<?xml version="1.0"encoding="utf-8"?> <!-- This template is for creating an Internet Draft using xml2rfc, which is available here: http://xml.resource.org. -->encoding="UTF-8"?> <!DOCTYPE rfcSYSTEM "rfc2629.dtd"[<!-- One method to get references from the online citation libraries. There has to be one entity for each item to be referenced. An alternate method (rfc include) is described in the references. --><!ENTITYRFC2119 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.2119.xml">nbsp " "> <!ENTITY zwsp "​"> <!ENTITYRFC2629 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.2629.xml">nbhy "‑"> <!ENTITYRFC5378 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.5378.xml">wj "⁠"> ]><?xml-stylesheet type='text/xsl' href='rfc2629.xslt' ?> <!-- used by XSLT processors --> <!-- For a complete list and description of processing instructions (PIs), please see http://xml.resource.org/authoring/README.html. --> <!-- Below are generally applicable Processing Instructions (PIs) that most I-Ds might want to use. (Here they are set differently than their defaults in xml2rfc v1.32) --> <!--<?rfc strict="yes" ?>--> <!-- give errors regarding ID-nits and DTD validation --> <!-- control the table of contents (ToC) --> <?rfc toc="yes"?> <!-- generate a ToC --> <?rfc tocdepth="4"?> <!-- the number of levels of subsections in ToC. default: 3 --> <!-- control references --> <?rfc symrefs="no"?> <!-- use symbolic references tags, i.e, [RFC2119] instead of [1] --> <?rfc sortrefs="yes" ?> <!-- sort the reference entries alphabetically --> <!-- control vertical white space (using these PIs as follows is recommended by the RFC Editor) --> <?rfc compact="yes" ?> <!-- do not start each main section on a new page --> <?rfc subcompact="no" ?> <!-- keep one blank line between list items --> <!-- end of list of popular I-D processing instructions --><rfc xmlns:xi="http://www.w3.org/2001/XInclude" submissionType="IRTF" category="exp"docName="draft-irtf-icnrg-ccninfo-13" ipr="trust200902">consensus="true" docName="draft-irtf-icnrg-ccninfo-15" number="9344" ipr="trust200902" obsoletes="" updates="" xml:lang="en" tocInclude="true" tocDepth="4" symRefs="true" sortRefs="true" version="3"> <!--category values: std, bcp, info, exp, and historic ipr values: full3667, noModification3667, noDerivatives3667 you can add the attributes updates="NNNN" and obsoletes="NNNN" they will automatically be output with "(if approved)"xml2rfc v2v3 conversion 3.15.0 --> <!-- ***** FRONT MATTER ***** --> <front> <title abbrev="CCNinfo"> CCNinfo: Discovering Content and Network Information in Content-Centric Networks </title><!-- add 'role="editor"' below for the editors if appropriate --> <!-- Another author who claims to be an editor --><seriesInfo name="RFC" value="9344"/> <author initials="H" surname="Asaeda" fullname="Hitoshi Asaeda"> <organization abbrev="NICT">National Institute of Information and Communications Technology</organization> <address> <postal><code>184-8795</code><street>4-2-1 Nukui-Kitamachi, Koganei</street><code>Tokyo 184-8795</code><code>184-8795</code> <region>Tokyo</region> <country>Japan</country> </postal> <email>asaeda@nict.go.jp</email> </address> </author> <author initials="A" surname="Ooka" fullname="Atsushi Ooka"> <organization abbrev="NICT">National Institute of Information and Communications Technology</organization> <address> <postal> <street>4-2-1 Nukui-Kitamachi, Koganei</street><code>Tokyo 184-8795</code><code>184-8795</code> <region>Tokyo</region> <country>Japan</country> </postal> <email>a-ooka@nict.go.jp</email> </address> </author> <author initials="X" surname="Shao" fullname="Xun Shao"> <organization>Toyohashi University of Technology</organization> <address> <postal> <street>1-1 Hibarigaoka Tempaku-cho, Toyohashi</street><code>Aichi 441-8580</code><region>Aichi</region> <code>441-8580</code> <country>Japan</country> </postal> <email>shao.xun.ls@tut.jp</email> </address> </author> <dateyear="2022"/>year="2023" month="February" /> <!-- Meta-data Declarations --><area>IRTF</area> <workgroup>ICN Research Group</workgroup><workgroup>Information-Centric Networking</workgroup> <keyword>ICN</keyword> <keyword>CCNx</keyword> <keyword>NDN</keyword> <keyword>CCNinfo</keyword> <abstract> <t> This document describes a mechanism named "CCNinfo" that discovers information about the network topology and in-network cache in Content-Centric Networks(CCN).(CCNs). CCNinfoinvestigates:investigates 1) the CCN routing path information per name prefix, 2) the Round-Trip Time (RTT) between the content forwarder and the consumer, and 3) the states of in-network cache per name prefix. CCNinfo is useful to understand and debug the behavior of testbed networks and other experimental deployments of CCN systems.</t> <t> This document is a product of the IRTF Information-Centric Networking Research Group (ICNRG). This document represents the consensus view of ICNRG and has been reviewed extensively by several members of the ICN community and the RG. The authors and RG chairs approve of the contents. The document is sponsored under theIRTF andIRTF, is not issued by theIETFIETF, and is not an IETF standard. This is an experimental protocol and the specification may change in the future.</t> </abstract> </front> <middle> <!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% --> <section anchor="sec.intro"title="Introduction">numbered="true" toc="default"> <name>Introduction</name> <t>In Content-Centric Networks(CCN),(CCNs), publishers provide the content through the network, and receivers retrieve it by name. In this network architecture, routers forward content requests through their Forwarding Information Bases (FIBs), which are populated by name-based routing protocols. CCN also enables receivers to retrieve content from an in-network cache.</t> <t>In CCN, while consumers do not generally need to know the content forwarder that is transmitting the content to them, the operators and developers may want to identify the content forwarder and observe the routing path information per name prefix for troubleshooting or investigating the network conditions.</t> <t>IP traceroute<!-- <xref target="refs.traceroute"/>-->is a useful tool for discovering the routing conditions in IP networks because it provides intermediate router addresses along the path between the source anddestinationthe destination, and the Round-Trip Time (RTT) for the path. However, this IP-based network tool cannot trace the name prefix paths used in CCN. Moreover, such IP-based network tools do not obtain the states of the in-network cache to be discovered.</t> <t>Contrace <xreftarget="refs.commag" />target="Contrace" format="default"/> enables end users (i.e., consumers) to investigate path and in-network cache conditions in CCN. Contrace is implemented as an external daemon process running over TCP/IP that can interact with a previous CCNx forwarding daemon (CCNx-0.8.2) to retrieve the caching information on the forwarding daemon. This solution is flexible, but it requires defining the common APIs used for global deployment in TCP/IP networks. ICN (Information-Centric Networking) ping <xreftarget="refs.icnping" />target="I-D.irtf-icnrg-icnping" format="default"/> and traceroute <xreftarget="refs.icntrace" />target="I-D.irtf-icnrg-icntraceroute" format="default"/> are lightweight operational tools that enable a user to explore the path(s) that reach a publisher or a cache storing the named content. ICN ping and traceroute, however, do not expose detailed information about the forwarders deployed by a network operator.</t> <t>This document describes the specifications of "CCNinfo", an active networking tool for discovering the path andcontent cachingcontent-caching information in CCN. CCNinfo defines the protocol messages to investigate path and in-network cache conditions in CCN. It is embedded in the CCNx forwarding process and can facilitate with non-IP networks as with the basic CCN concept.</t> <t>The two message types, Request and Reply messages, are encoded in the CCNx TLV format <xreftarget="refs.ccnx"/>.target="RFC8609" format="default"/>. Therequest-replyRequest-and-Reply message flow, walking up the tree from a consumer toward a publisher, is similar to the behavior of the IP multicast traceroute facility <xreftarget="refs.mtrace2" />.</t>target="RFC8487" format="default"/>.</t> <t>CCNinfo facilitates the tracing of a routing path andprovides:provides 1) the RTT between the content forwarder (i.e., caching router or first-hop router) and consumer, 2) the states of the in-network cache per name prefix, and 3) the routing path information per name prefix.</t> <t>In addition, CCNinfo identifies the states of the cache, such as thefollowingmetrics for Content Store (CS) in the contentforwarder:forwarder as follows: 1) size of cachedcontent objects,Content Objects, 2) number of cachedcontent objects,Content Objects, 3) number of accesses (i.e., received Interests) per content, and 4) elapsed cache time and remaining cache lifetime of content.</t> <t>CCNinfo supports multipath forwarding. The Request messages can be forwarded to multiple neighbor routers. When the Request messages are forwarded to multiple routers, the different Reply messages are forwarded from different routers or publishers.</t> <t>Furthermore, CCNinfo implements policy-based information provisioning that enables administrators to "hide" secure or private information but does not disrupt message forwarding. This policy-based information provisioning reduces the deployment barrier faced by operators in installing and running CCNinfo on their routers.</t> <t>The document represents the consensus of the Information-Centric Networking Research Group (ICNRG). This document was read and reviewed by the active research group members. It is not an IETF product and is not a standard.</t> <section anchor="sec.intro.exp"title="CCNinfonumbered="true" toc="default"> <name>CCNinfo as an ExperimentalTool">Tool</name> <t>In order to carry out meaningful experimentation with CCNx protocols, comprehensive instrumentation and management information is needed to take measurements and explore both the performance and robustness characteristics of the protocols and of the applications using them. CCNinfo's primary goal is to gather and report this information. As experience is gained with both the CCNx protocols and CCNinfo itself, we can refine the instrumentation capabilities and discover what additional capabilities might be needed in CCNinfo and conversely which features wind up not being of sufficient value to justify the implementation complexity and execution overhead.</t> <t>CCNinfo is intended as a comprehensive experimental tool for CCNx-based networks. It provides a wealth of information from forwarders, including on-path in-network cache conditions as well as forwarding path instrumentation of multiple paths toward content forwarders. As an experimental capability that exposes detailed information about the forwarders deployed by a network operator, CCNinfo employs more granular authorization policies than those required of ICN ping or ICN traceroute.</t> <t>CCNinfo uses two message types: Request and Reply. A CCNinfo user, e.g., consumer, initiates a CCNinfo Request message whens/he wantsthey want to obtain routing path and cache information. When an adjacent neighbor router receives the Request message, it examines its own cache information. If the router does not cache the specified content, it inserts its Report block into the hop-by-hop header of the Request message and forwards the message to its upstream neighbor router(s) decided by its FIB. In <xreftarget="fig:request" />,target="fig_request" format="default"/>, CCNinfo user and routers(Router(Routers A, B, C) insert their own Report blocks into the Request message and forward the message toward the content forwarder.</t> <figureanchor="fig:request" title="Request message invokedanchor="fig_request"> <name>Request Message Invoked by the CCNinfouserUser andforwardedForwarded byrouters.">Routers</name> <artworkalign="center">align="center" name="" type="" alt=""><![CDATA[ 1. Request 2. Request 3. Request (U) (U+A) (U+A+B) +----+ +----+ +----+ | | | | | | | v | v | v +--------+ +--------+ +--------+ +--------+ +---------+ | CCNinfo|----| Router |----| Router |----| Router |----|Publisher| | user | | A | | B | | C | | | +--------+ +--------+ +--------+ +--------+ +---------+ \ \ +-------+ 3. Request \ | Cache | (U+A+B) \ +---------+ | v| Caching |----+ | router | +---------+</artwork>]]></artwork> </figure> <t>When the Request message reaches the content forwarder, the content forwarder forms the Reply message; it inserts its own Reply block TLV and Reply sub-block TLV(s) to the Request message. The Reply message is then forwarded back toward the user in a hop-by-hop manner along the Pending Interest Table (PIT) entries. In <xreftarget="fig:reply" />,target="fig_reply" format="default"/>, each router(Router(Routers C, B, and A) forwards the Reply message along its PITentryentry, and finally, the CCNinfo user receives a Reply message from Router C, which is the first-hop router for thePublisher.publisher. Another Reply message from theCachingcaching router (i.e., Reply(C)) is discarded at Router B if the other Reply message (i.e., Reply(P)) was already forwarded by Router B.</t> <figureanchor="fig:reply" title="Reply messages forwardedanchor="fig_reply"> <name>Reply Messages Forwarded byrouters,Routers, andoneOne ReplymessageMessage isreceivedReceived by the CCNinfouser.">User</name> <artworkalign="center">align="center" name="" type="" alt=""><![CDATA[ 3. Reply(P) 2. Reply(P) 1. Reply(P) +----+ +----+ +----+ | | | | | | v | v | v | +--------+ +--------+ +--------+ +--------+ +---------+ | CCNinfo|----| Router |----| Router |----| Router |----|Publisher| | user | | A | | B | | C | | | +--------+ +--------+ +--------+ +--------+ +---------+ ^ \ +-------+ 1. Reply(C) \ | Cache | \ +---------+ | \| Caching |----+ | router | +---------+</artwork>]]></artwork> </figure> </section> </section> <!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% --> <sectiontitle="Terminology"> <t>Thenumbered="true" toc="default"> <name>Terminology</name> <t> The key words"MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY","<bcp14>MUST</bcp14>", "<bcp14>MUST NOT</bcp14>", "<bcp14>REQUIRED</bcp14>", "<bcp14>SHALL</bcp14>", "<bcp14>SHALL NOT</bcp14>", "<bcp14>SHOULD</bcp14>", "<bcp14>SHOULD NOT</bcp14>", "<bcp14>RECOMMENDED</bcp14>", "<bcp14>NOT RECOMMENDED</bcp14>", "<bcp14>MAY</bcp14>", and"OPTIONAL""<bcp14>OPTIONAL</bcp14>" in this document are to be interpreted as described inBCP 14 (<xref target="refs.RFC2119">RFC2119</xref> andBCP 14 <xref target="RFC2119"/> <xreftarget="refs.RFC8174">RFC8174</xref>)target="RFC8174"/> when, and only when, they appear in all capitals, as shownhere.</t>here. </t> <sectiontitle="Definitions">numbered="true" toc="default"> <name>Definitions</name> <t>This document follows the basic terminologies and definitions described in <xreftarget="refs.ccnx"/>.target="RFC8609" format="default"/>. Although CCNinfo requests flow in the opposite direction to the data flow, we refer to "upstream" and "downstream" with respect to data, unless explicitly specified.</t><t> <list style="hanging"> <t hangText="Scheme name"> <vspace blankLines="0"/> It<dl newline="true" spacing="normal"> <dt>Scheme name:</dt> <dd> A scheme name indicates a URI and protocol. This document only considers "ccnx:/" as the scheme name.</t> <t hangText="Prefix name"> <vspace blankLines="0"/></dd> <dt>Prefix name:</dt> <dd> A prefix name, which is defined in <xreftarget="refs.semantics" />,target="RFC8569" format="default"/>, is a name that does not uniquely identify a singlecontent object,Content Object, but rather a namespace or prefix of an existingcontent objectContent Object name.</t> <t hangText="Exact name"> <vspace blankLines="0"/></dd> <dt>Exact name:</dt> <dd> An exact name, which is defined in <xreftarget="refs.semantics" />,target="RFC8569" format="default"/>, is one that uniquely identifies the name of acontent object. </t> <t hangText="Node"> <vspace blankLines="0"/>Content Object. </dd> <dt>Node:</dt> <dd> A node within a CCN network can fulfill the role of a data publisher, a data consumer, and/or a forwarder forinterestInterest andcontent objectContent Object, asgivendescribed in <xreftarget="refs.term" />. </t> <t hangText="Consumer"> <vspace blankLines="0"/>target="RFC8793" format="default"/>. </dd> <dt>Consumer:</dt> <dd> A node that requestscontent objectsContent Objects by generating and sending outinterests.Interests. It isathe same definition of ICNConsumerConsumer, as given in <xreftarget="refs.term" />. </t> <t hangText="Publisher"> <vspace blankLines="0"/>target="RFC8793" format="default"/>. </dd> <dt>Publisher:</dt> <dd> A node that createscontent objectsContent Objects and makes them available for retrieval. It isathe same definition of ICNProducerProducer, as given in <xreftarget="refs.term" />. </t> <t hangText="Router"> <vspace blankLines="0"/>target="RFC8793" format="default"/>. </dd> <dt>Router:</dt> <dd> A node that implements stateful forwarding in the path between consumer and publisher.</t> <t hangText="Caching router"> <vspace blankLines="0"/></dd> <dt>Caching router:</dt> <dd> A node that temporarily stores and potentially carriesinterestsInterests orcontent objectsContent Objects before forwarding it to the next node.</t> <t hangText="Content forwarder"> <vspace blankLines="0"/> It</dd> <dt>Content forwarder:</dt> <dd> A content forwarder is either a caching router or a first-hop router that forwardscontent objectsContent Objects to consumers.</t> <t hangText="CCNinfo user"> <vspace blankLines="0"/></dd> <dt>CCNinfo user:</dt> <dd> A node that initiates the CCNinfo Request, which is either a consumer or a router that invokes the CCNinfo user program with the name prefix of the content. The CCNinfo user program, such as "ccninfo" command described in <xref target="sec.command"/>format="default"/> or other similar commands, initiates the Request message to obtain routing path and cache information.</t> <t hangText="Incoming face"> <vspace blankLines="0"/></dd> <dt>Incoming face:</dt> <dd> The face on which data are expected to arrive from the specified name prefix.</t> <t hangText="Outgoing face"> <vspace blankLines="0"/></dd> <dt>Outgoing face:</dt> <dd> The face to which data from the publisher or router are expected to transmit for the specified name prefix. It is also the face on which the Request messagesareis received.</t> <t hangText="Upstream router"> <vspace blankLines="0"/></dd> <dt>Upstream router:</dt> <dd> The router that connects to an Incoming face of a router.</t> <t hangText="Downstream router"> <vspace blankLines="0"/></dd> <dt>Downstream router:</dt> <dd> The router that connects to an Outgoing face of a router.</t> <t hangText="First-hop</dd> <dt>First-hop router(FHR)"> <vspace blankLines="0"/>(FHR):</dt> <dd> The router that matches a FIB entry with an Outgoing face referring to a local application or a publisher.</t> <t hangText="Last-hop</dd> <dt>Last-hop router(LHR)"> <vspace blankLines="0"/>(LHR):</dt> <dd> The router that is directly connected to a consumer.</t> </list> </t></dd> </dl> </section> </section> <!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% --> <sectiontitle="CCNinfonumbered="true" toc="default"> <name>CCNinfo MessageFormats">Formats</name> <t>CCNinfo Request and Reply messages are encoded in the CCNx TLV format(<xref target="refs.ccnx"/>,(see <xref target="RFC8609" format="default"/> and <xref target="CCNx_Hdr"/>).format="default"/>). The Request message consists of a fixed header, Request block TLV (<xref target="Req_block"/>),format="default"/>), and Report block TLV(s) (<xref target="Rpt_block"/>).format="default"/>). The Reply message consists of a fixed header, Request block TLV, Report block TLV(s), Reply block TLV (<xref target="Reply_block"/>),format="default"/>), and Reply sub-block TLV(s) (<xref target="Reply_subblock"/>).</t>format="default"/>).</t> <figureanchor="CCNx_Hdr" title="Packet format [1]">anchor="CCNx_Hdr"> <name>Packet Format <xref target="RFC8609" format="default"/></name> <artworkalign="center">align="center" name="" type="" alt=""><![CDATA[ 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +---------------+---------------+---------------+---------------+ | Version | PacketType | PacketLength | +---------------+---------------+---------------+---------------+ | PacketType specific fields | HeaderLength | +---------------+---------------+---------------+---------------+ / Optional Hop-by-hop header TLVs / +---------------+---------------+---------------+---------------+ / PacketPayload TLVs / +---------------+---------------+---------------+---------------+ / Optional CCNx ValidationAlgorithm TLV / +---------------+---------------+---------------+---------------+ / Optional CCNx ValidationPayload TLV (ValidationAlg required) / +---------------+---------------+---------------+---------------+</artwork>]]></artwork> </figure> <t>The PacketType values in the fixed header shown in <xref target="CCNx_Hdr"/>format="default"/> are PT_CCNINFO_REQUEST andPT_CCNINFO_REPLY, respectively (<xrefPT_CCNINFO_REPLY (see <xref target="Type_val"/>).format="default"/>). CCNinfo Request and Reply messages are forwarded in a hop-by-hop manner. When the Request message reaches the content forwarder, the content forwarder turns it into a Reply message by changing the Type field value in the fixed header from PT_CCNINFO_REQUEST to PT_CCNINFO_REPLY and forwards it back toward the node that initiated the Request message.</t><figure anchor='Type_val' title="Packet Type Namespace"> <artwork align="center"> Code Type name ======== ===================== %x00 PT_INTEREST [1] %x01 PT_CONTENT [1] %x02 PT_RETURN [1] %x03 PT_CCNINFO_REQUEST %x04 PT_CCNINFO_REPLY </artwork> </figure><table anchor="Type_val"> <name>CCNx Packet Types</name> <thead> <tr> <th>Type</th> <th>Name</th> </tr> </thead> <tbody> <tr> <td>0x00</td> <td>PT_INTEREST <xref target="RFC8609" format="default"/></td> </tr> <tr> <td>0x01</td> <td>PT_CONTENT <xref target="RFC8609" format="default"/></td> </tr> <tr> <td>0x02</td> <td>PT_RETURN <xref target="RFC8609" format="default"/></td> </tr> <tr> <td>0x03</td> <td>PT_CCNINFO_REQUEST</td> </tr> <tr> <td>0x04</td> <td>PT_CCNINFO_REPLY</td> </tr> </tbody> </table> <t>Following a fixed header, there can be a sequence of optional hop-by-hop header TLV(s) for a Request message. In the case of a Request message, it is followed by a sequence of Report blocks, each from a router on the path toward the publisher or caching router.</t> <t>At the beginning of PacketPayload TLVs, a top-level TLV type, T_DISCOVERY (<xref target="Top-level_Type"/>),format="default"/>), exists at the outermost level of a CCNx protocol message. This TLV indicates that the Name segment TLV(s) and Reply block TLV(s) would follow in the Request or Reply message.</t><figure anchor='Top-level_Type' title="Top-Level Type Namespace"> <artwork align="center"> Code Type name ============= ========================= %x0000 Reserved [1] %x0001 T_INTEREST [1] %x0002 T_OBJECT [1] %x0003 T_VALIDATION_ALG [1] %x0004 T_VALIDATION_PAYLOAD [1] %x0005 T_DISCOVERY </artwork> </figure> <!-- XXX The reasons to distinguish or separate PT values; o. distinguish normal interest/data forwarding; e.g., no cache, force multipath discovery, o. easy to filter out invalid ccninfo request or set different access control policy --> <!-- XXX Why we define the new type value, T_TRACE, and don't use T_INTEREST and T_OBJECT icnping and icntrace do? Because it is good to distingush regular Interest/CoB transmission and CCNinfo. CCNinfo requires (1) no cache for reply messages, (2) different PIT operations especially required for multipath support. For (1), it is possible to do it by setting "cache lifetime = 0", but . And in any case, PT_xxx must be --><table anchor="Top-level_Type"> <name>CCNx Top-Level Types</name> <thead> <tr> <th>Type</th> <th>Name</th> </tr> </thead> <tbody> <tr> <td>0x0000</td> <td>Reserved <xref target="RFC8609" format="default"/></td> </tr> <tr> <td>0x0001</td> <td>T_INTEREST <xref target="RFC8609" format="default"/></td> </tr> <tr> <td>0x0002</td> <td>T_OBJECT <xref target="RFC8609" format="default"/></td> </tr> <tr> <td>0x0003</td> <td>T_VALIDATION_ALG <xref target="RFC8609" format="default"/></td> </tr> <tr> <td>0x0004</td> <td>T_VALIDATION_PAYLOAD <xref target="RFC8609" format="default"/></td> </tr> <tr> <td>0x0005</td> <td>T_DISCOVERY</td> </tr> </tbody> </table> <!-- ========================================================== --> <section anchor="sec.request"title="Request Message">numbered="true" toc="default"> <name>Request Message</name> <t>When a CCNinfo user initiates a discovery request (e.g., via the ccninfo command described in <xref target="sec.command"/>),format="default"/>), a CCNinfo Request message is created and forwarded to its upstream router through the Incoming face(s) determined by its FIB.</t> <t>The Request message format is shown in <xref target="Req_message"/>.format="default"/>. It consists of a fixed header, Request header block TLV (<xref target="Req_block"/>),format="default"/>), Report block TLV(s) (<xref target="Rpt_block"/>),format="default"/>), Name TLV, and Request block TLV. Request header block TLV and Report block TLV(s) are contained in the hop-by-hop header, as those might change from hop to hop. Request block TLV is encoded in the PacketPayload TLV by content forwarder as the protocol message itself. The PacketType value of the Request message is PT_CCNINFO_REQUEST (<xref target="Type_val"/>).format="default"/>). The Type value of the CCNx Top-Level typenamespaceis T_DISCOVERY (<xref target="Top-level_Type"/>).</t>format="default"/>).</t> <figureanchor="Req_message" title="Request message consists of a fixed header, Request block TLV, Report block TLV(s), and Name TLV">anchor="Req_message"> <name>Request Message</name> <artworkalign="center">align="center" name="" type="" alt=""><![CDATA[ 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +---------------+---------------+---------------+---------------+ | Version | PacketType | PacketLength | +---------------+---------------+---------------+---------------+ | HopLimit | ReturnCode | Reserved(MBZ) | HeaderLength | +===============+===============+===============+===============+ / Request header block TLV / +---------------+---------------+---------------+---------------+ / Report block TLV 1 / +---------------+---------------+---------------+---------------+ / Report block TLV 2 / +---------------+---------------+---------------+---------------+ / . / / . / +---------------+---------------+---------------+---------------+ / Report block TLV n / +===============+===============+===============+===============+ | Type (=T_DISCOVERY) | MessageLength | +---------------+---------------+---------------+---------------+ | T_NAME | Length | +---------------+---------------+---------------+---------------+ / Name segment TLVs (name prefix specified by CCNinfo user) / +---------------+---------------+---------------+---------------+ / Request block TLV / +---------------+---------------+---------------+---------------+ / Optional CCNx ValidationAlgorithm TLV / +---------------+---------------+---------------+---------------+ / Optional CCNx ValidationPayload TLV (ValidationAlg required) / +---------------+---------------+---------------+---------------+</artwork>]]></artwork> </figure><t>HopLimit: 8 bits <list><dl> <dt>HopLimit:</dt> <dd><t>8 bits</t> <t>HopLimit is a counter that is decremented with each hop whenever a Request packet is forwarded. It is specified by the CCNinfo user program. The HopLimit valueMUST<bcp14>MUST</bcp14> be decremented by 1 prior to forwarding the Request packet. The packet is discarded if HopLimit is decremented to zero. HopLimit limits the distance that a Request may travel on the network. Only the specified number of hops from the CCNinfo user traces the Request. The last router stops the trace and sends the Reply message back to the CCNinfouser.</t> </list> </t> <t>ReturnCode: 8 bits <list>user.</t></dd> <dt>ReturnCode:</dt> <dd><t>8 bits</t> <t>ReturnCode is used for the Reply message. This value is replaced by the content forwarder when the Request message is returned as the Reply message (see <xref target="sec.reply"/>).format="default"/>). Until then, this fieldMUST<bcp14>MUST</bcp14> be transmitted as zeros and ignored on receipt.</t></list> </t> <figure> <artwork align="center"> Value Name Description ----- --------------- ---------------------------------------------- %x00 NO_ERROR No error %x01 WRONG_IF CCNinfo<table> <name>ReturnCode Used for the Reply Message</name> <thead> <tr> <th>Value</th> <th>Name</th> <th>Description</th> </tr> </thead> <tbody> <tr> <td>0x00</td> <td>NO_ERROR</td> <td>No error</td> </tr> <tr> <td>0x01</td> <td>WRONG_IF</td> <td>CCNinfo Request arrived on an interface to which this router would not forward for the specifiedname/functionname and/or function toward thepublisher. %x02 INVALID_REQUEST Invalidpublisher.</td> </tr> <tr> <td>0x02</td> <td>INVALID_REQUEST</td><td>Invalid CCNinfo Request isreceived. %x03 NO_ROUTE Thisreceived.</td> </tr> <tr> <td>0x03</td> <td>NO_ROUTE </td> <td>This router has no route for the name prefix and no way to determine aroute. %x04 NO_INFO Thisroute.</td> </tr> <tr> <td>0x04</td> <td>NO_INFO</td> <td>This router has no cache information for the specified nameprefix. %x05 NO_SPACE Thereprefix.</td> </tr> <tr> <td>0x05</td> <td>NO_SPACE</td> <td>There was not enough room to insert another Report block in thepacket. %x06 INFO_HIDDEN Informationpacket.</td> </tr> <tr> <td>0x06</td> <td>INFO_HIDDEN</td><td>Information is hidden from this discovery owing to somepolicy. %x0E ADMIN_PROHIB CCNinfopolicy.</td> </tr> <tr> <td>0x0E</td> <td>ADMIN_PROHIB</td> <td>CCNinfo Request is administrativelyprohibited. %x0F UNKNOWN_REQUEST Thisprohibited.</td> </tr> <tr> <td>0x0F</td> <td>UNKNOWN_REQUEST</td> <td>This router does notsupport/recognizesupport or recognize the Requestmessage. %x80 FATAL_ERROR Inmessage.</td> </tr> <tr> <td>0x80</td> <td>FATAL_ERROR</td> <td>In a fatal error, the router may know the upstream router but cannot forward the message toit. </artwork> <!--0x06 NO_GATEWAY CCNinfo Request arrived on a non-gateway router.--> <!--0x82 TOO_MANY_BLOCKS There was too many Report blocks in the packet.--> <!-- <postamble> The 0x80 bit of the ReturnCode is used to indicate a fatal error. A fatal error is one where the router cannot forward the message to the upstream router. </postamble>--> </figure> <t>Reserved (MBZ): 8 bits <list>it.</td> </tr> </tbody> </table> </dd> <dt>Reserved (MBZ):</dt> <dd><t>8 bits</t> <t>The reserved fields in the Value fieldMUST<bcp14>MUST</bcp14> be transmitted as zeros and ignored onreceipt.</t> </list> </t>receipt.</t></dd> </dl> <!-- ======================================================== --> <section anchor="sec.request_blk"title="Requestnumbered="true" toc="default"> <name>Request Header Block and RequestBlock">Block</name> <t>When a CCNinfo user transmits the Request message,s/he MUSTthey <bcp14>MUST</bcp14> inserther/histheir Request header block TLV (<xref target="Req_block"/>)format="default"/>) into the hop-by-hop header and Request block TLV (<xref target="Req_nodeblock"/>)format="default"/>) into the message before sending it through the Incoming face(s).</t> <figureanchor='Req_block' title="Request header blockanchor="Req_block"> <name>Request Header Block TLV(hop-by-hop header)">(Hop-by-Hop Header)</name> <artworkalign="center">align="center" name="" type="" alt=""><![CDATA[ 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +---------------+---------------+---------------+---------------+ | Type (=T_DISC_REQHDR) | Length | +---------------+---------------+-------+-------+-------+-+-+-+-+ | Request ID |SkipHop| Flags |V|F|O|C| +---------------+---------------+-------+-------+-------+-+-+-+-+</artwork> </figure> <figure anchor='Hop-by-hop_Type' title="Hop-by-Hop Type Namespace"> <artwork align="center"> Code Type name ============= ========================= %x0000 Reserved [1] %x0001 T_INTLIFE [1] %x0002 T_CACHETIME [1] %x0003 T_MSGHASH [1] %x0004-%x0007 Reserved [1] %x0008 T_DISC_REQHDR %x0009 T_DISC_REPORT %x0FFE T_PAD [1] %x0FFF T_ORG [1] %x1000-%x1FFF Reserved [1] </artwork>]]></artwork> </figure><t>Type: 16 bits <list><table anchor="Hop-by-hop_Type"> <name>CCNx Hop-by-Hop Types</name> <thead> <tr> <th>Type</th> <th>Name</th> </tr> </thead> <tbody> <tr> <td>0x0000</td> <td>Reserved <xref target="RFC8609" format="default"/></td> </tr><tr> <td>0x0001</td> <td>T_INTLIFE <xref target="RFC8609" format="default"/></td> </tr><tr> <td>0x0002</td> <td>T_CACHETIME <xref target="RFC8609" format="default"/></td> </tr><tr> <td>0x0003</td> <td>T_MSGHASH <xref target="RFC8609" format="default"/></td> </tr><tr> <td>0x0004-0x0007</td> <td>Reserved <xref target="RFC8609" format="default"/></td> </tr><tr> <td>0x0008</td> <td>T_DISC_REQHDR</td> </tr><tr> <td>0x0009</td> <td>T_DISC_REPORT</td> </tr><tr> <td>0x0FFE</td> <td>T_PAD <xref target="RFC8609" format="default"/></td> </tr><tr> <td>0x0FFF</td> <td>T_ORG <xref target="RFC8609" format="default"/></td> </tr><tr> <td>0x1000-0x1FFF</td> <td>Reserved <xref target="RFC8609" format="default"/></td> </tr> </tbody> </table> <dl> <dt>Type:</dt> <dd><t>16 bits</t> <t>Format of the Value field.For theThe type value of the Request header block TLVMUST<bcp14>MUST</bcp14> beT_DISC_REQHDR.</t> </list> </t> <t>Length: 16 bits <list>T_DISC_REQHDR.</t></dd> <dt>Length:</dt> <dd><t>16 bits</t> <t>Length of the Value field inoctets. <!-- XXX removed because of no detail discussion about this XXX Minimum length required is 4 octets (i.e., no Value field). The maximum TLV length is not defined; however the entire CCNinfo packet length should not exceed the available MTU.--> </t> </list> </t> <t>Request ID: 16 bits <list>octets.</t></dd> <dt>Request ID:</dt> <dd><t>16 bits</t> <t>This field is used as a unique identifier for the CCNinfo Request so that the duplicate or delayed Reply messages can bedetected.</t> </list> </t> <t>SkipHopdetected.</t></dd> <dt>SkipHop (Skip HopCount): 4 bits <list>Count):</dt> <dd><t>4 bits</t> <t>Number of skipped routers for a Request. It is specified by the CCNinfo user program. The number of routers corresponding to the value specified in this field areskippedskipped, and the CCNinfo Request messages are forwarded to the next router without the addition of Report blocks; the next upstream router then starts the trace. The maximum value of this parameter is 15. This valueMUST<bcp14>MUST</bcp14> be lower than that of HopLimit at the fixedheader.</t> </list> </t> <!-- <t>TimeO: 3 bits <list> <t>Timeout value (seconds). This Timeout value means a [CCNinfo Reply Timeout] value (seconds) requested by the CCNinfo user later described in <xref target="sec.timer" />. A CCNinfo user requests routers along the path to keep the PIT entry for the Request until this timeout value expires. Note that, because of some security concern (<xref target="sec.timeout" />), a router along the path may configure the shorter timeout value than this requested timeout value. In that case, the Request may be timed out and the user may not receive the Reply as expected.</t> </list> </t>--> <t>Flags: 12 bits <list>header.</t></dd> <dt>Flags:</dt> <dd><t>12 bits</t> <t>The Flags field is used to indicate the types of the content or path discoveries. Currently, as shown in <xref target="FlagVal"/>,format="default"/>, fourbits, "C",bits ("C", "O", "F", and"V""V") are assigned, and the other 8 bits are reserved (MBZ) for the future use. Each flag can be mutually specified with other flags. These flags are set by the CCNinfo user program when they initiate Requests (see <xref target="sec.command"/>),format="default"/>), and the routers that receive the Requests deal with the flags and change the behaviors (see <xref target="sec.router"/>format="default"/> for details). The Flag values defined in this Flags field correspond to the Reply sub-blocks.</t></list> </t> <figure anchor='FlagVal' title="Codes<table anchor="FlagVal"> <name>Codes andtypes specifiedTypes Specified in Flagsfield"> <artwork align="center"> Flag Value Description ----- ----- ----------------------------------------------------- C 0 PathField</name> <thead> <tr> <th>Flag</th> <th>Value</th> <th>Description</th> </tr> </thead> <tbody> <tr> <td>C</td> <td>0</td> <td>Path discovery (i.e., no cache information retrieved)(default) C 1 Path(default)</td> </tr><tr> <td>C</td> <td>1</td> <td>Path and cache informationretrieval O 0 Requestretrieval</td> </tr><tr> <td>O</td> <td>0</td> <td>Request to any content forwarder(default) O 1 Publisher(default)</td> </tr><tr> <td>O</td> <td>1</td> <td>Publisher discovery (i.e., only FHR canreply) F 0 Requestreply)</td> </tr><tr> <td>F</td> <td>0</td> <td>Request based on FIB's forwarding strategy(default) F 1 Full(default)</td> </tr><tr> <td>F</td> <td>1</td> <td>Full discovery request. Request to possible multiple upstream routers specified in FIBsimultaneously V 0 Nosimultaneously</td> </tr><tr> <td>V</td> <td>0</td><td>No reply validation(default) V 1 Reply(default)</td> </tr><tr> <td>V</td> <td>1</td> <td>Reply sender validates Replymessage </artwork> </figure>message</td> </tr> </tbody> </table> </dd></dl> <figureanchor='Req_nodeblock' title="Request blockanchor="Req_nodeblock"> <name>Request Block TLV(packet payload)">(Packet Payload)</name> <artworkalign="center">align="center" name="" type="" alt=""><![CDATA[ 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +---------------+---------------+---------------+---------------+ | Type (=T_DISC_REQ) | Length | +---------------+---------------+---------------+---------------+ | Request Arrival Time | +---------------+---------------+---------------+---------------+ / Node Identifier / +---------------+---------------+---------------+---------------+</artwork>]]></artwork> </figure><figure anchor='CCNx_Type' title="CCNx<table anchor="CCNx_Type"> <name>CCNx MessageType Namespace"> <artwork align="center"> Code Type name ============== =================== %x0000 T_NAME [1] %x0001 T_PAYLOAD [1] %x0002 T_KEYIDRESTR [1] %x0003 T_OBJHASHRESTR [1] %x0005 T_PAYLDTYPE [1] %x0006 T_EXPIRY [1] %x0007 T_DISC_REQ %x0008 T_DISC_REPLY %x0009-%x0012 Reserved [1] %x0FFE T_PAD [1] %x0FFF T_ORG [1] %x1000-%x1FFF Reserved [1] </artwork> </figure> <t>Type: 16 bits <list>Types</name> <thead> <tr> <th>Type</th> <th>Name</th> </tr> </thead> <tbody> <tr> <td>0x0000</td> <td>T_NAME <xref target="RFC8609" format="default"/></td> </tr><tr> <td>0x0001</td> <td>T_PAYLOAD <xref target="RFC8609" format="default"/></td> </tr><tr> <td>0x0002</td> <td>T_KEYIDRESTR <xref target="RFC8609" format="default"/></td> </tr><tr> <td>0x0003</td> <td>T_OBJHASHRESTR <xref target="RFC8609" format="default"/></td> </tr><tr> <td>0x0005</td> <td>T_PAYLDTYPE <xref target="RFC8609" format="default"/></td> </tr><tr> <td>0x0006</td> <td>T_EXPIRY <xref target="RFC8609" format="default"/></td> </tr><tr> <td>0x0007-0x000C</td> <td>Reserved <xref target="RFC8609" format="default"/></td> </tr><tr> <td>0x000D</td> <td>T_DISC_REQ</td> </tr><tr> <td>0x000E</td> <td>T_DISC_REPLY</td> </tr><tr> <td>0x0FFE</td> <td>T_PAD <xref target="RFC8609" format="default"/></td> </tr><tr> <td>0x0FFF</td> <td>T_ORG <xref target="RFC8609" format="default"/></td> </tr><tr> <td>0x1000-0x1FFF</td> <td>Reserved <xref target="RFC8609" format="default"/></td> </tr> </tbody> </table> <dl> <dt>Type:</dt> <dd><t>16 bits</t> <t>Format of the Value field. For the Request block TLV, the type value(s)MUST<bcp14>MUST</bcp14> be T_DISC_REQ (see <xref target="CCNx_Type"/>)format="default"/>) in the currentspecification.</t> </list> </t> <t>Length: 16 bits <list>specification.</t></dd> <dt>Length:</dt> <dd><t>16 bits</t> <t>Length of the Value field inoctets.</t> </list> </t> <dl newline="true" spacing="normal" indent="3">octets.</t></dd> <dt>Request ArrivalTime: 32 bits</dt> <dd> <!-- <vspace blankLines="1"/>--> </dd></dl> <dl newline="false" spacing="normal" indent="3"> <dt/> <dd> <t> TheTime:</dt> <dd><t>32 bits</t> <t>The Request Arrival Time is a 32-bit NTP timestamp specifying the arrival time of the CCNinfo Request message at the router. The 32-bit form of an NTP timestamp consists of the middle 32 bits of the full 64-bitform;form, that is, the low 16 bits of the integer part and the high 16 bits of the fractionalpart. </t>part.</t> <t>The following formula converts from a timespec (fractional part in nanoseconds) to a 32-bit NTP timestamp:</t></dd> </dl><artwork name="" type="" align="left" alt=""><![CDATA[ request_arrival_time = ((tv.tv_sec + 32384) << 16) + ((tv.tv_nsec << 7) / 1953125) ]]></artwork><dl newline="false" spacing="normal" indent="3"> <dt/> <dd><t> The constant 32384 is the number of seconds from Jan 1, 1900 to Jan 1, 1970 truncated to 16 bits. ((tv.tv_nsec << 7) / 1953125) is a reduction of ((tv.tv_nsec / 1000000000) << 16), where "<<" denotes a logical leftshift.</dd> </dl> <dl newline="false" spacing="normal" indent="3"> <dt/> <dd>shift.</t> <t> Note that it isRECOMMENDED<bcp14>RECOMMENDED</bcp14> for all the routers on the path to have synchronized clocks to measure one-way latency per hop; however, even if they do not have synchronized clocks, CCNinfo measures the RTT between the content forwarder andconsumer.</dd> </dl> <t>Node Identifier: variable length <list>the consumer.</t></dd> <dt>Node Identifier:</dt> <dd><t>variable length</t> <t>This field specifies the node identifier (e.g., node name or hash-based self-certifying name <xreftarget="refs.hopauth" />)target="DCAuth" format="default"/>) or all-zeros if unknown. This document assumes that the Name TLV defined in the CCNx TLV format <xreftarget="refs.ccnx" />target="RFC8609" format="default"/> can be used for this field and the node identifier is specified init.</t> </list> </t>it.</t></dd> </dl> </section> <!-- ======================================================== --> <section anchor="sec.report_blk"title="Reportnumbered="true" toc="default"> <name>Report BlockTLV">TLV</name> <t>A CCNinfo user and each upstream router along the path would insert their own Report block TLV without changing the Type field of the fixed header of the Request message until one of these routers is ready to send a Reply. In the Report block TLV (<xref target="Rpt_block"/>),format="default"/>), the Request Arrival Time and Node IdentifierMUSTvalues <bcp14>MUST</bcp14> be inserted.</t> <figureanchor='Rpt_block' title="Report blockanchor="Rpt_block"> <name>Report Block TLV(hop-by-hop header)">(Hop-by-Hop Header)</name> <artworkalign="center">align="center" name="" type="" alt=""><![CDATA[ 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +---------------+---------------+---------------+---------------+ | Type (=T_DISC_REPORT) | Length | +---------------+---------------+---------------+---------------+ | Request Arrival Time | +---------------+---------------+---------------+---------------+ / Node Identifier / +---------------+---------------+---------------+---------------+</artwork>]]></artwork> </figure><t>Type: 16 bits <list><dl> <dt>Type:</dt> <dd><t>16 bits</t> <t>Format of the Value field. For the Report block TLV, the type value(s)MUST<bcp14>MUST</bcp14> be T_DISC_REPORT in the current specification. For all the available typesforof the CCNx hop-by-hoptype namespace,types, please see <xreftarget="Hop-by-hop_Type"/>.</t> </list> </t> <t>Length: 16 bits <list>target="Hop-by-hop_Type" format="default"/>.</t></dd> <dt>Length:</dt> <dd><t>16 bits</t> <t>Length of the Value field inoctets.</t> </list> </t> <t>Requestoctets.</t></dd> <dt>Request ArrivalTime: 32 bits <list>Time:</dt> <dd><t>32 bits</t> <t>Same definition as given in <xref target="sec.request_blk"/>.</t> </list> </t> <t>Node Identifier: variable length <list>format="default"/>.</t></dd> <dt>Node Identifier:</dt> <dd><t>variable length</t> <t>Same definition as given in <xref target="sec.request_blk"/>.</t> </list> </t>format="default"/>.</t></dd> </dl> </section> <!-- Report Block --> <section anchor="sec.namespec"title="Contentnumbered="true" toc="default"> <name>Content NameSpecification">Specification</name> <t>Specifications of the Name TLV (whose type value is T_NAME) and the Name Segment TLVs are described in <xreftarget="refs.ccnx" />,target="RFC8609" format="default"/>, whichareis followed by CCNinfo. CCNinfo enablestothe specification of the content nameeitherwith either a prefix name without chunk number (such as "ccnx:/news/today") or an exact name (such as "ccnx:/news/today/Chunk=10"). When a CCNinfo user specifies a prefix name,s/hethey will obtain the summary information of the matchedcontent objectsContent Objects in the content forwarder. In contrast, when a CCNinfo user specifies an exact name,s/hethey will obtain information only about the specifiedcontent objectContent Object in the content forwarder. A CCNinfo Request messageMUST NOT<bcp14>MUST NOT</bcp14> be sent only with a scheme name, ccnx:/. It will be rejected and discarded by routers.</t> </section> <!-- Name --> </section> <!-- Request Message --> <!-- ========================================================== --> <section anchor="sec.reply"title="Reply Message">numbered="true" toc="default"> <name>Reply Message</name> <t>When a content forwarder receives a CCNinfo Request message from an appropriate adjacent neighbor router, it inserts its own Reply block TLV and Reply sub-block TLV(s) to the Request message and turns the Request into the Reply by changing the Type field of the fixed header of the Request message from PT_CCNINFO_REQUEST to PT_CCNINFO_REPLY. The Reply message (see <xref target="Reply_message"/>)format="default"/>) is then forwarded back toward the CCNinfo user in a hop-by-hop manner.</t> <figureanchor="Reply_message" title="Reply message consists of a fixed header, Request block TLV, Report block TLV(s), Name TLV, and Reply block/sub-block TLV(s)">anchor="Reply_message"> <name>Reply Message</name> <artworkalign="center">align="center" name="" type="" alt=""><![CDATA[ 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +---------------+---------------+---------------+---------------+ | Version | PacketType | PacketLength | +---------------+---------------+-------------+-+---------------+ | HopLimit | ReturnCode | Reserved(MBZ) | HeaderLength | +===============+===============+=============+=+===============+ / Request header block TLV / +---------------+---------------+---------------+---------------+ / . / / . / / n Report block TLVs / / . / / . / +===============+===============+===============+===============+ | Type (=T_DISCOVERY) | MessageLength | +---------------+---------------+---------------+---------------+ | T_NAME | Length | +---------------+---------------+---------------+---------------+ / Name segment TLVs (name prefix specified by CCNinfo user) / +---------------+---------------+---------------+---------------+ / Request block TLV / +---------------+---------------+---------------+---------------+ / Reply block TLV / +---------------+---------------+---------------+---------------+ / Reply sub-block TLV 1 / +---------------+---------------+---------------+---------------+ / . / / . / +---------------+---------------+---------------+---------------+ / Reply sub-block TLV k / +---------------+---------------+---------------+---------------+ / Optional CCNx ValidationAlgorithm TLV / +---------------+---------------+---------------+---------------+ / Optional CCNx ValidationPayload TLV (ValidationAlg required) / +---------------+---------------+---------------+---------------+</artwork>]]></artwork> </figure> <!-- ======================================================== --> <section anchor="sec.reply_blk"title="Replynumbered="true" toc="default"> <name>Reply BlockTLV">TLV</name> <t>The Reply block TLV is an envelope for the Reply sub-block TLV(s) (explainedfromin the next section).</t> <figureanchor="Reply_block" title="Reply blockanchor="Reply_block"> <name>Reply Block TLV(packet payload)">(Packet Payload)</name> <artworkalign="center">align="center" name="" type="" alt=""><![CDATA[ 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +---------------+---------------+---------------+---------------+ | Type (=T_DISC_REPLY) | Length | +---------------+---------------+---------------+---------------+ | Request Arrival Time | +---------------+---------------+---------------+---------------+ / Node Identifier / +---------------+---------------+---------------+---------------+</artwork>]]></artwork> </figure><t>Type: 16 bits <list><dl> <dt>Type:</dt> <dd><t>16 bits</t> <t>Format of the Value field. For the Reply block TLV, the type valueMUST<bcp14>MUST</bcp14> be T_DISC_REPLY shown in <xref target="CCNx_Type"/>format="default"/> in the currentspecification.</t> </list> </t> <t>Length: 16 bits <list>specification.</t></dd> <dt>Length:</dt> <dd><t>16 bits</t> <t>Length of the Value field in octets. This length is the total length of the Reply sub-block(s).</t></list> </t> <t>Request</dd> <dt>Request ArrivalTime: 32 bits <list>Time:</dt> <dd><t>32 bits</t> <t>Same definition as given in <xref target="sec.request_blk"/>.</t> </list> </t> <t>Node Identifier: variable length <list>format="default"/>.</t> </dd> <dt>Node Identifier:</dt> <dd><t>variable length</t> <t>Same definition as given in <xref target="sec.request_blk"/>.</t> </list> </t>format="default"/>.</t> </dd> </dl> <!-- ======================================================== --> <section anchor="sec.reply_subblk"title="Replynumbered="true" toc="default"> <name>Reply Sub-BlockTLV">TLV</name> <t>The router on the traced path will add one or multiple Reply sub-blocks followed by the Reply block TLV before sending the Reply to its neighbor router. This section describes the Reply sub-block TLV for informing various cache states and conditions as shown in <xref target="Reply_subblock"/>.format="default"/>. (Other Reply sub-block TLVs will be discussed in separate document(s).)</t> <t>Note that some routers may not be capable of reporting the followingvalues, such asvalues: Object Size, Object Count, # Received Interest, First Seqnum, Last Seqnum, Elapsed Cache Time, and Remain CacheLifetime, shownLifetime (shown in <xref target="Reply_subblock"/>, orformat="default"/>). Or, some routers do not report these values due to their policy. In that case, the routers <bcp14>MUST</bcp14> set these fields to a value of all ones (i.e.,%xFFFFFFFF).0xFFFFFFFF). The value of each fieldwill<bcp14>MUST</bcp14> be also all-one when the value is equal to or bigger than the maximum size expressed by the 32-bit field. The CCNinfo user programMUST<bcp14>MUST</bcp14> inform that these values are not valid if the fields received are set to the value of all ones.</t> <t>If the cache is refreshed after reboot, the value in each fieldMUST<bcp14>MUST</bcp14> be refreshed (i.e.,MUST<bcp14>MUST</bcp14> be set to 0). If the cache remains after reboot, the valueMUST NOT<bcp14>MUST NOT</bcp14> be refreshed (i.e.,MUST<bcp14>MUST</bcp14> be reflected as it is).</t> <figureanchor="Reply_subblock" title="Reply sub-blockanchor="Reply_subblock"> <name>Reply Sub-Block TLV for T_DISC_CONTENT and T_DISC_CONTENT_PUBLISHER(packet payload)">(Packet Payload)</name> <artworkalign="center">align="center" name="" type="" alt=""><![CDATA[ 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +---------------+---------------+---------------+---------------+ | Type | Length | +---------------+---------------+---------------+---------------+ | Object Size | +---------------+---------------+---------------+---------------+ | Object Count | +---------------+---------------+---------------+---------------+ | # Received Interest | +---------------+---------------+---------------+---------------+ | First Seqnum | +---------------+---------------+---------------+---------------+ | Last Seqnum | +---------------+---------------+---------------+---------------+ | Elapsed Cache Time | +---------------+---------------+---------------+---------------+ | Remain Cache Lifetime | +---------------+---------------+---------------+---------------+ | T_NAME | Length | +---------------+---------------+---------------+---------------+ / Name Segment TLVs / +---------------+---------------+---------------+---------------+</artwork> </figure> <figure anchor='Sub_Type' title="CCNinfo Reply Type Namespace"> <artwork align="center"> Code Type name ============= =========================== %x0000 T_DISC_CONTENT %x0001 T_DISC_CONTENT_PUBLISHER %x0FFF T_ORG %x1000-%x1FFF Reserved (Experimental Use) </artwork>]]></artwork> </figure><t>Type: 16 bits <list><table anchor="Sub_Type"> <name>CCNx Reply Types</name> <thead> <tr> <th>Type</th> <th>Name</th> </tr> </thead> <tbody> <tr> <td>0x0000</td> <td>T_DISC_CONTENT</td> </tr><tr> <td>0x0001</td> <td>T_DISC_CONTENT_PUBLISHER</td> </tr><tr> <td>0x0FFF</td> <td>T_ORG</td> </tr><tr> <td>0x1000-0x1FFF</td> <td>Reserved for Experimental Use</td> </tr> </tbody> </table> <dl> <dt>Type:</dt> <dd><t>16 bits</t> <t>Format of the Value field. For the Reply sub-block TLV, the type valueMUST<bcp14>MUST</bcp14> be either T_DISC_CONTENT or T_DISC_CONTENT_PUBLISHER defined in theCCNinfoCCNx ReplyType NamespaceTypes (<xref target="Sub_Type"/>).format="default"/>). T_DISC_CONTENT is specified when a content forwarder replies with the cacheinformation is replied from a caching router.information. T_DISC_CONTENT_PUBLISHER is specified whenthe content information is replied froma FHR attached to apublisher.</t> </list> </t> <t>Length: 16 bits <list>publisher replies with the original content information.</t></dd> <dt>Length:</dt> <dd><t>16 bits</t> <t>Length of the Value field in octets.</t></list> </t> <t>Object Size: 32 bits <list></dd> <dt>Object Size:</dt> <dd><t>32 bits</t> <t>The total size (KB) of the unexpiredcontent objects.Content Objects. Values less than 1 KB are truncated. Note that the maximum size expressed by the 32-bit field is approximately 4.29 TB. </t></list> </t> <t>Object Count: 32 bits <list></dd> <dt>Object Count:</dt> <dd><t>32 bits</t> <t>The number of the unexpiredcontent objects.Content Objects. Note that the maximum count expressed by the 32-bit field is approximately 4.29billion.</t> </list> </t> <t>#billion.</t></dd> <dt># ReceivedInterest: 32 bits <list> <!-- <t>The number of the received Interest messages to retrieve the content (not content objects).</t>-->Interest:</dt> <dd><t>32 bits</t> <t>The total number of the received Interest messages to retrieve the cachedcontent objects.</t> </list> </t> <t>First Seqnum: 32 bits <list>Content Objects.</t> </dd> <dt>First Seqnum:</dt> <dd><t>32 bits</t> <t>The first sequential number of the unexpiredcontent objects.</t> </list> </t> <t>Last Seqnum: 32 bits <list>Content Objects.</t> </dd> <dt>Last Seqnum:</dt> <dd><t>32 bits</t> <t>The last sequential number of the unexpiredcontent objects.Content Objects. The First Seqnum and Last Seqnum do not guarantee the consecutiveness of the cachedcontent objects;Content Objects; however, knowing these values may help in the analysis of consecutive or discontinuous chunks such as <xreftarget="refs.acur" />.</t> </list> </t> <t>Elapsedtarget="CONSEC-CACHING" format="default"/>.</t></dd> <dt>Elapsed CacheTime: 32 bits <list>Time:</dt> <dd><t>32 bits</t> <t>The elapsed time (seconds) after the oldestcontent objectContent Object of the content is cached.</t></list> </t> <!-- XXXXX cache life time is per content? or per content object? If the latter one, this is wrong. --> <t>Remain</dd> <dt>Remain CacheLifetime: 32 bits <list>Lifetime:</dt> <dd><t>32 bits</t> <t>The lifetime (seconds) of acontent object,Content Object, which is lastly cached.<!--The shortest lifetime among the cached content objects. The content object is removed after this timeout period. --> </t> </list></t> </dd> </dl> </section> <!-- Reply Sub-Block --> </section> <!-- Reply Block --> </section> <!-- Reply Message --> </section> <!-- CCNinfo Message Formats --> <!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% --> <section anchor="sec.user"title="CCNinfonumbered="true" toc="default"> <name>CCNinfo UserBehavior">Behavior</name> <!-- ========================================================== --> <sectiontitle="Sendingnumbered="true" toc="default"> <name>Sending CCNinfoRequest">Request</name> <t>A CCNinfo user invokes a CCNinfo user program (e.g., ccninfo command) that initiates a CCNinfo Request message and sends it to the user's adjacent neighbor router(s) of interest. The user later obtains both the routing path information and in-network cache information in the single Reply.</t> <t>When the CCNinfo user program initiates a Request message, itMUST<bcp14>MUST</bcp14> insert the necessary values, i.e., the "Request ID" and the "Node Identifier", in the Request block. The Request IDMUST<bcp14>MUST</bcp14> be unique for the CCNinfo user untils/he receivesthey receive the corresponding Reply message(s) or the Request is timed out.</t> <t>Owing to some policies, a router may want to validate the CCNinfo Requests using the CCNx ValidationPayload TLV (whether it accepts the Request or not) especially when the router receives the "full discovery request" (see <xref target="sec.forward.full-request"/>).format="default"/>). Accordingly, the CCNinfo user programMAY<bcp14>MAY</bcp14> require validating the Request message and appending the user's signature into the CCNx ValidationPayload TLV. The router then forwards the Request message. If the router does not approve the Request, it rejects the Request message as described in <xref target="sec.admin_prohibit"/>.</t> <!-- XXX or silently discards the Request??? -->format="default"/>.</t> <t>After the CCNinfo user program sends the Request message, until the Reply is timed out or the expected numbers of Replies or a Reply message with a non-zero ReturnCode in the fixed header is received, the CCNinfo user programMUST<bcp14>MUST</bcp14> keep the following information:HopLimit, specifiedHopLimit (specified in the fixedheader,header), RequestID, Flags,ID and Flags (specified in the Request header block), and NodeIdentifier,Identifier and Request ArrivalTime, specifiedTime (specified in the Requestblock.</t>block).</t> <!-- ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ --> <section anchor="sec.usr.path"title="Routingnumbered="true" toc="default"> <name>Routing PathInformation">Information</name> <t>A CCNinfo user can send a CCNinfo Request for investigating the routing path information for the specified named content. Using the Request, a legitimate user can obtain 1) the node identifiers of the intermediate routers, 2) the node identifier of the content forwarder, 3) the number of hops between the content forwarder and the consumer, and 4) the RTT between the content forwarder and the consumer, per name prefix. This CCNinfo Request is terminated when it reaches the content forwarder.</t> </section> <!-- ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ --> <section anchor="sec.usr.cache"title="In-Networknumbered="true" toc="default"> <name>In-Network CacheInformation">Information</name> <t>A CCNinfo user can send a CCNinfo Request for investigating in-network cache information. Using the Request, a legitimate user can obtain 1) the size of cachedcontent objects,Content Objects, 2) the number of cachedcontent objects,Content Objects, 3) the number of accesses (i.e., received Interests) per content, and 4) the lifetime and expiration time of the cachedcontent objects,Content Objects, for Content Store (CS) in the content forwarder, unless the content forwarder is capable of reporting them (see <xref target="sec.reply_subblk"/>).format="default"/>). This CCNinfo Request is terminated when it reaches the content forwarder.</t> </section> </section> <!-- ========================================================== --> <section anchor="sec.receiving_reply"title="Receivingnumbered="true" toc="default"> <name>Receiving CCNinfoReply">Reply</name> <t>A CCNinfo user program will receive one or multiple CCNinfo Reply messages from the adjacent neighbor router(s). When the program receives the Reply, itMUST<bcp14>MUST</bcp14> compare the kept Request ID and Node Identifier values to identify the Request and Reply pair. If they do not match, the Reply messageMUST<bcp14>MUST</bcp14> be silently discarded.</t> <t>If the number of Report blocks in the received Reply is more than the initial HopLimit value (which was inserted in the original Request), the ReplyMUST<bcp14>MUST</bcp14> be silently ignored.</t> <t>After the CCNinfo user has determined thats/he hasthey have traced the whole path or the maximum path thats/hethey can be expected to,s/hethey might collect statistics by waiting for a timeout. Useful statistics provided by CCNinfo are stated in <xreftarget="sec.diag"/>.</t>target="sec.diag" format="default"/>.</t> </section> </section> <!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% --> <section anchor="sec.router"title="Router Behavior">numbered="true" toc="default"> <name>Router Behavior</name> <!-- ========================================================== --> <sectiontitle="Usernumbered="true" toc="default"> <name>User and NeighborVerification">Verification</name> <t>Upon receiving a CCNinfo Request message, a routerMAY<bcp14>MAY</bcp14> examine whether a valid CCNinfo user has sent the message. If the router recognizes that the Request sender's signature specified in the Request is invalid, itSHOULD<bcp14>SHOULD</bcp14> terminate the Request, as defined in <xref target="sec.terminate.invalid"/>.</t>format="default"/>.</t> <t>Upon receiving a CCNinfoRequest/ReplyRequest or Reply message, a routerMAY<bcp14>MAY</bcp14> examine whether the message comes from a valid adjacent neighbor node. If the router recognizes that theRequest/ReplyRequest or Reply sender is invalid, itSHOULD<bcp14>SHOULD</bcp14> silently ignore theRequest/Replymessage, as specified in <xref target="sec.adjacency"/>.</t> <!-- The router next examines the number of Report blocks. If the number of Report blocks is equal or more than the value of the "HopLimit" in the fixed header, the Request MUST be silently ignored.-->format="default"/>.</t> </section> <!-- ========================================================== --> <section anchor="sec.receive.req"title="Receivingnumbered="true" toc="default"> <name>Receiving CCNinfoRequest">Request</name> <t>After a router accepts the CCNinfo Request message, it performs the following steps.</t><t><list style='numbers'> <t>The<ol spacing="normal" type="1"><li>The value of "HopLimit" in the fixed header andthatthe value of "SkipHop (Skip Hop Count)" in the Request block are counters that are decremented with each hop. If the HopLimit value is zero, the router terminates the Request, as defined in <xref target="sec.terminate.no_route"/>.format="default"/>. If the SkipHop value is equal to or more than the HopLimit value, the router terminates the Request, as defined in <xref target="sec.terminate.invalid"/>. Otherwise,format="default"/>; otherwise, until the SkipHop value becomes zero, the router forwards the Request message to the upstream router(s) without adding its own Report block and without replying to the Request. If the router does not know the upstream router(s) regarding the specified name prefix, it terminates the Request, as defined in <xref target="sec.terminate.no_route"/>.format="default"/>. It should be noted that the Request messages are terminated at the FHR; therefore, although the maximum value for the HopLimit is 255 and that for SkipHop is 15, if the Request messages reach the FHR before the HopLimit or SkipHop value becomes 0, the FHR silently discards the Request message and the Request is timedout.</t> <t>Theout.</li> <li>The router examines the Flags field (specified in <xref target="FlagVal"/>)format="default"/>) in the Request block of the received CCNinfo Request. If the "C" flag is not set, it is categorized as the "routing path information discovery". If the "C" flag is set, it is the "cache information discovery". If the "O" flag is set, it is the "publisherdiscovery".</t> <t>Ifdiscovery".</li> <li>If the Request is either "cache information discovery" or "routing path information discovery", the router examines its FIB and CS. If the router caches the specified content, it sends the Reply message with its own Reply block and sub-block(s). If the router cannot insert its own Reply block or sub-block(s) because of no space, it terminates the Request, as specified in <xref target="sec.terminate.no_space"/>.format="default"/>. If the router does not cache the specified content but knows the upstream neighbor router(s) for the specified name prefix, it creates the PIT entry,andinserts its own Report block in the hop-by-hopheaderheader, and forwards the Request to the upstream neighbor(s). If the router cannot insert its own Report block because of no space, or if the router does not cache the specified content and does not know the upstream neighbor router(s) for the specified name prefix, it terminates the Request, as defined in <xref target="sec.terminate.no_route"/>.</t> <t>Ifformat="default"/>.</li> <li>If the Request is the "publisher discovery", the router examines whether it is the FHR for the requested content. If the router is the FHR, it sends the Reply message with its own Report block and sub-blocks (in the case of cache information discovery) or the Reply message with its own Report block without adding any Reply sub-blocks (in the case of routing path information discovery). If the router is not the FHR but knows the upstream neighbor router(s) for the specified name prefix, it creates the PIT entry,andinserts its own Reportblockblock, and forwards the Request to the upstream neighbor(s). If the router cannot insert its own Report block in the hop-by-hop header because of no space, it terminates the Request, as specified in <xref target="sec.terminate.no_space"/>.format="default"/>. If the router is not the FHR and does not know the upstream neighbor router(s) for the specified name prefix, it terminates the Request, as defined in <xref target="sec.terminate.no_route"/>.format="default"/>. Note that in Cefore <xreftarget="refs.cefore" />,target="Cefore-site" format="default"/>, there is an API by which a publisher informs the application prefix to theFHRFHR, and the FHR registers it into the FIB. The prefix entry then can be statically configured on other routers or announced by a routingprotocol.</t> </list></t>protocol.</li> </ol> </section> <!-- ========================================================== --> <section anchor="sec.forward.request"title="Forwardingnumbered="true" toc="default"> <name>Forwarding CCNinfoRequest">Request</name> <!-- ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ --> <section anchor="sec.forward.regular"title="Regular Request">numbered="true" toc="default"> <name>Regular Request</name> <t>When a router decides to forward a Request message with its Report block to its upstream router(s), it specifies the Request Arrival Time and Node Identifier values in the Report block of the Request message. The router then forwards the Request message upstream toward the publisher or caching router based on the FIB entry like the ordinary Interest-Data exchanges in CCN.</t> <t>When the router forwards the Request message, itMUST<bcp14>MUST</bcp14> record the F flag and Request ID in the Request block of the Request message and exploiting path labels (specified in <xref target="sec.intro"/>)format="default"/>) at the corresponding PIT entry. The router can later check the PIT entry to correctly forward the Reply message(s) back.</t> <t>CCNinfo supports multipath forwarding. The Request messages can be forwarded to multiple neighbor routers.<!-- XXX accept strategy, no SHOULD XXX -->Some routers may have a strategy for multipath forwarding; when a router sends Interest messages to multiple neighbor routers, it may delay or prioritize to send the message to the upstream routers. The CCNinfo Request, as the default, complies with such strategies; a CCNinfo user could trace the actual forwarding path based on the forwarding strategy and will receive a single Reply message such as acontent object.</t>Content Object.</t> </section> <!-- ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ --> <section anchor="sec.forward.full-request"title="Fullnumbered="true" toc="default"> <name>Full DiscoveryRequest">Request</name> <t>There may be a case wherein a CCNinfo user wants to discover all possible forwarding paths and content forwarders based on the routers' FIBs. The "full discovery request" enables this functionality. If a CCNinfo user sets the F flag in the Request block of the Request message (as seen in <xref target="FlagVal"/>)format="default"/>) to request the full discovery, the upstream routers simultaneously forward the Requests to all multiple upstream routers based on the FIBs. Then, the CCNinfo user can trace all possible forwarding paths. As seen in <xreftarget="fig:reply_force" />,target="fig_reply_force" format="default"/>, each router forwards the Reply message along its PITentryentry, and finally, the CCNinfo user receives two Reply messages: one from the FHR (Router C) and the other from the Caching router.</t> <figureanchor="fig:reply_force" title="Full discovery request.anchor="fig_reply_force"> <name>Full Discovery Request: Replymessages forwardedMessages Forwarded bypublisherthe Publisher androuters.">Routers</name> <artworkalign="center">align="center" name="" type="" alt=""><![CDATA[ 3. Reply(C) 2. Reply(C) 3. Reply(P) 2. Reply(P) 1. Reply(P) +----+ +----+ +----+ | | | | | | v | v | v | +--------+ +--------+ +--------+ +--------+ +---------+ | CCNinfo|----| Router |----| Router |----| Router |----|Publisher| | user | | A | | B | | C | | | +--------+ +--------+ +--------+ +--------+ +---------+ ^ \ +-------+ 1. Reply(C) \ | Cache | \ +---------+ | \| Caching |----+ | router | +---------+</artwork>]]></artwork> </figure> <t>To receive different Reply messages forwarded from different routers, the PIT entries initiated by CCNinfo remain until the configured CCNinfo Reply Timeout (<xref target="sec.timer"/>)format="default"/>) is expired. In other words, unlike the ordinary Interest-Data exchanges in CCN, if routers that accept the full discovery request receive the full discovery request, the routersSHOULD NOT<bcp14>SHOULD NOT</bcp14> remove the PIT entry created by the full discovery request until the CCNinfo Reply Timeout value expires.</t> <t>Note that the full discovery request is anOPTIONAL<bcp14>OPTIONAL</bcp14> implementation of CCNinfo; it may not be implemented on routers. Even if it is implemented on a router, it may not accept the full discovery request from non-validated CCNinfo users or routers or because of its policy. If a router does not accept the full discovery request, it rejects the full discovery request as described in <xref target="sec.admin_prohibit"/>.format="default"/>. Routers that enable the full discovery requestMAY<bcp14>MAY</bcp14> rate-limit Replies, as described in <xref target="sec.rate_limit.reply"/>format="default"/> as well.</t> </section> </section> <!-- ========================================================== --> <section anchor="sec.send.reply"title="Sendingnumbered="true" toc="default"> <name>Sending CCNinfoReply">Reply</name> <t>If there is a caching router or FHR for the specified content within the specified hop count along the path, the caching router or FHR sends back the Reply message toward the CCNinfo user and terminates the Request.</t> <t>When a router decides to send a Reply message to its downstream neighbor router or the CCNinfo user with a NO_ERROR return code, it inserts a Report block with the Request Arrival Time and Node Identifier values to the Request message. Then, the router inserts the corresponding Reply sub-block(s) (<xref target="Reply_subblock"/>)format="default"/>) to the payload. The router finally changes the Type field in the fixed header from PT_CCNINFO_REQUEST to PT_CCNINFO_REPLY and forwards the message back as the Reply toward the CCNinfo user in a hop-by-hop manner.</t><!-- <t>The total number of the traced routers SHOULD be the sum of the Report blocks in the Request (including the one just added), even though there may be the Request blocks with null Node Identifier because of some administrative policy (see <xref target="sec.policy" />). The router that creates the Reply message SHOULD examine the number of the located Report block TLVs and compare it with the HopCount field value in the Request block TLV in the Reply message.</t> <t>When a router decides to send the Reply message for the Request for the cache or routing path information discovery, it forms the Reply message including a Reply block and a Reply sub-block and various cache information. After the router puts the NO_ERROR return code in the fixed header, it sends the Reply back toward the CCNinfo user.</t>--><t>If a router cannot continue the Request, the routerMUST<bcp14>MUST</bcp14> put an appropriate ReturnCode in the Request message, change the Type field value in the fixed header from PT_CCNINFO_REQUEST to PT_CCNINFO_REPLY, and forward the Reply message back toward the CCNinfo user to terminate the Request (see <xref target="sec.terminate"/>).</t>format="default"/>).</t> </section> <!-- ========================================================== --> <sectiontitle="Forwardingnumbered="true" toc="default"> <name>Forwarding CCNinfoReply">Reply</name> <t>When a router receives a CCNinfo Reply whose Request ID and Node Identifier values match those in the PIT entry, which is sent from a valid adjacent neighbor router, it forwards the CCNinfo Reply back toward the CCNinfo user. If the router does not receive the corresponding Reply within the [CCNinfo Reply Timeout] period, then it removes the corresponding PIT entry and terminates the trace.</t> <t>The Flags field in the Request block TLV is used to indicate whether the router keeps the PIT entry during the CCNinfo Reply Timeout even after one or more corresponding Reply messages are forwarded. When the CCNinfo user does not set the F flag (i.e., "0"), the intermediate routers immediately remove the PIT entry whenever they forward the corresponding Reply message. When the CCNinfo user sets the F flag (i.e., "1"), which means the CCNinfo user chooses the "full discovery request" (see <xref target="sec.forward.full-request"/>),format="default"/>), the intermediate routers keep the PIT entry within the [CCNinfo Reply Timeout] period. After this timeout, the PIT entry is removed.</t> <t>CCNinfo RepliesMUST NOT<bcp14>MUST NOT</bcp14> be cached in routers upon the transmission of Reply messages.</t> </section> <!-- ========================================================== --> <sectiontitle="PITnumbered="true" toc="default"> <name>PIT Entry Management for MultipathSupport">Support</name> <t>Within a network with a multipath condition, there is a case (<xreftarget="fig:multi-replies" />)target="fig_multi-replies" format="default"/>) wherein a single CCNinfo Request is split into multiple Requests (e.g., at Router A), which are injected into a single router (Router D). In this case, multiple Replies with the same Request ID and Node Identifier values, including different Reportblocksblocks, are received by the router (Router D).</t> <figureanchor="fig:multi-replies" title="">anchor="fig_multi-replies"> <name>An Example of Multipath Network Topology</name> <artworkalign="center">align="center" name="" type="" alt=""><![CDATA[ +--------+ | Router | | B | +--------+ / \ / \ +--------+ +--------+ +--------+ +---------+ | CCNinfo|----| Router | | Router | ... |Publisher| | user | | A | | D | | | +--------+ +--------+ +--------+ +---------+ \ / \ / +--------+ | Router | | C | +--------+</artwork>]]></artwork> </figure> <t>To recognize different CCNinfo Reply messages, the routersMUST<bcp14>MUST</bcp14> distinguish the PIT entries by the Request ID and exploiting path labels, which could be a hash value of the concatenation information of the cumulateNode Identifiersnode identifiers in the hop-by-hop header and the specified content name. For example, when Router D in <xreftarget="fig:multi-replies" />target="fig_multi-replies" format="default"/> receives a CCNinfo Request from Router B, its PIT includes the Request ID and value such as H((Router_A|Router_B)|content_name), where "H" indicates some hash function and "|" indicates concatenation. When Router D receives a CCNinfo Request from Router C, its PIT includes the same Request ID and value of H((Router_A|Router_C)|content_name). Two different Replies are later received on RouterDD, and each Reply is appropriately forwarded to Router B and Router C, respectively. Note that two Reply messages coming from Router B and Router C are reached at Router A, but the CCNinfo user can only receive the first Reply message either from Router B or Router C as Router A removes the corresponding PIT entry after it forwards the first Reply.</t> <t>To avoid routing loops, when a router seeks the cumulateNode Identifiersnode identifiers of the Report blocks in the hop-by-hop header, itMUST<bcp14>MUST</bcp14> examine whether its ownNode Identifiernode identifier is not previously inserted. If a router detects its ownNode Identifiernode identifier in the hop-by-hop header, the router inserts its Report block and terminates the Request as will be described in <xref target="sec.terminate.fatal"/>.</t> <!-- <t>CCNinfo Requests SHOULD NOT result in PIT aggregation in routers during the Request message transmission.</t> XXX No more needed because of unique PIT entry given by hash value. -->format="default"/>.</t> </section> </section> <!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% --> <section anchor="sec.terminate"title="CCNinfo Termination">numbered="true" toc="default"> <name>CCNinfo Termination</name> <t>When performing a hop-by-hop trace, it is necessary to determine when to stop the trace. There are several cases when an intermediate router might return a Reply before a Request reaches the caching router or the FHR.</t> <sectiontitle="Arrivingnumbered="true" toc="default"> <name>Arriving atFirst-hop Router">First-Hop Router</name> <t>A CCNinfo Request can be determined to have arrived at the FHR. To ensure that a router recognizes that it is the FHR for the specified content, it needs to have a FIB entry (or to attach) to the corresponding publisher or the content.</t> </section> <sectiontitle="Arrivingnumbered="true" toc="default"> <name>Arriving at Router HavingCache">Cache</name> <t>A CCNinfo Request can be determined to have arrived at the router having the specified content cache within the specified HopLimit.</t> </section> <sectiontitle="Arrivingnumbered="true" toc="default"> <name>Arriving at LastRouter">Router</name> <t>A CCNinfo Request can be determined to have arrived at the last router of the specified HopLimit. If the last router does not have the corresponding cache, itMUST<bcp14>MUST</bcp14> insert its Report block and send the Reply message with a NO_INFO return code without appending any Reply(sub-)blockblock or sub-block TLVs.</t> </section> <section anchor="sec.terminate.invalid"title="Invalid Request">numbered="true" toc="default"> <name>Invalid Request</name> <t>If the router does not validate the Request or the Reply even it is required, the routerMUST<bcp14>MUST</bcp14> note a ReturnCode of INVALID_REQUEST in the fixed header of the message, insert its Report block, and forward the message as the Reply back to the CCNinfo user. The routerMAY,<bcp14>MAY</bcp14>, however, randomly ignore the received invalid messages. (See <xref target="sec.rate_limit.request"/>.)</t>format="default"/>.)</t> </section> <section anchor="sec.terminate.no_route"title="No Route">numbered="true" toc="default"> <name>No Route</name> <t>If the router cannot determine the routing paths or neighbor routers for the specified name prefix within the specified HopLimit, itMUST<bcp14>MUST</bcp14> note a ReturnCode of NO_ROUTE in the fixed header of the message, insert its Report block, and forward the message as the Reply back to the CCNinfo user.</t> </section> <sectiontitle="No Information">numbered="true" toc="default"> <name>No Information</name> <t>If the router does not have any information about the specified name prefix within the specified HopLimit, itMUST<bcp14>MUST</bcp14> note a ReturnCode of NO_INFO in the fixed header of the message, insert its Report block, and forward the message as the Reply back to the CCNinfo user.</t> </section> <section anchor="sec.terminate.no_space"title="No Space">numbered="true" toc="default"> <name>No Space</name> <t>If appending the Reportblock orblock, the Reply(sub-)blockblock, or Reply sub-block would make the hop-by-hop header longer than 247 bytes or the Request packet longer than the MTU of the Incoming face,<!-- or longer than 1280 bytes (in the case of IPv6 as the payload <xref target="refs.IPv6"/>),-->the routerMUST<bcp14>MUST</bcp14> note a ReturnCode of NO_SPACE in the fixed header of the message and forward the message as the Reply back to the CCNinfo user.</t> </section> <section anchor="sec.terminate.fatal"title="Fatal Error">numbered="true" toc="default"> <name>Fatal Error</name> <t>If a CCNinfo Request has encountered a fatal error, the routerMUST<bcp14>MUST</bcp14> note a ReturnCode of FATAL_ERROR in the fixed header of the message and forward the message as the Reply back to the CCNinfo user. This may happen, for example, when the router detects some routing loop in the Request blocks (see <xref target="sec.intro"/>).format="default"/>). The fatal error can be encoded with another error: if a router detects routing loop but cannot insert its Report block, itMUST<bcp14>MUST</bcp14> note NO_SPACE and FATAL_ERROR ReturnCodes (i.e.,%x85)0x85) in the fixed header and forward the message back to the CCNinfo user.</t> </section> <sectiontitle="CCNinfonumbered="true" toc="default"> <name>CCNinfo ReplyTimeout">Timeout</name> <t>If a router receives the Request or Reply message that expires its own [CCNinfo Reply Timeout] value (<xreftarget="sec.timer"/>),target="sec.timer" format="default"/>), the router will silently discard the Request or Reply message.</t> </section> <section anchor="sec.nonsupport"title="Non-Supported Node">numbered="true" toc="default"> <name>Non-Supported Node</name> <t>Cases will arise in which a router or a FHR along the path does not support CCNinfo. In such cases, a CCNinfo user and routers that forward the CCNinfo Request will time out the CCNinfo request.</t><!--a downstream router that supports ccninfo will reply to the ccninfo user with a message indicating that the upstream router does not support ccninfo. XXXX how to detect non-supported router???--></section> <section anchor="sec.admin_prohibit"title="Administratively Prohibited">numbered="true" toc="default"> <name>Administratively Prohibited</name> <t>If CCNinfo is administratively prohibited, the router rejects the Request message andMUST<bcp14>MUST</bcp14> send the CCNinfo Reply with the ReturnCode of ADMIN_PROHIB. The routerMAY,<bcp14>MAY</bcp14>, however, randomly ignore the Request messages to be rejected (see <xref target="sec.rate_limit.request"/>).</t>format="default"/>).</t> </section> </section> <!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% --> <section anchor="sec.config"title="Configurations">numbered="true" toc="default"> <name>Configurations</name> <section anchor="sec.timer"title="CCNinfonumbered="true" toc="default"> <name>CCNinfo ReplyTimeout">Timeout</name> <t>The [CCNinfo Reply Timeout] value is used to time out a CCNinfo Reply. The value for a router can be statically configured by the router'sadministrators/operators.administrators and/or operators. The default value is 3 (seconds). The [CCNinfo Reply Timeout] valueSHOULD NOT<bcp14>SHOULD NOT</bcp14> be larger than 4 (seconds) andSHOULD NOT<bcp14>SHOULD NOT</bcp14> be lower than 2 (seconds).</t> </section> <sectiontitle="HopLimitnumbered="true" toc="default"> <name>HopLimit in FixedHeader">Header</name> <t>If a CCNinfo user does not specify the HopLimit value in the fixed header for a Request message as the HopLimit, the HopLimit is set to 32. Note that 0 HopLimit is an invalid Request; hence, the router in this case follows the way defined in <xref target="sec.terminate.invalid"/>.</t>format="default"/>.</t> </section> <section anchor="sec.acl.config"title="Access Control">numbered="true" toc="default"> <name>Access Control</name> <t>A routerMAY<bcp14>MAY</bcp14> configure the valid or invalid networks to enable an access control. The access controlMAY<bcp14>MAY</bcp14> be defined per name prefix, such as "who can retrieve which name prefix" (see <xref target="sec.acl"/>).</t>format="default"/>).</t> </section> </section> <!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% --> <section anchor="sec.diag"title="Diagnosis and Analysis"> <section title="Numbernumbered="true" toc="default"> <name>Diagnosis and Analysis</name> <section numbered="true" toc="default"> <name>Number of Hops andRTT">RTT</name> <t>A CCNinfo Request message is forwarded in a hop-by-hop manner and each forwarding router appends its own Report block. We can then verify the number of hops to reach the content forwarder or publisher and the RTT between the content forwarder or publisher.</t> </section> <sectiontitle="Cachingnumbered="true" toc="default"> <name>Caching RouterIdentification">Identification</name> <t>While some routers may hide their node identifiers with all-zeros in the Report blocks (as seen in <xref target="sec.policy"/>),format="default"/>), the routers in the path from the CCNinfo user to the content forwarder can be identified.</t> </section> <sectiontitle="TTLnumbered="true" toc="default"> <name>TTL or HopLimit">Limit</name> <t>By taking the HopLimit from the content forwarder and forwarding the TTL threshold over all hops, it is possible to discover the TTL or hop limit required for the content forwarder to reach the CCNinfo user.</t> </section> <section anchor="sec.delay"title="Time Delay">numbered="true" toc="default"> <name>Time Delay</name> <t>If the routers have synchronized clocks, it is possible to estimate the propagation and queuing delays from the differences between the timestamps at the successive hops. However, this delay includes the control processing overhead; therefore, it is not necessarily indicative of the delay that would be experienced by the data traffic.</t> </section> <sectiontitle="Path Stretch">numbered="true" toc="default"> <name>Path Stretch</name> <t>By obtaining the path stretch "d / P", where "d" is the hop count of the data and "P" is the hop count from the consumer to the publisher, we can measure the improvements in path stretch in various cases, such as in different caching and routing algorithms. We can then facilitate the investigation of the performance of the protocol.</t> </section> <sectiontitle="Cachenumbered="true" toc="default"> <name>Cache HitProbability">Probability</name> <t>CCNinfo can show the number of receivedinterestsInterests per cache or chunk on a router. Accordingly, CCNinfo measures the content popularity (i.e., the number of accesses for eachcontent/cache),content and/or cache), thereby enabling the investigation of the routing/caching strategy in networks.</t> </section> </section> <!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% --> <section anchor="sec.iana"title="IANA Considerations"> <!-- <t>New assignments can only be made via a Standards Action as specified in <xref target="refs.IANA" />. This document does not intend to be the standard document. However, the new assignments such as the ReturnCode and various type values will be considered when this specification becomes the RFC.</t>-->numbered="true" toc="default"> <name>IANA Considerations</name> <t>This section details each kind of CCNx protocol value thatcan behas been registered. As per <xreftarget="refs.IANA" />, this section makestarget="RFC8126" format="default"/>, four assignments have been made infourexistingregistriesregistries, andcreatesa new Reply Type registry has been created in the "Content-Centric Networking (CCNx)" registrygroup. The registration procedure is "RFC Required", which requires only that this document be published as an RFC.</t>group.</t> <section anchor="sec.iana.pt"title="Packetnumbered="true" toc="default"> <name>Packet TypeRegistry">Registry</name> <t>As shown in <xreftarget='Type_val' />,target="Type_val" format="default"/>, CCNinfo defines two packet types, PT_CCNINFO_REQUEST and PT_CCNINFO_REPLY, whosesuggestedvalues are%x030x03 and%x04,0x04, respectively.</t> </section> <section anchor="sec.iana.tlt"title="Top-Levelnumbered="true" toc="default"> <name>Top-Level TypeRegistry">Registry</name> <t>As shown in <xreftarget='Top-level_Type' />,target="Top-level_Type" format="default"/>, CCNinfo defines one top-level type, T_DISCOVERY, whosesuggestedvalue is%x0005.</t>0x0005.</t> </section> <section anchor="sec.iana.hbh"title="Hop-by-Hopnumbered="true" toc="default"> <name>Hop-by-Hop TypeRegistry">Registry</name> <t>As shown in <xreftarget='Hop-by-hop_Type' />,target="Hop-by-hop_Type" format="default"/>, CCNinfo defines two hop-by-hop types, T_DISC_REQHDR and T_DISC_REPORT, whosesuggestedvalues are%x00080x0008 and%x0009,0x0009, respectively.</t> </section> <section anchor="sec.iana.msg"title="Messagenumbered="true" toc="default"> <name>Message TypeRegistry">Registry</name> <t>As shown in <xreftarget='CCNx_Type' />,target="CCNx_Type" format="default"/>, CCNinfo defines two message types, T_DISC_REQ and T_DISC_REPLY, whosesuggestedvalues are%x00070x000D and%x0008,0x000E, respectively.</t> </section> <section anchor="sec.iana.reply"title="Replynumbered="true" toc="default"> <name>Reply TypeRegistry">Registry</name> <t>IANA has created the "CCNx Reply Types" registry and allocated the reply types. The registration procedure is "RFC Required" <xref target="RFC8126"/>. The Type value is 2 octets. The range is%x0000-%xFFFF.0x0000-0xFFFF. As shown in <xreftarget='Sub_Type' />,target="Sub_Type" format="default"/>, CCNinfo defines three reply types, T_DISC_CONTENT, T_DISC_CONTENT_PUBLISHER, and T_ORG, whosesuggestedvalues are%x0000, %x0001,0x0000, 0x0001, and%x0FFF,0x0FFF, respectively.</t> </section> </section> <!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% --> <section anchor="sec.sec"title="Security Considerations">numbered="true" toc="default"> <name>Security Considerations</name> <t>This section addresses some of the security considerations.</t> <!-- ========================================================== --> <section anchor="sec.policy"title="Policy-Basednumbered="true" toc="default"> <name>Policy-Based Information Provisioning forRequest">Request</name> <t>Although CCNinfo gives excellent troubleshooting cues, some network administrators or operators may not want to disclose everything about their network to the public or may wish to securely transmit private information to specific members of their networks. CCNinfo provides policy-based information provisioning, thereby allowing network administrators to specify their response policy for each router.</t> <t>The access policy regarding "who is allowed to retrieve" and/or "what kind of cache information" can be defined for each router. For the former type of access policy, routers with the specified contentMAY<bcp14>MAY</bcp14> examine the signature enclosed in the Request message and decide whether they should notify the content information in the Reply. If the routers decide to not notify the content information, theyMUST<bcp14>MUST</bcp14> send the CCNinfo Reply with the ReturnCode of ADMIN_PROHIB without appending any Reply(sub-)blockblock or sub-block TLVs. For the latter type of policy, the permission, whether (1) All (all cache information is disclosed), (2) Partial (cache information with a particular name prefix can (or cannot) be disclosed), or (3) Deny (no cache information is disclosed), is defined at the routers.</t> <t>In contrast, we entail that each router does not disrupt the forwarding of CCNinfo Request and Reply messages. When a Request message is received, the routerSHOULD<bcp14>SHOULD</bcp14> insert the Report block if the ReturnCode is NO_ERROR. Here, according to the policy configuration, the Node Identifier field in the Report blockMAY<bcp14>MAY</bcp14> be null (i.e., all-zeros), but the Request Arrival Time fieldSHOULD NOT<bcp14>SHOULD NOT</bcp14> be null. Finally, the routerSHOULD<bcp14>SHOULD</bcp14> forward the Request message to the upstream router toward the content forwarder if the ReturnCode is kept with NO_ERROR.</t> </section> <!-- ========================================================== --> <section anchor="sec.acl"title="Filteringnumbered="true" toc="default"> <name>Filtering CCNinfo Users Located in InvalidNetworks">Networks</name> <t>A routerMAY<bcp14>MAY</bcp14> support an access control mechanism to filter out Requests from invalid CCNinfo users. To accomplish this, invalid networks (or domains) could, for example, be configured via a list ofallowed/disallowedallowed or disallowed networks (as observed in <xref target="sec.acl.config"/>).format="default"/>). If a Request is received from a disallowed network (according to theNode Identifiernode identifier in the Request block), the RequestMUST NOT<bcp14>MUST NOT</bcp14> be processed and the Reply with the ReturnCode of INFO_HIDDENSHOULD<bcp14>SHOULD</bcp14> be used to note that. The routerMAY,<bcp14>MAY</bcp14>, however, performrate limitedrate-limited logging of such events.</t> </section> <!-- ========================================================== --> <sectiontitle="Topology Discovery">numbered="true" toc="default"> <name>Topology Discovery</name> <t>CCNinfo can be used to discover actively used topologies. If a network topology is not disclosed, CCNinfo RequestsSHOULD<bcp14>SHOULD</bcp14> be restricted at the border of the domain using the ADMIN_PROHIB return code.</t> </section> <!-- ========================================================== --> <sectiontitle="Characteristicsnumbered="true" toc="default"> <name>Characteristics ofContent">Content</name> <t>CCNinfo can be used to discover the type of content being sent by publishers. If this information is a secret, CCNinfo RequestsSHOULD<bcp14>SHOULD</bcp14> be restricted at the border of the domain, using the ADMIN_PROHIB return code.</t> </section> <!-- ========================================================== --> <section anchor="sec.compute"title="Computational Attacks">numbered="true" toc="default"> <name>Computational Attacks</name> <t>CCNinfo may impose heavy tasks at content forwarders because it makes content forwarders seek their internal cache states reported in the Reply messages whenever they form the Reply messages. The current CCNinfo specification allows to return null values for several fields, such as First/Last Seqnum or Elapsed Cache Time fields in the Reply sub-block. As mentioned in <xref target="sec.reply_subblk"/>,format="default"/>, these valuesMAY<bcp14>MAY</bcp14> be null. This means that the content forwardercan notcannot only hide these values owing toprivacy/security policies,privacy and security policies but also skip the implementations of the complex functions to report these values.</t> </section> <!-- ========================================================== --> <section anchor="sec.timeout"title="Longernumbered="true" toc="default"> <name>Longer or Shorter CCNinfo ReplyTimeout">Timeout</name> <t>Routers can configure CCNinfo Reply Timeout (<xref target="sec.timer"/>),format="default"/>), which is the allowable timeout value to keep the PIT entry. If routers configure a longer timeout value, there may be an attractive attack vector against the PIT memory. Moreover, especially when the full discovery request option (<xref target="sec.forward.request"/>)format="default"/>) is specified for the CCNinfo Request, several Reply messages may be returned and cause a response storm. (See <xref target="sec.rate_limit.reply"/>format="default"/> for rate-limiting to avoid the storm). To avoid DoS attacks, routersMAY<bcp14>MAY</bcp14> configure the timeout value, which is shorter than the user-configured CCNinfo timeout value. However, if it is too short, the Request may be timed out and the CCNinfo user does not receive all Replies;s/hethey onlyretrievesretrieve the partial path information (i.e., information about a part of the tree).</t> <t>There may be a way to enable incremental exploration (i.e., to explore the part of the tree that was not explored by the previous operation); however, discussing such mechanisms is out of scope of this document.</t> </section> <!-- ========================================================== --> <section anchor="sec.rate_limit.request"title="Limitingnumbered="true" toc="default"> <name>Limiting RequestRates">Rates</name> <t>A routerMAY<bcp14>MAY</bcp14> rate-limit CCNinfo Requests by ignoring some of the consecutive messages. The routerMAY<bcp14>MAY</bcp14> randomly ignore the received messages to minimize the processing overhead, i.e., to keep fairness in processingrequests,requests or to prevent traffic amplification. In such a case, no error message is returned. The rate limit function is left to the router's implementation.</t> </section> <!-- ========================================================== --> <section anchor="sec.rate_limit.reply"title="Limitingnumbered="true" toc="default"> <name>Limiting ReplyRates">Rates</name> <t>CCNinfo supporting multipath forwarding may result in one Request returning multiple Reply messages. To prevent abuse, the routers in the traced pathMAY<bcp14>MAY</bcp14> need to rate-limit the Replies. In such a case, no error message is returned. The rate limit function is left to the router's implementation.</t> </section> <!-- ========================================================== --> <section anchor="sec.adjacency"title="Adjacency Verification">numbered="true" toc="default"> <name>Adjacency Verification</name> <t>It is assumed that the CCNinfo Request and Reply messages are forwarded by adjacent neighbor nodes or routers. The CCNx message format or semantics do not define a secure way to verify thenode/routernode and/or router adjacency, whileHopAutha hop-by-hop authentication such as <xreftarget="refs.hopauth" />target="DCAuth" format="default"/> provides a possible method for an adjacency verification and defines the corresponding message format for adjacency verification as well as the router behaviors. CCNinfoMAY<bcp14>MAY</bcp14> use a similar method for node adjacency verification. </t> </section> </section><!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% --> <section title="Acknowledgements"> <t>The authors would like to thank Jerome Francois, Erik Kline, Spyridon Mastorakis, Paulo Mendes, Ilya Moiseenko, David Oran, and Thierry Turletti for their valuable comments and suggestions on this document.</t> </section> <!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% --></middle> <!-- *****BACK MATTER ***** --> <back><references title="Normative References"> <reference anchor="refs.ccnx"> <front> <title>CCNx Messages in TLV Format</title> <author initials="M" surname="Mosko"/> <author initials="I" surname="Solis"/> <author initials="C" surname="Wood"/> <date month="July" year="2019"/> </front> <seriesInfo name="RFC" value="8609"/> </reference> <reference anchor="refs.semantics"> <front> <title>CCNx Semantics</title> <author initials="M" surname="Mosko"/> <author initials="I" surname="Solis"/> <author initials="C" surname="Wood"/> <date month="July" year="2019"/> </front> <seriesInfo name="RFC" value="8569"/> </reference> <reference anchor="refs.RFC2119" target='https://www.rfc-editor.org/info/rfc2119'> <front> <title>Key words for use in RFCs to Indicate Requirement Levels</title> <author initials='S.' surname='Bradner' fullname='S. Bradner'><organization /></author> <date year='1997' month='March'<displayreference target="I-D.irtf-icnrg-icnping" to="ICN-PING" /><abstract><t>In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.</t></abstract> </front> <seriesInfo name='BCP' value='14'/> <seriesInfo name='RFC' value='2119'/> <seriesInfo name='DOI' value='10.17487/RFC2119'/> </reference> <reference anchor="refs.RFC8174" target='https://www.rfc-editor.org/info/rfc8174'> <front> <title>Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words</title> <author initials='B.' surname='Leiba' fullname='B. Leiba'><organization /></author> <date year='2017' month='May'<displayreference target="I-D.irtf-icnrg-icntraceroute" to="ICN-TRACEROUTE" /></front> </reference> <reference anchor='refs.IANA' target='https://www.rfc-editor.org/info/rfc8126'> <front> <title>Guidelines for Writing an IANA Considerations Section in RFCs</title> <author initials='M.' surname='Cotton' fullname='M. Cotton'><organization /></author> <author initials='B.' surname='Leiba' fullname='B. Leiba'><organization /></author> <author initials='T.' surname='Narten' fullname='T. Narten'><organization /></author> <date year='2017' month='June' /> <abstract><t>Many protocols make use of points of extensibility that use constants to identify various protocol parameters. To ensure that the values in these fields do not have conflicting uses and to promote interoperability, their allocations are often coordinated by a central record keeper. For IETF protocols, that role is filled by the Internet Assigned Numbers Authority (IANA).</t><t>To make assignments in a given registry prudently, guidance describing the conditions under which new values should be assigned, as well as when and how modifications to existing values can be made, is needed. This document defines a framework for the documentation of these guidelines by specification authors, in order to assure that the provided guidance for the IANA Considerations is clear and addresses the various issues that are likely in the operation of a registry.</t><t>This is the third edition of this document; it obsoletes RFC 5226.</t></abstract> </front> <seriesInfo name='BCP' value='26'/> <seriesInfo name='RFC' value='8126'/> <seriesInfo name='DOI' value='10.17487/RFC8126'/> </reference><references> <name>References</name> <references> <name>Normative References</name> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8609.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8569.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.2119.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8174.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8126.xml"/> </references><references title="Informative References"> <reference anchor="refs.term"> <front> <title>Information-Centric Networking (ICN): Content-Centric Networking (CCNx) and Named Data Networking (NDN) Terminology</title> <author initials="C" surname="Wood"/> <author initials="A" surname="Afanasyev"/> <author initials="L" surname="Zhang"/> <author initials="D" surname="Oran"/> <author initials="C" surname="Tschudin"/> <date month="June" year="2020"/> </front> <seriesInfo name="RFC" value="8793"/> </reference><references> <name>Informative References</name> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8793.xml"/> <referenceanchor="refs.commag">anchor="Contrace"> <front> <title>Contrace: ATooltool forMeasuringmeasuring andTracing Content-Centric Networks</title>tracing content-centric networks</title> <author initials="H" surname="Asaeda"/> <author initials="K" surname="Matsuzono"/> <author initials="T" surname="Turletti"/> <date month="March" year="2015"/> </front> <seriesInfoname="IEEEname="DOI" value="10.1109/MCOM.2015.7060502"/> <refcontent>IEEE CommunicationsMagazine," value="Vol.53, No.3, pp.182-188"/> </reference> <reference anchor="refs.icnping"> <front> <title>ICN Ping Protocol Specification</title> <author initials="S" surname="Mastorakis"/> <author initials="J" surname="Gibson"/> <author initials="I" surname="Moiseenko"/> <author initials="R" surname="Droms"/> <author initials="D" surname="Oran"/> <date month="May" year="2022"/> </front> <seriesInfo name="draft-irtf-icnrg-icnping-06" value="(work in progress)"/> </reference> <reference anchor="refs.icntrace"> <front> <title>ICN Traceroute Protocol Specification</title> <author initials="S" surname="Mastorakis"/> <author initials="J" surname="Gibson"/> <author initials="I" surname="Moiseenko"/> <author initials="R" surname="Droms"/> <author initials="D" surname="Oran"/> <date month="May" year="2022"/> </front> <seriesInfo name="draft-irtf-icnrg-icntraceroute-06" value="(work in progress)"/> </reference> <reference anchor="refs.mtrace2"> <front> <title>Mtrace Version 2: Traceroute Facility for IP Multicast</title> <author initials="H" surname="Asaeda"/> <author initials="K" surname="Mayer"/> <author initials="W" surname="Lee"/> <date month="October" year="2018"/> </front> <seriesInfo name="RFC" value="8487"/>Magazine, Vol. 53, No. 3, pp. 182-188</refcontent> </reference> <!-- [I-D.irtf-icnrg-icnping] IESG state I-D Exists as of 1/31/23--> <xi:include href="https://datatracker.ietf.org/doc/bibxml3/reference.I-D.irtf-icnrg-icnping.xml"/> <!-- [I-D.irtf-icnrg-icntraceroute] IESG state I-D Exists as of 1/31/23--> <xi:include href="https://datatracker.ietf.org/doc/bibxml3/reference.I-D.irtf-icnrg-icntraceroute.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8487.xml"/> <referenceanchor="refs.dcauth">anchor="DCAuth"> <front> <title>DCAuth: Data-Centric Authentication for Secure In-Network Big-Data Retrieval</title> <author initials="R" surname="Li"/> <author initials="H" surname="Asaeda"/> <author initials="J" surname="Wu"/> <date month="October" year="2018"/> </front> <seriesInfoname="IEEEname="DOI" value="10.1109/TNSE.2018.2872049"/> <refcontent>IEEE Transactions on Network Science andEngineering (TNSE)" value=""/> </reference>--> <reference anchor="refs.hopauth"> <front> <title>Hop-by-Hop Authentication in Content-Centric Networking/Named Data Networking</title> <author initials="R" surname="Li"/> <author initials="H" surname="Asaeda"/> <date month="February" year="2020"/> </front> <seriesInfo name="draft-li-icnrg-hopauth-02" value="(work in progress)"/>Engineering, Vol. 7, No. 1, pp. 15-27</refcontent> </reference> <!-- [I-D.li-icnrg-hopauth] IESG state Expired --> <!--<xi:include href="https://datatracker.ietf.org/doc/bibxml3/reference.I-D.li-icnrg-hopauth.xml"/> [HA] replaced by above journal as hopauth is expired and not maintained.--> <referenceanchor="refs.acur">anchor="CONSEC-CACHING"> <front> <title>Consecutive Caching and Adaptive Retrieval for In-Network Big Data Sharing</title> <author initials="R" surname="Li"/> <author initials="K" surname="Matsuzono"/> <author initials="H" surname="Asaeda"/> <author initials="X" surname="Fu"/> <date month="May" year="2018"/> </front> <seriesInfoname="Proc.name="DOI" value="10.1109/ICC.2018.8422233"/> <refcontent>Proc. IEEEICC," value="KansasICC, Kansas City,USA"/>MO, USA</refcontent> </reference> <referenceanchor="refs.ieice">anchor="Cefore"> <front> <title>Cefore: Software Platform Enabling Content-Centric Networking and Beyond</title> <author initials="H" surname="Asaeda"/> <author initials="A" surname="Ooka"/> <author initials="K" surname="Matsuzono"/> <author initials="R" surname="Li"/> <date month="September" year="2019"/> </front> <seriesInfoname="IEICEname="DOI" value="10.1587/transcom.2018EII0001"/> <refcontent>IEICE Transaction onCommunications," value="Vol.E102-B, No.9, pp.1792-1803"/>Communications, Volume E102-B, Issue 9, pp. 1792-1803</refcontent> </reference> <referenceanchor="refs.cefore"anchor="Cefore-site" target="https://cefore.net/"> <front><title>Cefore Home Page</title> <author /> <date /><title>Cefore</title> <author/> <date/> </front> </reference><!--<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.2119.xml"/> <referencegroup anchor="STD78" target="https://www.rfc-editor.org/info/std78"> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.5343.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.5590.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.5591.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6353.xml"/> </referencegroup>--></references> </references> <!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% --> <section anchor="sec.command"title="ccninfonumbered="true" toc="default"> <name>ccninfo Command andOptions">Options</name> <t> CCNinfo is implemented in Cefore <xreftarget="refs.ieice" format="default"/><xref target="refs.cefore"target="Cefore" format="default"/> <xref target="Cefore-site" format="default"/>. The command invoked by the CCNinfo user (e.g., consumer) is named "ccninfo". The ccninfo command sends the Request message and receives the Reply message(s). There are several options that can be specified with ccninfo, while the content name prefix (e.g., ccnx:/news/today) is the mandatory parameter.</t> <t>The usage of the ccninfo command is as follows:</t> <artwork name="" type="" align="left" alt=""><![CDATA[Usage:ccninfo [-c] [-f] [-o] [-V] [-r hop_count] [-s hop_count] [-valgo]algorithm] name_prefix ]]></artwork> <dl newline="true" spacing="normal" indent="3"><dt>name_prefix</dt><dt>name_prefix:</dt> <dd>PrefixThe prefix name of content (e.g., ccnx:/news/today) or exact name of content (e.g., ccnx:/news/today/Chunk=10) the CCNinfo user wants to trace.</dd></dl> <dl newline="true" spacing="normal" indent="3"><dt>coption</dt>option:</dt> <dd> This option can be specified if a CCNinfo user needs the cache information as well as the routing path information for the specified content/cache and RTT between the CCNinfo user and content forwarder. </dd> <dt>foption</dt>option:</dt> <dd> This option enables the "full discovery request"; routers send CCNinfo Requests to multiple upstream faces based on their FIBs simultaneously. The CCNinfo user can then trace all possible forwarding paths. </dd> <dt>ooption</dt>option:</dt> <dd> This option enablesto tracethe tracing of the path to the content publisher. Each router along the path to the publisher inserts each Report block and forwards the Request message. It does not send Reply even if it caches the specified content. FHR that attaches the publisher (who has the complete set of content and is not a caching router) sends the Reply message. </dd> <dt>Voption</dt>option:</dt> <dd> This option requests the Reply sender to validate the Reply message with the Reply sender's signature. The Reply message will then include the CCNx ValidationPayload TLV. The validation algorithm is selected by the Reply sender. </dd> <dt>roption</dt>option:</dt> <dd>NumberThe number of traced routers. This value is set in the "HopLimit" field located in the fixed header of the Request. For example, when the CCNinfo user invokes theCCNinfoccninfo command with this option, such as "-r 3", only three routers along the path examine their path and cache information. </dd> <dt>soption</dt>option:</dt> <dd>NumberThe number of skipped routers. This value is set in the "SkipHop" field located in the Request block TLV. For example, when the CCNinfo user invokes theCCNinfoccninfo command with this option, such as "-s 3", three upstream routers along the path only forward the Request message but do not append their Report blocks in thehop- by-hophop-by-hop header and do not send Reply messages despite having the corresponding cache. </dd> <dt>voption</dt>option:</dt> <dd> This option enables the CCNinfo user to validate the Request message withhis/hertheir signature. The Request message will include the CCNx ValidationPayload TLV. The validation algorithm is specified by the CCNinfo user. </dd> </dl> </section> <!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% --><!--<sectionanchor="sec.history" title="Change History"> <t>-00: This document was created based on the previous "Contrace" document whose initial version had been publishednumbered="false" toc="default"> <name>Acknowledgements</name> <t>The authors would like to thank <contact fullname="Jérôme François"/>, <contact fullname="Erik Kline"/>, <contact fullname="Spyridon Mastorakis"/>, <contact fullname="Paulo Mendes"/>, <contact fullname="Ilya Moiseenko"/>, <contact fullname="David Oran"/>, and <contact fullname="Thierry Turletti"/> for their valuable comments and suggestions onOctober 31, 2016.</t> <t>-01: Lots of bug fixes from -00.</t> </section>-->this document.</t> </section> </back> <!-- [rfced] Throughout the text, the following terminology appears to be used inconsistently. Please review these occurrences and let us know if/how they may be made consistent. CCNinfo command vs. ccninfo command ([HA] Done with ccninfo command) Request and Reply vs. request-reply vs. Request/Reply ([HA] Done.) caching router vs. Caching router ([HA] Done except Figs.1 and 2 and their explanation) interests vs. Interests ([HA] Done with Interest except a few general "interest") node identifier vs. Node Identifier ([HA] Done with Node Identifier (as the field name) and node identifier (as the general term)) --> </rfc>