Dialogic® SS7G2x Signaling Server SGW Mode User Manual Issue 4
7.6.2Dual Resilient Operation
Two Signaling Gateways have the ability to work in conjunction with one another to realize a single SS7 signaling point where the operation of the Message Transfer Part (MTP) is distributed. Failure (or planned maintenance) of one or other of the Signaling Gateways operating in “Dual Mode” therefore does not result in a loss of SS7 signaling capability.
The use of the dual functionality does introduce some restrictions that are described below. The user is responsible for ensuring that these restrictions are acceptable, otherwise the dual mode of operation may not be applicable.
7.6.2.1Overview of Dual Resilience
The dual Signaling Gateway solution assumes that each Signaling Gateway has one (or more) signaling links facing the network.
The ability for each of the Signaling Gateways to communicate with each other is addressed by adding an additional link set (containing one or two links, for example LS2 in Figure 11, “Dual Resilient Operation” on page 144) between the two platforms. This link set is used to convey network status and management messages between the two halves of the system and to pass signaling traffic as necessary.
On each Signaling Gateway, there is (a minimum of) two link sets, one connected to the adjacent signaling point and the other connected to the other half of the dual pair. Each MTP route is configured so that the primary link set is the link set connected to the adjacent signaling point and the secondary link set is the link set connected to the partner Signaling Gateway. Load sharing across these link sets is disabled.
The link set between the two halves of the dual Signaling Gateway is configured so that the originating and destination point codes are identical.
Under normal circumstances, messages that have been determined for the SS7 network are routed directly over the link set that connects to the adjacent signaling point. Under failure conditions, when the link to the adjacent signaling point is not available, the traffic messages are sent instead on the secondary link set to the partner Signaling Gateway. On receipt of these messages, the partner Signaling Gateway recognizes that the message is not destined for itself and transfers the message to its
The signaling that takes place between each half of the dual Signaling Gateway system makes use of two reserved Network Indicator values in the
The link set between the two halves of the dual pair now becomes a key element in the system and to avoid a single point of failure, this link set should contain at least two signaling links. Where possible, these links should be located on different signaling boards.
7.6.2.2Configuration
Each half of the dual configuration needs to be configured separately using existing configuration techniques and noting the following.
The additional link set between the two Signaling Gateways should have the local point code and the adjacent point code set to the same value.
Each route to a destination signaling point should be configured to use the network link set as the primary link set and the inter Signaling Gateway link set as the secondary link set. Load sharing must be disabled.
When connecting to a pair of adjacent STPs, each STP must have a route declared on each Signaling Gateway and in all cases the
A route must be configured to the other half of the dual Signaling Gateway system, this must use the inter- Signaling Gateway link set as the only link set.
In addition, the link set between the two halves of the dual Signaling Gateway system must be designated as a “special” link set. The method of achieving this depends on the equipment and configuration tools in use as follows:
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