Re: congestion control? - (was Re: Appointment of a Transport Area Director)

[Wesley Eddy <[e-mail]>]

On 3/5/2013 10:40 AM, Spencer Dawkins wrote:
> On 3/5/2013 8:15 AM, Brian E Carpenter wrote:
>> On 05/03/2013 11:55, Dearlove, Christopher (UK) wrote:
>>> I've no idea about the example quoted, but I can see some of their
>>> motivation.
>>>
>>> TCP's assumptions (really simplified) that loss of packet =
>>> congestion => backoff
>>> aren't necessarily so in a wireless network, where packets can be
>>> lost without
>>> congestion. This means that TCP into, out of, or across, a MANET
>>> using TCP can be
>>> bad. It then tends to happen that the MANET people don't fully
>>> understand TCP,
>>> and the TCP people don't fully understand MANETs.
>>
>> The effects you mention were definitely discussed in PILC.
>> http://www.ietf.org/wg/concluded/pilc.html
>> Maybe the PILC documents need revision?
>>
>>      Brian
> 
> TRIGTRAN tried to nail this down in more detail after PILC concluded (I
> co-chaired both PILC and the TRGTRAN BOFs). This quote from the IETF 56
> minutes pretty much captured where that ended up:
> 
> <quote>
> Spencer summarized a private conversation with Mark Allman as, "Gee,
> maybe TCP does pretty well often times on its own.  You may be able to
> find cases where you could do better with notifications, but by the time
> you make sure the response to a notification doesn't have undesirable
> side effects in other cases, TCP doesn't look so bad"
> </quote>
> 
> If we had to have all the TCP responding-to-loss mechanisms in an
> implementation anyway, and we could tell a sender to slow down, but not
> to speed up, it wasn't clear that additional mechanisms would buy you much.
> 
> References are at
> http://www.ietf.org/proceedings/55/239.htm and
> http://www.ietf.org/proceedings/56/251.htm
> 
> The high order bit on this may have been that TRIGTRAN wasn't IETF-ready
> and should have gone off to visit IRTF-land, but in the early 2000s, I
> (at least) had no idea how to make that happen.
> 


Later on, there was also a proposed TERNLI BoF and mailing list,
and bar BoF that resulted in:
http://tools.ietf.org/id/draft-sarolahti-tsvwg-crosslayer-01.txt
But didn't go any farther, that I'm aware of.  Section 6 actually
puts into context TRIGTRAN and other attempts to do something in
this space.  There's quite a bit of history just in the IETF.

RFC 4907 (IAB's "Architectural Implications of Link Indications")
is also a good snapshot of the thinking at that time.

-- 
Wes Eddy
MTI Systems