Computer Networks PDF Lecture Notes

Dr./ Abeer Saber 1 2  Computer Network Components Network Interface Card (NIC) Hub Switch Router Modem 3  Network Interface Card (NIC) is a hardware component used to connect a computer with another computer onto a network. 4  Hub is a hardw...

Dr./ Abeer Saber 1 2  Computer Network Components Network Interface Card (NIC) Hub Switch Router Modem 3  Network Interface Card (NIC) is a hardware component used to connect a computer with another computer onto a network. 4  Hub is a hardware device that divides the network connection among multiple devices. When computer requests for some information from a network, it first sends the request to the Hub through cable. Hub will broadcast this request to the entire network. 5  Switch is a hardware device that connects multiple devices on a computer network. A Switch contains more advanced features than Hub. 6  Router is a hardware device which is used to connect a LAN with an internet connection. It is used to receive, analyze and forward the incoming packets to another network. 7  Modem is a hardware device that allows the computer to connect to the internet over the existing telephone line. 9  Repeaters are defined as a networking device that is used to amplify and generate the incoming signal. Repeaters work at the physical layer of the OSI model. The main aim of using a repeater is to increase the networking distance by increasing the strength and quality of signals. 10 11  A firewall is a network security device, either hardware or software-based, which monitors all incoming and outgoing traffic and based on a defined set of security rules it accepts, rejects or drops that specific traffic. Accept : allow the traffic Reject : block the traffic but reply with an “unreachable error” Drop : block the traffic with no reply A firewall establishes a barrier between secured inter nal networks and outside untrusted network, such as the Internet. 12 13  Servers are computers that runs operating system and hold data that can be shared over a computer network. A client is a computer that is connected to other computers in the network and can receive data sent by other computers. 14  Here’s a list of common dedicated servers: File Server: Stores and dispenses files. Mail Server: The network’s post office; handles email functions. Print Server: Manages printers on the network. 15  Web Server: Manages web-based activities by running Hypertext Transfer Protocol (HTTP) for storing web content and accessing web pages. Fax Server The “memo maker” that sends and receives paperless faxes over the network. 16  A p p l i c at i o n S e r ve r M a n a g e s n e t wo r k applications. Telephony Server Handles the call center and call routing and can be thought of as a sophisticated network answering machine. Proxy Server Handles tasks in the place of other machines on the network, particularly an Internet connection. 17  IEEE Institute of Electrical and Electronics Engineers, an organization dedicated to advancing innovation and technological excellence for the benefit of humanity, is the world's largest technical professional society. It is designed to serve professionals involved in all aspects of the electrical, electronic, and computing fields and related areas of science and technology that underlie modern civilization. 18  The IEEE standards in computer networks ensure communication between various devices; it also helps to make sure that the network service, i.e., the Internet and its related technologies, must follow a set of guidelines and practices so that all the networking devices can communicate and work smoothly. 19  Ethernet is the traditional technology for connecting devices in a wired local area network (LAN) or wide area network. It enables devices to communicate with each other via a protocol, which is a set of rules or common network language. Ethernet describes how network devices format and transmit data so other devices on the same LAN or campus network can recognize, receive and process the information. An Ethernet cable is the physical, encased wiring over which the data travels 20 21 22  Network media is the actual path over which an electrical signal travels as it moves from one component to another. The common types of network media, including twisted-pair cable, coaxial cable, fiber-optic cable, and wireless. 23  1- Coaxial Cable 24  1- Coaxial Cable Coaxial cable sometimes known as coax cable, is an electrical cable which transmits radio frequency (RF) signals from one point to another. It contains a center conductor made of copper that’s surrounded by a plastic jacket with a braided shield over it. 25  Communication Media Coaxial cable: Is widely used for cable television systems, office buildings, and other work-sites for local area networks. Consists of copper or aluminum wire wrapped with insulating layer.  2- Twisted-Pair Cable 27  2- Twisted-Pair Cable Twisted-pair cable consists of multiple individually insulated wires that are twisted together in pairs. 28  2.3- Straight Through Cable A straight through cable is a type of twisted pair cable that is used in local area networks. This type of cable is also sometimes called a patch cable. 29  2.3- Straight Through Cable Straight through cable is an alternative to wireless connections where one or more computer s access a router through a wireless signal. It is used to 30 connect different type of devices.  2.3- Straight Through Cable 31  2.4- Crossover Cable Cross over or swap on its way when coming from one end to the other. Unlike patch cable, crossover cable uses two different wiring standards on both end. 32  Straight-through cables are used to connect devices that operate at different layers of the network model, such as a computer. And a switch or a switch and a router. Crossover cables are utilised to link devices operating. At the network model's same layer, such as two computers, switches, or routers 33 34  2.5- Rolled Cable Rollover cable also known Console cable is a cable that is used to connect a computer terminal to a router's console port. This cable is typically flat (and has a light blue color) to help distinguish it from other types of network cabling. 35  2.5- Rolled Cable 36  2.5- Rolled Cable 37  3- Fiber Optic 38  3- Fiber Optic Fiber-optic cable transmits digital signals using light impulses rather than electricity, it’s immune to EMI and RFI. Fiber cable allows light impulses to be carried on either a glass or a plastic core. Glass can carry the signal a greater distance, but plastic costs less. 39  3- Fiber Optic A fiber-optic cable contains anywhere from a few to hundreds of optical fibers within a plastic casing. Also known as optic cables or optical fiber cables, they transfer data signals in the form of light and travel hundreds of miles significantly faster than those used in traditional electrical cables. 40  3- Fiber Optic 41  Wireless Technologies Bluetooth Bluetooth enables a variety of devices, including cell phones, PDAs, wireless keyboards and mice, PCs, and printers. Links up to 8 devices in 10-m area  Wireless Technologies Wi-Fi Used for wireless LAN and wireless Internet access Use access points: Device with radio receiver/transmitter for connecting wireless devices to a wired LAN Weak security features  Half-duplex Ether net is defined basically, when you run half duplex, you’re using only one wire pair with a digital signal either transmitting or receiving. 44  Full-duplex Ethernet uses two pairs of wires at the same time instead of one measly wire pair like half duplex employs. Yo u d o n ’ t n e e d t o w o r r y a b o u t collisions because now it’s like a freeway 45 46  These important points: There are no collisions in full-duplex mode. A dedicated switch port is required for each full-duplex host. The host network card and the switch port must be capable of operating in full-duplex mode. 47 48 49 50  The cast term here signifies some data(stream of packets) is being transmitted to the recipient(s) from the client(s) side over the communication channel that helps them to communicate. Let’s see some of the “cast” concepts that are prevailing in the computer networks field. 51 52 53