Transit subs can be dynamically provisioned by RADIUS accounting start messages forwarded by the RADIUS AAA server to a RADIUS sub-manager function at the OSS layer. This RADIUS sub manager manages dynamic transit AA subscribers on the appropriate ISA and transit-ip-policy based on the RADIUS accounting information. The interface for the sub manager to configure transit AA subscribers is RADIUS CoA messages, which are acknowledged with a CoA success message to the sub manager.
If a dynamic transit sub cannot be created as requested by a CoA because of resource constraints or conflicts, the node replies to the sub manager with a CoA fail message so that retries do not continue. This message should contain information as to the cause of the rejection. Multiple IPs per sub are allowed when common sub-ID names are seen, but with differing IP hosts.
When a RADIUS update or CoA message is seen, it could contain a modified IP address or app-profile for an existing transit sub which is accepted without affecting transit AA subscriber statistics. These transit AA subscribers are removed by the sub manager when a RADIUS accounting stop message is received.
Figure: RADIUS COA example shows a RADIUS CoA Example.
The attributes in RADIUS COA that identify the downstream transit AA subscribers are:
downstream BRAS/ CMTS: NAS-port-ID
IP address (framed-ip-address)
subscriber ID (per RADIUS accounting sub-id-string)