Thanks for your response. I will do as advised.

Switch version : ACM 6.3 SP10 & SM 6.3.8

Interface : SIP Trunk

Setup : MediaGateway, will be referred as MG(A SipServer
running at x.x.22.7) talking to Avaya Session
Manager(x.x.221.112) via TLS & SRTP connection.

Agent : 6285

MG dials out to agent : Not captured in trace.

MG dials out to 6279 : 2 way audio b/w 6285 & 6279

MG holds : no audio. MG sends Invite with 'sendonly'

MG retrieves : one way audio from 6279 to MG/6285 only

During this step, Avaya shuffles IP with ACK message also changing the
crypto master key(inline:hIwhHWxzcgOESx/HtGAQ2iySPlOp3dDbFnwzWTL0). As
per RFC there is no response for ACK(well ACK itself is final response
for 3 way handshake of Invite), That leave no way for MG to send its
new crypto to far end. Without new key, Avaya extension 6279 can't
read the media thats been sent to it.

I can provide the traceSM trace for this scenario, if required.

Has anyone seen this/worked around this issue ?