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rfc:rfc8123

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.

Dawes & Arunachalam Informational [Page 1] RFC 8123 Log Me" Marker March 2017

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
 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.  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

Dawes & Arunachalam Informational [Page 2] RFC 8123 Log Me" Marker March 2017

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

Dawes & Arunachalam Informational [Page 7] RFC 8123 Log Me" Marker March 2017

        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.

Dawes & Arunachalam Informational [Page 10] RFC 8123 Log Me" Marker March 2017

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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