In this section:
In the following network configuration (see the following figure)
Typically, in this scenario, nodes C and D behave as STPs. If A is required to send a message signaling unit (MSU) to B, this MSU would be sent through C or D and it would be routed using standard MTP Level 3 routing procedures.
Routing MSUs Using MTP Level 3 Routing Procedures
Enabling the traffic flow shown in the following figure with traditional MTP3 routing (based on DPC only) is not possible for the following reasons:
Forcing MSUs Through Core STP E
The routing on incoming linkset feature is license-dependent. For information about license availability and pricing, contact your Sales Representative
To allow the traffic flows presented in the preceding illustrations, the allows routing of messages not only on the DPC, as defined in SS7 standards, but also on a per incoming linkset basis.
In this case, when routing traffic is destined to B, nodes C and D must route messages originating from A through E or F. However, traffic originating from F destined to B is routed directly to B. To obtain this traffic pattern, the operator must provision two routeset lists that are assigned directionally (see the following figure)
Routing on Incoming Linkset (RTIL)
When the Edge devices are configured with appropriate routing tables, the core STPs must also allow the appropriate traffic flow.
For STPs that use standard SS7 routing, one solution is to provision routes asymmetrically.
Using this method, the links between C, D, E, and F carry unidirectional traffic. E receives traffic from C, but sends traffic to D (see the following figure).
Asymmetric Routing Example