[SIPForum-techwg] TCP vs. UDP (SP adoption of TCP?)

Wed May 21 11:38:39 EDT 2008

Absolutely false. 

> -----Original Message-----
> From: techwg-bounces at sipforum.org 
> [mailto:techwg-bounces at sipforum.org] On Behalf Of Kaushik V Shah
> Sent: Wednesday, May 21, 2008 00:24
> To: Elwell, John
> Cc: techwg at sipforum.org; Russell Bennett; Hiers, David
> Subject: Re: [SIPForum-techwg] TCP vs. UDP (SP adoption of TCP?)
> 
> In context of 3261, UDP is as reliable as TCP due to 
> retransmissions over UDP.
> 
> TCP has clear efficiency issues compared with UDP and that is 
> fundamentally because, reliability - which is application 
> level issue, is being enforced irrespective.
> 
> For e.g. in context of SIP, response to request (1xx, 2xx, 
> ...) is itself an indication of request having reached the 
> remote (or the proxy who in turn takes on responsibility of 
> sending further up/down). Now if TCP is used, we are 
> introducing  two levels of ACK (one at TCP level due to 
> reliable transfer and other at SIP level in the form of response).
> 
> There are practical issues of UDP fragmentation, but imho, we 
> will be better off fixing these UDP issues, if possible.
> 
> Regards,
> Kaushik
> 
> Elwell, John wrote:
> > Yes, this has always been the thing that puzzled me. A lot 
> of vendors 
> > and service providers have tried to reproduce PSTN 
> capabilities with 
> > SIP. Yet PSTN signalling protocols always ran over a reliable 
> > transport, so the obsession with UDP seems to be a contradiction.
> >
> > John
> >
> >   
> >> -----Original Message-----
> >> From: techwg-bounces at sipforum.org
> >> [mailto:techwg-bounces at sipforum.org] On Behalf Of Hiers, David
> >> Sent: 20 May 2008 18:28
> >> To: Russell Bennett; Zweig, Greg; techwg at sipforum.org
> >> Subject: Re: [SIPForum-techwg] TCP vs. UDP (SP adoption of TCP?)
> >>
> >> All,
> >> As a service provider using an expensive mix of best-of-breed SIP 
> >> implementations that service a fair number of endpoints 
> and minutes, 
> >> I see the ability to use UDP as one of SIP's primary weaknesses.
> >>
> >> The attempt to supplant the TDM PSTN five-nines reliability is not 
> >> particularly well facilitated by running the entire show over an 
> >> unreliable transport protocol whose primary benefit is reduced HW 
> >> resource requirements.
> >>
> >> When shopping for future peering partners, I would tend to 
> prefer one 
> >> who's engineering philosophy happily embraces the deterministic 
> >> control of TCP rather than the fire-and-forget nature of UDP.
> >>
> >> Best regards,
> >>
> >>
> >> David Hiers
> >>
> >> CCIE (R/S, V), CISSP
> >> ADP Dealer Services
> >> 2525 SW 1st Ave.
> >> Suite 300W
> >> Portland, OR 97201
> >> o: 503-205-4467
> >> f: 503-402-3277
> >>
> >>
> >>
> >> -----Original Message-----
> >> From: techwg-bounces at sipforum.org 
> >> [mailto:techwg-bounces at sipforum.org]
> >> On Behalf Of Russell Bennett
> >> Sent: Tuesday, May 20, 2008 9:21 AM
> >> To: Zweig, Greg; techwg at sipforum.org
> >> Subject: Re: [SIPForum-techwg] TCP vs. UDP (SP adoption of TCP?)
> >>
> >> Greg et al.
> >>
> >> I have already agreed that we have to accommodate the past, but we 
> >> also have to drive the future.  If we "make it OK to just 
> offer UDP" 
> >> then that is what people will think that it is acceptable to do.
> >>
> >> I have been actively engaged with a number of service 
> providers for 
> >> quite some time now and, without naming names or providing 
> timelines, 
> >> I can assure you that TCP is being deployed by service providers.
> >>
> >> As for encouraging quick adoption - the issue is not one 
> of which SIP 
> >> Transport is best/cheapest/already there; the issue is one 
> of simple
> >> economics: SIP Trunks cannibalize Service Provider revenues under 
> >> existing pricing models.  The SPs who offer "UDP only" are seeing 
> >> little demand for SIP Trunking - what they don't realize 
> is that it 
> >> is a "chicken and egg" problem.
> >>
> >> We must move SP SIP connectivity capability forward such 
> that SPs can 
> >> start to deploy revenue generating services and applications to 
> >> replace revenue lost by decrementing PRI trunks.  We can 
> only get to 
> >> a service federation model by moving rapidly beyond SIP 
> Voice.  If we 
> >> can't *even* get to more broadly deployed SIP Voice, then 
> (some) SPs 
> >> will remain where they are - stuck in the 20th century.
> >>
> >> Forward looking SPs that I work with have heard this loud 
> and clear.
> >>
> >> UDP should be a 'MUST' to support older architectures.  
> TCP MUST be a 
> >> 'MUST' to support newer architectures.  I don't see how we 
> >> accommodate the past and drive the future any other way.
> >>
> >>
> >> Russell
> >>
> >> -----Original Message-----
> >> From: techwg-bounces at sipforum.org 
> >> [mailto:techwg-bounces at sipforum.org]
> >> On Behalf Of Zweig, Greg
> >> Sent: Monday, May 19, 2008 11:39 AM
> >> To: Peter Dunkley; techwg at sipforum.org
> >> Subject: Re: [SIPForum-techwg] TCP vs. UDP (SP adoption of TCP?)
> >>
> >> Agreed -- We also have to consider the capabilities at the 
> customer 
> >> premise.  I wouldn't want to advocate a solution that drives end 
> >> customers into a position where their existing equipment is made 
> >> obsolete.  There are many products in-use that could be 
> upgraded to 
> >> other facets of a SIPconnect 1.1 implementation but will 
> never cost 
> >> effectively support TCP.  I want to embrace them, not 
> disenfranchise 
> >> them.
> >>
> >> We need to accommodate the past while we drive the future.
> >>
> >> Greg Zweig
> >> Sonus Networks. Inc
> >> (978) 614-8027
> >>
> >>
> >> -----Original Message-----
> >> From: techwg-bounces at sipforum.org 
> >> [mailto:techwg-bounces at sipforum.org]
> >> On Behalf Of Peter Dunkley
> >> Sent: Monday, May 19, 2008 2:23 PM
> >> To: techwg at sipforum.org
> >> Subject: Re: [SIPForum-techwg] TCP vs. UDP (SP adoption of TCP?)
> >>
> >> The danger with this approach is that you will may end up with a 
> >> wonderful SIPconnect 1.1 recommendation that the 
> writers/purists love 
> >> but is unpalatable to the industry.
> >>
> >> There needs to be a pragmatic approach taken that illustrates what 
> >> SIP trunking should be, while still encouraging quick adoption.
> >>
> >> Making SPs have to choose between changing their architecture or 
> >> becomming compliant will not encourage them to adopt SIPconnect 
> >> (quickly
> >>
> >> or otherwise).
> >>
> >> Russell Bennett wrote:
> >>     
> >>> All,
> >>>
> >>> I know from trying to work with the SPs on SIP Trunking 
> that *some*
> >>>       
> >> SPs are going to take a firm position on the support of UDP 
> >> only.   The
> >> question that Janne poses is:
> >>     
> >>>         1) Are we going to define SC1.1 to be what a SIP
> >>>       
> >> Trunk service
> >> should be (e.g. UDP *and* TCP, among many other things)?
> >>     
> >>>         OR
> >>>         2) Write SC1.1 to be what we think will enroll more
> >>>       
> >> SPs in the
> >> SC compliance program?
> >>     
> >>> I argue strongly against 2 - this would not be a step forward on
> >>>       
> >> SC1.0.  3261 is very clear on TCP support.  If SIP Forum was a 
> >> commercial entity, then we would go for 2 to maximize revenue.
> >>     
> >>> However, SF is a standards body and it is incumbent upon us
> >>>       
> >> to develop
> >> SC1.1 as a *correct*, albeit pragmatic, document.  The key is the 
> >> balance between pragmatism and correctness and I, for one, 
> think that 
> >> accommodating SPs that are mired in the 20th century is the wrong 
> >> side of that balance.
> >>     
> >>> Russell
> >>>
> >>>
> >>>       
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> >
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