On 15 Mar 2005, at 02:36, Lennon - Orcon wrote:
Just wondering how many providers other than citylink adapt anycast into their network. I decided to write something here to explain to others what it is and how I've implemented it.
Anycast can be used for things like:
DNS (Root Servers which are ready in Use in NZ) Multicast RP Points (For public RP points in different areas on an ISP) SNTP (it can be for NTP, but changing anycast servers could stuff it up) 6to4 gateways (192.88.99.0/24)/2002:c058:6301::
Normally anycast addresses are to be used in a stateless way (you cannot guarentee the 2 UDP or TCP sessions to come from the same anycast machine (as if routing to an anycast machine address stops it goes to an alternative machine) . Simple things like the above are only used in an anycast way..
No, lots of TCP-based services are distributed using anycast. The decision as to whether anycast is an appropriate mechanism is more complicated than "is the transaction stateless". For a more thorough description, see http://www.ietf.org/internet-drafts/draft-ietf-grow-anycast-00.txt (comments welcome). Joe