[Serusers] more about record route

[Juha Heinanen]

i based my reasoning regarding the need to add record route only to the
initial request to this text in rfc3261.  i guess the proxy may add
record route to any request, but since it doesn't have any effect to the
dialog state, i don't see a point of doing it.

-- juha

12.2 Requests within a Dialog

Requests within a dialog MAY contain Record-Route and Contact header
fields. However, these requests do not cause the dialog s route set to
be modified, although they may modify the remote target URI. Specifi-
cally, requests that are not target refresh requests do not modify the
dialog s remote target URI, and requests that are target refresh
requests do. For dialogs that have been established with an INVITE, the
only target refresh request defined is re-INVITE (see Section 14). Other
extensions may define different target refresh requests for dialogs
established in other ways. Note that an ACK is NOT a target refresh
request. Target refresh requests only update the dialog s remote target
URI, and not the route set formed from the Record-Route. Updating the
latter would introduce severe backwards compatibility problems with RFC
2543-compliant systems.