For those of you who do not know what BLF is...Great, if you can get it to work. It turns the NOTIFY message sent from the Voipfone PBX doesn't have the “Subscription-State” header.
Busy Lamps is for use with extensions on our PBX and means that - if you have a phone that supports it which at the moment that means all snom phones - you can see which extensions are busy, which are ringing and which are free.
This is obviously a very useful function for receptionists – they can see who’s available before transferring a call. But it is also useful for everyone, especially in a distributed business with extensions in different physical locations; at home or even in different countries; it works wherever the telephones are located. You can see whether an extension is available before you call it.
A useful side effect of this feature is that you can now simply press the key next to the extension number and it will dial the number for you directly.
According to RFC 3265, Section 3.2.4. Subscriber NOTIFY Behaviour
- NOTIFY requests MUST contain "Subscription-State" headers
which indicate the status of the subscription.
I contacted Voipfone and pointed this out to them and I am happy to say that this was the response I received:
You're right we don’t send a Subscription-State header if we send a NOTIFY for dialog-info and we should this has now been corrected and is going through change control and will be rolled across the network next week.WooHoo - Finally Voipfone's Busy Lamp Field (BLF) should work with Cisco, Linksys and OBIHAI phones as well as their Snom and gigaset range.