|
North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: How relable does the Internet need to be? (Was: Re: ConvergedNetwork Threat)
--On 27 February 2004 14:52 +0000 Paul Jakma <[email protected]> wrote: Because you always want to get to an E911 service in the same AS number...You do or you dont? I dont see why anycast addresses need or need not be restricted to same AS. Anycast topology tends to follow AS topology, as people prefer their own routes. So if there is 205.1.2.3/32 anycast into (say) AS701 in DC (only), and anycast into (say) AS2914 in every US city, then it would not be unexpected for an AS701 customer in SF to reach the anycase node for 205.1.2.3/32 in DC, as AS701 will in general prefer its own routes. If you take a rural situation where you have your nearest (geographically) E911 service on some long link into Sprint, and the customer on some long link into UUnet, it is most unlikely they will be close (network wise) Anycast is arguable good for finding the best *connected* (i.e. closest using a network metric) server, but is pretty hopeless for finding a closest (using a geographic metric) server at anything much less than continental resolution. Further, it is heuristic in nature. For (say) DNS, it doesn't much matter if 1 in 50 queries go to a server far further away than they need to. For E911, it does. Alex
|