Christer,

No, I meant SDP should not be modified for the purpose of NAT traversal if ICE 
is used. It seems it can still be changed for other purposes.

John

> -----Original Message-----
> From: Christer Holmberg [mailto:[EMAIL PROTECTED] 
> Sent: 17 March 2008 13:42
> To: Elwell, John; IETF SIP List
> Subject: RE: [Sip] SBC impact on RFC 4474
> 
> 
> Hi John,
> 
> My comment was based on your "should not be applicable with 
> ICE" statement, and they way I understood it was that SDP 
> would not be modified if ICE is used.
> 
> Maybe I missunderstood what you were trying to say.
> 
> Regards,
> 
> Christer
> 
> -----Original Message-----
> From: Elwell, John [mailto:[EMAIL PROTECTED] 
> Sent: 14. maaliskuuta 2008 13:41
> To: Christer Holmberg; IETF SIP List
> Subject: RE: [Sip] SBC impact on RFC 4474
> 
> Christer,
> 
> I think I already captured that in the statement "Other 
> reasons are topology hiding, media shaping, etc.. Such 
> modification breaks RFC
> 4474 signatures."
> If you think that is insufficient, please elaborate reasons, 
> so we get a better understanding of the scope of the problem.
> 
> John 
> 
> > -----Original Message-----
> > From: Christer Holmberg [mailto:[EMAIL PROTECTED]
> > Sent: 14 March 2008 01:29
> > To: Elwell, John; IETF SIP List
> > Subject: VS: [Sip] SBC impact on RFC 4474
> > 
> > Hi,
> >  
> > SBCs may modify SDP even if ICE is used.
> >  
> > Regards,
> >  
> > Christer
> > 
> > ________________________________
> > 
> > Lähettäjä: [EMAIL PROTECTED] puolesta: Elwell, John
> > Lähetetty: to 13.3.2008 22:27
> > Vastaanottaja: IETF SIP List
> > Aihe: [Sip] SBC impact on RFC 4474
> > 
> > 
> > 
> > One of the questions raised at the end of the SIP session today was 
> > the
> > following:
> > 
> > "Are there any useful steps for dealing with SDP modification by 
> > SBCs?"
> > 
> > SBCs modify SDP (and perhaps other signed information in SIP 
> > requests).
> > One of the reasons is NAT traversal (should not be applicable with 
> > ICE, but I don't think we can always assume that ICE is used).
> > Other reasons
> > are topology hiding, media shaping, etc.. Such modification 
> breaks RFC
> > 4474 signatures.
> > 
> > SBCs also sometimes change From URIs in SIP requests, as 
> discussed in 
> > draft-kaplan-sip-uris-change-00. We have taken this into account 
> > during our various discussions (in the WG and off-line) on the 
> > telephone number problem, so I want to keep that separate. For this 
> > thread, assume an "email-style" (or non-phone-number-based) 
> From URI 
> > that is not modified by an SBC. Focus instead on 
> modification of other 
> > signed information.
> > 
> > I would like to hear views on the following:
> > - The degree to which this is a problem.
> > - Existing solution proposals:
> >     o draft-wing-sip-identity-media-02
> >     o draft-fischer-sip-e2e-sec-media-00
> > - Other solution proposals.
> > 
> > John
> > 
> > _______________________________________________
> > Sip mailing list  https://www.ietf.org/mailman/listinfo/sip
> > This list is for NEW development of the core SIP Protocol Use 
> > [EMAIL PROTECTED] for questions on current sip Use 
> > [EMAIL PROTECTED] for new developments on the application of sip
> > 
> > 
> > 
> 
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