Computer Networking - Lec 3 PDF

Network Cables and Interfaces Dr. Enas Elgeldawi  Cables used as Physical Transmission Medium Ethernet Cables Twisted Pair Coaxial Fiber Optic UTP STP Single mode Multi Mode Cables used as Physi...

Network Cables and Interfaces Dr. Enas Elgeldawi  Cables used as Physical Transmission Medium Ethernet Cables Twisted Pair Coaxial Fiber Optic UTP STP Single mode Multi Mode Cables used as Physical Transmission Medium Types of cables used as transmission medium are twisted pair, cable coaxial cable, fiber optic cable. Twisted Pair Cable  Twisted pair cable consists of pairs of insulated copper wires twisted together  There are two types of twisted pair cables shielded twisted pair cable and unshielded twisted pair cable. Advantages of twisted pair cable:  Twisted pair cables are cheaper  they are flexible  they are light in weight and  easy to install  UTP STP Unshielded Twisted Pair Shielded Twisted Pair Cables used as Physical Transmission Medium Coaxial Cable  A coaxial cable is an insulated copper cable used to carry high frequency data signals such as voice images videos and text.  the coaxial cable has a conductor placed in center surrounded by multiple protective shields and an outer jacket that ensure noise and distortion free transmission of high frequency data. Advantages of coaxial cable:  can transmit data much faster than twisted pair cables  they are less prone to noise Coaxial Cables used as Physical Transmission Medium Fiber Optic Cable  Fiber optics cable consists of hair like strands of glass or any transparent material which can pass light at high quality to carry light signals.  It can also send and receive a wide range of data frequencies at a speed matching to the speed of light.  Fiber optic cables are made up of three components transmitter, receiver and the cable.  The transmitter transform electrical signals into light waves.  The cable used as a medium for carrying light waves.  The receiver receives the light signals and converts them into electrical signals. Advantages of fiber optic cable fiber:  Provides high bandwidth over long distance.  Super fast transmission. Fiber Optic  Cables used as Transmission Medium Ethernet Cables Twisted Pair Coaxial Fiber Optic UTP STP Single mode Multi Mode UTP: Unshielded Twisted Pair RJ-45 Connector RJ = Registered Jack UTP: Unshielded Twisted Pair In the mid-1980s, the TIA (Telecommunications Industry Association) and the EIA (Electronic Industries Association) began developing methods for cabling buildings, with the intent of developing a uniform wiring system that would support multivendor products and environments. In 1991, the TIA/EIA released the TIA/EIA 568 Commercial Building Telecommunication Cabling standard. Note that the ISO/IEC-11801 Generic Customer Premises Cabling standard is an international cabling standard that is based on the ANSI/TIA/EIA-568 cabling standard. UTP: Unshielded Twisted Pair Twisted Ethernet cables connect devices, such as computers, routers, switches, and servers, and enable data transmission between them. But not all Ethernet cables are the same. The twist actually helps protect against eletromagnetic interference, or EMI. So, there are four pairs of wires twisted together, that makes eight wires in total. Depending on the type of devices and the network configuration, There are 2 types of Ethernet cables, straight-through or crossover cables. Twisted Ethernet cables are comprised of four twisting pairs of wires, each with a different color: orange, green, blue, and brown. Each pair consists of a solid-colored wire and a white wire with a stripe of the same color. These wires are arranged in a specific order and terminated with an RJ-45 connector at each end. The RJ-45 connector has eight pins, numbered from 1 to 8, that correspond to the wires in the cable. Twisted Ethernet cables transmit data using electrical signals. Each pair of wires carries a positive or negative signal that represents a binary digit (0 or 1). The signal is sent from the transmitter (TX) of one device to another device’s receiver (RX). The TX and RX pins are assigned to different pairs of wires depending on the speed and standard of the Ethernet cable. For example, for 10BASE-T and 100BASE- TX Ethernet, which operate at 10 Mbps and 100 Mbps, respectively, the TX hooks are 1 and 2, and the RX pins are 3 and 6. For 1000BASE-T Ethernet, which operates at 1 Gbps, the TX pins are 1, 2, 3, and 4, and the RX pins are 5, 6, 7, and 8. UTP: Unshielded Twisted Pair UTP Straight Through Crossover Straight Through Crossover Straight-Through Cables Straight-through cables are the most common type of Ethernet cables. They 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. In a straight-through cable, the wires are arranged in the same order at both ends of the cable. This means that one device’s TX pins are connected to another device’s RX pins and vice versa. For example, pin 1 of one end is connected to pin 1 of the other rear, pin 2 to pin 2, and onwards. The standard wiring scheme for straight-through cables is called T568A, which follows this order of wires from left to right: white-green, green, white-orange, blue, white-blue, orange, white- brown, and brown. Another wiring scheme, called T568B, swaps the positions of the orange and green pairs, resulting in this order: white-orange, orange, white-green, blue, white-blue, green, white-brown, brown. Both schemes are functionally equivalent as long as the same scheme is used at both ends of the cable. Crossover Cables Crossover cables link devices operating at the same layer of the network model, such as two computers, switches, or routers. In a crossover cable, the wires are placed in a different order at each end of the cable. This means that the TX pins of one device are connected to the TX pins of another device, and the RX pins are connected to the RX pins. For example, pin 1 of one end is connected to pin 3 of the other end, pin 2 to pin 6, and so on. The standard wiring scheme for crossover cables is a combination of T568A and T568B, which follows this order of wires from left to right at one end: white-green, green, white-orange, blue, white-blue, orange, white-brown, brown. And this order at the other end: white-orange, orange, white-green, blue, white-blue, green, white-brown, brown. By reversing the positions of the orange and green pairs, the crossover cable ensures that the TX and RX pairs are swapped between the devices. Key Differences Between Straight-Through vs. Crossover Cables The main difference between straight-through vs. crossover cables is how they connect the devices’ TX and RX pins. Straight-through cables connect the TX pins of one device to the RX pins of another device, while crossover cables connect the TX pins of one device to the TX pins of another device. This difference affects the purpose and scenarios where each type of cable is used. 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. This is because these devices have different roles and functions in the network and need to communicate using different signals. For example, a computer sends data to a switch using the TX pins, and the switch forwards the data to another device using the RX pins. Crossover cables are utilized to link devices operating at the network model’s same layer, such as two computers, switches, or routers. This is because these devices have similar roles and functions in the network, and they need to communicate with each other using the same signals. For example, two computers send and receive data to each other using the TX and RX pins. A crossover cable ensures that the data is exchanged between the devices without interference or confusion. Auto-MDIX and Its Impact Auto-MDIX (Automatic Medium-Dependent Interface Crossover) is a feature that allows network devices to detect and adjust the cable type and pin configuration automatically. With Auto-MDIX, you do not need to worry about choosing the right cable type for your network setup. As the devices will automatically configure themselves to use either straight-through or crossover cables. Auto-MDIX is supported by most modern network devices, such as switches, routers, and network cards. However, it is still important to understand the differences between straight-through. And crossover cables, as some older devices may not support Auto-MDIX or be disabled by default. In such cases, you will need to use the appropriate cable type for your network configuration or enable Auto-MDIX on your devices if possible.