Re: [Sip] Question on draft-ietf-sip-outbound-20 draft: multipleflowcreation

True, UDP flow may not be required if TCP flow has been setup to route
incoming traffic towards UA. But Won't it be an additional bonus if UA
creates a UDP FLOW in addition to TCP FLOW, so that network can still
reach the UA over the other transport FLOW when one FLOW is down (Unless
if both FLOWs got created with same host and all the FLOWs connected to
that host is down)? 
 
Also assume a UA has some local policy to prefer UDP transport over TCP
to transmit the outgoing SIP messages of size less than MTU. In such
scenarios, UA might want to establish both UDP and TCP FLOWs with the
same edge proxy and keep alive both the connections and use the
corresponding FLOW based on DNS lookup preferences and User's local
policy preferences to transport outgoing messages.

________________________________

From: Francois Audet [mailto:[email protected]] 
Sent: Saturday, August 29, 2009 12:23 AM
To: Vavilapalli Srikanth-A19563; [email protected]; [email protected];
[email protected]
Subject: RE: [Sip] Question on draft-ietf-sip-outbound-20 draft:
multipleflowcreation


I honestly don't know why anybody would want to do both UDP and TCP.
 
(In other words, if you set up a TCP flow, I don't see a benefit in also
setting up a UDP flow which you will have to maintain for keep alives).
 


________________________________

	From: [email protected] [mailto:[email protected]] On
Behalf Of Vavilapalli Srikanth-A19563
	Sent: Friday, August 28, 2009 07:46
	To: Audet, Francois (SC100:3055); [email protected];
[email protected]; [email protected]
	Subject: Re: [Sip] Question on draft-ietf-sip-outbound-20 draft:
multipleflowcreation
	
	
	Hi
	 
	Thanks for the reply..One more of clarification required..
	 
	So If UA wishes to create multiple transport flows with
"sip:primary.example.com"(As specified in
draft-ietf-sip-outbound-20#section-13 to honor RFC3261 requirement for
message size greater than MTU), would it be OK it one FLOW lands on
Host1 and other FLOW lands on Host2?
	 
	i.e for example if "sip:primary.example.com" got resolved into
(IP1, Port1, TCP) -> (IP2, Port2, TCP) -> (IP2, Port2, UDP) -> (IP1,
Port1, UDP) in that order, and if UA wises to create both TCP and UDP
FLOWs with "sip:primary.example.com", then it starts creating TCP FLOW
with (IP1, Port1, TCP) and can create a UDP FLOW with (IP2, Port2, UDP)
based on RFC 3263 procedures. Is my understanding correct here? 
	 
	In the above example, if (IP1) is down/crashed for some reasons,
then "sip:primary.example.com", can never use the TCP FLOW for
transporting inbound messages to that UA (Even though the IP1 and IP2
are state synchronized) until User Agent detects the FLOW failure with
(IP1) and re-create the TCP FLOW with (IP1 or IP2). Is my understanding
correct here?
	 
	Please clarify..
	 
	Regard
	Srikanth

________________________________

	From: Francois Audet [mailto:[email protected]] 
	Sent: Thursday, August 27, 2009 9:22 PM
	To: Vavilapalli Srikanth-A19563; [email protected]
	Subject: RE: [Sip] Question on draft-ietf-sip-outbound-20 draft:
multiple flowcreation
	
	
	You would have 2. One for primary, and one for secondary. For
each one of those, you would use normal RFC 3263 procedures for
determining which SRV record to use.


________________________________

		From: [email protected] [mailto:[email protected]]
On Behalf Of Vavilapalli Srikanth-A19563
		Sent: Thursday, August 27, 2009 07:57
		To: [email protected]
		Subject: [Sip] Question on draft-ietf-sip-outbound-20
draft: multiple flowcreation
		
		
		Hi
		 
		As specified in section 3.3/3.4 of
draft-ietf-sip-outbound-20 draft, If a UA is configured with a
outbound-proxy-set with two proxy uris: "sip:primary.example.com" and
"sip:secondary.example.com" And for example, "sip:primary.example.com"
got DNS resolved in to two SRV records "Host1" and "Host2" and
"sip:secondary.example.com" got DNS resolved in to "Host3" and "Host4",
Should UA create four FLOWs, One with each host OR just two FLOWs, one
with each proxy URI(i.e one flow with either Host1 or Host2 and second
flow with Host3 or Host4)?
		 
		Please clarify.
		 
		Regards
		Srikanth