Internet Engineering Task Force (IETF) P. Dawes
Request for Comments: 8497 Vodafone Group
Category: Standards Track C. Arunachalam
ISSN: 2070-1721 Cisco Systems
November 2018
Marking SIP Messages to Be Logged
Abstract
SIP networks use signaling monitoring tools to diagnose user-reported
problems and to perform regression testing if network or user agent
(UA) software is upgraded. As networks grow and become
interconnected, including connection via transit networks, it becomes
impractical to predict the path that SIP signaling will take between
user agents and therefore impractical to monitor SIP signaling end to
end.
This document describes an indicator for the SIP protocol that can be
used to mark signaling as being of interest to logging. Such marking
will typically be applied as part of network testing controlled by
the network operator and is not used in normal user agent signaling.
Operators of all networks on the signaling path can agree to carry
such marking end to end, including the originating and terminating
SIP user agents, even if a session originates and terminates in
different networks.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8497.
Copyright Notice
Copyright (c) 2018 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
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 4
3. "Log Me" Marking Protocol Aspects . . . . . . . . . . . . . . 4
3.1. Session-ID "logme" Parameter . . . . . . . . . . . . . . 4
3.2. Starting and Stopping Logging . . . . . . . . . . . . . . 4
3.3. Identifying Test Cases . . . . . . . . . . . . . . . . . 5
3.4. Passing the Marker . . . . . . . . . . . . . . . . . . . 6
3.4.1. To/From a User Device . . . . . . . . . . . . . . . . 6
3.4.2. To/From an External Network . . . . . . . . . . . . . 6
3.4.3. Across a Non-supporting SIP Intermediary . . . . . . 6
3.5. Logging Multiple Simultaneous Dialogs . . . . . . . . . . 6
3.6. Format of Logged Signaling . . . . . . . . . . . . . . . 6
3.7. Marking Related Dialogs . . . . . . . . . . . . . . . . . 7
3.8. Forked Requests . . . . . . . . . . . . . . . . . . . . . 11
4. SIP Entity Behavior . . . . . . . . . . . . . . . . . . . . . 11
4.1. Scope of Marking . . . . . . . . . . . . . . . . . . . . 11
4.2. Endpoints . . . . . . . . . . . . . . . . . . . . . . . . 12
4.3. SIP Intermediaries Acting on Behalf of Endpoints . . . . 13
4.4. B2BUAs . . . . . . . . . . . . . . . . . . . . . . . . . 15
4.5. "Log Me" Marker Processing by SIP Intermediaries . . . . 15
4.5.1. Stateless Processing . . . . . . . . . . . . . . . . 15
4.5.2. Stateful Processing . . . . . . . . . . . . . . . . . 16
4.5.2.1. "Log Me" Marking Not Supported by Originating UA 17
4.5.2.2. "Log Me" Marking Not Supported by Terminating UA 19
4.5.2.3. "Log Me" Marking Removed by Originating Network . 21
4.5.2.4. "Log Me" Marking Removed by Supporting
Terminating Network . . . . . . . . . . . . . . . 23
4.5.2.5. "Log Me" Marking Passed by Non-supporting
Terminating Network . . . . . . . . . . . . . . . 25
5. Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
5.1. Error Cases . . . . . . . . . . . . . . . . . . . . . . . 27
5.1.1. Missing "Log Me" Marker Error Case . . . . . . . . . 27
5.1.2. "Log Me" Marker Appears Mid-dialog Error Case . . . . 31
5.2. Non-error Cases . . . . . . . . . . . . . . . . . . . . . 32
5.2.1. Missing "Log Me" Marker Non-error Case . . . . . . . 32
5.2.2. "Log Me" Marker Appears Mid-dialog Non-error Case . . 33
5.2.3. Combining Dialogs Non-error Case . . . . . . . . . . 34
5.3. Error Handling . . . . . . . . . . . . . . . . . . . . . 34
6. Augmented BNF for the "logme" Parameter . . . . . . . . . . . 35
7. Security Considerations . . . . . . . . . . . . . . . . . . . 35
7.1. "Log Me" Authorization . . . . . . . . . . . . . . . . . 35
7.2. "Log Me" Marker Removal . . . . . . . . . . . . . . . . . 36
7.3. Denial-of-Service Attacks . . . . . . . . . . . . . . . . 36
7.4. Data Protection . . . . . . . . . . . . . . . . . . . . . 36
8. Privacy Considerations . . . . . . . . . . . . . . . . . . . 36
8.1. Personal Identifiers . . . . . . . . . . . . . . . . . . 37
8.2. Data Stored at SIP Intermediaries . . . . . . . . . . . . 37
8.3. Data Visible at Network Elements . . . . . . . . . . . . 38
8.4. Preventing Fingerprinting . . . . . . . . . . . . . . . . 38
8.5. Retaining Logs . . . . . . . . . . . . . . . . . . . . . 38
8.6. User Control of Logging . . . . . . . . . . . . . . . . . 39
8.7. Recommended Defaults . . . . . . . . . . . . . . . . . . 39
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 39
9.1. Registration of the "logme" Parameter . . . . . . . . . . 39
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 40
10.1. Normative References . . . . . . . . . . . . . . . . . . 40
10.2. Informative References . . . . . . . . . . . . . . . . . 41
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 42
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 42
1. Introduction
When users experience problems with setting up sessions using SIP,
enterprise or service provider network operators often have to
identify the root cause by examining the SIP signaling. Also, when
network or user agent (UA) software or hardware is upgraded,
regression testing is needed. Such diagnostics apply to a small
proportion of network traffic and can apply end to end, even if
signaling crosses several networks possibly belonging to several
different network operators. It may not be possible to predict the
path through those networks in advance, therefore, a mechanism is
needed to mark a session as being of interest so that SIP entities
along the signaling path can provide diagnostic logging. [RFC8123]
illustrates this motivating scenario. This document describes a
solution that meets the requirements for such "log me" marking of SIP
signaling also defined in [RFC8123].
This document also defines a new header field parameter, "logme", for
the Session-ID header field [RFC7989]. Implementations of this
document MUST implement [RFC7989].
2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. "Log Me" Marking Protocol Aspects
3.1. Session-ID "logme" Parameter
Logging for diagnostic purposes is most effective when it is applied
end to end in a communication session. This ability requires a "log
me" marker to be passed through SIP intermediaries. The Session-ID
header field defined in [RFC7989] was chosen to carry the "log me"
marker as a "logme" parameter since the session identifier is
typically passed through SIP Back-to-Back User Agents (B2BUAs)
(described in [RFC7092]) or other intermediaries, as per the Session-
ID requirement REQ3 in [RFC7206]. The "logme" parameter shown in
Figure 1 does not introduce any device-specific or user-specific
information and MUST be passed unchanged with the Session-ID header
field. There is an exception, however, for the cases specified in
Section 3.4.2 where the "log me" marker may be removed at a network
boundary.
Alice Proxy Registrar
u1.example.com p1.example.com r1.example.com
| | |
|(1) INVITE | |
| Session-ID: ab30317f1a784dc48ff824d0d3715d86;
| remote=47755a9de7794ba387653f2099600ef2;logme
|----------------->| |
| | |
Figure 1: "Log Me" Marking Using the "logme" Session-ID Header Field
Parameter
3.2. Starting and Stopping Logging
If a dialog is to be "log me" marked, then marking MUST start with
the SIP request that initiates that dialog (dialog-initiating
requests are described in Section 12.1 of [RFC3261]). For the most
effective testing and troubleshooting, marking continues for the
lifetime of the dialog, applies to each request and response in the
dialog, and applies uninterrupted end to end (including user
devices). The "log me" marking mechanism described in this document
allows for parts of the signaling path to not be marked, e.g, because
an endpoint does not support the "log me" marking mechanism (see
Section 4.5.2) or because an endpoint or intermediary deliberately
removes the "log me" marker (see Section 4.5.2.4). Also, marking
errors can terminate marking before the dialog ends (see
Section 5.3).
A UA or intermediary adds a "log me" marker in an unmarked request or
response in two cases: first, because it is configured to add the
marking to a dialog-creating request, or second, because it has
received a dialog-creating request that is being "log me" marked
causing it to maintain state to ensure that all requests and
responses in the dialog are similarly "log me" marked. Once the "log
me" marking is started for a dialog, all subsequent requests and
responses in this dialog are "log me" marked. Marking is stopped
when this dialog and its related dialogs end. It is considered an
error (see Section 5.1.2) if "log me" marking is started in a mid-
dialog request or response.
For the first case, "log me" marking trigger condition configurations
that define whether a UA or intermediary can initiate "log me"
marking for a given dialog are out of scope of this document. As an
example of trigger condition configurations, the UA or intermediary
could be configured to add a "log me" marker for all dialogs
initiated during a specific time period (e.g., 9:00 am - 10:00 am
every day) or for specific dialogs that have a particular "User-
Agent" header field value. They could also be configured to add a
"log me" marker for a specific set of called party numbers for which
users are experiencing call setup failures.
For the second case of a UA or intermediary detecting that a dialog-
initiating request is being "log me" marked, the scope of such
marking extends to the lifetime of the dialog. In addition, as
discussed in Section 3.7, "log me" marked dialogs that create related
dialogs (e.g., REFER) may transfer the marking to the related
dialogs. In such cases, the entire "session", identified by the
Session-ID header field, is "log me" marked.
3.3. Identifying Test Cases
The local Universally Unique Identifier (UUID) portion of the
Session-ID header field value [RFC7989] in the initial SIP request of
a dialog is used as a random test case identifier (described in REQ 5
in [RFC8123]). This provides the ability to collate all logged SIP
requests and responses to the initial SIP request in a dialog or
standalone transaction.
3.4. Passing the Marker
3.4.1. To/From a User Device
When a user device inserts the "log me" marker, the marker MUST be
passed unchanged in the Session-ID header field across an edge proxy
or a B2BUA adjacent to the user device.
3.4.2. To/From an External Network
An external network is a peer network connected at a network boundary
as defined in [RFC8123].
External networks may be connected directly or via a peering network,
and such networks often have specific connection agreements. Whether
"log me" marking is removed depends on the policy applied at the
network-to-network interface. Troubleshooting and testing will be
easier if peer networks endeavor to make agreements to pass "log me"
marking unchanged. However, since a "log me" marker may cause a SIP
entity to log the SIP header and body of a request or response, the
"log me" marker MUST be removed at a network boundary if no agreement
exists between peer networks.
3.4.3. Across a Non-supporting SIP Intermediary
"Log me" marking is most effective if passed end to end. However,
intermediaries that do not comply with this document might pass the
"log me" marker unchanged or even drop it entirely.
3.5. Logging Multiple Simultaneous Dialogs
Multiple SIP dialogs can be simultaneously logged by an originating
UA, terminating UA, and SIP entities on the signaling path. These
dialogs are differentiated by their test case identifier (the local
UUID portion of the Session-ID header field value at the originating
device).
3.6. Format of Logged Signaling
The entire SIP message (SIP request line, response line, header
fields, and message body) SHOULD be logged since troubleshooting
might be difficult if information is missing. Logging SHOULD use
common standard formats such as SIP Common Log Format (CLF) defined
in [RFC6873] and Libpcap as defined in "vnd.tcpdump.pcap" in the
Media Types registry [MEDIA-TYPES]. If SIP CLF is used, the entire
message is logged using Vendor-ID = 00000000 and Tag = 02 in the
<OptionalFields> portion of the SIP CLF record (see Section 4.4 of
[RFC6873]). Header fields SHOULD be logged in the form in which they
appear in the message; they SHOULD NOT be converted between long and
compact forms described in Section 7.3.3 of [RFC3261].
3.7. Marking Related Dialogs
"Log me" marking is done per dialog; typically, it begins at dialog
creation and ends when the dialog ends. However, dialogs related to
a "log me" marked dialog MAY also be "log me" marked for call control
features such as call forward, transfer, park, and join. As
described in Section 6 of [RFC7989], related dialogs can occur when
an endpoint receives a 3xx message, a REFER that directs the endpoint
to a different peer, an INVITE request with Replaces that also
potentially results in communicating with a new peer, or an INVITE
with a Join header field as described in [RFC3911]. An example is
the call transfer feature described in Section 6.1 of [RFC5589]. The
logged signaling for related dialogs can be correlated using Session-
ID header field values as described in Section 10.9 of [RFC7989].
In the example shown in Figure 2, Alice has reported problems making
call transfers. Her terminal is placed in debug mode in preparation
for "log me" marked signaling from the network administrator,
Bob. Bob's terminal is configured to "log me" mark and log signaling
for calls originated during the troubleshooting session (e.g., for a
duration of 15 minutes). Bob, who is troubleshooting the problem,
arranges to make a call that Alice can attempt to transfer. Bob
calls Alice, which creates initial dialog1, and then Alice transfers
the call to connect Bob to Carol. Logged signaling is correlated
using the test case identifier, which is the local UUID
ab30317f1a784dc48ff824d0d3715d86 in the Session-ID header field of
INVITE request F1. Logging by Alice's terminal begins when it
receives and echoes the "log me" marker in INVITE F1 and ends when
the last request or response in the dialog is sent or received (200
OK F7 of dialog1). Also during dialog1, Alice's terminal logs
related REFER dialog2, which it initiates and terminates as part of
the call transfer. Alice's terminal inserts a "log me" marker in the
REFER request and 200 OK responses to NOTIFY requests in dialog2.
Both dialog1 and dialog2 have the same test case identifier.
Logging by Bob's terminal begins when it sends INVITE F1, which
includes the "log me" marker, and ends when dialog3, initiated by
Bob, ends. Logging by Carol's terminal begins when it receives the
INVITE F5 with the "log me" marker and ends when dialog3 ends.
dialog3 is not logged by Alice's terminal; however, the test case
identifier ab30317f1a784dc48ff824d0d3715d86 is also the test case
identifier (local-uuid) in INVITE F5. Also, the test case identifier
of dialog2, which is logged by Alice's terminal, can be linked to
dialog1 and dialog3 because the remote-uuid component of dialog2 is
the test case identifier ab30317f1a784dc48ff824d0d3715d86.
Alice Bob Carol
Transferor Transferee Transfer
| | Target
| INVITE F1 | |
dialog1 |<-------------------| |
| 200 OK F2 | |
dialog1 |------------------->| |
| ACK | |
dialog1 |<-------------------| |
| INVITE (hold) | |
dialog1 |------------------->| |
| 200 OK | |
dialog1 |<-------------------| |
| ACK | |
dialog1 |------------------->| |
| REFER F3 (Target-Dialog:1) |
dialog2 |------------------->| |
| 200 OK | |
dialog2 |<-------------------| |
| NOTIFY (100 Trying) F4 |
dialog2 |<-------------------| |
| 200 OK | |
dialog2 |------------------->| |
| | INVITE F5 |
dialog3 | |------------------->|
| | 200 OK |
dialog3 | |<-------------------|
| | ACK |
dialog3 | |------------------->|
| NOTIFY (200 OK) F6| |
dialog2 |<-------------------| |
| 200 OK | |
dialog2 |------------------->| |
| BYE | |
dialog1 |------------------->| |
| 200 OK F7 | |
dialog1 |<-------------------| |
| | BYE |
dialog3 | |<-------------------|
| | 200 OK |
dialog3 | |------------------->|
Figure 2: "Log Me" Marking Related Dialogs in Call Transfer
F1: Bob's UA inserts the "logme" parameter in the Session-ID header
field of the INVITE request that creates dialog1.
F3: Alice's UA inserts the "logme" parameter in the Session-ID
header field of the REFER request that creates dialog2, which
is related to dialog1.
F5: Bob's UA inserts the "logme" parameter in the Session-ID header
field of the INVITE request that creates dialog3, which is
related to dialog1.
F1 INVITE Transferee -> Transferor
INVITE sips:transferor@atlanta.example.com SIP/2.0
Via: SIP/2.0/TLS [2001:db8::1];branch=z9hG4bKnas432
Max-Forwards: 70
To: <sips:transferor@atlanta.example.com>
From: <sips:transferee@biloxi.example.com>;tag=7553452
Call-ID: 090459243588173445
Session-ID: ab30317f1a784dc48ff824d0d3715d86
;remote=00000000000000000000000000000000;logme
CSeq: 29887 INVITE
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
Supported: replaces, gruu, tdialog
Contact: <sips:3ld812adkjw@biloxi.example.com;gr=3413kj2ha>
Content-Type: application/sdp
Content-Length: ...
F2 200 OK Transferor -> Transferee
SIP/2.0 200 OK
Via: SIP/2.0/TLS [2001:db8::1];branch=z9hG4bKnas432
To: <sips:transferor@atlanta.example.com>;tag=31kdl4i3k
From: <sips:transferee@biloxi.example.com>;tag=7553452
Call-ID: 090459243588173445
Session-ID: 47755a9de7794ba387653f2099600ef2
;remote=ab30317f1a784dc48ff824d0d3715d86;logme
CSeq: 29887 INVITE
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
Supported: replaces, gruu, tdialog
Contact: <sips:4889445d8kjtk3@atlanta.example.com;gr=723jd2d>
Content-Type: application/sdp
Content-Length: ...
F3 REFER Transferor -> Transferee
REFER sips:3ld812adkjw@biloxi.example.com;gr=3413kj2ha SIP/2.0
Via: SIP/2.0/TLS pc33.atlanta.example.com;branch=z9hG4bKna9
Max-Forwards: 70
To: <sips:3ld812adkjw@biloxi.example.com;gr=3413kj2ha>
From: <sips:transferor@atlanta.example.com>;tag=1928301774
Call-ID: a84b4c76e66710
Session-ID: 47755a9de7794ba387653f2099600ef2
;remote=ab30317f1a784dc48ff824d0d3715d86;logme
CSeq: 314159 REFER
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
Supported: gruu, replaces, tdialog
Require: tdialog
Refer-To: <sips:transfertarget@chicago.example.com>
Target-Dialog: 090459243588173445;local-tag=7553452
;remote-tag=31kdl4i3k
Contact: <sips:4889445d8kjtk3@atlanta.example.com;gr=723jd2d>
Content-Length: 0
F4 NOTIFY Transferee -> Transferor
NOTIFY sips:4889445d8kjtk3@atlanta.example.com
;gr=723jd2d SIP/2.0
Via: SIP/2.0/TLS [2001:db8::1];branch=z9hG4bKnas432
Max-Forwards: 70
To: <sips:transferor@atlanta.example.com>;tag=1928301774
From: <sips:3ld812adkjw@biloxi.example.com;gr=3413kj2ha>
;tag=a6c85cf
Call-ID: a84b4c76e66710
Session-ID: ab30317f1a784dc48ff824d0d3715d86
;remote=47755a9de7794ba387653f2099600ef2;logme
CSeq: 73 NOTIFY
Contact: <sips:3ld812adkjw@biloxi.example.com;gr=3413kj2ha>
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
Supported: replaces, tdialog
Event: refer
Subscription-State: active;expires=60
Content-Type: message/sipfrag
Content-Length: ...
F5 INVITE Transferee -> Transfer Target
INVITE sips:transfertarget@chicago.example.com SIP/2.0
Via: SIP/2.0/TLS [2001:db8::1];branch=z9hG4bKnas41234
Max-Forwards: 70
To: <sips:transfertarget@chicago.example.com>
From: <sips:transferee@biloxi.example.com>;tag=j3kso3iqhq
Call-ID: 90422f3sd23m4g56832034
Session-ID: ab30317f1a784dc48ff824d0d3715d86
;remote=00000000000000000000000000000000;logme
CSeq: 521 REFER
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
Supported: replaces, gruu, tdialog
Contact: <sips:3ld812adkjw@biloxi.example.com;gr=3413kj2ha>
Content-Type: application/sdp
Content-Length: ...
F6 NOTIFY Transferee -> Transferor
NOTIFY sips:4889445d8kjtk3@atlanta.example.com
;gr=723jd2d SIP/2.0
Via: SIP/2.0/TLS [2001:db8::1];branch=z9hG4bKnas432
Max-Forwards: 70
To: <sips:transferor@atlanta.example.com>;tag=1928301774
From: <sips:3ld812adkjw@biloxi.example.com;gr=3413kj2ha>
;tag=a6c85cf
Call-ID: a84b4c76e66710
Session-ID: ab30317f1a784dc48ff824d0d3715d86
;remote=47755a9de7794ba387653f2099600ef2;logme
CSeq: 74 NOTIFY
Contact: <sips:3ld812adkjw@biloxi.example.com;gr=3413kj2ha>
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
Supported: replaces, tdialog
Event: refer
Subscription-State: terminated;reason=noresource
Content-Type: message/sipfrag
Content-Length: ...
3.8. Forked Requests
A SIP intermediary is required to copy the "log me" marker into
forked requests. SIP request forking is discussed in Sections 4 and
16.6 of [RFC3261].
4. SIP Entity Behavior
4.1. Scope of Marking
"Log me" marking is intended to be limited, in time period and number
of dialogs marked, to the minimum needed to troubleshoot a particular
problem or perform a particular test.
o SIP entities MUST be configured to "log me" mark only dialogs
needed for the current testing purpose, e.g., troubleshooting or
regression testing. The mechanisms in this section ensure that
"log me" marking begins at dialog creation and, other than cases
of marking related dialogs or premature ending, ends when the
dialog being "log me" marked ends.
o If a dialog is to be marked, the only way to initiate "log me"
marking is at the dialog-creating request (e.g., SIP INVITE) sent
by an originating endpoint or an intermediary that marks on behalf
of the originating endpoint. Marking that appears mid-dialog is
an error as described in Section 5.1.2. The final terminating
endpoint, or intermediary that marks on behalf of the terminating
endpoint, cannot initiate marking, but it takes action as defined
in Sections 4.2 and 4.3 if it receives an incoming "log me"
marker.
Note that the error cases described in Section 5.1 cause SIP entities
to stop "log me" marking, and the requirements in Section 7 also
place requirements on SIP entities, including allowing SIP entities
to not log signaling based on local policies (see Section 8.6).
4.2. Endpoints
A common scenario is to have both originating and terminating
endpoints support "log me" marking with the originating endpoint
configured to initiate "log me" marking. In this simplest use case,
the originating UA inserts a "log me" marker in the dialog-creating
SIP request and all subsequent SIP requests within that dialog. The
"log me" marker is passed through the SIP intermediaries and arrives
at the terminating UA, which echoes the "log me" marker in the
corresponding responses. If the terminating UA sends an in-dialog
request on a dialog that is being "log me" marked, it inserts a "log
me" marker and the originating UA echoes the "log me" marker in
responses. The terminating UA logs the "log me" marked SIP requests
and responses if it is allowed as per policy defined in the
terminating network. This basic use case suggests the following
rules for originating and terminating UAs.
For originating UAs:
o The originating UA configured for "log me" marking MUST insert a
"log me" marker into the dialog-creating SIP request and
subsequent in-dialog SIP requests.
o The originating UA itself logs marked requests and responses.
o The originating UA echoes, in responses, the "log me" marker
received in in-dialog requests from the terminating side.
o The originating UA logs the SIP responses that it sends in
response to received "log me" marked in-dialog requests.
o The originating UA MAY also apply these rules to any subsequent
related SIP dialogs as described in Section 3.7.
For terminating UAs:
o The terminating UA detects that a dialog is of interest to logging
by the existence of a "log me" marker in an incoming dialog-
creating SIP request.
o The terminating UA itself logs marked requests and corresponding
marked responses if allowed as per policy.
o The terminating UA MUST echo a "log me" marker in responses to a
SIP request that included a "log me" marker.
o If the terminating UA has detected that a dialog is being "log me"
marked, it MUST insert a "log me" marker in any in-dialog SIP
requests that it sends.
o The terminating UA itself logs any in-dialog SIP requests that it
sends if allowed as per policy.
o The terminating UA MAY also apply these rules to any subsequent
related SIP dialogs as described in Section 3.7.
4.3. SIP Intermediaries Acting on Behalf of Endpoints
A network operator may know that some of the UAs connected to the
network do not support "log me" marking. Subject to the
authorizations in Section 7.1, a SIP intermediary close to the UA
(e.g., edge proxy, B2BUA) on the originating and/or terminating sides
inserts the "log me" marker instead in order to test sessions
involving such UAs.
The originating and terminating SIP intermediaries are not identified
by protocol means but are designated and explicitly configured by the
network administrator to "log me" mark on behalf of endpoints. The
intermediaries that are known to be closest to the terminals can be
configured to "log me" mark on behalf of terminals that do not
support "log me" marking. The originating SIP intermediary is the
first one to be traversed by a SIP request sent by the originating
endpoint. Similarly, the terminating SIP intermediary is the last
intermediary traversed before the terminating endpoint is reached.
The SIP intermediary at the originating side is configured to insert
the "log me" marker on behalf of the originating endpoint. If the
terminating UA does not echo the "log me" marker in responses to a
marked request, then the SIP intermediary closest to the terminating
UA, if configured to mark on behalf of the terminating UA, inserts a
"log me" marker in responses to the request. Likewise, if the
terminating UA sends an in-dialog request, the SIP intermediary at
the terminating side inserts a "log me" marker and the SIP
intermediary at the originating side echoes the "log me" marker in
responses to that request. Originating and terminating
intermediaries that are configured for "log me" marking on behalf of
the endpoint must also mark dialog-creating requests that contain
Target-Dialog [RFC4538], Join [RFC3911], and Replaces [RFC3891]
header fields and corresponding responses. The SIP intermediaries at
the originating and terminating sides log the "log me" marked SIP
requests and responses if it is allowed as per policy defined in the
originating and terminating networks. This scenario suggests the
following rules when a SIP intermediary is configured to initiate or
handle "log me" marking on behalf of a UA.
For the originating SIP intermediary:
o The originating SIP intermediary configured for "log me" marking
MUST insert a "log me" marker into the dialog-creating SIP request
and subsequent in-dialog SIP requests.
o The originating SIP intermediary itself logs marked requests and
responses.
o The originating SIP intermediary detects the "log me" marker
received in in-dialog requests and echoes the "log me" marker in
the corresponding SIP responses.
o The originating SIP intermediary logs the SIP responses that it
sends in response to "log me" marked in-dialog requests.
o The originating SIP intermediary MAY also apply these rules to any
subsequent related SIP dialogs as described in Section 3.7.
For the terminating SIP intermediary:
o The terminating SIP intermediary detects that a dialog is of
interest to logging by the existence of a "log me" marker in an
incoming dialog-creating SIP request.
o The terminating SIP intermediary itself logs marked requests and
corresponding responses if allowed as per policy.
o The terminating SIP intermediary MUST echo a "log me" marker in
responses to a SIP request that included a "log me" marker.
o If the terminating SIP intermediary has detected that a dialog is
being "log me" marked, it MUST insert a "log me" marker in any in-
dialog SIP requests from the terminating UA.
o The terminating SIP intermediary itself logs any in-dialog SIP
requests that it sends if allowed as per policy.
o The terminating SIP intermediary MAY also apply these rules to any
subsequent related SIP dialogs as described in Section 3.7.
4.4. B2BUAs
B2BUA "log me" behavior is specified based on its different signaling
plane roles described in [RFC7092].
A Proxy-B2BUA SHOULD copy "log me" marking in requests and responses
from its terminating side to the originating side without needing
explicit configuration to do so.
A dialog on one "side" of the B2BUA may or may not be coupled to a
related dialog on the other "side" for "log me" purposes. To allow
end-to-end troubleshooting of user problems and regression testing, a
signaling-only and SDP-modifying signaling-only B2BUA [RFC7092]
SHOULD couple related dialogs for "log me" marking purposes and pass
on the received "log me" parameter from the originating side to the
terminating side and vice versa. For example, a SIP B2BUA handling
an end-to-end session between an external caller and an agent in a
contact center environment can couple the dialog between itself and
an agent with the dialog between itself and the external caller. It
can pass on the "log me" marking from the originating side to the
terminating side to enable end-to-end logging of specific sessions of
interest.
For dialogs that are being "log me" marked, all B2BUAs MUST "log me"
mark in-dialog SIP requests that they generate on their own, without
needing explicit configuration to do so. This rule applies to both
the originating and terminating sides of a B2BUA.
4.5. "Log Me" Marker Processing by SIP Intermediaries
4.5.1. Stateless Processing
Typically, "log me" marking will be done by an originating UA and
echoed by a terminating UA. SIP intermediaries on the signaling path
between these UAs that do not perform the tasks described in Sections
4.3 or 4.4 MUST simply log any request or response that contains a
"log me" marker in a stateless manner, if it is allowed per local
policy.
4.5.2. Stateful Processing
The originating and terminating SIP intermediaries that "log me" mark
on behalf of endpoints and SIP intermediaries that remove "log me"
marking at the network boundary must maintain state to enable "log
me" marking. Applicable scenarios are as follows:
o The originating UA does not support "log me" marking. This
scenario was described in Section 4.3 and requires support by the
originating SIP intermediary. "Log me" marker processing is
illustrated in Section 4.5.2.1.
o The terminating UA does not support "log me" marking. This
scenario was described in Section 4.3 and requires support by the
terminating SIP intermediary. "Log me" marker processing is
illustrated in Section 4.5.2.2.
o The originating network ensures that it does not pass marking
outside its boundaries in order to not impact any external
networks. The originating network removes "log me" marking from
SIP requests and responses before forwarding them from its network
boundary to external networks, but it adds marking back to any
incoming SIP requests and responses belonging to any "log me"
marked dialog. This scenario requires support by the SIP
intermediary at the originating network boundary. "Log me" marker
processing is illustrated in Section 4.5.2.3.
o The terminating network ensures that it does not allow "log me"
marking from external networks to pass through its boundary to its
internal entities. The terminating network removes "log me"
marking from SIP requests and responses before forwarding them
internally, but it adds marking back to any outgoing SIP requests
and responses belonging to any "log me" marked dialog. This
scenario requires support by the SIP intermediary at the
terminating network boundary. "Log me" marker processing is
illustrated in Section 4.5.2.4.
o The terminating network does not support "log me" marking and does
not echo marking that it receives. The originating network adds
marking back to any incoming SIP requests and responses belonging
to the "log me" marked dialog. This scenario requires support by
the SIP intermediary at the originating network boundary and "log
me" marker processing is illustrated in Section 4.5.2.5.
SIP intermediary behavior in these scenarios is illustrated using
[RFC3665] example call flow "Session Establishment Through Two
Proxies".
4.5.2.1. "Log Me" Marking Not Supported by Originating UA
Alice's UA does not support "log me" marking; hence, Proxy 1, which
is the SIP intermediary closest to Alice, is configured to act on
behalf of Alice's UA to "log me" mark specific dialogs of interest
that are created by Alice for troubleshooting purposes.
In Figure 3, Proxy 1 in the originating network maintains state of
which dialogs are being logged in order to "log me" mark all SIP
requests and responses that it receives from Alice's UA before
forwarding them to Proxy 2.
[ NETWORK A ] [ NETWORK B ]
Alice Proxy 1 Proxy 2 Bob
| | | |
| INVITE F1 | | |
| (no logme) | | |
|--------------->| | |
| | INVITE F2 | |
| | (logme) | |
| |--------------->| |
| | | |
| | | |
| 100 F3 | | INVITE F4 |
| (logme) | | (logme) |
|<---------------| 100 F5 |--------------->|
| | (logme) | |
| |<---------------| |
| | | 180 F6 |
| | | (logme) |
| | 180 F7 |<---------------|
| | (logme) | |
| 180 F8 |<---------------| |
| (logme) | | |
|<---------------| | 200 F9 |
| | | (logme) |
| | 200 F10 |<---------------|
| | (logme) | |
| 200 F11 |<---------------| |
| (logme) | | |
|<---------------| | |
| ACK F12 | | |
| (no logme) | | |
|--------------->| | |
| | | |
| | ACK F13 | |
| | (logme) | |
| |--------------->| |
| | | |
| | | ACK F14 |
| | | (logme) |
| | |--------------->|
| Both Way RTP Media |
|<================================================>|
| | | BYE F15 |
| | | (logme) |
| | BYE F16 |<---------------|
| | (logme) | |
| BYE F17 |<---------------| |
| (logme) | | |
|<---------------| | |
| 200 F18 | | |
| (no logme) | | |
|--------------->| | |
| | 200 F19 | |
| | (logme) | |
| |--------------->| |
| | | |
| | | 200 F20 |
| | | (logme) |
| | |--------------->|
| | | |
Figure 3: The Originating UA Does Not Support "Log Me" Marking
F1: Alice's UA does not insert a "log me" marker in the dialog-
creating INVITE request F1. Nevertheless, Proxy 1 is
configured to initiate logging on behalf of Alice. Proxy 1
logs INVITE request F1 and maintains state that this dialog is
being logged.
F2: Proxy 1 inserts a "log me" marker in INVITE request F2 before
forwarding it to Proxy 2. Proxy 1 logs this request.
F3: Proxy 1 inserts a "log me" marker in 100 response F3 before
forwarding it to Alice's UA since this is a response sent on a
dialog that is being "log me" marked. Proxy 1 logs this
response.
F4: "Bob's UA detects the "log me" marker and logs the INVITE
request F4 if allowed as per policy.
F6: Bob's UA echoes the "log me" marker in INVITE request F4 into
180 response F6. It logs this response if allowed as per
policy.
F7 and F8: Proxy 1 logs the received "180" response F7 and passes
the "log me" marker to Alice's UA in F8.
F12: Proxy 1 receives ACK with no "log me" marker. It doesn't
consider this an error since it is configured to "log me" mark
on behalf of Alice's UA.
F13: Proxy 1 inserts a "log me" marker in ACK request F13 before
forwarding it to Proxy 2. Proxy 1 logs this request.
F15: Bob's UA inserts a "log me" marker in the in-dialog BYE request
and this "log me" marker is carried back to Alice's UA in F16
and F17. Bob's UA logs this request if allowed as per policy.
F18: Alice's UA does not echo the "log me" marker from BYE request
F17 into 200 response F18.
F19: Proxy 1 inserts a "log me" marker in 200 response F19 before
forwarding it to Proxy 2. Proxy 1 logs this response.
4.5.2.2. "Log Me" Marking Not Supported by Terminating UA
In Figure 4, Bob's UA does not support "log me" marking, so Proxy 2
in the terminating network maintains state to ensure "log me" marking
of SIP requests and responses from Bob's UA.
[ NETWORK A ] [ NETWORK B ]
Alice Proxy 1 Proxy 2 Bob
| | | |
| INVITE F1 | | |
| (log me) | | |
|--------------->| | |
| | INVITE F2 | |
| | (log me) | |
| |--------------->| |
| | | |
| | | |
| 100 F3 | | |
| (log me) | | |
|<---------------| | |
| | | INVITE F4 |
| | | (log me) |
| | 100 F5 |--------------->|
| | (log me) | |
| |<---------------| |
| | | 180 F6 |
| | | (no log me) |
| | |<---------------|
| | | |
| | | |
| | 180 F7 | |
| | (log me) | |
| |<---------------| |
| | | |
| | | |
| 180 F8 | | |
| (log me) | | |
|<---------------| | 200 F9 |
| | | (no log me) |
| | 200 F10 |<---------------|
| | (log me) | |
| 200 F11 |<---------------| |
| (log me) | | |
|<---------------| | |
| ACK F12 | | |
| (log me) | | |
|--------------->| | |
| | ACK F13 | |
| | (log me) | |
| |--------------->| ACK F14 |
| | | (log me) |
| | |--------------->|
| Both Way RTP Media |
|<================================================>|
| | | BYE F15 |
| | | (no log me) |
| | BYE F16 |<---------------|
| | (log me) | |
| BYE F17 |<---------------| |
| (log me) | | |
|<---------------| | |
| 200 F18 | | |
| (log me) | | |
|--------------->| | |
| | 200 F19 | |
| | (log me) | |
| |--------------->| 200 F20 |
| | | (log me) |
| | |--------------->|
| | | |
Figure 4: The Terminating UA Does Not Support "Log Me" Marking.
F1: Alice's UA inserts a "log me" marker in the dialog-creating
INVITE request F1.
F2: INVITE F2 is "log me" marked; therefore, Proxy 2 maintains
state that this dialog is to be logged. Proxy 2 logs the
request and responses of this dialog if allowed per policy.
F5: Proxy 2 inserts a "log me" marker in the 100 response it sends
to Proxy 1.
F6: Bob's UA does not support "log me" marking; therefore, the 180
response to the INVITE request doesn't have a "log me" marker.
F7: Proxy 2 inserts a "log me" marker in the 180 response on behalf
of Bob's UA before forwarding it. The same applies to response
F10 and the BYE request in F16.
4.5.2.3. "Log Me" Marking Removed by Originating Network
If network A in Figure 5 is performing testing independently of
network B, then network A removes "log me" marking from SIP requests
and responses forwarded to network B to prevent triggering unintended
logging in network B. Proxy 1 removes "log me" marking from requests
and responses that it forwards to Proxy 2 and maintains state of
which dialogs are being "log me" marked in order to "log me" mark
requests and responses that it forwards from Proxy 2 to Alice's UA.
For troubleshooting purposes, Proxy 1 MAY also log the requests and
responses sent to or received from Proxy 2 even though it removed
"log me" marker prior to forwarding the messages to Proxy 2.
[ NETWORK A ] [ NETWORK B ]
Alice Proxy 1 Proxy 2 Bob
| | | |
| INVITE F1 | | |
| (logme) | | |
|--------------->| | |
| | INVITE F2 | |
| | (no logme) | |
| |--------------->| |
| | | |
| | | |
| 100 F3 | | |
| (logme) | | INVITE F4 |
| | | (no logme) |
|<---------------| 100 F5 |--------------->|
| | (no logme) | |
| |<---------------| |
| | | 180 F6 |
| | | (no logme) |
| | 180 F7 |<---------------|
| | (no logme) | |
| 180 F8 |<---------------| |
| (logme) | | |
|<---------------| | 200 F9 |
| | | (no logme) |
| | 200 F10 |<---------------|
| | (no logme) | |
| 200 F11 |<---------------| |
| (logme) | | |
|<---------------| | |
| ACK F12 | | |
| (logme) | | |
|--------------->| | |
| | | |
| | ACK F13 | |
| | (no logme) | |
| |--------------->| |
| | | |
| | | ACK F14 |
| | | (no logme) |
| | |--------------->|
| Both Way RTP Media |
|<================================================>|
| | | BYE F15 |
| | | (no logme) |
| | BYE F16 |<---------------|
| | (no logme) | |
| BYE F17 |<---------------| |
| (logme) | | |
|<---------------| | |
| 200 F18 | | |
| (logme) | | |
|--------------->| | |
| | 200 F19 | |
| | (no logme) | |
| |--------------->| |
| | | |
| | | 200 F20 |
| | | (no logme) |
| | |--------------->|
| | | |
Figure 5: The Originating Network Removes "Log Me" Marking from
Outgoing SIP Messages at its Network Edge.
F1: Alice's UA inserts a "log me" marker in the dialog-creating
INVITE request, and Proxy 1 therefore maintains state that this
dialog is to be logged.
F2: Proxy 1 removes "log me" marking from INVITE request before
forwarding it to Proxy 2. Proxy 1 logs INVITE request F2.
F3: Proxy 1 inserts a "log me" marker in the 100 response sent to
Alice's UA. Proxy 1 logs this response.
F8: Proxy 1 inserts a "log me" marker in the 180 response before
forwarding it to Alice's UA. Proxy 1 logs this response. The
same applies to responses F11 and F17.
F13: Proxy 1 removes "log me" marking from the ACK request. Proxy 1
logs this request before forwarding it to Proxy 2.
F19: Proxy 1 removes "log me" marking from the 200 response of the
BYE request. Proxy 1 logs this response before forwarding it
to Proxy 2.
4.5.2.4. "Log Me" Marking Removed by Supporting Terminating Network
In Figure 6, Proxy 2 removes "log me" marking from all SIP requests
and responses entering network B. However, Proxy 2 supports
maintaining the marking state of the dialog and "log me" marks
requests and responses that it sends towards Proxy 1. For
troubleshooting purposes, Proxy 2 MAY also log the requests and
responses received from or sent to Bob even though it removed the
"log me" marker prior to forwarding the messages to Bob. This
scenario might be used for troubleshooting a signaling path between
two enterprise or carrier networks, or across a transit network, with
minimal logging (i.e., only at the network boundaries).
[ NETWORK A ] [ NETWORK B ]
Alice Proxy 1 Proxy 2 Bob
| | | |
| INVITE F1 | | |
| (log me) | | |
|--------------->| | |
| | INVITE F2 | |
| | (log me) | |
| |--------------->| |
| | | |
| | | |
| 100 F3 | | |
| (log me) | | |
|<---------------| | |
| | | INVITE F4 |
| | | (no log me) |
| | 100 F5 |--------------->|
| | (log me) | |
| |<---------------| |
| | | 180 F6 |
| | | (no log me) |
| | |<---------------|
| | 180 F7 | |
| | (log me) | |
| |<---------------| |
| | | |
| | | |
| 180 F8 | | |
| (log me) | | |
|<---------------| | 200 F9 |
| | | (no log me) |
| | 200 F10 |<---------------|
| | (log me) | |
| 200 F11 |<---------------| |
| (log me) | | |
|<---------------| | |
| ACK F12 | | |
| (log me) | | |
|--------------->| | |
| | ACK F13 | |
| | (log me) | |
| |--------------->| ACK F14 |
| | | (no log me) |
| | |--------------->|
| Both Way RTP Media |
|<================================================>|
| | | BYE F15 |
| | | (no log me) |
| | BYE F16 |<---------------|
| | (log me) | |
| BYE F17 |<---------------| |
| (log me) | | |
|<---------------| | |
| 200 F18 | | |
| (log me) | | |
|--------------->| | |
| | 200 F19 | |
| | (log me) | |
| |--------------->| 200 F20 |
| | | (no log me) |
| | |--------------->|
| | | |
Figure 6: The terminating network removes "log me" marking from
incoming SIP messages at its network edge.
F1: Alice's UA inserts a "log me" marker in the dialog-creating
INVITE request F1. Proxy 1 detects the "log me" marker, logs
the request, and maintains state that this dialog is to be
logged.
F2: Proxy 2 removes the "log me" marker in the INVITE request F2
before forwarding it as F4. The same applies to responses F13
and F19.
F6: Proxy 2 inserts a "log me" marker in the 180 response to the
INVITE request and logs the request before forwarding it as F7.
The same applies to response F9 and the BYE request in F15.
4.5.2.5. "Log Me" Marking Passed by Non-supporting Terminating Network
In Figure 6, Proxy 2 is not "log me" aware and therefore passes
marking in all SIP requests and responses entering network B
according to the rules in Sections 16.6 and 16.7 of [RFC3261]. Proxy
2 does not log requests and responses in the dialog. Proxy 1
supports maintaining the marking state of the dialog. When Proxy 1
observes that requests and responses received from Proxy 2 are not
marked, it adds the marking.
For troubleshooting purposes, Proxy 1 MAY also log the requests and
responses received from or sent to Proxy 2 even though Proxy 2 didn't
add "log me" to messages sent to Proxy 1.
[ NETWORK A ] [ NETWORK B ]
Alice Proxy 1 Proxy 2 Bob
| | | |
| INVITE F1 | | |
| (log me) | | |
|--------------->| | |
| | INVITE F2 | |
| | (log me) | |
| |--------------->| |
| | | |
| | | |
| 100 F3 | | |
| (log me) | | |
|<---------------| | |
| | | INVITE F4 |
| | | (log me) |
| | 100 F5 |--------------->|
| | (no log me) | |
| |<---------------| |
| | | 180 F6 |
| | | (no log me) |
| | |<---------------|
| | 180 F7 | |
| | (no log me) | |
| |<---------------| |
| | | |
| | | |
| 180 F8 | | |
| (log me) | | |
|<---------------| | 200 F9 |
| | | (no log me) |
| | 200 F10 |<---------------|
| | (no log me) | |
| 200 F11 |<---------------| |
| (log me) | | |
|<---------------| | |
| ACK F12 | | |
| (log me) | | |
|--------------->| | |
| | ACK F13 | |
| | (log me) | |
| |--------------->| ACK F14 |
| | | (log me) |
| | |--------------->|
| Both Way RTP Media |
|<================================================>|
| | | BYE F15 |
| | | (no log me) |
| | BYE F16 |<---------------|
| | (no log me) | |
| BYE F17 |<---------------| |
| (log me) | | |
|<---------------| | |
| 200 F18 | | |
| (log me) | | |
|--------------->| | |
| | 200 F19 | |
| | (log me) | |
| |--------------->| 200 F20 |
| | | (log me) |
| | |--------------->|
| | | |
Figure 7: The Terminating Network Removes "Log Me" Marking from
Incoming SIP Messages at its Network Edge.
F1: Alice's UA inserts a "log me" marker in the dialog-creating
INVITE request F1. Proxy 1 detects the "log me" marker, logs
the request, and maintains state that this dialog is to be
logged.
F2: Proxy 2 passes the "log me" marker in the INVITE request F2
before forwarding it as F4. The same applies to request F13
and response F19.
F6: Bob's UA does not support "log me" marking and does not echo
the "log me" marker in response F6. The same applies to
response F9 and the BYE request F15.
F7: Proxy 1 inserts a "log me" marker in the 180 response of the
INVITE request before forwarding it as F8. The same applies to
response F10 and the BYE request F16.
5. Errors
5.1. Error Cases
The following error cases are possible for "log me" marking:
1. A "log me" marker is unexpectedly missing from a dialog that is
being logged.
2. A "log me" marker unexpectedly appears in a dialog that is not
being logged.
3. A "log me" marker unexpectedly disappears and then reappears in a
dialog being logged. This is treated in the same way as case 1.
4. A "log me" marker is unexpectedly missing from a retransmission
in a dialog being logged. This is treated in the same way as
case 1.
These cases apply to any request or response sent by any entity and
in any direction in a dialog being "log me" marked. Detection of
these error cases is described in this section.
5.1.1. Missing "Log Me" Marker Error Case
Since "log me" marking is per-dialog, if a dialog is being marked and
marking is missing from a request or response then this is an error.
However, detecting such errors is not as simple as checking for
missing markers because of cases such as non-supporting terminals
where it is normal that marking is not done.
Detecting errors must be evaluated separately for each neighbor. It
is an error if a particular neighbor has previously sent "log me" in
the dialog and then stops, independently of what has been happening
with other neighbors.
UAs and intermediaries that are stateless with respect to "log me"
marking are not able detect such errors. User agents and
intermediaries that are stateful with respect to "log me" marking are
able to detect that a marker is missing from a dialog that has
previously been "log me" marked. Error cases are illustrated in this
section, and non-error cases in Section 5.2.1.
The following figures illustrate missing "log me" marker errors.
Figure 8 shows an error detected at Proxy 1, where an expected "log
me" marker is missing.
[ NETWORK A ] [ NETWORK B ]
Alice Proxy 1 Proxy 2 Bob
| | | |
| INVITE F1 | | |
| (log me) | INVITE F2 | |
|--------------->| (log me) | INVITE F3 |
| |--------------->| (log me) |
| | |--------------->|
| | | |
| | | 200 F4 |
| | 200 F5 | (log me) |
| 200 F6 | (log me) |<---------------|
| (log me) |<---------------| |
|<---------------| | |
| | | |
| ACK F7 | | |
| (no log me) | | |
|--------------->| | |
| | ACK F8 | |
| | (no log me) | |
| |--------------->| |
| | | ACK F9 |
| | | (no log me) |
| | |--------------->|
Figure 8: Error Case: Missing "Log Me" Marker
F1: Proxy 1 detects the "log me" marker and maintains state that
this dialog is to be logged.
F7: Proxy 1 detects that the expected "log me" marker is missing,
considers it to be an error, and stops "log me" marking in
subsequent requests and responses in this dialog.
Figure 9 shows an error detected at both Proxy 2 and Bob's UA.
[ NETWORK A ] [ NETWORK B ]
Alice Proxy 1 Proxy 2 Bob
| INVITE F1 | | |
| (log me) | | |
|--------------->| | |
| | INVITE F2 | |
| | (log me) | |
| |--------------->| |
| | | |
| | | |
| 100 F3 | | |
| (log me) | | |
|<---------------| | |
| | | INVITE F4 |
| | | (log me) |
| | 100 F5 |--------------->|
| | (log me) | |
| |<---------------| |
| | | 180 F6 |
| | | (log me) |
| | |<---------------|
| | 180 F7 | |
| | (log me) | |
| |<---------------| |
| | | |
| | | |
| 180 F8 | | |
| (log me) | | |
|<---------------| | 200 F9 |
| | | (log me) |
| | 200 F10 |<---------------|
| | (log me) | |
| 200 F11 |<---------------| |
| (log me) | | |
|<---------------| | |
| ACK F12 | | |
| (no log me) | | |
|--------------->| | |
| | ACK F13 | |
| | (no log me) | |
| |--------------->| ACK F14 |
| | | (no log me) |
| | |--------------->|
Figure 9: Error Case: Missing "Log Me" Marker
F2: Proxy 2 detects the "log me" marker and maintains state that
this dialog is to be logged.
F4: Bob's UA detects the "log me" marker and maintains state that
this dialog is to be logged.
F12: Proxy 1 detects that the expected "log me" marker is missing,
considers it to be an error, and stops "log me" marking in
subsequent requests and responses in this dialog. Hence, it
does not insert a "log me" marker in F13.
F13: Proxy 2 detects that the expected "log me" marker is missing,
considers it to be an error, and stops "log me" marking in
subsequent requests and responses in this dialog.
F14: Proxy 2 does not insert a "log me" marker because it has
stopped "log me" marking due to an error observed in F13.
Bob's UA detects that the expected "log me" marker is missing,
considers it to be an error, and stops "log me" marking in
subsequent requests and responses in this dialog.
5.1.2. "Log Me" Marker Appears Mid-dialog Error Case
SIP endpoints, intermediaries acting on behalf of endpoints, and
B2BUAs that can perform "log me" marking are stateful. Such entities
will expect a "log me" marker only for dialogs where the initial
dialog-creating request was "log me" marked, either by themselves or
by an upstream entity. "Log me" marking that subsequently begins
mid-dialog is an error.
Figure 10 illustrates a "log me" marking error observed in the middle
of a dialog. Alice's UA supports "log me" marking but the call is
not initially marked for logging, i.e., INVITE F1 is not "log me"
marked. But Alice's UA starts to "log me" mark at the ACK request
F7. Proxy 1 supports "log me" marking at the originating network
boundary and therefore detects the error, does not log signaling, and
removes the "log me" marker before forwarding the ACK request F8.
[ NETWORK A ] [ NETWORK B ]
Alice Proxy 1 Proxy 2 Bob
| | | |
| INVITE F1 | | |
| (no log me) | INVITE F2 | |
|--------------->| (no log me) | INVITE F3 |
| |--------------->| (no log me) |
| | |--------------->|
| | | |
| | | 200 F4 |
| | 200 F5 | (no log me) |
| 200 F6 | (no log me) |<---------------|
| (no log me) |<---------------| |
|<---------------| | |
| | | |
| ACK F7 | | |
| (log me) | | |
|--------------->| | |
| | ACK F8 | |
| | (no log me) | |
| |--------------->| |
| | | ACK F9 |
| | | (log me) |
| | |--------------->|
Figure 10: Error Case: "Log Me" Marker Begins Mid-dialog
5.2. Non-error Cases
5.2.1. Missing "Log Me" Marker Non-error Case
The following figure illustrates a non-error case.
Figure 11 shows Proxy 2 receiving a response with no "log me" marker
that is not an error case. Proxy 2 is configured by network B to
perform "log me" marking on behalf of Bob's UA, which does not
support "log me" marking. Proxy 2 does not therefore expect
responses from Bob to include a "log me" marker.
[ NETWORK A ] [ NETWORK B ]
Alice Proxy 1 Proxy 2 Bob
| | | |
| INVITE F1 | | |
| (log me) | | |
|--------------->| | |
| | INVITE F2 | |
| | (log me) | |
| |--------------->| |
| | | |
| | | |
| 100 F3 | | |
| (log me) | | |
|<---------------| | |
| | | INVITE F4 |
| | | (log me) |
| | 100 F5 |--------------->|
| | (log me) | |
| |<---------------| |
| | | 180 F6 |
| | | (no log me) |
| | |<---------------|
| | 180 F7 | |
| | (log me) | |
| |<---------------| |
| 180 F8 | | |
| (log me) | | |
|<---------------| | |
Figure 11: Non-error Case: Missing "Log Me" Marker
F2: Proxy 2 detects the "log me" marker and maintains state that
this dialog is to be logged. Proxy 2 inserts "log me" markers
on behalf of Bob's user agent, such as in F7.
F6: Proxy 2 detects that the "log me" marker is missing from the
response but considers "log me" marking to be ongoing as a
marker was not expected.
F7: Proxy 2 continues to "log me" mark requests and responses on
behalf of Bob's UA.
5.2.2. "Log Me" Marker Appears Mid-dialog Non-error Case
A SIP intermediary that can perform "log me" marking on behalf of an
endpoint MAY optionally mark a request or response towards a non-
supporting endpoint, such as the 100 response F3 in Figure 3. In
this case, the endpoint will receive a "log me" marker mid-dialog,
and this is not considered an error.
Another use case is a network in which some (but not all) endpoints
support "log me" marking and that wants to avoid treating endpoints
differently by always managing "log me" marking at a SIP
intermediary. In this case, the endpoint that supports "log me" is
not configured to mark a dialog; instead, the SIP intermediary is
configured to perform "log me" marking on behalf of that endpoint.
This case still requires authorization as described in Section 7.1.
This SIP intermediary MAY optionally mark a request or response
towards the endpoint, such as the 100 response F3 in Figure 3. The
endpoint will receive a "log me" marker mid-dialog, which is not
considered an error.
5.2.3. Combining Dialogs Non-error Case
When troubleshooting call flows that involve the SIP Join header
field specified in [RFC3911], the ideal scenario is to have "log me"
marking enabled on all UAs and intermediaries participating in the
end-to-end session. If the ideal scenario is not feasible, the
following rules apply:
o If an endpoint or an intermediary that is "log me" aware and is
already "log me" marking a dialog receives a SIP INVITE with a
Join header field and without a "log me" marker, it MUST NOT "log
me" mark responses and requests exchanged within the new dialog
established as a result of processing the SIP INVITE.
o If an endpoint or an intermediary that is "log me" aware and is
not "log me" marking a dialog receives a SIP INVITE with a Join
header field and with a "log me" marker, it MUST "log me" mark
responses and requests exchanged within the new dialog established
as a result of processing the SIP INVITE as per Section 4 of this
document.
5.3. Error Handling
The two error types that SIP entities must handle are defined in
Section 5.1: a missing marker error and an error of "log me" marking
that begins mid-dialog. Section 5.2 gives exceptions that have
marking that begins mid-dialog or a missing marker but are not
errors.
If a missing marker error is detected by a UA, SIP intermediary, or
B2BUA, it SHOULD consider this to be an error condition in the "log
me" functionality. It MUST NOT mark subsequent requests and
responses, and it MUST stop logging messages in the same dialog. Any
previously logged messages SHOULD be retained, for the time period
defined in Section 8.5, and not deleted.
If a "log me" marking that begins mid-dialog error is detected by a
UA, SIP intermediary, or B2BUA, it SHOULD consider this to be an
error condition in the "log me" functionality. It MUST NOT forward
the "log me" marker, and it MUST NOT log the message. It MUST NOT
mark subsequent requests and responses, and it MUST NOT log
subsequent messages in the same dialog.
"Log me" marking errors can be detected and handled only by
supporting UAs or B2BUAs. A SIP proxy as defined in [RFC3261] cannot
detect or handle marking errors and will simply forward any "log me"
marker it receives.
6. Augmented BNF for the "logme" Parameter
ABNF is described in [RFC5234]. This document introduces a new
"logme" parameter for the Session-ID header field defined in
Section 5 of [RFC7989].
sess-id-param =/ logme-param
logme-param = "logme"
Figure 12: Augmented BNF for the "logme" Parameter
7. Security Considerations
7.1. "Log Me" Authorization
"Log me" marking MUST be disabled by default both at the endpoints
and intermediaries and MUST be enabled only by authorized users. For
example, an end user or network administrator must give permission
for a terminal that supports "log me" marking in order to initiate
marking. Similarly, a network administrator must enable a
configuration at the SIP intermediary to perform "log me" marking on
behalf of a terminal that does not support "log me" marking. The
permission MUST be limited to only specific calls of interest that
are originated in a given time duration.
Activating a debug mode affects the operation of a terminal;
therefore, the debugging configuration MUST be supplied by an
authorized party to an authorized terminal through a secure
communication channel.
7.2. "Log Me" Marker Removal
The log me "log me" marker is not sensitive information, though it will
sometimes be inserted because a particular device is experiencing
problems.
The presence of a log me "log me" marker will cause some SIP entities to log
signaling messages. Therefore, this marker MUST be removed at the
earliest opportunity if it has been incorrectly inserted, such as
appearing mid-dialog in a dialog that was not being logged or outside
the configured start and stop of logging.
If SIP requests and responses are exchanged with an external network
with which there is no agreement to pass "log me" marking, then the
"log me" marking is removed as mandated in Section 3.4.2. This
behavior applies to incoming and outgoing requests and responses.
7.3. Denial-of-Service Attacks
Maliciously configuring a large number of terminals to simultaneously
mark dialogs with a "log me" marker will cause high processor load on
SIP entities that are logging signaling. Since "log me" marking is
for the small number of dialogs subject to troubleshooting or
regression testing, the number of dialogs that can be simultaneously
logged can be statically limited without adversely affecting the
usefulness of "log me" marking. Also, the SIP intermediary closest
to the terminal and SIP intermediary at network edge (e.g., Session
Border Controllers) can be configured to screen-out "log me" markers
when troubleshooting or regression testing is not in progress.
7.4. Data Protection
A SIP entity that has logged information MUST protect the logs.
Storage of the log files are subject to the security considerations
specified in [RFC6872].
8. Privacy Considerations
Logging includes all SIP header fields. The SIP privacy mechanisms
defined in [RFC3323] can be used to ensure that logs do not divulge
personal identity information in the core SIP header fields specified
in [RFC3261].
Privacy mechanisms might also need to be applied to header fields
defined by SIP extensions and for managing the confidentiality of the
Request-URI and SIP header fields and bodies.
8.1. Personal Identifiers
"Log me" marking is defined for the SIP protocol, and SIP has header
fields such as From, Contact, and P-Asserted-Identity that can carry
personal identifiers. Different protocol interactions can be
correlated using the Session-ID and Call-ID header fields, but such
correlation is limited to a single end-to-end session.
In order to protect user privacy during logging, privacy settings can
be enabled or requested by the terminal used by the end user.
[RFC3323] suggests two mechanisms:
o By using the value "anonymous" in the From header field
o By requesting header-level and session-level privacy from SIP
intermediaries using the Privacy header
Endpoints that support Globally Routable User Agent URIs (GRUUs) can
use a temporary GRUU (see Section 3.1.2 of [RFC5627]) assigned by the
Registrar in order to protect user privacy as discussed in
Section 10.3 of [RFC5627].
Intermediaries that perform "log me" marking on behalf of the
endpoints (see Section 4.3) may also be configured to apply privacy
(as defined in Section 3.3 of [RFC3323]) on messages that belong to a
dialog that is "log me" marked.
Complete anonymization (e.g., the Request-URI and the "username"
field in the "o=" parameter of an SDP body) may not be possible in
all circumstances; therefore, administrators of the originating and
terminating networks should consider how privacy will be ensured when
providing consent for "log me" marking.
"Log me" marking is typically used for troubleshooting and regression
testing; in some cases, a service-provider-owned device with a dummy
account can be used instead of a customer device. In such cases, no
personal identifiers are included in the logged signaling messages.
8.2. Data Stored at SIP Intermediaries
SIP endpoints and intermediaries that honor the "log me" request
store all the SIP messages that are exchanged within a given dialog.
SIP messages can contain the personal identifiers listed in
Section 8.1 and additionally a user identity, calling party number,
IP address, hostname, and other user-related or device-related items.
The SIP message bodies describe the kind of session being set up by
the identified end user and device.
"Log me" marking does not introduce any additional user or device
data to SIP but might indicate that a specific user is experiencing a
problem.
If the SIP SDP parameters [SDP-PARAMETERS] contain sensitive security
information (e.g., encryption keys) such as "crypto" [RFC4568], 3GPP-
Integrity-Key, or 3GPP-SRTP-Config [RFC6064] attributes, then the
attribute value MUST be masked with a dummy value prior to storing
the message in a log file. For example, the attribute value can be
replaced with a string of special characters like "X", "*", and "#"
as shown in the example below.
a=crypto:XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXX
8.3. Data Visible at Network Elements
SIP messages that are logged due to "log me" requests are stored only
by the SIP initiators, intermediaries, and recipients. Enablers as
defined in Section 3.1 of [RFC6973], such as firewalls and DNS
servers, do not log messages due to the "log me" marking.
8.4. Preventing Fingerprinting
"Log me" functionality is typically used to troubleshoot a given
problem and, hence, can be used as a method to identify users and
devices that are experiencing issues. The best way to prevent
fingerprinting of users is to enable or request SIP privacy for the
logged dialog.
8.5. Retaining Logs
The lifetime of "log me" marking is equivalent to the lifetime of the
dialog that initiated the "log me" request. When "log me" is
extended to related dialogs, the lifetime is extended until there is
no remaining related dialog for the end-to-end session.
"Log me" automatically expires at the end of the dialog, and there is
no explicit mechanism to turn off logging within a dialog.
The scope of "log me" marking is limited, i.e., a user or the network
administrator has to enable it on a per-session basis or for a
specific time period. This minimizes the risk of exposing user data
for an indefinite time.
The retention time period for logged messages SHOULD be the minimum
needed for each particular troubleshooting or testing case. The
retention period is configured based on the data-retention policies
of service providers and enterprises.
8.6. User Control of Logging
Consent to turn on "log me" marking for a given session MUST be
provided by the end user or by the network administrator. It is
handled outside of the protocol through user interface or application
programming interfaces at the endpoint, call control elements, and
network management systems.
Originating and terminating endpoints that are "log me" aware and
have a user interface MUST indicate (using text, icon, etc.) to the
user that a session is being logged.
SIP entities across the communication path MAY be configured to pass
through the "log me" marking but not honor the request, i.e., not log
the data based on local policies.
8.7. Recommended Defaults
The recommended defaults for "log me" marking are:
o Turn on SIP privacy as described in Section 8 or use a device that
is service provider owned with a dummy user identity for test
calls.
o Use the local UUID portion of the Session-ID header field value at
the originating device as the test case identifier as described in
Section 3.3.
9. IANA Considerations
9.1. Registration of the "logme" Parameter
The following parameter has been added to the "Header Field
Parameters and Parameter Values" section of the "Session Initiation
Protocol (SIP) Parameters" registry:
+-------------+---------------+-------------------------+-----------+
| Header | Parameter | Predefined Values | Reference |
| Field | Name | | |
+-------------+---------------+-------------------------+-----------+
| Session-ID | logme | No (no values are | [RFC8497] |
| | | allowed) | |
+-------------+---------------+-------------------------+-----------+
Table 1
10. References
10.1. Normative References
[MEDIA-TYPES]
IANA, "Media Types",
<https://www.iana.org/assignments/media-types/>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261,
DOI 10.17487/RFC3261, June 2002,
<https://www.rfc-editor.org/info/rfc3261>.
[RFC3323] Peterson, J., "A Privacy Mechanism for the Session
Initiation Protocol (SIP)", RFC 3323,
DOI 10.17487/RFC3323, November 2002,
<https://www.rfc-editor.org/info/rfc3323>.
[RFC3891] Mahy, R., Biggs, B., and R. Dean, "The Session Initiation
Protocol (SIP) "Replaces" Header", RFC 3891,
DOI 10.17487/RFC3891, September 2004,
<https://www.rfc-editor.org/info/rfc3891>.
[RFC3911] Mahy, R. and D. Petrie, "The Session Initiation Protocol
(SIP) "Join" Header", RFC 3911, DOI 10.17487/RFC3911,
October 2004, <https://www.rfc-editor.org/info/rfc3911>.
[RFC4538] Rosenberg, J., "Request Authorization through Dialog
Identification in the Session Initiation Protocol (SIP)",
RFC 4538, DOI 10.17487/RFC4538, June 2006,
<https://www.rfc-editor.org/info/rfc4538>.
[RFC4568] Andreasen, F., Baugher, M., and D. Wing, "Session
Description Protocol (SDP) Security Descriptions for Media
Streams", RFC 4568, DOI 10.17487/RFC4568, July 2006,
<https://www.rfc-editor.org/info/rfc4568>.
[RFC5627] Rosenberg, J., "Obtaining and Using Globally Routable User
Agent URIs (GRUUs) in the Session Initiation Protocol
(SIP)", RFC 5627, DOI 10.17487/RFC5627, October 2009,
<https://www.rfc-editor.org/info/rfc5627>.
[RFC6064] Westerlund, M. and P. Frojdh, "SDP and RTSP Extensions
Defined for 3GPP Packet-Switched Streaming Service and
Multimedia Broadcast/Multicast Service", RFC 6064,
DOI 10.17487/RFC6064, January 2011,
<https://www.rfc-editor.org/info/rfc6064>.
[RFC6872] Gurbani, V., Ed., Burger, E., Ed., Anjali, T., Abdelnur,
H., and O. Festor, "The Common Log Format (CLF) for the
Session Initiation Protocol (SIP): Framework and
Information Model", RFC 6872, DOI 10.17487/RFC6872,
February 2013, <https://www.rfc-editor.org/info/rfc6872>.
[RFC6873] Salgueiro, G., Gurbani, V., and A. Roach, "Format for the
Session Initiation Protocol (SIP) Common Log Format
(CLF)", RFC 6873, DOI 10.17487/RFC6873, February 2013,
<https://www.rfc-editor.org/info/rfc6873>.
[RFC7989] Jones, P., Salgueiro, G., Pearce, C., and P. Giralt, "End-
to-End Session Identification in IP-Based Multimedia
Communication Networks", RFC 7989, DOI 10.17487/RFC7989,
October 2016, <https://www.rfc-editor.org/info/rfc7989>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[SDP-PARAMETERS]
IANA, "Session Description Protocol (SDP) Parameters",
<https://www.iana.org/assignments/sdp-parameters/>.
10.2. Informative References
[RFC3665] Johnston, A., Donovan, S., Sparks, R., Cunningham, C., and
K. Summers, "Session Initiation Protocol (SIP) Basic Call
Flow Examples", BCP 75, RFC 3665, DOI 10.17487/RFC3665,
December 2003, <https://www.rfc-editor.org/info/rfc3665>.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008,
<https://www.rfc-editor.org/info/rfc5234>.
[RFC5589] Sparks, R., Johnston, A., Ed., and D. Petrie, "Session
Initiation Protocol (SIP) Call Control - Transfer",
BCP 149, RFC 5589, DOI 10.17487/RFC5589, June 2009,
<https://www.rfc-editor.org/info/rfc5589>.
[RFC6973] Cooper, A., Tschofenig, H., Aboba, B., Peterson, J.,
Morris, J., Hansen, M., and R. Smith, "Privacy
Considerations for Internet Protocols", RFC 6973,
DOI 10.17487/RFC6973, July 2013,
<https://www.rfc-editor.org/info/rfc6973>.
[RFC7092] Kaplan, H. and V. Pascual, "A Taxonomy of Session
Initiation Protocol (SIP) Back-to-Back User Agents",
RFC 7092, DOI 10.17487/RFC7092, December 2013,
<https://www.rfc-editor.org/info/rfc7092>.
[RFC7206] Jones, P., Salgueiro, G., Polk, J., Liess, L., and H.
Kaplan, "Requirements for an End-to-End Session
Identification in IP-Based Multimedia Communication
Networks", RFC 7206, DOI 10.17487/RFC7206, May 2014,
<https://www.rfc-editor.org/info/rfc7206>.
[RFC8123] Dawes, P. and C. Arunachalam, "Requirements for Marking
SIP Messages to be Logged", RFC 8123,
DOI 10.17487/RFC8123, March 2017,
<https://www.rfc-editor.org/info/rfc8123>.
Acknowledgments
The authors wish to thank Paul Giralt, Paul Kyzivat, Jorgen Axell,
Christer Holmberg, Vijay Gurbani, Ben Campbell, Gonzalo Salgueiro,
Francesca Palombini, Adam Roach, Mirja Kuhlewind, Benjamin Kaduk,
Eric Rescorla, Alissa Cooper, Warren Kumari, and Alexey Melnikov for
their constructive review comments and guidance while developing this
document.
Authors' Addresses
Peter Dawes
Vodafone Group
The Connection
Newbury, Berkshire RG14 2FN
United Kingdom
Phone: +44 7717 275009
Email: peter.dawes@vodafone.com
Chidambaram Arunachalam
Cisco Systems
7200-12 Kit Creek Road
Research Triangle Park, NC 27709
United States of America
Email: carunach@cisco.com