End-to-End Session Identification in IP-Based Multimedia Communication Networks
draft-ietf-insipid-session-id-04
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 7989.
|
|
|---|---|---|---|
| Authors | Paul Jones , Chris Pearce , James Polk , Gonzalo Salgueiro | ||
| Last updated | 2014-01-24 | ||
| Replaces | draft-jones-insipid-session-id | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Formats | |||
| Reviews |
GENART Telechat review
(of
-26)
by Elwyn Davies
Almost ready
GENART Last Call review
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by Elwyn Davies
Almost ready
|
||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | WG Document | |
| Document shepherd | Keith Drage | ||
| Shepherd write-up | Show Last changed 2013-09-10 | ||
| IESG | IESG state | Became RFC 7989 (Proposed Standard) | |
| Consensus boilerplate | Yes | ||
| Telechat date | (None) | ||
| Responsible AD | Gonzalo Camarillo | ||
| Send notices to | insipid-chairs@tools.ietf.org, draft-ietf-insipid-session-id@tools.ietf.org |
draft-ietf-insipid-session-id-04
Network Working Group P. Jones (Ed.)
Internet Draft C. Pearce
Intended status: Standards Track J. Polk (Ed.)
Expires: July 24, 2014 G. Salgueiro
Cisco Systems
January 24, 2014
End-to-End Session Identification in IP-Based Multimedia
Communication Networks
draft-ietf-insipid-session-id-04
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.
This document also describes a backwards compatibility mechanism for
an existing "in the wild" implementation that is both sufficiently
different than the standard solution and whose implementation will
likely not be updated ever by some vendors.
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 July 24, 2014.
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Copyright Notice
Copyright (c) 2014 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. Session Identifier Requirements and Use Cases..................4
4. Constructing and Conveying the Session Identifier..............4
4.1. Constructing the Session Identifier.......................4
4.2. Conveying the Session Identifier..........................5
5. Transmitting the Session Identifier in SIP.....................6
6. Endpoint Behavior..............................................7
7. Processing by Intermediaries...................................8
8. Associating Endpoints in a Multipoint Conference...............9
9. Various Call Flow Operations Utilizing the Session ID.........10
9.1. Basic Session ID Construction with 2 UUIDs...............10
9.2. Basic Call Transfer using REFER..........................11
9.3. Basic Call Transfer using reINVITE.......................13
9.4. Single Focus Conferencing................................14
9.5. Single Focus Conferencing using WebEx....................16
9.6. Cascading Conference Bridge Support for the Session ID...17
9.6.1. Calling into Cascaded Conference Bridge for the Session
ID.........................................................18
9.7. Basic 3PCC for two UAs...................................19
9.8. Session ID Handling in 100 Trying SIP Response and CANCEL
Request.......................................................20
9.8.1. Session ID Handling in a 100 Trying SIP Response....20
9.8.2. Session ID in a CANCEL SIP Request..................21
9.9. Session ID in an out-of-dialog REFER Transaction.........22
10. Compatibility with a Previous Implementation.................23
11. Security Considerations......................................24
12. IANA Considerations..........................................25
12.1. Registration of the "Session-ID" Header Field...........25
12.2. Registration of the "remote" Parameter..................25
13. Acknowledgments..............................................25
14. References...................................................25
14.1. Normative References....................................25
14.2. Informative References..................................26
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Author's Addresses...............................................27
1. Introduction
IP-based multimedia communication systems like SIP [RFC3261] and
H.323 [H.323] have the concept of a "call identifier" that is
globally unique. The 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 truly 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 [I-D.ietf-insipid-session-id-reqts].
This proposal also has capabilities not mentioned in [I-D.ietf-
insipid-session-id-reqts], shown in call flows in section 9.
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 10.
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 [RFC2119]
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.
The terms "Session Identifier" and "Session ID" refer to the value of
the identifier, whereas "Session-ID" refers to the header used to
convey the identifier.
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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"
[I-D.ietf-insipid-session-id-reqts].
4. Constructing and Conveying the Session Identifier
4.1. Constructing the Session Identifier
The Session Identifier is comprised of two RFC 4122 defined UUIDs
[RFC4122], with each UUID representing one of the endpoints
participating in the session.
The version number in the UUID indicates the manner in which the UUID
is generated, such as using random values or using the MAC address of
the endpoint. To satisfy the requirement that no user or device
information be conveyed, endpoints SHOULD generate version 4 (random)
or version 5 (SHA-1) UUIDs.
When generating a version 5 UUID, endpoints or intermediaries MUST
utilize the following "name space ID" (see Section 4.3 of RFC4122):
uuid_t NameSpace_SessionID = {
/* a58587da-c93d-11e2-ae90-f4ea67801e29 */
0xa58587da,
0xc93d,
0x11e2,
0xae, 0x90, 0xf4, 0xea, 0x67, 0x80, 0x1e, 0x29
}
Further, the "name" to utilize for version 5 UUIDs is the
concatenation of the Call-ID header value and the "tag" parameter
that appears on the "From" or "To" line associated with the device
for which the UUID is created. Once an endpoint generates a UUID for
a session, the UUID never changes, even if values originally used as
input into its construction change over time.
Intermediaries that insert a Session-ID header into a SIP message on
behalf of a sending User Agent MUST utilize version 5 UUIDs to ensure
that UUIDs for the communication session are always generated with
the same values. If an intermediary does not know the tag value for
an endpoint, the intermediary MUST NOT attempt to generate a UUID for
that endpoint. Note that if an intermediary is stateless and the
endpoint on one end of the call is replaced with another endpoint due
to some service interaction, the values used to create the UUID might
change and, if so, the intermediary will compute a different UUID.
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4.2. Conveying the Session Identifier
The SIP user agent (UA) initially transmitting the SIP request, i.e.,
a User Agent Client or UAC, will create a UUID and transmit that to
the ultimate destination UA. Likewise, the responding UA, i.e., a
User Agent Server or UAS, 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. 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 Identifier 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.
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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 [RFC5234] 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 / null )
null = 32("0")
The productions "SEMI", "EQUAL", and "generic-param" are defined in
RFC 3261. The production DIGIT is defined in RFC 5234.
The Session-ID header MUST NOT have more than one "remote" parameter.
In the case where an entity compliant with this specification is
interworking with an entity that implemented [I-D.kaplan-insipid-
session-id], there might be a need to have no "remote=" parameter.
The details under which those conditions apply are described in
Section 10. In no case other than for backwards compatibility with
[I-D.kaplan-insipid-session-id] is there allowed to be no "remote="
parameter.
A valid sess-uuid value is a null value, i.e., 32 zeros. This is
expected in the "remote=" UUID of every initial standard SIP request.
This null value will get replaced by the ultimate destinations UAS
when that UA generates a UUID for the response. One caveat is
explained in Section 10 for a possible backwards compatibility case.
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 in each message it
transmits. For example, a Session-ID header might appear like this:
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Session-ID: ab30317f1a784dc48ff824d0d3715d86;
remote=47755a9de7794ba387653f2099600ef2
The UUID values are presented as strings of lower-case hexadecimal
characters, with the most significant byte of the UUID appearing
first.
A UUID having the value of all zeros is a special UUID value. It is
used in certain special cases, and hereafter is defined as the "null"
UUID value. Either the "local-uuid" field or "remote-uuid" field can
have a "null" value.
6. Endpoint Behavior
To comply with this specification, SIP UAs MUST include a Session-ID
header-value in all SIP messages transmitted as a part of a
communication session. The UUID of the transmitter of the message
MUST appear in the "local-uuid" portion of the Session-ID header-
value with one exception, mentioned below, and the UUID of the peer
device, if known, must appear as the "remote" parameter following the
transmitter's UUID.
Once a 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 or request timeouts;
- the session is redirected in response to a 3xx message; or
- a session is transferred via a REFER message [RFC3515], or when
a SIP dialog is replaced via an INVITE with Replaces [RFC3891].
The exception to including the UUID of the transmitting entity
mentioned above is in the case of provisional responses that occur
before the destination UA has generated its UUID. The 100 (Trying)
response and the 181 (Call Forwarding) response are examples of such
provisional responses. In these cases, the sending intermediary
places the one known UUID in the "remote-uuid" field, and sets the
"local-uuid" field to the "null" UUID value. This placement is always
where a UA expects to receive its UUID value in SIP responses.
A non-intermediary UA that receives a Session-ID header MUST take
note of the first UUID value (i.e., the "local-uuid") 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, making sure not to change this UUID
value in the process of moving the value internally from the "local-
uuid" field to the "remote-uuid" field.
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It should be noted that messages received by a UA might contain a
"local-uuid" parameter that does not match what the UA expected the
far end UA's UUID to be. This might happen as a result of service
interactions by intermediaries and MUST NOT negatively affect the
communication session. However, the UA may log this event for the
purposes of troubleshooting.
For any purpose the UA has for the Session Identifier, it MUST assume
that the Session Identifier is {A,B} where "A" is the UUID value of
this endpoint (i.e., "local-uuid") and "B" is the UUID value of the
peer endpoint (i.e., "remote-uuid"), taken from the most recently
received message within this session. Note that when comparing
Session Identifiers for equivalence, the identifier {A,B} is equal to
the set {B,A}.
An endpoint MUST assume that the UUID value of the peer UA MAY change
at any time due to service interactions. If the UUID value of the
peer UA changes, the UA MUST include this new UUID as the "remote"
parameter in any subsequent messages.
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 ("local-uuid") value in each response received by this
initiating UA. UAs MUST take care to ensure that the correct UUID
value is returned in the "remote" parameter when responding to those
endpoints.
Cascading MCUs all utilize the same UUID value ("local-uuid" portion
of the Session-ID header-value) for all participants of the cascaded
conference. An MCU conveys the UUID value to utilize via the "local-
uuid" portion of the Session-ID header-value in an INVITE to a second
MCU.
7. Processing by Intermediaries
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.
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
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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.
When intermediaries transmit provisional responses, such as 100
Trying, they MUST be consistent with the text in Section 6 that
discussed how endpoints are expected to receive a certain UUID value
(say, either a "local-uuid" or "remote-uuid", but not both). In
provisional responses that have not reached their destination UAS to
generate the other UUID value for that endpoint, intermediaries are
to place the UAC's UUID value in the "remote-uuid" portion of the
Session-ID header-value, and a null "local-uuid" value.
A CANCEL request sent by an intermediary that has received no
previous response from the target UA has a Session-ID constructed
exactly like the INVITE to that UA, with only a "local-uuid" value in
the Session-ID header-value.
If a SIP intermediary initiates a dialog between two UAs in a 3PCC
scenario, the SIP request in the initial INVITE will have a non-null
local-uuid value; call this UUID X. This is temporary. The request
will still have a null remote-uuid value; call this value N. The SIP
server MUST be transaction stateful. The UUID pair in the INVITE will
be {X,N}. A non-redirected or rejected response will have a UUID pair
{A,X}. This transaction stateful, dialog initiating SIP server MUST
replace its own UUID, i.e., X, with a null UUID (i.e., {A,N}) that
the UAS expects to receive (see Section 9.7 for an example).
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
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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 flow examples with the initial UUID and
the complete Session ID indicated per message, as well as when the
Session ID changes according to the rules within this document during
certain operations/functions.
This section is for illustrative purposes only and is non-normative.
In the following flows, RTP refers to the Real-time Transport
Protocol [RFC3550].
"N" represents a null UUID in those examples in this section that
have an N.
9.1. Basic Session ID Construction with 2 UUIDs
Session ID
--- Alice B2BUA Bob Carol
{A,N} |----INVITE----->| |
{A,N} | |----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
General operation of this example:
o The originating transmitter of a SIP message populates the
"local-uuid" portion of the Session-ID header-value.
o UA-Alice sends its UUID in the SIP INVITE, and populates the
"remote=" parameter with a null value (32 zeros).
o B2BUA receives an INVITE with both a "local-uuid" portion of
the Session-ID header-value from UA-Alice as well as the null
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"remote=" UUID, and transmits the INVITE towards UA-Bob with an
unchanged Session-ID header-value.
o UA-Bob receives Session-ID and generates and replaces its
"local-uuid" portion of the Session-ID header-value UUID to
construct the whole/complete Session-ID header-value, at the
same time transferring Alice's UUID unchanged to the "remote-
uuid" portion of the Session-ID header-value in the 200 OK SIP
response.
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.
o UA-Alice, upon reception of the 200 OK from the B2BUA, transmits
the ACK towards the B2BUA. The construction of the Session-ID
header-value in this ACK is that of Alice's UUID is the "local-
uuid", and Bob's UUID populates the "remote-uuid" portion of the
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.
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,N} |-----INVITE---->| |
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{A,N} | |-----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
General operation of this example:
Starting from the existing Alice/Bob call described in Figure 1 of
this document, 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. This Alice-to-Carol dialog will have a new Call-
ID, therefore it requires a new Session-ID header-value. The
wrinkle here is we can, and will, use Alice's UUID from her
existing dialog with Bob in the new INVITE to Carol.
o UA-Alice retains her UUID from the Alice-to-Bob call {A} when
requesting a call with UA-Carol. This is placed in the "local-
uuid" portion of the Session-ID header-value, at the same time
inserting a null "remote-uuid" value (because Carol's UA has not
yet received the UUID value). This same UUID traverses the B2BUA
unchanged.
o UA-Carol receives the INVITE with a Session ID UUID {A,N},
replaces the A UUID value into the "remote-uuid" portion of the
Session-ID header-value and creates its own UUID {C} and places
this value in the "local-uuid" portion of the Session-ID header-
value - thereby removing the N (null) value altogether. This
combination forms 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.
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o UA-Alice receives the 200 OK with the Session ID {C,A} and both
responds to UA-Carol with an ACK (just as in Figure 1 - switches
places of the two UUID fields), and 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======================>|
| | | |
{B,A} | |<-----BYE-------| |
{A,B} | |-----200 OK---->| |
| | | |
Figure 3 - Call transfer using reINVITE
General operation of this example:
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 (with the Session-ID "local-uuid"
= Bob's UUID and "remote-uuid" = Alice's UUID), informing her to
transfer her existing call to Carol.
o The B2BUA intercepts this reINVITE and sends a new INVITE with
Alice's UUID {"local-uuid" = "A"} to Carol.
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o Carol receives the INVITE and accepts the request and adds her
UUID {C} to the Session ID for this session {"local-uuid" = "C",
"remote-uuid" = "A"}.
o Bob terminates the call with a BYE using the Session ID {"local-
uuid" = "B", "remote-uuid" = "A"}. The B2BUA responds to Bob
since Alice and Carol are now in a new call.
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 and depicted with the use of M1, M2, and
M3. Each user in this example goes through a two-step process of
signaling to gain entry onto their conference call, which the
conference focus identifies as M'.
Session ID Conference
--- Alice Focus Bob Carol
| | | |
| | | |
{A,N} |----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,N} | |<----INVITE-----| |
{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,N} | |<--------------------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
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General operation of this example:
Alice calls into a conference server to attend a certain conference.
This is a two-step operation since Alice cannot include the
conference ID at this time and/or any passcode in the INVITE request.
The first step is Alice's UA calling another UA to participate in a
session This will appear to be similar as the call-flow in Figure 1
(in section 9.1). What is unique about this call is the second step:
the conference server calls back with a reINVITE request with its
second UUID, but maintaining the UUID Alice sent in the first INVITE.
This subsequent UUID from the conference server will be the same for
each UA that calls into this conference server participating in this
same conference bridge/call, which is generated once Alice typically
authenticates and identifies which bridge she wants to participate
on.
o Alice sends an INVITE to the conference server with her UUID {A}
and a "remote" UUID of N.
o The conference server responds with a 200 OK response which
replaces the N UUID with a temporary UUID ("M1") as the "local-
uuid" and a "remote-uuid" = "A".
NOTE: this 'temporary' UUID is a real UUID; it is only temporary
to the conference server because it knows that it is going to
generate another UUID to replace the one just send in the 200 OK.
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 Session-ID header-value of
"local-uuid" = "M'" (and "remote-uuid" = "A") 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 ("M'")
for that conference.
o In this example, Carol (and each additional user) goes through
the same procedures and steps as Alice and Bob to get on this
same conference.
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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,N} |<----INVITE-----| | |
{A,M} |-----200 OK---->| | |
{M,A} |<-----ACK-------| | |
|<=====RTP======>| | |
| | | |
| |<** HTTPS *****>| |
| | Transaction | |
| | | |
{M,N} | |-----INVITE---->| |
{B,M} | |<----200 OK-----| |
{M,B} | |------ACK------>| |
| |<=====RTP======>| |
| | | |
| |<****************** HTTPS *****>|
| | Transaction |
| | | |
{M,N} | |--------------------INVITE----->|
{C,M} | |<-------------------200 OK------|
{M,C} | |---------------------ACK------->|
| |<====================RTP=======>|
Figure 5 - Single Focus Webex Conference
General operation of this example:
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, URI and/or IP address, etc.)
for each device she wants for this conference call. For
example, the audio and video play-out devices could be separate
units.
o Conference Focus server sends INVITE (Session-ID header-value
"local-uuid" = M and a remote UUID of N, where M equals the
"local-uuid" for each participant on this conference bridge) to
UA-Alice to start session with that server for this A/V
conference call.
o Upon receiving the INVITE request from the conference focus
server, Alice responds with a 200 OK. Her UA moves the "local-
uuid" unchanged into the "remote-uuid" field, and generates her
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own UUID and places that into the "local-uuid" field to complete
the Session-ID construction.
o Bob and Carol perform same function to join this same A/V
conference call as Alice.
9.6. Cascading Conference Bridge Support for the Session ID
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 [RFC4579] defines the 'isfocus'
Contact: header parameter just for this purpose.
Session ID
--- MCU-1 MCU-2 MCU-3 MCU-4
| | | |
{M',N} |----INVITE----->| | |
{J,M'} |<---200 OK------| | |
{M',J} |-----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',N} UUID pair 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',N} |----INVITE----->| | |
{J,M'} |<---200 OK------| | |
{M',J} |-----ACK------->| | |
| | | |
{M',N} |---------------------INVITE----->| |
{K,M'} |<--------------------200 OK------| |
{M',K} |----------------------ACK------->| |
| | | |
{M',N} |-------------------------------------INVITE----->|
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{L,M'} |<------------------------------------200 OK------|
{M',L} |--------------------------------------ACK------->|
Figure 7 - MCU Communicating Session ID UUID to More than One
General operation of this example:
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 An MCU that receives this {M',N} UUID pair 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.
9.6.1. Calling into Cascaded Conference Bridge for the Session ID
Here is an example of how a UA, say Robert, calls into a cascaded
conference focus. Because MCU-1 has already contacted MCU-3, the MCU
where Robert is going to join the conference, MCU-3 already has the
Session-ID (M') for this particular conference call.
Session ID
--- MCU-1 MCU-2 MCU-3 Robert
| | | |
{M',N} |----INVITE----->| | |
{J,M'} |<---200 OK------| | |
{M',J} |-----ACK------->| | |
| | | |
{M',N} |---------------------INVITE----->| |
{K,M'} |<--------------------200 OK------| |
{M',K} |----------------------ACK------->| |
| | | |
{R,N} | | |<---INVITE-----|
(M',R} | | |----200 OK---->|
{R,M'} | | |<----ACK-------|
Figure 8 - A UA Calling into a Cascaded MCU UUID
General operation of this example:
o The UA, Robert in this case, INVITEs the MCU to join a
particular conference call. Robert's UA does not know anything
about whether this is the main MCU of the conference call, or a
cascaded MCU. Robert likely does not know MCUs can be cascaded,
he just wants to join a particular call. Like as with any
standard implementation, he includes a null "remote-uuid".
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o The cascaded MCU, upon receiving this INVITE from Robert,
replaces the null UUID with the UUID value communicated from
MCU-1 for this conference call as the "local-uuid" in the SIP
response. Thus, moving Robert's UUID "R" to the "remote-uuid"
value.
o The ACK has the Session-ID {R,M'}, completing the 3-way
handshake for this call establishment. Robert has now joined the
conference call originated from MCU-1.
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,N} |<----INVITE-----| |
{A,X} |-----200 OK---->| |
{A,N} | |----INVITE----->|
{B,A} | |<---200 OK------|
{A,B} |<-----ACK-------| |
{A,B} | |------ACK------>|
|<==============RTP==============>|
Figure 8 - 3PCC initiated call between Alice and Bob
General operation of this example:
o Some out of band procedure directs a B2BUA (or other SIP server)
to have Alice and Bob talk to each other. In this case, the SIP
server MUST be transaction stateful, if not dialog stateful.
o The SIP server INVITEs Alice to a session and uses a temporary
UUID {X} and a null UUID pairing.
o Alice receives and accepts this call set-up and replaces the
null UUID with her UUID {A} in the Session ID, now {A,X}.
o The transaction stateful SIP server receives Alice's UUID {A} in
the local UUID portion and keeps it there, and discards its own
UUID {X}, replacing this with a null UUID value in the INVITE to
Bob 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.
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9.8. Session ID Handling in 100 Trying SIP Response and CANCEL Request
The following two subsections show examples of the Session ID for a
100 Trying response and a CANCEL request in a single call-flow.
9.8.1. Session ID Handling in a 100 Trying SIP Response
The following 100 Trying response is taken from an existing RFC, from
[RFC5359] Section 2.9 ("Call Forwarding - No Answer").
Session ID Alice SIP Server Bob-1 Bob-2
| | | |
{A,N} |----INVITE----->| | |
{A,N} | |---INVITE---->| |
{N,A} |<--100 Trying---| | |
{B1,A} | |<-180 Ringing-| |
{B1,A} |<--180 Ringing--| | |
| | | |
| *Request Timeout* |
| | | |
{A,B1} | |---CANCEL---->| |
{B1,A} | |<--200 OK-----| |
{B1,A} | |<---487-------| |
{A,B1} | |---- ACK ---->| |
| | | |
{N,A} |<-181 Call Fwd--| | |
| | | |
{A,N} | |------------------INVITE------>|
{B2,A} | |<----------------180 Ringing---|
{B2,A} |<-180 Ringing---| | |
{B2,A} | |<-----------------200 OK ------|
{B2,A} |<--200 OK-------| | |
{A,B2} |----ACK-------->| | |
{A,B2} | |------------------ACK--------->|
| | | |
|<=========== Both way RTP Established =========>|
| | | |
{A,B2} |----BYE-------->| | |
{A,B2} | |--------------------BYE------->|
{B2,A} | |<------------------200 OK------|
{B2,A} |<--200 OK-------| | |
| | | |
Figure 9 - Session ID in the 100 Trying and CANCEL Messaging
Below is the explanatory text from RFC 5359 Section 2.9 detailing
what the desired behavior is in the above call flow (i.e., what the
call-flow is attempting to achieve).
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"Bob wants calls to B1 forwarded to B2 if B1 is not answered
(information is known to the SIP server). Alice calls B1 and no
one answers. The SIP server then places the call to B2."
General operation of this example:
o Alice generates an INVITE request because she wants to invite
Bob to join her session. She creates a UUID as described in
section 9.1, and places that value in the "local-uuid" field of
the Session-ID header-value. Alice also generates a "remote-
uuid" of null and sends this along with the "local-uuid".
o The SIP server (imagine this is a B2BUA), upon receiving Alice's
INVITE, and generates the optional provisional response 100
Trying. Since the SIP server has no knowledge Bob's UUID for
his part of the Session ID value, it cannot include his "local-
uuid". Rather, any 100 Trying response includes Alice's UUID in
the "remote-uuid" portion of the Session-ID header-value with a
null "local-uuid" value in the response. This is consistent with
what Alice's UA expects to receive in any SIP response
containing this UUID.
9.8.2. Session ID in a CANCEL SIP Request
In the same call-flow example as the 100 Trying response is a CANCEL
request. Please refer to Figure 9 for the CANCEL request example.
General operation of this example:
o In Figure 9 above, Alice generates an INVITE with her UUID value
in the Session-ID header-value.
o Bob-1 responds to this INVITE with a 180 Ringing. In that
response, he includes his UUID in the Session-ID header-value
(i.e., {B1,A}); thus completing the Session-ID header-value for
this session, even though no final response has been generated
by any of Bob's UAs.
o This means that if the SIP server were to generate a SIP request
within this session, in this case a CANCEL request, it would
have a complete Session ID to include in that request. In this
case, the "local-uuid" = "A", and the "remote-uuid" = "B1".
o As it happens with this CANCEL, the SIP server intends to invite
another UA of Bob (i.e., B2) for Alice to communicate with.
o In this example call-flow, taken from RFC 5359, Section 2.9, a
181 (Call is being Forwarded) response is sent to Alice. Since
the SIP server generated this SIP request, and has no knowledge
of Bob-2's UUID value, it cannot include that value in this 181.
Thus, and for the exact reasons the 100 Trying including the
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Session ID value, only Alice's UUID is included in the remote-
uuid field of the Session-ID header-value, with a null UUID
present in the "local-uuid" field.
9.9. Session ID in an out-of-dialog REFER Transaction
The following call-flow was extracted from Section 6.1 of [RFC5589]
("Successful Transfer"), with the only changes being the names of the
UAs to maintain consistency within this document.
Alice is the transferee
Bob is the transferer
and Carol is the transfer-target
Session ID Bob Alice Carol
| | |
{A,N} |<-----INVITE--------| |
{B,A} |------200 OK------->| |
{A,B} |<------ACK----------| |
| | |
{B,A} |--INVITE {hold}---->| |
{A,B} |<-200 OK------------| |
{B,A} |--- ACK ----------->| |
| | |
{X,N} |--REFER------------>|(Target-Dialog:Carol)|
{Y,X} |<-202 Accepted------| |
| | |
{Y,X} |<NOTIFY {100 Trying}| |
{X,Y} |-200 OK------------>| |
| | |
{A,N} | |--INVITE------------>|
{C,A} | |<-200 OK-------------|
{A,C} | |---ACK-------------->|
| | |
{A,B} |<--NOTIFY {200 OK}--| |
{B,A} |---200 OK---------->| |
| | |
{B,A} |--BYE-------------->| |
{A,B} |<-200 OK------------| |
{C,A} | |<------------BYE-----|
{A,C} | |-------------200 OK->|
Figure 10: Basic Transfer Call Flow
General operation of this example:
o Just as in Section 9.2, Figure 2, Alice invites Bob to a
session, and Bob eventually transfers Alice to communicate with
Carol.
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o What is different about the call-flow in Figure 10 is that Bob's
REFER is not in-dialog, meaning it would have the same UUID
pair. Rather, in this case, Bob's using an out-of-dialog REFER,
meaning Bob generates a new UUID for this SIP request, and
Alice, subsequently would also generate a new UUID for the 202
(Accepted) response, replacing the null "remote-uuid in the
REFER.
o Alice will use her existing UUID {A,N} in the INVITE towards
Carol (who generates UUID "C" for this session), thus
maintaining the common UUID within the Session ID for this new
Alice-to-Carol session.
10. Compatibility with a Previous Implementation
There is a much earlier and proprietary document that specifies the
use of a Session-ID header [draft-kaplan-insipid-session-id] that we
will herewith attempt to achieve backwards compatibility. Neither
Session-ID header 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.
But that is where compatibility is not ensured, given the unknowns
related to the behavior of entities implementing the pre-standard
implementation. For this "new" implementation to work with the "old"
implementation *and* any "old" implementation to work with "new"
implementations, there needs to be a set of rules for all "new"
implementations MUST follow.
- since no option tags or feature tags are to be used for
distinguishing versions, the presence and order of any "remote-
uuid" value within the Session-ID header value is to be used to
distinguish implementation versions.
- if a SIP request has a "remote-uuid" value, this comes from a
standard implementation, and not a pre-standard one.
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- if a SIP request has no "remote-uuid" value, this comes from a pre-
standard implementation, and not a standard one. In this case, one
UUID is used to identify this dialog, even if the responder is a
standard implementation of this specification.
- if a SIP response has a non-null "local-uuid" that is 32 octets
long, this response comes from a standard implementation. There are
two exceptions to this rule: a 100 Trying response and a 181 Call
Forwarded response will have null "local-uuid" values.
- if a SIP response has a non-null "local-uuid" that is not 32 octets
long, this response comes from a misbehaving implementation, and
its Session-ID header value MUST be discarded. That said, the
response might still be valid according to the rules within SIP
[RFC3261], and SHOULD be checked further.
- if a SIP response arrives that has the same value of Session-ID
UUIDs in the same order as was sent, this comes from a pre-standard
implementation, and MUST NOT be discarded for not altering the null
"remote-uuid". In this case, any new transaction within this dialog
MUST preserve the order of the two UUIDs within all Session-ID
header-values, including the ACK, until this dialog is terminated.
- if a SIP response only contains the "local-uuid" that was sent
originally, this comes from a pre-standard implementation and MUST
NOT be discarded for removing the null "remote-uuid". In this case,
all future transactions within this dialog MUST contain only the
UUID received in the first SIP response. Any new transaction
starting a new dialog from the standard Session-ID implementation
MUST include and "local-uuid" and a null "remote-uuid", even if
that new dialog is between the same two UAs.
- Standard implementations SHOULD NOT expect pre-standard
implementations to be consistent in their implementation, even
within the same dialog. For example, perhaps the first, third and
tenth responses contain a "remote-uuid", but all the others do not.
This behavior SHOULD (MUST?) be allowed by standard implementations
of the Session-ID specification.
- All of this does not apply to other parameters that might be
defined in the future, i.e., currently unknown. They are discarded.
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.
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The Session Identifier might be utilized for logging or
troubleshooting, but MUST NOT be used for billing purposes.
Other considerations???
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 Robert Sparks, Hadriel Kaplan,
Christer Holmberg, Paul Kyzivat, and Charles Eckel for their
invaluable comments during the development of this document.
14. References
14.1. Normative References
[RFC3261] Rosenberg, J., et al., "SIP: Session Initiation
Protocol", RFC 3261, June 2002.
[H.323] Recommendation ITU-T H.323, "Packet-based multimedia
communications systems", December 2009.
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4122] Leach, P., Mealling, M., Salz, R., "A Universally Unique
IDentifier (UUID) URN Namespace", RFC 4122, July 2005.
[RFC5234] Crocker, D., Overell, P, "Augmented BNF for Syntax
Specifications: ABNF", RFC 5234, January 2008.
[RFC4579] Johnston, A., Levin, O., "Session Initiation Protocol
(SIP) Call Control - Conferencing for User Agents", RFC
4579, August 2006.
[RFC3891] Mahy, R., Biggs, B., Dean, R., 'The Session Initiation
Protocol (SIP) "Replaces" Header', RFC 3891, September
2004.
[RFC3515] Sparks, R., "The Session Initiation Protocol (SIP) Refer
Method", RFC 3515, April 2003.
[I-D.kaplan-insipid-session-id]
Kaplan, H., "A Session Identifier for the Session
Initiation Protocol (SIP)", August 2013.
14.2. Informative References
[RFC3550] Schulzrinne, H., et al., "RTP: A Transport Protocol for
Real-Time Applications", RFC 3550, July 2003.
[I-D.ietf-insipid-session-id-reqts]
Jones, et al., "Requirements for an End-to-End Session
Identification in IP-Based Multimedia Communication
Networks", draft-ietf-insipid-session-id-reqts-09,
November 2013.
[RFC5359] Johnston, A., et al., "Session Initiation Protocol
Service Examples", RFC 5359, October 2008.
[RFC5589] Sparks, R., Johnston, A., Petrie, D., "Session Initiation
Protocol (SIP) Call Control - Transfer", RFC 5359, June
2009.
Jones, et al. Expires July 24, 2014 [Page 26]
Internet-Draft End-To-End Session ID January 2014
Author's Addresses
Paul E. Jones (Ed.)
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 (Ed.)
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 July 24, 2014 [Page 27]