Network Topologies PDF

# Network Topologies ## Introduction - Two or more connected computers that share a resource such as data, a printer, an internet connection, applications, or a combination of these. - Three most common types of networks: - Local Area Network (LAN) - Metropolitan Area Network (MAN) - W...

# Network Topologies ## Introduction - Two or more connected computers that share a resource such as data, a printer, an internet connection, applications, or a combination of these. - Three most common types of networks: - Local Area Network (LAN) - Metropolitan Area Network (MAN) - Wide Area Network (WAN) ## Local Area Networks (LANs) - Consist of computers, network interface cards, peripheral devices, networking media, and network devices. - Allow businesses to locally share files and printers efficiently and make internal communication possible such as e-mail. - LANs are designed to: - Operate within a limited geographic area. - Allow many users to access high-bandwidth media. - Provide full-time connectivity to local services. - Connect physically adjacent devices. - Common LAN technologies: - Ethernet - Token Ring - FDDI - Fiber Distributed Data Interface ## Metropolitan Area Networks (MANs) - Span a metropolitan area, such as a city or a suburban area. - Connect LANs separated by distance and that are located within a common geographic area. ## Wide Area Networks (WANs) - Interconnect LANs, which then provide access to computers or files servers in other locations. - Allow businesses to communicate across great distances. - WANs have created a new class of workers called telecommuters - people who never have to leave home to go to work. - WANs are designed to: - Operate over large, geographically separated areas. - Allow users to engage in real-time communication with other users. - Provide full-time remote resources connected to local services. - Provide e-mail, World Wide Web, file transfer, and e-commerce services. ## Bus Topology - Often used when a network installation is small, simple, or temporary. - Cable is just one or more wires, with no active electronics to amplify the signal or pass it along from computer to computer. - Bus is a passive topology. - Only one computer at a time can send a message. The number of computers attached to a bus network can significantly affect the speed of the network. - Advantages: - Simple, reliable in very small networks, easy to use, and easy to understand. - Requires the least amount of cable to connect computers. - Easy to extend. ## Star Topology - Cables run from computers to a central location where they are all connected by a device called a hub. - Each computer on a star network communicates with a central hub that resends the message either to all the computers or only to the destination computer. The hub can be active or passive. - Advantages: - Easy to modify and add new computers. - Central hub is a good place to diagnose network faults. - Single computer failures do not necessarily bring down the whole network. ## Ring Topology - Each computer is connected to the next computer, with the last one connected to the first. - Every computer is connected to the next computer in the ring and retransmits what it receives from the previous computer. - Messages flow around the ring in one direction. - Ring is an active network and is not subject to the signal loss problems a bus experiences. - Some ring networks do token passing. - Token is passed around the ring until a computer wishes to send information. - Computer modifies the token, adds an electronic address and date, and sends it around the ring. - Each computer receives the token and the information and passes them to the next computer until either the electronic address matches the address of a computer or the token returns to its origin. - The receiving computer returns a message to the originator indicating that the message has been received. - The sending computer then creates another token and places it on the network, allowing another station to capture the token and begin transmitting. - Advantages: - Each computer is given equal access to the token. - Network degrades gracefully as more users are added. - Disadvantages: - Failure of one computer can affect the whole ring. - Difficult to troubleshoot. - Adding or removing computers disrupts the network. ## Mesh Topology - Distinguished by having redundant links between devices. - Each device in the network is connected via a link. - This becomes unmanageable beyond a very small number of devices. - Advantages: - Data can be transmitted from different devices simultaneously. - Withstands high traffic. - High redundancy. - Expansion and modification in topology can be done without disrupting other nodes. - Disadvantages: - High redundancy in many of the network connections. - High cost. - Difficult to set-up, maintain and administer. # Network Connectivity Devices - **Repeater:** Layer 1 device that strengthens a signal. - **Hub:** Layer 1 device, acts as a central point for devices connected to it. Data is sent by the hub to all devices connected to it. - **Bridge:** Layer 2 device, learns the MAC addresses on each side of it and uses this information to forward data packets between networks. It filters data to direct it to the correct destination. - **Switch:** Layer 2 device, uses a table of MAC addresses to determine the segment on which a frame needs to be transmitted. It can send data to multiple destinations at the same time. - **Router:** Layer 3 device, uses IP addresses to route data packets between networks. It decides the best path for the data to travel. # Network Cables - **Unshielded Twisted Pair (UTP):** Four pair wire medium composed of pairs of wires, covered with insulating material. - **Shielded Twisted Pair (STP):** Each pair of wires is wrapped in a metallic foil and the 4 pairs of wires are wrapped in an overall metallic braid to further reduce crosstalk. - **Screened Twisted Pair (SCTP):** A new hybrid of UTP. UTP is wrapped in a metallic foil shield or "screen". # Network Protocols - **TCP/IP:** The most common protocol used on the Internet, including LANs and WANs. Two separate layers: - **Transmission Control Protocol:** Assembles a message or file into smaller packets that are transmitted over the Internet. - **Internet Protocol:** Handles the address part of each packet so that it gets to the right destination. # Network Addressing - IP addresses are 32-bit numbers that are entered into a NIC's configuration parameters. - Used when multiple networks are connected together and when accessing the Internet. - IP addresses are grouped into classes and it is easy to tell which type of IP address is being issued by the first number shown in the dotted decimal notation. - Class A: 1-126 - Class B: 128-191 - Class C: 192-223 # Subnet Masks - Subnet mask is a number that the computer uses to determine which part of the IP address represents the network and which portion represents the host. # Peer to Peer Networking - Participants that make a portion of their resources available to other network participants without the need for central coordination. # Layering - Breaking down complex communications is comparable to building a car. - Layering is done step by step according to the complexity of the task. - The **OSI Reference Model** helps us understand how information travels throughout a network in a layered fashion. - Seven layers (and their function): 1. **Physical Layer:** Transmission of bits over a physical medium 2. **Data Link Layer:** Error detection and correction on the physical link. 3. **Network Layer:** Responsible for routing data packets between networks. 4. **Transport Layer:** Providing reliable and end-to-end delivery of data between two applications. 5. **Session Layer:** Manages the communication session between two applications, including connection establishment, termination, synchronization, and error recovery. 6. **Presentation Layer:** Handles different data formats and ensures that data is interpreted correctly by the receiving device. 7. **Application Layer:** Provides interface between the application programs and the network. # Importance of Layering - It simplifies network communication by breaking down complex tasks into smaller, simpler parts. - It standardizes network components, allowing for vendor independence and easier integration. # Summary - *Network Topologies* offer different ways to connect devices in a network. - *Network Connectivity Devices* are hardware components that help connect and manage network traffic (repeaters, hubs, bridges, switches, routers). - *Network Cables* are the physical medium used to transmit data between devices (UTP, STP, SCTP). - *Network Protocols* provide the rules for how devices communicate with each other (TCP/IP). - *IP Addressing* is used to identify each device on a network, and *Subnet Masks* help determine which part of the IP address represents the network and which part represents the host. - *Peer-to-peer Networking* allows devices to share resources directly without a central server. - *Layering* breaks down network functions into smaller, simpler tasks, making them easier to understand, build, and troubleshoot.