IƱaki Baz Castillo writes:
Anyhow, it could occur that the request contains a valid SIP header (token: value) but with an invalid grammar (i.e. a P-Asserted-Identity with a wrong URI value). The proxy could not check it (because in some configuration it just ignores such a header) but later the UAS/GW could inspect it and drop the request since the header is invalid (and it could reply a 400 or just drop the request).
where in rfc3261 is it stated that UAS is allowed to drop a request that it could respond to (i.e., the request has valid via header).
-- juha