tailieunhanh - Signaling System No.7 Protocol Architecture And Sevices part 57

MTP Level 2 User Adaptation (M2UA) The M2UA protocol defines the layer split between MTP Level 2 and MTP Level 3. M2UA is defined by RFC 3331 [140]. The M2UA protocol can be used between a SG, which is called | MTP Level 2 User Adaptation M2UA The M2UA protocol defines the layer split between MTP Level 2 and MTP Level 3. M2UA is defined by RFC 3331 140 . The M2UA protocol can be used between a SG which is called a Signaling Link Terminal SLT and an MGC. The SG would terminate standard SS7 links using MTP Level 1 and MTP Level 2 to provide reliable transport of MTP Level 3 messages to the SEP or STP. The SG also provides reliable transfer of MTP Level 2 primitives over IP using SCTP as the transport protocol. Figure 14-18 shows an example of an SG to the MGC application of M2UA. The SEP is a SEP in the SS7 network. Just as it does for M3UA NIF stands for Nodal Interworking Function. It is the software in the SG that provides the SS7 to IP network interworking. Figure 14-18. Example of M2UA Between SG and MGC Although not discussed M2UA can be used between two SGs but not in a peer-to-peer arrangement. One SG would terminate the SS7 links and backhaul the MTP Level 3 messages to the other SG which would terminate MTP Level 3. As noted the M2UA layer supports the MTP Level 2 to MTP Level 3 primitive boundary including support for link alignment message retrieval during link changeover remote and local processor outage and link congestion notifications. Messages and Formats M2UA uses the common header and TLV format for parameters that were defined in the M3UA section. In addition M2UA introduces an M2UA specific header that is required because an Application Server can support more than one Interface Identifier. Figure 14-19 shows the M2UA specific header which is placed between the common message header and message-specific parameters. Note that it follows the TLV format. The Interface Identifier can be an integer-based or text-based ASCII value. If it is integer-based the length is always equal to eight. If it is text-based the length is based on the length of the ASCII string up to a maximum of 255 octets. Figure 14-19. M2UA Specific Message Header Table 14-3 lists the .