MTP 3 task

The MTP 3 task has two primary functions:

Function

Description

Message routing and distribution

Routes outgoing messages to their specified destinations and distributes incoming messages to the appropriate application. NMS MTP 3 uses a flexible configuration capable of supporting a wide variety of network routing and addressing requirements.

Signaling network management

Reconfigures the signaling network as needed to maintain signaling capability in the case of failure or congestion. NMS MTP 3 redirects traffic away from failed links, signaling points (SPs), or both. It restores traffic to restored links and SPs, and exchanges route status with adjacent SPs.


MTP 3 entities

The MTP 3 layer consists of the following configurable entities:

Service access points (SAPs)

Service access points (SAPs) define the SS7 applications that use MTP 3. Each SAP is associated with one application, as identified by the service indicator field of a message, and one protocol variant.

The following illustration shows service access points (SAPs):

If multiple protocol variants are configured on the same MTP 3 instance (same board), two SAPs are required for each application: one for each protocol variant. In this case, a single application can associate itself with both SAPs for that service, or separate applications can be used for each protocol variant.

Signaling links

Signaling links define physical links between the TX board and the adjacent signaling points. One link configuration must be performed for each physical signaling link. The attributes of a link include the point code of the adjacent signaling point, protocol variant employed on the link, point code length, maximum packet length, various timer values, and membership in a linkset.

High speed links (HSL) meet the ANSI T1.111-1996 and Q.703/Annex A standards. Each HSL occupies a full (unchannelized) T1/E1 line and transfers data at the rate of 2.0 (1.544) Mbps. For information about configuring high speed links, refer to Mtp3InitLinkCfg.

Linksets

Linksets are groups of one to 16 links that directly connect two signaling points. Although a linkset usually contains all parallel signaling links between two SPs, you can define parallel linksets. Each signaling link is assigned membership in one linkset.

A combined linkset is a group of all linksets that can be used to reach a particular destination or group of destinations (routes). Each linkset can be associated with up to 16 combined linksets. Each linkset in a combined linkset can be assigned a priority relative to the other linksets belonging to that combined linkset.

Routes

Routes specify the destination signaling points (subnetworks or clusters) accessible from the target node. Each route is assigned a direction: up or down. One up route is required for the point code assigned to the signaling point being configured, and for each point code that is to be emulated. Up routes are used to identify incoming messages that are to be routed up to the applications or user parts. One down route is required for each remote signaling point, network, or cluster that is to be accessible from the SP being configured.

Down routes are used to route outgoing messages to the appropriate signaling links. Each down route is assigned to one combined linkset, which in turn identifies all linksets that can be used to reach that destination. Each linkset within the route's associated combined linkset can be assigned an optional priority, so that MTP routing chooses the highest priority available linkset when routing an outgoing packet to a particular destination. Any number of routes can be assigned to a combined linkset.

The following illustration shows the relationship between links, linksets, combined linksets, and routes: