On 17-mei-04, at 1:01, Joe Abley wrote:
If you have an example of someone enabling multi-path BGP hacks in
order to allow selection of more than one path, and specifically one
who has ever selected two or more paths to different nodes of F (that
is, paths to 192.5.5.0/24) I would be very interested to hear about
it.
Feedback and measurement data we have seen has not yet revealed an
occurrence of this, and conversations so far with operators does not
suggest there is much risk that we will. Your data will be interesting
to hear, however, if you can pass it on.
This is pretty much impossible with Cisco equipment, as in order to
load balance, the different routes must all be learned from the same
neighboring AS. (So if everyone used Cisco equipment the AS paths would
have to be identical.) Additionally, the default way to do this is send
all packets towards the same IP address over the same link. Other
vendors also bend over backwards to avoid packets from the same session
being distributed over more than one link. (The idea is that reordering
packets is bad. However, sometimes the measures to avoid it are worse.)
But as long as we're dissing anycast root DNS servers: how many of the
root servers are being anycast now or in the future, and how many
won't? As we've seen a few times with .org, and thought we saw with
.org many more times, over-enthusiastic anycasting isn't without its
dangers.
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