Practical Anycasting (PA/PracAny)

It is thought that anycast has many potential abilities which enable various good and convenient functions. There are strong desires to make anycast useful in real-world services and various applications with ease. Currently, anycast is already used or designed to use in some services or applications (e.g. some DNS root servers, ..). Unfortunately, they are very limited and used by very limited people. We would like to change this situation. We would like to make a world that anycast is used by general and various services and applications by anyone with ease.

Reasons why anycast is not widely used are:

1. Definition on anycast function or terminology is vague.
   

   There are many misunderstandings on anycast. Some people do not even understand basic anycast functions, (e.g., they do not recognize differences between "subnet anycast" and "global anycast").

   We have to start from definition clarifications on them.

2. General mechanisms that enable to use anycast for general and various applications are not prepared.

   Many people misunderstand that special mechanism is necessary to use anycast for some services or applications, and it not easy to provide anycast functions.

   It must be possible to provide generic mechanisms that enable to use anycast for any services or applications with ease.

3. Since anycast address is assigned to more than one interface or node,a interface or node which is indicated by an anycast address may be changed during the same session/connection.

   It is thought that anycast can be used only for "one shot"-type connections and not used for "continuous"-type connections.

   This is a surface understanding. From practical viewpoints, there must be ways to use anycast for TCP/UDP "continuous"-type connections. Without them, anycast will be used only for some limited services and charm of anycast will be reduced.

Goals of the proposed Practical Anycasting WG are:

1. Clarify definitions on anycast function, terminology and requirements on anycasting.
2. Clarify problems in using anycasting in the real-world services and various applications with ease.
3. Solve above problems.
   • Design mechanisms and methods to use anycast for general and various services or applications with ease.
   • Design mechanisms and methods to use anycast for TCP/UDP "continuous"-type connections from practical viewpoints.
4. Make anycast useful in real-world services and applications.

Anycast, a communication service defined in IPv6 [RFC 3513, RFC 2460], provides a stateless best effort delivery of an anycast datagram to at least one host; and preferably only one host, which serves the anycast address [RFC 1546]. An anycast message is the one that should be delivered to one member in a group of designated recipients, particularly to the member nearest to the sender, according to the routing protocols' measure of distance [RFC 3513].

Anycast communication services may considerably simplify some applications. Other than using anycast queries to locate an appropriate server from a group of available ones, multiple mirrored Web sites can share a single anycast address with which users could simply send a request in order to obtain information. Improving system reliability, global load distribution among distributed servers, and host auto-configuration are other promising applications.

There are various problems regarding anycasting. Currently, there are no IETF WGs that are dealing with these issues. Therefore, we would like to create a new WG that would address these issues and identify additional ones.