[asterisk-users] Wanted: tutorial on troubleshooting SIP issues

[Philip Prindeville]

For someone that's network-aware, but hasn't sat down and plowed through 
umpteen SIP-related RFC's and memorized the standards, is there a good 
primer on troubleshooting SIP issues?

I'm seeing a lot of NOTIFY/603 messages on my network between Asterisk 
and my Sipura 942's, for instance...

Not sure what these are...  perhaps the qualify keepalives?  In which 
case, I guess the 603 is moot...  but since the messages are originating 
from the Sipuras to Asterisk and not vice-versa, it wouldn't seem to be 
the "qualify"...  Next guess would be that they're NAT keepalives, but 
Asterisk and the phones are on the same private subnet (which in turn 
*is* NATted)...

Anyway, pointers for someone wanting to learn to quickly diagnose SIP 
conversations would be great.

Thanks,

-Philip