ss7box Redundancy Explained

Two ss7box are better than one as is usually the case in SS7 networking. If one fails or needs to be worked on, the other carries the load and there's no interruption in operations. The next question is, "How will that work?"

The first thing that's needed is a two-link linkset as shown in Figure 1 below. The links need to be in two separate E1/T1 spans. Each span is connected to Sangoma wanpipe port on a separate Linux box. Each Linux box is running an instance of ss7box. This is the F-Link setup most often found in ITU networks.

Figure 1

In Figure 2 the left hand SSP from Figure 1 is shown as an Sangoma SMG implementation using redundant ss7box. ss7box and SMG communicate using SCTP/IP. SMG communicates with Asterisk using TCP/IP and UDP/IP. SMG can receive from either ss7box at any time. SMG sends to the pair of ss7box using a load balancing scheme. If one of the links to an ss7box is lost, or if an ss7box is lost or is under maintenance, then the full signaling load is handled by the remaining ss7box. When the second ss7box returns to service, load is automatically balanced between both ss7box.

Figure 2

ANSI networks and some ITU networks use redundant signal transfer points (STPs) to interconnect signaling terminations like signal switching points (SSPs) as shown in Figure 3. In this type of network there will be a combined linkset between an SSP and a mated pair of STPs. A combined linkset, in its simplest form, is a pair of single-link linksets. The SSP connects to both linksets. Each STP in the mated pair connects to one of the two linksets. The same rules

Figure 3

In Figure 4 the SSP from Figure 3 is shown as an Sangoma SMG implementation. The same rules regarding load balance, fail-over, and fail-back listed for the F-link configuration above also apply to this A-link (or combined linkset) configuration.

Figure 4