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
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