The IP Over NBMA (ION) Archive

[Yao-Min Chen <ychen@fla.fujitsu.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.
> 
> 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.
> 
> 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.
> 
> Andre
> 

How is the spanning tree used?  Is it used only for forwarding control 
messages such as address resolution requests and replies,  or is it 
the case that shortcut paths have to traverse the spanning tree?  
Which part about the spanning tree does not make it scale? 

It will be even better if someone can also point me to related 
documents.  Thanks in advance.    

Yao-Min Chen  
Fujitsu Labs of America


> At 03:43 PM 8/19/97 -0400, Albert Manfredi wrote:
> >George Swallow's minutes included mention of OSPF advertisements which
> >incorporate layer 2 addresses, if I understood correctly. Did I get that
> >right?
> >
> >For ATM nets, maybe these could be used to create shortcuts. For IEEE
> >802 nets, what good are the layer 2 resolutions? I mean, is it an
> >extension to the proxy ARP concept, to include other networks? Will the
> >routers keep some sort of layer 2 table, for faster routing? Perhaps a
> >very quickly-aged table, of restricted size?
> >
> >If yes, it would be strange to see how an internet of IEEE LANs is
> >becoming more similar to ATM (shortcuts, switch-based, apparently
> >optimized for unicast rather than multicast).
> >
> >Can anyone clue me in? Thanks.
> >
> >Bert
> >manfredi@arl.bna.boeing.com
> >