[Docs] [txt|pdf] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits] [IPR]

Versions: (draft-jones-insipid-session-id) 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 RFC 7989

Network Working Group                                           P. Jones
Internet Draft                                                 C. Pearce
Intended status: Standards Track                                 J. Polk
Expires: September 12, 2013                                 G. Salgueiro
                                                           Cisco Systems
                                                          March 12, 2013



         End-to-End Session Identification in IP-Based Multimedia
                          Communication Networks
                     draft-ietf-insipid-session-id-00


Abstract

   This document describes an end-to-end Session Identifier for use in
   IP-based Multimedia Communication systems that enables endpoints,
   intermediate devices, and management systems to identify a session
   end-to-end, associate multiple endpoints with a given multipoint
   conference, track communication sessions when they are redirected,
   and associate one or more media flows with a given communication
   session.

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   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."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html

   This Internet-Draft will expire on September 12, 2013.





Jones, et al.         Expires September 12, 2013                [Page 1]


Internet-Draft          End-To-End Session ID                 March 2013


Copyright Notice

   Copyright (c) 2013 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...................................................2
   2. Conventions used in this document..............................3
   3. Session Identifier Requirements and Use Cases..................3
   4. Constructing the Session Identifier............................4
   5. Transmitting the Session Identifier in SIP.....................5
   6. Endpoint Behavior..............................................5
   7. Processing by Intermediaries...................................6
   8. Associating Endpoints in a Multipoint Conference...............7
   9. Various Call Flow Operations Utilizing the Session ID..........7
      9.1. Basic Session-ID Construction with 2 UUIDs................8
      9.2. Basic Call Transfer using REFER...........................9
      9.3. Basic Call Transfer using reINVITE.......................10
      9.4. Single Focus Conferencing................................11
      9.5. Single Focus Conferencing using WebEx....................13
      9.6. Cascading Conference Bridge Support for the Session-ID...14
      9.7. Basic 3PCC for two UAs...................................15
   10. Compatibility with a Previous Implementation.................16
   11. Security Considerations......................................17
   12. IANA Considerations..........................................18
      12.1. Registration of the "Session-ID" Header Field...........18
      12.2. Registration of the "remote" Parameter..................18
   13. Acknowledgments..............................................18
   14. References...................................................18
      14.1. Normative References....................................18
      14.2. Informative References..................................19
   Author's Addresses...............................................20


1. Introduction

   IP-based multimedia communication systems like SIP [1] and H.323 [2]
   have the concept of a "call identifier" that is globally unique.  The


Jones, et al.         Expires September 12, 2013               [Page 2]


Internet-Draft          End-To-End Session ID                 March 2013


   identifier is intended to represent an end-to-end communication
   session from the originating device to the terminating device.  Such
   an identifier is useful for troubleshooting, session tracking, and so
   forth.

   Unfortunately, there are a number of factors that contribute to the
   fact that the current call identifiers defined in SIP and H.323 are
   not suitable for end-to-end session identification.  A fundamental
   issue in protocol interworking is the fact that the syntax for the
   call identifier in SIP and H.323 is different between the two
   protocols.  This important fact makes it impossible for call
   identifiers to be exchanged end-to-end when a network utilizes one or
   more session protocols.

   Another reason why the current call identifiers are not suitable to
   identify the session end-to-end is that in real-world deployments
   devices like session border controllers often change the session
   signaling as it passes through the device, including the value of the
   call identifier.  While this is deliberate and useful, it makes it
   very difficult to track sessions end-to-end.

   This draft presents a new identifier, referred to as the Session
   Identifier, or "Session ID", and associated syntax intended to
   overcome the issues that exist with the currently defined call
   identifiers.  The proposal in this document attempts to comply with
   the requirements specified in [9]. This proposal also has
   capabilities not mentioned in [5], shown in call flows in section 10.
   Additionally, this proposal attempts to account for a previous,
   proprietary version of a SIP Session ID header, proposing a backwards
   compatibility of sorts, described in section 11.

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 RFC 2119 [3] when they
   appear in ALL CAPS.  These words may also appear in this document in
   lower case as plain English words, absent their normative meanings.

3. Session Identifier Requirements and Use Cases

   Requirements and Use Cases for the end-to-end Session Identifier can
   be found in a separate memo titled "Requirements for an End-to-End
   Session Identification in IP-Based Multimedia Communication Networks"
   [9].






Jones, et al.         Expires September 12, 2013               [Page 3]


Internet-Draft          End-To-End Session ID                 March 2013


4. Constructing the Session Identifier

   The Session Identifier is comprised of two RFC 4122 defined UUIDs
   [4], with each UUID representing one of the endpoints participating
   in the session.  The SIP user agent (UA) initially transmitting the
   SIP request will create a UUID and transmit that to the ultimate
   destination UA.  Likewise, the responding UA will create a UUID and
   transmit that to the first UA.  These two distinct UUIDs form what is
   referred to as the Session Identifier and is represented in this
   document in set notation of the form {A,B}, where A is UUID value
   from the UA transmitting a message and B is the UUID value from the
   intended recipient of the message, i.e., not an intermediary server
   along the signaling path.  The set {A,B} is equal to the set {B,A},
   and thus both represent the same Session Identifier.

   In the case where only one UUID is known, such as when a UA first
   initiates a SIP request, the Session ID would be {A}, where "A"
   represents the single UUID value transmitted.

   Since SIP sessions are subject to any number of service interactions,
   SIP INVITE messages might be forked as sessions are established, and
   since conferences might be established or expanded with endpoints
   calling in or the conference focus calling out, the construction of
   the Session Identifier from a set of UUIDs is important.

   To understand this better, consider that a UA participating in a
   communication session might be replaced with another, such as the
   case where two "legs" of a call are joined together by a PBX.
   Suppose that UA A and UA B both call UA C.  Further suppose that UA C
   uses a local PBX function to join the call between itself and UA A
   with the call between itself and UA B.  This merged call needs to be
   identified and identification of such sessions is natural and easily
   traceable when utilizing UUID values assigned by each entity in the
   communication session.

   In the case of forking, UA A might send an INVITE that gets forked to
   five different UAs, as an example.  Until one UA returns a 200 OK to
   the initial INVITE, a means of identifying each of these separate
   communication sessions is needed and allowing the set of {A, B1}, {A,
   B2}, {A, B3}, {A, B4}, and {A, B5} makes this possible.

   For conferencing scenarios, it is also useful to have a two-part
   Session-ID where the conference focus specifies one UUID.  This might
   allow for correlation among the participants in a single conference,
   for example.

   How a device acting on Session Identifiers stores, processes, or
   utilizes the Session Identifier is outside the scope of this
   document.


Jones, et al.         Expires September 12, 2013               [Page 4]


Internet-Draft          End-To-End Session ID                 March 2013


5. Transmitting the Session Identifier in SIP

   Each session initiated or accepted MUST have a local UA-generated
   UUID associated with the session.  This value MUST remain unchanged
   throughout the duration of that session.

   A SIP UA MUST convey its Session Identifier UUID in all transmitted
   messages within the same session.  To do this, each transmitted
   message MUST include the "Session-ID" header.  The Session-ID header
   has the following ABNF [5] syntax:

     session-id    = "Session-ID" HCOLON local-uuid

                     *(SEMI sess-id-param)

     local-uuid    = sess-uuid

     remote-uuid   = sess-uuid

     sess-uuid     = 32(DIGIT / %x61-66)  ;32 chars of [0-9a-f]

     sess-id-param = remote-param / generic-param

     remote-param  = "remote" EQUAL remote-uuid

   The productions "SEMI", "EQUAL", and "generic-param" production is
   defined in RFC 3261.  The production DIGIT is defined in RFC 5234.

   The Session-ID header MUST NOT have more than one "remote" parameter.

   The "local-uuid" in the Session-ID header represents the UUID value
   of the UA transmitting the message.  If the UA transmitting the
   message previously received a UUID value from its peer endpoint, it
   MUST include that UUID as the "remote" parameter.  For example, using
   the UUID values from the previous section, a Session-ID header might
   appear like this:

     Session-ID: aeffa652b22911dfa81f12313a006823;
                 remote=be11afc8b22911df86c412313a006823

   The UUID values are presented as strings of lower-case hexadecimal
   characters, with the most significant byte of the UUID appearing
   first.

6. Endpoint Behavior

   To comply with this specification, SIP UAs MUST include a Session-ID
   header-value in all messages transmitted as a part of a communication
   session.


Jones, et al.         Expires September 12, 2013               [Page 5]


Internet-Draft          End-To-End Session ID                 March 2013


   A non-intermediary UAS that receives a Session-ID header MUST take
   note of the first UUID value that it receives in the Session-ID
   header and assume that that is the UUID of the peer endpoint within
   that communications session.  UAs MUST include this received UUID
   value as the "remote" parameter when transmitting subsequent
   messages.

   It should be noted that messages received by a UA might contain a
   "remote" parameter that does match the UAs UUID.  This might happen
   as a result of service interactions by intermediaries and MUST NOT be
   regarded as an error.

   For any purpose the UA has for the Session-ID, it MUST assume that
   the Session-ID is {A,B} where "A" is the UUID value of this endpoint
   and "B" is the UUID value of the peer endpoint, taken from the most
   recently received message within this session.

   An endpoint MUST assume that the UUID value of the peer UA MAY change
   at any time due to service interactions.  However, once an UA
   allocates a UUID value for a communication session, the UA MUST NOT
   change that UUID value for the duration of the session, including
   when communication attempts are retried due to receipt of 4xx
   messages, when the session is redirected in response to a 3xx
   message, or when a session is transferred via a REFER message [7].

   It is also important to note that if a session is forked by an
   intermediary in the network, the initiating UA may receive multiple
   responses back from different endpoints, each of which will contain a
   different UUID value.  UAs MUST take care to ensure that the correct
   UUID value is returned in the "remote" parameter when responding to
   those endpoints.

7. Processing by Intermediaries

   Intermediaries that wish to utilize the Session-ID MAY extract the
   UUID header-values from any SIP message.  Alternatively,
   intermediaries MAY observe the first UUID value in the Session-ID
   header for messages sent in each direction and use those values to
   locally construct the Session Identifier.

   Intermediaries MUST NOT alter the UUID values found in the Session-ID
   header, except as described in this section.

   Intermediary devices that transfer a call, such as by joining
   together two different "call legs", MUST properly construct a
   Session-ID header that contains the correct UUID values and correct
   placement of those values.  As described above, the recipient of any
   message initiated by the intermediary will assume that the first UUID
   value belongs to the peer endpoint.


Jones, et al.         Expires September 12, 2013               [Page 6]


Internet-Draft          End-To-End Session ID                 March 2013


   If a SIP message having no Session-ID header is received by an
   intermediary, the intermediary MAY assign a "local-uuid" value to
   represent the sending endpoint and insert that value into all
   signaling messages on behalf of the sending endpoint.  If the
   intermediary is aware of a "remote" value that identifies the
   receiving UA, it MUST insert that value if also inserting the "local-
   uuid" value.

   Devices that initiate communication sessions following the procedures
   for third party call control MUST fabricate a UUID value that will be
   utilized only temporarily.  Once the responding endpoint provides a
   UUID value in a response message, the temporary value MUST be
   discarded and replaced with the endpoint-provided UUID value.  Refer
   to the third-party call control example for an illustration.

   Whenever there is a UA that does not implement this specification
   communicating through a B2BUA, the B2BUA MAY become dialog stateful
   and insert a UUID value into the Session-ID header on behalf of the
   UA according to the rules stated in Section 6.

8. Associating Endpoints in a Multipoint Conference

   Multipoint Control Units (MCUs) group two or more sessions into a
   single multipoint conference.  The MCU should utilize the same UUID
   value for each session that is grouped into the same conference.  In
   so doing, each individual session in the conference will have a
   unique Session Identifier (since each endpoint will create a unique
   UUID of its own), but will also have one UUID in common with all
   other participants in the conference.

   Intermediary devices, such as proxies or session border controllers,
   or network diagnostics equipment might assume that when they see two
   or more sessions with different Session Identifiers, but with one
   UUID in common, that the sessions are part of the same conference.

   Note, however, that this assumption of being part of the same
   conference is not always true.  For example, in a SIP forking
   scenario, there might also be what appears to be multiple sessions
   with a shared UUID value.  This is actually desirable.  What is
   desired is to allow for the association of related sessions.  Whether
   sessions are related because of forking or because endpoints are
   communicating as a part of a conference does not matter.  They are
   nonetheless related.

9. Various Call Flow Operations Utilizing the Session ID

   Seeing something frequently makes understanding easier. With that in
   mind, we include several call flows with the initial UUID and the
   complete Session-ID indicated per message, as well as when the


Jones, et al.         Expires September 12, 2013               [Page 7]


Internet-Draft          End-To-End Session ID                 March 2013


   Session-ID changes according to the rules within this document during
   certain operations/functions.

9.1. Basic Session-ID Construction with 2 UUIDs

      Session-ID
         ---     Alice            B2BUA             Bob            Carol
         {A}       |----INVITE----->|                |
         {A}       |                |----INVITE----->|
        {B,A}      |                |<---200 OK------|
        {B,A}      |<---200 OK------|                |
        {A,B}      |------ACK------>|                |
        {A,B}      |                |------ACK------>|
                   |<==============RTP==============>|

             Figure 1 - Session-ID Creation when Alice calls Bob

   Operation/Rules:

     o Transmitter of SIP message places its Session-ID UUID first in
       order;

     o UA-Alice sends its UUID in INVITE;

     o B2BUA receives an INVITE with a Session-ID header-value from UA-
       Alice, and transmits INVITE towards UA-Bob with an unchanged
       Session-ID header-value;

     o UA-Bob receives Session-ID and adds its UUID to construct the
       whole/complete Session-ID header-value in the 200 OK;

     o UA-Bob orders the UUIDs such that its UUID is first when UA-Bob
       is transmitting the SIP message;

     o B2BUA receives the 200 OK response with a complete Session-ID
       header-value from UA-Bob, and transmits 200 OK towards UA-Alice
       with an unchanged Session-ID header-value; while maintaining the
       order of UUIDs in the Session-ID header-value;

     o UA-Alice, upon reception of the 200 OK from the B2BUA, transmits
       the ACK towards the B2BUA with its UUID positioned first, and
       the UUID from UA-Bob positioned second in the Session-ID header-
       value.

     o B2BUA receives the ACK with a complete Session-ID header-value
       from UA-Alice, and transmits ACK towards UA-Bob with an
       unchanged Session-ID header-value; while maintaining the order
       of UUIDs in the Session-ID header-value;



Jones, et al.         Expires September 12, 2013               [Page 8]


Internet-Draft          End-To-End Session ID                 March 2013


9.2. Basic Call Transfer using REFER

   From the example built within Section 9.1 (the basic session-ID
   establishment), we proceed to this 'Basic Call Transfer using REFER'
   example.

      Session-ID
         ---     Alice            B2BUA             Bob            Carol
                   |                |                |               |
                   |<==============RTP==============>|               |
        {B,A}      |                |<---reINVITE----|               |
        {B,A}      |<---reINVITE----| (puts Alice on Hold)           |
        {A,B}      |-----200 OK---->|                |               |
        {A,B}      |                |-----200 OK---->|               |
        {B,A}      |                |<-----ACK-------|               |
        {B,A}      |<-----ACK-------|                |               |
                   |                |                |               |
        {B,A}      |                |<----REFER------|               |
        {B,A}      |<----REFER------|                |               |
        {A,B}      |-----200 OK---->|                |               |
        {A,B}      |                |-----200 OK---->|               |
        {A,B}      |-----NOTIFY---->|                |               |
        {A,B}      |                |-----NOTIFY---->|               |
        {B,A}      |                |<----200 OK-----|               |
        {B,A}      |<----200 OK-----|                |               |
                   |                |                |               |
         {A}       |-----INVITE---->|                                |
         {A}       |                |-----INVITE-------------------->|
        {C,A}      |                |<----200 OK---------------------|
        {C,A}      |<----200 OK-----|                                |
        {A,C}      |------ACK------>|                                |
        {A,C}      |                |------ACK---------------------->|
                   |                |                |               |
                   |<======================RTP======================>|
                   |                |                |               |
        {A,B}      |-----NOTIFY---->|                |               |
        {A,B}      |                |-----NOTIFY---->|               |
        {B,A}      |                |<----200 OK-----|               |
        {B,A}      |<----200 OK-----|                |               |
        {B,A}      |                |<-----BYE-------|               |
        {B,A}      |<-----BYE-------|                |               |
        {A,B}      |-----200 OK---->|                |               |
        {A,B}      |                |-----200 OK---->|               |
                   |                |                |               |

                    Figure 2 - Call Transfer using REFER

   Operation/Rules:



Jones, et al.         Expires September 12, 2013               [Page 9]


Internet-Draft          End-To-End Session ID                 March 2013


   Starting from the existing Alice/Bob call described in Figure 1,
   which established an existing Session-ID header-value...

     o UA-Bob reINVITEs Alice to call Carol, using a REFER transaction,
       as described in [RFC3515]. UA-Alice is initially put on hold,
       then told in the REFER who to contact with a new INVITE, in this
       case UA-Carol.

     o UA-Alice retains her UUID from the Alice-to-Bob call {A} when
       requesting a call with UA-Carol. This same UUID traverses the
       B2BUA unchanged.

     o UA-Carol receives the INVITE with a Session-ID UUID {A}, creates
       its own UUID {C}, and combines them to form a full Session-ID
       {C,A} in the 200 OK to the INVITE. This Session-ID header-value
       traverses the B2BUA unchanged towards UA-Alice.

     o UA-Alice receives the 200 OK with the Session-ID {C,A} and both
       responses to UA-Carol with an ACK, generates a NOTIFY to Bob
       with a Session-ID {A,B} indicating the call transfer was
       successful.

     o It does not matter which UA terminates the Alice-to-Bob call;
       Figure 2 shows UA-Bob doing this transaction.

9.3. Basic Call Transfer using reINVITE

   From the example built within Section 9.1 (the basic session-ID
   establishment), we proceed to this 'Basic Call Transfer using
   reINVITE' example.

   Alice is talking to Bob. Bob pushes a button on his phone to transfer
   Alice to Carol via the B2BUA (using reINVITE).

      Session-ID
         ---     Alice            B2BUA             Bob            Carol
                   |                |                |               |
                   |<==============RTP==============>|               |
                   |                |                |               |
        {B,A}      |                |<---reINVITE----|               |
        {A,B}      |                |-----200 OK---->|               |
        {B,A}      |                |<-----ACK-------|               |
                   |                |                |               |
         {A}       |                |-----INVITE-------------------->|
        {C,A}      |                |<----200 OK---------------------|
        {A,C}      |                |------ACK---------------------->|
                   |                |                |               |
                   |<======================RTP======================>|
                   |                |                |               |


Jones, et al.         Expires September 12, 2013              [Page 10]


Internet-Draft          End-To-End Session ID                 March 2013


        {B,A}      |                |<-----BYE-------|               |
        {B,A}      |<-----BYE-------|                |               |
        {A,B}      |-----200 OK---->|                |               |
        {A,B}      |                |-----200 OK---->|               |
                   |                |                |               |

                   Figure 3 - Call transfer using reINVITE

   Operation/Rules:

     o We assume the call between Alice and Bob from Section 9.1 is
       operational with Session-ID {A,B}.

     o Bob sends a reINVITE to Alice to transfer her to Carol.

     o The B2BUA intercepts this reINVITE and sends a new INVITE with
       Alice's UUID {A} to Carol.

     o Carol receives the INVITE and accepts the request and adds her
       UUID {C} to the Session-ID for this session {C,A}.

     o Bob terminates the call (which Alice could too) with a BYE using
       their Session-ID {B,A}.

9.4. Single Focus Conferencing

   Multiple users call into a conference server (say, an MCU) to attend
   one of many conferences hosted on or managed by that server. Each
   user has to identify which conference they want to join, but this
   information is not necessarily in the SIP messaging.  It might be
   done by having a dedicated address for the conference or via an IVR,
   as assumed in this example. Each user in this example goes through a
   two-step process of signaling to gain entry onto their conference
   call.

      Session-ID                Conference
         ---     Alice            Focus             Bob            Carol
                   |                |                |               |
                   |                |                |               |
         {A}       |----INVITE----->|                |               |
        {M1,A}     |<---200 OK------|                |               |
        {A,M1}     |-----ACK------->|                |               |
                   |<====RTP=======>|                |               |
        {M',A}     |<---reINVITE----| (to change the |               |
        {A||M'}    |-----200 OK---->|   UUID to M')  |               |
        {M',A}     |<-----ACK-------|                |               |
                   |                |                |               |
                   |                |                |               |
         {B}       |                |<----INVITE-----|               |


Jones, et al.         Expires September 12, 2013              [Page 11]


Internet-Draft          End-To-End Session ID                 March 2013


        {M2,B}     |                |-----200 OK---->|               |
        {B,M2}     |                |<-----ACK-------|               |
                   |                |<=====RTP======>|               |
       {M'||B}     | (to change the |----reINVITE--->|               |
       {B||M'}     |   UUID to M')  |<----200 OK-----|               |
       {M'||B}     |                |------ACK------>|               |
                   |                |                |               |
                   |                |                |               |
         {C}       |                |<--------------------INVITE-----|
        {M3,C}     |                |---------------------200 OK---->|
        {C,M3}     |                |<---------------------ACK-------|
                   |                |<=====================RTP======>|
       {M'||C}     | (to change the |--------------------reINVITE--->|
       {C||M'}     |   UUID to M')  |<--------------------200 OK-----|
       {M'||C}     |                |----------------------ACK------>|

                  Figure 4 - Single Focus Conference Bridge

   Operation/Rules:

   Alice calls into a conference server to attend a certain conference.
   This is a two-step operation since Alice cannot include the
   conference ID and any passcode in the INVITE.

     o Alice sends an INVITE to the conference server with her UUID
       {A}.

     o The conference server accepts using a generic, temporary UUID
       {M1}.

     o Once Alice, the user, gains access to the IVR for this
       conference server, she enters a specific conference ID and
       whatever passcode (if needed) to enter a specific conference
       call.

     o Once the conference server is satisfied Alice has identified
       which conference she wants to attend (including any passcode
       verification), the conference server reINVITEs Alice to the
       specific conference and includes the UUID {M'} for that
       conference. All valid participants in the same conference will
       receive this same UUID for identification purposes and to better
       enable monitoring, and tracking functions.

     o Bob goes through this two-step process of an INVITE transaction,
       followed by a reINVITE transaction to get this same UUID for
       that conference.





Jones, et al.         Expires September 12, 2013              [Page 12]


Internet-Draft          End-To-End Session ID                 March 2013


     o In this example, Carol (and each additional user) goes through
       the same procedures and steps as Alice to get on this same
       conference.

9.5. Single Focus Conferencing using WebEx

   Alice, Bob and Carol call into same Webex conference.

      Session-ID                Conference
         ---     Alice            Focus             Bob            Carol
                   |                |                |               |
                   |<** HTTPS *****>|                |               |
                   |  Transaction   |                |               |
                   |                |                |               |
         {M}       |<----INVITE-----|                |               |
        {A||M}     |-----200 OK---->|                |               |
        {M||A}     |<-----ACK-------|                |               |
                   |<=====RTP======>|                |               |
                   |                |                |               |
                   |                |<** HTTPS *****>|               |
                   |                |  Transaction   |               |
                   |                |                |               |
         {M}       |                |-----INVITE---->|               |
        {B||M}     |                |<----200 OK-----|               |
        {M||B}     |                |------ACK------>|               |
                   |                |<=====RTP======>|               |
                   |                |                |               |
                   |                |<****************** HTTPS *****>|
                   |                |                   Transaction  |
                   |                |                |               |
         {M}       |                |--------------------INVITE----->|
        {C||M}     |                |<-------------------200 OK------|
        {M||C}     |                |---------------------ACK------->|
                   |                |<====================RTP=======>|

                  Figure 5 - Single Focus Webex Conference

   Operation/Rules:

     o Alice communicates with Webex server with desire to join a
       certain meeting, by meeting number; also includes UA-Alice's
       contact information (phone number or URI).

     o Conference Focus server sends INVITE to UA-Alice to start
       session with the Session-ID of that server for this A/V
       conference call.

     o Bob and Carol perform same function to join this same A/V
       conference call as Alice.


Jones, et al.         Expires September 12, 2013              [Page 13]


Internet-Draft          End-To-End Session ID                 March 2013


9.6. Cascading Conference Bridge Support for the Session-ID

   {Editor's note: this section describes some unique behavior.
   Motivating text needs to be added following working group
   discussion.}

   To expand conferencing capabilities requires cascading conference
   bridges. A conference bridge, or MCU, needs a way to identify itself
   when contacting another MCU. RFC 4579 [6] defines the 'isfocus'
   Contact: header parameter just for this purpose.

   Cascading MCUs for the purpose of having each use the same UUID (aka
   half the Session-ID), in its simplest form, is one MCU informing
   another which UUID to use for joining UAs.

      Session-ID
         ---     MCU-1            MCU-2            MCU-3           MCU-4
                   |                |                |               |
         {M'}      |----INVITE----->|                |               |
         {M'}      |<---200 OK------|                |               |
         {M'}      |-----ACK------->|                |               |

          Figure 6 - MCUs Communicating Session-ID UUID for Bridge

   Regardless of which MCU (1 or 2) a UA contacts for this conference,
   once the above exchange has been received and acknowledged, the UA
   will get the same M' UUID from the MCU for the complete Session-ID.

   A more complex form would be a series of MCUs all being informed of
   the same UUID to use for a specific conference. This series of MCUs
   can either be informed

     o All by one MCU (that initially generates the UUID for the
       conference),

     o The one MCU that generates the UUID informs one or several MCUs
       of this common UUID, and they inform downstream MCUs of this
       common UUID each will be using for this one conference, or

      Session-ID
         ---     MCU-1            MCU-2            MCU-3           MCU-4
                   |                |                |               |
         {M'}      |----INVITE----->|                |               |
         {M'}      |<---200 OK------|                |               |
         {M'}      |-----ACK------->|                |               |
                   |                |                |               |
         {M'}      |---------------------INVITE----->|               |
         {M'}      |<--------------------200 OK------|               |
         {M'}      |----------------------ACK------->|               |


Jones, et al.         Expires September 12, 2013              [Page 14]


Internet-Draft          End-To-End Session ID                 March 2013


                   |                |                |               |
         {M'}      |-------------------------------------INVITE----->|
         {M'}      |<------------------------------------200 OK------|
         {M'}      |--------------------------------------ACK------->|

       Figure 7 - MCU Communicating Session-ID UUID to More than One

   Operation/Rules:

     o The MCU generating the Session-ID UUID communicates this in a
       separate INVITE, having a Contact header with the 'isfocus'
       header parameter. This will identify the MCU as what RFC 4579
       conference-aware SIP entity.

     o The MCU that is contacted, i.e., the UAS MCU, does not populate
       or complete the Session-ID header value. The UAS MCU transmits a
       200 OK response acknowledging it is to respond with this M' UUID
       to all requests for the designated conference.

     o An MCU that receives this M' UUID in an inter-MCU transaction,
       can communicate the M' UUID in a manner in which it was received
       (though this time this second MCU would be the UAC MCU), unless
       local policy dictates otherwise.

9.7. Basic 3PCC for two UAs

   External entity sets up call to both Alice and Bob for them to talk
   to each other.

      Session-ID
         ---     Alice            B2BUA             Bob            Carol
                   |                |                |
         {X}       |<----INVITE-----|                |
        {A,X}      |-----200 OK---->|                |
         {A}       |                |----INVITE----->|
        {B,A}      |                |<---200 OK------|
        {A,B}      |<-----ACK-------|                |
        {A,B}      |                |------ACK------>|
                   |<==============RTP==============>|

            Figure 8 - 3PCC initiated call between Alice and Bob

   Operation/Rules:

     o Some out of band procedure directs a B2BUA (or other SIP server)
       to have Alice and Bob talk to each other.

     o The SIP server INVITEs Alice to a session and uses a temporary
       UUID {X}.


Jones, et al.         Expires September 12, 2013              [Page 15]


Internet-Draft          End-To-End Session ID                 March 2013


     o Alice receives and accepts this call set-up and includes her
       UUID {A} in the Session-ID, now {A,X}.

     o The SIP server uses Alice's UUID {A}, and discards its own {X}
       to INVITE Bob to the session as if this came from Alice
       originally.

     o Bob receives and accepts this INVITE and adds his own UUID {B}
       to the Session-ID, now {B,A} for the response.

     o And the session is established.

10. Compatibility with a Previous Implementation

   There is a much earlier and proprietary document that specifies the
   use of a Session-ID header that we will herewith attempt to achieve
   backwards compatibility. Neither Session-ID has any versioning
   information, so merely adding that this document describes "version
   2" is insufficient. Here are the set of rules for compatibility
   between the two specifications. For the purposes of this discussion,
   we will label the proprietary specification of the Session-ID as the
   "old" version and this specification as the "new" version of the
   Session-ID.

   The previous (i.e., "old") version only has a single value as a
   Session-ID, but has a generic-parameter value that can be of use.

   In order to have an "old" version talk to an "old" version
   implementation, nothing needs to be done as far as the IETF is
   concerned.

   In order to have a "new" version talk to a "new" version
   implementation, both implementations need to following this document
   (to the letter) and everything should be just fine.

   In order to have an "old" version talk to a "new" version
   implementation, several aspects need to be looked at. They are:

     o The "old" version UA will include a single UUID as its Session-
       ID.

     o The "new" version UA will respond by including a complete
       Session-ID with two UUIDs, with the "new" version's UUID listed
       first (because it cannot know it is talking with an "old"
       version implementation at this point).

     o The "old" version UA will have to ignore the first UUID, and
       consider its singular "old" UUID as valid, as long as the value
       does not change..


Jones, et al.         Expires September 12, 2013              [Page 16]


Internet-Draft          End-To-End Session ID                 March 2013


     o During subsequent transactions within this session, the "new"
       version may receive SIP requests without its UUID, but with the
       "old" version's UUID. The "new" version UA MUST add its UUID to
       the received Session-ID. The "old" version implementation will
       merely disregard it each time it receives this "new" version
       UUID (if it was not the first UUID).

   In order to have a "new" version talk to an "old" Version
   implementation, several aspects need to be looked at. They are:

     o The "new" version UA will include a single UUID as its initial
       Session-ID header always, not knowing which version of UA it is
       communicating with.

     o The "old" version UA will respond by seeing the UUID as a valid
       and complete Session-ID and not include another UUID or generic-
       param.  Thus, the 200 OK will not include any Session-ID part of
       its own from the "old" version implementation.

     Rule: implementation supporting a "new" version of the Session-ID
       MUST NOT error or otherwise reject receiving only its own UUID
       back in any transaction. It MUST interpret this response to mean
       that it is communicating with an "old" Session-ID
       implementation.

     o Open question - how do we want all intermediaries and/or
       monitoring systems to interpret this single UUID complete
       Session-ID?

11. Security Considerations

   When creating a UUID value, endpoints SHOULD ensure that there is no
   user or device-identifying information contained within the UUID.  In
   some environments, though, use of a MAC address, which is one option
   when constructing a UUID, may be desirable, especially in some
   enterprise environments.  When communicating over the Internet,
   though, the UUID value MUST utilize random values.

   The Session-ID might be utilized for logging or troubleshooting, but
   MUST NOT be used for billing purposes. { Why does this matter? }

   Other considerations???









Jones, et al.         Expires September 12, 2013              [Page 17]


Internet-Draft          End-To-End Session ID                 March 2013


12. IANA Considerations

12.1. Registration of the "Session-ID" Header Field

   The following is the registration for the 'Session-ID' header field
   to the "Header Name" registry at http://www.iana.org/assignments/sip-
   parameters:

   RFC number: RFC XXXX

   Header name: 'Session-ID'

   Compact form: none

   [RFC Editor: Please replace XXXX in this section and the next with
   the this RFC number of this document.]

12.2. Registration of the "remote" 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       | remote         | No                | [RFCXXXX] |
   +------------------+----------------+-------------------+-----------+

13. Acknowledgments

   The authors would like to than Hadriel Kaplan, Christer Holmberg, and
   Paul Kyzivat for their invaluable comments during the development of
   this document.

   This document was prepared using 2-Word-v2.0.template.dot.

14. References

14.1. Normative References

   [1]   Rosenberg, J., et al., "SIP: Session Initiation Protocol", RFC
         3261, June 2002.

   [2]   Recommendation ITU-T H.323, "Packet-based multimedia
         communications systems", December 2009.

   [3]   Bradner, S., "Key words for use in RFCs to Indicate Requirement
         Levels", BCP 14, RFC 2119, March 1997.


Jones, et al.         Expires September 12, 2013              [Page 18]


Internet-Draft          End-To-End Session ID                 March 2013


   [4]   Leach, P., Mealling, M., Salz, R., "A Universally Unique
         IDentifier (UUID) URN Namespace", RFC 4122, July 2005.

   [5]   Crocker, D., Overell, P, "Augmented BNF for Syntax
         Specifications: ABNF", RFC 5234, January 2008.

   [6]   Johnston, A., Levin, O., "Session Initiation Protocol (SIP)
         Call Control - Conferencing for User Agents", RFC 4579, August
         2006.

14.2. Informative References

   [7]   Sparks, R., "The Session Initiation Protocol (SIP) Refer
         Method", RFC 3515, April 2003.

   [8]   Schulzrinne, H., et al., "RTP: A Transport Protocol for Real-
         Time Applications", RFC 3550, July 2003.

   [9]   Jones, et al., "Requirements for an End-to-End Session
         Identification in IP-Based Multimedia Communication Networks",
         draft-ietf-insipid-session-id-reqts-05, February 2013.






























Jones, et al.         Expires September 12, 2013              [Page 19]


Internet-Draft          End-To-End Session ID                 March 2013


Author's Addresses

   Paul E. Jones
   Cisco Systems, Inc.
   7025 Kit Creek Rd.
   Research Triangle Park, NC 27709
   USA

   Phone: +1 919 476 2048
   Email: paulej@packetizer.com
   IM: xmpp:paulej@packetizer.com


   Chris Pearce
   Cisco Systems, Inc.
   2300 East President George Bush Highway
   Richardson, TX 75082
   USA

   Phone: +1 972 813 5123
   Email: chrep@cisco.com
   IM: xmpp:chrep@cisco.com


   James Polk
   Cisco Systems, Inc.
   3913 Treemont Circle
   Colleyville, Texas
   USA

   Phone: +1 817 271 3552
   Email: jmpolk@cisco.com
   IM: xmpp:jmpolk@cisco.com


   Gonzalo Salgueiro
   Cisco Systems, Inc.
   7025 Kit Creek Rd.
   Research Triangle Park, NC 27709
   USA

   Phone: +1 919 392 3266
   Email: gsalguei@cisco.com
   IM: xmpp:gsalguei@cisco.com







Jones, et al.         Expires September 12, 2013              [Page 20]


Html markup produced by rfcmarkup 1.129d, available from https://tools.ietf.org/tools/rfcmarkup/