[TUHS] OSI stack (Was: Posters)
jnc at mercury.lcs.mit.edu
Tue Feb 5 06:29:47 AEST 2019
> From: Grant Taylor
> I'm not quite sure what you mean by naming a node vs network interface.
Does one name (in the generic high-level sense of the term 'name'; e.g. an
'address' is a name for a unit of main memory) apply to the node (host) no
matter how many interfaces it has, or where it is/moves in the network? If so,
that name names the node. If not...
> But I do know for a fact that in IPv4, IP addresses belonged to the
No. Multi-homed hosts in IPv4 had multiple addresses. (There are all sorts
of kludges out there now, e.g. a single IP address shared by a pool of
servers, precisely because the set of entity classes in IPvN - hosts,
interfaces, etc - and namespaces for them were not rich enough for the
things that people actually wanted to do - e.g. have a pool of servers.)
Ignore what term(s) anyone uses, and apply the 'quack/walk' test - how is
it used, and what can it do?
> I don't understand what you mean by using "names" for "path selection".
Names (in the generic sense above) used by the path selection mechanism
(routing protocols do path selection).
> That's probably why I don't understand how routes are allocated by a
> naming authority.
They aren't. But the path selection system can't aggregate information (e.g.
routes) about multiple connected entities into a single item (to make the path
selection scale, in a large network like the Internet) if the names the path
selection system uses for them (i.e. addresses, NSAP's, whatever) are
allocated by several different naming authorities, and thus bear no
relationship to one another.
E.g. if my house's street address is 123 North Street, and the house next door's
address is 456 South Street, and 124 North Street is on the other side of town,
maps (i.e. the data used by a path selection algorithm to decide how to get from
A to B in the road network) aren't going to be very compact.
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