| The Timestamp header field describes when the UAC sent the request to the
UAS. When a 100 (Trying) response is generated, any Timestamp header field
present in the request MUST be copied into this 100 (Trying) response. If
there is a delay in generating the response, the UAS SHOULD add a delay
value into the Timestamp value in the response. This value MUST contain the
difference between the time of sending of the response and receipt of the
request, measured in seconds. Although there is no normative behavior
defined here that makes use of the header, it allows for extensions or
SIP applications to obtain RTT estimates, that may be used to adjust the
timeout value for retransmissions.
For Example:
Timestamp: 54
author: BEA Systems, NIST version: 1.2 |