Re: HIP, the Host Identification Protocol

[Paul Francis--formerly Tsuchiya <[e-mail]>]

>  
>  If the host has no ID entry at all, then it must look up to see if it
>  already knows the router from a previous transaction.  (One of the
>  purposes of having the routers transmit HELLO packets is so that the
>  hosts can keep track of which routers they have heard from recently;
>  if the host goes too long without hearing from a router which
>  previously responded, then it can automatically fall over to the
>  next-higher-preference-value router, /without/ (and this is important)
>  having to wiretap the intra-area routing protocol.

But, router discovery already does this......routers send hellos,
hosts listen to them. 

>  
>  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.

>  
>  > If only the responsible router keeps the information, how can other
>  > routers do such things as load balancing?
>  
>  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.....

>  which wires.  They then agree between themselves that, for half of the
>  IDs on segment 2, router1 will use a preference of 0 and router2 will
>  use a preference of 1, with the roles reversed for the other half.

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

>  Now, when any /system/ on segment 1 wants to send to a first-half host
>  on segment 2, it gets back a preference-0 proxy HELLO from router1,
>  and a preference-1 proxy HELLO from router2; router1 also forwards the
>  packet to the destination host.  Now the sender will prefer to use
>  router1 to forward packets to that destination, unless it is down, in
>  which case it will automatically fall over to router2.

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......

>  
>  > This still confuses me.  THe inter-area and exit routers will learn
>  > about each other via the routing protocol.  Router discovery is
>  > limited to a single subnet (LAN).
>  
>  Right.  Don't forget that there are /hosts/ in this area, too!
>  

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.....

PX