MEGACO - CALEA - Topology descriptor

SPLIT-IN CALEA
SPLIT-OUT CALEA
MIXED CALEA



7.1.18 Topology descriptor (From RFC 3525 Gateway Control Protocol Version 1)
A Topology descriptor is used to specify flow directions between Terminations in a Context. Contrary to the descriptors in previous subclauses, the Topology descriptor applies to a Context instead of a Termination. The default topology of a Context is that each Termination's transmission is received by all other Terminations. The Topology descriptor is optional to implement. An MG that does not support Topology descriptors, but receives a command containing one, returns Error 444 Unsupported or unknown descriptor, and optionally includes a string containing the name of the unsupported Descriptor ("Topology") in the error text in the error descriptor.

The Topology descriptor occurs before the commands in an action. It is possible to have an action containing only a Topology descriptor, provided that the Context to which the action applies already exists.

A Topology descriptor consists of a sequence of triples of the form (T1, T2, association). T1 and T2 specify Terminations within the Context, possibly using the ALL or CHOOSE wildcard. The association specifies how media flows between these two Terminations as follows.

- (T1, T2, isolate) means that the Terminations matching T2 do not receive media from the Terminations matching T1, nor vice versa.

- (T1, T2, oneway) means that the Terminations that match T2 receive media from the Terminations matching T1, but not vice versa. In this case use of the ALL wildcard such that there are Terminations that match both T1 and T2 is not allowed.

- (T1, T2, bothway) means that the Terminations matching T2 receive media from the Terminations matching T1, and vice versa. In this case it is allowed to use wildcards such that there are Terminations that match both T1 and T2. However, if there is a Termination that matches both, no loopback is introduced.