On Sun, Jul 7, 2013 at 6:39 AM, Ben Niven-Jenkins <[email protected]>wrote:
> Rich & Richard, > > On 6 Jul 2013, at 18:19, Richard Alimi wrote: > > On Fri, Jul 5, 2013 at 9:27 PM, Y. Richard Yang <[email protected]> wrote: > > RY:The exact requirement will be: > > If a Server s provides a cost map c, then its IRD must provide the > network map used by c, to avoid the case that s provides a network map n, > but c uses network map n'. > > > > RA: I tend to think its okay if the a particular IRD provides only the > cost map but not link back to the network map. I see the tradeoffs as the > following: > > > > Advantages of having a link to the network map (in addition to its ID): > > - easier for a client to "correct" itself if it somehow discovered an > IRD with the cost map > > > > Disadvantages of having a link to the network map (in addition to its > ID): > > - server is responsible for keeping track of back-references and > redundant information (as you point out) > > > > In general, I'm in favor of reducing the coupling as much as possible, > though admittedly a cost map and network map are coupled already by a > Version Tag. > > [BN] The difference is that both the networkmap-generator and the > costmap-generator have to deterministically produce the same Version Tag > for the same map input/generation, they don't need to know anything about > each other, so version tag generation can be loosely coupled. Backlinks > require the generator to know which (of possibly many) URIs it was called > from and therefore which backlink to use and are therefore more tightly > coupled. Interesting point that networkmap and costmap can be generated in different servers, as long as they are consistent. In other words, the VTAG generation must be deterministic from a given network. The scenario that I have in mind, which I assumed to be more typical, is that a control server computes a topology from the base network topology, extracts the nodes as the network map, and computes the pairwise cost (attributes) as the cost map. I agree with the comment on backlinks at the cost map. Richard > >
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