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In einer eMail vom 20.11.2007 23:32:31 Westeuropäische Normalzeit schreibt
tli@cisco.com:
Tony, Brian,
Each node has to see a network topology where this node is surrounded by
nodes and links, whereby the more remote the looser the links, whereas the nodes
are all individual routers (even those at highest hierarchical level !!! ). The
length of each link between any two nodes is precisely determined due to the
routing protocol which builds this hierarchical topology. I expect that the
length of some hierarchical link is according to the number of physical link
hops in between the two adjacent nodes (not the geographical distance in miles
or km, which could be done as well, e.g. in order to build a disk for worldwide
car navigation ). What is needed: for each viewed node its geographical
coordinates (proper degrees, not the minutes or seconds) and the destination's
geographical coordinates, likewise, which would take 3 parameter octets in the
IPv4-header. DNS lookup should provide this info together with the IPv4
address. I hope, the ingress host can put the geo-info into the IPv4-header, or
at least some proxy who is close to the source user and has cached what he has
learned from a passing DNS query.
But then the real (strict) next link determination can be done even if the
destination node is not on the radar screen :-) but just some other node with
geo-data closest to the destination's geo-data.
So routing, fairly as close as we want by design, can be done without any
reachability info evaluation.
It could be done such close that the last few hops can be done just like in
OSPF, where each passed node forwards based on the reachability info of the
egress node, or, if you want, by using classic BGP, however with a small
routing table with geographical square degree- wide unique address prefix.
Heiner
On Nov 20, 2007, at 2:15 PM, Brian Carpenter wrote: |