Marking SIP Messages to be Logged
draft-ietf-insipid-logme-marking-01
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Internet Engineering Task Force P. Dawes
Internet-Draft Vodafone Group
Intended status: Standards Track August 28, 2014
Expires: March 1, 2015
Marking SIP Messages to be Logged
draft-ietf-insipid-logme-marking-01
Abstract
SIP networks use signalling monitoring tools to diagnose user
reported problems and for regression testing if network or user agent
software is upgraded. As networks grow and become interconnected,
including connection via transit networks, it becomes impractical to
predict the path that SIP signalling will take between user agents,
and therefore impractical to monitor SIP signalling end-to-end.
This document describes an indicator for the SIP protocol which can
be used to mark signalling as of interest to logging. Such marking
will typically be applied as part of network testing controlled by
the network operator and not used in regular user agent signalling.
However, such marking can be carried end-to-end including the SIP
user agents, even if a session originates and terminates in different
networks.
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 March 1, 2015.
Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved.
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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
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 . . . . . . . . . . . . . . . . . . . . 3
3. Motivating Scenario . . . . . . . . . . . . . . . . . . . . . 3
4. Skeleton Diagnostic Procedure . . . . . . . . . . . . . . . . 4
5. Protocol for Log-Me Marking . . . . . . . . . . . . . . . . . 5
5.1. Configuration for Log-Me Marking . . . . . . . . . . . . 5
5.2. Starting and Stopping Log-Me Marking . . . . . . . . . . 5
5.3. End Points of Log-Me Marking . . . . . . . . . . . . . . 6
5.3.1. Originating and Terminating User Agent . . . . . . . 6
5.3.2. Originating Edge Proxy and Terminating Edge Proxy . . 7
5.4. Maintaining State . . . . . . . . . . . . . . . . . . . . 7
5.5. Missing Log-me Marker in Dialog Being Logged . . . . . . 9
5.6. Logging Multiple Simultaneous Dialogs . . . . . . . . . . 10
5.7. Forked Requests . . . . . . . . . . . . . . . . . . . . . 10
5.8. B2BUA Handling of Log-Me Marked Dialogs . . . . . . . . . 10
5.8.1. All B2BUA Roles . . . . . . . . . . . . . . . . . . . 10
5.8.2. Proxy-B2BUA . . . . . . . . . . . . . . . . . . . . . 10
5.8.2.1. Terminating Behaviour . . . . . . . . . . . . . . 10
5.8.3. Signaling-only and SDP-Modifying Signaling-only . . . 11
5.8.3.1. Terminating Behaviour . . . . . . . . . . . . . . 11
5.8.3.2. Originating Behaviour . . . . . . . . . . . . . . 11
5.8.4. Media Relay, Media Aware, Media Termination . . . . . 11
5.9. 'Log-Me' Marker . . . . . . . . . . . . . . . . . . . . . 11
5.9.1. Header Field Parameter for Session-ID . . . . . . . . 11
5.9.2. Identifying Test Cases . . . . . . . . . . . . . . . 12
6. Security Considerations . . . . . . . . . . . . . . . . . . . 12
6.1. Trust Domain . . . . . . . . . . . . . . . . . . . . . . 12
6.2. Security Threats . . . . . . . . . . . . . . . . . . . . 12
6.2.1. The Log-Me Marker . . . . . . . . . . . . . . . . . . 12
6.2.2. Activating Debug . . . . . . . . . . . . . . . . . . 12
6.3. Protecting Logs . . . . . . . . . . . . . . . . . . . . . 12
7. Augmented BNF for the "debug" Parameter . . . . . . . . . . . 12
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
8.1. Registration of the "debug" Parameter . . . . . . . . . . 13
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
9.1. Normative References . . . . . . . . . . . . . . . . . . 13
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9.2. Informative References . . . . . . . . . . . . . . . . . 13
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 13
1. Introduction
If users experience problems with setting up sessions using SIP,
their service provider needs to find out why by examining the SIP
signalling. Also, if network or user agent 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
signalling 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 signalling path can provide diagnostic logging. This
document describes a solution that meets the requirements for such a
'log me' marker for SIP signalling as defined in draft-ietf-insipid-
logme-reqs [I-D.ietf-insipid-logme-reqs].
2. 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].
3. Motivating Scenario
Signalling for SIP session setup can cross several networks, and
these networks may not have common ownership and also may be in
differrent countries. If a single operator wishes to perform
regression testing or fault diagnosis end-to-end, the separate
ownership of networks that carry the signalling and the explosion in
the number of possible signalling paths through SIP entities from the
originating to the terminating user make it impractical to pre-
configure logging of an end-to-end SIP signalling of a session of
interest.
The figure below shows an example of a signalling path through
multiple networks.
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+------------------+ +------------------+
| COUNTRY A | | COUNTRY B |
| Operator A | | Operator A |
| | | |
| SIP Phones | | SIP Phones |
| | //| |
+------------------+ // +------------------+
| //
| //
,'```', // +------------------+
.`',.' `..'``',<==// | COUNTRY B |
,' Operator A `', | Operator A |
; Backbone Network ..'-------| |
', ,., .'` | PSTN phones |
'.,.`'.,,,.` `''` | |
|| +------------------+
||
\/
+------------------+
| |
| Transit Network |
| |
| |\\
+------------------+ \\
| \\
| \\
+------------------+ \\ +------------------+
| COUNTRY D | \\ | COUNTRY C |
| Operator C | \\=>| Operator B |
| | | |
| SIP Phones | | SIP Phones |
| | | |
+------------------+ +------------------+
Figure 1: Example signalling path through multiple networks
4. Skeleton Diagnostic Procedure
The skeleton diagnostic procedure is as follows:
o The user's user agent is placed in debug mode. The user agent
logs its own signalling and inserts a log me marker into SIP
requests for session setup
o All SIP entities that the signalling traverses, from the first
proxy the user agent connects to at the edge of the network to the
destination user agent, can detect that the log me marker is
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present and can log SIP requests and responses that contain the
marker if configured to do so.
o Subsequent responses and requests in the same dialog are logged.
o Logging stops, either because the dialog has ended or because a
'stop event', typically expiry of a certain amount of time,
occurred
o The user's user agent and any other SIP entity that has logged
signalling sends logs to a server that is co-ordinating
diagnostics.
5. Protocol for Log-Me Marking
This clause describes the protocol solution to the log-me
requirements described in draft-ietf-insipid-logme-reqs
[I-D.ietf-insipid-logme-reqs].
5.1. Configuration for Log-Me Marking
Configuration of a user agent or proxy to perform log-me marking can
be done in any way that is convenient to the configured entity. For
example, an XML file might be used to list conditions for starting
and stopping based on time.
<start>09:00:00</start>
<stop>09:10:00</stop>
Figure 2: Simple example log-me configuration
Logging is on a per-dialog basis and individual logs are
differentiated by their test identifier, which is defined in
Section 5.9.2 of this document. Therefore, an individual log for an
individual dialog is closed when that dialog ends. Logging is
typically done separately from regualar operation, which means that
tests can be designed to be short enough to troubleshoot quickly and
to limit the size of individual logs. If logging is configured so
that everything is logged for a specified number of minutes then
several separate dialogs might start and finish meaning that several
logs may be generated, each one distinguished by its test identifier.
5.2. Starting and Stopping Log-Me Marking
A proxy or user agent needs to determine when it needs to log-me mark
a SIP request or response. A user agent or proxy log-me marks a
request or response for two reasons: either it is configured to do so
or it has detected that a dialog is being log-me marked and maintains
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state to ensure that all requests and responses in the dialog are
log-me marked. A regression test might be configured to log-me mark
all SIP dialogs created during a given time period whereas a
troubleshooting test might be configured to mark a dialog based on
criteria specific to a reported fault. When configuration has caused
a user agent or proxy to start log-me marking requests and responses,
marking continues until the dialog ends.
5.3. End Points of Log-Me Marking
Log-me marking is initiated on a dialog creating side controlled by
configuration. The dialog terminating side detects an incoming log-
me marker and reacts accordingly.
5.3.1. Originating and Terminating User Agent
In the simplest case, an originating user agent will insert a log-me
marker in the dialog-creating SIP request and all subsequent SIP
requests within that dialog. The log-me marker is carried to the
terminating user agent and the terminating user agent echoes the log-
me marker in responses. If the terminating user agent sends an in-
dialog request on a dialog that is being log-me marked, it inserts a
log-me marker and the originating user agent echoes the log-me marker
in responses. This basic case suggests the following principles:
o The originating user agent is configured for debug
o The terminating user agent is not configured for debug and cannot
initiate log-me marking.
o The originating user agent logs its own signalling and inserts a
log me marker into the dialog-creating SIP request and subsequent
in-dialog SIP requests.
o The terminating user agent can detect 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 user agent MUST echo a log-me marker in responses
to a SIP request that included a log-me marker.
o If the terminating user agent has detected that a dialog is being
log-me marked, it inserts a log-me marker in any in-dialog SIP
requests that it sends.
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5.3.2. Originating Edge Proxy and Terminating Edge Proxy
Some user agents might not support log-me marking. In order to test
sessions involving such user agents, the log-me marker is inserted by
edge proxies on the originating and terminating sides. The log-me
marker is carried to the terminating user agent but the terminating
user agent is not able to echo the log-me marker in responses to that
request. Therefore the terminating edge proxy inserts a log-me
marker in reponses to the request. Likewise, if the terminating user
agent sends an in-dialog request, the terminating edge proxy inserts
a log-me marker and the originating edge proxy echoes the log-me
marker in responses to that request. This case suggests the
following principles:
o The originating edge proxy is configured for debug.
o The terminating edge proxy is not configured for debug and cannot
initiate log-me marking.
o The originating edge proxy logs its own signalling and inserts a
log me marker into SIP requests for session setup.
o The terminating edge proxy can detect that a dialog is of interest
to logging by the existence of a log-me marker in an incoming SIP
request.
o The terminating edge proxy MUST echo a log-me marker in responses
to a SIP request that included a log-me marker.
o If the terminating edge proxy has detected that a dialog is being
log-me marked, it inserts a log-me marker in in-dialog SIP
requests from the terminating user agent.
o The originating edge proxy echoes the log-me marker in responses
to in-dialog requests received from the terminating side.
5.4. Maintaining State
If a proxy inserts a log-me marker in a SIP request (because a user
agent did not) then it must ensure that a log-me marker is also
inserted in responses to that request. A proxy on the terminating
side that receives a SIP reqeust with a log-me marker may also ensure
that responses to that requset contain a log-me marker by inserting
one if the terminating user agent did not. Entities that perform
this log-me marking or checking must maintain a record of which
dialogs are being log-me marked.
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In the figure below, the edge proxy in the originating network
maintains state to ensure log-me marking of SIP requests and in the
terminating network the registrar maintains state to ensure log-me
marking of SIP responses. Such behaviour is useful for logging if
end devices do not insert or echo a log-me marker.
Alice Proxy Registrar
u1.foocorp.com p1.foocorp.com r1.foocorp.com
| | |
|(1) INVITE | |
| (u1 does not insert log-me marker in SIP request)
|----------------->| |
| |(2) INVITE |
| | 'log-me' marker
| | (p1 inserts log-me marker. p1 maintains
| | state and inserts log-me marker in all
| | requests on this dialog)
| |----------------->|
| | |(3) INVITE
| | | 'log-me' marker
| | |--------> (to barcorp)
| | |
| | |
| | |
| | |(8) 200 OK
| | | 'log-me' marker
| |(9) 200 OK |<-------- (from barcorp)
| | 'log-me' marker
| |<-----------------|
|(10) 200 OK | |
| 'log-me' marker |
|<-----------------| |
| | |
|(11) ACK | |
|--------------------------------------------------------->
| | |
Proxy Registrar Bob
p1.barcorp.com r1.barcorp.com u1.barcorp.com
| | |
(3) INVITE | |
'log-me' marker | |
----->|(from foocorp) | |
| | |
|(4) INVITE | |
| 'log-me' marker |
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|----------------->| |
| |(r1 detects that this dialog is
| | being log-me marked)
| | |
| | |
| |(5) INVITE |
| 'log-me' marker
| |----------------->|
| | |
| |(6) 200 OK |
| | (u1 does not echo LogMe:
| | to SIP response)|
| |<-----------------|
|(7) 200 OK | |
|'log-me' marker | |
| (r1 inserts log-me marker. r1 maintains
| state and inserts log-me marker in all
| responses on this dialog)
|<-----------------| |
| | |
(8) 200 OK | |
'log-me' marker | |
<----| | |
| | |
(11) ACK | |
from foocorp) -------------------------->|
| | |
| | |
| |(12) re-INVITE |
| |<-----------------|
| |(in-dialog request)
| | |
|(13) re-INVITE | |
|'log-me' marker | |
|<-----------------| |
|(r1 inserts log-me marker into in-dialog
| requests sent from the terminating user agent)
| | |
Figure 3: Maintaining state for log-me marking
5.5. Missing Log-me Marker in Dialog Being Logged
A terminating user agent or terminating edge proxy that has been
echoing markers in responses for a given dialog might receive a SIP
request that has not been log-me marked. Since log-me marking is
done per dialog, this is an error. In such cases, the proxy SHOULD
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consider log-me marking to have ended and MUST NOT mark a response to
the unmarked request, responses to subsequent requests in the dialog,
or in-dialog requests sent from the terminating side. Similarly,
log-me marking that begins mid-dialog is an error case and the
terminating user agent or edge proxy MUST NOT log-me mark responses
to the marked request, responses to subsequent requests in the
dialog, or in-dialog requests from the terminating side.
5.6. Logging Multiple Simultaneous Dialogs
An originating or terminating user agent and SIP entities on the
signaling path can log multiple SIP dialogs simultaneously, these
dialogs are differentiated by their test identifier.
5.7. Forked Requests
Log-me marking is copied into forked requests.
5.8. B2BUA Handling of Log-Me Marked Dialogs
The log-me marking behaviour of a B2BUA needs to be consistent with
its purpose of troubleshooting user problems and regression testing.
For example, a B2BUA that does no more than transcoding media can
simply copy log-me marking from UAS to UAC whereas a B2BUA that
performs varied and complex signalling tasks such as distributing
calls in a call centre needs flexible configuration so that log-me
marking can target specific B2BUA functions.
B2BUA behaviour is described below for each of the B2BUA types
described in RFC7092 [RFC7092]. Behaviour described in this clause
applies only to dialogs that are being log-me marked.
5.8.1. All B2BUA Roles
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.
5.8.2. Proxy-B2BUA
5.8.2.1. Terminating Behaviour
A Proxy-B2BUA SHOULD copy log-me marking in requests and responses
from its terminating to the originating side without needing explicit
configuration to do so.
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5.8.3. Signaling-only and SDP-Modifying Signaling-only
5.8.3.1. Terminating Behaviour
A signaling-only B2BUA SHOULD NOT copy log-me marking in requests and
responses from its terminating to its originating side. Whether a
dialog that a signaling-only B2BUA terminates causes log-me marking
of a dialog on its originating side SHOULD be controlled by explicit
configuration of the originating side, in the same way that a UAC
requires configuration to control log-me marking.
5.8.3.2. Originating Behaviour
Whether a signaling-only B2BUA log-me marks SIP requests that it
generates on its own SHOULD be controlled by explicit configuration
of the originating side, in the same way that a UAC requires
configuration to control log-me marking.
5.8.4. Media Relay, Media Aware, Media Termination
Log-me marking behaviour is independent of B2BUA media-plane
functionality. Behaviour of signaling/media plane B2BUA roles is
therefore dictated only by the signaling plane role as described in
Section 5.8.2 and Section 5.8.3 in this document.
5.9. 'Log-Me' Marker
5.9.1. Header Field Parameter for Session-ID
A new header field parameter called debug is defined to be used with
the Session-ID header field (described in draft-ietf-insipid-session-
id [I-D.ietf-insipid-session-id]).
Alice Proxy Registrar Debug Server
u1.foocorp.com p1.foocorp.com r1.foocorp.com d1.foocorp.com
| | | |
|(1) INVITE | | |
| Session-ID: ab30317f1a784dc48ff824d0d3715d86; |
| remote=47755a9de7794ba387653f2099600ef2; debug
|----------------->| | |
| | | |
Figure 4: Log-me marking using the "debug" Session-ID: header field
parameter
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5.9.2. Identifying Test Cases
The test case identifier is the Session-ID in the Session-ID header
field (described in draft-ietf-insipid-session-id
[I-D.ietf-insipid-session-id]). A log relates to exactly one dialog
and logs are distinguished by their test case identifier.
6. Security Considerations
6.1. Trust Domain
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 SHOULD be
removed at a trust domain boundary. If a prior agreement to log
sessions exists with the net hop network then the log me marker might
not be removed.
6.2. Security Threats
6.2.1. The Log-Me Marker
The log me marker is not sensitive information, although it will
sometimes be inserted because a particular device is experiencing
problems.
The presence of a log me marker will cause some SIP entities to log
signalling. Therefore, this marker MUST be removed at the earliest
opportunity if it has been incorrectly inserted.
6.2.2. Activating Debug
Activating a debug mode affects the operation of a user agent,
therefore it MUST be supplied by an authorized server to an
authorized user agent, it MUST NOT be altered in transit, and it MUST
NOT be readable by an unauthorized third party.
6.3. Protecting Logs
A SIP entity that has logged information SHOULD encrypt it, such that
it can be decrypted only by a person authorized to examine the logged
information.
7. Augmented BNF for the "debug" Parameter
ABNF is described in RFC 5234 [RFC5234]
debug-param = "debug"
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8. IANA Considerations
8.1. Registration of the "debug" Parameter
The following parameter is to be added to the "Header Field
Parameters and Parameter Values" section of the SIP parameter
registry:
+--------------+----------------+-------------------+-----------+
| Header Field | Parameter Name | Predefined Values | Reference |
+--------------+----------------+-------------------+-----------+
| Session-ID | debug | No | [RFCXXXX] |
+--------------+----------------+-------------------+-----------+
Table 1
9. References
9.1. Normative References
[I-D.ietf-insipid-logme-reqs]
Dawes, P., "Requirements for Marking SIP Messages to be
Logged", draft-ietf-insipid-logme-reqs-01 (work in
progress), July 2014.
[I-D.ietf-insipid-session-id]
Jones, P., Pearce, C., Polk, J., and G. Salgueiro, "End-
to-End Session Identification in IP-Based Multimedia
Communication Networks", draft-ietf-insipid-session-id-06
(work in progress), April 2014.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
9.2. Informative References
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008.
[RFC7092] Kaplan, H. and V. Pascual, "A Taxonomy of Session
Initiation Protocol (SIP) Back-to-Back User Agents", RFC
7092, December 2013.
Author's Address
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Peter Dawes
Vodafone Group
The Connection
Newbury, Berkshire RG14 2FN
UK
Email: peter.dawes@vodafone.com
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