Subject: RE: [Sip] RE: Stateless Proxy and SIP responses

From: "CHADLI Youssef RD-CORE-ISS" <[email-masked]>
Date: Thu, 25 Jan 2007 13:42:20 +0100

Hi,
 
According to RFC3261, a stateless proxy does not maintain a transcation state. Then when it receive a SIP response it cannot konw to which resquest it does correspond. Moreover, a stateless proxy does not perform retransmissions. 
 
Here is an extract from FRC 3261/8.2.7:
 A stateless UAS is a UAS that does not maintain transaction state.
 It replies to requests normally, but discards any state that would
 ordinarily be retained by a UAS after a response has been sent.  If a
 stateless UAS receives a retransmission of a request, it regenerates
 the response and resends it, just as if it were replying to the first
 instance of the request.
 
Best regards
 
Youssef 

________________________________

De : David Viamonte [mailto:[email-masked]] 
Envoyé : mercredi 24 janvier 2007 15:04
À : CHADLI Youssef RD-CORE-ISS
Cc : [email-masked]
Objet : Re: [Sip] RE: Stateless Proxy and SIP responses

A stateless proxy must receive all responses related to a request. Otherwise, the proxy is not able to know whether a proxied request succeeds, or a transmisssion error occurs, or the receiving entity died, ...

Additionally, consider a (stateless) forking proxy: it needs to receive an answer in one leg in order to cancel the request in the other leg, for example.

In general, observe that a request is only 50% of a full transaction. The minimum set of information any SIP node can proces is a full transaction. Therefore, in order to correctly process a request, a stateless proxy must receive and correctly process the answer(s) (e.g.: 100 Trying, 18x, 200 OK) as well. Afterwars, it may safely remain out of the signalling path of subsequent SIP messages.

For INVITE requests, the final ACK message may not traverse the stateless proxy. This is because the ACK is a "special" SIP message, not exactly a real request as other SIP messages.

Cheers,

David

CHADLI Youssef RD-CORE-ISS escribió: 

	Hi all, 

	RFC 3261 states that even a stateless SIP proxy must insert a Via entry containing its contact address in SIP request. Then, a stateless Proxy will receive all SIP responses to a proxied SIP request. However, in general, a stateless proxy would not need to receive the SIP responses to a being proxied request.

	I would like to konw what is the functional reason that leaded to mandate Proxy stateless to receive SIP responses for proxied requests.

	Thanks in advance 

	Youssef  

________________________________

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_______________________________________________
Sip mailing list  https://www1.ietf.org/mailman/listinfo/sip
This list is for NEW development of the core SIP Protocol
Use [email-masked] for questions on current sip
Use [email-masked] for new developments on the application of sip

---

From: David Viamonte <[email-masked]>
Date: Thu, 25 Jan 2007 13:58:04 +0100

Agreed.

I think the right reference is section 16.1 (stateless Proxy, not UAS).

Hence, I agree the right reason is backed by other mails sent by other
contributors.

Sorry for BS'itting :-)

Cheers,

David

Hi,

According to RFC3261, a stateless proxy does not
maintain a transcation state. Then when it receive a SIP response it
cannot konw to which resquest it does correspond. Moreover, a stateless
proxy does not perform retransmissions.

A stateless UAS is a UAS that
does not maintain transaction state.

It replies to requests
normally, but discards any state that would

instance of the request.

Best regards

Youssef

De : David
Viamonte [mailto:[email-masked]]

Cc : [email-masked]

A stateless
proxy must receive all responses related to a request. Otherwise, the
proxy is not able to know whether a proxied request succeeds, or a
transmisssion error occurs, or the receiving entity died, ...

Additionally, consider a (stateless) forking proxy: it needs to receive
an answer in one leg in order to cancel the request in the other leg,
for example.

In general, observe that a request is only 50% of a full transaction.
The minimum set of information any SIP node can proces is a full
transaction. Therefore, in order to correctly process a request, a
stateless proxy must receive and correctly process the answer(s) (e.g.:
100 Trying, 18x, 200 OK) as well. Afterwars, it may safely remain out
of the signalling path of subsequent SIP messages.

For INVITE requests, the final ACK message may not traverse the
stateless proxy. This is because the ACK is a "special" SIP message,
not exactly a real request as other SIP messages.

Cheers,

David

Hi all,

RFC 3261 states that even a
stateless SIP proxy must insert a Via entry containing its contact
address in SIP request. Then, a stateless Proxy will receive all SIP
responses to a proxied SIP request. However, in general, a stateless
proxy would not need to receive the SIP responses to a being proxied
request.

I would like to konw what is the
functional reason that leaded to mandate Proxy stateless to receive SIP
responses for proxied requests.

Thanks in advance

Youssef