Web cache (file sharing)

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Web cache called a caching technique that is suitable sharing - as some eMule mods or ProxyShare - allows the ISP to proxies download with mostly high speed cached data. In contrast to PeerCache , no new technology to be purchased and set up on the part of the ISP is required. Instead, the provider's existing proxy servers are used.

Since more and more ISP proxies have been discontinuing their service, web cache technology can usually only be used with the help of third-party proxies. However, this represents a misuse of the concept and usually does not achieve the desired speed in data transmission, since foreign users are usually treated at a disadvantage by the ISP proxies.

Technical principle

With the help of a downward-compatible protocol extension, webcache-enabled mods communicate with each other. The information is transferred whether there is web cache support and, if so, which proxy server is set. This is usually that of your own provider.

In order to instruct the proxy server to temporarily store the transferred data, both clients between which the transfer takes place must use a mod that is webcache-capable. The client that uploads the data now converts the data into blocks of 180 Kbytes each and makes them available via HTTP via the web server integrated in eMule .

The downloading client now downloads this data, instead of using the eD2K protocol, as an HTTP data stream via the set proxy. The prerequisite for this is that there are other known clients that use the same proxy and that it is assumed that they do not yet have the file parts to be downloaded.

Upon completion of the transfer of client Downloading other clients tells the same proxy, the HTTP - URL with the 180 kb block was available under on the uploading client before. These now send a request to the proxy for this data themselves. If the proxy has cached them, i.e. temporarily stored them, the blocks can now be downloaded from the proxy instead of via a conventional client-to-client connection.

advantages

  • On the client side, data can be downloaded at the speed that the proxy allows. As a rule, this is only limited by the bandwidth of the downloading client.
  • The distribution of data happens faster and more efficiently. In the hypothetical ideal case, a file would only have to be uploaded once so that it is downloaded by all customers of the same provider.
  • With the cached data, the providers save traffic to other providers, which usually has to be paid for. The data remains internal.
  • Since web cache uses the provider's existing proxy infrastructure, you do not run any legal risk.
  • No credits are used for data received through the web cache that are obtained for the normal upload (the web cache only functions as a free download reserve from outside the normal P2P network)
  • Web cache blocks are also encrypted, the Internet providers cannot be accused of complicity in the event that the transferred data is copyrighted or otherwise illegal material.

history

A web cache emule from 2006 with the typical web cache peaks within the download curve

The programming of the WebCache feature was done by a programmer named SuperLexx. The planning and preliminary considerations were carried out in the development forum of www.emule-project.net in a thread over 20 pages long that was originally started by a user named Sufcrusher.

Based on this discussion, a user named Brunni created a homepage on which the principle was explained. A forum has also been set up. Since the feature was not programmed and the official eMule team showed no interest, the project was put on hold for more than a year and development was stopped for reasons of time.

The developer of Emule-Morph later resumed development, programmed some improvements and fixed bugs. The homepage of the project, which was on sourceforge, had to be deactivated because the automatic proxy detection function caused too much traffic. With every connection to an ed2k server, a request was sent to a PHP script that passed the second part of the client's DNS as a parameter. (e.g. dip0.t-dialin.net) With the help of a MySQL query, the corresponding proxy with setting data was determined and returned as XML. This was arguably one of the greatest weaknesses. The idea seemed good, many emule users reported download increases of 10 to 30%, recognizable by the mostly 180 kB peak peaks that constantly stood out hedgehog-like from the normal download statistics curve.

However, because most people were probably too easy to find out their own proxy manually later and everyone could only use that of their own ISP so that the clients could identify each other, the web cache emules could hardly spread later, and the developers of the Web cache mods are also constantly struggling with prejudices that they would damage the network, so that today (2008) there is practically no current version of the emule with the web cache feature.

At times, even free proxy servers were set up in the Spanish area that could be used by everyone, but when the developers of Emule-Morph (at that time the flagship of all web cache versions) removed the web cache feature from their version, these servers were also closed again. This marked the end of the web cache era or at least its expansion within the P2P community.

criticism

In the official eMule version and some, also widespread, eMule mods (e.g. Xtreme) there is no web cache integration.

  • It is often stated that the web cache feature is a misuse of the provider proxies. On the other hand, it can be argued that proxy servers have largely lost their importance for providers, since regular cacheable HTTP traffic no longer causes the majority of Internet data traffic these days. With web cache, however, the basic intention of proxy servers is still preserved: The relief of external data traffic. However, it is feared that eMule will again be increasingly targeted by providers through web cache and that further "anti-P2P measures" could follow.
  • The use of public proxies for eMules Webcache, on the other hand, is an actual abuse that makes the above-mentioned principle of a win-win situation for ISPs as well as their customers ad absurdum. Especially in the Spanish area, users forward a URL to known, free proxy servers via various DDNS services . These are either intentionally (data protection, circumvention of internet censorship) not restricted to certain user groups or they are incorrectly configured. This still creates external traffic and proxies, which may have poor internet connections, are overloaded.
  • The method fell into disrepute due to some serious errors in earlier web cache versions. In the eMule network, you often come across users who use software that is compatible with the web cache, but who leave this function unused.
  • As a rule, there are many more failed web cache downloads than successful ones. This is due to the fact that the proxy servers delete the data packets very quickly if they are not requested regularly. If you now realize that querying the proxy server logically costs overhead and the data packets only have a very small file size (180 kB), web cache very quickly becomes an inefficient method if not - as is often the case - a large number compatible users can be found for a download.

Further file sharing applications with web cache support

Individual evidence

  1. ↑ Speed ​​up using ISP proxy webcaches ( Memento from January 13, 2010 in the Internet Archive )

Web links