Monday, October 12, 2015

CUBE - SIP - Enhanced 180 Provisional Response Handling

Source: http://www.cisco.com/c/en/us/td/docs/ios/voice/cube/configuration/guide/vb_book/vb_book/vb_1506.html

Information About SIP—Enhanced 180 Provisional Response Handling

The Session Initiation Protocol (SIP) feature allows you to specify whether 180 messages with Session Description Protocol (SDP) are handled in the same way as 183 responses with SDP. The 180 Ringing message is a provisional or informational response used to indicate that the INVITE message has been received by the user agent and that alerting is taking place. The 183 Session Progress response indicates that information about the call state is present in the message body media information. Both 180 and 183 messages may contain SDP, which allows an early media session to be established prior to the call being answered.
Prior to this feature, Cisco gateways handled a 180 Ringing response with SDP in the same manner as a 183 Session Progress response; that is, the SDP was assumed to be an indication that the far end would send early media. Cisco gateways handled a 180 response without SDP by providing local ringback, rather than early media cut-through. This feature provides the capability to ignore the presence or absence of SDP in 180 messages, and as a result, treat all 180 messages in a uniform manner. The SIP—Enhanced 180 Provisional Response Handling feature allows you to specify which call treatment, early media or local ringback, is provided for 180 responses with SDP:
Table 1 shows the call treatments available with this feature:

Table 1 Call Treatments with SIP Enhanced 180 Provisional Response Handling 

Response Message

SIP Enhanced 180 Provisional Response Handling Status

Treatment

180 response with SDP

Enabled (default)

Early media cut-through

180 response with SDP

Disabled

Local ringback

180 response without SDP

Not affected by the SIP—Enhanced 180 Provisional Response Handling feature

Local ringback

183 response with SDP

Not affected by the SIP—Enhanced 180 Provisional Response Handling feature

Early media cut-through