Intel SIU520 SS7 manual Connection to an Adjacent Mated STP Pair

Application Note Building Fault-tolerant SS7 Systems Using the Intel® NetStructure™ SIU520 SS7 Signaling Gateway

Single Point Code

Link Set id 1

Inter-SIU

Link Set

SIUA

Link Set id 0

A-Links

SIUB

Link Set id 2

STPA

SSP/SCP

STPB

Figure 7. Dual-resilient SIUs Connected to a Mated STP Pair in a Straight Link Configuration

Single Point Code

Link Set id 1

Inter-SIU

Link Set

SIUA

Link Set id 0

SIUB

STPA

SSP/SCP

STPB

Link Set id 2

Figure 8. Dual-resilient SIUs Connected to a Mated STP Pair in a Crossed Link Configuration

In case (A), since the F-links all exist in the same link set, messages may be sent from the adjacent SSP/SCP to either SIUA or SIUB. If an SIU receives a message from the SS7 network for a circuit or transaction that it does not control, this receive message is passed automatically to the other SIU for processing via the TCP/IP LAN.

Connection to an Adjacent Mated STP Pair

There are two ways of connecting a pair of SIUs to a mated STP pair. In the first method, the straight link configuration, each SIU is configured with two link sets: one link set containing STP-facing links, plus the inter-SIU link set. The straight link configuration consists in connecting SIUA to STPA and SIUB to STPB, as shown in Figure 7.

The second method, the crossed link configuration, consists of adding crossed link connections between SIUA and STPB and between SIUB and STPA to the previous mode. In a crossed link configuration, each SIU

is configured with three linksets: two link sets containing the links towards each STP, plus the inter-SIU link set (see Figure 8). The configuration of the DPC will contain the link set IDs of the two link sets connected to the STPs. Load sharing can be enabled to take advantage of all the system resources. In such a configuration, the inter-SIU link set is not used for traffic failover, but only for synchronization of network management messages. Consequently, a single link within this link set is fairly enough, giving an increased bandwidth for network- facing links.

The inter-SIU link must be carefully dimensioned as it will have to support the outgoing traffic of the SIU that would have lost its entire network-facing links, as shown in Figure 9. Again, a common practice is to allocate a fourth of the total number of network-facing links in the inter- SIU link set.

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