Hi Ingrid
As I suggested in the draft about ICP extensions, IPsec can provide its
strong integrity and authentication mechanisms for ICP. Thus, security
problems of ICP disappear by the use of IPsec.
---- ivan.lovric@cnet.francetelecom.fr tél : (+33) 02 31 75 91 25> ---------- > 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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