Re: bad idea?

[Adrian Chadd <adrian () creative net au>]

On Wed, Jul 05, 2000, Greene, Dylan wrote:
> Jeremiah,
>
> Hey there.. What you're describing is basically anycast, (rfc 1546) which is
> useful for single packet, connectionless UDP type things (dns lookups), but
> can make connection oriented / statefull protocols break.  
>
> If you are advertising what appears to be two ways to get to the same
> prefix, you're relying on having stable paths through the internet to always
> deliver a packet via the same path the one before it took.  If something
> outside of your control breaks / changes, you may end up changing paths and
> could start sending packets towards your 'other' (same destination) site mid
> session. 
>
> Another thing to be careful of is inconsistent-as.  If you plan to have
> multiple sites advertising the same prefix, they either need to be all part
> of the same asn, or you need to advertise a separate anycast asn padded w/
> unique per-site asns. (Also a good way to withdraw routes is necessary,
> using gated or something..)  
>
> I think the anycast rfc mentioned setting aside a block of space for this
> purpose. 

If you originate it from the same AS then yes, it works just fine.
I've run it for web servers before, without a complaint, and
a few people here have run it for streaming media and can give you
feedback. I haven't tested it for long-held streaming media connections
so I can't comment.



Adrian