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Operational Features
5-174 41-001343-02 REV04 – 05.2014
P-Preferred Identity Header for BLA Accounts
The IP Phones support the BLA specification, draft-anil-sipping-bla-02, which states that the P-Preferrred-Identity header
(RFC3325) gets added to the INVITE message to indicate the Caller-ID that is used for the call.
BLA Support for Message Waiting Indicator (MWI)
The IP Phones have an option for a Busy Line Appearance (BLA) configured line to send a SUBSCRIBE SIP message for a
Message Waiting Indicator (MWI).
You can configure this feature using the configuration files or the Aastra Web UI.
Limitations
The following are limitations of the BLA Support for MWI feature:
• The phone shows MWI for the first matching identity if more than one line with different user names has the same BLA
account.
• If a normal line has the same user name as the BLA user of another line, the phone shows MWI only for the normal line.
Configuring BLA Support for MWI Using the Configuration Files
Use the following procedure to configure BLA support for MWI.
Note:
The P-Preferred-Identity for BLA accounts is also sent for hold/unhold messages.
Notes:
• If you change the setting on this parameter, you must reboot the phone for it to take affect.
• Both the “sip explicit mwi subscription” and “sip mwi for bla account” parameters must be enabled in order for the
MWI subscription for BLA to occur.
• The MWI re-subscription for the BLA account uses the value set for the "sip explicit mwi subscription period"
parameter to re-subscribe.
4.Whether or not the "sip mwi for bla account" parameter is enabled, the priority for displaying MWI does not
change.
Configuration Files
For specific parameters you can set in the configuration files, see Appendix A, the section,“BLA Support for MWI” on pageA-77.