The internet is a vast pool of data and information that is scientifically systematized to help the billions of internet users to collect and utilize those data and information to accomplish their personal or professional needs. The internet is growing very rapidly and as per experts, it will continue to grow exponentially in size, which results in network overcrowding and server overloading. Thus, the experts have come out with a solution to get rid of such a problem even when there is overcrowding on the internet for certain shared data. This concept is called Web caching and has been proved to be the most effective solution to ease the service bottleneck and decrease the network traffic drastically, thereby minimizing the user access delay. Web resource caching thus have the two benefits-it reduces the load on the original infrastructure where the data are shared and at the same time reduces the user access latency.
In a nutshell, getting access to any data over the internet may be slow and expensive. A large number of searching requires many round trips between the client and the origin of the data or server. Too much traffic is the primary cause of delay in accessing what is searched hence it results into loss of time and money for a visitor. It is the ability to cache, i.e. preserving all the previously accessed resources and reuse them repetitively can optimize the overall performance of the internet.
The Working Procedure of Web Caching System:
Web sites have been frequently updating their web contents. News topics change, Sports results change, stock market information change, weather reports changes, and so on. This dynamism is more visible in e-commerce sites where product stocks and prices go on changing every minute. It is true that caching is not advantageous if it is returning outdated data or information. A traffic report that is two hours or more old doesn’t have much value to a visitor. The current advancement in IT has enabled to place checks and balances to make sure that the content the visitor is viewing is the most recent one. A Web site is constituted of many small parts that are adjusted with each other to make a whole page. A website possesses logos, images, text, graphs, sounds, and animations, etc. Each of these items is cached as different objects, while some items may not cache at all. For a news site say, news.com, normally the cache the user is accessing may store the logo object, advertising bars, and the rest of the stuff that makes up the fundamental look of the Web site. But the news pieces and articles never stored in the cache as these change every now and then. In this case, the user’s cache has made the site much faster to download because all the standing data and graphics are already stored in the cache, only the news items go on changing.
So how a cache does comes to know, what to keep inside and what to mark as a variable? It depends on a program developed by the Web developer, as also the way a cache is configured. As explained before, a website is made up of many individual pieces and each one of these pieces is specifically encoded with certain types of information that directs a cache how to manage it. The website administrator actually controls these items. There are numerous cache products available in the market. Each has a lot of diverse configuration options to ensure that the data repetitively accesses from a certain website are current.
Benefits of Caching
There are several advantages of using web caching:
- It reduces the rate of band width consumption thus network traffic is decreased to a great extent leading to less network congestion.
- It reduces delay in accessing a website or web content by two processes-
- As the frequently accessed websites or contents are accessed from a cache instead of the original server, the transmission time reduces drastically.
- The congestion in the server lessens which enables the users to access the other contents that are not stored in the cache quickly.
- Web caching drastically decreases the workload of the remote Web server by distributing data among the various caches over the wide-area network.
- Remote server may go inaccessible due to over congestion, sudden crash, or network partitioning. In such a condition, the cached copy in the proxy server can make the website accessible at least with historical data. This enhances the robustness of the web service.
Disadvantages of Web Caching:
Though the advantages of web caching are much profound than a few drawbacks, still the user should be aware of all related disadvantages too:
- The foremost drawback of caching is unavailability of current data and graphics when a proxy server is not updated regularly.
- The proxy cache itself can become overcrowded if the number of clients is more than the capacity. It causes a severe jam in the proxy server thus creating the same situation as happens in the remote server. The experts always ask to limit the number of clients in a proxy server. Fixation the maximum as also the minimum accessibility is a must for optimum utilization of a proxy server.
- It reduces the number of hits in the original remote server thus the traffic record will never show the actual data. This disappoints a lot of website visitors, information feeders, and buyers in an e-commerce site. Many internet users prefer to rely on popular websites only, thus the owners too disappointed as this hampers their marketing plan. For this reason, many website owners never allow their website contents to cache.
Types of Web Caches
Website contents can be cached at different locations along the path in between the client’s computer and the remote server. First, many browsers have built-in caches called browser cache. Next, a proxy cache which accumulates all of the requests from a group of clients. Lastly, a gateway cache can be located in front of an origin server to cache the all popular responses.
Here are some more details regarding these web caches:
Browser Cache: Browsers and other clients immensely benefited from a built-in cache. When a user presses the “Back” button in the browser, it can read the previous pages from its cache. Non-graphical agents cache objects as temporary files on the disk of the machine rather than keeping them in memory. The accessibility of a browser cache is limited to only one user and a minimum one user agent. Thus, it gets hits only when the user revisits a page with the “Back” button.
Proxy Cache: Proxy caches unlike browser caches are used by different users at once. As the traffic always remains high for a popular website proxy caching normally has high hit ratios than other types of caches. Also the hit ratio increases as the number of uses increases. This type of caching essentially services for numerous organizations at a time. They normally run on dedicated hardware. Proxy caching are usually located near the routers on the service provider’s place. This type of cache is located in such a way that maximizes the number of clients that can use it.
Gateway Cache: A gateway cache is located near the remote server or at a different point in the network in such a way and with such an authority that it works on behalf of the remote server and sometimes in co-operation with the remote server. Gateway Cache is highly functional in a number of occasions. Content distribution networks use Gateway cache to replicate the same information at various locations at the same point of time. Clients are directed to the gateway nearest to their locations which enable all of them to feel closer to the source server. The gateway cache is also used to decrypt HTTP or TLS connections and also to accelerate slow web servers.
Catching Architecture
Catching architecture is very much important for web resource catching. Two primary architectures are popularly used, which are as follows:
Hierarchical Catching Architecture: In this system, the catches are placed at multiple levels of the network. At the bottom of all these levels remain the browser caches or client caches. When the client fails to retrieve data the request is forwarded to the upper-level caches and in this way it reaches the remote server.
Distributed Catching Architecture: In this system there remains no other level in between the institutional cache and the user or the institutional cache and the remote server. If a cache is unable to retrieve a requested information or data then it passes it to the other institutional cache. The retrieving process runs in this way and ultimately it reaches to the remote server.
As internet service has become more and more trendy, users will increasingly suffer from congestion and overloading types of problems. Thus Web caching is successfully used as one of the effective techniques to improve server jams and reduce network traffic to the maximum possible extent. The major challenges for applying Web caching are data caching, proxy placement of caches, and efficient cache routing. Web caching is a real help for the modern-day server-related problems, but the website administrators must use it very proficiently to get maximum benefit out of these systems.