| Network Working Group | C. Holmberg |
| Internet-Draft | J. Holm |
| Intended status: Standards Track | Ericsson |
| Expires: July 13, 2015 | R. Jesske |
| Deutsche Telekom | |
| M. Dolly | |
| ATT | |
| January 9, 2015 |
3rd-Generation Partnership Project (3GPP) SIP URI Inter Operator Traffic Leg parameter
draft-holmberg-dispatch-iotl-04.txt
In 3rd-Generation Partnership Project (3GPP) networks, the signalling path between a calling user and a called user can be partioned into segments, referred to as traffic legs. Each traffic leg may span networks belonging to different operators, and will have its own characteristics that can be different from other traffic legs in the same call. A traffic leg might be associated with multiple SIP dialogs, e.g. in case a B2BUA which modifies the SIP dialog identifier is located within the traffic leg.
This document defines a new SIP URI parameter, 'iotl'. The parameter can be used in a SIP URI to indicate that the entity associated with the address, or an entity responsible for the host part of the address, represents the end of a specific traffic leg (or multiple traffic legs).
The SIP URI 'iotl' parameter defined in this document has known uses in 3GPP networks. Usage in other networks is also possible.
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In a 3rd-Generation Partnership Project (3GPP) network, an end user device can be attached (e.g. using a radio access network) to its own operator network (home network) [TS.3GPP.24.229], or to another operator's network (visited network) [TS.3GPP.24.229]. In the latter case the user is referred to as a roaming user.
3GPP operator networks are often not connected directly to each other. Instead, there might be intermediate networks, referred to as 3GPP transit networks, between them. Such transit network act on SIP level or on IP level.
In 3GPP networks, the signalling path between a calling user and a called user can be partioned into segments, referred to as traffic legs. Each traffic leg may span networks belonging to different operators, and will have its own characteristics that can be different from other traffic legs in the same call. A traffic leg might be associated with multiple SIP dialogs, e.g. in case a Back-To-Back User Agent (B2BUA) [RFC3261] which modifies the SIP dialog identifier is located within the traffic leg.
The traffic leg information can be used by intermediary entities to make policy decisions, related to e.g. media anchoring, signalling policy, insertion of media functions (e.g. transcoder) and charging.
The figure below shows two users (Alice and Bob) and the different type of networks that the signaling might traverse. The signalling path can be divided into multiple traffic legs, and the type of traffic legs depends on how the signalling is routed.
Alice -- ORIG HNW +++++ TRANSIT NW +++++ TERM HNW -- Bob
Home + + + + + Home
+ ++++++++++++++++++ + +
+ + +
+ + +
+ +++++++++++++++++++++++ +
+ + + +
Alice -- ORIG VNW +++++ TRANSIT NW ++ TERM VNW -- Bob
Visited Visited
Figure 1: 3GPP operator network roaming roles
ORIG HNW = Originating 3GPP Home Network
TERM HNW = Terminating 3GPP Home Network
ORIG VNW = Originating 3GPP Visited Network
TERM VNW = Terminating 3GPP Visited Network
TRANSIT NW = 3GPP Transit Network
In Figure 1 Alice is a user initiating communication with Bob, and:
Alice is attached to an originating network, which is either the home network of Alice, or a visited network (in case Alice is roaming). In both cases any originating service is provided by the home network of Alice.
Bob is attached to a terminating network, which is either the home network of Bob, or a visited network (in case Bob is roaming). In both cases any terminating service is provided by the home network of Bob.
A transit network, providing transit functions (e.g. translation of free phone numbers), may be included between the originating and terminating networks and between visited and home networks.
This document defines a new SIP URI parameter [RFC3261], 'iotl'. The parameter can be used in a SIP URI to indicate that the entity associated with the address, or an entity responsible for the host part of the address, represents the end of a specific traffic leg (or multiple traffic legs).
SIP entities that do not support the SIP URI 'iotl' parameter will simply ignore it, if received, as defined in [RFC3261].
The SIP URI 'iotl' parameter defined in this document has known uses in 3GPP networks. Usage in other networks is also possible.
The SIP URI 'iotl' parameter defined in this document has known uses in 3GPP networks. Usage in other networks is also possible.
This section describes examples of different types of traffic legs in 3GPP networks.
In this case, Alice is located in a visited network. When Alice sends the initial SIP INVITE request for a call, one traffic leg (referred to as the 'visitedA-homeA' traffic leg) represents the signalling path between the UA of Alice and the home S-CSCF [3GPP TS 24.229] of Alice.
In this case, Bob is located in a visited network. When the home S-CSCF of Bob forwards the initial SIP INVITE request for a call towards Bob, one traffic leg (referred to as the 'homeB-visitedB' traffic leg) represents the signalling path between the home S-CSCF of Bob and the UA of Bob.
In this case, the home S-CSCF of Alice forwards the initial SIP INVITE request towards the home S-CSCF of Bob. The signalling path between the S-CSCFs represents one traffic leg (referred to as the 'homeA-homeB' traffic leg).
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].
As specified in [RFC3261], when a SIP entity inserts a SIP URI in an initial request for a dialog, or in a stand-alone request, the SIP URI will be used to route the request to another SIP entity, addressed by the SIP URI, or to a SIP entity responsible for the host part of the SIP URI (e.g. a SIP registrar). If such entity represents the end of one or more traffic legs, the SIP entity inserting the SIP URI can add a SIP URI 'iotl' parameter to the SIP URI, to indicate the type(s) of traffic leg. Each parameter value indicates a type of traffic leg.
For routing of a SIP request, a SIP entity can add the 'iotl' parameter to the SIP URI of the Request-URI [RFC3261], or to the SIP URI of a Route header field [RFC3261], of an initial request for a dialog, or of an stand-alone request. SIP entities can add the 'iotl' parameter to the SIP URI of a Path header field [RFC3327] or a Service-Route header field [RFC3608], in order for the parameter to later occur in a Route header field.
When a SIP entity receives an initial request for a dialog, or a stand-alone request, which contains one or more SIP URI 'iotl' parameters, it identifies the type of traffic leg in the following way:
During SIP registration [RFC3261], entities can add the 'iotl' parameter to the SIP URI of a Path or Service-Route header field, if the entity is aware that SIP URI will be used to indicate the end of a specific traffic leg for initial requests for dialogs, or stand-alone requests, sent on the registration path.
As defined in [RFC3261], a SIP entity must not modify remove uri parameters from SIP URIs associated with other entities. This also applies to the 'iotl' parameter.
This section describes the SIP URI 'iotl' parameter values defined in this specification.
This value indicates that a SIP entity responsible for the host part of the SIP URI associated with the parameter represents the end of a traffic leg between the home network (originating) of the calling user and the home network (terminating) of the called user.
In 3GPP, this traffic leg is between two S-CSCFs.
This value indicates that the SIP entity addressed by the SIP URI associated with the parameter represents the end of a traffic leg between the home network (terminating) of the called user and the visited network (terminating) in which the called user is located.
In 3GPP, this traffic leg is between the home S-CSCF and the UE of the called user, or between the Service Centralization and Continuity Application Server (SCC AS) in the home network of the called user and Access Transfer Control Function (ATCF) in the visited network of the called user.
This value indicates that a SIP entity responsible for the host part of the SIP URI associated with the parameter represents the end of a traffic leg between the visited network (originating) in which the calling user is located and the home network (originating) of the calling user.
In 3GPP, this traffic leg is between the UE and the home S-CSCF of the calling user, or between the P-CSCF in the visited network, serving the calling user, and the home S-CSCF of the calling user.
This value indicates that the SIP entity addressed by the SIP URI associated with the parameter represents the end of a traffic leg between the home network (originating) and the visited network (originating) in which the calling user is located.
In 3GPP, this traffic leg is between the home S-CSCF of the calling user and the Transit and Roaming Function (TRF) [3GPP TS 24.229] serving the calling user, and exists in scenarios where the home S-CSCF of the calling user forwards a request back to the visited network where the UE of the calling user is located. An example of this is when the Roaming Architecture for Voice over IMS with Local breakout (RAVEL) [3GPP TS 24.229] feature is enabled.
This value indicates that a SIP entity responsible for the host part of the SIP URI associated with the parameter represents the end of a traffic leg between the visited network (originating) of the calling user and the home network (terminating) of the called user.
In 3GPP, this traffic leg is between the Transit and Roaming Function (TRF) [3GPP TS 24.229] serving the calling user and the home S-CSCF of the called user, and exists in scenarios where a request is forwarded from the visited network where the calling user is located directly to the home S-CSCF of the called user. An example of this is when the Roaming Architecture for Voice over IMS with Local breakout (RAVEL) [3GPP TS 24.229] feature is enabled.
This section defines the ABNF for the 'iotl' SIP URI parameter. The ABNF defined in this specification is conformant to RFC 5234 [RFC5234].
This specification does not create an IANA registry for 'iotl' parameter values. A registry should be considered if new parameter values are defined in the future.
The ABNF [RFC5234] grammar for the role SIP URI parameter is:
uri-parameter =/ iotl-param iotl-param = iotl-tag "=" iotl-value ["." iotl-value] iotl-tag = "iotl" iotl-value = "homeA-homeB" / "homeB-visitedB" / "visitedA-homeA" / "homeA-visitedA" /" visitedA-homeB" / other-iotl other-iotl = 1*iotl-char iotl-char = alphanum / "-" ;; alphanum defined in RFC 3261
The information SHOULD only be used for making policy decisions based on the role by nodes within the same trust domain [RFC3325]. In addition, there MUST exist an agreement between the operators for usage of the roaming role information.
[RFC EDITOR NOTE: Please replace RFC-XXXX with the RFC number of this document.] This specification adds one new value to the IANA registration in the "SIP/SIPS URI Parameters" registry as defined in [RFC3969].
Parameter Name Predefined Values Reference
____________________________________________
iotl Yes [This RFC]
The authors wish to thank everyone in the 3GPP community that gave comments on the initial version of this document, and contributed with comments and suggestion during the work. A special thanks to Paul Kyziwat, Dale Worley and Michael Hammer. Robert Sparks performed the Gen-ARTreview of the draft.
[RFC EDITOR NOTE: Please remove this section when publishing]
draft-holmberg-dispatch-iotl-03
draft-holmberg-dispatch-iotl-02
draft-holmberg-dispatch-iotl-01
draft-holmberg-dispatch-iotl-00
| [RFC3325] | Jennings, C., Peterson, J. and M. Watson, "Private Extensions to the Session Initiation Protocol (SIP) for Asserted Identity within Trusted Networks", RFC 3325, November 2002. |
This section contains example call flows based on 3GPP usage of the SIP URI 'iotl' parameter.
The Visited Proxy (P-CSCF) adds the iotl value 'homeB-visitedB' to the Path header field of the REGISTER request, to be used for terminating routing towards Alice. The Home Proxy (S-CSCF) adds the iotl value 'visitedA-homeA' to the Service-Route header field, to be used for originating initial/stand-alone requests from Alice.
Visited Proxy Visited Proxy Home Proxy Home Proxy
Alice's . . . . P-CSCF . . . . . IBCF-V . . . . . IBCF-H . . . . S-CSCF
| | | | |
| REGISTER F1 | | | |
|--------------->| REGISTER F2 | | |
| |--------------->| REGISTER F3 | |
| | |--------------->| REGISTER F4 |
| | | |--------------->|
| | | | |
| | | | 200 (OK) F5 |
| | | |<---------------|
| | | 200 (OK) F6 | |
| | |<---------------| |
| | 200 (OK) F7 | | |
| |<---------------| | |
| 200 (OK) F8 | | | |
|<---------------| | | |
F1 REGISTER Alice -> P-CSCF
REGISTER sip:registrar.home1.net SIP/2.0
F2 REGISTER P-CSCF -> IBCF-V
REGISTER sip:registrar.home1.net SIP/2.0
Path: <p-cscf URI;iotl=homeB-visitedB>
F3 REGISTER IBCF-V -> IBCF-H
REGISTER sip:registrar.home1.net SIP/2.0
Path: <p-cscf URI;iotl=homeB-visitedB>
F4 REGISTER IBCF-H -> S-CSCF
REGISTER sip:registrar.home1.net SIP/2.0
Path: <p-cscf URI;iotl=homeB-visitedB>
F5 200 OK S-CSCF -> IBCF-H
200 OK
Path: <p-cscf URI;iotl=homeB-visitedB>
Service-Route: <s-cscf URI;iotl=visitedA-homeA>
F6 200 OK IBCF-H -> IBCF-V
200 OK
Path: <p-cscf URI;iotl=homeB-visitedB>
Service-Route: <s-cscf URI;iotl=visitedA-homeA>
F7 200 OK IBCF-V -> P-CSCF
200 OK
Path: <p-cscf URI;iotl=homeB-visitedB>
Service-Route: <s-cscf URI;iotl=visitedA-homeA>
F8 200 OK P-CSCF -> Alice
200 OK
Path: <p-cscf URI;iotl=homeB-visitedB>
Service-Route: <s-cscf URI;iotl=visitedA-homeA>
Figure 2: The UE registers via P-CSCF
In the originating INVITE request from Alice, the iotl value 'visitedA-homeA', received in the Service-Route header field during registration, is added to the Route header field representing the Home Proxy S-CSCF, to indicate the traffic leg type between the Visited Proxy P-CSCF and the Home Proxy S-CSCF.
Visited Proxy Visited Proxy Home Proxy Home Proxy
Alice's . . . . P-CSCF . . . . . IBCF-V . . . . . IBCF-H . . . . S-CSCF
| | | | |
| INVITE F1 | | | |
|--------------->| INVITE F2 | | |
| |--------------->| INVITE F3 | |
| | |--------------->| INVITE F4 |
| | | |--------------->|
| | | | |
| | | | 180 F5 |
| | | 180 F6 |<---------------|
| | 180 F7 |<---------------| |
| 180 F8 |<---------------| | |
|<---------------| | | |
| | | | |
F1 INVITE Alice -> P-CSCF
INVITE sip:Bob@homeB.net SIP/2.0
Route: <p-cscf URI>,<s-cscf URI;iotl=visitedA-homeA>
F2 INVITE P-CSCF -> IBCF-V
INVITE sip:Bob@homeB.net SIP/2.0
Route: <ibcf-v URI>,<s-cscf URI;iotl=visitedA-homeA>
F3 INVITE IBCF-V -> IBCF-H
INVITE sip:Bob@homeB.net SIP/2.0
Route: <ibcf-h URI>,<s-cscf URI;iotl=visitedA-homeA>
F4 INVITE IBCF-H -> S-CSCF
INVITE sip:Bob@homeB.net SIP/2.0
Route: <s-cscf URI;iotl=visitedA-homeA>
Figure 3: Originating IMS call
In the terminating INVITE request towards Alice, the iotl value 'homeB-visitedB', provided to the Home Proxy S-CSCF during registration, is added to the Route header field representing the Visited Proxy P-CSCF, to indicate the traffic leg type between the Home Proxy S-CSCF and the Visited Proxy P-CSCF.
Home Proxy Home Proxy Visited Proxy Visited Proxy
S-CSCF . . . . IBCF-H . . . . . IBCF-V . . . . . P-CSCF . . . . . Bob
| | | | |
| INVITE F1 | | | |
|--------------->| INVITE F2 | | |
| |--------------->| INVITE F3 | |
| | |--------------->| INVITE F4 |
| | | |--------------->|
| | | | |
| | | | 180 F5 |
| | | 180 F6 |<---------------|
| | 180 F7 |<---------------| |
| 180 F8 |<---------------| | |
|<---------------| | | |
| | | | |
F1 INVITE S-CSCF -> IBCF-H
INVITE sip:Bob@visitedB.net SIP/2.0
Route: <ibcf-h URI>,<p-cscf-v URI;iotl=homeB-visitedB
F2 INVITE IBCF-H -> IBCF-V
INVITE sip:Bob@visitedB.net SIP/2.0
Route: <ibcf-v URI>,<p-cscf-v URI;iotl=homeB-visitedB
F3 INVITE IBCF-V -> P-CSCF
INVITE sip:Bob@visitedB.net SIP/2.0
Route: <p-cscf-v URI;iotl=homeB-visitedB
F4 INVITE P-CSCF -> Bob
INVITE sip:Bob@visitedB.net SIP/2.0
Figure 4: Terminating IMS call
The S-CSCF of the originating home network adds the iotl value 'homeA-homeB' in the Request-URI of the INVITE, sent towards the S-CSCF of the terminating network, to indicate the traffic leg type between the S-CSCFs.
Home-A Proxy Home-A Proxy Home-B Proxy Home-B Proxy Home-B Proxy
S-CSCF-A . . . . IBCF-A . . . . .IBCF-B . . . . .I-CSCF-B . . .S-CSCF-B
| | | | |
| INVITE F1 | | | |
|--------------->| INVITE F2 | | |
| |--------------->| INVITE F3 | |
| | |--------------->| INVITE F4 |
| | | |--------------->|
| | | | |
| | | | 180 F5 |
| | | 180 F6 |<---------------|
| | 180 F7 |<---------------| |
| 180 F8 |<---------------| | |
|<---------------| | | |
| | | | |
F1 INVITE S-CSCF-A -> IBCF-A
INVITE sip:Bob@visitedB.net;iotl=homeA-homeB SIP/2.0
F2 INVITE IBCF-a -> IBCF-B
INVITE sip:Bob@visitedB.net;iotl=homeA-homeB SIP/2.0
F3 INVITE IBCF-B -> I-CSCF-B
INVITE sip:Bob@visitedB.net;iotl=homeA-homeB SIP/2.0
F4 INVITE I-CSCF-B -> S-CSCF-B
INVITE sip:Bob@visitedB.net;iotl=homeA-homeB SIP/2.0
Figure 5: Call between originating home and terminating home network