Hi Dino, Sorry, I didn't look closely enough at what you wrote or the diagram. I planned to look at it properly later, and have now done so.
I added the image to http://www.firstpr.com.au/ip/ivip/lisp-links/ with a link to this discussion. > The top side shows the packet flow when the mapping doesn't exist > and the bottom side shows the packet flow when the mapping does > exist. OK. It is hard to show everything on a diagram, but a key point is the distinction between packets travelling natively on the Net and those travelling on the ALT network (LAT). The map request packet, which is perhaps an encapsulated initial data packet, travels along the GRE tunnel to the nearest ALT router. There, over the GRE links to other ALT routers, each ALT router forwards the packet according to its destination address 240.1.1.1. The structure of this LAT network results in the packet arriving at the correct ETR for this destination host. The map reply message goes back via the ordinary Internet (no GRE tunnels or ALT routers) to the ITR. Subsequent encapsulated data packets go from the ITR to the ETR via the ordinary Internet too. Its not clear to me how the 12.0.0.1 ITR has a tunnel to an ALT router, unless the dotted line "Low Opex" indicates a tunnel, without the need for a physical link to this ALT router. The diagram makes it look easy, with a single GRE hop between the first and the final ALT router. However, in reality, it would be common for the packet to have to ascend the highly aggregated ALT hierarchy before it could descend the hierarchy towards the ALT router with a direct link to the correct ETR. Also, each GRE tunnel may involve traversing multiple physical routers. This long path problem was discussed: http://psg.com/lists/rrg/2008/msg00229.html with a diagram: http://www.antd.nist.gov/~ksriram/strong_aggregation.png and a round-up of the debate: http://www.firstpr.com.au/ip/ivip/lisp-links/#long_paths - Robin -- to unsubscribe send a message to [EMAIL PROTECTED] with the word 'unsubscribe' in a single line as the message text body. archive: <http://psg.com/lists/rrg/> & ftp://psg.com/pub/lists/rrg
