Signalling modes

Associated Mode
In the associated mode, the signalling messages for a relation between two nodes
are conveyed over a link directly connecting those nodes.

Quasi-Associated Mode
In this mode a predetermined path is taken by signalling messages. This path transits
an STP and does not directly connect the origin and destination nodes.
The STP functionality (quasi-associated mode of signalling) offers scalability,
resilience and, more importantly for operators, reduced connectivity cost in respect of
the signalling network. The associated mode of signalling may be used by directly
connected SPs.
In the example the Base Station Controller (BSC) is directly connected to the MSC
and uses an associated mode of signalling, whereas the Network Switching System
(NSS) is using the quasi-associated mode of signalling between databases, indirectly
connected by STPs.