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Wednesday, February 10, 2010

Blu Ray DISC

Blu Ray  DISC
Blu-ray also known as Blu-ray DISC(BD) is a name of a next generation optical disc video recording format jointly developed by nine leading consumer electronics companies(Hitachi,LG, Matsuhita (Panasonic), pioneer, philips, samsung,sharp, sony, and Thomson). The format was developed to enable recording, rewriting and play back of high definition video(HDTV). Blu-ray makes it possible to record over 2 hours of digital high definition video(HDTV) or more than 13 hours of standard-definition video(SDTV/VHS Quality) on a 27 GB disc. there are also plans for higher capacity discs that are expected to hold up to 50 gb of data. the nine companies announced the joint establishment of the specification for blu- ray disc in feburary 19 2002 and after the hard work of the professionals of those companies it is in the market from April 10, 2003. An interesting factor about the blu-ray is that in near future we can find the collection Blu-ray disc of movies in the market as we get the collection of MP3 files.

Tuesday, February 9, 2010

Transparent Caching

the browsers should be configured explicitly to use a proxy server. this is not a headache anymore instructing each and every client to make proxy settings. Transparent caching is very handy in such cases. transparent caches are simple and they can be easily used in a network and do not require explicit coordination with other caches. Transparent caching in context of HTTP proxy caches means the transparent hijacking of the port 80, which is the default HTTP port. the cache hijacks the port 80 traffic whenever the client tries to request to the remote servers. the client does not have to configure his/her browser. instead squid transparently picks up requests and responses to the client. squid cache/proxy server acts as transparently caching servers and fulfils the clients requests of web objects, if available locally hence making efficient web browsing.

Web Caching

web caching refers to storing locally the once referenced web objects, should any future request come for that object, it is checked for in local store and if present there it is retrieved directly from the local store instead from the original server. It saves time, bandwidth and of course money. Web caching can be done at end users desktop or on dedicated cache server. Most of the present day browsers have support for caching to some extent though they are not of high performance and limited to a computer only. the most effective way to implement cache is by service provider. they can deploy a dedicated server and high performance web caching software. Wherever caching is done the goal is the same. It is better if ISPs cache web objects so that frequently referenced sites could be serve locally instead of downloading every time from the original servers. This increases throughput dramatically. the above discussions suggests that given sufficient storage, whole internet could be cached. However this is not true, Information is dynamic in nature and so is the web. If we cache everything we end up serving stale objects to the clients. this is worse than having slow access. there are methods to ensure the freshness of an object stored in a cache.

Wednesday, February 3, 2010

What is FTP ?

The FTP(File Transfer Protocol) utility program is commanly used for copying files to and from other computers. FTP is a general protocol that works on unix system as well as a variety of other (non unix) systems. FTP is basically used to promote sharing of files (computer programs and/or data), to encourage indirect or implicit(via programs) use of remote computers, to shield a user from variations in file storage systems among hosts, and to transfer data reliably and efficiently. FTP though usable direclty by a user at a terminal, is designed mainly for use by programs. FTP is in common use for downloading data and programs and for uploading files such as web sites to or from the servers of the same or different architecture.(such as windows PC,MAC ,etc).