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RFC 8123
Internet Engineering Task Force (IETF) P. Dawes
Request for Comments: 8123 Vodafone Group
Category: Informational C. Arunachalam
ISSN: 2070-1721 Cisco Systems
March 2017
Requirements for Marking SIP Messages to be Logged
Abstract
SIP networks use signaling monitoring tools to debug customer-
reported problems and for regression testing if network or client
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 clients and,
therefore, impractical to monitor SIP signaling end-to-end.
This document describes the requirements for adding an indicator to
the SIP Protocol Data Unit (PDU) or a SIP message that marks the PDU
as a candidate for logging. Such a marking will typically be applied
as part of network testing controlled by the network operator and not
used in regular client signaling. However, such a marking can be
carried end-to-end, including the SIP terminals, even if a session
originates and terminates in different networks.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
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). Not all documents
approved by the IESG are a candidate for any level of Internet
Standard; see 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
http://www.rfc-editor.org/info/rfc8123.
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Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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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. Conventions Used in This Document . . . . . . . . . . . . . . 3
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Network Boundary . . . . . . . . . . . . . . . . . . . . 3
3.2. Trust Domain . . . . . . . . . . . . . . . . . . . . . . 4
3.3. Intermediary . . . . . . . . . . . . . . . . . . . . . . 4
4. Motivating Scenario . . . . . . . . . . . . . . . . . . . . . 4
4.1. Introduction . . . . . . . . . . . . . . . . . . . . . . 4
4.2. Example Network Arrangement . . . . . . . . . . . . . . . 5
4.3. Example Debugging Procedure . . . . . . . . . . . . . . . 6
5. "Log Me" Marking Requirements . . . . . . . . . . . . . . . . 6
5.1. Message Logs . . . . . . . . . . . . . . . . . . . . . . 6
5.2. "Log Me" Marking . . . . . . . . . . . . . . . . . . . . 7
5.3. Processing the "Log Me" Marker . . . . . . . . . . . . . 7
6. Security Considerations . . . . . . . . . . . . . . . . . . . 8
6.1. Trust Domain . . . . . . . . . . . . . . . . . . . . . . 8
6.2. Security Threats . . . . . . . . . . . . . . . . . . . . 9
6.2.1. "Log Me" Marking . . . . . . . . . . . . . . . . . . 9
6.2.2. Logged Information . . . . . . . . . . . . . . . . . 9
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
8.1. Normative References . . . . . . . . . . . . . . . . . . 9
8.2. Informative References . . . . . . . . . . . . . . . . . 10
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
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1. Introduction
Service providers, enterprises, and others who operate networks that
use SIP (see [RFC3261]) need the ability to debug problems reported
by end users and also to run regression tests if SIP client software/
hardware is upgraded. Such debugging and testing might be confined
to a single service provider or network, or they may occur between
the administrative domains of different network operators, including
domains in different countries that are interconnected through
networks belonging to one or more third parties.
A mechanism is needed to mark particular SIP sessions, i.e., those
related to debugging or regression testing, as candidates for
logging; this marking must be carried within the candidate SIP
messages as they are routed across networks (and geographies) to
enable logging at each SIP entity without having to know in advance
the list of SIP entities through which the SIP signaling messages
will traverse. Such marking must take into account that SIP messages
might traverse different network operators, different countries,
regions with different privacy requirements, and different trust
domains. This document describes the requirements for such a "log
me" marker for SIP signaling.
2. Conventions Used in This Document
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 [RFC2119], except that
rather than describing interoperability requirements, they are used
to describe requirements to be satisfied by the "log me" marker
solution.
3. Terminology
3.1. Network Boundary
A network boundary is the part of a signaling path where messages
pass between entities that are under different administrative
control. Figure 2 in [RFC5853] shows a network boundary between the
originating gateway GW-A1 in operator A's network and the Session
Border Controller (SBC) in operator B's network. A network boundary
is significant in this document because manipulation of signaling at
the boundary could prevent end-to-end testing or troubleshooting.
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Topology hiding and protocol repair (see [RFC5853]) are two common
functions that manipulate signaling at the network boundary. These
functions are performed by SIP device types (see [RFC7092]) such as a
Session Border Controller and Interconnection Border Control Function
(IBCF).
3.2. Trust Domain
In this document, a trust domain is the set of entities that have
been identified by prior agreement as the participating elements in
logging, typically for the purpose of debugging or regression
testing. A trust domain contains all SIP entities under
configuration control of the network operator who is performing
regression testing plus all SIP entities that are under configuration
control of peer network operators who have agreed to participate in
that regression testing. The purpose of trust domain requirements is
to prevent network operators from inadvertently triggering logging in
networks that are not part of any testing or troubleshooting.
3.3. Intermediary
The term "intermediary" is defined in Section 2 of [RFC7989]; it
refers to any entity along the call signaling path.
4. Motivating Scenario
4.1. Introduction
Signaling for SIP session setup can cross several networks; these
networks may not have common ownership and may also be in different
countries. If a single operator wishes to perform regression testing
or fault debugging end-to-end, the separate ownership of networks
that carry the signaling and the explosion in the number of possible
signaling paths through SIP entities from the originating to the
terminating user make it impractical to preconfigure logging end-to-
end SIP signaling of a session of interest.
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4.2. Example Network Arrangement
The figure below gives an example of a signaling path through
multiple networks.
+------------------+ +------------------+
| COUNTRY W | | COUNTRY X |
| Operator A | | Operator A |
| | | |
| SIP Phones | | SIP Phones |
| | //| |
+------------------+ // +------------------+
| //
| //
,'```', // +------------------+
.`',.' `..'``',<==// | COUNTRY X |
,' Operator A `', | Operator A |
; Backbone Network ..'--| |
', ,., .'` | PSTN phones |
'.,.`'.,,,.` `''` | |
|| +------------------+
||
\/
+------------------+
| |
| Transit Network |
| |
| |\\
+------------------+ \\
| \\
| \\
+------------------+ \\ +------------------+
| COUNTRY Z | \\ | COUNTRY Y |
| Operator C | \\=>| Operator B |
| | | |
| SIP Phones | | SIP Phones |
| | | |
+------------------+ +------------------+
Figure 1: Example Signaling Path through Multiple Networks
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4.3. Example Debugging Procedure
One possible set of steps is outlined below to illustrate the
debugging procedure.
o The user's terminal is placed in debug mode. The terminal logs
its own signaling and inserts a "log me" marker into SIP requests
for session setup.
o All SIP entities that the signaling traverses, from the first
proxy the terminal connects to at the edge of the network to the
destination client terminal, detect that the "log me" marker is
present and then log SIP requests and responses that contain the
marker if configured to do so.
o Subsequent responses and requests in the same dialog are also
marked with a "log me" marker. For some scenarios, such as call
transfer, related dialogs may also be marked with "log me" marker.
o Logging stops, either because the dialog has ended or because a
"stop event", typically expiry of a certain amount of time,
occurred.
o Logs are retrieved, for example, by logging on to the SIP entity
or entities that contain the logs.
5. "Log Me" Marking Requirements
5.1. Message Logs
REQ1 If a SIP message is logged, then the entire SIP message (SIP
headers and message body) MUST be logged using a standard
logging format such as SIP Common Log Format (CLF) defined in
[RFC6873].
REQ2 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 as described in [RFC3261], Section 7.3.3.
When and how signaling logs are retrieved is out of scope of this
document. Logs might be retrieved by logging on to the SIP entity
that contains the logs, by sending logs to a central server that is
coordinating debugging, by storing them on removable media for later
manual collection, or by some other method. All log retrieval
mechanisms MUST adhere to the authorization and privacy protection
policies set forth by the network administrator.
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5.2. "Log Me" Marking
REQ3: It MUST be possible to mark a SIP request or response to be
considered for logging by inserting a "log me" marker. This
is known as "log me" marking.
REQ4: It MUST be possible for a "log me" marker to cross network
boundaries.
REQ5: A "log me" marker MAY include an identifier that indicates the
test case that caused it to be inserted, known as a "test case
identifier". The test case identifier does not have any
impact on session setup; it is used to collate all logged SIP
requests and responses to the initial SIP request in a dialog
or standalone transaction. The local Universally Unique
Identifier (UUID) portion of the Session-ID described in
[RFC7206] and [RFC7989] could be used as a random test case
identifier.
5.3. Processing the "Log Me" Marker
REQ6: A "log me" marker is most effective if all networks on the
signaling path agree to pass it end-to-end. However, source
networks should behave responsibly and not leave it to a
downstream network to detect and remove a marker that it is
not expecting.
REQ7: The presence of a "log me" marker indicates that a request or
response is part of debugging or regression testing.
REQ8: It MUST be possible to insert a "log me" marker in SIP
responses that correspond to SIP requests with a "log me"
marker in order to ensure that the complete SIP transaction is
logged. This requirement applies to endpoints, SIP/Public
Switched Telephone Network (PSTN) gateways, and back-to-back
user agents (B2BUAs).
REQ9: The "log me" marker mechanism SHOULD allow a SIP intermediary
to request logging SIP requests and responses on behalf of the
originating endpoint. The typical use case for this
requirement is for compatibility with User Agents (UAs) that
have not implemented "log me" marking, i.e., when a UA has not
marked a request or when responses received on a dialog of
interest for logging do not contain an echoed "log me" marker.
Another use case is when the session origination UA that
inserted the "log me" marker is no longer participating in the
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session (e.g., call transfer scenarios) and the intermediary
adds a "log me" marker in related sessions to enable end-to-
end signaling analysis.
REQ10: The mechanism MUST allow stateless processing of SIP requests
that contain a "log me" marker by SIP intermediaries. This
requirement enables the SIP intermediaries to base the
decision to log a SIP request or response solely on the
presence of the "log me" marker.
REQ11: The scope of a SIP message logging request includes all
requests and responses within a given dialog. The scope can
be extended to related dialogs that correspond to an end-to-
end session for scenarios discussed in REQ9. The "log me"
request MUST be indicated at the beginning of the dialog of
interest and SHOULD continue to the dialog end without any
stop and restart during the duration of the dialog.
REQ12: The presence of a "log me" marker might cause some SIP
entities to log signaling. Therefore, this marker MUST be
removed at the earliest opportunity if it has been incorrectly
inserted (e.g., mid-dialog or outside the configured start and
stop of "log me" marking).
The definition of types of events that cause logging to stop and the
configuration of SIP entities to detect such "stop events" is outside
the scope of this document.
6. Security Considerations
In order to prevent any security implications of a "log me" marker,
the marker itself MUST NOT contain any sensitive information,
detecting its presence or absence MUST NOT reveal sensitive
information, and maliciously adding a "log me" marker MUST NOT
adversely affect a network. This section analyzes how to meet these
requirements.
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 MUST be
removed at a trust domain boundary. If a prior agreement to log
sessions exists with the next hop network, then the "log me" marker
SHOULD NOT be removed.
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6.2. Security Threats
6.2.1. "Log Me" Marking
The "log me" marker MUST NOT convey any sensitive information,
although the "log me" marker will sometimes be inserted because a
particular device is experiencing problems. The "log me" marker MUST
NOT reveal any information related to any SIP user or device.
The insertion of the "log me" marker at the endpoint MUST be approved
by the end user or by the network administrator. Similarly, network
administrator authorization is required for a SIP intermediary to
insert a "log me" marker on behalf of a UA that does not support "log
me" marking.
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.
6.2.2. Logged Information
Logged signaling is privacy-sensitive data; therefore, signaling logs
MUST NOT be readable by an unauthorized third party.
7. IANA Considerations
This document does not require any IANA actions.
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[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,
<http://www.rfc-editor.org/info/rfc6873>.
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8.2. Informative References
[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,
<http://www.rfc-editor.org/info/rfc3261>.
[RFC5853] Hautakorpi, J., Ed., Camarillo, G., Penfield, R.,
Hawrylyshen, A., and M. Bhatia, "Requirements from Session
Initiation Protocol (SIP) Session Border Control (SBC)
Deployments", RFC 5853, DOI 10.17487/RFC5853, April 2010,
<http://www.rfc-editor.org/info/rfc5853>.
[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,
<http://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,
<http://www.rfc-editor.org/info/rfc7206>.
[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, <http://www.rfc-editor.org/info/rfc7989>.
Acknowledgments
The authors wish to thank Jorgen Axell, Ben Campbell, Keith Drage,
Vijay Gurbani, Christer Holmberg, Hadriel Kaplan, Paul Kyzivat, James
Polk, Gonzalo Salgueiro, Alberto Llamas, Brett Tate, Paul Giralt,
Stewart Bryant, Sean Turner, and Dan Romascanu for their constructive
comments and guidance while developing this document.
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Authors' Addresses
Peter Dawes
Vodafone Group
The Connection
Newbury, Berkshire RG14 2FN
United Kingdom
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
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