WebTV Proxy Server Q&A

December 15, 1998

Like AOL users, WebTV subscribers access the Internet through  a "proxy server". Proxy servers intercept traffic between servers and clients, "tweak" or cache it, then pass it along.

Why does WebTV use proxy servers?
Proxy servers allow WebTV to speed up users' Web sessions. By caching web content, proxies can deliver popular pages without needing to retrieve a unique copy from the Internet each time. Additionally, the proxy server can "tweak" individual pages to ensure that they will display properly on a television screen.

What is this "tweaking"?
To speed the download of pages, the proxy will optimize image and audio formats in addition to the HTML before sending the Web page and associated files along to a WebTV terminal. This process does not result in a visible alteration of Web site content.

What version of HTTP does WebTV implement?
WebTV's servers implement HTTP 1.0, with selected parts of 1.1.

Are all web pages cached?
No. The following types of pages will not be cached:

  • Pages that are passed through an SSL(secure) connection
  • Pages that have an associated cookie
  • Any page that does not contain  a "last modified" date and an explicit "expires" date

How do I keep my pages from being cached?
The most reliable way to keep pages from being cached by proxy servers is to alter your server configuration files. However, most Webmasters do not have access to these files, so the use of <meta> tags to emulate HTTP headers is common. WebTV proxy servers, unlike most other proxies, will honor "no-cache" directives given in this fashion.

There are several different ways of writing a "no-cache" meta tag, and all of them are seen on Web pages. There is no harm in inserting multiple <meta> tags within a document, but some are more useful than others.

<META HTTP-EQUIV="Expires" CONTENT="Thu, 01 Dec 1994 16:00:00 GMT">

The most reliable method of ensuring that your content is not cached comes directly from the HTTP spec. This meta tag specifies an "expires" field that has already passed. Thus, the proxy will not cache the content. Current WebTV proxies will honor this header.

 

<META HTTP-EQUIV="Expires" CONTENT="0">

A popular way of specifying a date in the past is to specify the date as "0". While this will work, Webmasters should note that it is not strictly "correct", and HTTP 1.0 servers are under no obligation to honor tags formed in this way.  Current WebTV proxies will honor this header.

 

<META HTTP-EQUIV="Cache-Control" CONTENT="no-cache">

This method of specifying a "no cache" directive to a proxy server came about in HTTP 1.1. WebTV will be supporting this in the next upgrade of its proxy servers. Current WebTV proxies will honor this header.

 

<META HTTP-EQUIV="Pragma" CONTENT="no-cache">

This meta tag is also commonly seen, although it is incorrect for a server to send this to a client. HTTP 1.0 specifies "pragma" as a header to be sent by clients when requesting a fresh copy of a page, not by servers. However, due to its widespread use, WebTV will support this header in the next upgrade of its proxy servers. Current WebTV proxies will honor this header.

Do WebTV users have static IP addresses?
To speed surfing, a WebTV terminal may issue requests through a number of proxies; anywhere from two to a a dozen. This results in a correspondingly large number of IP addresses for a single WebTV user during a single session for non-secure connections. If a connection is made through SSL, the WebTV user will bypass the proxy and have a static IP until an HTTP connection is resumed. Since the Web is primarily stateless, multiple IP numbers are rarely a problem. However, if your site requires users to maintain a static IP address during their non-secure sessions, please send an email to staticIP@webtv.net.This address is only valid for Webmasters who need this service.