Network Topologies PDF

IT2203 Network Reference Models Network Topologies (Huawei, 2022) It is a schematic description of a network arrangement, connecting various nodes (sender and receiver) through lines of connection. Star Topology – in this type of topology, the computers are connected to a si...

IT2203 Network Reference Models Network Topologies (Huawei, 2022) It is a schematic description of a network arrangement, connecting various nodes (sender and receiver) through lines of connection. Star Topology – in this type of topology, the computers are connected to a single hub through a cable. This hub is the central node while all other nodes are connected to it. o Advantages: New nodes can be easily added to the network. Communication data must be forwarded by the central node, which facilitates network monitoring. o Disadvantages: Faults on the central node affect the entire network's communication. Bus Topology – a network type in which every computer and network device is connected to a single cable. When it has exactly two (2) endpoints, then it is called Linear Bus Topology. All nodes are connected through a bus (ex. coaxial cable). o Advantages: The installation is simple and cable resources are saved. Generally, the failure of a node does not affect the communication of the entire network. o Disadvantages: A bus fault affects the communication of the entire network. The information sent by a node can be received by all other nodes, resulting in low security. Ring Topology – forms a ring as each computer is connected to another computer, with the last one (1) connected to the first—exactly two (2) neighbors for each device. o Advantages: Cables resources are saved. o Disadvantages: It is difficult to add new nodes. The original ring must be interrupted before new nodes are inserted to form a new ring. Tree Topology – has a root node and all other nodes are connected to it forming a hierarchy. It is also called hierarchical topology. It should at least have three (3) levels to the hierarchy. o Advantages: Multiple star networks can be quickly combined, facilitating network expansion. o Disadvantages: A fault on a node at a higher layer is more severe. Mesh Topology – a point-to-point connection to other nodes or devices. All the network nodes are connected. o Partial Mesh Topology – in this topology, some systems are connected in the same fashion as mesh topology, but some devices are only connected to two (2) or three (3) devices. ▪ Advantages: The cost of a partial-mesh network is lower than that of a full-mesh network. PARTIAL ▪ Disadvantages: The reliability of a partial-mesh network is lower than that of a full-mesh network. o Full Mesh Topology – each node or device is connected. ▪ Advantages: It has high reliability and high communication efficiency. ▪ Disadvantages: Each node requires a large number of physical ports and interconnection cables. As a result, the cost is high, and it is difficult to expand. FULL 02 Handout 1 *Property of STI  [email protected] Page 1 of 5  IT2203 Hybrid Topology – it consists of a mix of two (2) different types of topologies merging as one network. o In actual networking, multiple types of topologies may be combined based on the cost, communication efficiency, and reliability requirements. Common Network Devices (Huawei, 2022) Terminal device It is the end-device of the data communication system. It provides the necessary functions required by the user access protocol operations. This includes data terminal equipment (DTE) such as a PC, phone, handsets, printers, and servers. A network interface card (NIC) is a key component that connects directly to a device that allows access to a network such as an internet or a local network. Switch It is the device closest to end-users, used to access the network and switch data frames. Switches belonging at the access layer are usually Layer 2 switches, also known as Ethernet switches. A broadcast domain is a set of nodes that can receive broadcast packets from a node. The Ethernet switch can implement the following functions: o Data frame switching o Access to end-user devices o Basic access security functions o Layer 2 link redundancy. Router It is a network-layer device that forwards data packets on the Internet. A modem is a device that connects a network to the Internet. It takes signals from your Internet service provider (ISP) and translates them into signals connected to the local devices. Gateway is a term for a router that provides functions such as protocol conversion, route selection, and data exchange when networks using different architectures or protocols communicate with each other. Firewall It is a network security device used to ensure secure communication between two networks. o It monitors, restricts, and modifies data flows passing through it to shield information, structure, and running status of internal networks from the public network o It is located between two (2) networks with different trust levels (for example, between an intranet and the Internet). o It controls the communication between the two networks and forcibly implements unified security policies to prevent unauthorized access to important information resources. 02 Handout 1 *Property of STI  [email protected] Page 2 of 5  IT2203 Wireless Devices It is a network that uses radio waves, laser, and infrared signals to replace some or all transmission media in a wired LAN. Common Wi-Fi is a WLAN technology based on the IEEE 802.11 family of standards. o Fat Access Point (Fat AP) applies to homes. It works independently and needs to be configured separately. It has simple functions and low costs. o Fit Access Point (Fat AP) applies to medium- and large-sized enterprises. It needs to work with the AC and is managed and configured by the AC. o Access Controller (AC) is generally deployed at the aggregation layer of the entire network. The AC provides wireless data control services featuring large capacity, high performance, high reliability, easy installation, and easy maintenance. Networking based on Geographical Coverage Local Area Network (LAN) o A LAN generally covers an area of a few square kilometers. o The main function is to connect several terminals that are close to each other (within a family, within one or more buildings, within a campus, for example). Technologies used: Ethernet and Wi-Fi. Metropolitan Area Network (MAN) o A MAN is a large-sized LAN, requiring high costs but can provide a higher transmission rate. It improves the transmission media in LANs and expands the access scope of LANs (able to cover a university campus or city). o The main function is to connect hosts, databases, and LANs at different locations in the same city. o Technologies used: Ethernet (10 Gbit/s or 100 Gbit/s) and WiMAX. Wide Area Network (WAN) o A WAN generally covers an area of several kilometers or larger (thousands of kilometers for example). o It is mainly used to connect several LANs or MANs that are far from each other (for example, across cities or countries). Telecom operators' communication lines use HDLC and PPP. 02 Handout 1 *Property of STI  [email protected] Page 3 of 5  IT2203 OSI Reference Model (Huawei, 2020) The Open Systems Interconnection (OSI) model is a descriptive network scheme. The OSI model describes how information or data makes its way from application programs through a network medium to another application program located on another network. LAYER 7: APPLICATION LAYER is the OSI layer that is closest to the user. It provides network services to the user’s applications such as spreadsheet programs, word processing programs, and bank terminal programs. o The application layer establishes the availability of intended communication partners, synchronizes, and establishes agreement on procedures for error recovery and control of data integrity. LAYER 6: PRESENTATION LAYER ensures that the information that the application layer of one (1) system sends out is readable by the application layer of another system. o If necessary, the presentation layer translates between multiple data formats by using a common format. Provides encryption and compression of data. Examples: JPEG, MPEG, ASCII, HTML. LAYER 5: SESSION LAYER defines how to start, control and end conversations (called sessions) between applications. It also synchronizes dialogue between two (2) hosts’ presentation layers and manages their data exchange. LAYER 4: TRANSPORT LAYER regulates information flow to ensure end-to-end connectivity between host applications reliably and accurately. This layer segments data from the sending host’s system and reassembles the data into a data stream on the receiving host’s system. LAYER 3: NETWORK LAYER defines end-to-end delivery of packets. It defines how routing works (identifying endpoints) and how routes are learned so that the packets can be delivered. o The network layer defines how to fragment a packet into smaller packets to accommodate different media. Examples: Routers operate at Layer 3 - IP, IPX, AppleTalk. LAYER 2: DATA LINK LAYER provides access to the networking media and physical transmission across the media and this enables the data to locate its intended destination on a network. o The data link layer provides reliable transit of data across a physical link by using the Media Access Control (MAC) addresses. o This layer is concerned with network topology, network access, error notification, ordered delivery of frames, and flow control. Examples: Ethernet, Frame Relay, FDDI. LAYER 1: PHYSICAL LAYER deals with the physical characteristics of the transmission medium. It defines the electrical, mechanical, procedural, and functional specifications for achieving, maintaining, and deactivating the physical link between end systems. o Such characteristics as voltage levels, the timing of voltage changes, physical data rates, maximum transmission distances, physical connectors, and other similar attributes are defined by physical layer specifications. Examples: EIR/TIA-232, RJ45, NRZ. TCP/IP Model It is a networking model with a set of communication protocols for the Internet and similar networks. It is commonly known as TCP/IP because its Transmission Control Protocol and Internet Protocol (IP) were the first networking protocols defined in this model. Internet Protocol (IP) provides basic communication. Transmission Control Protocol (TCP) provides key functions that applications need. APPLICATION LAYER represents an interface through a variety of protocols that enable services to be applied to end-user application processes. These services include handling high-level protocols, issuing of representation, encoding, and dialog control. TRANSPORT LAYER is responsible for reliable end-to-end data delivery from the source host to the destination host. INTERNET LAYER (Network) is responsible for the delivery of service requests that respond from the transport layer and have them arrive at their destination through the “virtual network” image of the Internet. NETWORK ACCESS LAYER is also called the host-to-network layer, which is concerned with all of the issues that an IP packet requires to make a physical link to the network media. The network interface layer functions include mapping the IP addresses to physical hardware addresses and encapsulation of IP packets. 02 Handout 1 *Property of STI  [email protected] Page 4 of 5  IT2203 Comparison of OSI Reference Model to TCP/IP Model (Williams, 2021) The OSI Model is a logical and conceptual model that defines network communication used by systems open to interconnection and communication with other systems. On the other hand, TCP/IP helps you determine how a specific computer should be connected to the Internet and how you can be transmitted between them. OSI follows a vertical approach, whereas TCP/IP follows a horizontal approach. The OSI model’s, transport layer is only connection-oriented, whereas the TCP/IP model is both connection-oriented and connectionless. OSI model is developed by ISO (International Standard Organization), whereas TCP Model is developed by ARPANET (Advanced Research Project Agency Network). OSI model helps you standardize router, switch, motherboard, and other hardware whereas TCP/IP helps you establish a connection between different types of computers. References: Comer, D. (2019). The internet book: Everything you need to know about computer networking and how the Internet works. CRC Press. Huawei. (2020). HCIA-Datacom V1.0 Training Material. Karumanchi, N., Damodaram, A., & Rao, S. (2020). Elements of computer networking: An integrated approach. Career Monk. Kurose, T & Ross, K. (2021). Computer networking: A top-down approach. Pearson. Robertazzi, T. (2017). Introduction to computer networking. Springer International. Williams, L. (2021). TCP/IP vs OSI model: What’s the difference? [Web Article]. 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