[SIPForum-discussion] Question on via and contact headers

[shuaib ahmad]

Hi All,

As we know via header contains address of hub through which it is
being passed to destination and destination would send back response
of request using via header entries. Contact header is used to send a
request(Re-INVITE, BYE)after first INVITE. If we do not include
contact header in INVITE, we are not able to send BYE( we do not get
200 OK).

My question here is if we have via header to send response back to
source then why do we need contact header in INVITE ?