The UOC's Educational Intranet
 

 

 

Architecture of I-Campus

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Diagram of the architecture of the Educational Intranet of the UOC

 

Browser: This is an Internet browser. An example is Netscape or Internet Explorer.

Proxy Server: This server is in charge of centralising the traffic between the Internet and the UOC network, in order to avoid the obligation for the machines of the UOC to have a direct connection to the Internet. At the same time, it contains safety mechanisms to impede any non-authorised external accessThis server is in charge of centralising the traffic between the Internet and the UOC network, in order to avoid the obligation for the machines of the UOC to have a direct connection to the Internet. At the same time, it contains safety mechanisms to impede any non-authorised external access.

Example: One of the machines in the UOC network which uses a customer software, like a browser (Explorer, Netscape...) and needs to visit an Internet address. As there is no direct connection, the request is passed on to the proxy server, which will accede to the page requested and return it to the machine making the request.

Web Server: This is in charge of storing and delivering Web pages. In the case of the Educational Intranet, it contains the static pages (they are fixed pages with a type of content which does not vary).

Analogy: When you go to a video club in order to borrow a film, at first you can only take the box. When you are ready to pay for the service, the person attending you will look for the relevant cassette in the store-room and give it to you (in an analogous way, the person and the store-room would be the static-page server).

Intranet Daemon : This is the service managing the Intranet's dynamic information (in other words, information subject to variation).

One of the challenges in Internet development is in the method of executing processes. If a service is of a CGI* type, each click a user makes with the mouse generates a process, and the performance of the hardware, as can be imagined, becomes very low. The UOC's Intranet Daemon executes processes by threads (multiple synchronous executions under a single process sharing resources such as the memory and data), so that a process can give rise simultaneously to a great number of clicks from various users. In memory and data sharing, if a user needs the same information as another who is part of the same process, he or she does not need to seek the information at its source, as it has already been obtained and is therefore immediately available.

Analogy: Sorting books in a library
Five books enter a library every minute. In the case of CGI, the librarian waits at the door, collects one book, goes up the ladder and places the book on the shelf. With Intranet Daemon, the librarian collects the five books at the same time, and goes up the ladder and places them on the shelf in one operation, and takes advantage of the action of going up the ladder to sort them all at the same time.

Cluster of services: this is the application containing the business rules (all the norms of an application) of the UOC Intranet, sorted and organised according to services. They are accessible and inter-operational by means of a standard protocol named IIOP, which is a part of CORBA (a computing solution open to the connection of applications on different platforms).

The IIOP standard can be used from various applications and allows you to call for a service independently of the visual design and the business logic applied to it. The cluster of services allows changes in this business logic without affecting the use of the Campus, as its architecture is divided up into services - before, it used to be monolithic.

Developments have been made in Java, a programming language which has advantages and disadvantages. The following are its main advantages:

Easy re-use.

Integration into the Internet.

Flexible language.

Independence from the operating system (as programming is done through Java's virtual machine).

The most important disadvantages are:

Low performance of virtual machines, as little work has been done on its technology.

A young and rapidly-evolving language, which forces one to adapt oneself to it constantly.

Analogy. Let us imagine a house which we shall name "cluster of services". Its different rooms -dining-room, kitchen, dormitories- would constitute the business logic, in other words, the structure of the house. And the gas and light services, for example, would be those offered by the "house" cluster of services. In this case, we could carry out a renovation of part of the electrical installation of the whole house without affecting either its structure (the business logic) or the distribution of spaces.

 

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mirador@uoc.edu       © FUOC 2001       Last updated data: 20.10.03
Browser Browser Browser Web Server Intranet Daemon Cluster of services