[ih] When was Go Back N adopted by TCP

[Detlef Bosau]

Am 19.05.2014 00:26, schrieb Vint Cerf:
> i think this is not an adequate analysis. Delay variations between A,
> S, B and C might produce different timeouts even if the RTT
> measurement algorithms are the same. "fair"is not a simple notion in
> the dynamic and variable world of the Internet.

On the one hand, I agree. On the other: You put in question basically
all phd theses on congestion control from the last 20 years.

I just had a look at the ns2 code, I always (if unsaid) assumed, it did
go back n as retransmission strategy. (And from what I've seen 5 minutes
ago, it apparently does. However, I should take the time to have a
closer look at the code.)

=> Quite a lot of work in the past apparently made quite strong
assumptions, which may simply not hold in any cases,
=> many phd-theses were theses on "ns2" but not on "TCP".


What you say is no contradiction to my analysis. What you say is that an
identical rtt measurement algorithm may be insufficient to produce
"faire shares". (The term is not my invention, btw.)


Detlef
>
> v
>
>
>
> On Sun, May 18, 2014 at 5:49 PM, Detlef Bosau <detlef.bosau at web.de
> <mailto:detlef.bosau at web.de>> wrote:
>
>     Just to make my thoughts more clear.
>
>     Let A,B,C end nodes, S some switch.
>
>     A
>        \
>          S---------------------------------C
>        /
>     B
>
>     Assume one data flow from a to C, a competing one from B to C.
>
>     I expect that it makes a difference, whether both TCPs employ the same
>     RTO scheme or, e.g. A, uses a more aggressive one that does earlier
>     retransmissions than its competitor. At least when we expect both TCPs
>     to use a fair share of resources, both TCPs should employ the same
>     scheme.
>
>     Do you agree?
>
>     Detlef
>
>     --
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>
>


-- 
------------------------------------------------------------------
Detlef Bosau
Galileistraße 30   
70565 Stuttgart                            Tel.:   +49 711 5208031
                                           mobile: +49 172 6819937
                                           skype:     detlef.bosau
                                           ICQ:          566129673
detlef.bosau at web.de                     http://www.detlef-bosau.de

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