Subject: RE: [Sip] Re: draft-ietf-sip-congestsafe-02.txt

From: [email-masked]
Date: Fri, 7 Nov 2003 11:15:17 +0200

> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]]On Behalf Of ext
> Scott Lawrence
> Sent: Thursday, November 06, 2003 4:34 PM
> To: [email-masked]
> Subject: [Sip] Re: draft-ietf-sip-congestsafe-02.txt

> 
>     UAC     Proxy       Proxy     Proxy      UAC
>      A -----> B --------> C ------> D ------> E
> 
>   UAC A sends an INVITE to E with 'Proxy-Require: congestion-managed',
>   initially handing it off to Proxy B.  Using normal SIP routing
>   mechanisms, that message finds itself in due course at Proxy D
>   (the local proxy on E's network).  The administrator of that
>   network has (for whatever reason) chosen to configure SIP on that
>   network to prefer (or even be limited to) UDP.  This potential
>   conflict raises two questions:
> 
>    - Why should a user elsewhere in the network (A) be empowered to
>      exercise any control of routing policy within the local network
>      (E's network)?
> 
>    - Why would A want to send a request using this mechanism, given
>      that doing so introduces a new potential failure mode, but does
>      not improve that chances that this individual request will
>      succeed?

Actually, Proxy D uses the transport protocol that E has indicated in its contact-header of REGISTER.

REGISTER
...
Contact: <sip:[email-masked];transport=tcp>

This forces D to forward the message to E using TCP.

Proxies B, C, and D can have NAPTR entries without a udp option.

Eg of B network NSPTR records (no UDP option):

;       order   pref   flags         service      regexp     replacement
IN NAPTR 50     50      "s"    "SIPS+D2T"         ""           _sips._tcp.domain1.com.
IN NAPTR 90     50      "s"    "SIP+D2T"          ""           _sip._tcp.domain1.com

It is true that is a collected effort in that all domains have to configure their networks as above.

This is the BCP I would propose.

Regards,
Hisham

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