rfc2719.txt

中、英文RFC文档大全打包下载完全版 .

Ong, et al.                  Informational                      [Page 6]

RFC 2719     Framework Architecture for Signaling Transport October 1999


   For interworking with SS7-controlled SCN networks, the SG terminates
   the SS7 link and transfers the signaling information to the MGC using
   signaling transport.  The MG terminates the interswitch trunk and
   controls the trunk based on the control signaling it receives from
   the MGC. As shown below in case (a), the SG, MGC and MG may be
   implemented in separate physical units, or as in case (b), the MGC
   and MG may be implemented in a single physical unit.

   In alternative case (c), a facility-associated SS7 link is terminated
   by the same device (i.e., the MGU) that terminates the interswitch
   trunk. In this case, the SG function is co-located with the MG
   function, as shown below, and signaling transport is used to
   "backhaul" control signaling to the MGCU.

   Note: SS7 links may also be terminated directly on the MGCU by
   cross-connecting at the physical level before or at the MGU.

            SGU
           +--------+
   SS7<------>[SG]  |
   (ISUP)  |   |    |
           +---|----+
            ST |                SGU                       MGCU
           +---|----+           +--------+                +--------+
           | [MGC]  |      SS7---->[SG]  |                | [MGC]  |
           |   |    |           |   |    |                |  | |   |
           +---|----+           +---|----+                +--|-|---+
          MGCU |                 ST |                        | |
               |                    |                     ST | |
     Media +---|----+     Media +---|----+                +--|-|---+
      ------->[MG]  |      ----->[MG/MGC]|      SS7 link-->[SG]|   |
    stream |        |    stream |        |       Media------> [MG] |
           +--------+           +--------+       stream   +--------+
           MGU                  MGU                       MGU

            (a)                     (b)                      (c)

   Notes: ST = Signaling Transport used to carry SCN signaling

                     Figure 2: Example Implementations











Ong, et al.                  Informational                      [Page 7]

RFC 2719     Framework Architecture for Signaling Transport October 1999


   In some implementations, the function of the SG may be divided into
   multiple physical entities to support scaling, signaling network
   management and addressing concerns.  Thus, Signaling Transport can be
   used between SGs as well as from SG to MGC. This is shown in Figure 3
   below.

               SGU                                 MGCU
             +---------+                         +---------+
             |         |          ST             |         |
             |  [SG2]------------------------------>[MGC]  |
             |   ^ ^   |                         |         |
             +---|-|---+                         +---------+
                 | |
                 | |             ST
               ST| +--------------------------------+
                 |                                  |
                 |                                  |
        SS7  +---|----------+             SS7  +----|---------+
   -----------> [SG1]       |        -----------> [SG1]       |
    media    |              |         media    |              |
   ------------------->[MG] |        ------------------->[MG] |
    stream   +--------------+         stream   +--------------+
              MGU                                MGU


                        Figure 3: Multiple SG Case

   In this configuration, there may be more than one MGU handling
   facility associated signaling (i.e. more than one containing it's own
   SG function), and only a single SGU. It will therefore be possible to
   transport one SS7 layer between SG1 and SG2, and another SS7 layer
   between SG2 and MGC. For example, SG1 could transport MTP3 to SG2,
   and SG2 could transport ISUP to MGC.

2.3  ISDN Interworking for Connection Control

   In ISDN access signaling, the signaling channel is carried along with
   data channels, so that the SG function for handling Q.931 signaling
   is co-located with the MG function for handling the data stream.
   Where Q.931 is then transported to the MGC for call processing,
   signaling transport would be used between the SG function and MGC.
   This is shown in Figure 3 below.









Ong, et al.                  Informational                      [Page 8]

RFC 2719     Framework Architecture for Signaling Transport October 1999


                             MGCU
                             +-------------+
                             |    [MGC]    |
                             |     | |     |
                             +-----|-|-----+
                                   | |
                                   | O device control
                                   | |
                          Q.931/ST O |
                                   | |
                             +-----|-|-----+
                             |     | |     |
                       Q.931---->[SG]|     |
                      signals|       |     |
                             |       |     |
                    Media---->[MG]   |
                    stream   |             |
                             +-------------+
                             MGU


                   Figure 4: Q.931 transport model

2.4  Architecture for Database Access

   Transaction Capabilities (TCAP) is the application part within SS7
   that is used for non-circuit-related signaling.

   TCAP signaling within IP networks may be used for cross-access
   between entities in the SS7 domain and the IP domain, such as, for
   example:

   -  access from an SS7 network to a Service Control Point (SCP) in IP.
   -  access from an SS7 network to an MGC.
   -  access from an MGC to an SS7 network element.
   -  access from an IP SCP to an SS7 network element.

   A basic functional model for TCAP over IP is shown in Figure 5.













Ong, et al.                  Informational                      [Page 9]

RFC 2719     Framework Architecture for Signaling Transport October 1999


                            +--------------+
                            | IP SCP       |
                            +--|----|------+
                               |    |
            SGU                |    |                SGU
           +--------------+    |    |    +--------------+
           |              |    |    |    |              |
   SS7<--------->[SG] ---------+    |    |     [SG]<---------> SS7
   (TCAP)  |      |       |         |    |      |       |
           +------|-------+         |    +------|-------+
                  |                 |           |
                  O    +------------+           O
          MGCU    |    |                        | MGCU
          +-------|----|--+               +-----|--------+
          |       |    |  |               |     |        |
          |      [MGC]    |               |    [MGC]     |
          |       |       |               |     |        |
          +-------|-------+               +-----|--------+
                  |                             |
          +-------|-------+               +-----|------+
    Media |       |       |               |     |      | Media
   <------+---->[MG]  <---+--RTP stream---+--> [MG]  <-+-------->
    stream|               |               |            | stream
          +---------------+               +------------+
          MGU                             MGU


                     Figure 5: TCAP Signaling over IP

3. Protocol Architecture

   This section provides a series of examples of protocol architecture
   for the use of Signaling Transport (SIG).

3.1 Signaling Transport Components

   Signaling Transport in the protocol architecture figures below is
   assumed to consist of three components (see Figure 6):

   1) an adaptation sub-layer that supports specific primitives, e.g.,
      management indications, required by a particular SCN signaling
      application protocol.
   2) a Common Signaling Transport Protocol that supports a common set
      of reliable transport functions for signaling transport.
   3) a standard, unmodified IP transport protocol.






Ong, et al.                  Informational                     [Page 10]

RFC 2719     Framework Architecture for Signaling Transport October 1999


                 +-- +--------------------------------+
                 |   |      SCN adaptation module     |
                 |   +--------------------------------+
                 |                  |
               S |   +--------------------------------+
               I |   | Common Signaling Transport     |
               G |   +--------------------------------+
                 |                  |
                 |   +--------------------------------+
                 |   |     standard IP transport      |
                 +-- +--------------------------------+


                Figure 6: Signaling Transport Components

3.2. SS7 access for Media Gateway Control

   This section provides a protocol architecture for signaling transport
   supporting SS7 access for Media Gateway Control.

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

          +----+                                       +-----+
          |ISUP|                                       | ISUP|
          +----+        +-----+      +---------+       +-----+
          |MTP |        |MTP  |      |MTP | SIG|       | SIG |
          |L1-3|        |L1-3 |      |L1-3+----+       +-----+
          |    |        |     |      |    | IP |       | IP  |
          +----+        +-----+      +---------+       +-----+


          STP - Signal Transfer Point    SEP - Signaling End Point
          SG - Signaling Gateway         SIG - Signaling Transport
          MGC - Media Gateway Controller


                      Figure 7: SS7 Access to MGC












Ong, et al.                  Informational                     [Page 11]

RFC 2719     Framework Architecture for Signaling Transport October 1999


3.3. Q.931 Access to MGC

   This section provides a protocol architecture for signaling transport
   supporting ISDN point-to-point access (Q.931) for Media Gateway
   Control.

            ******    ISDN      *********     IP     *******
            * EP *--------------* SG/MG *------------* MGC *
            ******              *********            *******

            +----+                                   +-----+
            |Q931|                                   | Q931|
            +----+              +---------+          +-----+
            |Q921|              |Q921| SIG|          | SIG |
            +    +              +    +----+          +-----+
            |    |              |    | IP |          | IP  |
            +----+              +---------+          +-----+

            MG/SG - Media Gateway with SG function for backhaul
            EP - ISDN End Point


                         Figure 8: ISDN Access

3.4. SS7 Access to IP/SCP

   This section provides a protocol architecture for database access,
   for example providing signaling between two IN nodes or two mobile
   network nodes. There are a number of scenarios for the protocol
   stacks and the functionality contained in the SIG, depending on the
   SS7 application.

   In the diagrams, SS7 Application Part (S7AP) is used for generality
   to cover all Application Parts (e.g. MAP, IS-41, INAP, etc).
   Depending on the protocol being transported, S7AP may or may not
   include TCAP. The interface to the SS7 layer below S7AP can be either
   the TC-user interface or the SCCP-user interface.

   Figure 9a shows the scenario where SCCP is the signaling protocol
   being transported between the SG and an IP Signaling Endpoint (ISEP),
   that is, an IP destination supporting some SS7 application protocols.










Ong, et al.                  Informational                     [Page 12]