The SIP-ALG for LCOS has the following features:
- No local registration: The SIP proxy does not provide registration for SIP endpoints. Instead, it mediates the registrations directly to the approved SIP domains. Anmerkung: This means that it is impossible to set up a line backup over alternative voice lines (analog, ISDN).
- Transparency for SIP extensions: The SIP ALG also transmits unknown, non-standard header elements to enable the SIP messages to be communicated between terminal devices and SIP PBXs. Anmerkung: The SIP ALG determines an unambiguous destination for every SIP message. Forking (communication between multiple devices of the same identity) is handled upstream. The SIP-ALG merely provides transparent forwarding of these data packets.