Internet Engineering Task Force                                 P. Dawes
Internet-Draft                                            Vodafone Group
Intended status: Informational                            C. Arunachalam
Expires: January 8, 2017                                   Cisco Systems
                                                            July 7, 2016

           Requirements for Marking SIP Messages to be Logged


   SIP networks use signalling 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 signalling will take between clients, and
   therefore impractical to monitor SIP signalling end-to-end.

   This draft describes 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 marking will typically be applied as
   part of network testing controlled by the network operator and not
   used in regular client signalling.  However, such 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 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
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   This Internet-Draft will expire on January 8, 2017.

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Copyright Notice

   Copyright (c) 2016 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
   ( 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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions Used in this Document . . . . . . . . . . . . . .   3
   3.  Motivating Scenario . . . . . . . . . . . . . . . . . . . . .   3
   4.  Basic Debugging Procedure . . . . . . . . . . . . . . . . . .   4
   5.  Requirements for a "Log Me" Marker  . . . . . . . . . . . . .   5
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
     6.1.  Trust Domain  . . . . . . . . . . . . . . . . . . . . . .   7
     6.2.  Security Threats  . . . . . . . . . . . . . . . . . . . .   7
       6.2.1.  "Log Me" Marking  . . . . . . . . . . . . . . . . . .   7
       6.2.2.  Sending Logged Information  . . . . . . . . . . . . .   7
   7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   7
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   Service providers who use SIP (see RFC 3261 [RFC3261]) in their
   networks need the ability to debug customer reported problems and
   also need to run regression tests if SIP client software/hardware is
   upgraded.  Such debugging and tests might be confined to a single
   service provider or network, or may occur between the administrative
   domains of service providers, including providers 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
   and this marking must be carried within the candidate SIP messages as
   they are routed across networks (and geographies) to enable logging

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   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 service providers, different countries, regions with
   different privacy requirements, and different trust domains.  This
   draft describes the requirements for such a "log me" marker for SIP

2.  Conventions Used in this Document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   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
   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 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

   The figure below gives an example of a signalling path through
   multiple networks.

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      +------------------+          +------------------+
      | 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 signalling path through multiple networks

4.  Basic Debugging Procedure

   The debugging procedure steps are outlined below.  The entire SIP
   message (SIP headers and message body) MUST be logged using the SIP
   CLF format defined in RFC 6873 [RFC6873], with Vendor-ID = 00000000
   and Tag = 02 in the <OptionalFields> portion of the SIP CLF record
   (see RFC 6873 [RFC6873] clause 4.4).  Header fields MUST be logged in
   their long form and not the compact form described in RFC 3261
   [RFC3261] clause 7.3.3.

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   o  The user's terminal is placed in debug mode.  The terminal 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 terminal connects to at the edge of the network to the
      destination client terminal, can detect that the "log me" marker
      is 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.  The definition of stop event types and the
      configuration of stop events in the SIP entity is outside the
      scope of this document.

   o  When and how signalling 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 co-ordinating debugging, by storing them on removable media for
      later manual collection, or by some other method.

5.  Requirements for a "Log Me" Marker

   o  REQ1: It MUST be possible to mark a SIP request or response as of
      interest for logging by inserting a "log me" marker.  This is
      known as "log me" marking.

   o  REQ2: It MUST be possible for a "log me" marker to cross network

   o  REQ3: A "log me" marker is most effective if it passes 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
      will not use.  A "log me" marker SHOULD be removed at trust domain

   o  REQ4: The presence of a "log me" marker indicates that a request
      or response is part of debugging or regression testing.  SIP
      entities that support "log me" marking SHOULD log SIP requests or
      responses that contain a "log me" marker."  The SIP entity checks
      for the presence of a "log me" marker and writes any request or
      response that contains a "log me" marker to a log file.

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   o  REQ5: If a UA that supports "log me" marking receives a request
      with a "log me" marker, it MUST echo that "log me" marker in
      responses to that request.

   o  REQ6: A SIP proxy MAY insert a "log me" marker into requests and
      responses.  The typical case for which a proxy needs to insert a
      "log me" marker is for compatibility with UAs that have not
      implemented "logme" 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.  In these cases,
      the entity that inserts a "log me" marker is stateful inasmuch as
      it must remember when a dialog is of interest for logging.  An
      entity that inserts a "log me" marker SHOULD also log the SIP
      request or response as per REQ4.

   o  REQ7: SIP proxies MAY be stateless in terms of logging of SIP
      requests that contain a "log me" marker, i.e. they MAY base the
      decision to log a SIP request or response solely on the presence
      of the "log me" marker.  For example, it is OPTIONAL for a SIP
      entity to maintain state of which SIP requests contained a "log
      me" marker in order to log responses to those requests.  Echoing a
      "log me" marker in responses is the responsibility of the UA that
      receives a request.

   o  REQ8: 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 by the debugging server to collate all
      logged SIP requests and responses to the initial SIP request in a
      dialog or standalone transaction.  The Session-ID described in RFC
      7206 [RFC7206] and I-D.ietf-insipid-session-id-12
      [I-D.ietf-insipid-session-id] could be used as the test case
      identifier but it would be useful for the UA to log a human
      readable name together with this Session-ID when it performs "log
      me" marking of an initial SIP request.

   o  REQ9: "log me" marking of requests and responses MUST be applied
      on a per-dialog granularity.  If applied, "log me" marking MUST
      begin with the dialog-creating request and SHOULD continue to the
      dialog end. "log me" marking MUST NOT be stopped and re-started on
      a given dialog.

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

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   adversely affect a network.  This section analyses how to meet these

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 next hop network then the "log me" marker
   might not be removed.

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 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.

   Activating a debug mode affects the operation of a terminal,
   therefore debugging configuration must be supplied by an authorized
   server to an authorized terminal, debugging configuration must not be
   altered in transit, and must not be readable by an unauthorized third

   Logged signalling is privacy-sensitive data, therefore signalling
   logs must be passed to an authorized server, must not be altered in
   transit, and must not be readable by an unauthorized third party.

6.2.2.  Sending Logged Information

   A SIP entity that has logged information should encrypt it, such that
   it can be decrypted only by the debug server, before sending it to a
   debug server in order to protect the content of logs from a third

7.  Acknowledgments

   The authors wish to thank Jorgen Axell, Keith Drage, Vijay Gurbani,
   Christer Holmberg, Hadriel Kaplan, Paul Kyzivat, James Polk, and
   Gonzalo Salgueiro for their constructive comments and guidance while
   developing this document.

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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,

   [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,

8.2.  Informative References

              Jones, P., Polk, J., Salgueiro, G., and C. Pearce, "End-
              to-End Session Identification in IP-Based Multimedia
              Communication Networks", draft-ietf-insipid-session-id-12
              (work in progress), January 2015.

   [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,

   [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,

Authors' Addresses

   Peter Dawes
   Vodafone Group
   The Connection
   Newbury, Berkshire  RG14 2FN


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   Chidambaram Arunachalam
   Cisco Systems
   7200-12 Kit Creek Road
   Research Triangle Park, NC, NC  27709


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