Web Caching

Appendix C.  Cache Array Routing Protocol

CARP consists of two different components: a membership table format and an algorithm. The membership table is one way an agent learns about about the set of parent caches (the other is manual configuration). The algorithm is how an agent selects the appropriate parent for a given request.

The information in this appendix is taken from an expired Internet Draft. You can also find information on CARP by searching Microsoft’s web site.

Membership Table

The format of the Proxy Array Membership Table is an ASCII text file. It has a global information section followed by a blank line and a list of caching proxies with various parameters.

The first line of the global information section identifies the file as a CARP table and includes the protocol version number, for example:

Proxy Array Information/1.0

The draft document describes only CARP Version 1.0.

The remainder of the global information section consists of the following headers:

ArrayEnabled

The draft states, “This field allows proxies to advertise their implementation of CARP v1 even if they are not members of a Proxy Array.” Valid values are 0 and 1. Presumably, a caching proxy sets this field to 0 if it supports CARP but is not a member of an array.

ConfigID

This is a 32-bit integer identifier for a particular instance of a table. This is not a version number—you can’t use ConfigID to tell if one version of a table is newer than another. You can use it to find out if two members have the ...