well finally we made it. thanx to the Kristian's hint & the 'ss7 reset' command, i modified the mtp.c a little to circumvent chan_ss7 to not to wait for SLTA after sending an SLTM rather modified it in a way that it feels to be receiving an SLTA right after sending sending an SLTM, moreover i commented the line 'mtp3_link_fail(m);' that actually is executed to change the link-state to DOWN when the two tries & the
Q.707 timer T1 (to wait to receive an SLTA) gets expired, so removing this statement eventually prevented the link from going DOWN. one<br><br>then the 2nd prob was this:<br>Dec 16 01:10:25 WARNING[4904]: chan_ss7.c:2291 process_circuit_message: Group reset still in progress for CIC=3, typ=IAM message discarded.
<br><br>i.e. every message was being discarded, now the solution was lying in issueing & successfully executing a group reset command(to reset all channels) . The other side (EWSD) tech person was not able to issue such command for the link b/w we two(the reason i m not sure abt), but we do had a CLI cmd for this
i.e. 'ss7 reset', but this cmd never runs successfully (rather it crashes the Asterisk) when executed on a Blocked DOWNed Link (this is my experience for all the way last three months) & the link was blocked & DOWNed because of the above described reason (SLTA timeout). So basically preventing the link from going DOWN (by fixing SLTA prob) allowed the successful execution of 'ss7 reset' & that finally turned the channels' status as 'idle'
i.e. ready to receive/place calls<br><br>thanx to everyone for help<br>regards<br>