North American Network Operators Group

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Re: oh k can you see

  • From: Bill Woodcock
  • Date: Mon Oct 31 17:55:51 2005

      On Mon, 31 Oct 2005, Joe Maimon wrote:
    > Isnt this the standard problem? 


    > Why does anycast have any special bearing on the problem?

It doesn't, except that Vixie decided to do it anyway with F, and it 
sounds like now K is doing it as well.

I have no clue why.  The problems with doing this had been clearly 
understood for a long time, the putative benefit is negliglble, and to the 
best of my knowledge, none of those of us who run large anycast networks 
commercially have ever found it beneficial to use NO_EXPORT in the general 

I guess folks just like to be different.

    > Sites connected to providers who have chosen a path marked as NO_EXPORT as
    > best over one not so marked will not get any route to that prefix from
    > that provider. They better hope that they are connected to another
    > provider who did not select as best path a NO_EXPORT marked prefix.


    > NO_EXPORT is not safe to be used while trying to traffic engineer but
    > maintain global connectivity.


    > NO_EXPORT is only safe for more specific prefixes, as long as there is a
    > less specific prefix that is still usuable.

    > NO_EXPORT to a large provider with potential large numbers of single homed
    > BGP customers who may not be taking a 0/0 (in an attempt to use SAV?) is
    > probably not a good idea

    > NO_EXPORT to large providers raises the probablity of there being sites
    > who multihome to only those, therefore NO_EXPORT to multiple large
    > providers is almost certainly dangerous.

Which leaves the question of why F, and now K, appear to be trying to do