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Re: 13 Root Server Limitation

2004-05-17 01:35:57
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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