draft-ietf-sigtran-signalling-over-sctp-applic-07.txt   draft-ietf-sigtran-signalling-over-sctp-applic-08.txt 
INTERNET-DRAFT L. Coene(Ed) INTERNET-DRAFT L. Coene(Ed)
Internet Engineering Task Force Siemens Internet Engineering Task Force Siemens
Issued: January 2003 J. Pastor Issued: March 2003 J. Pastor
Expires: July 2003 Ericsson Expires: September 2003 Ericsson
Telephony Signalling Transport over SCTP applicability statement Telephony Signalling Transport over SCTP applicability statement
< draft-ietf-sigtran-signalling-over-sctp-applic-07.txt> <draft-ietf-sigtran-signalling-over-sctp-applic-08.txt>
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. Internet-Drafts are working all provisions of Section 10 of RFC2026. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas, documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts. working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six Internet-Drafts are draft documents valid for a maximum of six
skipping to change at page 2, line 5 skipping to change at page 2, line 5
Abstract Abstract
This document describes the applicability of the new protocols This document describes the applicability of the new protocols
developed under the signalling transport framework[RFC2719]. A developed under the signalling transport framework[RFC2719]. A
description of the main issues regarding the use of the Stream description of the main issues regarding the use of the Stream
Control Transmission Protocol (SCTP)[RFC2960] and each adaptation Control Transmission Protocol (SCTP)[RFC2960] and each adaptation
layer for transport of telephony signalling information over IP layer for transport of telephony signalling information over IP
infrastructure is explained. infrastructure is explained.
Draft Telephony signalling over SCTP AS January 2003 Draft Telephony Signalling over SCTP AS March 2003
Table of contents Table of contents
Telephony signalling over SCTP Applicability statement ......... ii Telephony signalling over SCTP Applicability statement ......... ii
Chapter 1: Introduction ........................................ 2 Chapter 1: Introduction ........................................ 3
Chapter 1.1: Scope ..... ....................................... 3 Chapter 1.1: Scope ..... ....................................... 3
Chapter 1.2: Terminology ....................................... 3 Chapter 1.2: Terminology ....................................... 3
Chapter 1.3: Contributors ...................................... 3 Chapter 1.3: Contributors ...................................... 4
Chapter 2: SIGTRAN architecture ................................ 4 Chapter 2: SIGTRAN architecture ................................ 4
Chapter 2.1: Overview ......................................... 4 Chapter 2.1: Overview ......................................... 4
Chapter 3: Issues for transporting Telephony signalling Chapter 3: Issues for transporting Telephony signalling
information over SCTP .......................................... 6 information over SCTP .......................................... 6
Chapter 3.1: Congestion control ................................ 6 Chapter 3.1: Congestion control ................................ 6
Chapter 3.2: Detection of failures ............................. 6 Chapter 3.2: Detection of failures ............................. 6
Chapter 3.2.1: Retransmission TimeOut (RTO) calculation ........ 7 Chapter 3.2.1: Retransmission TimeOut (RTO) calculation ........ 7
Chapter 3.2.2: Heartbeat ....................................... 7 Chapter 3.2.2: Heartbeat ....................................... 7
Chapter 3.2.3: Maximum Number of retransmissions ............... 7 Chapter 3.2.3: Maximum Number of retransmissions ............... 7
Chapter 3.3: Shorten end-to-end message delay ................. 7 Chapter 3.3: Shorten end-to-end message delay ................. 8
Chapter 3.4: Bundling considerations ........................... 8 Chapter 3.4: Bundling considerations ........................... 8
Chapter 3.5: Stream Usage ...................................... 8 Chapter 3.5: Stream Usage ...................................... 8
Chapter 4: User Adaptation Layers............................... 8 Chapter 4: User Adaptation Layers............................... 8
Chapter 4.1: Access Signalling.................................. 11 Chapter 4.1: Access Signalling.................................. 11
Chapter 4.1.1: IUA (ISDN Q.921 User Adaptation) ................ 11 Chapter 4.1.1: IUA (ISDN Q.921 User Adaptation) ................ 11
Chapter 4.1.2: V5UA (V5.2-User Adaptation) Layer ............... 12 Chapter 4.1.2: V5UA (V5.2-User Adaptation) Layer ............... 12
Chapter 4.1.3: DUA (DPNSS/DASS User adaptation) Layer .......... 13 Chapter 4.1.3: DUA (DPNSS/DASS User adaptation) Layer .......... 13
Chapter 4.2: Network Signalling ................................ 13 Chapter 4.2: Network Signalling ................................ 14
Chapter 4.2.1: MTP lvl3 over IP ................................ 14 Chapter 4.2.1: MTP lvl3 over IP ................................ 14
Chapter 4.2.1.1: M2UA (SS7 MTP2-User Adaptation) Layer ......... 14 Chapter 4.2.1.1: M2UA (SS7 MTP2-User Adaptation) Layer ......... 14
Chapter 4.2.1.2: M2PA (SS7 MTP2-User Peer-to-Peer Adaptation) .. 15 Chapter 4.2.1.2: M2PA (SS7 MTP2-User Peer-to-Peer Adaptation) .. 15
Chapter 4.2.1.3: Main difference between M2PA and M2UA ......... 16 Chapter 4.2.1.3: Main difference between M2PA and M2UA ......... 16
Chapter 4.2.2: M3UA (SS7 MTP3 User Adaptation) Layer ........... 17 Chapter 4.2.2: M3UA (SS7 MTP3 User Adaptation) Layer ........... 17
Chapter 4.2.3: SUA (SS7 SCCP User Adaptation) Layer ............ 18 Chapter 4.2.3: SUA (SS7 SCCP User Adaptation) Layer ............ 18
Chapter 5: Security considerations ............................. 20 Chapter 5: Security considerations ............................. 20
Chapter 6: References and related work ......................... 20 Chapter 6: References and related work ......................... 20
Chapter 7: Acknowledgments ..................................... 21 Chapter 7: Acknowledgments ..................................... 21
Chapter 8: Author's address .................................... 22 Chapter 8: Author's address .................................... 22
1 INTRODUCTION Draft Telephony Signalling over SCTP AS March 2003
Draft Telephony signalling over SCTP AS January 2003 1 INTRODUCTION
This document intends to inform how to transport telephony This document intends to inform how to transport telephony
signalling protocols, used in classic telephony systems, over IP signalling protocols, used in classic telephony systems, over IP
networks. The whole architecture is called SIGTRAN (Signalling networks. The whole architecture is called SIGTRAN (Signalling
Transport) as described in RFC2719 and is composed of a transport Transport) as described in RFC2719 and is composed of a transport
protocol(SCTP) and several User Adaptation layers(UAL). The protocol(SCTP) and several User Adaptation layers(UAL). The
transport protocol SCTP has been been developed to fulfill the transport protocol SCTP has been been developed to fulfill the
stringent requirements that telephony signalling networks have. The stringent requirements that telephony signalling networks have. The
set of User Adaptation layers have also been introduced to make it set of User Adaptation layers have also been introduced to make it
possible that different signalling protocols can use the SCTP layer. possible that different signalling protocols can use the SCTP layer.
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UAL: User adaptation layer: the protocol that encapsulate the upper UAL: User adaptation layer: the protocol that encapsulate the upper
layer telephony signalling protocols that are to be transported over layer telephony signalling protocols that are to be transported over
SCTP/IP. SCTP/IP.
ISEP: IP signalling endpoint: a IP node that implements SCTP and a ISEP: IP signalling endpoint: a IP node that implements SCTP and a
User adapatation layer. User adapatation layer.
SP: signalling point SP: signalling point
1.3 Contributors Draft Telephony Signalling over SCTP AS March 2003
Draft Telephony signalling over SCTP AS January 2003 1.3 Contributors
The following people contributed to the document: L. Coene(Editor), The following people contributed to the document: L. Coene(Editor),
M. Tuexen, G. Verwimp, J. Loughney, R.R. Stewart, Qiaobing Xie, M. Tuexen, G. Verwimp, J. Loughney, R.R. Stewart, Qiaobing Xie,
M. Holdrege, M.C. Belinchon, A. Jungmaier, J. Pastor and L. Ong. M. Holdrege, M.C. Belinchon, A. Jungmaier, J. Pastor and L. Ong.
2 SIGTRAN architecture 2 SIGTRAN architecture
The SIGTRAN architecture describes the transport of signalling The SIGTRAN architecture describes the transport of signalling
information over IP infrastructure. information over IP infrastructure.
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performance requirements. performance requirements.
(3) The standard Internet Protocol. (3) The standard Internet Protocol.
The telephony signalling protocols to be transported can be: The telephony signalling protocols to be transported can be:
- SS7 MTP3 users: SCCP, ISUP, TUP... - SS7 MTP3 users: SCCP, ISUP, TUP...
- SS7 MTP2 users: MTP3 - SS7 MTP2 users: MTP3
- SS7 SCCP users: RANAP, MAP(+TCAP), INAP(+TCAP)... Draft Telephony Signalling over SCTP AS March 2003
Draft Telephony signalling over SCTP AS January 2003 - SS7 SCCP users: RANAP, MAP(+TCAP), INAP(+TCAP)...
- ISDN Q.921 users: Q.931 - ISDN Q.921 users: Q.931
- V5.2/DSS1 - V5.2/DSS1
- .... - ....
Every classic telephony protocol can have a corresponding UAL Every classic telephony protocol can have a corresponding UAL
developed. developed.
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- Support of multi-homing for added reliability - Support of multi-homing for added reliability
- Protection against blind denial-of-service attacks - Protection against blind denial-of-service attacks
- Protection against blind masquerade attacks - Protection against blind masquerade attacks
SCTP is used as the transport protocol for telephony signalling SCTP is used as the transport protocol for telephony signalling
applications. Message boundaries are preserved during data applications. Message boundaries are preserved during data
transport by SCTP and so each UAL can specify its own message transport by SCTP and so each UAL can specify its own message
structure withing the SCTP user data. The SCTP user data can be structure within the SCTP user data. The SCTP user data can be
Draft Telephony Signalling over SCTP AS March 2003
delivered by the order of transmission within a stream(in sequence delivered by the order of transmission within a stream(in sequence
delivery) or unordered. delivery) or unordered.
Draft Telephony signalling over SCTP AS January 2003
SCTP can be used to provide redundancy at the SCTP can be used to provide redundancy at the
transport layer and below. Telephony applications needing this level transport layer and below. Telephony applications needing this level
of redundancy can make use of SCTP's multi-homing support. of redundancy can make use of SCTP's multi-homing support.
SCTP can be used for telephony applications where head-of-line SCTP can be used for telephony applications where head-of-line
blocking is a concern. Such an application should use multiple blocking is a concern. Such an application should use multiple
streams to provide independent ordering of telephony signalling streams to provide independent ordering of telephony signalling
messages. messages.
3 Issues for transporting telephony signalling over SCTP 3 Issues for transporting telephony signalling over SCTP
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Some telephony signalling applications may have their own congestion Some telephony signalling applications may have their own congestion
control and flow control techniques. These techniques may interact control and flow control techniques. These techniques may interact
with the congestion control procedures in SCTP. with the congestion control procedures in SCTP.
3.2 Detection of failures 3.2 Detection of failures
Telephony systems often must have no single point of failure in Telephony systems often must have no single point of failure in
operation. operation.
Draft Telephony Signalling over SCTP AS March 2003
The UAL must meet certain service availability and performance The UAL must meet certain service availability and performance
requirements according to the classical signalling layers they are requirements according to the classical signalling layers they are
Draft Telephony signalling over SCTP AS January 2003
replacing. Those requirements may be specific for each UAL. replacing. Those requirements may be specific for each UAL.
For example, telephony systems are often required to be able to For example, telephony systems are often required to be able to
preserve stable calls during a component failure. Therefore error preserve stable calls during a component failure. Therefore error
situations at the transport layer and below must be detected quickly situations at the transport layer and below must be detected quickly
so that the UAL can take approriate steps to recover and preserve the so that the UAL can take approriate steps to recover and preserve the
calls. This poses special requirements on SCTP to discover calls. This poses special requirements on SCTP to discover
unreachablility of a destination address or a peer. unreachablility of a destination address or a peer.
3.2.1 Retransmission TimeOut (RTO) calculation 3.2.1 Retransmission TimeOut (RTO) calculation
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HB.interval. It should be noted this might result in a higher traffic HB.interval. It should be noted this might result in a higher traffic
load. load.
3.2.3 Maximum number of retransmissions 3.2.3 Maximum number of retransmissions
Setting Path.Max.Retrans and Association.Max.Retrans SCTP parameters Setting Path.Max.Retrans and Association.Max.Retrans SCTP parameters
to lower values will speed up both destination address and peer to lower values will speed up both destination address and peer
failure detection. However, if these values are set too low, the failure detection. However, if these values are set too low, the
probability of false fault detections might increase. probability of false fault detections might increase.
Draft Telephony signalling over SCTP AS January 2003 Draft Telephony Signalling over SCTP AS March 2003
3.3 Shorten end-to-end message delay 3.3 Shorten end-to-end message delay
Telephony applications often require short end-to-end message Telephony applications often require short end-to-end message
delays. The method described in section 3.2.1 on lowering RTO may delays. The method described in section 3.2.1 on lowering RTO may
be considered. The different paths within a single association will be considered. The different paths within a single association will
have a different RTO, so using the path with the lowest RTO will have a different RTO, so using the path with the lowest RTO will
lead to a shorter end-to-end message delay for the application lead to a shorter end-to-end message delay for the application
running on top of the UAL's. running on top of the UAL's.
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There are UALs for both access signalling (DSS1) and trunk signalling There are UALs for both access signalling (DSS1) and trunk signalling
(SS7). A brief description of the standardized UALs follows in the (SS7). A brief description of the standardized UALs follows in the
next sub-sections. next sub-sections.
The delivery mechanism in the several UALs The delivery mechanism in the several UALs
- Supports seamless operation of UALs user peers over an IP - Supports seamless operation of UALs user peers over an IP
network connection. network connection.
Draft Telephony Signalling over SCTP AS March 2003
- Supports the interface boundary that the UAL user had with the - Supports the interface boundary that the UAL user had with the
traditional lower layer. traditional lower layer.
Draft Telephony signalling over SCTP AS January 2003
- Supports management of SCTP transport associations and traffic - Supports management of SCTP transport associations and traffic
between SGs and ISEPs or two ISEPs between SGs and ISEPs or two ISEPs
- Supports asynchronous reporting of status changes to management. - Supports asynchronous reporting of status changes to management.
Signalling User Adaptation Layers have been developed for both: Signalling User Adaptation Layers have been developed for both:
Access and Trunk Telephony Signalling. They are defined as follows. Access and Trunk Telephony Signalling. They are defined as follows.
Access Signalling: This is the signalling that is needed between and Access Signalling: This is the signalling that is needed between and
access device and an exchange in the core network in order to access device and an exchange in the core network in order to
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designed UALS are: designed UALS are:
- ISDN Q.921 Users: Q.931 - ISDN Q.921 Users: Q.931
- V5.2/DSS1 - V5.2/DSS1
- DPNSS/DASS2 - DPNSS/DASS2
- SS7 MTP3 Users: SCCP, ISUP, TUP - SS7 MTP3 Users: SCCP, ISUP, TUP
- SS7 MTP2 Users: MTP3 - SS7 MTP2 Users: MTP3
- SS7 SCCP Users: TCAP, RANAP, BSSAP, ... - SS7 SCCP Users: TCAP, RANAP, BSSAP, ...
Two main scenarios have been developed to use the different UALS for Two main scenarios have been developed to use the different UALS for
IP Signalling Transport:
Draft Telephony signalling over SCTP AS January 2003 Draft Telephony Signalling over SCTP AS March 2003
IP Signalling Transport:
(1) Intercommunication of traditional Signalling transport nodes and (1) Intercommunication of traditional Signalling transport nodes and
IP based nodes. IP based nodes.
Traditional Telephony Traditional Telephony
Telephony Signalling Telephony Signalling
********* Signalling ********** over IP ******** ********* Signalling ********** over IP ********
* SEP *----------------* SG *--------------* ISEP * * SEP *----------------* SG *--------------* ISEP *
********* ********** ******** ********* ********** ********
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| | | +----+ +-------+ | | | +----+ +-------+
| TTST | |TTST|SCTP| | SCTP | | TTST | |TTST|SCTP| | SCTP |
| | | +----+ +-------+ | | | +----+ +-------+
| | | | IP | | IP | | | | | IP | | IP |
+-------+ +---------+ +-------+ +-------+ +---------+ +-------+
SEP - Signalling Endpoint SEP - Signalling Endpoint
SG - Signalling Gateway SG - Signalling Gateway
ISEP - IP Signalling Endpoint ISEP - IP Signalling Endpoint
SigProt - Signalling Protocol SigProt - Signalling Protocol
TTST - Traditional Telephony Signalling Transport TTSP - Traditional Telephony Signalling Protocol
UAL - User Adaptation Layer UAL - User Adaptation Layer
SCTP - Stream Control Transport Protocol SCTP - Stream Control Transport Protocol
It is also referred as SG to AS communication. AS I the name that It is also referred as SG to AS communication. AS is the name that
UAL usually gives to the ISEP nodes. It stands for Application UAL usually gives to the ISEP nodes. It stands for Application
Server. Server.
(2) Communication inside the IP network. (2) Communication inside the IP network.
Telephony Telephony
Signalling Signalling
********* over IP ********* ********* over IP *********
* ISEP *------------------* ISEP * * ISEP *------------------* ISEP *
********* ********* ********* *********
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+-------+ +-------+ +-------+ +-------+
|SigProt| |SigProt| |SigProt| |SigProt|
+-------+ +-------+ +-------+ +-------+
| UAL | | UAL | | UAL | | UAL |
+-------+ +-------+ +-------+ +-------+
| SCTP | | SCTP | | SCTP | | SCTP |
+-------+ +-------+ +-------+ +-------+
| IP | | IP | | IP | | IP |
+-------+ +-------+ +-------+ +-------+
This is also referred to as IPSP communication. IPSP is the name Draft Telephony Signalling over SCTP AS March 2003
Draft Telephony signalling over SCTP AS January 2003
of the role that an UAL plays on an IP-based node. It stands for This is also referred to as IPSP communication. IPSP stands for IP
IP Signalling Point. Signalling Point and describes the role that the UAL plays on a
IP-based node.
The first scenario is applied for both types of signalling (access The first scenario is applied for both types of signalling (access
and trunk signalling). On the other hand the peer to peer basis can and trunk signalling). On the other hand the peer to peer basis can
only be used for trunk signalling. only be used for trunk signalling.
4.1 Access Signalling 4.1 Access Signalling
The SIGTRAN WG have developed UALs to transport the following Access The SIGTRAN WG have developed UALs to transport the following Access
Signalling protocols: Signalling protocols:
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UAL: IUA (ISDN Q.921 User Adaptation) UAL: IUA (ISDN Q.921 User Adaptation)
This document supports both ISDN Primary Rate Access (PRA) as well as This document supports both ISDN Primary Rate Access (PRA) as well as
Basic Rate Access (BRA) including the support for both point-to-point Basic Rate Access (BRA) including the support for both point-to-point
and point-to-multipoint modes of communication. This support and point-to-multipoint modes of communication. This support
includes Facility Associated Signalling (FAS), Non-Facility includes Facility Associated Signalling (FAS), Non-Facility
Associated Signalling (NFAS) and NFAS with backup D channel. Associated Signalling (NFAS) and NFAS with backup D channel.
It implements the client/server architecture. The default orientation It implements the client/server architecture. The default orientation
would be for the SG to take on the role of server while the ISEP is is for the SG to take on the role of server while the ISEP is
the client. The SCTP (and UDP/TCP) Registered User Port Number the client. The SCTP (and UDP/TCP) Registered User Port Number
Assignment for IUA is 9900. Assignment for IUA is 9900.
Examples of the upper layers to be transported would be Q.931 and Examples of the upper layers to be transported are Q.931 and QSIG.
QSIG.
The main scenario supported by this UAL is the SG to ISEP The main scenario supported by this UAL is the SG to ISEP
communication where the ISEP role is typically played by a node communication where the ISEP role is typically played by a node
called MGC defined in [RFC2719]. called an MGC, as defined in [RFC2719].
****** ISDN ****** IP ******* ****** ISDN ****** IP *******
*PBX *---------------* SG *--------------* MGC * *PBX *---------------* SG *--------------* MGC *
****** ****** ******* ****** ****** *******
+-----+ +-----+ +-----+ +-----+
|Q.931| (NIF) |Q.931| |Q.931| (NIF) |Q.931|
+-----+ +----------+ +-----+ +-----+ +----------+ +-----+
| | | | IUA| | IUA | | | | | IUA| | IUA |
| | | +----+ +-----+ | | | +----+ +-----+
|Q.921| |Q.921|SCTP| |SCTP | |Q.921| |Q.921|SCTP| |SCTP |
| | | +----+ +-----+ | | | +----+ +-----+
| | | | IP | | IP | | | | | IP | | IP |
+-----+ +-----+----+ +-----+ +-----+ +-----+----+ +-----+
Draft Telephony signalling over SCTP AS January 2003 Draft Telephony Signalling over SCTP AS March 2003
NIF - Nodal Interworking Function NIF - Nodal Interworking Function
PBX - Private Branch Exchange PBX - Private Branch Exchange
SCTP - Stream Control Transmission Protocol SCTP - Stream Control Transmission Protocol
IUA - ISDN User Adaptation Layer Protocol IUA - ISDN User Adaptation Layer Protocol
The SCTP (and UDP/TCP) Registered User Port Number Assignment for IUA The SCTP (and UDP/TCP) Registered User Port Number Assignment for IUA
is 9900. is 9900.
The value assigned by IANA for the Payload Protocol Identifier in the The value assigned by IANA for the Payload Protocol Identifier in the
SCTP Payload Data chunk is 1 SCTP Payload Data chunk is "1".
4.1.2 V5UA over IP 4.1.2 V5UA over IP
UAL: V5UA (V5.2-User Adaptation) UAL: V5UA (V5.2-User Adaptation)
It is an extension from the IUA layer with the modifications needed It is an extension from the IUA layer with the modifications needed
to support the differences between Q.921 / Q.931, and V5.2 layer 2 / to support the differences between Q.921 / Q.931, and V5.2 layer 2 /
layer 3. It supports analog telephone access, ISDN basic rate access layer 3. It supports analog telephone access, ISDN basic rate access
and ISDN primary rate access over a V5.2 interface. It is basically and ISDN primary rate access over a V5.2 interface. It is typically
implemented in an interworking scenario with SG. implemented in an interworking scenario with SG.
****** V5.2 ****** IP ******* ****** V5.2 ****** IP *******
* AN *---------------* SG *--------------* MGC * * AN *---------------* SG *--------------* MGC *
****** ****** ******* ****** ****** *******
+-----+ +-----+ +-----+ +-----+
|V5.2 | (NIF) |V5.2 | |V5.2 | (NIF) |V5.2 |
+-----+ +----------+ +-----+ +-----+ +----------+ +-----+
| | | |V5UA| |V5UA | | | | |V5UA| |V5UA |
| | | +----+ +-----+ | | | +----+ +-----+
|LAPV5| |LAPV5|SCTP| |SCTP | |LAPV5| |LAPV5|SCTP| |SCTP |
| | | +----+ +-----+ | | | +----+ +-----+
| | | | IP + | IP | | | | | IP + | IP |
+-----+ +-----+----+ +-----+ +-----+ +-----+----+ +-----+
AN Access Network AN - Access Network
NIF Nodal Interworking Function NIF - Nodal Interworking Function
LAPV5 Link Access Protocol for the V5 channel LAPV5 - Link Access Protocol for the V5 channel
SCTP - Stream Control Transmission Protocol SCTP - Stream Control Transmission Protocol
The SCTP (and UDP/TCP) Registered User Port Number Assignment for The SCTP (and UDP/TCP) Registered User Port Number Assignment for
V5UA is 5675. V5UA is 5675.
Draft Telephony signalling over SCTP AS January 2003 Draft Telephony Signalling over SCTP AS March 2003
The value assigned by IANA for the Payload Protocol Identifier in the The value assigned by IANA for the Payload Protocol Identifier in the
SCTP Payload Data chunk is "6". SCTP Payload Data chunk is "6".
4.1.3 DPNSS/DASS2 over IP 4.1.3 DPNSS/DASS2 over IP
UAL: DUA (DPNSS/DASS2 User Adaptation) UAL: DUA (DPNSS/DASS2 User Adaptation)
The DUA is built on top of IUA defining the necessary extensions to The DUA is built on top of IUA and defines the necessary extensions
IUA for a DPNSS/DASS2 transport. DPNSS stands for Digital Private to IUA for a DPNSS/DASS2 transport. DPNSS stands for Digital Private
Network Signalling System and DASS2 for Digital Access Signalling Network Signalling System and DASS2 for Digital Access Signalling
System No 2 System No 2.
****** DPNSS ****** IP ******* ****** DPNSS ****** IP *******
*PBX *---------------* SG *--------------* MGC * *PBX *---------------* SG *--------------* MGC *
****** ****** ******* ****** ****** *******
+-----+ +-----+ +-----+ +-----+
|DPNSS| (NIF) |DPNSS| |DPNSS| (NIF) |DPNSS|
| L3 | | L3 | | L3 | | L3 |
+-----+ +-----+----+ +-----+ +-----+ +-----+----+ +-----+
| | | | DUA| | DUA | | | | | DUA| | DUA |
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| | | +----+ +-----+ | | | +----+ +-----+
| | | | IP + | IP | | | | | IP + | IP |
+-----+ +-----+----+ +-----+ +-----+ +-----+----+ +-----+
PBX - Private Branch eXchange PBX - Private Branch eXchange
NIF - Nodal Interworking function NIF - Nodal Interworking function
SCTP - Stream Control Transmission Protocol SCTP - Stream Control Transmission Protocol
DUA - DPNSS User Adaptation Layer Protocol DUA - DPNSS User Adaptation Layer Protocol
The value assigned by IANA for the Payload Protocol Identifier in the The value assigned by IANA for the Payload Protocol Identifier in the
SCTP Payload Data chunk is "TBD". SCTP Payload Data chunk is "10".
Draft Telephony Signalling over SCTP AS March 2003
4.2 Network Signalling 4.2 Network Signalling
The SIGTRAN WG have developed UALs to transport the following SS7 The SIGTRAN WG have developed UALs to transport the following SS7
protocols: protocols:
- MTP2 Users: MTP3 - MTP2 Users: MTP3
- MTP3 Users: ISUP, TUP, SCCP - MTP3 Users: ISUP, TUP, SCCP
- SCCP Users: TCAP, RNSAP, RANAP, BSSAP, ... - SCCP Users: TCAP, RNSAP, RANAP, BSSAP, ...
4.2.1 MTP lvl3 over IP 4.2.1 MTP lvl3 over IP
Draft Telephony signalling over SCTP AS January 2003
UALs: UALs:
- M2UA (SS7 MTP2 User Adaptation) - M2UA (SS7 MTP2 User Adaptation)
- M2PA (SS7 MTP2-User Peer-to-Peer Adaptation) - M2PA (SS7 MTP2-User Peer-to-Peer Adaptation)
4.2.1.1 M2UA (SS7 MTP2 User Adaptation) 4.2.1.1 M2UA (SS7 MTP2 User Adaptation)
M2UA protocol is mainly used between a Signalling Gateway (SG) and M2UA protocol is typically used between a Signalling Gateway (SG)
Media Gateway Controller (MGC). The SG will terminate up to MTP Level and Media Gateway Controller (MGC). The SG will terminate up to MTP
2 and the MGC will terminate MTP Level 3 and above. In other words, Level 2 and the MGC will terminate MTP Level 3 and above. In other
the SG will transport MTP Level 3 messages over an IP network to a words, the SG will transport MTP Level 3 messages over an IP network
MGC. to a MGC.
The only SS7 MTP2 User is MTP3 that is the protocol transported by MTP3 and MTP3b are the the only SS7 MTP2 User protocols that is
this UAL. transported by this UAL.
The SG provides a interworking of transport functions with the IP The SG provides a interworking of transport functions with the IP
transport, in order to transfer the MTP2-User signalling messages to transport to transfer MTP2-User signalling messages with an
and from an Application Server (e.g. MGC) where the peer MTP2- Application Server (e.g. MGC) where the peer MTP2-User exists.
User protocol layer exists.
****** SS7 ****** IP ******* ****** SS7 ****** IP *******
*SEP *-----------* SG *-------------* MGC * *SEP *-----------* SG *-------------* MGC *
****** ****** ******* ****** ****** *******
+----+ +----+ +----+ +----+
|S7UP| |S7UP| |S7UP| |S7UP|
+----+ +----+ +----+ +----+
|MTP3| |MTP3| |MTP3| |MTP3|
| | (NIF) | | | | (NIF) | |
+----+ +----+----+ +----+ +----+ +----+----+ +----+
| | | |M2UA| |M2UA| | | | |M2UA| |M2UA|
| | | +----+ +----+ | | | +----+ +----+
|MTP2| |MTP2|SCTP| |SCTP| |MTP2| |MTP2|SCTP| |SCTP|
| | | +----+ +----+ | | | +----+ +----+
| | | |IP | |IP | | | | |IP | |IP |
+----+ +---------+ +----+ +----+ +---------+ +----+
Draft Telephony Signalling over SCTP AS March 2003
MGC - Media Gateway Controler MGC - Media Gateway Controler
SG - Signalling Gateway SG - Signalling Gateway
SEP - SS7 Signalling Endpoint SEP - SS7 Signalling Endpoint
NIF - Nodal Interworking Function NIF - Nodal Interworking Function
IP - Internet Protocol IP - Internet Protocol
SCTP - Stream Control Transmission Protocol SCTP - Stream Control Transmission Protocol
The SCTP (and UDP/TCP) Registered User Port Number Assignment for The SCTP (and UDP/TCP) Registered User Port Number Assignment for
M2UA is 2904. M2UA is 2904.
Draft Telephony signalling over SCTP AS January 2003
The value assigned by IANA for the Payload Protocol Identifier in the The value assigned by IANA for the Payload Protocol Identifier in the
SCTP Payload Data chunk is "2" SCTP Payload Data chunk is "2".
4.2.1.2 M2PA (SS7 MTP2-User Peer-to-Peer Adaptation) Layer 4.2.1.2 M2PA (SS7 MTP2-User Peer-to-Peer Adaptation) Layer
M2PA protocol is used between SS7 Signalling Points employing the MTP M2PA protocol is used between SS7 Signalling Points employing the MTP
Level 3 protocol. The SS7 Signalling Points may also employ standard Level 3 protocol. The SS7 Signalling Points may also use standard
SS7 links using the SS7 MTP Layer 2 to provide transport of MTP Layer SS7 links using the SS7 MTP Level 2 to provide transport of MTP Level
3 signalling messages. 3 signalling messages.
Both configurations: intercommunication of SS7 and IP with SG and Both configurations: communication of SS7 and IP with SG and
communication between ISEPs are possible. communication between ISEPs are possible.
Communication between two IP nodes: Communication between two IP nodes:
******** IP ******** ******** IP ********
* IPSP *--------* IPSP * * IPSP *--------* IPSP *
******** ******** ******** ********
+------+ +------+ +------+ +------+
| TCAP | | TCAP | | TCAP | | TCAP |
skipping to change at page 15, line 44 skipping to change at page 16, line 5
+------+ +------+ +------+ +------+
| SCTP | | SCTP | | SCTP | | SCTP |
+------+ +------+ +------+ +------+
| IP | | IP | | IP | | IP |
+------+ +------+ +------+ +------+
IP - Internet Protocol IP - Internet Protocol
IPSP - IP Signalling Point IPSP - IP Signalling Point
SCTP - Stream Control Transmission Protocol SCTP - Stream Control Transmission Protocol
Interconnection of SS7 and IP nodes: Draft Telephony Signalling over SCTP AS March 2003
Draft Telephony signalling over SCTP AS January 2003 Connection of SS7 and IP nodes:
******** SS7 *************** IP ******** ******** SS7 *************** IP ********
* SEP *--------* SG *--------* IPSP * * SEP *--------* SG *--------* IPSP *
******** *************** ******** ******** *************** ********
+------+ +------+ +------+ +------+
| TCAP | | TCAP | | TCAP | | TCAP |
+------+ +------+ +------+ +------+
| SCCP | | SCCP | | SCCP | | SCCP |
+------+ +-------------+ +------+ +------+ +-------------+ +------+
skipping to change at page 16, line 37 skipping to change at page 16, line 39
These figures are only an example. Other configurations are possible. These figures are only an example. Other configurations are possible.
For example, IPSPs without traditional SS7 links could use the For example, IPSPs without traditional SS7 links could use the
protocol layers MTP3/M2PA/SCTP/IP to route SS7 messages in a network protocol layers MTP3/M2PA/SCTP/IP to route SS7 messages in a network
with all IP links. with all IP links.
Another example is that two SGs could be connected over an IP network Another example is that two SGs could be connected over an IP network
to form an SG mated pair similar to the way STPs are provisioned in to form an SG mated pair similar to the way STPs are provisioned in
traditional SS7 networks. traditional SS7 networks.
The SCTP (and UDP/TCP) Registered User Port Number Assignment for The SCTP (and UDP/TCP) Registered User Port Number Assignment for
M2PA is TBD. M2PA is 3565.
The value assigned by IANA for the Payload Protocol Identifier in the The value assigned by IANA for the Payload Protocol Identifier in the
SCTP Payload Data chunk is TBD SCTP Payload Data chunk is "5".
4.2.1.3 Main differences between M2PA and M2UA: 4.2.1.3 Main differences between M2PA and M2UA:
a. M2PA: IPSP processes MTP3/MTP2 primitives. a. M2PA: IPSP processes MTP3/MTP2 primitives.
M2UA: MGC transports MTP3/MTP2 primitives between the SG's MTP2 M2UA: MGC transports MTP3/MTP2 primitives between the SG's MTP2
and the MGC's MTP3 (via the NIF) for processing. and the MGC's MTP3 (via the NIF) for processing.
b. M2PA: SG-IPSP connection is an SS7 link. b. M2PA: SG-IPSP connection is an SS7 link.
M2UA: SG-MGC connection is not an SS7 link. It is an M2UA: SG-MGC connection is not an SS7 link. It is an
extension of MTP to a remote entity. extension of MTP to a remote entity.
c. M2PA: SG is an SS7 node with a point code. Draft Telephony Signalling over SCTP AS March 2003
M2UA: SG is not an SS7 node and has no point code.
d. M2PA: SG can have upper SS7 layers, e.g., SCCP.
M2UA: SG does not have upper SS7 layers since it has no MTP3.
Draft Telephony signalling over SCTP AS January 2003
e. M2PA: relies on MTP3 for management procedures.
M2UA: uses M2UA management procedures.
4.3 MTP lvl3-Users (ISUP, TUP, SCCP) over IP 4.3 MTP lvl3-Users (ISUP, TUP, SCCP) over IP
UAL: M3UA (SS7 MTP3 User Adaptation) UAL: M3UA (SS7 MTP3 User Adaptation)
M3UA protocol supports the transport of any SS7 MTP3-User signalling M3UA protocol supports the transport of any SS7 MTP3-User signalling
such as TUP, ISUP and SCCP over IP using the services of SCTP. such as TUP, ISUP and SCCP over IP using the services of SCTP.
Interconnection of SS7 and IP nodes: Interconnection of SS7 and IP nodes:
skipping to change at page 17, line 37 skipping to change at page 18, line 5
+------| +------+-+------+ +------+ +------| +------+-+------+ +------+
| MTP2 | | MTP2 | | SCTP | | SCTP | | MTP2 | | MTP2 | | SCTP | | SCTP |
+------+ +------+ +------+ +------+ +------+ +------+ +------+ +------+
| L1 | | L1 | | IP | | IP | | L1 | | L1 | | IP | | IP |
+------+ +------+ +------+ +------+ +------+ +------+ +------+ +------+
SEP - SS7 Signalling End Point SEP - SS7 Signalling End Point
SCTP - Stream Control Transmission Protocol SCTP - Stream Control Transmission Protocol
NIF - Nodal Interworking Function NIF - Nodal Interworking Function
Communication between two IP nodes: Draft Telephony Signalling over SCTP AS March 2003
Draft Telephony signalling over SCTP AS January 2003 Communication between two IP nodes:
******** IP ******** ******** IP ********
* IPSP *----------* IPSP * * IPSP *----------* IPSP *
******** ******** ******** ********
+------+ +------+ +------+ +------+
|SCCP- | |SCCP- | |SCCP- | |SCCP- |
| User | | User | | User | | User |
+------+ +------+ +------+ +------+
| SCCP | | SCCP | | SCCP | | SCCP |
+------+ +------+ +------+ +------+
| M3UA | | M3UA | | M3UA | | M3UA |
+------+ +------+ +------+ +------+
| SCTP | | SCTP | | SCTP | | SCTP |
+------+ +------+ +------+ +------+
| IP | | IP | | IP | | IP |
+------+ +------+ +------+ +------+
It works using the client-server philosophy. ISEP is recommended to M3UA uses a client-server architecture. It is recommended that the
be client when talking with a SG. The reserved port by IANA is 2905 ISEP acts as the client and initiate the SCTP assocaitions with the
to listen to possible client connections. SG. The port reserved by IANA is 2905. This is the port upon which
the SG should listen for possible client connections.
The assigned payload protocol identifier for the SCTP DATA chunks is The assigned payload protocol identifier for the SCTP DATA chunks is
3. "3".
4.4 SCCP-Users over IP 4.4 SCCP-Users over IP
UAL: SUA (SS7 SCCP User Adaptation) UAL: SUA (SS7 SCCP User Adaptation)
SUA protocol supports the transport of any SS7 SCCP-User signalling SUA protocol supports the transport of any SS7 SCCP-User signalling
such as MAP, INAP, SMS, BSSAP, RANAP over IP using the services of such as MAP, INAP, SMS, BSSAP, RANAP over IP using the services of
SCTP. SUA can support only non-call related signalling. SCTP. Each of the applications using SUA have their own set of
timing requirements that can be found in their respective
standards documents.
SUA does not pose stringent timing constraints on SCTP due to the Draft Telephony Signalling over SCTP AS March 2003
fact that SUA applications have broad timing requirement (from 10 of
seconds to hours) which the applications guard themselves and the
timing supervision of the application is end-to-end, not hop-by-
hop(as with ISUP).
Possible configurations are showed in the pictures below. Possible configurations are showed in the pictures below.
- Interconnection of SS7 and IP: - Interconnection of SS7 and IP:
Draft Telephony signalling over SCTP AS January 2003
******** *************** ******** ******** *************** ********
* SEP * IP * * IP * * * SEP * IP * * IP * *
* or *---------* SG *--------* ASP * * or *---------* SG *--------* ASP *
* STP * * * * * * STP * * * * *
******** *************** ******** ******** *************** ********
+------ +------+ +------ +------+
| SUAP | | SUAP | | SUAP | | SUAP |
+------+ +------+------+ +------+ +------+ +------+------+ +------+
| SCCP | | SCCP | SUA | | SUA | | SCCP | | SCCP | SUA | | SUA |
skipping to change at page 20, line 5 skipping to change at page 20, line 5
| SCTP | | SCTP | | SCTP | | SCTP |
+------+ +------+ +------+ +------+
| IP | | IP | | IP | | IP |
+------+ +------+ +------+ +------+
IANA has registered SCTP Port Number 14001 for SUA. It is IANA has registered SCTP Port Number 14001 for SUA. It is
recommended that SGs use this SCTP port number for listening for new recommended that SGs use this SCTP port number for listening for new
connections. The payload protocol identifier for the SCTP DATA chunks connections. The payload protocol identifier for the SCTP DATA chunks
is "4". is "4".
Draft Telephony signalling over SCTP AS January 2003 Draft Telephony Signalling over SCTP AS March 2003
5 Security considerations 5 Security considerations
UALs are designated to carry signalling messages for telephony UALs are designated to carry signalling messages for telephony
services. As such, UALs must involve the security needs of several services. As such, UALs must involve the security needs of several
parties: the end users of the services; the network providers and parties: the end users of the services; the network providers and
the applications involved. Additional requirements may come from the applications involved. Additional requirements may come from
local regulation. While having some overlapping security needs, any local regulation. While having some overlapping security needs, any
security solution should fulfill all of the different parties' security solution should fulfill all of the different parties'
needs. See specific Security considerations in each UAL technical needs. See specific Security considerations in each UAL technical
skipping to change at page 20, line 47 skipping to change at page 21, line 5
[RFC2960] Stewart, R. R., Xie, Q., Morneault, K., Sharp, C. , , [RFC2960] Stewart, R. R., Xie, Q., Morneault, K., Sharp, C. , ,
Schwarzbauer, H. J., Taylor, T., Rytina, I., Kalla, M., Zhang, Schwarzbauer, H. J., Taylor, T., Rytina, I., Kalla, M., Zhang,
L. and Paxson, V, "Stream Control Transmission Protocol", RFC2960, L. and Paxson, V, "Stream Control Transmission Protocol", RFC2960,
October 2000. October 2000.
[RF3257] Coene, L., Tuexen, M., Verwimp, G., Loughney, J., Stewart, [RF3257] Coene, L., Tuexen, M., Verwimp, G., Loughney, J., Stewart,
R. R., Xie, Q., Holdrege, M., Belinchon, M.C., and Jungmayer, A., R. R., Xie, Q., Holdrege, M., Belinchon, M.C., and Jungmayer, A.,
"Stream Control Transmission Protocol Applicability statement", "Stream Control Transmission Protocol Applicability statement",
RFC3257, April 2002. RFC3257, April 2002.
Draft Telephony Signalling over SCTP AS March 2003
[RFC2719] Ong, L., Rytina, I., Garcia, M., Schwarzbauer, H., Coene, [RFC2719] Ong, L., Rytina, I., Garcia, M., Schwarzbauer, H., Coene,
L., Lin, H., Juhasz, I., Holdrege, M., Sharp, C., "Framework L., Lin, H., Juhasz, I., Holdrege, M., Sharp, C., "Framework
Architecture for Signalling Transport", RFC2719, October 1999. Architecture for Signalling Transport", RFC2719, October 1999.
Draft Telephony signalling over SCTP AS January 2003
[RFC3057] Morneault, K., Rengasami, S., Kalla, M., Sidebottom, G., [RFC3057] Morneault, K., Rengasami, S., Kalla, M., Sidebottom, G.,
"ISDN Q.921-User Adaptation Layer", RFC3057, February 2001. "ISDN Q.921-User Adaptation Layer", RFC3057, February 2001.
[RFC3331] Morneault, K., Dantu, R., Sidebottom, G., George, T., [RFC3331] Morneault, K., Dantu, R., Sidebottom, G., George, T.,
Bidulock, B., Heitz , J., "Signaling System 7 (SS7) Message Transfer Bidulock, B., Heitz , J., "Signaling System 7 (SS7) Message Transfer
Part (MTP) 2 - User Adaptation Layer", RFC3331, September 2002. Part (MTP) 2 - User Adaptation Layer", RFC3331, September 2002.
[RFC3332] Sidebottom, G., Pastor-Balbas, J., Rytina, I., Mousseau, [RFC3332] Sidebottom, G., Pastor-Balbas, J., Rytina, I., Mousseau,
G., Ong, L., Schwarzbauer, H.J., Gradischnig, K., Morneault, K., G., Ong, L., Schwarzbauer, H.J., Gradischnig, K., Morneault, K.,
Kalla, M., Glaude, N., Bidulock, B., Loughney, J., "SS7 MTP3-User Kalla, M., Glaude, N., Bidulock, B., Loughney, J., "SS7 MTP3-User
skipping to change at page 21, line 45 skipping to change at page 22, line 4
[ALLMAN99] Allman, M. and Paxson, V., "On Estimating End-to-End [ALLMAN99] Allman, M. and Paxson, V., "On Estimating End-to-End
Network Path Properties", Proc. SIGCOMM'99, 1999. Network Path Properties", Proc. SIGCOMM'99, 1999.
[RFCSIGSEC] Loughney, J., Tuexen, M. and Pastor-Balbas, J.,"Security [RFCSIGSEC] Loughney, J., Tuexen, M. and Pastor-Balbas, J.,"Security
Considerations for SIGTRAN Protocols", Considerations for SIGTRAN Protocols",
draft-ietf-sigtran-security-00.txt, work in progress draft-ietf-sigtran-security-00.txt, work in progress
7 Acknowledgments 7 Acknowledgments
This document was initially developed by a design team consisting of This document was initially developed by a design team consisting of
Draft Telephony Signalling over SCTP AS March 2003
Lode Coene, John Loughney, Michel Tuexen, Randall R. Stewart, Lode Coene, John Loughney, Michel Tuexen, Randall R. Stewart,
Qiaobing Xie, Matt Holdrege, Maria-Carmen Belinchon, Andreas Qiaobing Xie, Matt Holdrege, Maria-Carmen Belinchon, Andreas
Jungmaier, Gery Verwimp and Lyndon Ong. Jungmaier, Gery Verwimp and Lyndon Ong.
Draft Telephony signalling over SCTP AS January 2003
The authors wish to thank Renee Revis, H.J. Schwarzbauer, T. Taylor, The authors wish to thank Renee Revis, H.J. Schwarzbauer, T. Taylor,
G. Sidebottom, K. Morneault, T. George, M. Stillman and many others G. Sidebottom, K. Morneault, T. George, M. Stillman, B. Bidulock
for their invaluable comments. and many others for their invaluable comments.
8 Author's Address 8 Author's Address
Lode Coene Phone: +32-14-252081 Lode Coene Phone: +32-14-252081
Siemens Atea EMail: lode.coene@siemens.com Siemens Atea EMail: lode.coene@siemens.com
Atealaan 34 Atealaan 34
B-2200 Herentals B-2200 Herentals
Belgium Belgium
Javier Pastor-Balbas Phone: +34-91-3393819 Javier Pastor-Balbas Phone: +34-91-3393819
skipping to change at page 22, line 46 skipping to change at page 23, line 5
way, such as by removing the copyright notice or references to the way, such as by removing the copyright notice or references to the
Internet Society or other Internet organizations, except as needed Internet Society or other Internet organizations, except as needed
for the purpose of developing Internet standards in which case the for the purpose of developing Internet standards in which case the
procedures for copyrights defined in the Internet Standards procedures for copyrights defined in the Internet Standards
process must be followed, or as required to translate it into process must be followed, or as required to translate it into
languages other than English. languages other than English.
The limited permissions granted above are perpetual and will not The limited permissions granted above are perpetual and will not
be revoked by the Internet Society or its successors or assigns. be revoked by the Internet Society or its successors or assigns.
Draft Telephony Signalling over SCTP AS March 2003
This document and the information contained herein is provided on This document and the information contained herein is provided on
an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
Draft Telephony signalling over SCTP AS January 2003
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
- -
 End of changes. 

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