[e2e] Lost Layer?

l.wood@surrey.ac.uk l.wood at surrey.ac.uk
Tue Feb 11 00:57:13 PST 2014

says Joe:
> I have no idea what a 'network' layer is that is different from what we
> currently call the link layer.

RFC3819/BCP 89, which Joe wrote, calls ATM stuff etc. "subnetworks".

Which is to say, Joe wasn't calling them link layers then.

Lloyd Wood
From: end2end-interest-bounces at postel.org [end2end-interest-bounces at postel.org] On Behalf Of Joe Touch [touch at ISI.EDU]
Sent: 11 February 2014 02:31
To: Jon Crowcroft; Detlef Bosau
Cc: <end2end-interest at postel.org>
Subject: Re: [e2e] Lost Layer?

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

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

                endpoints = link addresses

I have no idea what a 'network' layer is that is different from what we
currently call the link layer. Links layers *are* networks (Ethernet,
SONET, etc.), except when there's no network at all (point-to-point
links that need no L2).

 > but also the
> socket layer needs revising badly to allow for a wider set of
> transport service semantics than came out of the fast
> hack that bbn and berkeley did

The real 'disconnect' (pun intended) is that TCP uses the initial SYN
destination port as both a service identifier and as part of the
connection demultiplexer (i.e., address at the TCP layer),
(see http://tools.ietf.org/html/draft-touch-tcpm-sno-00)

*and* that both TCP and IP layers use IP addresses as part of their
endpoint IDs (vs. having unique TCP endpoint addresses).

If there are additional semantics needed, IMO there is the need for an
additional layer and demultiplexer (at whatever layer you need that


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