On an incoming call, with RADIUS configured, the IMG will exchange the RADIUS Access-Request/Access-Accept messages with a configured RADIUS server. Within the Access-Request message among other info is the Called-Station-Id attribute. The Called-Station-Id attribute contains the Dialed Number in the incoming call. On a normal (enbloc) call where Overlap Signaling is disabled, the complete Dialed Number is sent to the RADIUS server within this message. With Overlap Signaling enabled, the Dialed Number is received in multiple incoming messages such as in Subsequent SAM messages or in multiple INVITE messages. In this scenario the Called-Station-Id attribute contained only part of the complete Dialed Number. This feature buffers the Dialed Number before sending the Access-Request message and when all digits are collected, it sends the Called Station-Id attribute to the RADIUS server for processing. The feature is always enabled and functions whenever Overlap signaling is enabled in the channel group object. Refer to the topic below for more information.
Call Flow Diagram
The Call flow diagram displays the functionality of the RADIUS - Overlap Call Processing feature.
A call is received from the SS7 network. Since the call being received is received using Overlap signaling, the initial IAM message has the first of three digits of the original Dialed Number. (Dialed Number = 876)
The digit in the message is buffered in the IMG.
A subsequent SAM message with the second digit which is the number 7 is received and stored.
The last subsequent SAM message with the last digit which is the number 6 is received and stored.
Once all digits have been collected (as specified in diagram), an Access-Request message is sent to the RADIUS server. The Called-Station-Id attribute within the Access-Request message is populated with the complete Dialed Number received.
The RADIUS server does a lookup and responds with an Access-Accept message.
The call is then routed to the SIP network with either the incoming digits or any Redirect digits that come from the RADIUS server (with Prepaid Support Enabled).
Configuration
The RADIUS using Overlap Call Processing feature is by default always enabled. For the feature to function correctly, Overlap Enable field in the Channel Group object must be set to enabled in the Incoming channel group only. Below is screen capture of an SS7 channel group displaying how to enable overlap signaling.
Additional Info
RADIUS using overlap signaling is supported in SIP, SS7, and ISDN.
RADIUS using overlap signaling is supported when the overlap enable field is enabled in the Incoming Channel Group only.
RADIUS using overlap will not function if the overlap signaling field is set to Enabled in both the incoming and outgoing channel groups -or- just the outgoing channel group.