12 Feb
2007
12 Feb
'07
2:22 p.m.
It takes me ages too. I've to check the RFC due to the fact, that my UAS
was rejecting ACK with branch=0 and the result of the digg is, that I'm
not sure whether is it correct to use it at all.
If I skip the requirement in 8.1.1.7 Via:
The branch ID inserted by an element compliant with this
specification MUST always begin with the characters "z9hG4bK". These
7 characters are used as a magic cookie (7 is deemed sufficient to
ensure that an older RFC 2543 implementation would not pick such a
value), so that servers receiving the request can determine that the
branch ID was constructed in the fashion described by this
specification (that is, globally unique). Beyond this requirement,
the precise format of the branch token is implementation-defined.
then in 17.2.3 Matching Requests to Server Transactions we can read:
If the branch parameter in the top Via header field is not present,
or does not contain the magic cookie, the following procedures are
used. These exist to handle backwards compatibility with RFC 2543
compliant implementations.
The INVITE request matches a transaction if the Request-URI, To tag,
From tag, Call-ID, CSeq, and top Via header field match those of the
INVITE request which created the transaction. In this case, the
INVITE is a retransmission of the original one that created the
transaction. The ACK request matches a transaction if the Request-
URI, From tag, Call-ID, CSeq number (not the method), and top Via
* header field match those of the INVITE request which created the
transaction, and the To tag of the ACK matches the To tag of the
response sent by the server transaction. Matching is done based on
the matching rules defined for each of those header fields.
Inclusion of the tag in the To header field in the ACK matching
process helps disambiguate ACK for 2xx from ACK for other responses
at a proxy, which may have forwarded both responses (This can occur
in unusual conditions. Specifically, when a proxy forked a request,
and then crashes, the responses may be delivered to another proxy,
which might end up forwarding multiple responses upstream). An ACK
request that matches an INVITE transaction matched by a previous ACK
is considered a retransmission of that previous ACK.
Note the sentence marked by * (hope the formatting will sustain) - if
the branch is not present os does not contain the cookie (true for
branch=0).... top Via header field match those of the INVITE.... we have
branch id which does not start with the cookie - shall we use the branch
id for the matching or not? As I understand the text, we use the Via
header with the branch id, so it won't ever match the INVITE.
I'm looking forward to your comments.
OTOH, setting sync_branch=0 has helped (CVS head version).
Michal
On Wed, 2007-02-07 at 14:41 +0100, Jiri Kuthan wrote:
At 16:58 18/12/2006, Martin Hoffmann wrote:
Jiri Kuthan wrote:
sorry -- it takes me ages to answer. -jiri
forward.c:
/* calculate branch for outbound request; if syn_branch is turned off,
calculate is from transaction key, i.e., as an md5 of From/To/CallID/
CSeq exactly the same way as TM does; good for reboot -- than messages
belonging to transaction lost due to reboot will still be forwarded
with the same branch parameter and will be match-able downstream
if it is turned on, we don't care about reboot; we simply put a simple
value in there; better for performance
*/
if (syn_branch ) {
*msg->add_to_branch_s='0';
msg->add_to_branch_len=1;
} else {
main.c
/* shall use stateful synonym branches? faster but not reboot-safe */
int syn_branch = 1;
--
Jiri Kuthan http://iptel.org/~jiri/
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Serusers mailing list
Serusers(a)lists.iptel.org
http://lists.iptel.org/mailman/listinfo/serusers At 17:05 17/12/2006, Kapil Dhawan wrote:
<evil>
Ever used forward() in SER?
</evil> I am using RTC/1.2 library and its not generating
branch parameter.
too bad, most implementation can deal with it in backw2ards compatibility mode
but clients should no longer generate such branch. I would be looking for
a more up-to-date stack if I was you.