Example T.38 offer sent by a Cisco AS5350XM on detecting FAX:

v=0
o=CiscoSystemsSIP-GW-UserAgent 1107 1281 IN IP4 192.168.0.1
s=SIP Call
c=IN IP4 192.168.0.1
t=0 0
m=image 33884 udptl t38
a=T38FaxVersion:0
a=T38MaxBitRate:14400
a=T38FaxFillBitRemoval:0
a=T38FaxTranscodingMMR:0
a=T38FaxTranscodingJBIG:0
a=T38FaxRateManagement:transferredTCF
a=T38FaxMaxBuffer:200
a=T38FaxMaxDatagram:72
a=T38FaxUdpEC:t38UDPRedundancy