can anyone explain this - from rfc791

[n***@gmail.com]

"a single physical host must be able to act as if it were several distinct hosts to the extent of using several distinct internet addresses."
I wonder if anyone can explain this to me. I know what multi-homing is about as regards interfaces, but this "virtualizing" of hosts as regards to addresses, I have not seen it described in any textbook. thanks

[Jorgen Grahn]

Post by n***@gmail.com
"a single physical host must be able to act as if it were several
distinct hosts to the extent of using several distinct internet
addresses."
I wonder if anyone can explain this to me. I know what multi-homing
is about as regards interfaces, but this "virtualizing" of hosts as
regards to addresses, I have not seen it described in any textbook.

I think they simply meant what the next paragraph says:

That is, provision must be made for a host to have several
physical interfaces to the network with each having several
logical internet addresses.

They write "distinct hosts", but I don't think that means
virtualization, or anything else beyond "someone talking to you via
address A shouldn't have to know that you also serve using addresses
B--Z".

/Jorgen

[Barry Margolin]

Post by Jorgen Grahn

Post by n***@gmail.com
"a single physical host must be able to act as if it were several
distinct hosts to the extent of using several distinct internet
addresses."
I wonder if anyone can explain this to me. I know what multi-homing
is about as regards interfaces, but this "virtualizing" of hosts as
regards to addresses, I have not seen it described in any textbook.

That is, provision must be made for a host to have several
physical interfaces to the network with each having several
logical internet addresses.
They write "distinct hosts", but I don't think that means
virtualization, or anything else beyond "someone talking to you via
address A shouldn't have to know that you also serve using addresses
B--Z".

And furthermore, there's no confusion between the IPs. If a client
connects to a server on address A, the source address of outgoing
packets must be A, not B.

[Nnaemeka David]

I never knew an interface could have several logical internet addresses. Then, what use is multi-homing; why have several interfaces when one can serve and you use that one for several addresses. That's precisely what baffles me.

[Rick Jones]

Post by Nnaemeka David
I never knew an interface could have several logical internet
addresses. Then, what use is multi-homing; why have several
interfaces when one can serve and you use that one for several
addresses. That's precisely what baffles me.

More than one physical interface can bring bandwidth and SMP scaling
advantages. It can also allow you to connect to the broader network
via multiple, independent paths.

rick jones

[Robert Wessel]

On Mon, 7 Oct 2013 08:11:28 -0700 (PDT), Nnaemeka David

Post by Nnaemeka David
I never knew an interface could have several logical internet addresses. Then, what use
is multi-homing; why have several interfaces when one can serve and you use that one
for several addresses. That's precisely what baffles me.

You might want several IP addresses on your machine in order to host
multiple services (keeping in mind that there are often better ways to
do that), provide routing between parts of the network, or to provide
connections to disjoint networks. OTOH, multiple physical interfaces
allow for redundant connections, increased throughput, routing and
connection to disjoint networks.

Parts of those lists are completely independent of each other.

[Lew Pitcher]

On Monday 07 October 2013 15:27, in comp.protocols.tcp-ip, "Robert Wessel"

Post by Robert Wessel
On Mon, 7 Oct 2013 08:11:28 -0700 (PDT), Nnaemeka David

Post by Nnaemeka David
I never knew an interface could have several logical internet addresses.
Then, what use is multi-homing; why have several interfaces when one can
serve and you use that one for several addresses. That's precisely what
baffles me.

You might want several IP addresses on your machine

And, often /do/ have several (at least, two) IP addresses on your machine:
the loopback (localhost.localnet) address of 127.0.0.1 counts as an IP
address.

Post by Robert Wessel
in order to host multiple services (keeping in mind that there are often
better ways to do that),

Sometimes, a multi-homed host provides different services based on the
network. A multi-homed host may, for instance, provide different "virtual
host" web addresses, depending on whether the connection came from an
internal network or an external network. Often, an outward-facing
web-services host uses an inward-facing network connection to converse with
(say) it's database host, or it's logging host.

Post by Robert Wessel
provide routing between parts of the network,

A smart router, with firewall, is often implemented /as/ a multi-homed host.

Post by Robert Wessel
or to provide connections to disjoint networks.
OTOH, multiple physical interfaces allow for redundant connections,
increased throughput, routing and connection to disjoint networks.
Parts of those lists are completely independent of each other.