Delay-Tolerant Networking Research Group E. Birrane Internet-Draft V. Ramachandran Intended status: ExperimentalJohns Hopkins University Applied Physics La Expires: April 04, 2014 October 01, 2013 Delay Tolerant Network Management Protocol draft-irtf-dtnrg-dtnmp-00 Abstract This draft describes the Delay/Disruption Tolerant Network Management Protocol (DTNMP). The DTNMP provides monitoring and configuration features between managing devices and those managed devices operating on the far side of high-delay or high-disruption links. The protocol is designed to minimize the number of transmitted bytes, operate without sessions or (concurrent) two-way links, and to function autonomously when there is no timely contact with a network operator. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on April 04, 2014. Copyright Notice Copyright (c) 2013 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of Birrane & Ramachandran Expires April 04, 2014 [Page 1] Internet-Draft DTNMP October 2013 the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 3 1.2. Technical Notes . . . . . . . . . . . . . . . . . . . . . 4 1.3. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.3.1. Protocol Scope . . . . . . . . . . . . . . . . . . . 4 1.3.2. Specification Scope . . . . . . . . . . . . . . . . . 5 1.4. Requirements Language . . . . . . . . . . . . . . . . . . 5 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. System Model . . . . . . . . . . . . . . . . . . . . . . . . 7 3.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 7 3.2. Roles and Responsibilities . . . . . . . . . . . . . . . 8 3.3. Data Flows . . . . . . . . . . . . . . . . . . . . . . . 10 3.4. Control Flow by Role . . . . . . . . . . . . . . . . . . 11 3.4.1. Notation . . . . . . . . . . . . . . . . . . . . . . 11 3.4.2. Serialized Management . . . . . . . . . . . . . . . . 11 3.4.3. Multiplexed Management . . . . . . . . . . . . . . . 12 3.4.4. Data Fusion . . . . . . . . . . . . . . . . . . . . . 14 4. Component Model . . . . . . . . . . . . . . . . . . . . . . . 15 4.1. Data Representation . . . . . . . . . . . . . . . . . . . 15 4.1.1. Types . . . . . . . . . . . . . . . . . . . . . . . . 15 4.1.2. Categories . . . . . . . . . . . . . . . . . . . . . 15 4.1.3. Data Model . . . . . . . . . . . . . . . . . . . . . 16 4.2. Primitive Types . . . . . . . . . . . . . . . . . . . . . 16 4.2.1. Self-Delimiting Numeric Value (SDNV) . . . . . . . . 17 4.2.2. Timestamp (TS) . . . . . . . . . . . . . . . . . . . 17 4.2.3. Data Collections (DC) . . . . . . . . . . . . . . . . 17 4.3. Naming . . . . . . . . . . . . . . . . . . . . . . . . . 17 4.4. Special Types . . . . . . . . . . . . . . . . . . . . . . 21 4.4.1. MID Collections (MC) . . . . . . . . . . . . . . . . 21 4.4.2. Expressions (EXPR) . . . . . . . . . . . . . . . . . 21 4.4.3. Predicate (PRED) . . . . . . . . . . . . . . . . . . 22 5. Functional Specification . . . . . . . . . . . . . . . . . . 22 5.1. Message Group Format . . . . . . . . . . . . . . . . . . 22 5.2. Message Format . . . . . . . . . . . . . . . . . . . . . 23 5.3. Administrative Messages (0x00 - 0x07) . . . . . . . . . . 25 5.3.1. Register Agent (0x00) . . . . . . . . . . . . . . . . 25 5.3.2. Status Reporting Policy (0x01) . . . . . . . . . . . 26 5.3.3. Status Message (0x02) . . . . . . . . . . . . . . . . 26 5.4. Definition Messages (0x08 - 0x0F) . . . . . . . . . . . . 27 5.4.1. Define Custom Report (0x08) . . . . . . . . . . . . . 27 5.4.2. Define Computed Data (0x09) . . . . . . . . . . . . . 28 5.4.3. Define Macro (0x0A) . . . . . . . . . . . . . . . . . 28 5.5. Reporting Messages (0x10 - 0x17) . . . . . . . . . . . . 28 Birrane & Ramachandran Expires April 04, 2014 [Page 2] Internet-Draft DTNMP October 2013 5.5.1. Data List (0x10) . . . . . . . . . . . . . . . . . . 28 5.5.2. Data Definitions (0x11) . . . . . . . . . . . . . . . 29 5.5.3. Data Report (0x12) . . . . . . . . . . . . . . . . . 29 5.5.4. Production Schedule Report (0x13) . . . . . . . . . . 30 5.6. Control Messages (0x18 - 0x1F) - 0xFF) . . . . . . . . . 31 5.6.1. Periodic Production Message (0x18) . . . . . . . . . 31 5.6.2. Predicate Production Message (0x19) . . . . . . . . . 32 5.6.3. Perform Control (0x20) . . . . . . . . . . . . . . . 32 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 33 7. Security Considerations . . . . . . . . . . . . . . . . . . . 33 8. Normative References . . . . . . . . . . . . . . . . . . . . 33 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 34 1. Introduction This RFC presents the Delay/Disruption Tolerant Network Management Protocol (DTNMP) used to perform application-layer network management functions over Delay/Disruption Tolerant Networks (DTNs) [RFC4838]. 1.1. Overview A network management protocol defines the messages that implement management functions amongst managed and managing devices in a network. Management functions include the definition, production, and reporting of performance data, the application of administrative and security policy, and the configuration of behavior based on local time and state measurements. DTNs contain nodes whose communication links are characterized by signal propagation delays and/or transmission disruptions that make timely data exchange difficult or impossible. Protocols that rely on timely data exchange, such as those that rely on negotiated sessions or other synchronized acknowledgment, do not function in the DTN environment. The Internet approach of network management via closed- loop, synchronous messaging fits this pattern and, therefore, does not work when network disruptions increase in frequency and severity. While no protocol delivers data in the absence of a networking link, protocols that eliminate or drastically reduce overhead and end-point coordination require much smaller transmission windows and continue to function when confronted with large delays and disruptions in the network. DTNMP accomplishes the network management function using open-loop, intelligent-push, asynchronous mechanisms that better scale as link challenges scale. The protocol is designed to support five desirable properties: Intelligent Push of Information Birrane & Ramachandran Expires April 04, 2014 [Page 3] Internet-Draft DTNMP October 2013 The intelligent push of information eliminates the need for round- trip data exchange in the management protocol. This is a necessary consequence of operating in open-loop systems where reliable round-trip communication may not exist. DTNMP is designed to operate even in uni-directional networks. Small Message Sizes Smaller messages require smaller periods of viable transmission for communication, incur less re-transmission cost, and consume less resources when persistently stored en-route in the network. DTNMP minimizes the size of a message whenever practical, to include packing and unpacking binary data, variable-length fields, and pre-configured data definitions. Fine-grained, Flexible Data Identification Fine-grained identification allows data in the system to be explicitly addressed while flexible data identification allows users to define their own customized, addressed data collections. In both cases, the ability to define precisely the data required removes the need to query and transmit large data sets only to filter/downselect desired data at a receiving device. Asynchronous Operation DTNMP does not rely on session establishment or round-trip data exchange to perform network management functions. Wherever possible, the DTNMP is designed to be stateless. Where state is required, the DTNMP provides mechanisms to support transactions and graceful degredation when nodes in the network fail to synchronize on common definitions. Compatibility with Low-Latency Network Management Protocols DTNMP adopts an identifier approach compatible with the Managed Information Base (MIB) format used by Internet management protocols such as the Simple Network Management Protocol (SNMP), thus enabling management interfaces between DTNs and other types of networks. 1.2. Technical Notes All multi-byte values are assumed to be communicated in network-byte order. Bit-fields are specified in Little-Endian format with bit position 0 holding the least-significant bit (LSB). When illustrated in this manuscript, the LSB appears on the right. 1.3. Scope 1.3.1. Protocol Scope Birrane & Ramachandran Expires April 04, 2014 [Page 4] Internet-Draft DTNMP October 2013 The DTNMP provides data monitoring, administration, and configuration for applications operating above the data link layer of the OSI networking model. While the DTNMP may be configured to support the management of network layer protocols (such as the Internet Protocol and Bundle Protocol) it also uses these protocols stacks to encapsulate and communicate its own DTNMP messages. It is assumed that the protocols used to carry DTNMP messages provide addressing, confidentiality, integrity, security, fragmentation support and other network/session layer functions. 1.3.2. Specification Scope This document describes the format of the DTNMP messages exchanged amongst managing and managed devices in a DTN. This document further describes the rationale behind key design decisions to the extent that such a description informs the operational deployment and configuration of DTNMP implementations. This document does not address specific data configurations of DTNMP-enabled devices, nor does it discuss the interface between DTNMP and other management protocols, such as SNMP. 1.4. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119]. 2. Terminology This section identifies those terms critical to understanding the proper operation of the DTNMP. Whenever possible, these terms align in both word selection and meaning with their analogs from other management protocols. Actor A software service running on either managed or managing devices implementing an end-point in the DTNMP. Actors may implement the "Manager" role, "Agent" role, or both. Agent Role A role within the DTNMP, associated with a managed device, responsible for reporting performance data, enforcing administrative policies, and accepting/performing actions. Agents exchange information with DTNMP managers operating either on the same device or on a remote managing device. Application Data Model (ADM) Birrane & Ramachandran Expires April 04, 2014 [Page 5] Internet-Draft DTNMP October 2013 The set of predefined data definitions, reports, literals, operations, and controls given to a DTNMP actor to manage a particular application or protocol. DTNMP actors support multiple ADMs, one for each application/protocol being managed. Atomic Data Globally unique, managed data definitions, similar to those defined in a Management Information Base (MIB), whose definition does not change based on the configuration of a DTNMP actor. Atomic data comprise the "lingua franca" within the DTNMP. All messages in the protocol operate either directly on atomic data or on data derived from atomic data. Computed Data Data items that are computed dynamically by a DTNMP actor from some combination of Atomic Data and other Computed Data. Controls Operations that may be undertaken by a DTNMP actor to change the behavior, configuration, or state of an application managed by the DTNMP. Macros A named, ordered collection of controls. Managed Item Definition (MID) A parameterized structure used to uniquely identify all data and control definitions within the DTNMP. MIDs are a super- set of Object Identifiers (OIDs) and the mechanism by which the DTNMP maintains data compatibility with other management protocols. Manager A role within the DTNMP associated with a managing device responsible for configuring the behavior of, and receiving/ processing/visualizing information from, DTNMP agents. DTNMP managers also provide gateways to non-DTNMP management protocols as part of conditioning the data returned from agents. Managers interact with one or more agents located on the same device and/or on remote devices in the network. Report Birrane & Ramachandran Expires April 04, 2014 [Page 6] Internet-Draft DTNMP October 2013 A named, ordered collection of data items gathered by one or more DTNMP agents and provided to one or more DTNMP managers. Reports may contain atomic data, computed data, and other reports. Individual data within a report are not named; the report itself is named to reduce the size of the report message. 3. System Model 3.1. Overview DTNMP performs the core network management functions of configuration, performance reporting, control, and administration, as follows. Configuration The configuration function synchronizes definitions amongst DTNMP actors in the DTN. Managers and Agents must agree on what ADMs are supported by what nodes. Further, these Actors must agree on the definitions of customized information, such as data production schedules, report definitions, and state- based autonomous actions. Performance Reporting Since DTNMP operates asynchronously, performance *monitoring* is replaced by performance *reporting*. As there is no expectation of closed-loop control of a managed device across a delayed/disrupted link, the best action that a managing device can undertake is to collect and operate on whatever data is received by managed devices. Reporting the performance of a managed device involves the local collection of reports and the communication of those reports to appropriate managing devices. Control Part of the ADM for a supported application/protocol includes a list of controls/commands that may be run by a DTNMP actor based on local time or local state. Controls comprise the basic autonomy mechanism within the DTNMP. Administration The mappings amongst agents and managers within a network may be complex, especially in networks comprising multiple administrative domains. The administrative management function defines what managers may control what agents, for what types of information. Birrane & Ramachandran Expires April 04, 2014 [Page 7] Internet-Draft DTNMP October 2013 3.2. Roles and Responsibilities By definition, DTNMP agents reside on managed devices and DTNMP managers reside on managing devices. These roles naturally map to the transmit and receipt of various DTNMP messages. This section describes how each of these roles participate in the network management functions outlined in the prior section. Agent Responsibilities Local Data Collection Agents MUST collect and report the data defined in all ADMs for which they have been configured for the local managed device. Agents MAY also collect data for network nodes that do not have their own DTNMP agents. In this scenario, the DTNMP agent acts as a proxy agent. Autonomous Control Agents MUST determine, without manager intervention, whether a configured control should be invoked. Agents MUST periodically evaluate the conditions associated with configured controls and invoke those controls based on local state. Agents MAY also invoke controls on other devices within a regional, low-latency network. Data Conditioning DTNMP agents MUST accept computed data definitions that specify how a single data value may be constructed from the transformation of one or more other data values in the system, using the expression syntax specified in this manuscript. Further, agents MUST produce this data when requested by Managers with the appropriate security persmissions. Agents MUST produce the list of computer data definitions when requested by a Manager. Agents MUST detect when a computed data definition references other data definitions that are unknown to the agent and respond in a way consistent with the logging/error-handling configuration of the agent. Report Definition Agents MUST support the ability to accept and store definitions for custom report definitions. Agents MUST conform to the security policies associated with custom reports when determining if a Manager may request a report defined by a different Manager in Birrane & Ramachandran Expires April 04, 2014 [Page 8] Internet-Draft DTNMP October 2013 the network. Agents MUST provide a listing of custom report definitions to appropriate managing devices when requested. Agents MUST detect requests for custom reports that are not configured on the agent, or are not appropriate for the requesting Manager, and respond in a way consistent with the logging/ error-handling configuration of the agent. Consolidate Messages Agents SHOULD produce as few messages as possible when sending information. For example, rather than sending multiple report messages to a manager, an agent SHOULD prefer to send a single message containing multiple reports. Regional Proxy Agents MAY perform any of their responsibilities on behalf of other network nodes that, themselves, do not have a DTNMP agent. In such a configuration, the DTNMP agent acts as a proxy agent for these other network nodes. Manager Responsibilities Agent/ADM Mapping Managers MUST understand what ADMs are supported by the various agents with which they communicate. Managers SHOULD NOT attempt to request, invoke, or refer to ADM information for ADMs unsupported by an agent. Data Collection Managers MUST receive information from agents by asynchronously configuring the production of data reports and then waiting for, and collecting, responses from agents over time. Managers SHOULD implement internal time-outs to detect conditions where agent information has not been received within network-specific timespans. Custom Definitions Managers SHOULD provide the ability to define custom data and report definitions. Any defined custom definitions MUST be transmitted to appropriate agents and these definitions MUST be remembered to interpret the reporting of these custom values from an agent in the future. Birrane & Ramachandran Expires April 04, 2014 [Page 9] Internet-Draft DTNMP October 2013 Data Translation Managers SHOULD provide some interface to other network management protocols, such as the SNMP. Managers MAY accomplish this by accumulating a repository of push-data from high-latency parts of the network from which data may be pulled by low- latency parts of the network. Data Fusion Managers MAY support the fusion of data from multiple agents with the purpose of transmitting fused data results to other managers within the network. Managers MAY receive fused reports from other managers pursuant to appropriate security and administrative configurations. 3.3. Data Flows We identify three significant data flows within the DTNMP: control flows from managers to agents, reports flows from agents to managers, and fusion reports from managers to other managers. These data flows are illustrated in Figure 1. DTNMP Data Flows +---------+ +------------------------+ +---------+ | Node A | | Node B | | Node C | | | | | | | |+-------+| |+-------+ +-------+| |+-------+| || ||=====>>|| DTNMP |====>>| DTNMP ||====>>|| || || ||<<=====|| Mgr B |<<====|Agent B||<<====|| || || DTNMP || |+--++---+ +-------+| || DTNMP || || Agent || +---||-------------------+ || Mgr C || || A || || || || || ||<<=========||==========================|| || || ||===========++========================>>|| || |+-------+| |+-------+| +---------+ +---------+ Figure 1 In this data flow, the agent on node A receives configurations from managers on nodes B and C, and replies with reports back to these managers. Similarly, the agent on node B interacts with the local manager on node B and the remote manager on node C. Finally, the manager on node B may fuse data reports received from agents at nodes A and B and send these fused reports back to the manager on node C. Birrane & Ramachandran Expires April 04, 2014 [Page 10] Internet-Draft DTNMP October 2013 From this figure, we see many-to-many relationships amongst managers, amongst agents, and between agents and managers. Note that agents and managers are roles, not necessarily differing software applications. Node A may represent a single software application fulfilling only the agent role, whereas node B may have a single software application fulfilling both the agent and manager roles. The specifics of how these roles are realized is an implementation matter. 3.4. Control Flow by Role This section describes three common configurations of DTNMP agents and managers and the flow of messages between them. These configurations involve local and remote management and data fusion. 3.4.1. Notation The notation outlined in Table 1 describes the types of control messages exchanged between DTNMP agents and managers. +----------------+---------------------------------+----------------+ | Term | Definition | Example | +----------------+---------------------------------+----------------+ | AD# | Atomic data definition, from | AD1 | | | ADM. | | | CD# | Custom data definition. | CD1 = AD1 + | | | | CD0. | | DEF([ACL], | Define id from expression. | DEF([*], CD1, | | ID,EXPR) | Allow managers in access | AD1 + AD2) | | | control list (ACL) to request | | | | this id. | | | PROD(P,ID) | Produce ID according to | PROD(1s, AD1) | | | predicate P. P may be a time | | | | period (1s) or an expression | | | | (AD1 > 10). | | | RPT(ID) | A report identified by ID. | RPT(AD1) | +----------------+---------------------------------+----------------+ Table 1: Terminology 3.4.2. Serialized Management This is a nominal configuration of network management where a managing device interacts with a set of managed devices, with a DTNMP manager installed on the managing device and a DTNMP agent installed on each managed device. The control flows for this are outlined in Figure 2. Birrane & Ramachandran Expires April 04, 2014 [Page 11] Internet-Draft DTNMP October 2013 Serialized Management Control Flow +----------+ +---------+ +---------+ | Manager | | Agent A | | Agent B | +----+-----+ +----+----+ +----+----+ | | | |-----PROD(1s, AD1)---->| |(Step 1) |----------------------------PROD(1s, AD1)--->| | | | | | | |<-------RPT(AD1)-------| |(Step 2) |<-----------------------------RPT(AD1)-------| | | | | | | |<-------RPT(AD1)-------| | |<-----------------------------RPT(AD1)-------| | | | | | | |<-------RPT(AD1)-------| | |<-----------------------------RPT(AD1)-------| | | | In a simple network, a manager interacts with multiple agents. Figure 2 In this figure, the manager configures agents A and B to produce atomic data AD1 every second in (Step 1). At some point in the future, upon receiving and configuring this message, agents A and B then build a report containing AD1 and send those reports back to the manager in (Step 2). 3.4.3. Multiplexed Management Networks spanning multiple administrative domains may require multiple managing devices (for example, one per domain). When a manager defines custom reports/data to an agent, that definition may be tagged with an access control list (ACL) to limit what other managers will be privy to this information. Managers in such networks SHOULD synchronize with those other managers granted access to their custom data definitions. When agents generate messages, they MUST only send messages to managers according to these ACLs, if present. The control flows in this scenario are outlined in Figure 3. Multiplexed Management Control Flow Birrane & Ramachandran Expires April 04, 2014 [Page 12] Internet-Draft DTNMP October 2013 +-----------+ +-------+ +-----------+ | Manager A | | Agent | | Manager B | +-----+-----+ +---+---+ +-----+-----+ | | | |--DEF(A,CD1,AD1*2)--->|<--DEF(B, CD2, AD2*2)-|(Step 1) | | | |---PROD(1s, CD1)----->|<---PROD(1s, CD2)-----|(Step 2) | | | |<-------RPT(CD1)------| |(Step 3) | |--------RPT(CD2)----->| |<-------RPT(CD1)------| | | |--------RPT(CD2)----->| | | | | |<---PROD(1s, CD1)-----|(Step 4) | | | | |--ERR(CD1 no perm.)-->| | | | |--DEF(*,CD3,AD3*3)--->| |(Step 5) | | | |---PROD(1s, CD3)----->| |(Step 6) | | | | |<---PROD(1s, CD3)-----| | | | |<-------RPT(CD3)------|--------RPT(CD3)----->|(Step 7) |<-------RPT(CD1)------| | | |--------RPT(CD2)----->| |<-------RPT(CD3)------|--------RPT(CD3)----->| |<-------RPT(CD1)------| | | |--------RPT(CD2)----->| Complex networks require multiple managers interfacing with agents. Figure 3 In more complex networks, managers may choose to define custom reports and data definitions, and agents may need to accept such definitions from multiple managers. Custom data definitions may include an ACL that describes who may query and otherwise understand the custom definition. In (Step 1), Manager A defines CD1 only for A while Manager B defines CD2 only for B. Managers may, then, request the production of reports containing these custom definitions, as shown in (Step 2). Agents produce different data for different managers in accordance with configured production rules, as shown in (Step 3). If a manager requests an operation, such as a production rule, for a custom data definition for which the manager has no permissions, a response consistent with the configured logging policy on the agent should be implemented, as shown in (Step 4). Alternatively, as shown in (Step 5), a manager may define custom data Birrane & Ramachandran Expires April 04, 2014 [Page 13] Internet-Draft DTNMP October 2013 with no restrictions allowing all other managers to request and use this definition. This allows all managers to request the production of reports containing this definition, shown in (Step 6) and have all managers receive this and other data going forward, as shown in (Step 7). 3.4.4. Data Fusion In many networks, agents do not want to individually transmit their data to a manager, preferring instead to fuse reporting data with local nodes prior to transmission. This approach reduces the number and size of messages in the network and reduces overall transmission energy expenditure. DTNMP supports fusion of NM reports by co- locating agents and managers on managed devices and offloading fusion activities to the manager. This process is illustrated in Figure 4. Data Fusion Control Flow +-----------+ +-----------+ +---------+ +---------+ | Manager A | | Manager B | | Agent B | | Agent C | +---+-------+ +-----+-----+ +----+----+ +----+----+ | | | | |--DEF(A,CD0,AD1+AD2)->| | |(Step 1) |--PROD(AD1&AD2, CD0)->| | | | | | | | |--PROD(1s,AD1)-->| |(Step 2) | |-------------------PROD(1s, AD2)->| | | | | | |<---RPT(AD1)-----| |(Step 3) | |<-------------------RPT(AD2)------| | | | | |<-----RPT(A,CD0)------| | |(Step 4) | | | | Data fusion in DTNMP accours amongst managers in the network. Figure 4 In this example, Manager A requires the production of a computed data set, CD0, from node B, as shown in (Step 1). The manager role understands what data is available from what agents in the subnetwork local to B, understanding that AD1 is available locally and AD2 is available remotely. Production messages are produced in (Step 2) and data collected in (Step 3). This allows the manager at node B to fuse the collected data reports into CD0 and return it in (Step 4). While a trivial example, the mechanism of associating fusion with the manager function rather than the agent function scales with fusion complexity, though it is important to reiterate that agent and Birrane & Ramachandran Expires April 04, 2014 [Page 14] Internet-Draft DTNMP October 2013 manager designations are roles, not individual software components. There may be a single software application running on node B implementing both Manager B and Agent B roles. 4. Component Model This section identifies the components that comprise the data communicated within the DTNMP, the way in which these components are named, and those special types associated with DTNMP messages. 4.1. Data Representation 4.1.1. Types Components within the DTNMP are represented as one of four basic data types: Data, Controls, Literals, and Operators: Data Data consist of values collected by an agent and reported to managers within the DTNMP. This includes definitions from an ADM, derived data as configured from managers, and reports which are collections of data elements. Controls Controls consist of actions that may be invoked on agents and managers to change behavior in response to some external event (such as local state changes or time). Controls include application-specific functions specified as part of an ADM and macros which are collections of these controls. Literals Literals are constant numerical values that may be used in the evaluation of expressions and predicates. Operator Operators are those mathematical functions that operate on series of Data and Literals, such as addition, subtraction, multiplication, and division. 4.1.2. Categories Components within the DTNMP can be categorized as Atomic, Computed, or Collection. Atomic Atomic components are those components that are directly implemented by the underlying software/firmware of a network node. Atomic components may also refer to components whose definitions may not be changed. Examples of atomic components are Data, Controls, Literals, and Operators specified by an ADM. Atomic component identifiers MUST be unique and SHOULD be managed by a registration authority, Birrane & Ramachandran Expires April 04, 2014 [Page 15] Internet-Draft DTNMP October 2013 similar to the mechanisms used to assign Object Identifiers (OIDs). Atomic components must be understood by both DTNMP managers and agents in a network. Computed Computed components are those components that are not directly implemented by the underlying software/firmware of a network node. The definition of a computed component MAY be dynamically defined by DTNMP managers and communicated to one or more DTNMP agents in a network. The definition of a computed component may include other computed components or other atomic components. The identifier of a computed component is not guaranteed to be universally unique but SHOULD be unique within the context of a particular network or internetwork. Collection A collection component is a set of other components (to include other collection components). DTNMP implementations MUST prevent circular definitions when implementing collections that include other collections. 4.1.3. Data Model Each component of the DTNMP data model can be identified as a combination of type and category, as illustrated in Table 2. In this table type/catgory combinations that are unsupported are listed as N/ A. Specifically, DTNMP does not support user-defined controls, constants, or operations; any value that specifies action on an agent MUST be pre-configured as part of an ADM. +------------+------------------+----------+----------+----------+ | | Data | Controls | Literals | Operator | +------------+------------------+----------+----------+----------+ | Atomic | Measured Value | Control | Constant | Operator | | Computed | Calculated Value | N/A | N/A | N/A | | Collection | Report | Macro | N/A | N/A | +------------+------------------+----------+----------+----------+ Table 2 4.2. Primitive Types Birrane & Ramachandran Expires April 04, 2014 [Page 16] Internet-Draft DTNMP October 2013 4.2.1. Self-Delimiting Numeric Value (SDNV) The data type "SDNV" refers to a Self-Delimiting Numerical Value (SDNV) described in [RFC6256]. SDNVs are used in the DTNMP to capture any data items that are expected to be 8 bytes or less in total length. DTNMP actors MAY reject any SDNV value that is greater than 8 bytes in length. 4.2.2. Timestamp (TS) For compatibility with a variety of protocols, the use of UTC time is selected to represent all time values in the DTNMP. However, timestamps in DTNMP may represent either absolute or relative time based on the associated epoch. DTNMP uses September 9th, 2012 as the timestamp epoch (UTC time 1348025776). Values less than this value MUST be considered as relative times. Values greater than or equal to this epoch MUST be considered as absolute times. In all cases, the DTNMP timestamp is encoded as an SDNV. 4.2.3. Data Collections (DC) A Data collection is comprised of a value identifiying the number of bytes in the collection, followed by each byte, as illustrated in Figure 5. Data collections are used in the DTNMP to capture variable data sets that are too large to place in an SDNV. Data Collection +---------+--------+--------+ +--------+ | # Bytes | BYTE 1 | BYTE 2 | ... | BYTE N | | [SDNV] | [BYTE] | [BYTE] | | [BYTE] | +---------+--------+--------+ +--------+ Figure 5 4.3. Naming All components within the DTNMP are identified using a Managed Identifier (MID). A MID is a variable-length structure that encapsulates an Object Identifier (OID) and augments it with information about the type and category of the component being identified and, optionally, information about who defined it. The MID structure, illustrated in Figure 6, is comprised of up to four fields. In this illustration, each field is named, the type of each field is given in []'s, and the string "(opt.)" indicates that the field is optional, pending on the values found in the flags bytes. Birrane & Ramachandran Expires April 04, 2014 [Page 17] Internet-Draft DTNMP October 2013 MID format +--------+--------+--------+--------+ | Flags | Issuer | OID | Tag | | [BYTE] | [SDNV] |[VARIED]| [SDNV] | | | (opt.) | | (opt.) | +--------+--------+--------+--------+ Figure 6 The MID fields are defined as follows. Flags Flags are used to describe the type of component identified by the MID, identify which optional fields in the MID are present, and the encoding used to capture the component's OID. The layout of the flag byte is illustrated in Figure 7. MID Flag Format +-----+---+---+-----+------+ | OID |TAG|ISS| CAT | TYPE | +-----+---+---+-----+------+ | 7 6 | 5 | 4 | 3 2 | 1 0 | +-----+---+---+-----+------+ MSB LSB Figure 7 MID Type (TYPE) The type of the component encapsulated by the MID, enumerated as data (0), control (1), literal (2), or operator (3). MID Category (CAT) The category of the component encapsulated by the MID, enumerated as atomic (0), computed (1), and collection (2). Issuer Present (ISS) Whether the issuer field is present (1) or not (0) for this MID. If this flag has a value of 1 then the issuer field MUST be present in the MID. Otherwise, the issuer field MUST NOT be present in the MID. Tag Present (TAG) Whether the tag field is present (1) or not (0) for this MID. If this flag has a value of 1 then the tag Birrane & Ramachandran Expires April 04, 2014 [Page 18] Internet-Draft DTNMP October 2013 field MUST be present in the MID. Otherwise, the tag field MUST NOT be present. OID Type (OID) Whether the contained OID field represents an full OID (0), a parameterized OID (1), a compressed full OID (2), or a compressed, parameterized OID (3). For example, a MID flag byte of 0x00 indicates an atomic data value with no issuer or tag field encapsulating a full OID. A MID flag byte of 0x94 indicates a computed data value with an issuer field, but no tag field encapsulating a compressed OID. Issuer This is a binary identifier representing a predetermined issuer name. The DTNMP protocol does not parse or validate this identifier, using it only as a distinguishing bit pattern to assure MID uniqueness. This value, for example, may come from a global registry of organizations, an issuing node address, or some other network-unique marking. OID The core of a MID is its encapsulated Object Identifier (OID). Aside from the flag byte, this is the only other mandatory element within a MID. The DTNMP defines four types of OID references for this part of the MID structure: Full OIDs, Parameterized OIDs, Compressed Full OIDs, and Compressed Parameterized OIDs. Full OID This is a binary representation of the full OID associated with the named value. The OID is encoded using a modified form of the ASN.1 Basic Encoding Rules (BER) for Object Identifiers (type value of 0x06). In the standard ASN.1 encoding, four octet sets are defined: identifier octets, length octets, contents octets, and end-of-contents octets. A DTNMP Full OID does not use the identifier, length, or end- of-contents octets. Instead, a DTNMP Full OID is comprised of two fields: the length in bytes of the encoded OID captured in an SDNV followed by the OID contents octets, as illustrated in Figure 8. Full OID Format Birrane & Ramachandran Expires April 04, 2014 [Page 19] Internet-Draft DTNMP October 2013 +------------+--------------------+ | OID Length | OID Content Octets | | [SDNV] | [ASN.1 BER] | +------------+--------------------+ Figure 8 Parameterized OID The parameterized OID is represented as the non- parameterized portions of the OID followed by one or more parameters. Parameterized OIDs are used to templatize the specification of data items and otherwise provide parameters to controls without requiring potentially unmanagable growth of a Full OID namespace. The format of a parameterized OID is given in Figure 9. Parameterized OID Format +----------+---------+--------+ +--------+ | Base OID | # Parms | Parm 1 | ... | Parm N | | [VAR] | [SDNV] | [DC] | | [DC] | +----------+---------+--------+ +--------+ Figure 9 Compressed Full OID Since many related OIDs share a common and lengthy hierarchy there is opportunity for significant message size savings by defining a shorthand for commonly-used portions of the OID tree. A partial OID is a tuple consisting of a nickname for a pre- defined portion of the OID tree (as an SDNV), followed by a relative OID. Compressed Parameterized OID A compressed, parameterized OID is similar to a compressed OID. In this instance, the tuple contained in this field is the nickname for the pre- defined portion of the OID tree (as an SDNV) followed by a parameterized OID whose hierarchy begins at the place identified by the nickname. Tag A value used to disambiguate multiple MIDs with the same OID/ Issuer combination. The definition of the tag is left to the discretion of the MID issuer. Proper name objects do not require a tag as their OIDs are guaranteed to be globally Birrane & Ramachandran Expires April 04, 2014 [Page 20] Internet-Draft DTNMP October 2013 unique. Options for tag values include an issuer-known version number or a hashing of the data associated with a non-proper-name MIDs. The tag field MUST NOT be present for the atomic category. 4.4. Special Types In addition to the primitive data types already mentioned, the following special data types are also defined. 4.4.1. MID Collections (MC) A MID collection is comprised of a value identifiying the number of MIDs in the collection, followed by each MID, as illustrated in Figure 10. MID Collection +--------+-------+ +-------+ | # MIDs | MID 1 | ... | MID N | | [SDNV] | [MID] | | [MID] | +--------+-------+ +-------+ Figure 10 4.4.2. Expressions (EXPR) Expressions apply operations to data and literal values to generate new data values. The expression type in DTNMP is a collection of MIDs that represent a postfix notation stack of Data, Literal, and Operation types. For example, the infix expression A * (B * C) is represented as the sequence A B C * *. The format of an expression is illustrated in Figure 11. Expression Format +----------+------------+ | Priority | Expression | | [SDNV] | [MC] | +----------+------------+ Figure 11 Priority The priority of this expression relative to any other expression configured on the DTNMP actor. Priorities are used when one expression MUST be evaluated before some other expression is evaluated. This field represents an unsigned Birrane & Ramachandran Expires April 04, 2014 [Page 21] Internet-Draft DTNMP October 2013 integer value with larger values indicating higher priority. Unless otherwise specified, a default priority value of 0 SHALL be used for any defined expression. Expression An expression is represented in the DTNMP as a MID collection, where each MID in the ordered collection represents the data, literals, and operations that comprise the expression. 4.4.3. Predicate (PRED) Predicates are expressions whose values are interpretted as a Boolean. The value of zero MUST be considered "false" and all other values MUST be considered "true". Similar to an expression, a predicate is represented as a MID collection. 5. Functional Specification This section describes the format of the messages that comprise the DTNMP protocol. When discussing the format/types of data that comprise message fields, the following conventions are used. +-----------+---------------------------------+ | Type Name | Description | +-----------+---------------------------------+ | BYTE | Unsigned, 8-bit byte. | | DC | Data Collection | | EXPR | Expression | | MC | MID Collection | | MID | Managed Identifier | | PRED | Predicate | | SDNV | Self-Delimiting Numerical Value | | TS | Timestamp | | VAR | Variable field. | +-----------+---------------------------------+ 5.1. Message Group Format Individual messages within the DTNMP are combined into a single group for communication with another DTNMP actor. Messages within a group MUST be received and applied as an atomic unit. The format of a message group is illustrated in Figure 12. These message groups are assumed communicated amongst agents and managers as the payloads of encapsulating protocols, such as the Bundle Protocol or Internet Protocol, which MAY provide additional security and data integrity features. Birrane & Ramachandran Expires April 04, 2014 [Page 22] Internet-Draft DTNMP October 2013 DTNMP Message Group Format +--------+-----------+-----------+ +-----------+ | # Msgs | Timestamp | Message 1 | ... | Message N | | [SDNV] | [TS] | [VAR] | | [VAR] | +--------+-----------+-----------+ +-----------+ Figure 12 # Msgs The number of messages that are together in this message group. Timestamp The creation time for this messaging group. This timestamp MUST be an absolute time. Individual messages may have their own creation timestamps based on their type, but the group timestamp also serves as the default creation timestamp for every message in the group. Message N The Nth message in the group. 5.2. Message Format Each message identified in the DTNMP specification adheres to a common message format, illustrated in Figure 13, consisting of a message header, a message body, and an optional trailer. DTNMP Message Format +--------+-------+---------+ | Header | Body | Trailer | | [BYTE] | [VAR] | [VAR] | | | | (opt.) | +--------+-------+---------+ Figure 13 Birrane & Ramachandran Expires April 04, 2014 [Page 23] Internet-Draft DTNMP October 2013 +-----------------+-------+-------+ | Message Context | Bit 0 | Bit 1 | +-----------------+-------+-------+ | Administrative | 0 | 0 | | Definition | 0 | 1 | | Reporting | 1 | 0 | | Control | 1 | 1 | +-----------------+-------+-------+ Table 3: Message Type Allocations Header The message header byte is shown in Figure 14. The header identifies a message context and opcode as well as flags that control whether a report should be generated on message success (Ack) and whether a report should be generated on message failure (Nack). DTNMP Common Message Header +--------+----+---+---------+-------+ |ACL Used|Nack|Ack| Context |Opcode | +--------+----+---+---------+-------+ | 7 | 6 | 5 | 4 3 | 2 1 0 | +--------+----+---+---------+-------+ MSB LSB Figure 14 Opcode The opcode field identifies the opcode of the message, within the associated message context. Context The context field segments messages into one of four logical groupings, as listed in Table 3. ACK Flag The ACK flag describes whether successfull application of the message must generate an ackowledgement back to the message sender. If this flag is set (1) then the receiving actor MUST generate a report communicating this status. Otherwise, the actor MAY generate such a report based on other criteria. NACK Flag Birrane & Ramachandran Expires April 04, 2014 [Page 24] Internet-Draft DTNMP October 2013 The NACK flag describes whether a failure applying the message must generate an error notice back to the message sender. If this flag is set (1) then the receiving actor MUST generate a report communicating this status. Otherwise, the actor MAY generate such a report based on other criteria. ACL Used Flag The ACL used flag indicates whether the message has a trailer associated with it that specifies the list of DTNMP actors that may participate in the actions or definitions associated with the message. This area is still under development. Body The message body contains the information associated with the given message. Trailer An OPTIONAL access control list (ACL) may be appended as a trailer to a message. When present, the ACL for a message identifiers the agents and managers that can be affected by the definitions and actions contained within the message. The explicit impact of an ACL is described in the context of each message below. When an ACL trailer is not present, the message results may be visible to any DTNMP actor in the network, pursuant to other security protocol implementations. 5.3. Administrative Messages (0x00 - 0x07) Administrative messages configure the exchange of information amongst agents and managers in the DTNMP. Additionally, they are used to report on the operation and state of the agent and manager. 5.3.1. Register Agent (0x00) The Register Agent message is used to inform a DTNMP manager of the presence of another agent in the network. +----------+ | Agent ID | | [SDNV] | +----------+ Figure 15: Register Agent Message Body Agent ID Birrane & Ramachandran Expires April 04, 2014 [Page 25] Internet-Draft DTNMP October 2013 The Agent ID MUST represent the unique address of the agent in whatever protocol is used to communicate with the agent. For example, when DTNMP is run over Bundle Protocol, the Agent ID should be the Endpoint Identifier (EID) of the agent being added. 5.3.2. Status Reporting Policy (0x01) Agents and managers in the network may periodically emit logging messages based on protocol-level events. The logging policy configures each DTNMP actor to produce or suppress messages in the network. +--------+ | MASK | | [BYTE] | +--------+ Figure 16: Reporting Policy Message Body Mask This bitmask identifies which types of administrative log messages should be produced by the DTNMP actor. If a bit in the mask is set, the log message associated with the bit MUST be produced by the actor. +----------+-------+-------+-------+-------+ | Reserved | Log | Error | Warn | Alert | +----------+-------+-------+-------+-------+ | 7 6 5 4 | 3 | 2 | 1 | 0 | +----------+-------+-------+-------+-------+ MSB LSB Figure 17 5.3.3. Status Message (0x02) Status messages are sent in response to local alerts, warnings, and errors that occur at a DTNMP actor. The messages may include a body field, the presence and format of which is indicated by the status code. +------+------+------------+ | Code | Time | Generators | |[MID] | [TS] | [MC] | +------+------+------------+ Figure 18 Birrane & Ramachandran Expires April 04, 2014 [Page 26] Internet-Draft DTNMP October 2013 Code This field is a literal data type identifying the type of status being communicated. Status codes are defined as constants within the ADMs for various protocols and applications, to include those status codes defined in a DTNMP ADM. Time The timestamp identifying when the status message was generated. This single timestamp holds for all status messages in the message. Generators The collection of MIDs that caused the generation of the error code. For example, if the error code specifies an unknown MID encountered while processing a computed data definition, then the generator could be the MID identifying the computed data element. 5.4. Definition Messages (0x08 - 0x0F) Definition messages establish new identifiers on DTNMP actors that define new information not already pre-configured as part of supported ADMs. These definitions include computed data, report definitions, and macros. 5.4.1. Define Custom Report (0x08) A custom report assigns a single MID value to represent an ordered collection of other MID values, with some administrative information that identifies what other nodes in the network may request and process this report. Custom Report Definition +-----------+------------+ | Report ID | Contents | | [MID] | [MC] | +-----------+------------+ Figure 19 Report ID The MID value identifying the custom report. Contents The contents of a report defintion as the ordered collection of MIDs that comprise the report. Birrane & Ramachandran Expires April 04, 2014 [Page 27] Internet-Draft DTNMP October 2013 5.4.2. Define Computed Data (0x09) A computed data item uses an expression to assign a data value. Computed Data Definition +--------+------------+ | New ID | Expression | | [MID] | [EXPR] | +--------+------------+ Figure 20 New ID The MID value identifying the computed data object. Expression The expression used to calculate the value of this data item. 5.4.3. Define Macro (0x0A) A macro is a series of controls that should be run in sequence. Macro Definition +--------+------------+ | New ID | Controls | | [MID] | [MC] | +--------+------------+ Figure 21 New ID The MID value identifying the macro. Controls The series of controls that are run sequentially as part of the macro. 5.5. Reporting Messages (0x10 - 0x17) Reporting messages are those message generated by DTNMP agents representing state on a managed device. 5.5.1. Data List (0x10) This message lists one or more configured data items on the producing DTNMP actor for which the requesting actor has access permissions. Birrane & Ramachandran Expires April 04, 2014 [Page 28] Internet-Draft DTNMP October 2013 +---------------+ | Configured ID | | [MC] | +---------------+ Figure 22 Configured ID The list of MIDs representing computed data defined on the actor for which the requesting actor has access permissions. The individual MIDs identify the associated types of data. 5.5.2. Data Definitions (0x11) This message contains a list of one or more configured item definitions on the producing DTNMP actor and accessible to the requesting actor. +--------+------+----------+ +------+----------+ | # Defs | ID 1 | Def 1 | ... | ID N | Def N | | [SDNV] |[MID] | [MC] | |[MID] | [MC] | +--------+------+----------+ +------+----------+ Figure 23 # Definitions The number of definitions included in this report. ID N The MID identifier of the Nth definition in the message. The MID is used to contain the data type. Definition N The definition of the Nth item. For computed data this is an expression. For macros, this is a MID list of controls. For reports, this is a MID list of data and other reports. 5.5.3. Data Report (0x12) Data reports include a listing of one or more data items collected from a managed device. These reports may include atomic data, computed data, or any report definition known to the generating device. Each message is a concatenation of ID/Data definitions with the overall message length assumed to be captured in the underlying transport container. +------+------+-----+------+-------+ +-----+------+-------+ | Time | Num |ID 1 |Size 1|Data 1 | |ID N |Size N|Data N | Birrane & Ramachandran Expires April 04, 2014 [Page 29] Internet-Draft DTNMP October 2013 | [TS] |[SDNV]|[MID]|[SDNV]|[BYTES]|...|[MID]|[SDNV]|[BYTES]| +------+------+-----+------+-------+ +-----+------+-------+ Figure 24 Time The time at which the report was generated by the DTNMP actor. Num The number of reports in the data report message. ID N The MID identifying the Nth report. Size N The size of the Nth report. Data N The contents of the Nth report. 5.5.4. Production Schedule Report (0x13) This message contains a list of all production rules configured on the DTNMP actor that can be accessed by the querying actor. +---------+--------+ +--------+ | # Rules | Rule 1 | ... | Rule N | | [SDNV] | [VAR] | | [VAR] | +---------+--------+ +--------+ Figure 25 # Rules The number of production rules included in this report. Rule N The Nth rule report in the list. A rule report is as follows. +-------+-------+-----------+--------+---------+ | Type | Start | Condition | Count | Results | | [BYTE]| [TS] | [PRED/TS] | [SDNV] | [MC] | +-------+-------+-----------+--------+---------+ Figure 26 Type Birrane & Ramachandran Expires April 04, 2014 [Page 30] Internet-Draft DTNMP October 2013 The type of rule being reported. Currently a Time Rule (0) or a Predicate Rule (1) Start The start time for the production rule. If a relative time, then this is interpretted as relative to message receipt. Condition The condition which, when true, causes the report to be produced. If a Time Rule then this is interpretted as a period measured in seconds. If a Predicate Rule, then this is interpretted an a predicate. Count The number of times the rule can fire before being disabled. Results The collection of MIDs produced by this rule. 5.6. Control Messages (0x18 - 0x1F) - 0xFF) Control messages cause pre-configured, vetted commands on the DTNMP agents to be issued. 5.6.1. Periodic Production Message (0x18) The periodic production message instructs an agent to produce a set of MID values periodically over time. MID values may represent any type of data value, including atomic data, computed data, or reports. Periodic Production Message Body +--------+------------+--------+---------+ | Start | Period (s) | Count | Results | | [TS] | [SDNV] | [SDNV] | [MC] | +--------+------------+--------+---------+ Figure 27 Start The time at which the production should commence. Period The number of seconds to wait between report message generation. Birrane & Ramachandran Expires April 04, 2014 [Page 31] Internet-Draft DTNMP October 2013 Count The number of reports to be generated by this configuration. The special value of 0 indicates production should continue indefinitely. Results The collection of MIDs to be included in the report. 5.6.2. Predicate Production Message (0x19) The predicate production message instructs an agent to produce a set of MID values whenever some condition is true on the agent. Predicate Production Message +-------+-----------+--------+---------+ | Start | Predicate | Count | Results | | [TS] | [PRED] | [SDNV] | [MC] | +-------+-----------+--------+---------+ Figure 28 Start The time at which the production should commence. Predicate The predicate that must evaluate to generate this report. Count The number of reports to be generated by this configuration. The special value of 0 indicates production should continue indefinitely. Results The collection of MIDs to be included in the report. 5.6.3. Perform Control (0x20) The perform control method causes the receiving DTNMP actor to apply one or more pre-configured controls. Birrane & Ramachandran Expires April 04, 2014 [Page 32] Internet-Draft DTNMP October 2013 Predicate Production Message +-------+-----------+ | Start | Controls | | [TS] | [MC] | +-------+-----------+ Figure 29 Start The time at which the control should be run. Controls The collection of controls to be applied by the DTNMP actor. 6. IANA Considerations At this time, this protocol has no fields registered by IANA. 7. Security Considerations Transport security is handled by the transport layer, for example the Bundle Security Protocol [RFC6257] when using the Bundle Protocol [RFC5050]. Finer grain application security is done via ACLs which are defined via configuration messages and implementation specific. 8. Normative References [DTNM] Birrane, E. and H. Kruse, "DTN Network management: The Definition and Exchange of Infrastructure Information in High Delay Environments", . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC4838] Cerf, V., Burleigh, S., Hooke, A., Torgerson, L., Durst, R., Scott, K., Fall, K., and H. Weiss, "Delay-Tolerant Networking Architecture", RFC 4838, April 2007. [RFC5050] Scott, K. and S. Burleigh, "Bundle Protocol Specification", RFC 5050, November 2007. [RFC6256] Eddy, W. and E. Davies, "Using Self-Delimiting Numeric Values in Protocols", RFC 6256, May 2011. Birrane & Ramachandran Expires April 04, 2014 [Page 33] Internet-Draft DTNMP October 2013 [RFC6257] Symington, S., Farrell, S., Weiss, H., and P. Lovell, "Bundle Security Protocol Specification", RFC 6257, May 2011. [tolerance] Birrane, E., Burleigh, S., and V. Cerf, "Defining Tolerance: Impacts of Delay and Didruption when Managing Challenged Networks", 2001. Authors' Addresses Edward J. Birrane Johns Hopkins University Applied Physics Laboratory Email: Edward.Birrane@jhuapl.edu Vignesh Ramachandran Johns Hopkins University Applied Physics Laboratory Email: Vinny.Ramachandran@jhuapl.edu Birrane & Ramachandran Expires April 04, 2014 [Page 34]