SIP B not Present

SIP B not Present

NOTIFY A that B has Not Signed In
NOTIFY A that B has <Not Signed In>

 

From the lecture notes “SIP Tutorial: Introduction to SIP” by Henry Sinnreich and Alan Johnston, formerly at http://smuhandouts.com/8393/SIPTutorial.pdf


Transcript

[slide144] The location server gets the SUBSCRIBE, and immediately I get a NOTIFY back that tells me, no, they're not signed in yet. But, meanwhile, this location server and the inbound proxy know that I'm waiting for B to appear.