automatically switches to TCP

----- Original Message ----
From: Manjunath Warad <manjunathwaradhuawei.com>
To: "Xia, Zhi Feng (Bruce)" <brucexlucent.com>; IETF SIP List <sipietf.org&gt;
Sent: Tuesday, November 28, 2006 7:20:17 AM
Subject: RE: [Sip] automatically switches to TCP

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From: Xia, Zhi Feng (Bruce) [mailto:brucexlucent.com]
Sent: Monday, November 27, 2006 2:27 PM
To: manjunathwaradhuawei.com; IETF SIP List
Subject: RE: [Sip] automatically switches to TCP

Hi Manju,

1. Is this documented somewhere?  

 &nbsp; &nbsp;About switching of protocol, it is documented in RFC 3261 in sec 18.1.1.

 

"If an element sends a request over TCP because of these message size

constraints, and that request would have otherwise been sent over

UDP, if the attempt to establish the connection generates either an

ICMP Protocol Not Supported, or results in a TCP reset, the element

SHOULD retry the request, using UDP. This is only to provide

backwards compatibility with RFC 2543 compliant implementations that

do not support TCP. It is anticipated that this behavior will be

deprecated in a future revision of this specification. "&nbsp;

 

 &nbsp;  About transaction moving to terminated state, check in the transaction part of RFC 3261.

 

2. We had a stack which sends messages over UDP as mandated by UA, if UDP failure or transaction timeout(e.g. after 7 retrys of INVITE) it switches to TCP instead of going into terminated state -- this sounds violate your "MUST"?

 &nbsp; &nbsp;I am not sure why this behaviour is implemented; however,  I think this is violation of standard.

 

Thanks,

Bruce

-----Original Message-----
From: Manjunath Warad [mailto:manjunathwaradhuawei.com]
Sent: 2006?11?24? 11:07 PM
To: 'Xia, Zhi Feng (Bruce)'; 'IETF SIP List'
Subject: RE: [Sip] automatically switches to TCP

Hi Bruce,

 &nbsp;  I think this is other way round, if sending on TCP fails then it is recommended to try on UDP to keep the backward compatibility with RFC 2543.

After timeout transaction MUST enter into terminated state and will not retry by changing the protocol.

 

Regards,

Manju

 

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From: Xia, Zhi Feng (Bruce) [mailto:brucexlucent.com]
Sent: Friday, November 24, 2006 4:47 PM
To: IETF SIP List
Subject: [Sip] automatically switches to TCP

Hi,

There're many implementations when transportation on UDP fails or transation timeout without response it will automatically try TCP connection. Is this mandated in any RFCs? I think RFC3261 says if transaction timeouts it should go to terminated state.

 

Is this implementation a violation to RFC3261?

 

Thanks,

Bruce