Interworking 183 Message Content

The SBC supports interworking of 183 message content in both directions, creating the 183 on the SIP side and creating the ACM or CPG messages on the ISUP side. Via configuration, you can disable interworking of 183 messages or set the SIP to SIP-I interworking to be based on the presence of and the value of any PEM header present in a 183 Session Progress message.

Some standards do not require you to map 183 messages into ACM/CPG messages. When disabled, the iwf-for-183 parameter in the applicable sip-isup-profile supports these environments. The default value is enabled. This parameter operates for native interworking, requiring that you set the sipi-behavior option in the sip-config to iam-anm.

Enabling vs. Disabling 183 Interworking

When enabled, the SBC:

• Inserts ACM to first 183 or 180
• Inserts a CPG into any subsequent 18x
• Inserts the REL into the SIP BYE
• Inserts the RLC into the 200 OK of the BYE, and
• Inserts the ANM into the 200 OK

When disabled, the SBC:

• Does not insert any ISUP body into 183s
• Inserts the ACM into the 180 instead of any 183
• Inserts a CPG into all further 180s, and
• Inserts the ANM into the 200 OK

If the session setup sequence uses only 183s, the SBC inserts a CON into 200 OK instead of an ANM.