SIP Normalization and Transparency Overview
SIP normalization and transparency is an optional feature that handles SIP interoperability issues between Unified Communications Manager and endpoints, service providers, PBXs, or gateways that implement SIP differently. To configure SIP normalization and transparency, apply a customized LUA script to a SIP trunk or SIP line. Unified Communications Manager applies the script to the SIP messaging that passes through the SIP trunks or SIP lines.
Upon installation, Unified Communications Manager contains default normalization and transparency scripts that you can assign to the SIP trunks and SIP profiles in your system. You can also create and import your own customized scripts.
SIP normalization scripts modify incoming and outgoing SIP messages. For example, if you are interoperating Unified Communications Manager with a Cisco TelePresence Video Communications Server, apply the vcs-interop script to the SIP trunk that connects the two. The script resolves the differences in the SIP messaging so that the two products can communicate.
You can apply a normalization script to any SIP trunk connection, regardless of which protocol is being used by the endpoint that connects to that SIP trunk.
SIP transparency scripts enable Unified Communications Manager to transparently pass SIP information, such as proprietary headers, from one call leg to the other. For transparency to work, both call legs must be SIP.
Another feature of SIP transparency is REFER transparency, which allows Unified Communications Manager to pass on REFER requests without acting on them. You can use REFER transparency in call center environments where a centralized agent may answer a call and then transfer the call to an agent who resides in the same geographical area as the caller. REFER transparency allows the centralized Unified Communications Manager to drop the call and shift call control to the new agent.
Default Scripts for SIP Normalization and Transparency
Upon installation, Cisco Unified Communications Manager contains the following default scripts for SIP Normalization and Transparency. You can apply these scripts to a SIP trunk or SIP profile, but you cannot edit these scripts. If none of these scripts meet your needs, you can create your own scripts:
HCS-PCV-PAI passthrough—Provides Cisco HCS platform integration with Enterprise IMS.
cisco-telepresence-conductor-interop—Provides interoperability for endpoints registered to TelePresence Conductor.
cisco-telepresence-mcu-ts-direct-interop—Provides interoperability between Cisco Unified Communications Manager and either Cisco TelePresence MCU or Cisco TelePresence Server.
diversion-counter—Provides capability to adjust the diversion counter.
refer-passthrough—Removes Cisco Unified Communications Manager from the call due to a blind transfer between SIP trunks.
vcs-interop—Provides interoperability for endpoints that are registered to the Cisco TelePresence Video Communications Server.