[asterisk-users] my (SIP) INVITE is ignored

[lokotes]

Hi,
I'm struggling with this kind of problem:
my hardware sip phone is registering to Asterisk 1.2.10 successfully, 
but when I send INVITE to server - it receives the packet but (in sip 
debug mode) I see: 'Ignoring this INVITE request'.
While searching in 'chan_sip.c' I've found that this message shows up if 
variable 'ignore' is being set. This is when

if (p->ocseq && (p->ocseq != seqno)) {
	ignore = 1;
}

unfortunately there aren't any comments around, so anyone could explain 
what exactly is happening?

regards,
L.