[asterisk-users] 2 Problems with 1.6.2

[Jared Smith]

On Fri, 2009-07-17 at 13:30 -0500, Danny Nicholas wrote:
> In some cases MWI is referred to (perhaps incorrectly) as BLF.  Try
> searching on that.

MWI and BLF are two separate and distinct items.  The only thing they
have in common is that they both deal with lighting up little lights on
a handset.

MWI is Message Waiting Indication, where Asterisk sends a SIP NOTIFY
message to a to a phone to let the phone know that there is new
voicemail in the mailbox corresponding to that SIP device.  (You set the
corresponding mailbox by setting "mailbox=1234 at default" in the peer or
friend definition in sip.conf, where 1234 is the mailbox, and default is
the voicemail context or section name in voicemail.conf.)

BLF stands for "Busy Lamp Field".  BLFs are used for *all kinds* of
different things, but most often they're used for monitoring extension
state of another extension.  To make this work, you create a dialplan
hint for the device in question to map an extension state to a device
state and then make sure that call limits are enforced in the SIP
channel driver (so that it keeps track of device state.  The phone with
the BLF will then SUBSCRIBE to the status of the hint, and then when the
extension state changes, Asterisk will send a SIP NOTIFY to the phone to
let it know that the subscribed hint has changed states.

I know you're only trying to help, but please don't muddy the water by
telling people that MWI and BLFs are the same thing.


-- 
Jared Smith
Training Manager
Digium, Inc.