The Routing Over Large Clouds Mailing List Archive by date

[Derya Cansever <dhc2@minuteman>]

Grenville:

RFC 1577 assumes that when the address to be resolved
is not in the same subnet as the host issuing the ARP,
is not in the same subnet as the host issuing the ARP,
then the route should go through a router in the subnet
acting as a gateway to other LIS's. As such, 
acting as a gateway to other LIS's. As such, 
when the host receives a reply
through the NHRP, it has no idea that it came from
NHRP and would cache the address as the one of its
gateway router. It is likely that this situation
would eventually create trouble for the host. However
tempting it may appear, I do not think it is a good
idea to implement NHRP without properly defining
and implementing NHRP host behavior.

Derya Cansever


gja wrote:

<<[Andy Malis wrote...]
<<[Andy Malis wrote...]
<<>>Attempting to clear up the confusion ... here is how the transition will
<<>>Attempting to clear up the confusion ... here is how the transition will
<<>>work:
<<
	<<[...]

<<The part I'm not seeing is the evolution of rfc1577-only hosts.
<<The transition plan seems to assume that hosts must be upgraded
<<to 'talk NHRP' if they want the benefits. Yet it occured to me
<<that in an LIS of X hosts and 1 ARP Server (and X >> 1) it
<<that in an LIS of X hosts and 1 ARP Server (and X >> 1) it
<<would be useful to also allow ARP Servers to be upgraded to
<<would be useful to also allow ARP Servers to be upgraded to
<<resolve host queries using NHRP. This (I think) would allow
<<rfc1577-only hosts to use cut-through VCs before having complete
<<local NHRP code. This is not quite the same as adding NHRP to the edge 
<<routers of 1577-only LISs.
<<
<<Resolution sequence for non-NHRP hosts becomes:
<<
      <<Local Host --> resolves addr from local cache
           <<|                   |
       <<(cache miss)           /|\
	<<ARP_REQUEST            |
	<<ARP_REQUEST            |
           <<|               ARP_REPLY
           <<|               ARP_REPLY
          \|/                  | 
           <<|                   |
      <<ARP Server ---> resolves addr from local cache
      <<ARP Server ---> resolves addr from local cache
           |                   |        
       <<(cache miss)           /|\
        NHRP request           |
           <<|               NHRP response
          <<\|/                  |   
           |                   |
      <<Nearest NHS ---> resolves addr from local cache
           <<|                   |        
       <<(cache miss)           /|\
        <<NHRP request           |
           |               NHRP response
          <<\|/                  |   
           <<|                   |
      <<Next NHS ---> resolves addr from local cache

<<etc.

<<Of course, this is only of relevance if people think there will
<<be rfc1577-only hosts out there :-)
<<
<<cheers,
<<gja