[e2e] Lost Layer?

[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. 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 
semantics).

Joe