1. Instructor: Ahmed Jafer Ahmed.jafer@benghazi.edu.ly
University Of Benghazi IT Faculty Computer Networks and Communications Department Internet Programming
Instructor:
Ahmed Jafer

2. What is a Computer Network?
A collection of autonomous computers interconnected by a single technology.
Two computers are said to be interconnected if they are able to exchange information.
autonomous مستقل

3. Why Computer Networks?
Resource sharing (data, programs, equipments, etc).
Communication medium ( , net meeting, chat rooms, video conf.).
e-Commerce.
Mobile computing, wireless net. handheld, laptops).
Equipments المعدات

4. Network Scale

5. Personal Area Networks
Networks that are meant for one person.
For example, a wireless network connecting a computer with its mouse, keyboard, and printer is a personal area network.

6. Local Area Networks Because LANs are restricted in size they:
Have low delay (microseconds or nanoseconds).
Make very few errors.
Simple network management.
Speed up to 10Gbps.
restricted مقيد

7. Metropolitan Area Networks
A metropolitan area network based on cable TV.

8. Wide Area Networks
Relation between hosts on LANs and the subnet.

9. Internet
The Internet, also called the Net, is an international network that connects many thousands of networks and millions of computers across the world. Used by many people and organizations to communicate and share information, the Internet links computers of different sizes and types. 

10. Server/Client architecture
Client-server architecture can be considered as a network environment that exchanges information between a server machine  and a client machine where server has some resources that can be shared by different clients.
considered نظرت

11. Server/Client
Functions such as exchange, web access and database access are built on the client/server model. Users accessing banking services from their computer use a web browser client to send a request to a web server at a bank.

12. Server/Client Networks
A network with two clients and one server.

13. The client-server model involves requests and replies.

14. Web servers
A Web server is a program that, using the client/server model
Web servers are computers that deliver (serves up) Web pages. Every Web server has an IP address and possibly a domain name. For example, if you enter the URL  your browser, this sends a request to the Web server whose domain name The server then fetches the page named index.html and sends it to your browser.

15. Web Servers (2)
There's a common set of features that you'll find on most web servers. Because web servers are built specifically to host websites, their features are typically focussed around setting up and maintaining a website's hosting environment.
Most web servers have features that allow you to do the following:
typically عادة ما

16. Web Servers - Features
Create one or more websites. (No I don't mean build a set of web pages. What I mean is, set up the website in the web server, so that the website can be viewed via HTTP)
Configure website/directory security. For example, which user accounts are/aren't allowed to view the website, which IP addresses are/aren't allowed to view the website etc.

17. Web Servers – Features (2)
Create an FTP site. An FTP site allows users to transfer files to and from the site.
Configure/nominate custom error pages. This allows you to build and display user friendly error messages on your website. For example, you can specify which page is displayed when a user tries to access a page that doesn't exist (i.e. a "404 error").
Configure تكوين nominate ترشيح

18.  web browser
A web browser is a software application for retrieving, presenting, and traversing information resources on the World Wide Web. An information resource is identified by a Uniform Resource Identifier (URI) and may be a web page, image, video, or other piece of content Hyperlinks present in resources enable users easily to navigate their browsers to related resources. A web browser can also be defined as an application software or program designed to enable users to access, retrieve and view documents and other resources on the Internet.
Retrieving استرجاع presenting عرض traversing العبور navigate التنقل Uniform Resource Identifier معرف الموارد الموحد navigate
التنقل retrieve استرداد