ETSI TS 183 048 V2.2.1 (2009-08)

Technical Specification
Telecommunications and Internet converged Services and
Protocols for Advanced Networking (TISPAN);
Resource and Admission Control System (RACS);
Protocol Signalling flows specification;
RACS Stage 3
2 ETSI TS 183 048 V2.2.1 (2009-08)

Reference
RTS/TISPAN-03200-NGN-R2
Keywords
protocol, signalling, stage 3
ETSI
650 Route des Lucioles
F-06921 Sophia Antipolis Cedex - FRANCE

Tel.: +33 4 92 94 42 00  Fax: +33 4 93 65 47 16

Siret N° 348 623 562 00017 - NAF 742 C
Association à but non lucratif enregistrée à la
Sous-Préfecture de Grasse (06) N° 7803/88

Important notice
Individual copies of the present document can be downloaded from:
http://www.etsi.org
The present document may be made available in more than one electronic version or in print. In any case of existing or
perceived difference in contents between such versions, the reference version is the Portable Document Format (PDF).
In case of dispute, the reference shall be the printing on ETSI printers of the PDF version kept on a specific network drive
within ETSI Secretariat.
Users of the present document should be aware that the document may be subject to revision or change of status.
Information on the current status of this and other ETSI documents is available at
http://portal.etsi.org/tb/status/status.asp
If you find errors in the present document, please send your comment to one of the following services:
http://portal.etsi.org/chaircor/ETSI_support.asp
Copyright Notification
No part may be reproduced except as authorized by written permission.
The copyright and the foregoing restriction extend to reproduction in all media.

© European Telecommunications Standards Institute 2009.
All rights reserved.
TM TM TM TM
DECT , PLUGTESTS , UMTS , TIPHON , the TIPHON logo and the ETSI logo are Trade Marks of ETSI registered
for the benefit of its Members.
TM
3GPP is a Trade Mark of ETSI registered for the benefit of its Members and of the 3GPP Organizational Partners.
LTE™ is a Trade Mark of ETSI currently being registered
for the benefit of its Members and of the 3GPP Organizational Partners.
GSM® and the GSM logo are Trade Marks registered and owned by the GSM Association.
ETSI
3 ETSI TS 183 048 V2.2.1 (2009-08)
Contents
Intellectual Property Rights . 4
Foreword . 4
1 Scope . 5
2 References . 5
2.1 Normative references . 6
2.2 Informative references . 7
3 Abbreviations . 7
4 Example call flow . 8
5 RACS related procedures . 9
5.1 Procedures at P-CSCF/IBCF . 9
5.1.1 Resource and admission control . 9
5.1.2 NAPT/NAPT-PT at the P-CSCF/IBCF. 10
5.2 Procedures at SPDF . 10
5.2.1 Reservation with BGF involved. 10
5.2.1.1 Resource reservation at the BGF . 10
5.2.1.2 Initial reservation for an session (SDP offer) . 12
5.2.1.3 Connection information received from the opposite direction (SDP answer) . 14
5.2.1.4 Connection information (SDP answer) received corresponding to multiple early dialogues . 15
5.2.1.5 BGF Media Transcoding . 15
5.2.1.6 BGF transport plane failure detection . 16
5.2.2 Reservation with x-RACF involved . 16
5.2.3 Reservation involving both x-RACF and BGF . 17
5.3 Procedures at x-RACF . 18
5.3.1 Determining RCEF involvement . 18
5.3.2 Reporting RCEF failure . 18
5.3.3 Multicast authorization . 18
5.4 Diameter request routing considerations . 18
6 Example signalling flows (informative) . 19
6.1 Basic IMS end-to-end signalling flow . 19
6.1.1 Session setup . 21
6.1.2 Session termination . 45
6.1.3 Session failures . 51
6.1.3.1 RCEF failure at session setup. 51
6.1.3.2 RCEF failure after session setup . 54
6.1.3.3 C-BGF A transport plane failure . 59
6.1.3.4 Admission denial . 67
6.1.4 Session Update . 69
6.2 IMS signalling flow involving IBCF entities . 92
6.2.1 Session setup . 93
6.2.2 Session termination . 110
6.3 IMS-based IPTV . 112
6.4 Traffic policy activation request -PULL mode . 173
6.4.1 Policy activation . 174
6.4.2 Policy deactivation . 175
6.5 Communication Waiting . 176
6.6 Media Latching/Hosted NAT traversal . 194
Annex A (informative): Bibliography . 205
Annex B (informative): Change history . 206
History . 208

ETSI
4 ETSI TS 183 048 V2.2.1 (2009-08)
Intellectual Property Rights
IPRs essential or potentially essential to the present document may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web
server (http://webapp.etsi.org/IPR/home.asp).
Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee
can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web
server) which are, or may be, or may become, essential to the present document.
Foreword
This Technical Specification (TS) has been produced by ETSI Technical Committee Telecommunications and Internet
converged Services and Protocols for Advanced Networking (TISPAN).
ETSI
5 ETSI TS 183 048 V2.2.1 (2009-08)
1 Scope
The present document specifies normative rules for how to use the Gq', Rq, Ia and Re protocols (TS 183 017 [4],
ES 283 026 [3] ES 283 018 [7] and TS 183 060 [9]) as of TISPAN release 2. These rules apply to the interface between:
• P-CSCF and SPDF using Gq';
• IBCF and SPDF using Gq';
• SPDF and (C- and I-) BGF using Ia;
• SPDF and x-RACF using Rq;
• x-RACF and RCEF using Re.
In addition, to illustrate the usage of these rules, the present document contains informative signalling flows between
the above-listed entities.
The present document covers both IMS and non-IMS AFs, and both conversational services such as telephony and
non-conversational services such as IPTV.
For IPTV, both unicast and multicast are covered, as well as the push and pull models for interactions with the
ECF/EFF. Conversational multicast services and the usage of pull for conversational services is out of the scope for the
present document.
In case of any discrepancy between the end-to-end IMS signalling flows in the present document and the ETSI TISPAN
IMS specifications (TS 182 006 [5], ES 283 003 [6] and TS 183 063 [10]), the ETSI TISPAN IMS specifications shall
take precedence.
The following specific topics are covered in the present document;
• policy enforcement in the RCEF;
• error handling over Ia;
• transcoding in the I/C-BGF;
• reservations requests in overbooking mode;
• address latching for hosted NAPT/NAPT-PT traversal.
2 References
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific.
• For a specific reference, subsequent revisions do not apply.
• Non-specific reference may be made only to a complete document or a part thereof and only in the following
cases:
- if it is accepted that it will be possible to use all future changes of the referenced document for the
purposes of the referring document;
- for informative references.
Referenced documents which are not found to be publicly available in the expected location might be found at
http://docbox.etsi.org/Reference.
NOTE: While any hyperlinks included in this clause were valid at the time of publication ETSI cannot guarantee
their long term validity.
ETSI
6 ETSI TS 183 048 V2.2.1 (2009-08)
2.1 Normative references
The following referenced documents are indispensable for the application of the present document. For dated
references, only the edition cited applies. For non-specific references, the latest edition of the referenced document
(including any amendments) applies.
[1] IETF RFC 3550: "RTP: A Transport Protocol for Real-Time Applications".
[2] ETSI TS 129 207: "Digital cellular telecommunications system (Phase 2+);Universal Mobile
Telecommunications System (UMTS); Policy control over Go interface (3GPP TS 29.207)".
[3] ETSI ES 283 026: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN);Resource and Admission Control; Protocol for QoS reservation
information exchange between the Service Policy Decision Function (SPDF) and the
Access-Resource and Admission Control Function (A-RACF) in the Resource and Protocol
specification".
[4] ETSI TS 183 017: "Telecommunications and Internet Converged Services and Protocols for
Advanced Networking (TISPAN); Resource and Admission Control: DIAMETER protocol for
session based policy set-up information exchange between the Application Function (AF) and the
Service Policy Decision Function (SPDF);Protocol specification".
[5] ETSI TS 182 006: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN); IP Multimedia Subsystem (IMS); Stage 2 description
(3GPP TS 23.228 v7.2.0, modified)".
[6] ETSI ES 283 003: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN); IP Multimedia Call Control Protocol based on Session
Initiation Protocol (SIP) and Session Description Protocol (SDP) Stage 3 [3GPP TS 24.229
[Release 7], modified]".
[7] ETSI ES 283 018: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN); Resource and Admission Control: H.248 Profile for controlling
Border Gateway Functions (BGF) in the Resource and Admission Control Subsystem (RACS);
Protocol specification".
[8] ETSI TS 124 229: "Digital cellular telecommunications system (Phase 2+); Universal Mobile
Telecommunications System (UMTS); Internet Protocol (IP) multimedia call control protocol
based on Session Initiation Protocol (SIP) and Session Description Protocol (SDP); Stage 3
(3GPP TS 24.229)".
[9] ETSI TS 183 060: "Telecommunications and Internet Converged Services and Protocols for
Advanced Networking (TISPAN); Resource and Admission Control Subsystem (RACS);
Re interface based on the DIAMETER protocol".
[10] ETSI TS 183 063: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN); IMS-based IPTV stage 3 specification".
[11] IETF RFC 3588: "Diameter Base Protocol".
[12] ITU-T Recommendation H.248.1: "Gateway control protocol: Version 3".
[13] IETF RFC 3246: "An Expedited Forwarding PHB (Per-Hop Behavior)".
[14] IETF RFC 4566: "SDP: Session Description Protocol".
[15] IETF RFC 2597: "Assured Forwarding PHB Group".
[16] ETSI TS 124 615: "Digital cellular telecommunications system (Phase 2+); Universal Mobile
Telecommunications System (UMTS); Communication Waiting (CW) using IP Multimedia (IM)
Core Network (CN) subsystem; Protocol Specification. (3GPP TS 24.615)".
ETSI
7 ETSI TS 183 048 V2.2.1 (2009-08)
2.2 Informative references
The following referenced documents are not essential to the use of the present document but they assist the user with
regard to a particular subject area. For non-specific references, the latest version of the referenced document (including
any amendments) applies.
Not applicable.
3 Abbreviations
For the purposes of the present document, the following abbreviations apply:
AAA AA-Answer
AAR AA-Request
AF Application Function
A-RACF Access - Resource Admission Control Function
AS Application Server
AVP Attribute Value Pair
BGF Border Gateway Function
C/I-BGF Core/Interconnection Border Gateway Function
CLF Connectivity session Location and repository Function
CW Communication Waiting
DL Down Link
FE Functional Entity
IBCF Interconnection Border Control Function
IMS IP Multimedia Subsystem
IP Internet Protocol
LD Local Descriptor
MG Media Gateway
MGC Media Gateway Controller
NAPT Network Address and Port Translation
NAPT-PT Network Address and Port Translation - Protocol Translation
NAT Network Address Translation
NDUB Network Determined User Busy
PCMU Pulse Code Modulation Mu-law
P-CSCF Proxy - Call Session Control Function
RACS Resource and Admission Control Subsystem
RCEF Resource Control Enforcement Function
RTCP Real Time Control Protocol
RTP Real Time Protocol
SDP Session Description Protocol
SIP Session Initiation Protocol
SPDF Service-based Policy Decision Function
UDP User Datagram Protocol
UE User Equipment
UL Up Link
XML eXtensible Markup Language
ETSI
8 ETSI TS 183 048 V2.2.1 (2009-08)
4 Example call flow
This clause contains a set of informative example call flows.

Figure 4.1: RACS, RCEF, BGF and P-CSCF/IBCF interactions (alternative 1)
Figure 4.1 illustrates the basic interactions involved when requesting a resource reservation from RACS for an IMS call.
It should be noted that the SPDF may interrogate I/C-BGF and x-RACF (shown as A-RACF in figure 4.1) in any order.
Hence, interacting with the C-BGF after the x-RACF as shown in figure 4.1 is not mandated, and the SPDF may instead
interrogate the x-RACF before the I/C-BGF as shown in figure 4.2, or interrogate these entities in parallel.
ETSI
9 ETSI TS 183 048 V2.2.1 (2009-08)
A-RACF A-RACF C- BGF/I-BGF SPDF P-CSCF/IBCF
SDP offer/
answer received
Define
connection info.
Diameter AAR
SPDF policy
Diameter AAR
Resource and
policy based
admission control
Diameter PIR
Policy install
Diameter PIA
Diameter AAA
H.248 ADD
Create
terminations
H.248 ADD reply
Extract
termination
addresses
Diameter AAA
Modify SDP
offer/answer
Figure 4.2: RACS, RCEF, BGF and P-CSCF/IBCF interactions (alternative 2)
For some deployments, the extraction of termination addresses done by the SPDF for signalling to the x-RACF may
rely on information coming from I/C-BGF. For example, the x-RACF may need the local termination address at the
C-BGF when performing resource and admission control for the network in between the RCEF and the C-BGF. Unless
this address information can be derived by other means, the SPDF needs to interrogate the C-BGF to obtain the local
termination address at the C-BGF before issuing a Diameter AAR to the x-RACF.
The interactions illustrated in figure 4.1 (and figure 4.2) are repeated twice for each call setup and each SPDF instance
along the path of the attempted call as described in the following clauses.
5 RACS related procedures
This clause specifies normative rules for how to use the Gq', Rq, Ia and Re protocols.
5.1 Procedures at P-CSCF/IBCF
5.1.1 Resource and admission control
This clause describes the rules used by the P-CSCF/IBCF to derive the bandwidth to request from RACS.
In case being present, the b= attribute will correspond to the bandwidth required by the most bandwidth demanding
codec in the list. Hence, the Max-Requested-Bandwidth-UL and -DL shall be set to the value given by the b= attribute
if present.
In case the b= attribute is not present the P-CSCF/IBCF shall set these AVPs according to one of the following rules:
• Set the AVPs to the value locally associated to the codec received in the m= line when only one codec is listed
in the m= line or the highest bandwidth required by the codecs listed in the SDP offer (when multiple codecs
are proposed for this media component).
ETSI
10 ETSI TS 183 048 V2.2.1 (2009-08)
• Set the AVPs to the value locally associated to the codec received in the m= line when only one codec is listed
in the m= line or the lowest bandwidth required by the codecs listed in the SDP offer (when multiple codecs
are proposed for this media component). In this case the Max-Requested-Bandwidth-UL and -DL AVPs may
not reflect the actual bandwidth value that will be negotiated for the session.
• Omit the AVPs and let RACS determine a default bandwidth based on the combination of Reservation-Class
and Media-Type AVPs.
The above-given rules are in line with the description given in annex B (table B.1) of TS 183 017 (Gq') [4] for how to
populate the Max-Requested-Bandwidth-UL and -DL AVPs. These rules provide however more details on how to
populate these AVPs referred to from TS 183 017 [4] in annex B (table B.1).
It should be noted that the above-given rules imply that the Max-Requested-Bandwidth-UL and -DL AVPs may be
modified during the SDP negotiation (i.e. when the codec to be used is finally agreed between the endpoints).
5.1.2 NAPT/NAPT-PT at the P-CSCF/IBCF
Details on NAPT/NAPT-PT operations at the P-CSCF are given in TS 124 229 [8].
The IBCF supports controlled NAPT/NAPT-PT but does not support hosted NAPT/NAPT-PT traversal. That is, the
IBCF is capable of replacing addresses and ports in the SDP as ephemeral terminations are created following the rules
given in clauses 5.2.1.3 and 5.2.1.4, but the IBCF cannot handle address latching as used for hosted NAPT/NAPT-PT
traversal. The P-CSCF is capable of both hosted NAPT/NAPT-PT traversal and controlled NAPT/NAPT-PT.
5.2 Procedures at SPDF
For resource and admission control purposes the SPDF will determine on local policy as specified in TS 183 017 [4]
whether a C-BGF and/or an A-RACF need to be involved in the AF session. The SPDF procedures related to the Gq'
interface involved in supporting NAPT/NAPT-PT services provided by the BGF and in supporting resource and
admission control services provided by the A-RACF are described in TS 183 017 [4]. Based on these procedures this
clause describes the operations of the SPDF involved in co-ordinating requests for these services made over Gq' with
the required signalling over the Ia and Rq interfaces.
The co-ordination of request made over Gq' with the required signalling over the Ia interface is described in
clause 5.2.1, while the co-ordination required between Gq' and the Rq interface is described in clause 5.2.2.
Clause 5.2.3 describes the co-ordination of signalling over the Ia and Rq interfaces.
5.2.1 Reservation with BGF involved
The translation of values not specific to address translation received over Gq' to values used for request made over Ia is
described in clause 5.2.1.1, operations involved in co-ordinating requests for NAPT/NAPT-PT services are described in
clauses 5.2.1.2, 5.2.1.3 and 5.2.1.4, BGF media transcoding is described in clause 5.2.1.5 and BGF transport plane
failure detection is described in clause 5.2.1.6.
5.2.1.1 Resource reservation at the BGF
Upon reception of an initial reservation (SDP offer) the SPDF will extract from the information received with the AAR
the important information in order to reserve resources at the transport layer, different AVPs will be received included
in the AAR, only some of them will be retransmitted over the Ia interface. The aim of this clause is to provide the
transcription for those AVPs:
• The Transport class AVP may be used for pointing to a class of transport services to be applied as detailed in
TS 183 017 [4], in that way it may indicate the DSCP marking and the command syntax over the Ia interface
may be ds/dscp, this information may be sent through the local control descriptor.
• The value of the Reservation priority AVP may be sent over the Ia interface as the priority of the context.
The following table summarizes the population rules for setting context and termination properties, based on received
DIAMETER AVPs and local configuration data.
ETSI
11 ETSI TS 183 048 V2.2.1 (2009-08)
Table 5.2.1.1.1
Context Descriptor Descriptor Descriptor Properties Population rules
parameters
Context ID   Always set by the BGF
Priority   Set from the Reservation-Priority AVP
Indicator
Emergency   Set from the Service Class AVP
Indicator
Term ID  See ES 283 018 [7]
Media
Stream
Local
Control
Mode Set from Flow-Status in Media-Component-Description
and/or Flow-Status in Media-Component.
Media-Sub-Component.
ds/dscp Set from Transport-Class in
Media-Component-Description.
gm/saf Depends on the Service-Class AVP and BGF profile
information.
gm/spf Depends on the Service-Class AVP and BGF profile
information.
gm/sam If gm/saf is set to ON, the gm/sam property is set from
the Flow-Description in Media-Component.
Media-Sub-Component.
gm/spr If gm/spf is set to ON, the gm/spr property is set from
the Flow-Description in Media-Component.
Media-Sub-Component.
gm/rsb Depends on the value of the Media-Type AVP and BGF
profile information.
gm/esas Depends on the Service-Class AVP and whether
NAP-PT is activated.
gm/lsa If gm/esas is set to ON, gm/lsa is set from the address
(c= line) contained in the remote descriptor of the
opposite termination.
gm/esps Depends on the Service-Class AVP and whether
NAP-PT is activated.
gm/lsp If gm/esps is set to ON, gm/lsp is set from the port
(m= line) contained in the remote descriptor of the
opposite termination.
tman/pdr If the Transport-Class corresponds to constant bit rate
traffic, the tman/pdr property shall be equivalent to the
b= line of the local descriptor or absent.
If the Transport-Class corresponds to variable bit rate
traffic, the tman/pdr property shall be equivalent to the
b= line of the local descriptor.
tman/mbs From Reservation-Class AVP
tman/dvt From Reservation-Class AVP
tman/sdr If the Transport-Class corresponds to constant bit rate
traffic, this property shall be omitted or identical to
tman/pdr.
If the Transport-Class corresponds to variable bit rate
traffic this property shall be derived from tman/pdr using
rules specific to the transport class.
tman/pol Set from the Transport-Class AVP.
Local c=
If NAPT-PT is activated, the address shall be assigned
by the BGF. Otherwise the address is set from the
contents of the remote descriptor of the opposite
termination.
See ES 283 018 [7] for the setting of other fields of the
c= line.
ETSI
12 ETSI TS 183 048 V2.2.1 (2009-08)
Context Descriptor Descriptor Descriptor Properties Population rules
parameters
m=
If NAPT-PT is activated, the port shall be assigned by
the BGF. Otherwise the port is set from the contents of
the remote descriptor of the opposite termination.
See ES 283 018 [7] for the setting of other fields of the
m= line.
b=
Shall be set from the Max-Requested-Bandwidth-UL or
Max-Requested-Bandwidth-DL depending on the
termination (upstream or downstream).
(see note)
Remote c=
The address is set from the Flow-Description in
Media-Component. Media-Sub-Component.
See ES 283 018 [7] for the setting of other fields of the
c= line.
m=
The port is set from the Flow-Description in
Media-Component. Media-Sub-Component.
See ES 283 018 [7] for the setting of other fields of the
m= line.
b=
Shall be set from the Max-Requested-Bandwidth-UL or
Max-Requested-Bandwidth-DL depending on the
termination (upstream or downstream).
(see note)
NOTE: If gm/rsb is set to ON, the value of the AVPs associated to the RTCP flow shall be added.

5.2.1.2 Initial reservation for an session (SDP offer)
Upon reception of an initial AAR with connection information, the SPDF shall extract the connection information from
the Media-Component-Description AVP(s).
Each Media-Component-Descriptor AVP received (one per m= line or media stream) contains one or more
Media-Sub-Component AVP(s) carrying a set of Flow-Descriptor AVP(s) that describe a unidirectional IP flow
associated with the media stream.
The SPDF shall from the set of Flow-Descriptor AVP(s) identify the direction of the corresponding IP flows i.e. uplink
or downlink. The direction of each IP flow is given by the value of the direction attribute of the corresponding
Flow-description AVP (i.e. "in" for uplink IP flows, and "out" for downlink IP flows). For each potential requesting
application that requires the services of a BGF, the SPDF shall hold a local mapping table that enables SPDF to ensure,
that both ephemeral terminations created for the session in the BGF are configured with connection information that
matches appropriately the IP flow direction with the network interface connecting the ephemeral termination.
In the P-CSCF case, an uplink IP flow originates from the UE served by the P-CSCF, and a downlink IP flow is
directed towards the UE served by the P-CSCF.
In the IBCF case, an uplink IP flow is directed from the local core network towards the peer core network, and a
downlink IP flow is directed from the peer core network towards the local core network.
The Binding-Input-List AVP shall be populated with an even number of V4-Transport-Address AVP or
V6-Transport-Address list elements. The first list element in each pair of list elements applies to the access side and the
second element applies to the core side. In case one of the V4-Transport-Address AVP or V6-Transport-Address AVP
in such pair is unknown, an even number of list elements shall be still provided with the unknown
V4-Transport-Address AVP or V6-Transport-Address AVP wild-carded.
The above-given rules apply to the P-CSCF but are also valid for the IBCF provided that "access side" is replaced by
"local core side" and "core side" by "peer core side". It shall be one pair of V4-Transport-Address AVP or
V6-Transport-Address list elements in the Binding-Input-List AVP for each single Media-Component-Description AVP
in an AAR. The list of such pairs shall be given in the same order as the list of Media-Component-Description AVPs.
This provides an explicit coupling between each Media-Component-Description AVP, each pair of list elements in the
Binding-Input-List AVP, and each pair of terminations in the BGF.
ETSI
13 ETSI TS 183 048 V2.2.1 (2009-08)
The following description for how to create ephemeral terminations applies to the P-CSCF but is also valid for the IBCF
provided that "access network" is replaced by "local core network" and "core network" by "peer core network".
After selection of the BGF to be contacted for the session, the SPDF requests initial configuration of the BGF to create
a context with two ephemeral terminations:
• ephemeral termination TA connecting the access network to the BGF; and
• ephemeral termination TC connecting the core network to the BGF.
TT TT
AA CC
ULUL LocLocal Coreal Core
AcAccecessss
GaGatete GaGatete
⇔⇔ ⇔⇔
DLDL
PPeer Coreeer Core
LocLocal Core al Core
H.248 ContexH.248 Contextt
H.248 ContexH.248 Contextt
Figure 5.2.1.2.1: BGF connection and flow model representation
For connection information corresponding to a downlink IP flow, the SPDF shall:
• on termination TA:
- define one media stream per Media-Component-Description AVP occurrence (see note 1):
for each media stream:
- set the remote Descriptor to the corresponding destination IP and port address of the
Flow-Description AVP marked with "out" direction and contained in the
Media-Sub-Component AVP for which the Flow-Usage AVP is either absent or set to
"no_information".
• on termination TC:
- define one media stream per Media-Component-Description AVP occurrence (see note 1):
for each media stream:
- if destination address NAPT(-PT) is activated for DL IP flows, request the BGF to select an
IP and port address in the local Descriptor and store the selected value;
- otherwise i.e. if destination address NAPT(-PT) is not activated for DL IP flows, set the local
Descriptor to the value assigned to the remote Descriptor of termination TA;
- optionally, configure the local control Descriptor with the gm/lsa and gm/lsp set to the value
assigned to the remote Descriptor of termination TA (see note 2).
For connection information corresponding to an uplink IP flow, the SPDF shall:
• on termination TC:
- define one media stream per Media-Component-Description AVP occurrence (see note 1):
for each media stream:
- set the remote Descriptor to the corresponding destination IP and port address of the
Flow-Description AVP marked with "in" direction and contained in the
Media-Sub-Component AVP for which the Flow-Usage AVP is either absent or set to
"no_information".
ETSI
14 ETSI TS 183 048 V2.2.1 (2009-08)
• on termination TA:
- define one media stream per Media-Component-Description AVP occurrence (see note 1):
for each media stream:
- if destination address NAPT(-PT) is activated for UL IP flows, request the BGF to select an
IP and port address in the local Descriptor and store the selected value;
- otherwise i.e. if destination address NAPT(-PT) is not activated for UL IP flows, set the local
Descriptor to the value assigned to the remote Descriptor of termination TC;
- Optionally, configure the local control Descriptor with the gm/lsa and gm/lsp properties set to
the value assigned to the Remote Descriptor of termination TC (see note 3).
NOTE 1: The SPDF can also specify additional media stream for RTCP this is described in ES 283 018 [7].
NOTE 2: This ensures that UL IP flows will be sent towards the core network using a source IP and port address
identical to the address used by the UE for sending packets, assuming that the UE sends and receives
packets using the same address and port.
NOTE 3: This ensures that DL IP flows will be sent towards the access network using a source IP and port address
identical to the address used to by the peer for sending packets, assuming that the peer sends and receives
packets using the same address and port.
If destination address NAPT(-PT) is activated for UL and/or DL IP flows, the SPDF shall return in the AAA message
the list of IP and port address(es) selected by the BGF as local Descriptors in the Binding-Output-List AVP for each
media stream in the same order as the corresponding Binding-Input-List AVP of the AAR message. That is, each
address and port pair received in the local Descriptor shall be included in the Binding-Output-List AVP in the same
position as the address and port pair that has been included in the remote Descriptor to which it is connected and was
given in the Binding-Input-List AVP. Note that the addresses and ports in the same positions in the Binding-Input-List
and the Binding-Output-List AVPs correspond to terminations at different sides of the BGF.
5.2.1.3 Connection information received from the opposite direction (SDP answer)
Upon reception of a subsequent AAR with connection information, the SPDF shall extract the connection information
from the Media-Component-Description AVP(s). These operations are performed as described in the previous clause.
The rules for how to populate the Binding-Input-List AVP and its relation to Media-Component-Description AVPs
given in clause 5.2.1.3 apply also to this clause.
The following description for how to create ephemeral terminations applies to the P-CSCF but is also valid for the IBCF
provided that "access network" is replaced by "local core network" and "core network" by "peer core network".
After selection of the BGF to be contacted for the session, the SPDF requests subsequent configuration of the context
created within the BGF.
For connection information corresponding to a downlink IP flow, SPDF shall:
• modify termination TA:
- for each media stream:
set the remote Descriptor to the corresponding destination IP and port address of the
Flow-Description AVP marked with "out" direction and contained in the Media-Sub-Component
AVP for which the Flow-Usage AVP is either absent or set to "no_information".
• modify termination TC:
- for each media stream:
if destination address NAPT(-PT) is activated for DL IP flows, request the BGF to select an IP and
port address in the local Descriptor and store the selected value;
otherwise i.e. if destination address NAPT(-PT) is not activated for DL IP flows, set the local
Descriptor to the value assigned to the remote Descriptor of termination TA;
ETSI
15 ETSI TS 183 048 V2.2.1 (2009-08)
Optionally, configure the local control Descriptor with the gm/lsa and gm/lsp properties set to the
value assigned to the Remote Descriptor of termination TA (see note 2).
For connection information corresponding to an uplink IP flow, the SPDF shall:
• modify termination TC:
- for each media stream:
set the remote Descriptor to the corresponding destination IP and port address of the
Flow-Description AVP marked with "in" direction and contained in the Media-Sub-Component
AVP for which the Flow-Usage AVP is either absent or set to "no_information".
• modify termination TA:
- for each media stream:
if destination address NAPT(-PT) is activated for UL IP flows, request the BGF to select an IP and
port address in the local Descriptor and store the selected value;
otherwise i.e. if destination address NAPT(-PT) is not activated for UL IP flows, set the local
Descriptor to the value assigned to the remote Descriptor of termination TC;
Optionally, configure the local control Descriptor with the gm/lsa and gm/lsp set to the value
assigned to the remote Descriptor of termination TC (see note 1).
NOTE 1: This ensures that DL IP flows will be sent towards the access network using a source IP and port address
identical to the address used to by the peer for sending packets, assuming that the peer sends and receives
packets using the same address and port.
NOTE 2: This ensures that UL IP flows will be sent towards the core network using a source IP and port address
identical to the address used by the UE for sending packets, assuming that the UE sends and receives
packets using the same address and port.
If destination address NAPT(-PT) is activated for UL and/or DL IP flows, the SPDF shall return in the AAA message
the list of IP and port address(es) selected by the BGF as local Descriptors in the Binding-Output-List AVP for each
media stream in the same order as the corresponding Binding-Input-List AVP of the AAR message. That is, each
address and port pair received in the local Descriptor shall be included in the Binding-Output-List AVP in the same
position as the address and port pair that has been included in the remote Descriptor to which it is connected and was
given in the Binding-Input-List AVP. Note that the addresses and ports in the same positions in the Binding-Input-List
and the Binding-Output-List AVPs correspond to terminations at different sides of the BGF.
5.2.1.4 Connection information (SDP answer) received corresponding to multiple
early dialogues
The SPDF may receive more than one AAR with SDP answer connection info in case the AF identifies that multiple
early dialogues are being created. These AAR will be marked with a SIP-Forking-Indication AVP set to value
SEVERAL_DIALOGUES. The SPDF shall request resources from the BGF as if this was an AAR (SDP answer)
without Forking-Indication but shall be prepared to restore QoS requirements for one of the early dialogues. The final
dialogue is identified when an AAR (SDP answer) is received without the SIP-Forking-Indication AVP.
5.2.1.5 BGF Media Transcoding
The BGF media transcoding abilities can be triggered by the Application Function (AF) in order to resolve codec
incompatibilities between UEs or administratively through local configuration in order to enforce the use of specific
codecs within the core network. If used to resolve codec incompatibilities between UEs, the procedures for Media
Transcoding control described in TS 124 229 [8], clause 5.10.7.2 (Media transcoding control procedures) apply.
If used to administratively enforce the use of specific codecs within a core network, local configuration may trigger the
BGF to transcode media going in to and out of the core network.
ETSI
16 ETSI TS 183 048 V2.2.1 (2009-08)
5.2.1.6 BGF transport plane failure detection
When detecting a transport plane event (like loss of RTP on an ephemeral termination), the BGF can send a Notify
command to the SPDF indicating the cause of the event. In order for this to happen, the SPDF must first indicate that it
wishes to be notified about the event in question. This is achieved by including the particular event in the Events
descriptor in an Add or Modify request (depending on the type of event). When the SPDF receives notification of an
event from the BGF, the SPDF can take appropriate action. It notifies the application function (P-CSCF A) which in
turn terminates the session between the affected UEs. It then releases the resources affected by the event.
The AF uses the Specific-Action AVP in the AA-Request to indicate which events it wants to be informed of.
5.2.2 Reservation with x-RACF involved
The SPDF may provide different amounts of information over Rq to the x-RACF depending on the particular service
being requested by the AF over Gq'. For example, for services that do not involve an policy enforcement in the RCEF,
port numbers are not needed and may hence be left out by the SPDF for signalling over Rq although ports numbers are
present in Gq' (and Ia) signalling. However, the recommended behaviour of the SPDF is to always provide complete
information over Rq to the x-RACF. This is to avoid making the SPDF aware of x-RACF operations for different
services and requiring it to operate differently for different services.
Some AVPs are transparently forwarded by the SPDF between the Gq' and Rq interfaces, while SPDF policies are
applied to other AVPs, which consequently may be altered by the SPDF before it signals to the x-RACF. The following
AVPs are forwarded transparently by the SPDF over Rq to the x-RACF:
• Media-Component-Description:
- Media-Component-Number.
- Media-Sub-Component.
- AF-Application-Identifier.
- Media-Type.
- Max-Requested-Bandwidth-UL.
- Max-Requested-Bandwidth-DL.
- Flow-Status.
- RS-Bandwidth.
- RR-Bandwidth.
- Codec-Data.
• Flow-Grouping.
• AF-Charging-Identifier.
• User-Name.
• Globally-Unique-Address.
• Overbooking-indicator.
ETSI
17 ETSI TS 183 048 V2.2.1 (2009-08)
The following AVPs may be altered by the SPDF before signalled to the x-RACF (AVPs with no specific information
on the mapping may be mapped to a different value based on local configuration):
• Media-Component-Description:
- Reservation-Class.
- Reservation-Priority.
- Transport-Class.
- Media-Authorization-Context-Id.
• Specific-Action:
INDICATION_OF_RELEASE_OF_BEARER shall be forwarded without c
...