The IP Over NBMA (ION) Archive

[Albert Manfredi <manfredi@arl.bna.boeing.com>]

Andre N. Fredette wrote:

> The OSPF Address Resolution Advertisement (ARA) Option proposed by Rob
>
> Coltun and Juha Heinanen seem to be very useful for ATM (or NBMA)
> networks.
>  They allow OSPF to be used to distribute shortcut addresses as an
> alternative to using NHRP.

Sounds like the router becomes, in effect, the NHS. I always found this
sort of approach attractive. That is, instead of piling on yet another
server to cover up yet another sin. A long time ago, I suggested that
the DNS could do this job, for ATM anyway, although the reactions I got
were that the DNS is too slow to keep "layer 2" addresses. (If native
E.164 addressing is used for ATM, the "layer 2" addresses would change
no more frequently than the IP addresses.) I guess another problem is
that the DNS would have to be made smarter, to know about topology of
the ATM net.

> Some people have proposed performing similar shortcut routing on
> broadcast
> LANs (e.g., Ethernet).  Given multiple subnets on a single broadcast
> LAN
> (perhaps using 802.1Q VLANs) NHRP or ARA could be used to obtain MAC
> addresses for inter-subnet traffic.

OK. Of course, with full duplex, switched Ethernets, the physical size
of these LANs can be pretty WANish. All of a sudden, it becomes
attractive not to force traffic over routers for what a Martian would
consider purely bureaucratic reasons.

> This approach requires a single spanning tree to be maintained for the
>
> entire switched ethernet domain over which the shortcuts are desired.
> It
> is my belief that this application of shortcuts doesn't scale well and
> is
> of very limited utility.

Probably so but, you know, it might scale just fine for a corporate
intranet.

Thanks for the precis. I'll read Juha's draft.

Bert
manfredi@arl.bna.boeing.com