Re: multihomed host

[William Waites <ww@styx.org>]

>>> "Iljitsch" == Iljitsch van Beijnum <iljitsch@muada.com> writes:

    Iljitsch> There is one difference that may be important sometimes,
    Iljitsch> but inconsequential  at other  times: a host  can detect
    Iljitsch> that an  interface is down. It  can't necessarily detect
    Iljitsch> the link to an ISP is down.

But the "physical  interface is down" failure mode  is relatively rare
-- as soon  as an ethernet switch,  or ethernet to atm  or mpls bridge
is thrown into  the mix, the "physical interface is  up but link layer
is down"  failure mode becomes much  more common. In  fact it subsumes
the first case since if there's no physical interface, there's no link
layer. 

Is the correct place to implement detection of these types of failures
in the link layer? But then  the providers have to play nicely, and it
says  nothing  about problems  more  than one  hop  out  in the  ISP's
network. Or beyond the ISP's AS even...

I  guess I  am  not sure  where  in the  stack  the failure  detection
belongs, or which types of failures are to be addressed here...

-w
-- 
William Waites <ww@styx.org>            Any sufficiently advanced
Idiosyntactix Research Laboratories	technology is indistinguishable
http://www.irl.styx.org			from a rigged demo.