Client Cache Communication
/Work in progress, content not to be trusted, comments welcome/
Finding a proxy
PAC
* [1]Automatic Proxy Configuration
Implemented in most web clients.
A JavaScript page on a web server hands out information on where to
find proxies. Clients need to point at the URL of this page. No
bootstrap mechanisme, manual configuration necessary. Manual
configuration is made easier by centralizing the script to one URL.
WPAD
Web Proxy Autodiscovery
* [2]Web Proxy Autodiscovery
WPAD uses a collection of pre-existing Internet resource discovery
mechanisms to perform web proxy auto-discovery.
The WPAD protocol specifies the following:
* how to use each mechanism for the specific purpose of web proxy
auto-discovery
* the order in which the mechanisms should be performed
* the minimal set of mechanisms which must be attempted by a WPAD
compliant web client
The resource discovery mechanisms utilized by WPAD are as follows:
* Dynamic Host Configuration Protocol DHCP
* Service Location Protocol SLP
* "Well Known Aliases" using DNS A records
* DNS SRV records
* "service: URLs" in DNS TXT records
WPAD is a proposal.
CARP
Cache Array Routing Protocol
* [3]draft-vinod-carp-v1-03.txt
Clients may use CARP directly as a hash function based proxy selection
mechanism. They need to be configured with the location of the cluster
information.
CARP is implemented in proxy servers. ( Actual implementations in
clients?? )
HTTP
HTTP is used for communicating with a web proxy. A web proxy may also
support other protocols.
Cache directives
HTTP/1.1 added support for cache directives. These cache directives
may
Privacy
Proxies may be used to anonymize users to web servers.
Security
Redirecting users through a proxy server gives access to all
information about usage and content of documents. This may be a
security risk, or it may create a single check point for communcation
as in firewalls.
Access controls based on IP numbers are not indicated in HTTP headers,
and caches have no way of knowing if a web object was access
restricted unless additional headers were provided by the web origin
server.
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References
1. http://home.netscape.com/eng/mozilla/2.0/relnotes/demo/proxy-live.html
2. http://egg.microsoft.com/wpad/
3. ftp://ftp.nordu.net/internet-drafts/draft-vinod-carp-v1-03.txt
This archive was generated by hypermail 2b29 : Thu Nov 18 2004 - 11:21:25 MST