Re: HIP, the Host Identification Protocol

[[e-mail]]

(Is there anyone else out there on this list who has the slightest
interest in this?)

<<On Thu, 17 Jun 93 11:03:10 EDT, [e-mail] (Paul Francis--formerly Tsuchiya) said:

>>  If the host has no router entry, then it sends the packet as a
>>  multicast; the routers then hear this multicast and send back proxy
>>  HELLOs to the sending host (if it is not on the same LAN segment);

> SHouldn't be necessary.  When a host comes up, it sends out the
> router discovery solicitation message, and learns of routers.
> There should be no case where a host has a packet to send and
> doesn't know of a router.

Aha!  I see the confusion!  Remember that, in my model, there are /no/
intra-area redirects.  The host does not want to send the packet to
/a/ router, it wants to send the packet to /the/ router (i.e., the
router which will actually do the forwarding).

>>  Remember that /all/ routers which do intra-area routing are considered
>>  responsible.  Here's an example of how we would do load-balancing...

> Then, what is an example of a not-responsible router?  After all,
> all routers are running intra-area routing.....

No.  For example, the entry router for a domain should know about
inter-area routing, but if it is only connected to a single physical
subnetwork of an area, then it is not responsible in that area and so is
completely oblivious to intra-area routing (or rather, it knows no
more about it than a host on the same wire does).  In other words, it
participates in the level-[1/2] routing (that is its function), but
not the level-0 routing.

Note the interaction with router discovery here.  Because router
discovery is on a per-LAN basis, the hosts on the same LAN as our
``irresponsible'' router are able to discover it in the normal way;
however, hosts on a different LAN in the same area won't see it
directly, but rather their intra-area router (which /does/ have to
participate in level-1 routing) will advertise itself on behalf of the
original router.

> Huh?  The preferences are on a per-LAN basis.

No, they're not, that's the whole point!  (As I said in the original
proposal: it bears some resemblance to ESIS, but it most emphatically
is NOT the same!)

> How can a router give certain preferences to some hosts and not
> others....the router is only advertising one hello message, and it
> has a preference that all hosts record.....

No.  The router doesn't advertise a preference in the router HELLO,
only in the proxy HELLO.

> I don't think it is good for routers to be sending hellos individually
> to hosts, except in the case where a host has just booted and needs
> quickly to know which routers are there, in which case it does the
> solicitation and the routers respond......

Well, that's one of the major difference between HIP and ESIS.  (One
of the reasons why I call proxy HELLOs by that name is because of the
similarity to proxy ARP in IPv4.)

> Of course, but the routing protocol advertises the hosts, ala ISIS.
> Routers only need learn of hosts on their attached LANS via hellos.
> Routers learn of hosts not on their LAN but in their area via the
> routing protocol.....

Intra-area routers, yes.  Non-intra-area routers, no.

-GAWollman

PS:  I should point out that this is just my proposal; anyone else who
wants to see areas in Pip is free to create his/her own proposal and
protocols that do the same thing.

--
Garrett A. Wollman   | Shashish is simple, it's discreet, it's brief. ... 
[e-mail] | Shashish is the bonding of hearts in spite of distance.
uvm-gen!wollman      | It is a bond more powerful than absence.  We like people
UVM disagrees.       | who like Shashish.  - Claude McKenzie + Florent Vollant