draft-ietf-sigtran-m2pa-02.txt   draft-ietf-sigtran-m2pa-03.txt 
Network Working Group Tom George Network Working Group Tom George
INTERNET-DRAFT Alcatel INTERNET-DRAFT Alcatel
Ram Dantu Ram Dantu
Cisco Systems Cisco Systems
Malleswar Kalla Malleswar Kalla
Telcordia Telcordia
Hanns Juergen Schwarzbauer Hanns Juergen Schwarzbauer
Siemens Siemens
Greg Sidebottom Greg Sidebottom
Nortel Networks
Ken Morneault Ken Morneault
Cisco Systems Cisco Systems
Expires September 2001 March 2, 2001 Expires January 2002 July 20, 2001
SS7 MTP2-User Peer-to-Peer Adaptation Layer SS7 MTP2-User Peer-to-Peer Adaptation Layer
<draft-ietf-sigtran-m2pa-02.txt> <draft-ietf-sigtran-m2pa-03.txt>
Status of This Memo Status of This Memo
This document is an Internet-Draft and is in full conformance with all This document is an Internet-Draft and is in full conformance with all
provisions of Section 10 of RFC 2026. Internet-Drafts are working provisions of Section 10 of RFC 2026. 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 months Internet-Drafts are draft documents valid for a maximum of six months
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To learn the current status of any Internet-Draft, please check the To learn the current status of any Internet-Draft, please check the
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ftp.isi.edu (US West Coast). ftp.isi.edu (US West Coast).
Abstract Abstract
This Internet Draft defines a protocol supporting the transport of SS7 This Internet Draft defines a protocol supporting the transport of
MTP Layer 3 signaling messages over IP using the services of the Signaling System Number 7 (SS7) Message Transfer Part (MTP) Layer 3
Stream Control Transmission Protocol (SCTP). This protocol would be signaling messages over Internet Protocol (IP) using the services of
used between SS7 Signaling Points employing the MTP Level 3 the Stream Control Transmission Protocol (SCTP). This protocol would
be used between SS7 Signaling Points employing the MTP Level 3
protocol. The SS7 Signaling Points may also employ standard SS7 links protocol. The SS7 Signaling Points may also employ standard SS7 links
using the SS7 Message Transfer Part (MTP) Layer 2 to provide transport using the SS7 MTP Layer 2 to provide transport of MTP Layer 3
of MTP Layer 3 signaling messages. signaling messages.
TABLE OF CONTENTS TABLE OF CONTENTS
1. Introduction............................................. 4 1. Introduction............................................. 4
1.1 Scope................................................. 4 1.1 Scope................................................. 4
1.2 Terminology........................................... 4 1.2 Terminology........................................... 4
1.3 Abbreviations......................................... 5 1.3 Abbreviations......................................... 5
1.4 Conventions........................................... 6 1.4 Conventions........................................... 6
1.5 Signaling Transport Architecture...................... 6 1.5 Signaling Transport Architecture...................... 6
1.6 Services Provided by M2PA............................. 7 1.6 Services Provided by M2PA............................. 8
1.7 Functions Provided by M2PA............................ 8 1.7 Functions Provided by M2PA............................ 9
1.8 Definition of the M2PA Boundaries..................... 9 1.8 Definition of the M2PA Boundaries.....................10
1.9 Differences Between M2PA and M2UA.....................11 1.9 Differences Between M2PA and M2UA.....................12
2. Protocol Elements........................................13 2. Protocol Elements........................................14
2.1 Common Message Header.................................13 2.1 Common Message Header.................................14
2.2 M2PA Messages.........................................14 2.2 M2PA Messages.........................................16
3. M2PA Link States.........................................16 3. M2PA Link State Control..................................19
4. Procedures...............................................19 4. Procedures...............................................22
4.1 Procedures to Support MTP2 Features...................19 4.1 Procedures to Support MTP2 Features...................22
4.2 Procedures to Support the MTP3/MTP2 Interface.........26 4.2 Procedures to Support the MTP3/MTP2 Interface.........31
5. Examples of M2PA Procedures..............................31 5. Examples of M2PA Procedures..............................36
5.1 Link Initialization (Alignment).......................31 5.1 Link Initialization (Alignment).......................36
5.2 Message Transmission and Reception....................33 5.2 Message Transmission and Reception....................39
5.3 Link Status Indication................................33 5.3 Link Status Indication................................39
5.4 Link Status Message (Processor Outage)................34 5.4 Link Status Message (Processor Outage)................40
5.5 Level 2 Flow Control..................................35 5.5 Level 2 Flow Control..................................41
5.6 MTP3 Signaling Link Congestion........................37 5.6 MTP3 Signaling Link Congestion........................43
5.7 Link Deactivation.....................................38 5.7 Link Deactivation.....................................44
5.8 Link Changeover.......................................39 5.8 Link Changeover.......................................45
6. Security.................................................41 6. Security.................................................47
7. IANA Considerations......................................42 6.1 Threats...............................................47
8. Acknowledgements.........................................42 6.2 Protecting Confidentiality............................47
9. References...............................................43 7. IANA Considerations......................................48
10. Author's Addresses.......................................44 7.1 SCTP Payload Protocol Identifier......................48
7.2 M2PA Protocol Extensions..............................48
8. Acknowledgements.........................................49
9. References...............................................50
10. Authors' Addresses.......................................51
1. Introduction 1. Introduction
1.1 Scope 1.1 Scope
There is a need for Switched Circuit Network (SCN) signaling protocol There is a need for Switched Circuit Network (SCN) signaling protocol
delivery over an IP network. This includes delivery from a Signalling delivery over an IP network. This includes message transfer between
Gateway (SG) to a Media Gateway Controller (MGC) or IP Signaling the following:
Point, as described in the Framework Architecture for Signalling
Transport [1]. This could allow for convergence of some signaling and - a Signaling Gateway (SG) and a Media Gateway Controller (MGC)
data networks. SCN signaling nodes would have access to databases and [1]
other devices in the IP network domain that do not employ SS7
signaling links. Likewise, IP telephony applications would have access - a SG and an IP Signaling Point (IPSP)
to SS7 services. There may also be operational cost and performance
- an IPSP and an IPSP
This could allow for convergence of some signaling and data
networks. SCN signaling nodes would have access to databases and other
devices in the IP network domain that do not employ SS7 signaling
links. Likewise, IP telephony applications would have access to SS7
services. There may also be operational cost and performance
advantages when traditional signaling links are replaced by IP network advantages when traditional signaling links are replaced by IP network
"connections". "connections".
The delivery mechanism described in this document allows for full MTP3 The delivery mechanism described in this document allows for full MTP3
message handling and network management capabilities between any two message handling and network management capabilities between any two
SS7 nodes, communicating over an IP network. An SS7 node equipped with SS7 nodes, communicating over an IP network. An SS7 node equipped with
an IP network connection is called an IP Signaling Point (IPSP). The an IP network connection is called an IP Signaling Point (IPSP). The
IPSPs function as traditional SS7 nodes using the IP network instead IPSPs function as traditional SS7 nodes using the IP network instead
of SS7 links. of SS7 links.
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- Support the MTP Level 2 / MTP Level 3 interface boundary. - Support the MTP Level 2 / MTP Level 3 interface boundary.
- Support management of SCTP transport associations and traffic - Support management of SCTP transport associations and traffic
instead of MTP2 Links. instead of MTP2 Links.
- Support asynchronous reporting of status changes to management. - Support asynchronous reporting of status changes to management.
1.2 Terminology 1.2 Terminology
MTP - The Message Transfer Part of the SS7 protocol [2]. MTP - The Message Transfer Part of the SS7 protocol [2] [3].
MTP2 - MTP Level 2, the MTP signaling link layer. MTP2 - MTP Level 2, the MTP signaling link layer.
MTP3 - MTP Level 3, the MTP signaling network layer. MTP3 - MTP Level 3, the MTP signaling network layer.
MTP2-User - A protocol that normally uses the services of MTP Level MTP2-User - A protocol that normally uses the services of MTP Level
2. The only MTP2 user is MTP3. 2. The only MTP2 user is MTP3. The MTP2 user is equivalent to the M2PA
user.
Signaling End Point (SEP) - A node in an SS7 network that originates Signaling End Point (SEP) - A node in an SS7 network that originates
or terminates signaling messages. One example is a central office or terminates signaling messages. One example is a central office
switch. switch.
IP Signaling Point (IPSP) - An SS7 Signaling Point with an IP IP Signaling Point (IPSP) - An SS7 Signaling Point with an IP
network connection used for SS7 over IP. network connection used for SS7 over IP.
Signaling Gateway (SG) - A signaling agent that receives/sends SCN Signaling Gateway (SG) - A signaling agent that receives/sends SCN
native signaling at the edge of the IP network [4]. In this context, native signaling at the edge of the IP network [4]. In this context,
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Signaling Transfer Point (STP) - A node in an SS7 network that routes Signaling Transfer Point (STP) - A node in an SS7 network that routes
signaling messages based on their destination point code in the SS7 signaling messages based on their destination point code in the SS7
network. network.
Association - An association refers to a SCTP association [5]. The Association - An association refers to a SCTP association [5]. The
association provides the transport for MTP3 protocol data units and association provides the transport for MTP3 protocol data units and
M2PA adaptation layer peer messages. M2PA adaptation layer peer messages.
Network Byte Order - Most significant byte first, also known as "Big Network Byte Order - Most significant byte first, also known as "Big
Endian". Endian". See [15], Appendix B Data Transmission Order.
Stream - A stream refers to a SCTP stream [5]. Stream - A stream refers to a SCTP stream [5].
1.3 Abbreviations 1.3 Abbreviations
BSNT - Backward Sequence Number to be Transmitted BSNT - Backward Sequence Number to be Transmitted
FSNC - Forward Sequence Number of last message accepted by FSNC - Forward Sequence Number of last message accepted by
remote level 2 remote level 2
LI - Length Indicator
MSU - Message Signal Unit MSU - Message Signal Unit
SCCP - Signaling Connection Control Part
SCN - Switched Circuit Network SCN - Switched Circuit Network
SCTP - Stream Control Transmission Protocol SCTP - Stream Control Transmission Protocol
SIF - Signaling Information Field SIF - Signaling Information Field
SIO - Service Information Octet SIO - Service Information Octet
SLC - Signaling Link Code SLC - Signaling Link Code
SS7 - Signaling System 7 SS7 - Signaling System Number 7
SSN - Stream Sequence Number SSN - Stream Sequence Number
STP - Signal Transfer Point
1.4 Conventions 1.4 Conventions
The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD, The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD,
SHOULD NOT, RECOMMENDED, NOT RECOMMENDED, MAY, and OPTIONAL, when they SHOULD NOT, RECOMMENDED, NOT RECOMMENDED, MAY, and OPTIONAL, when they
appear in this document, are to be interpreted as described in appear in this document, are to be interpreted as described in
[8]. [8].
1.5 Signaling Transport Architecture 1.5 Signaling Transport Architecture
The architecture that has been defined [4] for Switched Circuit The architecture that has been defined [4] for Switched Circuit
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protocol layer. protocol layer.
Within this framework architecture, this document defines an SCN Within this framework architecture, this document defines an SCN
adaptation module that is suitable for the transport of SS7 MTP3 adaptation module that is suitable for the transport of SS7 MTP3
messages. messages.
Figure 1 shows the seamless interworking at the MTP3 layer. MTP3 is Figure 1 shows the seamless interworking at the MTP3 layer. MTP3 is
adapted to the SCTP layer using the MTP2 User Peer-to-peer Adaptation adapted to the SCTP layer using the MTP2 User Peer-to-peer Adaptation
Layer (M2PA). All the primitives between MTP3 and MTP2 are supported Layer (M2PA). All the primitives between MTP3 and MTP2 are supported
by M2PA. The SCTP association acts as one SS7 link between the IPSPs. by M2PA. The SCTP association acts as one SS7 link between the IPSPs.
An IPSP may have the Signaling Connection Control Part (SCCP) and
other SS7 layers above MTP3.
******** IP ******** ******** IP ********
* IPSP *--------* IPSP * * IPSP *--------* IPSP *
******** ******** ******** ********
+------+ +------+ +------+ +------+
| TCAP | | TCAP |
+------+ +------+
| SCCP | | SCCP |
+------+ +------+
| MTP3 | | MTP3 | | MTP3 | | MTP3 |
+------+ +------+ +------+ +------+
| M2PA | | M2PA | | M2PA | | M2PA |
+------+ +------+ +------+ +------+
| SCTP | | SCTP | | SCTP | | SCTP |
+------+ +------+ +------+ +------+
| IP | | IP | | IP | | IP |
+------+ +------+ +------+ +------+
IP - Internet Protocol IP - Internet Protocol
IPSP - IP Signaling Point IPSP - IP Signaling Point
SCTP - Stream Control Transmission Protocol SCTP - Stream Control Transmission Protocol
(see Reference [5]) (see Reference [5])
Figure 1: M2PA Symmetrical Peer-to-Peer Architecture Figure 1: M2PA Symmetrical Peer-to-Peer Architecture
An IPSP may have SCCP and other SS7 layers above MTP3. Figure 2 shows Figure 2 shows an example of M2PA used in a Signaling Gateway
an example. The Signaling Gateway is an IPSP equipped with both (SG). The SG is an IPSP equipped with both traditional SS7 and IP
traditional SS7 and IP network connections. In effect, the Signaling network connections. In effect, the Signaling Gateway acts as a
Gateway acts as an STP. Any of the nodes in the diagram could have Signal Transfer Point (STP). Any of the nodes in the diagram could
SCCP or other SS7 layers. STPs may or may not be present in the SS7 have SCCP or other SS7 layers. STPs may or may not be present in the
path between the SEP and the SG. SS7 path between the SEP and the SG.
******** SS7 *************** IP ******** ******** SS7 *************** IP ********
* SEP *--------* SG *--------* IPSP * * SEP *--------* SG *--------* IPSP *
******** *************** ******** ******** *************** ********
+------+ +------+ +------+ +------+
| TCAP | | TCAP | | TCAP | | TCAP |
+------+ +------+ +------+ +------+
| SCCP | | SCCP | | SCCP | | SCCP |
+------+ +-------------+ +------+ +------+ +-------------+ +------+
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layers MTP3/M2PA/SCTP/IP to route SS7 messages in a network with all layers MTP3/M2PA/SCTP/IP to route SS7 messages in a network with all
IP links. IP links.
Another example, related to Figure 2, is that two SGs could be Another example, related to Figure 2, is that two SGs could be
connected over an IP network to form an SG mated pair similar to the connected over an IP network to form an SG mated pair similar to the
way STPs are provisioned in traditional SS7 networks. way STPs are provisioned in traditional SS7 networks.
1.5.1 Point Code Representation 1.5.1 Point Code Representation
The MTP specification requires that each node with an MTP3 layer is The MTP specification requires that each node with an MTP3 layer is
represented by an SS7 point code. In particular, each IPSP must have identified by an SS7 point code. In particular, each IPSP must have
its own SS7 point code. its own SS7 point code.
1.6 Services Provided by M2PA 1.6 Services Provided by M2PA
The SS7 MTP3/MTP2 (MTP2-User) interface is retained in the IPSP. The The SS7 MTP3/MTP2 (MTP2-User) interface is retained in the IPSP. The
M2PA protocol layer is required to provide the equivalent set of M2PA protocol layer is required to provide the equivalent set of
services to its user as provided by MTP Level 2 to MTP Level 3. services to its user as provided by MTP Level 2 to MTP Level 3.
These services are described in the following subsections. These services are described in the following subsections.
1.6.1 Support for MTP Level 2 / MTP Level 3 interface boundary 1.6.1 Support for MTP Level 2 / MTP Level 3 interface boundary
This interface is the same as the MTP2/MTP3 interface described in [2] This interface is the same as the MTP2/MTP3 interface described in
and [10], with the addition of support for larger sequence numbers in [2], [3] and [10], with the addition of support for larger sequence
[7]. numbers in [3] and [7].
Because SCTP uses larger sequence numbers than MTP, the MTP3 Because SCTP uses larger sequence numbers than MTP, the MTP3
Changeover procedure must use the Extended Changeover Order and Changeover procedure must use the Extended Changeover Order and
Extended Changeover Acknowledgment messages described in [7]. This Extended Changeover Acknowledgment messages described in [7] and
will allow for use of the SCTP stream sequence numbers in the [3]. This will allow for use of the SCTP stream sequence numbers in
changeover messages. the changeover messages.
Also, the following MTP3/MTP2 primitives must use the larger sequence Also, the following MTP3/MTP2 primitives must use the larger sequence
numbers: numbers:
- BSNT Indication - BSNT Confirmation
- Retrieval Request and FSNC - Retrieval Request and FSNC
1.6.2 Support for peer-to-peer communication 1.6.2 Support for peer-to-peer communication
In SS7, MTP Level 2 sends three types of messages, known as signal In SS7, MTP Level 2 sends three types of messages, known as signal
units: Message Signal Units (MSUs), Link Status Signal Units (LSSUs), units: Message Signal Units (MSUs), Link Status Signal Units (LSSUs),
and Fill-In Signal Units (FISUs). and Fill-In Signal Units (FISUs).
MSUs originate at a higher level than MTP2, and are destined for a MSUs originate at a higher level than MTP2, and are destined for a
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to SCTP as data for transport across a link. These are called User to SCTP as data for transport across a link. These are called User
Data messages in M2PA. Data messages in M2PA.
LSSUs allow peer MTP2 layers to exchange status information. Analogous LSSUs allow peer MTP2 layers to exchange status information. Analogous
messages are needed for M2PA. The Link Status message serves this messages are needed for M2PA. The Link Status message serves this
purpose. purpose.
FISUs are sent when no other signal units are waiting to be sent. This FISUs are sent when no other signal units are waiting to be sent. This
purpose is served by the heartbeat messages in SCTP. FISUs also carry purpose is served by the heartbeat messages in SCTP. FISUs also carry
acknowledgment of messages. This function is performed by acknowledgment of messages. This function is performed by
SCTP. Therefore, it is unnecessary for M2PA to provide a protocol unit SCTP. Therefore, it is unnecessary for M2PA to provide a protocol data
like the FISU. unit like the FISU.
1.7 Functions Provided by M2PA 1.7 Functions Provided by M2PA
1.7.1 Support of MTP3/MTP2 Primitives 1.7.1 Support of MTP3/MTP2 Primitives
M2PA receives the primitives sent from MTP3 to its lower layer. M2PA M2PA receives the primitives sent from MTP3 to its lower layer. M2PA
processes these primitives or maps them to appropriate primitives at processes these primitives or maps them to appropriate primitives at
the M2PA/SCTP interface. Likewise, M2PA sends primitives to MTP3 like the M2PA/SCTP interface. Likewise, M2PA sends primitives to MTP3 like
those used in the MTP3/MTP2 interface. those used in the MTP3/MTP2 interface.
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- Data retrieval to support the MTP3 changeover procedure - Data retrieval to support the MTP3 changeover procedure
- Reporting of link status changes to MTP3 - Reporting of link status changes to MTP3
- Processor outage procedure - Processor outage procedure
- Link alignment procedure - Link alignment procedure
1.7.3 Mapping of SS7 and IP Entities 1.7.3 Mapping of SS7 and IP Entities
For each IP link, the M2PA layer must maintain a map of the SS7 link The M2PA layer must maintain a map of each of its SS7 links to the
to its SCTP association and its corresponding IP destination. corresponding SCTP association.
1.7.4 SCTP Stream Management 1.7.4 SCTP Stream Management
SCTP allows a user-specified number of streams to be opened during the SCTP allows a user-specified number of streams to be opened during the
initialization. It is the responsibility of the M2PA layer to ensure initialization. It is the responsibility of the M2PA layer to ensure
proper management of the streams allowed within each association. proper management of the streams allowed within each association.
M2PA uses two streams in each direction in each association. Stream 0 M2PA uses two streams in each direction for each association. Stream 0
in each direction is designated for Link Status messages. Stream 1 is in each direction is designated for Link Status messages. Stream 1 is
designated for User Data messages. Separating the Link Status and User designated for User Data and Proving Data messages. Separating the
Data messages onto separate stream allows M2PA to prioritize the Link Status and User Data messages onto separate stream allows M2PA to
messages in a manner similar to MTP2. prioritize the messages in a manner similar to MTP2.
1.7.5 Retention of MTP3 in the SS7 Network 1.7.5 Retention of MTP3 in the SS7 Network
M2PA allows MTP3 to perform all of its Message Handling and Network M2PA allows MTP3 to perform all of its Message Handling and Network
Management functions with IPSPs as with other SS7 nodes. Management functions with IPSPs as with other SS7 nodes.
1.8 Definition of the M2PA Boundaries 1.8 Definition of the M2PA Boundaries
1.8.1 Definition of the M2PA / MTP Level 3 boundary 1.8.1 Definition of the M2PA / MTP Level 3 boundary
The upper layer primitives provided by M2PA are the same as those The upper layer primitives provided by M2PA are the same as those
provided by MTP2 to MTP3. These primitives are described in [2] and provided by MTP2 to MTP3. These primitives are described in [2], [3],
[10]. Following is a list of the primitives. and [10]. Following is a list of the primitives.
Primitives sent from MTP3 to M2PA: Primitives sent from MTP3 to M2PA:
Data Request - Used to send a Data Message for transmission. Data Request - Used to send a Data Message for transmission.
Start Request - Used to establish a link. Start Request - Used to activate a link.
Stop Request - Used to release a link. Stop Request - Used to deactivate a link.
Retrieve BSNT Request - Request the BSNT for the changeover procedure. Retrieve BSNT Request - Request the BSNT for the changeover procedure.
Retrieval Request and FSNC - Request retrieval of unacknowledged and Retrieval Request and FSNC - Request retrieval of unacknowledged and
unsent messages. This request includes the FSNC received from the unsent messages. This request includes the FSNC received from the
remote end. remote end.
Local Processor Outage Request - Informs M2PA of a local processor
outage condition.
Local Processor Outage Recovered Request - Informs M2PA that a local
processor outage condition has ceased.
Flush Buffers Request - Requests that all transmit and receive Flush Buffers Request - Requests that all transmit and receive
buffers be emptied. buffers be emptied.
Continue Request - Requests that processing resume after a processor Continue Request - Requests that processing resume after a processor
outage. outage.
Emergency Request - This is ignored by M2PA. Emergency Request - Requests that M2PA use the emergency alignment
procedure.
Emergency Ceases Request - This is ignored by M2PA. Emergency Ceases Request - Requests that M2PA use the normal alignment
procedure.
Primitives sent from M2PA to MTP3: Primitives sent from M2PA to MTP3:
Data Indication - Used to deliver received Data Message to MTP3. Data Indication - Used to deliver received Data Message to MTP3.
Congestion Indication - Indicates change in congestion level. The Congestion Indication - Indicates change in congestion status. The
indication includes the congestion level, if the protocol is using the indication includes the congestion status, if the protocol is using the
optional congestion levels. The indication also includes the discard optional congestion levels. The indication also includes the discard
level. status.
In Service Indication - Indicates that the link is in service. In Service Indication - Indicates that the link is in service.
Out of Service Indication - Indicates that the link is out of service. Out of Service Indication - Indicates that the link is out of service.
Retrieved Messages Indication - Indicates delivery of unacknowledged Retrieved Messages Indication - Indicates delivery of unacknowledged
and unsent messages. and unsent messages.
Retrieval Complete Indication - Indicates that delivery of Retrieval Complete Indication - Indicates that delivery of
unacknowledged and unsent messages is complete. unacknowledged and unsent messages is complete.
skipping to change at page 11, line 18 skipping to change at page 12, line 18
[5] Section 10 "Interface with Upper Layer". [5] Section 10 "Interface with Upper Layer".
1.9 Differences Between M2PA and M2UA 1.9 Differences Between M2PA and M2UA
The MTP2 User Adaptation Layer (M2UA) [6] also adapts the MTP3 layer The MTP2 User Adaptation Layer (M2UA) [6] also adapts the MTP3 layer
to the SCTP/IP stack. It does so through a backhauling architecture to the SCTP/IP stack. It does so through a backhauling architecture
[4]. This section intends to clarify some of the differences between [4]. This section intends to clarify some of the differences between
the M2PA and M2UA approaches. the M2PA and M2UA approaches.
A possible M2PA architecture is shown in Figure 3. Here the IPSP's A possible M2PA architecture is shown in Figure 3. Here the IPSP's
MTP3 uses its underlying M2PA as a replacement for MTP3 uses its underlying M2PA as a replacement for MTP2. Communication
MTP2. Commmunication between the two layers MTP3/M2PA is defined by between the two layers MTP3/M2PA is defined by the same primitives as
the same primitives as in SS7 MTP3/MTP2. M2PA performs functions in SS7 MTP3/MTP2. M2PA performs functions similar to MTP2.
similar to MTP2.
A comparable architecture for M2UA is shown in Figure 4. In M2UA, the A comparable architecture for M2UA is shown in Figure 4. In M2UA, the
MGC's MTP3 uses the SG's MTP2 as its lower SS7 layer. In SS7, MGC's MTP3 uses the SG's MTP2 as its lower SS7 layer. Likewise, the
commmunication between the MTP3 and MTP2 layers is defined by SG's MTP2 uses the MGC's MTP3 as its upper SS7 layer. In SS7,
communication between the MTP3 and MTP2 layers is defined by
primitives. In M2UA, the MTP3/MTP2 communication is defined as M2UA primitives. In M2UA, the MTP3/MTP2 communication is defined as M2UA
messages and sent over the IP connection. messages and sent over the IP connection.
******** SS7 *************** IP ******** ******** SS7 *************** IP ********
* SEP *--------* SG *--------* IPSP * * SEP *--------* SG *--------* IPSP *
******** *************** ******** ******** *************** ********
+------+ +-------------+ +------+ +------+ +-------------+ +------+
| SCCP | | SCCP | | SCCP | | SCCP | | SCCP | | SCCP |
+------+ +-------------+ +------+ +------+ +-------------+ +------+
skipping to change at page 13, line 13 skipping to change at page 14, line 13
Figure 4: M2UA in IP Signaling Gateway Figure 4: M2UA in IP Signaling Gateway
M2PA and M2UA are similar in that: M2PA and M2UA are similar in that:
a. Both transport MTP3 data messages. a. Both transport MTP3 data messages.
b. Both present an MTP2 upper interface to MTP3. b. Both present an MTP2 upper interface to MTP3.
Differences between M2PA and M2UA include: Differences between M2PA and M2UA include:
a. M2PA: IPSP processes MTP3-to-MTP2 primitives. a. M2PA: IPSP processes MTP3/MTP2 primitives.
M2UA: MGC transports MTP3-to-MTP2 primitives to SG's MTP2 M2UA: MGC transports MTP3/MTP2 primitives between the SG's MTP2
(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. M2UA: SG-MGC connection is not an SS7 link. It is an
extension of MTP to a remote entity.
c. M2PA: SG is an SS7 node with a point code. c. M2PA: SG is an SS7 node with a point code.
M2UA: SG is not an SS7 node and has no point code. M2UA: SG is not an SS7 node and has no point code.
d. M2PA: SG can have upper SS7 layers, e.g., SCCP. d. M2PA: SG can have upper SS7 layers, e.g., SCCP.
M2UA: SG does not have upper SS7 layers since it has no MTP3. M2UA: SG does not have upper SS7 layers since it has no MTP3.
e. M2PA: relies on MTP3 for management procedures.
M2UA: uses M2UA management procedures.
Potential users of M2PA and M2UA should be aware of these differences Potential users of M2PA and M2UA should be aware of these differences
when deciding how to use them for SS7 signaling transport over IP when deciding how to use them for SS7 signaling transport over IP
networks. networks.
2. Protocol Elements 2. Protocol Elements
This section describes the format of various messages used in this This section describes the format of various messages used in this
protocol. protocol.
All fields in an M2PA message must be transmitted in the network byte All fields in an M2PA message must be transmitted in the network byte
order, i.e., most significant byte first, unless otherwise stated. order, i.e., most significant byte first, unless otherwise stated.
2.1 Common Message Header 2.1 Common Message Header
The protocol messages for M2PA require a message header structure The protocol messages for M2PA require a message header structure
which contains a version, message type and message length. This which contains a version, message type and message length. The header
message header is common among all SCN adaptation layers. The structure is shown in Figure 5.
header structure is shown in Figure 5.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Version | Spare | Message Type | | Version | Spare | Message Class | Message Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message Length | | Message Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
Figure 5: Common Message Header Figure 5: Common Message Header
2.1.1 Version 2.1.1 Version
The version field contains the version of the M2PA adapation layer. The version field contains the version of M2PA. The supported versions
The supported versions are: are:
01 Release 1.0 of M2PA protocol Value Version
----- -------
1 Release 1.0 of M2PA protocol
2.1.2 Message Type 2.1.2 Spare
The valid message types are defined below and the message contents are The Spare field SHOULD be set to all zeroes (0's) by the sender and
described in Section 2.2. Each message can contain parameters. ignored by the receiver. The Spare field SHOULD NOT be used for
proprietary information.
The following list contains the message types for the defined messages. 2.1.3 Message Class
MTP2 User Adaptatation Messages The following List contains the valid Message Classes:
Type Value (Hex) Value
(decimal) Message Class
--------- -------------
11 M2PA Messages
User Data 0601 Other values are invalid for M2PA.
Link Status 0602
2.1.3 Message Length 2.1.4 Message Type
The Message length defines the length of the message in octets, not The following list contains the message types for the defined
including the header. messages.
Value Message Type
----- ------------
1 User Data
2 Link Status
3 Proving Data
Other values are invalid.
2.1.4 Message Length
The Message Length defines the length of the message in octets,
including the Common Header.
2.2 M2PA Messages 2.2 M2PA Messages
The following section defines the messages and parameter contents. An The following section defines the messages and parameter contents. An
M2PA message consists of a Common Message Header followed by the data M2PA message consists of a Common Message Header followed by the data
appropriate to the message. appropriate to the message.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
... ...
| Common Message Header | | Common Message Header |
... ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
... ...
| Message Data | | Message Data |
... ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2.2.1 User Data 2.2.1 User Data
The User Data is the data sent from the MTP3 in the form of the The User Data is the data sent from MTP3. The format for the User Data
contiguous LI, SIO, and SIF octets of the MSU ([2] Q.703, section 2.2 message is as follows:
Signal Unit Format). The LI octet includes the two undefined bits
between the SIO and LI fields.
The format for the User Data message is as follows:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
... ...
| Data | | Data |
... ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
No padding is added to the MTP3 message. The Data field contains the following fields of the MTP Message Signal
Unit (MSU):
Note that the Data field contains only the LI, SIF, and SIO - Length Indicator (LI), including the two undefined bits between
octets. The other components of the MTP2 MSU format (the Flag, BSN, the SIO and LI fields.
BIB, FSN, FIB, CK) are not included in M2PA. - Service Information Octet (SIO)
- Signaling Information Field (SIF)
The MTP MSU described in [2] Q.703, section 2.2 Signal Unit Format,
and [3] T1.111.3 section 2.2 Signal Unit Format.
M2PA does not add padding to the MTP3 message.
Note that the Data field SHALL NOT contain other components of the MTP
MSU format:
- Flag
- Backward Sequence Number (BSN)
- Backward Indicator Bit (BIB)
- Forward Sequence Number (FSN)
- Forward Indicator Bit (FIB)
- Check bits (CK)
The Data field SHALL be transmitted in the byte order as defined by
MTP3.
It is not necessary to put the message length in the LI octet as in It is not necessary to put the message length in the LI octet as in
MTP2. The LI octet is included because the two spare bits in the LI MTP2. The LI octet is included because the two spare bits in the LI
octet are used by MTP3 in a national version of SS7 as a Priority octet are used by MTP3 in at least one national version of SS7 to
field. See [9], section 14 "Common Characteristics of message signal carry MTP3 information. For example, the Japan TTC standard uses these
unit formats", section 14.2 (A) Priority Indicator (PRI). Therefore spare bits as an MTP3 Message Priority field. See [9], section 14
the format of the LI octet is: "Common Characteristics of message signal unit formats", section 14.2
(A) Priority Indicator (PRI). For versions of MTP that do not use
these two bits, the entire octet is spare.
Therefore in M2PA the format of the LI octet is:
0 0
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
| spare |PRI| (followed by SIO, SIF) | spare |PRI| (followed by SIO, SIF)
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
PRI - Priority used only in national MTP defined in [9]. PRI - Priority used only in national MTP defined in [9].
Spare for other MTP versions. Spare for other MTP versions.
Since the LI octet is not used for a message length, there is no need Since the LI octet is not used for a message length, there is no need
to support the expanded LI field in [2], Q.703 Annex A. Therefore the to support the expanded LI field in [2], Q.703 Annex A. Therefore the
LI field in M2PA is always one octet. LI field in M2PA is always one octet.
Note: In the SS7 Recommendations, the format of the messages and
fields within the messages are based on bit transmission order. In
these recommendations the Least Significant Bit (LSB) of each field is
positioned to the right. The received SS7 fields are populated octet
by octet as received into the 4-octet word as shown below.
As an example, in the ANSI MTP protocol, the Data field format is
shown below:
|MSB---------------------------------------------------------LSB|
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| spare |PRI| SIO | SIF octet | ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ : \
/ : /
\ : \
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... | ... | ... | SIF octet |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Within each octet the Least Significant Bit (LSB) per the SS7
Recommendations is to the right (e.g., bit 15 of SIO is the LSB).
2.2.2 Link Status 2.2.2 Link Status
The MTP2 Link Status message can be sent between M2PA peers to The MTP2 Link Status message can be sent between M2PA peers to
indicate link status. This message performs a function similar to the indicate link status. This message performs a function similar to the
the Link Status Signal Unit in MTP2. the Link Status Signal Unit in MTP2. Except as modified later in this
section, the format for the Link Status message is as follows:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| State | | State |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The valid values for State are shown in the following table. The valid values for State are shown in the following table.
Value Description Value
(decimal) Description
--------- -----------
1 Alignment
2 Proving Normal
3 Proving Emergency
4 Ready
5 Processor Outage
6 Processor Outage Ended
7 Busy
8 Busy Ended
1 In Service 2.2.3 Proving Data
2 Processor Outage
3 Processor Outage Ended
4 Busy
5 Busy Ended
3. M2PA Link States The Proving Data message is used during the proving period. The format
for the message is as follows.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
...
| Data |
...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
It is recommended that the length of the Data field be similar to the
size of the User Data messages that will be carried on the link.
It is recommended that the Data field contain a number pattern which
varies among the Proving Data messages, and that will allow the SCTP
checksum to be used to verify the accuracy of transmission.
3. M2PA Link State Control
The M2PA link moves from one state to another in response to various The M2PA link moves from one state to another in response to various
events. The events that may result in a change of state include: events. The events that may result in a change of state include:
- MTP3 primitive requests - MTP3 primitive requests
- SCTP notifications - SCTP notifications
- Receipt of Status messages from the peer M2PA - Receipt of Status messages from the peer M2PA
- Expiration of certain timers - Expiration of certain timers
Figure 6 illustrates state changes together with the causing events. Figure 6 illustrates state changes together with the causing events.
Note that some of the error conditions are not shown in the state Note that some of the error conditions are not shown in the state
diagram. diagram.
Following is a list of the M2PA Link States and a description of each. Following is a list of the M2PA Link States and a description of each.
IDLE - State of link during power-up initialization. IDLE - State of the link during power-up initialization.
OOS - Out Of Service. Power-up initialization is complete. OOS - Out Of Service. Power-up initialization is complete.
AIP - Alignment In Progress. M2PA is attempting to establish SCTP AIP - Alignment In Progress. M2PA is attempting to exchange Alignment
association. messages with its peer.
INS-LOCAL - In Service Local. Association is established. M2PA is PROVING - M2PA is sending Proving Data messages to its peer.
waiting for peer to verify that it is In Service.
ALIGNED READY - Proving is complete. M2PA is waiting until peer
completes proving.
INS - In Service. Link is ready for traffic. INS - In Service. Link is ready for traffic.
RETRIEVAL - Link no longer carries traffic. M2PA is waiting for RETRIEVAL - Link no longer carries traffic. M2PA is waiting for
request for message retrieval from MTP3. request for message retrieval from MTP3.
+-----------+ +-----------+
| IDLE | | IDLE |
+-----------+ +-----------+
| |
| Power On | Power On
| |
V | +--------------------------+
+-----------+ | | (Associate) |
+------->| OOS |<---------------------+ V V |
^ +-----------+ | +-----------+ |
| | | | +------>| OOS |<--+ |
| Server AND | | Client AND | | +-----------+ | Link Configured |
| MTP3 Start | | MTP3 Start | | | | | (Associate) |
| | | | | | +-----+ |
| V V | | | |
| | MTP3 Start |
| MTP3 Stop | |
| V |
| +-----------+ | | +-----------+ |
| | AIP |--------------------->+ +<------| AIP |----------------------->+
| +-----------+ MTP3 Stop | | +-----------+ SCTP Comm Error |
| | OR SCTP Comm Error |
| | OR SCTP Comm Lost | | | OR SCTP Comm Lost |
| | OR T1 Expiry |
| | | | | |
| | SCTP Comm Up | | | Receive LS Alignment |
| | OR LS Proving |
| MTP3 Stop | |
| V |
| +-----------+ |
+<------| PROVING |----------------------->+
| +-----------+ SCTP Comm Error |
| | OR SCTP Comm Lost |
| | | | | |
| | T2 Expiry |
| MTP3 Stop | |
| V | | V |
| +-----------+ | | +-----------+ |
| | INS-LOCAL |--------------------->+ +<------| ALIGNED | |
| +-----------+ MTP3 Stop | READY |----------------------->+
| | OR SCTP Comm Error +-----------+ |
| | OR SCTP Comm Lost | SCTP Comm Error |
| | OR T1 Expiry | OR SCTP Comm Lost |
| OR T3 Expiry |
| | | |
| | Link Status | Receive LS Proving Complete |
| | In Service received | OR Receive User Data |
| | | |
| V V |
| +-----------+ +-----------+ |
| | INS | | INS | |
| +-----------+ +-----------+ |
| | | |
Retrieval | | MTP3 Stop
Complete | | OR SCTP Comm Error
OR | | OR SCTP Comm Lost
MTP3 Start | | OR T6 Expiry
| | | |
| V | |
| +-----------+ | |
+<-------| RETRIEVAL | | |
| MTP3 Stop |
| OR SCTP Comm Error |
| OR SCTP Comm Lost |
| OR T6 Expiry |
| |
V |
+-----------+ |
| RETRIEVAL |----------------------->+
+-----------+ Retrieval Complete
OR MTP3 Start
Figure 6: M2PA Link State Transition Diagram
Figure 7 illustrates state changes in the M2PA management of the SCTP
association together with the causing events. Note that some of the
error conditions are not shown in the state diagram.
Following is a list of the M2PA Association States and a description
of each.
IDLE - State of the association during power-up initialization.
ASSOCIATE - M2PA is attempting to establish an SCTP association.
ESTABLISHED - SCTP association is established.
+-----------+ +-----------+
+------------------->| IDLE |
| +-----------+
| |
| (Issue SCTP | Associate
| Abort) | (Issue SCTP associate)
| |
| | +----------------------+
| | | (Issue SCTP |
| V V associate) |
| Abort +-----------+ |
+<-------------------| ASSOCIATE |------------------->+
| +-----------+ SCTP Comm Error |
| | |
| | |
| | SCTP Comm Up |
| | |
| V |
| Abort +-------------+ |
+<-------------------| ESTABLISHED |----------------->+
+-------------+ SCTP Comm Error
OR SCTP Comm Lost
Figure 6: M2PA Link State Transition Diagram. Figure 7: M2PA Association State Transition Diagram
4. Procedures 4. Procedures
4.1 Procedures to Support MTP2 Features 4.1 Procedures to Support MTP2 Features
4.1.1 Signal Unit Format, Delimitation, Acceptance 4.1.1 Signal Unit Format, Delimitation, Acceptance
Messages for transmission across the network must follow the format Messages for transmission across the network must follow the format
described in section 2. described in section 2.
SCTP provides reliable, in-sequence delivery. Therefore the related SCTP provides reliable, in-sequence delivery. Therefore the related
functionality of MTP2 is not needed. SCTP does not provide functions functionality of MTP2 is not needed. SCTP does not provide functions
related to Link State Control in MTP2. These functions must be related to Link State Control in MTP2. These functions must be
provided by M2PA. provided by M2PA.
4.1.2 Link Alignment 4.1.2 MTP and SCTP Entities
Link alignment includes the establishment of an SCTP association and a This section describes how M2PA relates MTP and SCTP entities.
handshaking procedure between the M2PA peers to verify that the
association is ready to be used as a link.
To prevent duplicate associations from being established, it must be To prevent duplicate associations from being established, it must be
decided in advance which endpoint initiates the establishment of the decided in advance which endpoint initiates the establishment of the
association. In a pair of endpoints, the endpoint that initiates the association. In a pair of endpoints, the endpoint that initiates the
establishment of the association is called the client. The other establishment of the association is called the client. The other
endpoint is the server. An endpoint may be a client in its endpoint is the server. An endpoint may be a client in its
relationship with one endpoint, and a server in its relationship with relationship with one endpoint, and a server in its relationship with
another endpoint. The designations of client and server are needed another endpoint. The designations of client and server are needed
only to decide which endpoint initiates the establishment of the only to decide which endpoint initiates the establishment of the
association. After that, the endpoints function as peers. association. After that, the endpoints function as peers.
The client initiates the association using the server's IP address and The client initiates the association using the server's IP address and
the M2PA well-known port number as the destination endpoint. In order the M2PA well-known port number as the destination endpoint. If only
to allow for multiple links between the two endpoints, the client uses one association is to be established between these two IP addresses,
a different local port number for each link. It must be decided in then the client should use its own IP address and the M2PA well-known
advance which local ports are used by the client. Each of these client port number as the source endpoint.
ports must be known to the server.
If it is desirable to create multiple associations (for multiple
links) between the two IP addresses, the client uses a different local
port number for each association.
The client M2PA should establish the association for a link when the
link is configured for operation by MTP signaling management.
Whenever the association is terminated, the client M2PA should
establish the association as soon as the termination procedure is
complete.
The client M2PA establishes an association by sending the SCTP
ASSOCIATE primitive to SCTP. The client should attempt to establish
the association periodically until it is successful.
Once the association is established and MTP3 has issued its Start
Request, M2PA begins the alignment procedure. The M2PA at either end
may initiate the alignment procedure first. There is no client/server
distinction once the SCTP association is established.
Each combination of client IP address/port and server IP address/port Each combination of client IP address/port and server IP address/port
(i.e., each association) must be mapped to the same Signaling Link (i.e., each association) must be mapped to the same Signaling Link
Code (SLC) in the client and server, so that each endpoint knows which Code (SLC) in the client and server, so that each endpoint knows which
link is being created at the time the SCTP association is link is being created at the time the SCTP association is
established. However, M2PA does not do any processing based on the established. However, M2PA does not do any processing based on the
SLC. SLC.
Following are examples of the relationships between associations and Following are examples of the relationships between associations and
links. Note that a link is an SCTP association identified by two links. Note that a link is an SCTP association identified by two
endpoints, in this case a client and server. Each endpoint is endpoints, in this case a client and server. Each endpoint is
identified by an IP address and port number. Each association is identified by an IP address and port number. Each association is
mapped to an SLC. mapped to an SLC.
Figure 7 shows a case with two IPSPs, each with two IP addresses. Two Figure 8 shows a case with two IPSPs, each with two IP addresses. Two
associations are the links that connect the two IPSPs. Since these associations are the links that connect the two IPSPs. Since these
links are in the same link set, they must have different SLCs. links are in the same link set, they must have different SLCs.
Table 1 shows the relationships in tabular form. Table 1 is only Table 1 shows the relationships in tabular form. Table 1 is only
conceptual. The actual method for mapping the SCTP associations to the conceptual. The actual method for mapping the SCTP associations to the
SLCs is implementation dependent. SLCs is implementation dependent.
IPSP X IPSP Y IPSP X IPSP Y
+-------------+ +-------------+ +-------------+ +-------------+
skipping to change at page 20, line 33 skipping to change at page 23, line 46
| IPC | association 2 | IPD | | IPC | association 2 | IPD |
| port = PW +---------------+ port = PW | | port = PW +---------------+ port = PW |
| SLC = b | | SLC = b | | SLC = b | | SLC = b |
| Client | | Server | | Client | | Server |
| | | | | | | |
+-------------+ +-------------+ +-------------+ +-------------+
IPx = IP address IPx = IP address
PW = Well-known port number for M2PA PW = Well-known port number for M2PA
Figure 7: Associations and Links - Figure 8: Associations and Links -
Two IPSPs with Two Endpoints Each Two IPSPs with Two IP Addresses Each
+-------------+---------------------------------------+-----+ +-------------+---------------------------------------+-----+
| Association | Client | Server | SLC | | Association | Client | Server | SLC |
| +------------+------+------------+------+ | | +------------+------+------------+------+ |
| | IP address | Port | IP address | Port | | | | IP address | Port | IP address | Port | |
+=============+============+======+============+======+=====+ +=============+============+======+============+======+=====+
| 1 | IPA | PW | IPB | PW | a | | 1 | IPA | PW | IPB | PW | a |
+-------------+------------+------+------------+------+-----+ +-------------+------------+------+------------+------+-----+
| 2 | IPC | PW | IPD | PW | b | | 2 | IPC | PW | IPD | PW | b |
+-------------+------------+------+------------+------+-----+ +-------------+------------+------+------------+------+-----+
Table 1: Associations and SLCs - Table 1: Associations and SLCs -
Two IPSPs with Two Endpoints Each Two IPSPs with Two IP Addresses Each
Figure 8 and Table 2 show an example with three IPSPs. Note that in Figure 9 and Table 2 show an example with three IPSPs. Note that in
this example, the two links are in different link sets. Therefore, it this example, the two links are in different link sets. Therefore, it
is possible that the values a and b may be equal. is possible that the values a and b may be equal.
IPSP X IPSP Y IPSP X IPSP Y
+-------------+ +-------------+ +-------------+ +-------------+
| | SCTP | | | | SCTP | |
| IPA | association 1 | IPB | | IPA | association 1 | IPB |
| port = PW +---------------+ port = PW | | port = PW +---------------+ port = PW |
| SLC = a | | SLC = a | | SLC = a | | SLC = a |
skipping to change at page 21, line 47 skipping to change at page 25, line 43
| | | |
| | | |
| | | |
| | | |
| | | |
+-------------+ +-------------+
IPx = IP address IPx = IP address
PW = Well-known port number for M2PA PW = Well-known port number for M2PA
Figure 8: Associations and Links - Figure 9: Associations and Links -
One IPSP Connected to Two IPSPs One IPSP Connected to Two IPSPs
+-------------+---------------------------------------+-----+ +-------------+---------------------------------------+-----+
| Association | Client | Server | SLC | | Association | Client | Server | SLC |
| +------------+------+------------+------+ | | +------------+------+------------+------+ |
| | IP address | Port | IP address | Port | | | | IP address | Port | IP address | Port | |
+=============+============+======+============+======+=====+ +=============+============+======+============+======+=====+
| 1 | IPA | PW | IPB | PW | a | | 1 | IPA | PW | IPB | PW | a |
+-------------+------------+------+------------+------+-----+ +-------------+------------+------+------------+------+-----+
| 2 | IPC | PW | IPD | PW | b | | 2 | IPC | PW | IPD | PW | b |
+-------------+------------+------+------------+------+-----+ +-------------+------------+------+------------+------+-----+
skipping to change at page 23, line 5 skipping to change at page 26, line 5
| | IP address | Port | IP address | Port | | | | IP address | Port | IP address | Port | |
+=============+============+======+============+======+=====+ +=============+============+======+============+======+=====+
| 1 | IPA | PW | IPB | PW | a | | 1 | IPA | PW | IPB | PW | a |
+-------------+------------+------+------------+------+-----+ +-------------+------------+------+------------+------+-----+
| 2 | IPC | PW | IPD | PW | b | | 2 | IPC | PW | IPD | PW | b |
+-------------+------------+------+------------+------+-----+ +-------------+------------+------+------------+------+-----+
Table 2: Associations and SLCs - Table 2: Associations and SLCs -
One IPSP Connected to Two IPSPs One IPSP Connected to Two IPSPs
Figure 9 and Table 3 show two associations between the same Figure 10 and Table 3 show two associations between the same
endpoints. This is accomplished by using different port numbers for endpoints. This is accomplished by using different port numbers for
each association at the client. each association at the client.
IPSP X IPSP Y IPSP X IPSP Y
+-------------+ +-------------+ +-------------+ +-------------+
| | SCTP | | | | SCTP | |
| IPA | association 1 | IPB | | IPA | association 1 | IPB |
| port = P1 +---------------+ port = PW | | port = P1 +---------------+ port = PW |
| SLC = a | | SLC = a | | SLC = a | | SLC = a |
skipping to change at page 23, line 27 skipping to change at page 26, line 27
| | | | | | | |
| | SCTP | | | | SCTP | |
| IPA | association 2 | IPB | | IPA | association 2 | IPB |
| port = PW +---------------+ port = PW | | port = PW +---------------+ port = PW |
| SLC = b | | SLC = b | | SLC = b | | SLC = b |
| Client | | Server | | Client | | Server |
| | | | | | | |
+-------------+ +-------------+ +-------------+ +-------------+
IPx = IP address IPx = IP address
P1, P2 = Pre-selected port numbers for Client P1 = Pre-selected port number for Client
PW = Well-known port number for M2PA PW = Well-known port number for M2PA
Figure 9: Associations and SLCs - Figure 10: Associations and SLCs -
Multiple Associations Between Endpoints Multiple Associations Between Two IP Addresses
+-------------+---------------------------------------+-----+ +-------------+---------------------------------------+-----+
| Association | Client | Server | SLC | | Association | Client | Server | SLC |
| +------------+------+------------+------+ | | +------------+------+------------+------+ |
| | IP address | Port | IP address | Port | | | | IP address | Port | IP address | Port | |
+=============+============+======+============+======+=====+ +=============+============+======+============+======+=====+
| 1 | IPA | P1 | IPB | PW | a | | 1 | IPA | P1 | IPB | PW | a |
+-------------+------------+------+------------+------+-----+ +-------------+------------+------+------------+------+-----+
| 2 | IPA | P2 | IPB | PW | b | | 2 | IPA | PW | IPB | PW | b |
+-------------+------------+------+------------+------+-----+ +-------------+------------+------+------------+------+-----+
Table 3: Associations and SLCs - Table 3: Associations and SLCs -
Multiple Associations Between Endpoints Multiple Associations Between Two IP Addresses
The association shall contain two streams in each direction. Stream 0 The association shall contain two streams in each direction. Stream 0
is designated for Link Status messages. Stream 1 is designated for is designated for Link Status messages. Stream 1 is designated for
User Data messages. User Data and Proving Data messages.
If the SCTP association is not established, the client M2PA sends the 4.1.3 Link Alignment
ASSOCIATE primitive to SCTP. The client should attempt to establish
the association periodically until it is successful.
If SCTP fails to establish the association, and M2PA had received a The purposes of the alignment procedure are:
Start Request from its MTP3, then M2PA shall report to MTP3 that the
link is out of service. If M2PA has an SCTP association ID for that
association, it should ABORT the association. The association ID is a
number provided by the SCTP used to identify an association.
Once the association is established, M2PA invokes the GETSRTTREPORT 1. To provide a handshaking procedure so that both endpoints are
primitive to determine the Smooth Round Trip Time (SRTT) from SCTP. If prepared to send SS7 traffic, and to prevent traffic from being
the SRTT exceeds its maximum allowed value (which is implementation sent before the other end is ready.
dependent), M2PA should use the ABORT primitive to end the
association. If M2PA had received a Start Request from its MTP3, then
M2PA shall report to MTP3 that the link is out of service.
Once M2PA has received a Start Request from MTP3, the association is 2. Verify that the SCTP association is suitable for use as an SS7
established, the SRTT is determined to be satisfactory, and if MTP3 link.
has not deactivated the link, then:
(a) If there is no local processor outage condition, M2PA sends a 3. Optionally, to overcome the SCTP slow start period.
Link Status of In Service to its peer.
(b) If there is a local processor outage condition, M2PA sends Link Link alignment takes place after the association is established. If
Status Processor Outage to its peer. When MTP3 sends Local SCTP fails to establish the association, and M2PA has received a Start
Processor Recovered, then M2PA sends Link Status Processor Request from its MTP3, then M2PA shall report to MTP3 that the link is
Outage Ended to its peer, followed by Link Status In Service. out of service.
If M2PA has not received a Link Status In Service from its peer at the Once the association is established and M2PA has received a Start
time it sends the Link Status In Service, M2PA starts timer T1. Timer Request from MTP3, M2PA sends the Link Status Alignment message to its
T1 is stopped when M2PA receives Link Status In Service from its peer. If M2PA has not already received the Link Status Alignment
peer. If M2PA does not receive Link Status In Service from its peer message from its peer, then M2PA starts timer T1.
before T1 expires, then M2PA reports to MTP3 that the link is out of
service. Then M2PA uses the ABORT primitive to end the association.
Recommended value of T1 is 5-50 seconds. (Note that if the remote M2PA has not received a Start Request from its
MTP3, it will not send the Link Status Alignment message to the
local M2PA. Eventually timer T1 in the local M2PA will expire.)
Note that if the server M2PA has not received a Start Request from its M2PA stops timer T1 when it has received the Link Status Alignment
MTP3, it will not send the Link Status In Service message to the message from its peer.
client. Eventually the client will ABORT the association. The client
will then attempt to establish the association.
When the association is established, M2PA has sent Link Status In If timer T1 expires, then M2PA reports to MTP3 that the link is out of
Service to its peer, and has received Link Status In Service from its service. M2PA should leave the association established. M2PA waits for
peer, and there is no local processor outage condition, then M2PA MTP3 to initiate the alignment procedure again.
sends Link In Service to its MTP3.
If M2PA receives a Link Status of Processor Outage during alignment, When M2PA has both sent and received the Link Status Alignment
and M2PA had received a Start Request from its MTP3, M2PA shall report message, it has completed alignment and moves to the proving state.
M2PA starts the proving period timer T2. During the proving period,
M2PA sends Link Status Proving messages to its peer at an interval
defined by the protocol parameter Status_Interval. M2PA sends either
the Proving Normal or Proving Emergency message, according to the
Emergency and Emergency Ceases commands from MTP3. M2PA uses the value
of T2 corresponding to the Normal or Emergency state. However, if M2PA
receives a Link Status Proving Emergency message from its peer, then
M2PA shall use the Emergency value for T2.
Also while T2 is running, M2PA shall send Proving Data messages on the
User Data stream. These messages are sent at a rate equal to the
protocol parameter Proving_Data_Rate.
When the proving period timer T2 expires, M2PA shall determine the
association's performance as described in section 4.1.6 Error
Monitoring. If the association's performance is inadequate, M2PA shall
report to MTP3 that the link is out of service. M2PA should leave the
association established. M2PA waits for MTP3 to initiate the alignment
procedure again.
If the association's performance is satisfactory, M2PA shall start the
timer T3 and send Link Status Ready messages to its peer at interval
Status_Interval. These messages are used to verify that both ends have
completed proving.
M2PA shall stop timer T3 when it receives a Link Status Proving
Complete or User Data message from its peer. If timer T3 expires, then
M2PA reports to MTP3 that the link is out of service. M2PA should
leave the association established. M2PA waits for MTP3 to initiate the
alignment procedure again.
Note that if M2PA has already received a Link Status Ready message
from its peer when it finishes checking the association's performance,
there is no need to start timer T3. M2PA can just send Link Status
Ready to the peer and continue along.
When all of the following are true:
(a) M2PA has received a Start Request from MTP3.
(b) M2PA's proving period T2 has expired.
(c) M2PA has sent a Link Status Ready to its peer.
(d) M2PA has received a Link Status Ready OR User Data
message from its peer.
then M2PA shall send Link In Service to its MTP3.
If there is a local processor outage condition, M2PA sends Link Status
Processor Outage to its peer. When the local processor outage
condition ends, then M2PA shall send Link Status Processor Outage
Ended to its peer. M2PA shall attempt to complete the alignment
procedure during the local processor outage condition.
If M2PA receives a Link Status Processor Outage during alignment, and
M2PA had received a Start Request from its MTP3, M2PA shall report
Remote Processor Outage to MTP3. Remote Processor Outage to MTP3.
M2PA shall ignore the Emergency and Emergency Ceases commands from Recommended values:
MTP3.
4.1.3 Processor Outage T1 Alignment - Range: 1-60 seconds Default: 10 seconds
T2 Proving -
Normal - Range: 1-60 seconds Default: 10 seconds
Emergency - Range: 400-600 milliseconds Default: 500 milliseconds
T3 Ready - Range: 1-60 seconds Default: 10 seconds
Status_Interval - implementation dependent.
Proving_Data_Rate - implementation dependent.
4.1.4 Processor Outage
A processor outage occurs when M2PA cannot transfer messages because A processor outage occurs when M2PA cannot transfer messages because
of a condition at a higher layer than M2PA. of a condition at a higher layer than M2PA.
When M2PA detects a local processor outage, it sends a Link Status When M2PA detects a local processor outage, it sends a Link Status
message to its peer with status Processor Outage. M2PA shall discard message to its peer with status Processor Outage. M2PA shall also
any User Data messages received. M2PA shall also cease sending User cease sending User Data messages to SCTP for transmission.
Data messages to SCTP for transmission.
M2PA should periodically send a Link Status Processor Outage message
as long as there is a local processor outage.
The peer M2PA, upon receiving the Link Status Processor Outage The peer M2PA, upon receiving the Link Status Processor Outage
message, shall report Remote Processor Outage to its MTP3. M2PA ceases message, shall report Remote Processor Outage to its MTP3. The peer
sending User Data messages. M2PA ceases sending User Data messages. M2PA stops the Remote
Congestion timer T6 if it is running.
MTP3 sends a Flush Buffers or Continue command to M2PA. When the MTP3 sends a Flush Buffers or Continue command to M2PA. When the
processor outage ceases, MTP3 sends a Local Processor Recovered processor outage ceases, MTP3 sends a Local Processor Recovered
indication to M2PA. The local M2PA notifies its peer by sending a Link indication to M2PA. The local M2PA notifies its peer by sending a Link
Status message with status Processor Outage Ended. The peer notifies Status message with status Processor Outage Ended. The peer uses the
its MTP3 that the remote processor outage has ceased. Remote Processor Recovered Indication to notify its MTP3 that the
remote processor outage condition has ceased.
4.1.4 Level 2 Flow Control 4.1.5 Level 2 Flow Control
Notification of receive congestion from SCTP to M2PA is implementation Notification of receive congestion from SCTP to M2PA is implementation
dependent. This section assumes that there is some form of receive dependent. This section assumes that M2PA has some means of
determining when SCTP is in receive congestion, such as a receive
congestion notification from SCTP to M2PA. Since SCTP has its own congestion notification from SCTP to M2PA. Since SCTP has its own
congestion control, the purpose of the M2PA level 2 flow control is to congestion control, the purpose of the M2PA level 2 flow control is to
monitor the association and decide if it should be aborted. monitor the association and decide if it should be aborted.
If M2PA receives notification from its lower layer SCTP that SCTP is If M2PA determines that SCTP is in receive congestion for an
in receive congestion for an association, M2PA shall send a Link association, M2PA shall send a Link Status Busy message to its peer on
Status Busy message to its peer on that association. that association.
M2PA should periodically send a Link Status Busy message as long as
its SCTP is in receive congestion.
When the peer M2PA receives the Link Status Busy message, it shall When the peer M2PA receives the Link Status Busy message, it shall
start the Remote Congestion timer T6. If timer T6 expires, M2PA shall start the Remote Congestion timer T6. If timer T6 expires, M2PA shall
use the ABORT primitive to end the association and take the link out use the ABORT primitive to end the association and take the link out
of service. of service.
The peer M2PA shall continue transmitting messages to SCTP while its The peer M2PA shall continue transmitting messages to SCTP while its
T6 timer is running, i.e., while the other end is Busy. T6 timer is running, i.e., while the other end is Busy.
If M2PA receives notification from its lower layer SCTP that SCTP is If M2PA determines that SCTP is no longer in receive congestion for
no longer in receive congestion for the association, M2PA shall send a the association, M2PA shall send a Link Status Busy Ended message to
Link Status Busy Ended message to its peer on that association. its peer on that association.
When the peer M2PA receives the Link Status Busy Ended message, it When the peer M2PA receives the Link Status Busy Ended message, it
shall stop timer T6. shall stop timer T6.
Recommended value of T6 is 1-6 seconds. Recommended value of T6 is 1-6 seconds.
4.1.5 Error Monitoring 4.1.6 Error Monitoring
If M2PA loses the SCTP association for a link, M2PA shall report to If M2PA loses the SCTP association for a link, M2PA shall report to
MTP3 that the link is out of service. MTP3 that the link is out of service.
As long as the SCTP association is up, M2PA shall regularly invoke the As long as the SCTP association is up, M2PA shall regularly monitor
SCTP GETSRTTREPORT primitive to determine the Smooth Round Trip Time the association performance. It is recommended that M2PA use the
(SRTT) from SCTP. If the the SRTT exceeds the maximum acceptable following data to determine the performance of the association:
value, the link is considered failed and taken out of service. The
interval between successive SRTT requests and the maximum acceptable
SRTT value are determined by the parameters:
SRTT_measurement_interval - Smooth Round Trip Time (SRTT). This can be obtained from SCTP by
Range: 1 - 1000 seconds. invoking the SCTP GETSRTTREPORT primitive.
Default: 5 seconds.
SRTT_max - Frequency of SCTP retransmissions.
Range: 0-65,535 milliseconds.
Default: 1000 milliseconds.
4.1.6 Transmission Priorities - Frequency of SCTP Gap Acknowledgements received.
If these values are not acceptable, the link is considered failed and
taken out of service.
The acceptable values of these data are implementation dependent.
The interval between successive checks of the performance data should
be a configurable parameter. Its value is implementation dependent.
4.1.7 Transmission and Reception Priorities
In MTP, Link Status messages have priority over User Data messages In MTP, Link Status messages have priority over User Data messages
([2] Q.703, section 11.2). To achieve this in M2PA, Link Status and ([2] Q.703, section 11.2). To achieve this in M2PA, M2PA shall send
User Data messages shall be sent via SCTP on separate streams. All Link Status and User Data messages on separate streams in its SCTP
messages are sent using the ordered delivery option. association. All messages are sent using the ordered delivery option.
M2PA SHOULD give higher priority to reading the Link Status stream M2PA SHOULD give higher priority to reading the Link Status stream
over the User Data stream. over the User Data stream.
M2PA SHOULD give higher priority to receiving notifications from SCTP M2PA SHOULD give higher priority to receiving notifications from SCTP
over reading either the Link Status stream or the User Data stream. over reading either the Link Status stream or the User Data stream.
Implementation Note: If the SCTP implementation allows streams to have Implementation Note: If the SCTP implementation allows streams to have
different priorities for sending messages, then M2PA SHOULD set the different priorities for sending messages, then M2PA SHOULD set the
Link Status stream to a higher priority than the User Data stream. See Link Status stream to a higher priority than the User Data stream. See
[13] for a possible extension to SCTP to allow for stream priorities. [13] for a possible extension to SCTP to allow for stream priorities.
4.1.8 M2PA Version Control
A node upgraded to a newer version of M2PA SHOULD support the older
versions used on other nodes with which it is communicating. If that
is the case, then alignment can proceed normally.
In particular, it is recommended that for future modifications to this
protocol:
- Any newer version should be able to process the messages from a
lower version.
- A newer version of M2PA should refrain from sending messages to an
older version of M2PA messages that the older version cannot
process.
- If an older version of M2PA receives a message that it cannot
process, it should discard the message.
- In cases where different processing is done in two versions for the
same format of a message, then the newer version should contain
procedures to recognize this and handle it appropriately.
In case a newer version of M2PA is incompatible with an older version,
the newer version should recognize this and prevent the alignment of
the link. If a Link Status Alignment message with an unsupported
version is received by the newer version, the receiving end's M2PA
shall not complete the alignment procedure.
4.2 Procedures to Support the MTP3/MTP2 Interface 4.2 Procedures to Support the MTP3/MTP2 Interface
4.2.1 Sending/receiving messages 4.2.1 Sending/receiving messages
When MTP3 sends a message for transmission to M2PA, M2PA passes the When MTP3 sends a message for transmission to M2PA, M2PA passes the
corresponding M2PA message to SCTP using the SEND primitive. corresponding M2PA message to SCTP using the SEND primitive.
M2PA Link Status messages are passed to SCTP using the SEND primitive. M2PA Link Status messages are passed to SCTP using the SEND primitive.
Link Status and User Data messages shall be sent via SCTP on separate Link Status and User Data messages shall be sent via SCTP on separate
streams. streams.
When M2PA receives a Data message from SCTP, M2PA passes the message When M2PA receives a User Data message from SCTP, M2PA passes the
to MTP3. message to MTP3.
If M2PA receives a message from SCTP with an invalid Message Class or
unsupported Message Type in the Common Message Header, M2PA shall
discard the message.
4.2.2 Link activation and restoration 4.2.2 Link activation and restoration
When MTP3 requests that M2PA activate or restore a link by a Start When MTP3 requests that M2PA activate or restore a link by a Start
Request, M2PA shall follow the alignment procedure in section 4.1.2.
Request, M2PA shall follow the alignment procedure in section 4.1.3.
4.2.3 Link deactivation 4.2.3 Link deactivation
When MTP3 requests that M2PA deactivate a link by a Stop command, M2PA When MTP3 requests that M2PA deactivate a link by a Stop command, M2PA
shall send an ABORT primitive to SCTP. shall send an ABORT primitive to SCTP.
4.2.4 Flush Buffers, Continue 4.2.4 Flush Buffers, Continue
The Flush Buffers and Continue commands allow M2PA to resume normal The Flush Buffers and Continue commands allow M2PA to resume normal
operations (i.e., transmission of messages to SCTP and receiving operations (i.e., transmission of messages to SCTP and receiving
skipping to change at page 27, line 46 skipping to change at page 32, line 40
and transmitting messages. and transmitting messages.
4.2.5 MTP3 Signaling Link Congestion 4.2.5 MTP3 Signaling Link Congestion
Notification of transmit congestion from SCTP to its upper layer Notification of transmit congestion from SCTP to its upper layer
(M2PA) is implementation dependent. Nevertheless, M2PA should receive (M2PA) is implementation dependent. Nevertheless, M2PA should receive
notification from SCTP adequate to allow MTP3 to meet its requirements notification from SCTP adequate to allow MTP3 to meet its requirements
for signaling link transmit congestion in [2] Q.704, section 3.8. for signaling link transmit congestion in [2] Q.704, section 3.8.
M2PA shall use the Congestion Indication primitive to notify its upper M2PA shall use the Congestion Indication primitive to notify its upper
layer MTP3 when transmit buffer occupancy crosses the congestion layer MTP3 of changes in the signaling link congestion status and the
onset, discard, and abatement thresholds. For national networks with signaling link discard status. For national networks with multiple
multiple congestion threshold levels, M2PA shall notify MTP3 when congestion threshold levels, M2PA shall notify MTP3 of the congestion
transmit buffer occupancy crosses each level of the congestion onset, and discard status levels.
discard, and abatement thresholds.
Note: M2PA does not discard messages because of transmit Note: M2PA does not discard messages because of transmit
congestion. Discarding of messages due to transmit congestion is congestion. Discarding of messages due to transmit congestion is
performed by MTP3. performed by MTP3.
4.2.6 Changeover 4.2.6 Changeover
The objective of the changeover is to ensure that signaling traffic The objective of the changeover is to ensure that signaling traffic
carried by the unavailable signaling link is diverted to the carried by the unavailable signaling link is diverted to the
alternative signaling link(s) as quickly as possible while avoiding alternative signaling link(s) as quickly as possible while avoiding
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transmitted over the alternate links. References to stream sequence transmitted over the alternate links. References to stream sequence
numbers in this section refer only to the User Data stream's stream numbers in this section refer only to the User Data stream's stream
sequence numbers. sequence numbers.
In order to support changeover in M2PA, the SCTP Stream Sequence In order to support changeover in M2PA, the SCTP Stream Sequence
Numbers must be used in place of the Forward and Backward Sequence Numbers must be used in place of the Forward and Backward Sequence
Numbers (FSN/BSN) of SS7. Numbers (FSN/BSN) of SS7.
Stream Sequence Numbers used by SCTP are 16 bits long. MTP2's Forward Stream Sequence Numbers used by SCTP are 16 bits long. MTP2's Forward
and Backward Sequence Numbers are only seven bits long. Hence it is and Backward Sequence Numbers are only seven bits long. Hence it is
necessary for MTP3 to accomodate the larger SSNs. This is done through necessary for MTP3 to accommodate the larger SSNs. This is done
the use of the Extended Changeover Order (XCO) and Extended Changeover through the use of the Extended Changeover Order (XCO) and Extended
Acknowledgement (XCA) messages instead of the Changeover Order (COO) Changeover Acknowledgement (XCA) messages instead of the Changeover
and Changeover Acknowledgement (COA) messages. The XCO and XCA Order (COO) and Changeover Acknowledgement (COA) messages. The XCO and
messages are specified in Reference [7] section 9.8.1. Only the XCO XCA messages are specified in Reference [7] section 9.8.1 and
and XCA messages from [7] are required. These messages have a 24-bit Reference [3] T1.111.4, section 15.4. Only the XCO and XCA messages
field for the sequence number. The upper 8 bits of the 24 bit field from [7] or [3] are required. The SSN is placed in the XCO/XCA message
should be set to 0, and the SSN placed in the lower 16 bits. as explained in [7] and [3].
(Note that the Stream Sequence Numbers are used instead of the (Note that the Stream Sequence Numbers are used instead of the
Transmission Sequence Numbers. The Transmission Sequence Numbers are Transmission Sequence Numbers. The Transmission Sequence Numbers are
32 bits long, and therefore would not fit in the XCO and XCA 32 bits long, and therefore would not fit in the XCO and XCA
messages.) messages. Furthermore, TSNs do not number User Data messages
consecutively. TSNs also number Link Status and SCTP-originated
messages, which should not be retrieved during the changeover
procedure.)
Also, the following MTP3/MTP2 primitives must use the larger sequence Also, the following MTP3/MTP2 primitives must use the larger sequence
numbers: numbers:
- BSNT Indication - BSNT Confirmation
- Retrieval Request and FSNC - Retrieval Request and FSNC
For data retrieval, MTP3 requests the Backward Sequence Number to be For data retrieval, MTP3 requests the Backward Sequence Number to be
Transmitted (BSNT) from M2PA through the Retrieve BSNT Transmitted (BSNT) from M2PA through the Retrieve BSNT
request. Normally, SCTP receives messages in order, in which case the request. Normally, SCTP receives messages in order, in which case the
BSNT is the last message received by SCTP. However, because of BSNT is the last message received by SCTP. However, because of
congestion or a failure condition, the sequence numbers of the congestion or a failure condition, the sequence numbers of the
acknowledged messages may have gaps. In particular, the SCTP SACK acknowledged messages may have gaps. In particular, the SCTP SACK
(selective acknowledgement message) message can have several of these (selective acknowledgement message) message can have several of these
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- Retrieval Request and FSNC - Retrieval Request and FSNC
For data retrieval, MTP3 requests the Backward Sequence Number to be For data retrieval, MTP3 requests the Backward Sequence Number to be
Transmitted (BSNT) from M2PA through the Retrieve BSNT Transmitted (BSNT) from M2PA through the Retrieve BSNT
request. Normally, SCTP receives messages in order, in which case the request. Normally, SCTP receives messages in order, in which case the
BSNT is the last message received by SCTP. However, because of BSNT is the last message received by SCTP. However, because of
congestion or a failure condition, the sequence numbers of the congestion or a failure condition, the sequence numbers of the
acknowledged messages may have gaps. In particular, the SCTP SACK acknowledged messages may have gaps. In particular, the SCTP SACK
(selective acknowledgement message) message can have several of these (selective acknowledgement message) message can have several of these
gaps. In this case, it is necessary to scan through these gaps and gaps. In this case, it is necessary to scan through these gaps and
find the sequence number before the first gap. This is the number find the sequence number before the first gap. This is the number
considered as the BSNT and communicated to MTP3. M2PA sends the BSNT considered as the BSNT and communicated to MTP3. M2PA sends the BSNT
value to MTP3 in the BSNT indication. In the same way, the remote end value to MTP3 in the BSNT confirmation. In the same way, the remote
also detects its BSNT. The MTP3 layers exchange BSNT values through end also detects its BSNT. The MTP3 layers exchange BSNT values
the XCO/XCA messages. The BSNT received from the other end is called through the XCO and XCA messages. The BSNT received from the other end
the FSNC. When MTP3 receives the FSNC from the other end, MTP3 is called the FSNC. When MTP3 receives the FSNC from the other end,
retrieves all the unsent and unacknowledged messages starting with MTP3 retrieves all the unsent and unacknowledged messages starting
sequence number (FSNC + 1). This is accomplished through a Retrieval with sequence number (FSNC + 1). This is accomplished through a
Request and FSNC request. After all the messages are sent from M2PA to Retrieval Request and FSNC request. After all the messages are sent
MTP3, M2PA sends a Retrieval Complete indication to MTP3. from M2PA to MTP3, M2PA sends a Retrieval Complete indication to MTP3.
As an example of how the BSNT is determined, suppose the following As an example of how the BSNT is determined, suppose the following
SSNs had been received by SCTP on the Data Stream when it is time to SSNs had been received by SCTP on the Data Stream when it is time to
do the changeover procedure: 1-10, 13, 14, 16. Then M2PA tells its do the changeover procedure: 1-10, 13, 14, 16. Then M2PA tells its
upper layer that the last message it received (the BSNT) was 10. SCTP upper layer that the last message it received (the BSNT) was 10. SCTP
has not delivered 13, 14, and 16 to M2PA because to do so would has not delivered 13, 14, and 16 to M2PA because to do so would
violate ordered delivery within the stream. The value of 10 is violate ordered delivery within the stream. The value of 10 is
transmitted to the remote end by MTP3 in the XCO/XCA message. So the transmitted to the remote end by MTP3 in the XCO/XCA message. So the
remote end will retransmit 11-16 on an alternate link. remote end will retransmit 11-16 on an alternate link.
If there are any messages on the SCTP receive queue, M2PA SHOULD If there are any messages on the SCTP receive queue, M2PA SHOULD
receive these messages and deliver them to MTP3. Note that SCTP does receive these messages and deliver them to MTP3. Note that SCTP does
not deliver incoming messages after the first gap (if any) in the not deliver incoming messages after the first gap (if any) in the
SSNs, since this would violate ordered delivery within the stream. In SSNs, since this would violate ordered delivery within the stream. In
the example above, this would mean that messages 1-10 SHOULD be the example above, this would mean that messages 1-10 SHOULD be
received. Otherwise, these unreceived messages might be lost, since received. Otherwise, these unreceived messages might be lost, since
SCTP might have acknowledged them. SCTP might have acknowledged them.
Note that the sequence numbers and messages requested by MTP3 may be Note that the sequence numbers and messages requested by MTP3 may be
obtained by M2PA from SCTP via the Communication Lost primitive [5]. obtained by M2PA from SCTP via the Communication Lost primitive [5].
Retrieval of messages is an optional feature in SCTP. To perform data Retrieval of messages is an optional feature in SCTP that is required
retrieval, it is necessary that this option be implemented, and that by M2PA. To perform data retrieval, it is necessary that SCTP identify
the SSNs of the messages are identified. SCTP must retain the messages the SSNs of the messages that M2PA retrieves. SCTP must retain the
for retrieval by MTP3/M2PA whenever an association is aborted. SCTP messages for retrieval by MTP3/M2PA whenever an association is
must be able to return messages to M2PA so that M2PA can perform aborted. SCTP must be able to return messages to M2PA so that M2PA can
retrieval for MTP3. There are various ways that this can be perform retrieval for MTP3. There are various ways that this can be
implemented, such as: implemented, such as:
(1) SCTP provides a way for M2PA to request retrieval of messages (1) SCTP provides a way for M2PA to request retrieval of messages
for a specified stream and SSN(s). for a specified stream and SSN(s).
(2) SCTP retrieves all messages and identifies the stream and SSN (2) SCTP retrieves all messages and identifies the stream and SSN
of each message. M2PA then must select the appropriate messages of each message. M2PA then must select the appropriate messages
to pass up to MTP3. to pass up to MTP3.
M2PA must be able to respond to the BSNT request from MTP3. There are M2PA must be able to respond to the BSNT request from MTP3. There are
various ways of implementing this, such as having SCTP provide the various ways of implementing this, such as having SCTP provide the
BSNT. BSNT.
It is helpful for M2PA to have access to the first and last SSN in It is helpful for M2PA to have access to the first and last SSN in
SCTP's transmission queue. This information could be used to determine SCTP's transmission queue. This information could be used to determine
if the FSNC received from the remote end is a valid value. if the FSNC received from the remote end is a valid value.
If M2PA receives a Retrieve BSNT request from MTP3, M2PA shall respond If M2PA receives a Retrieve BSNT request from MTP3, M2PA shall respond
with the BSNT indication. The BSNT value is the SCTP stream sequence with the BSNT confirmation. The BSNT value is the SCTP stream sequence
number of the last message received by SCTP User Data stream before number of the last message received by SCTP User Data stream before
any gaps in the stream sequence numbers. any gaps in the stream sequence numbers.
(Note that any messages with stream sequence number greater than this (Note that any messages received with a stream sequence number greater
BSNT value have been acknowledged by the receiving SCTP, but have not than this BSNT value have been acknowledged by the receiving SCTP, but
been passed up to M2PA. These messages are discarded by the receiving have not been passed up to M2PA. These messages are discarded by the
SCTP and are not delivered to the upper layer M2PA. Therefore these receiving SCTP and are not delivered to the upper layer
messages should be retransmitted by the far end on the alternate M2PA. Therefore these messages should be retransmitted by the far end
link.) on the alternate link.)
If M2PA receives a Retrieval Request and FSNC request from MTP3, M2PA If M2PA receives a Retrieval Request and FSNC request from MTP3, M2PA
shall retrieve from SCTP in order and deliver to MTP3: shall retrieve from SCTP in order and deliver to MTP3:
(a) any transmitted User Data messages beginning with the first (a) any transmitted User Data messages beginning with the first
unacknowledged message with stream sequence number greater unacknowledged message with stream sequence number greater
than FSNC. than FSNC.
(b) any untransmitted User Data messages in SCTP. (b) any untransmitted User Data messages in SCTP.
(c) any untransmitted User Data messages M2PA has not delivered (c) any untransmitted User Data messages M2PA has not delivered
to SCTP for transmission. to SCTP for transmission.
Then M2PA shall send the Retrieval Complete indication to MTP3. Then M2PA shall send the Retrieval Complete indication to MTP3.
For emergency changover, MTP3 retrieves only the unsent messages for For emergency changeover, MTP3 retrieves only the unsent messages for
transmission on the alternate link(s). If M2PA receives a Retrieval transmission on the alternate link(s). If M2PA receives a Retrieval
Request and FSNC request with no FSNC value, or with an invalid FSNC, Request and FSNC request with no FSNC value, or with an invalid FSNC,
then M2PA shall retrieve from SCTP in order and deliver to MTP3: then M2PA shall retrieve from SCTP in order and deliver to MTP3:
(a) any untransmitted User Data messages in SCTP. (a) any untransmitted User Data messages in SCTP.
(b) any untransmitted User Data messages M2PA has not delivered (b) any untransmitted User Data messages M2PA has not delivered
to SCTP for transmission. to SCTP for transmission.
Then M2PA shall send the Retrieval Complete indication to MTP3. Then M2PA shall send the Retrieval Complete indication to MTP3.
Note: The changeover procedure makes it impossible for M2PA to have 4.2.6.1 Multiple User Data Streams and Changeover
multiple User Data streams in a direction for one link. Buffer
The changeover procedure makes it problematic for M2PA to have
multiple User Data streams in one direction for a link. Buffer
updating would have to be done for each User Data stream separately to updating would have to be done for each User Data stream separately to
avoid duplication of messages. But MTP3 provides for only one XCO avoid duplication or loss of messages. But MTP3 provides for only one
message for sending the last-received SSN. XCO/XCA message for sending the last-received SSN.
M2PA links with multiple User Data streams would be possible if a
multiple-BSNT XCO/XCA message is defined in MTP3, or MTP3 allows
multiple XCO/XCA messages (one for each User Data stream) to be sent
during a changeover. This is beyond the scope of this document.
Another attempt to solve this problem and allow for multiple User Data
streams, without changes to MTP3 messages and procedures, is to
introduce sequence numbering of User Data messages at the M2PA
layer. The M2PA sequence numbers would be used instead of SCTP SSNs in
the XCO/XCA messages. However, since the M2PA messages would be
delivered over multiple streams, there could be a gap in the M2PA
sequence numbers at the receiving end when the changeover procedure
begins. There would be a possibility of losing the messages in the
gap, or duplicating messages after the gap.
5. Examples of M2PA Procedures 5. Examples of M2PA Procedures
In general, messages passed between MTP3 and M2PA are the same as In general, messages passed between MTP3 and M2PA are the same as
those passed between MTP3 and MTP2. M2PA interprets messages from those passed between MTP3 and MTP2. M2PA interprets messages from
MTP3 and sends the appropriate message to SCTP. Likewise, messages MTP3 and sends the appropriate message to SCTP. Likewise, messages
from SCTP are used to generate a meaningful message to MTP3. from SCTP are used to generate a meaningful message to MTP3.
Note that throughout this section, the primitives between MTP3 and Note that throughout this section, the primitives between MTP3 and
M2PA are named using the MTP terminology [1][2]. Communications M2PA are named using the MTP terminology [1][2]. Communications
skipping to change at page 32, line 8 skipping to change at page 37, line 8
5.1 Link Initialization (Alignment) 5.1 Link Initialization (Alignment)
An example of the message flow to bring an SS7 link in service is An example of the message flow to bring an SS7 link in service is
shown below. Alignment is done by both ends of the link. To simplify the shown below. Alignment is done by both ends of the link. To simplify the
diagram, alignment is shown on one end only. It is assumed in this diagram, alignment is shown on one end only. It is assumed in this
example that SCTP has been initialized. example that SCTP has been initialized.
MTP3 M2PA SCTP SCTP M2PA MTP3 MTP3 M2PA SCTP SCTP M2PA MTP3
---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ----
Out of Service
<------------
Emergency OR Emergency OR
Emergency Ceases Emergency Ceases
------------> ------------>
Start Start
------------> ------------>
Associate Associate
------------> ------------>
(SCTP Association (SCTP Association
procedure) procedure)
Communication Up Communication Up Communication Up Communication Up
<------------ ------------> <------------ ------------>
Even though the SCTP association is established, it is important that
M2PA not send MTP3 data at this point. It must be confirmed that both
ends of the link are ready for traffic. Otherwise, messages could be
lost. The endpoints must exchange In Service messages.
MTP3 M2PA SCTP SCTP M2PA MTP3 MTP3 M2PA SCTP SCTP M2PA MTP3
---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ----
Link Status Alignment
------------------------------------>
Start timer T1
Link Status Alignment
<------------------------------------
Stop timer T1
Start timer T2
Proving period begins. (Messages from remote end not shown.)
Link Status Proving
Proving Data
------------------------------------>
------------------------------------>
------------------------------------>
------------------------------------>
------------------------------------>
------------------------------------>
Timer T2 expires
Proving period ends. Check association performance.
Get SRTT Report Get SRTT Report
------------> ------------>
Link Status In Service Send Link Status Ready until the remote end completes its proving
period.
Start timer T3
Link Status Ready
------------------------------------>
------------------------------------>
------------------------------------>
------------------------------------> ------------------------------------>
Link Status In Service Link Status Ready
<------------------------------------ <------------------------------------
Stop timer T3
In Service In Service In Service In Service
<------------ ------------> <------------ ------------>
At this point, MTP3 may begin sending data messages. At this point, MTP3 may begin sending data messages.
5.2 Message Transmission and Reception 5.2 Message Transmission and Reception
Messages are transmitted using the Data Request primitive from MTP3 to Messages are transmitted using the Data Request primitive from MTP3 to
M2PA. The diagram shows the case where the Link is In Service. The M2PA. The diagram shows the case where the Link is In Service. The
message is passed from MTP3 of the source to MTP3 of the destination. message is passed from MTP3 of the source to MTP3 of the destination.
skipping to change at page 39, line 8 skipping to change at page 45, line 8
Communication Lost Communication Lost
<------------ <------------
Out of Service Out of Service
<------------ <------------
5.8 Link Changeover 5.8 Link Changeover
In this example, MTP3 performs a changeover because the link went out In this example, MTP3 performs a changeover because the link went out
of service. MTP3 selects a different link for retransmitting the of service. MTP3 selects a different link to retransmit the
unacknowledged and unsent messages. unacknowledged and unsent messages.
Note that in this example, the sequence numbers and messages requested Note that in this example, the sequence numbers and messages requested
by MTP3 are sent from SCTP to M2PA in the Communication Lost by MTP3 are sent from SCTP to M2PA in the Communication Lost
primitive. In general, the retrieval of sequence numbers and messages primitive. In general, the retrieval of sequence numbers and messages
is implementation dependent. is implementation dependent.
MTP3 M2PA SCTP SCTP M2PA MTP3 MTP3 M2PA SCTP SCTP M2PA MTP3
---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ----
skipping to change at page 40, line 21 skipping to change at page 46, line 21
Out of Service Out of Service
<------------ <------------
Retrieve BSNT Retrieve BSNT
------------> ------------>
(M2PA locates (M2PA locates
first gap in first gap in
received messages) received messages)
BSNT Indication BSNT Confirmation
<------------ <------------
XCO (BSNT) on another link XCO (BSNT) on another link
------------------------------------------------------------> ------------------------------------------------------------>
Retrieve BSNT Retrieve BSNT
<------------ <------------
BSNT Indication BSNT Confirmation
------------> ------------>
XCA (BSNT) XCA (BSNT)
<------------------------------------------------------------ <------------------------------------------------------------
Retrieval Request Retrieval Request
and FSNC and FSNC
------------> ------------>
(M2PA locates (M2PA locates
skipping to change at page 41, line 41 skipping to change at page 47, line 41
- Masquerade - Masquerade
- Improper Monopolization of Services - Improper Monopolization of Services
When M2PA is running in professionally managed corporate or service When M2PA is running in professionally managed corporate or service
provider network, it is reasonable to expect that this network provider network, it is reasonable to expect that this network
includes an appropriate security policy framework. The "Site Security includes an appropriate security policy framework. The "Site Security
Handbook" [11] SHOULD be consulted for guidance. Handbook" [11] SHOULD be consulted for guidance.
When the network in which M2PA runs involves more than one party, it When the network in which M2PA runs involves more than one party
MAY NOT be reasonable to expect that all parties have implemented (e.g., a non-private network), it MAY NOT be reasonable to expect that
security in a sufficient manner. In such a case, it is recommended all parties have implemented security in a sufficient manner. In such
that IPSEC be used to ensure confidentiality of user payload. Consult a case, it is recommended that IPSEC be used to ensure confidentiality
[12] for more information on configuring IPSEC services. of user payload. Consult [12] for more information on configuring
IPSEC services.
6.2 Protecting Confidentiality 6.2 Protecting Confidentiality
Particularly for mobile users, the requirement for confidentiality MAY Particularly for mobile users, the requirement for confidentiality MAY
include the masking of IP addresses and ports. In this case include the masking of IP addresses and ports. In this case
application-level encryption is not sufficient. IPSEC ESP SHOULD be application-level encryption is not sufficient. IPSEC ESP SHOULD be
used instead. Regardless of which level performs the encryption, the used instead. Regardless of which level performs the encryption, the
IPSEC ISAKMP service SHOULD be used for key management. IPSEC ISAKMP service SHOULD be used for key management.
7. IANA Considerations 7. IANA Considerations
7.1 SCTP Payload Protocol Identifier
The SCTP (and UDP/TCP) Registered User Port Number Assignment for M2PA The SCTP (and UDP/TCP) Registered User Port Number Assignment for M2PA
is TBD. is TBD.
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 SCTP Payload Data chunk is
M2PA TBD M2PA TBD
The SCTP Payload Protocol Identifier is included in each SCTP Data The SCTP Payload Protocol Identifier is included in each SCTP Data
chunk, to indicate which protocol the SCTP is carrying. This Payload chunk, to indicate which protocol the SCTP is carrying. This Payload
Protocol Identifier is not directly used by SCTP but may be used by Protocol Identifier is not directly used by SCTP but may be used by
certain network entities to identify the type of information being certain network entities to identify the type of information being
carried in a Data chunk. carried in a Data chunk.
The User Adaptation peer may use the Payload Protocol Identifier as a The User Adaptation peer may use the Payload Protocol Identifier as a
way of determining additional information about the data being way of determining additional information about the data being
presented to it by SCTP. presented to it by SCTP.
7.2 M2PA Protocol Extensions
This protocol may be extended through IANA in three ways:
- through definition of additional message classes,
- through definition of additional message types, and
- through definition of additional message parameters.
The definition and use of new message classes, types, and parameters
is an integral part of SIGTRAN adaptation layers. Thus, these
extensions are assigned by IANA through an IETF Consensus action as
defined in [14].
The proposed extension must in no way adversely affect the general
working of the protocol.
7.2.1 IETF Defined Message Classes
The documentation for a new message class MUST include the following
information:
(a) A long and short name for the message class.
(b) A detailed description of the purpose of the message class.
7.2.2 IETF Defined Message Types
Documentation of the message type MUST contain the following
information:
(a) A long and short name for the new message type.
(b) A detailed description of the structure of the message.
(c) A detailed definition and description of the intended use
of each field within the message.
(d) A detailed procedural description of the use of the new
message type within the operation of the protocol.
(e) A detailed description of error conditions when receiving this
message type.
When an implementation receives a message type which it does not
support, it MUST discard the message.
7.2.3 IETF-defined Parameter Extension
Documentation of the message parameter MUST contain the following
information:
(a) Name of the parameter type.
(b) Detailed description of the structure of the parameter field.
(c) Detailed definition of each component of the parameter value.
(d) Detailed description of the intended use of this parameter type,
and an indication of whether and under what circumstances
multiple instances of this parameter type may be found within
the same message type.
8. Acknowledgements 8. Acknowledgements
The authors would like to thank the following for their valuable The authors would like to thank the following for their valuable
comments and suggestions: Brian Tatum, Ian Rytina, Al Varney. comments and suggestions: Brian Tatum, Jeff Copley, Monique Bernard,
Wayne Davis, Cliff Thomas, Brian Bidulock, Ian Rytina, Al Varney.
9. References 9. References
[1] ITU-T Recommendation Q.700, 'Introduction To ITU-T Signalling [1] ITU-T Recommendation Q.700, 'Introduction To ITU-T Signalling
System No. 7 (SS7)' System No. 7 (SS7)'.
[2] ITU-T Recommendation Q.701-Q.705, 'Signalling System No. 7 [2] ITU-T Recommendation Q.701-Q.705, 'Signalling System No. 7
(SS7) - Message Transfer Part (MTP)' (SS7) - Message Transfer Part (MTP)'.
[3] ANSI T1.111-2000, American National Standard for [3] ANSI T1.111-2000, American National Standard for
Telecommunications - Signaling System Number 7 (SS7) - Telecommunications - Signaling System Number 7 (SS7) -
Message Transfer Part (MTP), 2000 Message Transfer Part (MTP), 2000.
[4] RFC 2719, Framework Architecture for Signaling Transport, [4] RFC 2719, Framework Architecture for Signaling Transport,
October 1999 October 1999.
[5] RFC 2960, Stream Control Transmission Protocol, [5] RFC 2960, Stream Control Transmission Protocol,
October 2000 October 2000.
[6] SS7 MTP2-User Adaptation Layer, draft-ietf-sigtran-m2ua-07.txt, [6] SS7 MTP2-User Adaptation Layer, draft-ietf-sigtran-m2ua-09.txt,
February 2001 July 2001.
[7] ITU-T Recommendation Q.2210, 'Message transfer part level 3 [7] ITU-T Recommendation Q.2210, 'Message transfer part level 3
functions and messages using the services of ITU-T functions and messages using the services of ITU-T
Recommendation Q.2140' Recommendation Q.2140'.
[8] Bradner, S. "Key words for use in RFCs to Indicate Requirement [8] Bradner, S. "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997. Levels", BCP 14, RFC 2119, March 1997.
[9] Telecommunication Technology Committee (TTC) Standard JT-Q704, [9] Telecommunication Technology Committee (TTC) Standard JT-Q704,
'Message Transfer Part Signaling Network Functions', 'Message Transfer Part Signaling Network Functions',
April 28, 1992. April 28, 1992.
[10] ITU-T Recommendation Q.2140, 'B-ISDN ATM Adaptation Layer', [10] ITU-T Recommendation Q.2140, 'B-ISDN ATM Adaptation Layer',
February 1995 February 1995.
[11] RFC 2196, Site Security Handbook, September 1997 [11] RFC 2196, Site Security Handbook, September 1997.
[12] RFC 2401, Security Architecture for the Internet Protocol, [12] RFC 2401, Security Architecture for the Internet Protocol,
November 1998 November 1998.
[13] SCTP Stream Based Flow Limiting Methods, [13] SCTP Extensions for Dynamic Reconfiguration of IP Addresses
draft-ietf-sigtran-srwnd-sctp-00.txt, January 31, 2001 and Enforcement of Flow and Message Limits,
draft-ietf-tsvwg-addip-sctp-02.txt, June 29, 2001.
10. Author's Addresses [14] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
Considerations Section in RFCs", BCP 26, RFC 2434, October
1998.
[15] RFC 791, Internet Protocol, September 1981.
10. Authors' Addresses
Tom George Tel: +1-972-519-3168 Tom George Tel: +1-972-519-3168
Alcatel USA EMail: tom.george@usa.alcatel.com Alcatel USA, Inc. EMail: Tom.George@usa.alcatel.com
1000 Coit Road 1000 Coit Road
Plano, TX 75075 Plano, TX 75075
USA USA
Ram Dantu, Ph.D. Tel: +1-469-255-0716 Ram Dantu, Ph.D. Tel: +1-469-255-0716
Cisco Systems Inc. EMail: rdantu@cisco.com Cisco Systems Inc. EMail: rdantu@cisco.com
17919 Waterview Parkway 17919 Waterview Parkway
Dallas, TX 75252 Dallas, TX 75252
USA USA
skipping to change at page 44, line 32 skipping to change at page 51, line 32
445 South Street 445 South Street
Morristown, NJ 07960 Morristown, NJ 07960
USA USA
Hanns Juergen Schwarzbauer Tel: +49-89-722-24236 Hanns Juergen Schwarzbauer Tel: +49-89-722-24236
SIEMENS AG HannsJuergen.Schwarzbauer@icn.siemens.de SIEMENS AG HannsJuergen.Schwarzbauer@icn.siemens.de
Hofmannstr. 51 Hofmannstr. 51
81359 Munich 81359 Munich
Germany Germany
Greg Sidebottom Tel: +1-613-763-7305 Greg Sidebottom
Nortel Networks EMail: gregside@nortelnetworks.com Kanata, Ontario EMail: gregside@home.com
3685 Richmond Rd, Canada
Nepean, Ontario
Canada K2H5B7
Ken Morneault Tel: +1-703-484-3323 Ken Morneault Tel: +1-703-484-3323
Cisco Systems Inc. EMail: kmorneau@cisco.com Cisco Systems Inc. EMail: kmorneau@cisco.com
13615 Dulles Technology Drive 13615 Dulles Technology Drive
Herndon, VA. 20171 Herndon, VA 20171
USA USA
This Internet Draft expires September 2001. This Internet Draft expires January 2002.
 End of changes. 

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