Đang chuẩn bị nút TẢI XUỐNG, xin hãy chờ
Tải xuống
Signaling Message Handling MTP3 processes all incoming MSUs to determine whether they should be sent to one of the MTP3 users or routed to another destination. The term "MTP3 user" refers to any user of MTP3 services, as indicated by the Service Indicator in the SIO. This includes messages generated by MTP3 itself, such as SNM | Signaling Message Handling MTP3 processes all incoming MSUs to determine whether they should be sent to one of the MTP3 users or routed to another destination. The term MTP3 user refers to any user of MTP3 services as indicated by the Service Indicator in the SIO. This includes messages generated by MTP3 itself such as SNM or those that are passed down from the User Parts at level 4 of the SS7 protocol like ISUP and SCCP. The term MTP User Part is also used but more specifically refers to the User Parts at level 4. When a node generates an MSU MTP3 is responsible for determining how to route the message toward its destination using the DPC in the Routing Label and the Network Indicator in the SIO. Figure 7-8 shows how MTP3 message processing can be divided into three discrete functions discrimination distribution and routing. Figure 7-8. Signaling Message Handling View full size image Discrimination Message discrimination is the task of determining whether an incoming message is destined for the node that is currently processing the message. Message discrimination makes this determination using both the NI and the DPC. Each node s Point Code is defined as belonging to a particular network type. The network types are those that are specified by the NI discussed earlier in this chapter. An ISC will have both a National network and International type with Point Codes in each. Nodes that do not function as an ISC are generally identified as a National network with a single Point Code. In some cases multiple Point Codes can identify a national node for example a network operator might use both National and National Spare network types at a network node with Point Codes in each network. The NI in an incoming message s SIO is examined to determine the network type for which the message is destined. Each time a node receives a message it must ask Is it for me The node asks the question by comparing the incoming DPC in the Routing Label to its own Point Code. If the Point .
