there is also RELAIS and CRISP
> ----------
> De : Ingrid Melve[SMTP:Ingrid.Melve@uninett.no]
> Date : vendredi 13 novembre 1998 13:10
> A : webrepl@cs.utk.edu
> Objet : Outline Inter Cache Communication
>
> Inter Cache Communication Protocols
>
> /Work in progress, content not to be trusted, comments welcome/
>
> This document (tries to, at least) gives an overview of inter cache
> communication protocols and techniques for web proxy caches.
>
> ICP
>
> Internet Cache Protocol
> * [1]RFC 2186 Internet Cache Protocol (ICP), version 2
> * [2]RFC 2187 Application of Internet Cache Protocol (ICP), version
> 2
> * [3]Internet Cache Protocol Extension (draft)
> * [4]ICP group
> * [5]ICP v1.4
>
> ICP is used by caches to query other caches about web objects, to see
> if a web object is present at the other cache.
>
> ICP uses UDP. Since UDP is unreliable, an estimate of network
> congestion and availability may be calculated by ICP loss. This
> rudimentary loss measurement does, together with round trip times
> provide a load balancing method for caches.
>
> Most current cache implementations support ICP in one form or the
> other.
>
> ICP does not convey information about HTTP headers associated with a
> web object. HTTP headers may include access control and cache
> directives, Since caches ask for objects, and then download the
> objects using HTTP, false cache hits may occur (object present in
> cache, but not accessible for sibling cache is one example). ICP
> suffer from all the security problems of UDP.
>
> Implemented in
> * [6]Harvest
> * [7]Harvest
> * [8]Squid
> * [9]NetCache (ICP version 3)
> * [10]BorderManager FastCache
> * [11]Netscape Proxy Server
> * [12]DeleGate
> * [13]MOWS
> * [14]Inktomi Traffic Server
> * [15]Cisco CacheEngine
> * [16]SkyCache
> * [17]Mirror Image
>
> WCCP
>
> Web Cache Control Protocol
> * No documentation publicly available
>
> The Web Cache Control Protocol is proprietary to Cisco.
>
> WCCP is used to transparently redirect web traffic from a router to
> the Cisco Cache Engine
>
> The Web Cache Control Protocol defines the communication between Cache
> Engines and routers. Using the Web Cache Control Protocol, a router
> redirects Web requests to a Cache Engine (rather than to the intended
> Web server). The router also determines Cache Engine availability and
> redirects requests to new Cache Engines as they are added to a cache
> farm.
>
> Implemented in
> * [18]Cisco CacheEngine
> * [19]Cisco CacheEngine
>
> HTCP
>
> Hyper Text Caching Protocol
> * [20]Hyper Text Caching Protocol (HTCP/0.0)
> (draft-vixie-htcp-proto-03.txt)
>
> HTCP is a protocol for discovering HTTP caches and cached data,
> managing sets of HTTP caches, and monitoring cache activity.
>
> HTCP includes HTTP headers, while ICPv2 does not. HTTP headers are
> vital information for web proxy caches.
>
> Implemented in
> * [21]Mirror Image
> * [22]Squid2 (partially)
>
> CARP
>
> Cache Array Routing Protocol
> * [23]draft-vinod-carp-v1-03.txt
>
> * [24]Microsoft CARP doc
> * [25]CARP site
>
> CARP is a hashing function for dividing URL-space among a cluster of
> proxy caches. Included in CARP is the definition of a Proxy Array
> Membership Table, and ways to download this information.
>
> An HTTP client agent (either a proxy server or a client browser) which
> implements CARP v1.0 can allocate and intelligently route requests for
> the correct URLs to any member of the Proxy Array. Due to the
> resulting sorting of requests through these proxies, duplication of
> cache contents is eliminated and global cache hit rates may be
> improved. [26][CARP]
>
> CARP is not a communication protocol, strictly speaking. One of the
> goals with CARP is to avoid inter-cache communication.
>
> CARP is used for clusters of web proxy caches, and clients may use
> CARP directly as a hash function based proxy selection mechanism.
>
> Implemented in
> * [27]Microsoft Proxy Server
> * [28]Netscape Proxy Server
> * [29]Squid (partially)
>
> Cache Digest
>
> * [30]Squid FAQ on Cache Digest
> * [31]Cache Digests (paper)
>
> Cache Digest allows proxies to make information about their cache
> content available to peers in a compact format.
>
> Cache Digest is not a protocol, but a compression technique for
> exchanging information about proxy cache content. A peer uses digests
> for identify co-operating caches that are likely to have a given web
> object. [32]
>
> Implemented in
> * [33]Squid2
>
> HTTP
>
> HTTP/1.0
>
> * [34]RFC 1945 Informational
>
> HTTP/1.1
>
> * [35]RFC 2068 Proposed Standard
> * (draft aimed at Draft Standard)
>
> One of the major changes from HTTP/1.0 to HTTP/1.1 is added support
> for web caching. The Cache-control: headers provides support for
> information providers to give cache directives.
>
> Multicast based protocols
>
> Several different trials have been made with multicast inter cache
> communication. Multicast ICP is implemented, but not in widespread
> use.
> _________________________________________________________________
>
> References
>
> Visible links:
> 1. ftp://ftp.nordu.net/rfc/rfc2186.txt
> 2. ftp://ftp.nordu.net/rfc/rfc2187.txt
> 3. ftp://ftp.nordu.net/internet-drafts/draft-lovric-icp-ext-01.txt
> 4. http://ircache.nlanr.net/Cache/ICP/
> 5. http://excalibur.usc.edu/icpdoc/icp.html
> 6. http://harvest.cs.colorado.edu/
> 7. http://harvest.transarc.com/
> 8. http://squid.nlanr.net/
> 9. http://www.netapp.com/netcache/
> 10. http://www.novell.com/bordermanager/fastcache/
> 11. http://www.netscape.com/comprod/proxy_server.html
> 12. http://wall.etl.go.jp/delegate/
> 13. http://mows.rz.uni-mannheim.de/mows/
> 14. http://www.inktomi.com/products/traffic/
> 15. http://www.cisco.com/warp/public/751/cache/
> 16. http://www.skycache.com/
> 17. http://www.mirror-image.com/
> 18.
> http://www.cisco.com/univercd/data/doc/netbu/hardware/webcache/webcache.ht
> m
> 19. http://www.cisco.com/warp/public/751/cache/cds_ov.htm
> 20. ftp://ftp.nordu.net/internet-drafts/draft-vixie-htcp-proto-03.txt
> 21. http://www.mirror-image.com/
> 22. http://squid.nlanr.net/
> 23. ftp://ftp.nordu.net/internet-drafts/draft-vinod-carp-v1-03.txt
> 24. http://www.eu.microsoft.com/proxy/guide/CarpWP.asp
> 25. http://egg.microsoft.com/carp/
> 26. ftp://ftp.nordu.net/internet-drafts/draft-vinod-carp-v1-03.txt
> 27. http://www.microsoft.com/proxy/
> 28. http://www.netscape.com/comprod/proxy_server.html
> 29. http://squid.nlanr.net/
> 30. http://squid.nlanr.net/Squid/FAQ/FAQ-16.html
> 31. http://wwwcache.ja.net/events/workshop/31/rousskov@nlanr.net.ps
> 32. http://wwwcache.ja.net/events/workshop/31/rousskov@nlanr.net.ps
> 33. http://squid.nlanr.net/
> 34. ftp://ftp.nordu.net/rfc/rfc1945.txt
> 35. ftp://ftp.nordu.net/rfc/rfc2068.txt
>
>
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