[e2e] Lost Layer?

Detlef Bosau detlef.bosau at web.de
Tue Feb 11 05:41:15 PST 2014

Am 11.02.2014 03:31, schrieb Joe Touch:
> On 1/11/2014 3:40 AM, Jon Crowcroft wrote:
>> In missive <52D04B36.9010005 at web.de>, Detlef Bosau typed:
>>   >>I would like to discuss the talk
>>   >>http://rina.tssg.org/docs/JohnDay-LostLayer120306.pdf
>>   >>given by John Day.
>>   >>
>>   >>What do you think, e.g., of the claim
>>   >>> •
>>   >>> TCP was split in the Wrong Direction!
>>   >>> • It is one layer, not two.
>> should have been 3 - as per the transport services work - its clear
>> you need a sublayer convergence (as per day's work)
> I disagree.
> There are three layers, but it's TCP that's incomplete. I don't at all
> understand the difference between a "network layer" and an
> "internetwork layer".
> I.e., the current layers are:
>     TCP + the pseudoheader (derived from the IP layer)
>         the endpoint IDs here combine the IP
>         address and TCP ports
>     IP (the internetworking layer)
>         endpoints = IP addresses
>     link
>         endpoints = link addresses
> I have no idea what a 'network' layer is that is different from what
> we currently call the link layer.

And you are not the only one to have this problem.

When you have a look at
title={ Protocol for Packet Network Intercommunication},
author={V.~ Cerf and R.~Kahn},
journal={IEEE Transactions on Communications},
month= "May",
year= "1974",
volume = "22",
number = "5",
pages = "637-- 648"

Cerf and Kahn had the same problem - and that's the reason for our
problems until today.

For about 40 years now, our "TCP System Model" is

Sender --------------------- Pipeline -------------------------------

That "Pipeline" can be a network path in a packet switched network is
simply ignored.

Cerf in RFC 675:

>    We specifically assume that fragments are transmitted from Host to
>    Host through means of a PACKET SWITCHING NETWORK [PSN] [ROWE70,
>    POUZ73]. This assumption is probably unnecessary, since a circuit
>    switched network could also be used, but for concreteness, we
>    explicitly assume that the hosts are connected to one or more PACKET
>    SWITCHES [PS] of a PSN [HEKA7O, POUZ74, SCWI71]

To make my comment as concise as possible:


(in other words: Refer to RFC 675 and you find the lost layer. It is
exactly the layer which Vint Cerf ignored.)

BTW: A look in RFC 896 and Nagle's algorithem exhibits, that eventually
someone told to the community that we  talk about (infinite) flows and
not about (finite) messages.

(a note to John Day: You sometimes refer to Metcalf and his remark,
networking would be interprocess communication. In conjunction with the
quote from Cerf, this is exactly the reason why we don't have a
functional congestion control. We repeat the same misconceptions for 40
years now.)

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