Re: [RRG] map change due to a path failure?

[jnc@mercury.lcs.mit.edu (Noel Chiappa)]

    > From: Brian E Carpenter <brian.e.carpenter@gmail.com>

    > That seems to assume that a failure will produce a map change. I expect
    > a failure to produce a change in the routing tables, but why should a
    > (temporary) failure produce any change in the map?

Because it's a lot less overhead to the system (overall) to change a mapping
entry, and then change it back when the failure has been remedied?

Of couse, if the failure affects *lots* of entries, then it's cheaper overall
to have the routing deal with it. However, it all depends on the exact nature
of the failure (which wasn't specified).

Unfortunately, we don't have any way (or tools) that would allow us to decide
whether it made more sense to handle something in one subsystem (mapping) or
another (path-selection).

    > I would expect this would cause the routing algorithm to be told about
    > the failure and to find an alternative path involving the same or an
    > alternative map entry.

In a perfect world, with a more rational routing (path-selection)
architecture, maybe. With the one we have, it does its thing without any real
interaction with its users. The existing system does its thing, and hands the
results down on stone tablets, take it or leave it.

	Noel

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