Subject: (ION) ipoa - distributed ARP server

From: Satya Rao <[email-masked]>
Date: Fri, 20 Feb 1998 11:10:19 -0600

Hi
This may be a non-issue and already been solved, but
I would like to know how ARP servers communicate in IPOA environment
(rfc 1577, 1483). I understand how it works within a LIS but, if a host
from a LIS wants to communicate with a host in another LIS in the ATM
cloud, How does the ARPServer of LIS1 communicate with the LIS2
ARPserver over ATM.
I can imagine how it would work in the case of a PVC, but what is best
way in dynamic environment, for ARPserver to know about all other
ARPservers in the WAN.

thanks,

-srao. 
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From: Albert Manfredi <[email-masked]>
Date: Fri, 20 Feb 1998 12:53:42 -0500

> cloud, How does the ARPServer of LIS1 communicate with the LIS2

Why should it? If a host from a LIS wants to communicate with a host
in another LIS, in the ATM cloud or any other cloud, within the RFC
1577 model of IP over ATM, that host must use the edge router(s) in
its LIS to get there anyway. It only needs to know the ATM address
of the edge router(s) in its own LIS. These can be configured as are
"default router" and optional routers in any IP configuration.

> way in dynamic environment, for ARPserver to know about all other

I think you're postulating an NHRP (Next Hop Resolution Protocol)
application. See the NHRP draft (I think its up to version 13.txt
now) for the answer. RFC 1577 does not support shortcuts across
LISs. RFC 1577 is very much like LANE in this regard.

With NHRP, in principle the ATMARP server could be combined with the
NHS (NHRP server). In NHRP, normal IP routing is used to find the
destination host, and when the optimal IP route is found, then the
ATM shortcut that makes most sense is established. If the two hosts
are in the same ATM cloud, the shortcut might be host to host
(assuming security controls allow). Otherwise, the shortcut would
just go to the best edge router of your ATM island.

Bert
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