Any good and latest web designer would always want to make sites that not only look great but also are quite fast to maintain and at the same time quite easy and simple to build. Server Side Include which has always been considered to be quite complex proves to be an amazing option especially for the small sites which need not be updated on a daily basis. If SSI is used properly it can definitely reduce the time that would be invested in the creation and the maintenance of any website.
The best part about SSI is that it is supported by all major leading web server platforms such as IIS and Apache. If IIS is the web server platform that is being used by you then SSIs are automatically enabled for all the files with extensions .stml, .stm or .shtml. But in case of Apache web server platform you would need to enable the SSI manually. As you can make it out from the name only that the main function of SSI is inserting the contents or the information contained in one file into another especially when the served up. Not only this you also have the option of inserting some other information such as file sizes, including the dates of the file modification and last but not the least the values of the server environment variables.
You can use the #include directive for including or inserting one file into the output of the other file. <! — #include virtual = “ /virtual/URL/to/file” –> It’s quite possible that this virtual attribute may appear a little funny if you have ever used SSI before or for that matter worked with IIS. This should not be mistaken with the file system path to the file but instead is a URL on the local server to the file. Thereby making the SSI files easier to move around from server to server as well as on the file system. Though the file attribute is widely accepted yet virtual is the general preference. If you are still persistent in using the file, you may end up in trouble while moving your web site from the development server to the production server.
Now once the basics are done it is now time to put it into action. In order to consider a typical situation wherein you would be first developing on the local machine and then later deploying it onto the server then you would have to get on developing a local web server. As there is definitely a difference between the two servers therefore it is always advisable to use the same local web server for the development and the production machines. And just in case if you have the plans of deploying on the Apache server and currently you are operating on the Windows desktop then you will have to make sure that the web server that is being used by you is surely an Apache server. And finally enable the SSI.
It is quite surprising though that you can actually reduce the redundancy by approximately 40% just by putting the navigation, footers and headers into your SSI files. This is surely a perfect way of reducing time especially during maintenance and construction. In case if you have certain download pages that have certain items that need to be updated regularly then you can make good use of the #flastmod directive as it is capable of keeping the download pages up to date. Therefore, it can well be seen and noted that SSI is a boom for the site developers and can be widely used for increasing the efficiency.
Usenet is a public discussion system which was developed to facilitate communication on the World Wide Web (WWW). Users from all over the world take part in the discussions to express their views on variety of topics and issues. Conceived by the students of the Duke University Tom Truscott and Jim Ellis in 1979, the Usenet looks like the bulletin boards and web forums. However the concept of Usenet is entirely different from these two even if the ultimate objective is same, i.e. to take part in online discussions or to broadcast certain information. The main difference between the Usenet and the Bulletin Board Systems (BBS) is that like the BBS the Usenet is not based on a central server and there is no central system owner, rather it is distributed among a large conglomeration of servers which change continuously and store and forward the Usenet messages to each other. Generally these servers operate in a loosely formed variable mesh topology.
Users of the Usenet generally read and post the messages on the local server operated by their ISP, University or by their employer. These messages are then exchanged among other servers online so that the information is available globally. The messages which the users read from or post to the Usenet are known as articles, posts, discussions or more popularly as news which are organized into different categories known as newsgroups. All the discussions are threaded with the help of news reader software. In order to use the Usenet the individuals have to subscribe themselves. Once they are logged into the user network (Usenet) the news client software application keeps track of all the activities of the users, activities like which articles they have read, the replies they have made or any new discussion initiated by them.
Generally, most of the discussions in a newsgroup are replies of some on going topics, i.e. one article is the reply of the other article. The set of articles which can be traced to one single no reply article is considered as a separate thread. Modern newsreaders display the discussions in the form of threads and sub-threads. This is very useful in case the users want to identify and follow a particular discussion in a high volume newsgroup.
Whenever a user starts a new discussion or replies to a post in a newsgroup it is available only for the users of that news server initially and then the different Usenet servers talk to each other periodically as per their configuration to copy the postings among each other and make them accessible on every network.
Usenet has its own cultural importance on the internet. It has given birth to many categories and sub-cultures and has offered millions of users an opportunity to express themselves, share their views on critical topics, help each other by giving suggestions and make friends. The messages or articles in a Usenet are transmitted in the same way the e-mails are sent. The only difference between the two is that the e-mails are restricted to their recipients but the Usenet users can access any information anytime.
Network Attached Storage, popularly known, as NAS is a file storage technology, which is used to store and manage large amount of data in a network, which can be retrieved by the clients whenever needed. It is being used in a large number of organizations now a days because of its awesome benefits.
By implementing NAS an organization can achieve the following:
- Reduced IT Staff Cost: As a NAS server can be accessed via TCP/IP network in graphical user interface (GUI) mode it does no require too many IT professionals for its management and configuration. In this way the IT staff cost is reduced to a great extent. The NAS server can be easily managed with the help of a web browser. The NAS filer is also preconfigured to facilitate specific file serving needs and thus its administration is simplified and there is reduction in the chances of operational errors too.
- Scalable without any Downtime: Business is dynamic in nature and the IT technologies are being designed in a way that they support the expansion or reduction in the current IT infrastructure easily without affecting its operational capability. NAS is also fully scalable. You can install a new filer in just 15 minutes without shutting down the whole NAS server. Advanced NAS servers also support some additional features like storage on-the-fly which eliminated the need for adding another node in the network. The users can simply access the any authorized data whenever they want. Thus NAS is also considered as a real time application.
- Specialized NAS Server: NAS servers are different from the general purpose servers. They have high computing speed and data read/write capabilities and the latency period is very less. NAS servers are optimized to handle a large number of requests simultaneously. They manage a massive amount of data with ease.
- Multi-OS Connectivity and Data-Sharing: One of the exciting advantages of Network Attached Storage is that it supports multiple operating systems and networks. NAS servers support a variety of protocols and file systems such as NFS of UNIX and CIFS of Microsoft Windows. This ensures that you can retrieve and share data on a cross-functional platform.
- Easy and Transparent Backup: The backup of the NAS filer can be taken without affecting the performance of the general purpose application servers.
- The existing network infrastructure can also be leveraged with the help of NAS. You can make better use of the current network and administration skills. Network attached Storage can be deployed anywhere in the network whenever needed without affecting the existing IT infrastructure. It can be easily amalgamated with the large and sophisticated enterprise management tools such as Microsoft Management Console (MMC), Tivoli, HP Openview etc. NAS also supports remote storage and centralized data management. You can store your data in a NAS server placed at a remote location and can manage it over the TCP/IP network from anywhere, even sitting at your home. No doubt, after implementing NAS anyone can reap higher performance from his IT infrastructure.
As discussed earlier, a cache proxy server is the one which stores the HTML documents and other web resources in its own storage space so that they can be delivered to the client without any delay.
Types of Caching
Caching can be passive as well as active. In passive caching the cache proxy server stores the web resources each time the client requests it. First of all, the cache server looks into its own database to check whether the requested resource is there or not. If it founds the desired data then there is no need to contact the web server and the data is delivered to the client instantly. If the proxy server doesn’t get the requested resource in its own database then it retrieves it from the relevant location on the internet and saves it for the future reference.
In active caching the cache proxy server stores and updates its database during its idle time. Whenever the cache server is not accessed by the clients for a set duration it learns the most frequently used resources, downloads them via internet and finally saves them in its cache for future reference. During the process of active caching the proxy server also checks for any updates regarding those resources which are already there in its database.
Challenges in Caching Process
No doubt that the cache servers incredibly reduce the latency periods and facilitate smooth data transactions, but the file caching process faces great challenges. This is not at all an easy task because the resources that have been saved in the cache server are static in nature but the web is highly dynamic and unpredictable. Sometimes a web page remains same for a long period and suddenly changes and sometimes changes are made every day. In case of real time applications such as sports and news web sites the updates are being done every second. So the cache server gets really into trouble while keeping all its records up to date so that the client doesn’t miss any single bit of information.
A large number of heuristic methods have been evolved till now and are being improved continuously in order to make the file caching more reliable and efficient. Sophisticated technologies are being implemented so that the cache server can keep its database up to date by updating the web documents and deleting the stale/expired records.
Load Balancing the Caching work
The caching can be done by implementing more than one cache proxy server and operating the whole array simultaneously. This benefits the organization in the way that the work load of caching can be shared among all the proxy servers. Thus, the caching can be done more effectively and speedily. This also increases the storage space to be used for storing HTML documents and other web applications. The whole array of cache servers can also be configured in such a way that if one cache server fails, then the remaining ones provide fault tolerance just like the Redundant Array of Inexpensive Disks (RAID).
