[SIPForum-techwg] TCP vs. UDP (SP adoption of TCP?)
Kaushik V Shah
kaushik at ncoretech.com
Thu May 22 01:51:49 EDT 2008
Thank you for sharing the link to the document via a separate mail.
It seem like last line of first para of introduction of this document is
making the same point as what I have conveyed in my mail!
So I am confused with this response.
Clearly, this is not to say that UDP is better (which is also what
is conveyed in the document).
Can we recognize the value and give due credit to UDP?
Cheers,
Kaushik
Francois Audet wrote:
> 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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