Re: The internet architecture

At 17:04 +0100 2008/12/29, Rémi Després wrote:
> John Day - le (m/j/a) 12/29/08 4:24 PM:
>
> > Re: The internet architecture
> > No it isn't Transport's job. Transport has one 
> > and only one purpose: end-to-end reliability 
> > and flow control.
> > "Managing" the resources of the network is the network layer's job.
> Reliably... and also efficiently.
Definitely.

> To transmit as fast as possible, including with 
> load sharing among several parallel paths, the 
> flow control function (i.e. the transport layer, 
> right?) has, in my understanding, to know how 
> many address couples it uses.
Strictly speaking, no, I would disagree that 
these are transport functions. Transport has no 
need to know any address couples.  That is why it 
has a connection id, i.e. concatenated port-ids. 
But then as I said, there really is no distinct 
transport or network layer.
This is where things get involved. because really 
the boundary between network and transport is a 
false boundary.  The last remnant of 
"beads-on-a-string" thinking.  One sign of this 
is the need for a protocol-id field in IP.  If we 
hadn't gotten into a battle with the PTTs over 
whether or not we needed a Transport Layer at 
all, I think we would have seen this a lot 
sooner.  But the battle caused lines to be drawn 
and forces to dig in.  ;-)
> Whether the transport layer can delegate some of 
> its flow control function to an intermediate 
> layer is IMO a terminology question.
Somewhat.  There is a fair amount of science on 
this topic under the heading of process control. 
The only purpose flow control should have in a 
transport protocol is to keep the sender from 
overrunning the receiver. <full stop>  Getting 
the terminology right can go along way to solving 
the problem.
> > Although, these distinctions of Network and 
> > Transport Layer are . . . shall we say, quaint.
> Yes, indeed.
>
> > Multihoming is fundamentally a routing problem. 
> > SCTP tries to claim to solve it by changing the 
> > definition, an old trick.
> I am not sure what the two definitions are.
> Being more specific would be helpful.
See below, but you did.  ;-)

> > ... Multihoming has nothing to do with what has 
> > traditionally been called the "Transport Layer."
> > It is a problem of routing not be able to 
> > recognize that two points of attachment go to 
> > the same place. ...
> In my understanding, knowing that two locators 
> are those of a common destination is the normal 
> result from getting these locators by 
> translation of an identifier, e.g. a domain name.
I don't believe the routing algorithms translate 
many domain names.  But you are right that a 
domain name is a synonym for a set of IP 
addresses.
Take care,
John

> RD
>
> > At 14:22 +0100 2008/12/29, Rémi Després wrote:
> >
> > > John,
> > >
> > > To pick a local interface for an outgoing 
> > > connection isn't the transport layer, e.g. 
> > > SCTP, well placed to do the job (or some 
> > > intermediate layer function like Shim6)?
> > > Thus, ordinary applications wouldn't need to be concerned.
> > >
> > > RD
_______________________________________________
Ietf mailing list
Ietf(_at_)ietf(_dot_)org
https://www.ietf.org/mailman/listinfo/ietf