Configuring Advanced Features
533
BLF Subscription
IP phones support BLF using a SUBSCRIBE/NOTIFY mechanism as specified in
. This
feature depends on support from a SIP server.
When the IP phone is configured to monitor a specific user, it sends a SUBSCRIBE message to
the server. A NOTIFY message which includes XML in the message body is sent to the IP phone
to inform the current state of monitored user. Once status of the monitored user is changed
from idle to busy or vice versa, the IP phone is notified from the server with a NOTIFY message.
You can manually configure the period of the BLF subscription.
Example of a SUBSCRIBE message:
SUBSCRIBE sip:[email protected]:5060 SIP/2.0
Via: SIP/2.0/UDP 10.3.20.1:5060;branch=z9hG4bK2940676338
From: "1010" <sip:[email protected]:5060>;tag=2493044525
To: <sip:[email protected]:5060>;tag=2527548726
Call-ID: [email protected]
CSeq: 2 SUBSCRIBE
Contact: <sip:[email protected]:5060>
Accept: application/dialog-info+xml
Max-Forwards: 70
User-Agent: Yealink SIP-T46G 28.82.0.20
Expires: 30
Event: dialog
Content-Length: 0
Example of a NOTIFY message (<state>confirmed</state> shows the call has been established):
NOTIFY sip:[email protected]:5060 SIP/2.0
Via: SIP/2.0/UDP 10.3.20.2:5060;branch=z9hG4bK276311022
From: <sip:[email protected]:5060>;tag=3436332841
To: "1010" <sip:[email protected]:5060>;tag=3098567568
Call-ID: [email protected]
CSeq: 4 NOTIFY
Contact: <sip:[email protected]:5060>
Content-Type: application/dialog-info+xml
Max-Forwards: 70
User-Agent: Yealink SIP-T27P 45.80.0.20
Subscription-State: active;expires=17
Event: dialog
Content-Length: 534
<?xml version="1.0"?>
<dialog-info xmlns="urn:ietf:params:xml:ns:dialog-info" version="3" state="partial"
entity="sip:[email protected]:5060">
Содержание SIP-T19 E2 T4 Series
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Страница 887: ...Troubleshooting 865 The phone begins rebooting Any reboot of the phone may take a few minutes ...