Update ReverseProxy.md (#14)

Term is formally deprecated. Mention that and refer to GatewayProxy.md
for the updated documentation.

Author: yadij

docs/SquidFaq/ReverseProxy.md

@@ -1,161 +1,13 @@
 ---
 FaqSection: operation
 ---
-# Reverse Proxy Mode
+# Reverse Proxy
 
-## What is the Reverse Proxy (httpd-accelerator) mode?
+ * ## What is a Reverse Proxy?
+ * ## What is the Reverse Proxy Mode?
+ * ## What is the `httpd-accelerator` mode? (in Squid v2)
+ * ## What is the Accelerator (`accel`) mode? (in Squid v3-v6)
 
-Occasionally people have trouble understanding accelerators and proxy
-caches, usually resulting from mixed up interpretations of "incoming"
-and "outgoing" data. I think in terms of requests (i.e., an outgoing
-request is from the local site out to the big bad Internet). The data
-received in reply is incoming, of course. Others think in the opposite
-sense of "a request for incoming data".
-
-An accelerator caches incoming requests for outgoing data (i.e., that
-which you publish to the world). It takes load away from your HTTP
-server and internal network. You move the server away from port 80 (or
-whatever your published port is), and substitute the accelerator, which
-then pulls the HTTP data from the "real" HTTP server (only the
-accelerator needs to know where the real server is). The outside world
-sees no difference (apart from an increase in speed, with luck).
-
-Quite apart from taking the load of a site's normal web server,
-accelerators can also sit outside firewalls or other network bottlenecks
-and talk to HTTP servers inside, reducing traffic across the bottleneck
-and simplifying the configuration. Two or more accelerators
-communicating via ICP can increase the speed and resilience of a web
-service to any single failure.
-
-The Squid redirector can make one accelerator act as a single front-end
-for multiple servers. If you need to move parts of your filesystem from
-one server to another, or if separately administered HTTP servers should
-logically appear under a single URL hierarchy, the accelerator makes the
-right thing happen.
-
-If you wish only to cache the "rest of the world" to improve local users
-browsing performance, then accelerator mode is irrelevant. Sites which
-own and publish a URL hierarchy use an accelerator to improve access to
-it from the Internet. Sites wishing to improve their local users' access
-to other sites' URLs use proxy caches. Many sites, like us, do both and
-hence run both.
-
-Measurement of the Squid cache and its Harvest counterpart suggest an
-order of magnitude performance improvement over CERN or other widely
-available caching software. This order of magnitude performance
-improvement on hits suggests that the cache can serve as an httpd
-accelerator, a cache configured to act as a site's primary httpd server
-(on port 80), forwarding references that miss to the site's real httpd
-(on port 81).
-
-In such a configuration, the web administrator renames all non-cachable
-URLs to the httpd's port (81). The cache serves references to cachable
-objects, such as HTML pages and GIFs, and the true httpd (on port 81)
-serves references to non-cachable objects, such as queries and cgi-bin
-programs. If a site's usage characteristics tend toward cachable
-objects, this configuration can dramatically reduce the site's web
-workload.
-
-## How do I set it up?
-
-Several configurations are possible. The
-[ConfigExamples](/ConfigExamples)
-section details several variations of Reverse Proxy.
-
-{% include pages-list-by-path.html dir="/ConfigExamples/Reverse"%}
-
-## Running the web server on the same server
-
-While not generally recommended it is possible to run both the
-accelerator and the backend web server on the same host. To do this you
-need to make them listen on different IP addresses. Usually the loopback
-address (127.0.0.1 or ::1) is used for the web server.
-
-In Squid this is done by specifying the public IP address in
-[http_port](http://www.squid-cache.org/Doc/config/http_port), and
-using loopback address for the web server
-
-    http_port the.public.ip.address:80 accel defaultsite=your.main.website
-    cache_peer 127.0.0.1 parent 80 0 no-query originserver
-
-And [Apache](http://www.apache.org/) may be configured like in
-*httpd.conf*to listen on the loopback address:
-
-    Port 80
-    BindAddress 127.0.0.1
-
-Other web servers uses similar directives specifying the address where
-it should listen for requests. See the manual to your web server for
-details.
-
-## Load balancing of backend servers
-
-To load balance requests among a set of backend servers allow requests
-to be forwarded to more than one
-[cache_peer](http://www.squid-cache.org/Doc/config/cache_peer), and
-use one of the load balancing options in the
-[cache_peer](http://www.squid-cache.org/Doc/config/cache_peer) lines.
-I.e. the round-robin option.
-
-    cache_peer ip.of.server1 parent 80 0 no-query originserver round-robin
-    cache_peer ip.of.server2 parent 80 0 no-query originserver round-robin
-
-Other load balancing methods is also available. See squid.conf.default
-for the full the description of the
-[cache_peer](http://www.squid-cache.org/Doc/config/cache_peer)
-directive options.
-
-## Common Problems
-
-### When using an httpd-accelerator, the port number or host name for redirects or CGI-generated content is wrong
-
-This happens if the port or domain name of the accelerated content is
-different from what the client requested. When your httpd issues a
-redirect message (e.g. 302 Moved Temporarily) or generates absolute
-URLs, it only knows the port it's configured on and uses this to build
-the URL. Then, when the client requests the redirected URL, it bypasses
-the accelerator.
-
-To fix this make sure that defaultsite is the site name requested by
-clients, and that the port number of
-[http_port](http://www.squid-cache.org/Doc/config/http_port) and the
-backent web server is the same. You may also need to configure the
-official site name on the web server.
-
-Alternatively you can also use the location_rewrite helper interface to
-Squid to fixup redirects on the way out to the client, but this only
-works for the Location header, not URLs dynamically embedded in the
-returned content.
-
-### Access to password protected content fails via the reverse proxy
-
-If the content on the web servers is password protected then you need to
-tell the proxy to trust your web server with authentication credentials.
-This is done via the login= option to
-[cache_peer](http://www.squid-cache.org/Doc/config/cache_peer).
-Normally you would use login=PASS to have the login information
-forwarded. The other alternatives is meant to be used when it's the
-reverse proxy which processes the authentication as such but you like to
-have information about the authenticated account forwarded to the
-backend web server.
-
-    cache_peer ip.of.server parent 80 0 no-query originserver login=PASS
-
-> :information_source:
-    To pass details back as given **login=PASS** is an exact string
-
-### Visitor requests can force fetching new objects from the back-end server
-
-Client requests can contain *Cache-Control:* settings specifying
-no-cache, must-revalidate, or low max-age which cause Squid to
-revalidate or fetch new content from the backend web server rather
-earlier than needed. This raises load on the delivery system which can
-lead to bandwidth problems and rising costs.
-
-In [Squid-3.1](/Releases/Squid-3.1)
-and later the [http_port](http://www.squid-cache.org/Doc/config/http_port)
-**ignore-cc** options is available on accel ports. This option informs
-Squid to ignore the visitors control headers and depend solely on the
-headers provided by backend servers.
-
-    http_port 80 accel ignore-cc
+The terms **Accelerator Proxy**, **httpd-accelerator**, and **Reverse Proxy**
+were all used in the past to describe what the HTTP Standard now officially
+defines as a [**Gateway Proxy**](GatewayProxy).