Introduction to Computer Networking PDF

**University of Technology, Jamaica** School of Computing & Information Technology -------------------------------------------- **INTRODUCTION TO COMPUTER NETWORKING** **Handout \#1** COMPUTER NETWORK ================ - A communication system that allows computers to exchange information...

**University of Technology, Jamaica** School of Computing & Information Technology -------------------------------------------- **INTRODUCTION TO COMPUTER NETWORKING** **Handout \#1** COMPUTER NETWORK ================ - A communication system that allows computers to exchange information with each other in a meaningful way. - A collection of computers and devices, connected by communication channels that facilitate communications among users, and allows users to share resources with other users - Networks may link computer that are all of the same type (homogeneous), or they may link computers of several different types (heterogeneous) - Information is transmitted across computer networks in packets which are sequences of bits containing both signaling information and user data, each packet being no greater than a maximum length determined by the network. ###### Advantages (See Fig 1.0 Below) - Facilitates communication - Sharing hardware - Sharing data & information - Sharing software - High reliability (in the event of failures) - Saving money - Fig 1.0 CATEGORIES OF COMPUTER NETWORK ============================== 1\. Local Area Network (LAN) - Offers high speed communication (order of 10mb/s) between computers situated within a limited area, typically a building or small site. - In general a low error rate can be achieved, all computers are connected to a single transmission medium and access to the medium is controlled in a distributed manner with all the computers working to agreed rules. - Each computer or device on the network is called a node. Often, nodes are connected to the network via cables - Usually owned and managed by a single organization. - Have three (3) characteristic features: 1. A diameter of not more than a few kilometers 2. A total data rate of at least several Mbps 3. Complete ownership by a single organization 2\. Wide Area Network (WAN) - Most WANs connect computers within a single country, but others (for example SITA which serves the international airline organizations) cover many countries using a communications channel that combines many types of media such as telephone lines, cables and airwaves. - The Internet is the world's largest WAN. - Has the following characteristic features: 1. Span greater distances than LANs. Typically span entire countries 2. Have much lower data rates usually under 1 Mbps 3. Owned by multiple organizations 4. WANs can be connected on demand or permanently connected; LANs have permanent connections between stations 5. WANs can use public or private network transports; LANs primarily use private network transports. 3\. Metropolitan Area Network (MAN) - Covers an area of the size of a typical city, but uses LAN technology. - They offer a simple, fast way to link different organizations for the exchange of information. NETWORK TOPOLOGIES ================== - Computers can be connected together in many different ways. - The layout or topology of the network will influence how reliable the network is and how easy it is to access. - The main physical topologies include wired or wireless networks. The main physical wired topologies are: Star, ring, bus, with many other derivatives **Star Topology**  All devices are connected to a central device called a hub by a separate cable. Nodes communicate across the network by passing data through the hub. **Advantages include:** - New stations can be added easily and quickly - A single cable failure won't bring down the entire network - It is relatively easy to troubleshoot **Disadvantages include:** - Total installation cost may be higher than that for a bus network because of the larger number of cables, but prices are constantly becoming more and more competitive. - It has a single point of failure **Ring Topology** All devices are connected to one another in the shape of a closed loop, so that each device is connected directly to two other devices, one on either side of it. Data is transmitted on a ring network from device to device **around the entire ring**, in one direction. When a computer sends data, the data travels to each computer on the ring **until it reaches its destination**. **Advantages: ** - Growth of system has minimal impact on performance - Each node (or workstation) in the network is able to purify and amplify the data signal before sending it to the next node, therefore introducing less signal loss as data travels.  - Can cover larger geographical areas where star implementations would be difficult.  - A break anywhere in the n/w shuts down the entire network.  - Most expensive topology - Failure of one computer may impact others - Non-destination users may access data passing around the network when it reaches his/her computer. - Difficult to add or subtract a station without brining down the entire network (physical ring topology is hardly ever used) **Bus Topology** All devices are connected to **a single central cable**, called the bus or backbone. Using the bus and a destination address, data is transmitted from the source device to the destination device (all along the single cable). **Advantages: ** - Bus topology is inexpensive and easy to install. You can attach & detach devices to the network at any point without affecting the rest of the network. - Failure of one device usually doesn't affect the rest of the network. - The transmission simply bypasses the failed device.  - Requires less cabling than a star network.  **Disadvantages: ** - Entire n/w shuts down if there is a break in the main cable.  - Terminators are required at both ends of the backbone cable.  - Difficult to identify the problem if the entire network shuts down.  - Not meant to be used as a stand-alone solution to cover a large building.  **Mesh Topology**  Devices are connected with many redundant interconnections between network nodes. In a true mesh topology every node has a connection to every other node in the network. **Tree Topology** A hybrid topology. Groups of star-configured networks are connected to a linear bus backbone. NETWORK PROTOCOLS ================= - Each type of computer system has its own method of storing information and interfacing to the outside world. - A protocol defines the rules of procedure, which computers must obey when communicating with each other. - At the basic level protocols define when and how packets shall be transmitted onto the network; these access protocols allow for the fundamental exchange of information. - At a higher level, an agreed character code must be used and the information must be interpreted by the appropriate application software. - Communicating computers must follow rules in order to convey useful information. - The following list indicates some of the requirements which have to be resolved for a point to point link between two computers: 1. The order of progress must follow an agreed procedure. 2. Information representation (Eg. a character) must be agreed. 3. The recipient must be able to check that the information has arrived at its destination in the order and the format in which it was sent, and must detect missing or duplicated pieces. 4. The recipient may have to acknowledge information that has been received correctly and indicate any errors that have occurred in order for the source to retransmit information. 5. The source should be prevented from flooding the destination with information, but the link should be used efficiently and deadlocks should be prevented. 6. Packets belonging to each of several conversations on the same link must be identified correctly. ##### Layering of Protocols **Protocol functions** Protocols are used to improve (and standardize) the communication process between two computers of different manufacturers. A protocol is **a set of** conventions or **rules** that the computers must follow to complete a data communication task. 1. Starting the communication - Identify which computers are "hosts" & which are "slaves" - Whether communication starts automatically - Identify which computers are allowed to communicate 2. Character identification - Rules for identifying frames of characters - Rules for identifying characters in frames 3. Message control - Frames (of several messages) may arrive (at the receiver) at random and must be assembled in order before being passed on to the user. 4. Error control - Rules for identifying electrical signals on the lines (transmission media) and provide feedback to the sender. 5. Ending the communication - Rules for terminating (normally & abnormally) communication between two computers. NETWORK NAVIGATION DEVICES ========================== Network devices, or networking hardware, are physical devices that are required for communication and interaction between hardware on a computer network. **Network Interface Card (NIC)** A network interface card (NIC) is a hardware component, typically a circuit board or chip, which is installed on a computer so it can connect to a network. Modern NICs provide functionality to computers, such as support for I/O interrupt, direct memory access (DMA) interfaces, data transmission, network traffic engineering and partitioning. **Hub** Hubs are used to connect multiple network devices together. They can be used to transmit both digital and analog information. Digital information is transmitted as packets, whereas analog information is transmitted as a signal. Hubs also act as a repeater, which amplifies signals that have weakened after being transmitted across a long distance. Hubs operate at the Physical layer of the Open Systems Interconnection (OSI) model. **Switch** A switch is a multiport network device whose purpose is to improve network efficiency and improve communication between hubs, routers, and other network devices. Switches are intelligent devices that gather information from incoming packets in order to forward them to the appropriate destination. Switches generally have limited information about the other nodes on the network. **Access Point (AP)** An access point is a transceiver device that connects wireless and ethernet LAN. It has a transmitter, receiver, and built-in antenna, allowing it to create a wireless LAN. An AP typically has multiple ports for network expansion or to support more endpoint devices. Its transmission range depends upon the environmental conditions and obstructions between the wireless client and AP. Multi-port APs can also operate as a switch, firewall, and DHCP server in a network. **Router** A router is popular networking hardware that can connect two network segments or subnets to create an extensive network. As a network layer device, the router collects and stores information such as the IP address of its connected devices in a routing table and uses it for packet forwarding to the right destination. Routers can operate with static and dynamic routing. Static routing requires manual configuration and is less effective in dynamic networks. In contrast, dynamic routing allows routers to exchange information with other routers using special routing protocols and identify the most optimal path for data transfer. **Firewall** A Firewall is a network security device that monitors and filters incoming and outgoing network traffic based on an organization's previously established security policies. At its most basic, a firewall is essentially the barrier that sits between a private internal network and the public Internet. A firewall's main purpose is to allow non-threatening traffic in and to keep dangerous traffic out. WIRED ETHERNET STANDARDS ======================== IEEE 802.3 is a set of standards put forth by the Institute of Electrical and Electronics Engineers (IEEE) that define Ethernet-based networks as well as the name of the working group assigned to develop these standards. IEEE 802.3 is otherwise known as the Ethernet standard and defines the physical layer and the media access control (MAC) of the data link layer for wired Ethernet networks, generally as a local area network (LAN) technology. **Ethernet Cable Category** The \"Cat\" in Cat5e, Cat6, etc. is short for \"Category.\" Network cables are divided into categories based mainly on bandwidth (measured in MHz), maximum data rate (measured in megabits per second) and shielding. **Cat 1:** For a time, this unshielded twisted pair (UTP) cable was the most common form of wiring for voice telephone systems in homes and offices. It consisted of two insulated copper wires twisted around each other and was designed for analog voice communications. **Cat 2:** Category 2 cabling was capable of voice and data communications and was primarily used during the 1980s for IBM Token Ring networks. It supported a data transmission rate of 4 Mbps. **Cat 3:** Introduced in the early 1990s, Category 3 cabling had four twisted pairs and was the first to support 10BaseT Ethernet networks as well as digital voice communications. It is still found in older buildings but its 10 Mbps data rate is considered too slow for modern networking. **Cat 4:** Like Cat3, Category 4 cable is typically found in older buildings where the cost of complete replacement is prohibitive. It had a data rate of 16 Mbps and was primarily used for IBM Token Ring networks. **Cat 5:** Introduced in 1995, Category 5 cable has a data rate of up to 100 Mbps. It is used for standard 10BaseT and 100BaseT (Fast Ethernet) networks, and can distribute data, video and telephone signals at distances up to 100 meters (328 ft.). Cat5e is not an official designation but is used by manufacturers to describe an enhanced Cat5 cable that is capable of speeds up to 1 Gbps. Its higher data rate is achieved by increasing the number of twists, making it more resistant to crosstalk. Cat5e is recommended for new sub-Gigabit network installations. **Cat 6:** In comparison to Cat5e, Cat6 cable provides greater bandwidth and data transfer rates up to 1 Gbps over 100 m, the same as Cat5e. However, at shorter distances of up to 37 m (121 ft.), Cat6 is able to achieve 10 Gbps speeds thanks to its improved shielding and higher bandwidth. Cat6 includes a physical separator called a \"spline\" between the four pairs to reduce crosstalk and foil shielding to reduce electromagnetic interference. Cat6 cabling is backward compatible with the Cat5/5e standard. Introduced in 2009, Cat6a is an \"augmented\" Category 6 cable with a bandwidth of up to 500MHz. **Cat 7:** The Cat7 specification is a proprietary standard developed by a consortium of companies and is not endorsed by IEEE or TIA/EIA. While substantially similar to the performance characteristics of Cat6a, Cat7 cables features proprietary GG45 connectors and robust shielding. Cat7a (Category 7 Augmented) is a further refinement of Cat7, capable of 40 Gigabit speeds over 50 meters and 100 Gbps up to 15 meters. The proprietary nature of the Cat7 and Cat7a standards and lack of support from IEEE and EIA has resulted in a relatively small installed based for Cat7/Cat7a. **Cat 8:** With a bandwidth of up to 2 GHz (2000 MHz) over 30 meters and a data rate of up to 40Gbs, Cat8 cable is ideal for switch-to-switch communications in a 25GBase T or 40GBase T network. Its conductors are wrapped in foil to virtually eliminate crosstalk and enable higher data rates. The result is a heavier gauge cable that is quite rigid and can be difficult to install in tight spaces. It still uses RJ45 connectors and is backwards compatible with previous standards. ---------------------------------------------------------------------------------------------------------------------------------------- **Category** **Max. Data Rate** **Bandwidth** **Max. Distance** **Usage** -------------- -------------------- --------------- ------------------------ ----------------------------------------------------------- Category 1 1 Mbps 0.4 MHz   Telephone and modem lines Category 2 4 Mbps 4 MHz   LocalTalk & Telephone Category 3 10 Mbps 16 MHz 100 m (328 ft.) 10BaseT Ethernet Category 4 16 Mbps 20 MHz 100 m (328 ft.) Token Ring Category 5 100 Mbps 100 MHz 100 m (328 ft.) 100BaseT Ethernet Category 5e 1 Gbps 100 MHz 100 m (328 ft.) 100BaseT Ethernet, residential homes Category 6 1 Gbps 250 MHz 100 m (328 ft.)\ Gigabit Ethernet, commercial buildings 10Gb at 37 m (121 ft.) Category 6a 10 Gbps 500 MHz 100 m (328 ft.) Gigabit Ethernet in data centers and commercial buildings Category 7 10 Gbps 600 MHz 100 m (328 ft.) 10 Gbps Core Infrastructure Category 7a 10 Gbps 1000 MHz 100 m (328 ft.)\ 10 Gbps Core Infrastructure 40Gb at 50 m (164 ft.) Category 8 25 Gbps (Cat8.1)\ 2000 MHz 30 m (98 ft.) 25 Gbps/40 Gbps Core Infrastructure 40 Gbps (Cat8.2) ---------------------------------------------------------------------------------------------------------------------------------------- NETWORK CONNECTORS ================== A device that eliminates a section of cabling or implements a state of access for network devices, including PCs, hubs, and switches. Connectors can be famous for their physical presentation and mating features, including jacks and attachment (male connectors) or attachments and ports (female connectors). Connectors are used to connect the guided (wired) transmission media to devices like the hub, server, workstations etc. **Bayonet Neill--Concelman (BNC)** BNC connector is a type of connector used with coaxial Ethernet cable. The connector is bayonet-style, meaning that it is put in then turned and locked in position. This connector is commonly used on a Token Ring network. BNC is also called the Bayonet Nut Connector or British Naval/Navy Connector although more appropriately known as the Bayonet Neill-Concelman. Below is an example of a BNC connector. In the picture two BNC cables are connecting to a BNC splitter. **Registered Jack (RJ)** RJ Cable allows network devices to communicate with voice and data equipment. It is primarily used to link various types of data equipment and telecommunication media in order to make use of services provided by local service providers, who in turn use it to exchange data across larger distances and with shorter exchange carriers. These RJ cables are classified based on their structure and purposes, such as size, PIN number, and compatibility.