-Both To and From headers contain logical addresses. These headers are not used for routing purposes. -Contact header in general contains a SIP(S) URI for receiving subsequent requests. However, this header is NOT used in PUBLISH and MESSAGE requests as they do not expect any subsequent requests.
Please find a general guideline on these message headers and URI scheme usage at http://www.softfront.co.jp/tech/ietfdoc/draft/draft-ashir-simple-message-guideline-01.txt Ashir ----- Original Message ----- From: "Jonathan Rosenberg" <[EMAIL PROTECTED]> To: "Anil Bollineni" <[EMAIL PROTECTED]> Cc: "'xiao'tong liang'" <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]> Sent: Thursday, February 26, 2004 5:20 AM Subject: Re: [Sip] From Header > Responses are sent to the Via address, though more commonly to the > source IP/port of the request when TCP is used, or when rport is used > (RFC 3581) with UDP. The IP/port in the Via effectively provide a > fallback, to be used for the server to re-initiate a connection to the > client in the event of failure to send the response. > > Subsequent requests in a dialog are sent to the Contact URI. > > From is a logical identifier, used for display and policy purposes. > Please, please don't muck with it. > > Let me take this opportunity to preach a little on the role of ALGs in a > network. > > As a general rule, ALGs are quite problematic. They don't work in > conjunction with most of the SIP security mechanisms, including S/MIME > but more importantly sips and TLS. Their spotty presence in a network, > generally undetectable to application entities in the network, cannot be > depended on, and therefore can never serve as a complete solution for an > application service provider. Worse yet, when (and I say when, not if) > one of these ALGs does something wrong that breaks a call flow, it > becomes almost impossible to diagnose and correct. Generally speaking, > application layer intelligence does not belong in the core of the > network; that brings us back to the days of single-service networks > where the whole network needs to be upgraded to support a new > application. ALGs are contrary to the hourglass model that is one of the > defining characteristics of IP. > > I much prefer solutions like ICE, STUN, TURN and MIDCOM, which separate > application layer intelligence from firewalls and NATs, and allow for > applications to do the right thing for themselves for the purposes of > NAT traversal. > > As such, the right model is to NOT build an ALG, but if you must, build > a full protocol-compliant entity that just so happens to ship with and > be co-resident in your firewall/nat. That entity must be directly > addressed by other SIP entities, rather than being a transparent element > in the network. It is only through this model that we can create robust > and secure SIP networks. > > -Jonathan R. > > > Anil Bollineni wrote: > > > The Via header tells that IP address/port where the response should be sent. > > It does not specify from where the request has been come, as the ports for > > sending request and receiving responses can be different. I think the only > > way we can tell is by seeing the sending ip and port in IP header of the > > packet. Please correct if I am wrong. > > > > Thanks, > > Anil > > > > > > This email contains material that is confidential. The content of this email > > is for the sole use of the intended recipient(s). Any review or distribution > > by persons other than the intended recipient(s) without the express > > permission of NetScreen Technologies, Inc. is strictly prohibited. If you > > are not the intended recipient, please contact the sender and delete/destroy > > all copies of this email and any related attachments. NetScreen does not > > guarantee the accuracy or completeness of third party materials or > > information. > > > > > > -----Original Message----- > > From: xiao'tong liang [mailto:[EMAIL PROTECTED] > > Sent: Sunday, February 22, 2004 6:07 PM > > To: Anil Bollineni > > Subject: Re: [Sip] From Header > > > > Via header. > > > > -- > > xiaotong > > > > > > --- Anil Bollineni <[EMAIL PROTECTED]> wrote: > > > >>Hi All, > >> > >> > >> > >> I understand from the following statement in > >>RFC, that From header > >>SHOULD not contain IP addresses/ports from whom the > >>request has come. If it > >>is so, I can't assume that the information is not > >>used to assume from where > >>(IP address/port) the request has come. Appreciate > >>your response to clarify > >>the point. > >> > >> > >> > >> As such, it is very important that the From URI > >>not contain IP addresses > >>or the FQDN > >> > >> of the host on which the UA is running, since > >>these are not logical > >> > >> names. > >> > >> > >> > >>Thank you, > >> > >>Anil > >> > >> > >> > >>This email contains material that is confidential. > >>The content of this email > >>is for the sole use of the intended recipient(s). > >>Any review or distribution > >>by persons other than the intended recipient(s) > >>without the express > >>permission of NetScreen Technologies, Inc. is > >>strictly prohibited. If you > >>are not the intended recipient, please contact the > >>sender and delete/destroy > >>all copies of this email and any related > >>attachments. NetScreen does not > >>guarantee the accuracy or completeness of third > >>party materials or > >>information. > >> > >> > >> > >> > > > > > > > > __________________________________ > > Do you Yahoo!? > > Yahoo! Mail SpamGuard - Read only the mail you want. > > http://antispam.yahoo.com/tools > > > > _______________________________________________ > > Sip mailing list https://www1.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 > > > > -- > Jonathan D. Rosenberg, Ph.D. 600 Lanidex Plaza > Chief Technology Officer Parsippany, NJ 07054-2711 > dynamicsoft > [EMAIL PROTECTED] FAX: (973) 952-5050 > http://www.jdrosen.net PHONE: (973) 952-5000 > http://www.dynamicsoft.com > > _______________________________________________ > Sip mailing list https://www1.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 _______________________________________________ Sip-implementors mailing list [EMAIL PROTECTED] http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
