H.323 and SIP Protocol Limitations and Restrictions

The following information should be noted for H.

323 Protocol:
  • If the phone has only the H.323 protocol enabled, the phone cannot be used to answer SIP calls.
  • If the phone has only the SIP protocol enabled, the phone cannot be used to answer H.323 calls.
  • If both SIP and H.323 protocols are disabled by mistake, the phone continues to work as a SIP-only phone; however, the phone is not registered (you are able to send and receive SIP URL calls).
  • The protocol to be used when placing a call from the user's local contact directory is unspecified by default. The user can select SIP or H.323 from the directory.
  • The protocol that is used when placing a call from the user's corporate directory depends on the order of the attributes in the corporate directory. If only SIP_address is defined, then the SIP protocol is used. If only H323_address is defined, then the H.323 protocol is used. If both are defined, then the one that is defined first is used.

    For example, if dir.corp.attribute.4.type is SIP_address and dir.corp.attribute.5.type is H323_address , then the SIP protocol is used.

  • By default, when more than one protocol is available, each protocol displays as a soft key and the user can choose which protocol to use.
  • Calls made using H.323 cannot be forwarded or transferred, and the following conditions apply:
    • The Transfer and Forward soft keys do not display during an H.323 call.
    • The Forward soft key does not display on the idle screen if the primary line is an H.323 line.
    • If a user presses the Transfer soft key during an H.323 call, no action is taken.
    • The auto-divert field in the local contact directory entry is ignored when a call is placed to that contact using H.323.
    • If a conference host ends a three-way conference call and one of the parties is connected by H.323, that party is not transferred to the other party that was part of the conference call.