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Problems with Caching Proxy Servers (pronounced "cashing proxee servers")
  1. The Symptoms
  2. What's Wrong?
  3. How can the problem be remedied?
  4. Information you should know -- The Basics...
    More-detailed information
  5. Caching Proxy Servers are not the Web-Browser Cache
  6. Last-Modified & Expiration Information
  7. Dynamic Pages
  8. The Problem
  9. What can you do about it?

The Symptoms:

Missing form variables when posting: This seems to be specifically related to faulty caching proxy servers not transmitting the user's post information to VoyForums.

Seeing old pages: Many people have reported that new messages are not being posted -- this is over 95% of the time not the case, but is the result of seeing an old version of a message index among other complications with some servers on Internet failing to comply with standards. It must be mentioned that VoyForums doesn't have any way of sending you an "old" forum index, and this paper explains that the actual location of this problem is usually with your Internet Provider and their "Caching Proxy Server(s)". Please read-on to learn about the problem before you contact your ISP.
New messages not posting: As mentioned above, this is not the actual case, but is just a side-effect of old pages being seen, or VoyForums not receiving page-requests. Read on to know more...

What's Wrong?
Many Internet Service Providers (ISPs) use software on their machines to reduce on network traffic -- they do this by keeping a copy of the webpages transferred by their users. Known as caching, the technique can be beneficial to reduce on network load. However, many ISPs use outdated or flawed caching software (called proxy cache software) which does not abide by HTTP 1.1 standards. The two main problems are:

  1. Ignoring when a page's size changes:
    Many flawed proxy servers improperly ignore if a webpage changes size. If a document's size changes, the page should be considered un-fresh, and updated in the cache.
  2. Not recognizing dynamic content:
    Webpages often include a Last-modified time. Many program-generated pages include an option specifying to not cache the pages (called "no-cache"). Pages which include no caching information or modification times should be considered "dynamic" content pages, and proxy servers should not cache these pages. Why not include the "no-cache" with these pages? The reason is because this option is used by your web-browser as well, and using it in a page means the web-browser will reload the page over the network even if moving backwards and forwards. Using it would actually consume more bandwidth than if the proxy servers were fixed.

How can the problem be remedied?
The Proxy-Cache software must be fixed/updated by the ISP to comply with HTTP/1.1 standards. Free software like "Squid" is very-well behaved and available for use by anyone. In addition, we're told that "ProxyPlus" for Windows is also just about as good (thanks to Kevin from Remote Communications for his helpful information). Other software must be updated so it is compliant with the latest standards.

There is nothing that can be done from a website -- the change must be made at the ISP. This is because any changes on a website serving dynamic data either means the data will not be considered dynamic at all (and users won't see new pages), or will increase on network traffic -- defeating the purpose of the proxy cache servers.

Many ISPs have already updated their software after users reported the problem, but there are still some that refuse to take action.

Information you should know -- The Basics...
When you view a webpage over Internet, the page is sent through many devices before it reaches you. Most of these devices do nothing more than send the information the proper direction (routers, switches, hubs, etc.) However many Internet Service Providers (ISPs) have special computers set up which store copies of user-requested webpages. These computers are known as "caching proxy servers", "caching proxies," or "caching servers", and they are primarily used to reduce network traffic by serving pages to users from a local storage instead of it being transmitted the full distance each time.

How does it reduce network traffic? The idea is simple: Any user(s) wanting to view a webpage send out their request, but since the Caching Proxy "sees" this request first, it can check if it already has that page stored -- if it has that page stored in its cache, it returns the stored page to the user. This means the page doesn't have to be transferred from the original source again. This also means the page may be a bit old.

This usually works fine, and is a marvellous way to reduce network load on Internet. Unfortunately, some proxies are faulty and do not follow the standards...

Caching Proxy Servers are not the Web-Browser Cache:
Before we go on, it is important to mention that we have been discussing machines outside of a user's machine. The most common "cache" a user hears of is the one his/her browser keeps on their own machine. This cache stores the pages a user retrieves and keeps them on their own hard drive and in memory. The problems we are discussing are predominantly not under the control of the end-user, and reside outside on Internet. We we will tell you what you can do about it at the end of this document.

Last-Modified & Expiration Information:
It is standard practice for web-pages to be transmitted along with the time the file was last modified. This information is sent by the site serving the webpage. This merely tells your web-browser or the proxy server when it is thought the document was last changed, but doesn't say much about when it will change next.

Additionally, there is another bit of information that can be sent to tell a cache not to cache. This is an Expires time, and is used to force a cache to clear this document from its storage at the specified time.

Dynamic Pages:
Web-pages which are created by a program and contain content that changes often are referred to as "dynamic-content" pages. They often change the data every time they are loaded. It is standard for such pages to be transmitted with no last-modified time nor expires time. Proxy Cache servers are not "supposed" to store these pages. Proxy Cache servers should also check to see if a page's content-length has changed -- if it has, they should consider it not-fresh and update their cache.

The Problem:
Although caching servers aren't supposed to cache these pages, they don't all follow the standards. In particular, older versions of proxy software tend to be more faulty than newer ones -- they keep the pages stored even when they shouldn't. The result is that even clicking reload will load the old stored page from the caching proxy, and the source-site never receives the request. This means that VoyForums servers never even receive your request to load the page again -- you're seeing an old page stored by your ISP.

What can you do about it?
If you suspect you are seeing old pages, it is not VoyForums doing it but, most likely, you are seeing the stored page from a caching proxy server. This server probably belongs to your ISP, and is more-than-likely a server not following the standards.

We have now received word from some of our forum owners that their users have had this problem fixed after reporting it to their ISP. It is highly possible that this problem occurs because an ISP is using outdated or faulty proxy software.

There is nothing we can do about this from our end, although we have tried. Each method of trying to deal with these non-standard-compliant proxy-servers has its own complications. After trying numerous work-arounds, we found it best to leave our site handle things the way it should, and hope ISPs fix their cache proxies.

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