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INTERNET-DRAFT                                             L. Coene(Ed)
Internet Engineering Task Force                                 Siemens
Issued:  February 2002                                        J. Pastor
Expires: August 2002                                           Ericsson





  Telephony Signalling Transport over SCTP applicability statement
      <draft-ietf-sigtran-signalling-over-sctp-applic-04.txt>


Status of this Memo



    This document is an Internet-Draft and is in full conformance with
    all provisions of Section 10 of RFC2026. Internet-Drafts are working
    documents of the Internet Engineering Task Force (IETF), its areas,
    and its working groups.  Note that other groups may also distribute
    working documents as Internet-Drafts.

    Internet-Drafts are draft documents valid for a maximum of six
    months and may be updated, replaced, or obsoleted by other documents
    at any time.  It is inappropriate to use Internet-Drafts as
    reference material or to cite them other than as "work in progress."

    The list of current Internet-Drafts can be accessed at
    http://www.ietf.org/ietf/1ID-abstracts.txt

    The list of Internet-Draft Shadow Directories can be accessed at
    http://www.ietf.org/shadow.html


Abstract


    This document describes the applicability of the Stream Control
    Transmission Protocol (SCTP)[RFC2960] for transport of telephony
    signalling information over IP infrastructure. Special
    considerations for using SCTP to meet the requirements of
    transporting telephony signalling [RFC2719] are discussed.












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                            Table of contents




   Telephony signalling over SCTP Applicability statement .........   ii
   Chapter 1: Introduction ........................................    2
   Chapter 1.1: Terminology .......................................    2
   Chapter 1.2: Contributors ......................................    3
   Chapter 1.3: Overview .........................................     3
   Chapter 2: Applicability of telephony signalling transport
   using SCTP .....................................................    4
   Chapter 3: Issues for transporting Telephony signalling
   information over SCTP ..........................................    4
   Chapter 3.1: Congestion control ................................    4
   Chapter 3.2: Detection of failures .............................    5
   Chapter 3.2.1: Retransmission TimeOut (RTO) calculation ........    5
   Chapter 3.2.2: Heartbeat .......................................    5
   Chapter 3.2.3: Maximum Number of retransmissions ...............    5
   Chapter 3.3:  Shorten end-to-end message delay .................    6
   Chapter 3.4: Bundling considerations ...........................    6
   Chapter 3.5: Stream Usage ......................................    6
   Chapter 4: User Adaptation Layers...............................    6
   Chapter 4.1: IUA (ISDN Q.921 User Adaptation). .................    7
   Chapter 4.2: V5UA (V5.2-User Adaptation) Layer..................    8
   Chapter 4.3: M2UA (SS7 MTP2 User Adaptation) Layer..............    8
   Chapter 4.4: M2PA (SS7 MTP2-User Peer-to-Peer Adaptation) Layer.    9
   Chapter 4.5: M3UA (SS7 MTP3 User Adaptation) Layer..............   11
   Chapter 4.6: SUA (SS7 SCCP User Adaptation) Layer...............   11
   Chapter 5: Security considerations .............................   12
   Chapter 6: References and related work .........................   13
   Chapter 7: Acknowledgments .....................................   13
   Chapter 8: Author's address ....................................   14












1 INTRODUCTION


    Transport of telephony signalling requires special
    considerations. In order to use SCTP, special care must be taken to
    meet the performance, timing and failure management requirements.



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1.1 Terminology


    The following terms are commonly identified in related work:


    Association: SCTP connection between two endpoints.

    Stream: A uni-directional logical channel established within an
    association, within which all user messages are delivered in
    sequence except for those submitted to the unordered delivery
    service.




1.2 Contributors


    The following people contributed to the document: L. Coene(Editor),
    M.  Tuexen, G. Verwimp, J. Loughney, R.R. Stewart, Qiaobing Xie,
    M. Holdrege, M.C. Belinchon, A. Jungmaier, J. Pastor and L. Ong.


1.3 Overview


    SCTP provides a general purpose, reliable transport between two
    endpoints.

    The following functions are provided by SCTP:

    - Reliable Data Transfer

    - Multiple streams to help avoid head-of-line blocking

    - Ordered and unordered data delivery on a per-stream basis

    - Bundling and fragmentation of user data

    - Congestion and flow control

    - Support continuous monitoring of reachability

    - Graceful termination of association

    - Support of multi-homing for added reliability

    - Protection against blind denial-of-service attacks

    - Protection against blind masquerade attacks

    Telephony Signalling transport over IP normally uses the following

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    architecture:

                    Telephony Application
                              |
             +------------------------------------+
             |   Signalling Adaptation module     |
             +------------------------------------+
                              |
             +------------------------------------+
             |Stream Control Transmission Protocol|
             |             (SCTP)                 |
             +------------------------------------+
                              |
               Internet Protocol (IPv4/IPv6)

    Figure 1.1: Telephony signalling transport protocol stack


    The components of the protocol stack are :

    (1) Adaptation modules are used when the telephony application needs
    to preserve an existing primitive interface. (e.g. management
    indications, data operation primitives, ... for a particular
    user/application protocol).

    (2) SCTP, specially configured to meet the telephony application
    performance requirements.

    (3) The standard Internet Protocol.



2  Applicability of Telephony Signalling transport using SCTP


    SCTP can be used as the transport protocol for telephony
    applications.  Message boundaries are preserved during data
    transport and so no message delineation is needed. The user data can
    be delivered by the order of transmission within a stream(in
    sequence delivery) or the order of arrival.

    SCTP can be used to provide redundancy and fault tolerance at the
    transport layer and below. Telephony applications needing this level
    of fault tolerance can make use of SCTP's multi-homing support.

    SCTP can be used for telephony applications where head-of-line
    blocking is a concern. Such an application should use multiple
    streams to provide independent ordering of telephony signalling
    messages.



3 Issues for transporting telephony signalling over SCTP


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3.1 Congestion Control


    The basic mechanism of congestion control in SCTP have been
    described in [RFC2960]. SCTP congestion control sometimes conflicts
    with the timing requirements of telephony signalling transport.

    In an engineered network (e.g. a private intranet), in which network
    capacity and maximum traffic is very well understood, some telephony
    signalling applications may choose to relax the congestion control
    rules in order to satisfy the timing requirements.  But this should
    be done without destabilising the network, otherwise this would lead
    to potential congestion collapse of the network.

    Some telephony signalling applications may have their own congestion
    control and flow control techniques. These techniques may interact
    with the congestion control procedures in SCTP.  Additionally,
    telephony applications may use SCTP stream based flow control
    [SCTPFLOW].



3.2 Detection of failures

    Telephony systems often must achieve high availability in operation.
    For example, they are often required to be able to preserve stable
    calls during a component failure. Therefore error situations at the
    transport layer and below must be detected very fast so that the
    application can take approriate steps to recover and preserve the
    stable calls. This poses special requirements on SCTP to discover
    unreachablility of a destination address or a peer.



3.2.1 Retransmission TimeOut (RTO) calculation

    The SCTP protocol parameter RTO.Min value has a direct impact on the
    calculation of the RTO itself. Some telephony applications want to
    lower the value of the RTO.Min to less than 1 second. This would
    allow the message sender to reach the maximum
    number-of-retransmission threshold faster in the case of network
    failures. However, lowering RTO.Min may have a negative impact on
    network behaviour [ALLMAN99].

    In some rare cases, telephony applications might not want to use the
    exponential timer back-off concept in RTO calculation in order to
    speed up failure detection. The danger of doing this is that, when
    network congestion occurs, not backing off the timer may worsen the
    congestion situation. Therefore, this strategy should never be used
    in public Internet.

    It should be noted that not using delayed SACK will also help faster

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    failure detection.



3.2.2 Heartbeat

    For faster detection of (un)availability of idle paths, the
    telephony application may consider lowering the SCTP parameter
    HB.interval. It should be noted this will result in a higher traffic
    load.



3.2.3 Maximum number of retransmissions

    Setting Path.Max.Retrans and Association.Max.Retrans SCTP parameters
    to lower values will speed up both destination address and peer
    failure detection. However, if these values are set too low, the
    probability of false detections will increase.



3.3 Shorten end-to-end message delay

    Telephony applications often require short end-to-end message
    delays.  The methods described in section 3.2.1 on lowering RTO and
    not using delayed SACK may be considered.



3.4 Bundling considerations

    Bundling small telephony signalling messages at transmission helps
    improve the bandwidth usage efficiency of the network. On the
    downside, bundling may introduce additional delay to some of the
    messages. This should be taken into consideration when end-to-end
    delay is a concern.



3.5 Stream Usage

    Telephony signalling traffic is often composed of multiple,
    independent message sequences. It is highly desirable to transfer
    those independent message sequences in separate SCTP streams. This
    reduces the probability of head-of-line blocking in which the
    retransmission of a lost message affects the delivery of other
    messages not belonging to the same message sequence.



4 User Adaptation Layers



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    Users Adaptation Layers are defined to substitute the telephony
    signaling protocol that is below of the telephony signaling protocol
    to be relayed.

    There are UALs for both access signaling (DSS1) and trunk signaling
    (SS7). A brief description of the standardized UALs follows in the
    next sub-sections.

    The delivery mechanism in the several UALs

       - Support seamless operation of UALs user peers over an IP network
          connection.

       - Support the interface boundary that the UAL user had with the
          traditional lower layer.

       - Support management of SCTP transport associations and traffic
          between SGs and ISEPs or two ISEPs

       - Support asynchronous reporting of status changes to management.


    Two main scenarios have been developed for Signaling Transport:

    - Intercommunication of traditional Signaling transport nodes and IP
    based nodes.


                       Traditional               Telephony
                        Telephony                Signaling
              *******   Signaling    **********   over IP    ********
              * SEP *----------------*   SG   *--------------* ISEP *
              *******                **********              ********

              +-----+                                        +------+
              | SP  |                                        |  SP  |
              +-----+                +----+----+             +------+
              |     |                |    |UAL |             |  UAL |
              |     |                |    +----+             +------+
              |TTST |                |TTST|SCTP|             | SCTP |
              |     |                |    +----+             +------+
              |     |                |    | IP |             |  IP  |
              +-----+                +---------+             +------+

                  SEP:  Signaling Endpoint
                  SG:   Signaling Gateway
                  ISEP: IP Signaling Endpoint
                  SP:   Signaling Protocol
                  TTST: Traditional Telephony Signaling Transport
                  UAL:  User Adaptation Layer
                  SCTP: Stream Control Transport Protocol




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    It is also referred as SG to AS communication. AS I the name that
    UAL usually gives to the ISEP nodes. It stands for Application
    Server.


    - Communication inside the IP networks.


                                      Telephony
                                      Signaling
                          ********     over IP      ********
                          * ISEP *------------------* ISEP *
                          ********                  ********

                          +------+                  +------+
                          |  SP  |                  |  SP  |
                          +------+                  +------+
                          |  UAL |                  | UAL  |
                          +------+                  +------+
                          | SCTP |                  | SCTP |
                          +------+                  +------+
                          |  IP  |                  |  IP  |
                          +------+                  +------+


    It is also referred as IPSP communication. IPSP is the name of the
    role that an IP-based node plays UAL usually gives to the ISEP
    nodes. It stands for IP Signaling Point.



4.1  IUA (ISDN Q.921 User Adaptation)


    This document supports both ISDN Primary Rate Access (PRA) as well as
    Basic Rate Access (BRA) including the support for both point-to-point
    and point-to-multipoint modes of communication.  This support
    includes Facility Associated Signaling (FAS), Non-Facility Associated
    Signaling (NFAS) and NFAS with backup D channel.

    It implements the client/server architecture. The default orientation
    would be for the SG to take on the role of server while the ISEP is
    the client. The SCTP (and UDP/TCP) Registered User Port Number
    Assignment for IUA is 9900.

    Examples of the upper layers to be transported would be Q.931 and
    QSIG.

    The main scenario supported by this UAL is the SG to ISEP
    communication where the ISEP role is typically played by a node
    called MGC defined in [RFC2719].



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                ******   ISDN        ******      IP      *******
                * EP *---------------* SG *--------------* MGC *
                ******               ******              *******

                +-----+                                  +-----+
                |Q.931|              (NIF)               |Q.931|
                +-----+           +----------+           +-----+
                |     |           |     | IUA|           | IUA |
                |     |           |     +----+           +-----+
                |Q.921|           |Q.921|SCTP|           |SCTP |
                |     |           |     +----+           +-----+
                |     |           |     | IP |           | IP  |
                +-----+           +-----+----+           +-----+

                NIF  - Nodal Interworking Function
                EP   - ISDN End Point
                SCTP - Stream Control Transmission Protocol
                IUA  - ISDN User Adaptation Layer Protocol


    The SCTP (and UDP/TCP) Registered User Port Number Assignment for IUA
    is 9900.

    The value assigned by IANA for the Payload Protocol Identifier in the
    SCTP Payload Data chunk is ô1ö



4.2  V5UA (V5.2-User Adaptation) Layer

    It is an extension from the IUA layer with the modifications needed
    to support the differences between Q.921 / Q.931, and V5.2 layer 2 /
    layer 3. It supports analog telephone access, ISDN basic rate access
    and ISDN primary rate access over a V5.2 interface. It is basically
    implemented in an interworking scenario with SG.


            ******   V5.2        ******      IP      *******
            * AN *---------------* SG *--------------* MGC *
            ******               ******              *******


            +-----+                                  +-----+
            |V5.2 |              (NIF)               |V5.2 |
            +-----+           +----------+           +-----+
            |     |           |     |V5UA|           |V5UA |
            |     |           |     +----+           +-----+
            |LAPV5|           |LAPV5|SCTP|           |SCTP |
            |     |           |     +----+           +-----+
            |     |           |     | IP +           | IP  |
            +-----+           +-----+----+           +-----+



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            AN    û Access Network
            NIF   û Nodal Interworking Function
            LAPV5 û Link Access Protocol for the V5 channel
            SCTP  - Stream Control Transmission Protocol


    The SCTP (and UDP/TCP) Registered User Port Number Assignment for
    V5UA is 5675.

    The value assigned by IANA for the Payload Protocol Identifier in the
    SCTP Payload Data chunk is ô6ö



4.3  DUA (DPNSS/DASS 2 User Adaptation) Layer


    The DUA is built on top of IUA defining the necessary extensions to
    IUA for a DPNSS/DASS2 transport. DPNSS stands for Digital Private
    Network Signaling System and DASS2 for Digital Access Signaling
    System No 2


               ******   DPNSS       ******      IP      *******
               *PBX *---------------* SG *--------------* MGC *
               ******               ******              *******

               +-----+                                  +-----+
               |DPNSS|              (NIF)               |DPNSS|
               | L3  |                                  | L3  |
               +-----+           +----------+           +-----+
               |     |           |     | DUA|           | DUA |
               |DPNSS|           |DPNSS+----+           +-----+
               | L2  |           | L2  |SCTP|           |SCTP |
               |     |           |     +----+           +-----+
               |     |           |     | IP +           | IP  |
               +-----+           +-----+----+           +-----+


          PBX  - Private Branch eXchange
          NIF  - Nodal Interworking function
          SCTP - Stream Control Transmission Protocol
          DUA  - DPNSS User Adaptation Layer Protocol

    The value assigned by IANA for the Payload Protocol Identifier in the
    SCTP Payload Data chunk is ôTBDö.



4.4  M2UA (SS7 MTP2 User Adaptation) Layer

    This protocol would be mainly used between a Signaling Gateway (SG)

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    and Media Gateway Controler (MGC). The SG will terminate up to MTP
    Level 2 and the MGC will terminate MTP Level 3 and above.  In other
    words, the SG will transport MTP Level 3 messages over an IP network
    to a MGC.

    The only SS7 MTP2 User is MTP3 that is the protocol transported by
    this UAL.

    The SG provides a interworking of transport functions with the IP
    transport, in order to transfer the MTP2-User signaling messages to
    and from an Application Server (e.g. MGC) where the peer MTP2-
    User protocol layer exists.



        ******    SS7    ******      IP     *******
        *SEP *-----------* SG *-------------* MGC *
        ******           ******             *******

        +----+                              +----+
        |S7UP|                              |S7UP|
        +----+                              +----+
        |MTP +                              |MTP |
        | L3 |            (NIF)             |L3  |
        +----+         +----+----+          +----+
        |MTP |         |MTP |M2UA|          |M2UA|
        |    |         |    +----+          +----+
        | L2 |         | L2 |SCTP|          |SCTP|
        | L1 |         | L1 +----+          +----+
        |    |         |    |IP  |          |IP  |
        +----+         +---------+          +----+


        MGC  - Media Gateway Controler
        SG   - Signaling Gateway
        SEP  - SS7 Signaling Endpoint
        NIF  - Nodal Interworking Function
        IP   - Internet Protocol
        SCTP - Stream Control Transmission Protocol


    The SCTP (and UDP/TCP) Registered User Port Number Assignment for
    M2UA is 2904.

    The value assigned by IANA for the Payload Protocol Identifier in the
    SCTP Payload Data chunk is ô2ö



4.5  M2PA (SS7 MTP2-User Peer-to-Peer Adaptation) Layer

    This protocol is used between SS7 Signaling Points employing the MTP
    Level 3 protocol. The SS7 Signaling Points may also employ standard
    SS7 links using the SS7 MTP Layer 2 to provide transport of MTP Layer

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    3 signaling messages.

    Both configurations: intercommunication of SS7 and IP with SG and
    communication between ISEPs are possible.


                ********   IP   ********
                * IPSP *--------* IPSP *
                ********        ********

                +------+        +------+
                | TCAP |        | TCAP |
                +------+        +------+
                | SCCP |        | SCCP |
                +------+        +------+
                | MTP3 |        | MTP3 |
                +------+        +------+
                | M2PA |        | M2PA |
                +------+        +------+
                | SCTP |        | SCTP |
                +------+        +------+
                | IP   |        | IP   |
                +------+        +------+

                IP    - Internet Protocol
                IPSP  - IP Signaling Point
                SCTP  - Stream Control Transmission Protocol





        ********  SS7   ***************   IP   ********
        * SEP  *--------*     SG      *--------* IPSP *
        ********        ***************        ********

        +------+                               +------+
        | TCAP |                               | TCAP |
        +------+                               +------+
        | SCCP |                               | SCCP |
        +------+        +-------------+        +------+
        | MTP3 |        |    MTP3     |        | MTP3 |
        +------+        +------+------+        +------+
        | MTP2 |        | MTP2 | M2PA |        | M2PA |
        +------+        +------+------+        +------+
        | MTP1 |        | MTP1 | SCTP |        | SCTP |
        |      |        |      +------+        +------+
        |      |        |      | IP   |        | IP   |
        +------+        +------+------+        +------+

        SEP   - SS7 Signaling Endpoint




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    These figures are only an example. Other configurations are possible.
    For example, IPSPs without traditional SS7 links could use the
    protocol layers MTP3/M2PA/SCTP/IP to route SS7 messages in a network
    with all IP links.

    Another example is that two SGs could be connected over an IP network
    to form an SG mated pair similar to the way STPs are provisioned in
    traditional SS7 networks.

    The SCTP (and UDP/TCP) Registered User Port Number Assignment for
    M2PA is TBD.

    The value assigned by IANA for the Payload Protocol Identifier in the
    SCTP Payload Data chunk is TBD




    Differences between M2PA and M2UA include:

       a. M2PA: IPSP processes MTP3/MTP2 primitives.
          M2UA: MGC transports MTP3/MTP2 primitives between the SG's MTP2
                and the MGC's MTP3 (via the NIF) for processing.

       b. M2PA: SG-IPSP connection is 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.
          M2UA: SG is not an SS7 node and has no point code.

       d. M2PA: SG can have upper SS7 layers, e.g., SCCP.
          M2UA: SG does not have upper SS7 layers since it has no MTP3.

       e. M2PA: relies on MTP3 for management procedures.
          M2UA: uses M2UA management procedures.




4.6  M3UA (SS7 MTP3 User Adaptation) Layer


    This adaptation layer supports the transport of any SS7 MTP3-User
    signaling such as TUP, ISUP and SCCP over IP using the services of
    SCTP.

    This protocol allows both:
       - Interconnection of SS7 and IP nodes
       - Communication between two IP nodes





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      ********   SS7   *****************   IP   ********
      * SEP  *---------*      SGP      *--------* ASP  *
      ********         *****************        ********

      +------+         +---------------+        +------+
      | ISUP |         |     (NIF)     |        | ISUP |
      +------+         +------+ +------+        +------+
      | MTP3 |         | MTP3 | | M3UA |        | M3UA |
      +------|         +------+-+------+        +------+
      | MTP2 |         | MTP2 | | SCTP |        | SCTP |
      +------+         +------+ +------+        +------+
      |  L1  |         |  L1  | |  IP  |        |  IP  |
      +------+         +------+ +------+        +------+

        SEP - SS7 Signaling End Point
        SCTP - Stream Control Transmission Protocol
        NIF - Nodal Interworking Function



            ********    IP    ********
            * IPSP *----------* IPSP *
            ********          ********

            +------+          +------+
            |SCCP- |          |SCCP- |
            | User |          | User |
            +------+          +------+
            | SCCP |          | SCCP |
            +------+          +------+
            | M3UA |          | M3UA |
            +------+          +------+
            | SCTP |          | SCTP |
            +------+          +------+
            |  IP  |          |  IP  |
            +------+          +------+

    It works using the client-server philosophy. ISEP is recommended to
    be client when talking with a SG. The reserved port by IANA is 2905
    to listen to possible client connections.

    The assigned payload protocol identifier for the SCTP DATA chunks is
    ô3ö.



4.7  SUA (SS7 SCCP User Adaptation) Layer


    This adaptation layer supports the transport of any SS7 SCCP-User
    signaling such as MAP, INAP, SMS, BSSAP, RANAP over IP using the
    services of SCTP. SUA can support only non-call related signaling.


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    SUA does not pose stringent timing constraints on SCTP due to the
    fact that SUA applications have broad timing requirement (from 10 of
    seconds to hours) which the applications guard themselves and the
    timing supervision of the application is end-to-end, not hop-by-
    hop(as with ISUP).


    Possible configurations showed in the pictures below:

       - Interconnection of SS7 and IP
       - IP Node to IP Node communication



            ********   SS7   ***************   IP   ********
            * SEP  *---------*             *--------*      *
            *  or  *         *      SG     *        * ASP  *
            * STP  *         *             *        *      *
            ********         ***************        ********

            +------                                 +------+
            | SUAP |                                | SUAP |
            +------+         +------+------+        +------+
            | SCCP |         | SCCP | SUA  |        | SUA  |
            +------+         +------+------+        +------+
            | MTP3 |         | MTP3 |      |        |      |
            +------+         +------+ SCTP |        | SCTP |
            | MTP2 |         | MTP2 |      |        |      |
            +------+         +------+------+        +------+
            |  L1  |         |  L1  |  IP  |        |  IP  |
            +------+         +------+------+        +------+

              SUAP - SCCP/SUA User Protocol (TCAP, for example)
              STP  - SS7 Signaling Transfer Point




                  ********   IP   ********
                  *      *--------*      *
                  * IPSP *        * IPSP *
                  *      *        *      *
                  ********        ********

                  +------+        +------+
                  | SUAP |        | SUAP |
                  +------+        +------+
                  | SUA  |        | SUA  |
                  +------+        +------+
                  | SCTP |        | SCTP |
                  +------+        +------+
                  |  IP  |        |  IP  |
                  +------+        +------+


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    IANA has registered SCTP Port Number 14001 for SUA.  It is
    recommended that SGs use this SCTP port number for listening for new
    connections. The payload protocol identifier for the SCTP DATA chunks
    is ô4ö.






5 Security considerations


    UALs are designated to carry signaling messages for telephony
    services. As such, UALs must involve the security needs of several
    parties: the end users of the services; the network providers and
    the applications involved.  Additional requirements may come from
    local regulation.  While having some overlapping security needs, any
    security solution should fulfill all of the different parties'
    needs.  See specific Security considerations in each UAL technical
    specification.

    SCTP only tries to increase the availability of a network. SCTP does
    not contain any protocol mechanisms which are directly related to
    user message authentication, integrity and confidentiality
    functions. For such features, it depends on the IPSEC protocols and
    architecture and/or on security features of its user protocols.

    Mechanisms for reducing the risk of blind denial-of-service attacks
    and masquerade attacks are built into SCTP protocol. See RFC2960,
    section 11 for detailed information.

    Currently the IPSEC working group is investigating the support of
    multihoming by IPSEC protocols. At the present time to use IPSEC,
    one must use 2 * N * M security associations if one endpoint uses N
    addresses and the other M addresses.



6 References and related work


    [RFC2960] Stewart, R. R., Xie, Q., Morneault, K., Sharp, C. , ,
    Schwarzbauer, H. J., Taylor, T., Rytina, I., Kalla, M., Zhang,
    L. and Paxson, V, "Stream Control Transmission Protocol", RFC2960,
    October 2000.


    [RFCOENE] Coene, L., Tuexen, M., Verwimp, G., Loughney, J., Stewart,
    R.  R., Xie, Q., Holdrege, M., Belinchon, M.C., and Jungmayer, A.,
    "Stream Control Transmission Protocol Applicability statement",
    <draft-ietf-sigtran-sctp-applicability-03.txt>, December 2000. Work

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    In Progress.


    [RFC2719] Ong, L., Rytina, I., Garcia, M., Schwarzbauer, H., Coene,
    L., Lin, H., Juhasz, I., Holdrege, M., Sharp, C., "Framework
    Architecture for Signalling Transport", RFC2719, October 1999


    [SCTPFLOW] Stewart, R., Ramalho, M., Xie, Q., Conrad, P. and Rose,
    M., "SCTP Stream based flow control", September 2000, Work in
    Progress.


    [ALLMAN99] Allman, M. and Paxson, V., "On Estimating End-to-End
    Network Path Properties", Proc. SIGCOMM'99, 1999.



7 Acknowledgments

    This document was initially developed by a design team consisting of
    Lode Coene, John Loughney, Michel Tuexen, Randall R. Stewart,
    Qiaobing Xie, Matt Holdrege, Maria-Carmen Belinchon, Andreas
    Jungmaier, Gery Verwimp and Lyndon Ong.


    The authors wish to thank Renee Revis, H.J. Schwarzbauer, T. Taylor,
    G.  Sidebottom, K. Morneault, T. George, M. Stillman and many others
    for their invaluable comments.



8 Author's Address


Lode Coene                  Phone: +32-14-252081
Siemens Atea                EMail: lode.coene@siemens.atea.be
Atealaan 34
B-2200    Herentals
Belgium

Javier Pastor-Balbas        Phone:
Ericsson                    Email: javier.pastor-balbas@ece.ericsson.se


Spain






Expires: August 2002


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