Network Comm Lecture 4 PDF

NETWORK TOPOLOGY  NETWORK TOPOLOGY INTRODUCTION Network topology refers to the arrangement of nodes (computers, devices, etc.) and connections in a network. Below is an explanation of major types of network topologies, along with their advantages, disadvantag...

NETWORK TOPOLOGY  NETWORK TOPOLOGY INTRODUCTION Network topology refers to the arrangement of nodes (computers, devices, etc.) and connections in a network. Below is an explanation of major types of network topologies, along with their advantages, disadvantages, and real-world examples  Bus Topology In a bus topology, all devices are connected to a single central cable (the "bus"). The data travels in both directions along the bus, and each device listens for data addressed to it.  Advantages 1. Easy to set up and extend. 2.Cost-effective as it uses less cable compared to other topologies. 3.Works well for small networks. 4.Requires minimal hardware (no need for switches or hubs). 5.Simple to understand and troubleshoot.  Disadvantages A single cable failure can bring down the entire network. Limited scalability due to signal degradation over long distances. Performance degrades as the number of devices increases. Not suitable for heavy network traffic. Troubleshooting cable breaks can be challenging.  Real-World Examples It is used in: 1. Small office 2. Home networks, early LAN setups, and experimental  Tree Topology Tree topology is a hierarchical structure where devices are connected in a tree-like pattern, with one root node and branching connections. It combines aspects of star and bus topologies. Tree Topology  Advantages 1. Highly scalable and suitable for large networks. 2. Centralized management through the root node. 3. Easier to troubleshoot specific branches. 4. Supports point-to-point wiring for individual segments. 5. Allows expansion by adding additional branches.  Disadvantages 1. Root node failure can affect the entire network. 2. Complex to set up and manage. 3. Expensive due to extensive cabling and hardware requirements. 4. Signal degradation can occur in long branches. 5. Network maintenance can be time-consuming.  Real-World Examples 1. Corporate networks 2. Hierarchical school or 3. University networks.  Star Topology All devices are connected to a central hub or switch in a star-like pattern. The hub acts as the communication controller. Star Topology  Advantages 1. Centralized management simplifies troubleshooting. 2. Easy to add or remove devices without affecting the entire network. 3. Offers better performance with minimal data collisions. 4. Isolation of devices ensures that a single failure doesn't disrupt the whole network. 5. Supports high-speed data transmission.  Disadvantages 1. Central hub failure can bring down the entire network. 2. Expensive to set up due to the cost of hubs and cabling. 3. Limited scalability as the hub has a finite number of ports. 4. Increased dependency on the central hub. 5. Requires more cabling compared to bus topology.  Real-World Examples 1. Office LANs 2. Home networks, and 3. Data centers. 4. Most modern offices use a star topology with centralized switches to manage connectivity and ensure reliability.  Ring Topology In a ring topology, devices are connected in a circular fashion. Data travels in one direction (unidirectional) or both directions (bidirectional) along the ring. Ring Topology  Advantages 1. Easy to set up and expand. 2. Data collisions are minimized due to token passing (if used). 3. Can handle high volumes of data traffic. 4. Equal access is provided to all devices in the network. 5. Works well for small-to-medium- sized networks.  Disadvantages 1. A single node or cable failure disrupts the entire network. 2. Troubleshooting and maintenance can be challenging. 3. Scalability is limited due to increased complexity with more devices. 4. Slower than star topology in large networks. 5. Adding or removing devices can disrupt network operations.  Real-World Examples 1. Fiber Distributed Data Interface (FDDI), 2. Small campus networks. 3. Fiber rings are used in metropolitan areas for redundancy in large-scale internet and communication services.  Mesh Topology In a mesh topology, every device is connected to every other device, creating multiple pathways for data to travel. It can be fully connected or partially connected. Mesh Topology  Advantages 1. Provides high reliability due to redundant paths. 2. No single point of failure (in full mesh). 3. Ensures consistent communication between devices. 4. Can handle high traffic volumes efficiently.  Disadvantages 1. Expensive to set up and maintain due to extensive cabling and hardware. 2. Complexity increases with the number of devices. 3. Troubleshooting is more difficult compared to other topologies. 4. Requires a lot of space for cabling. 5. Not practical for small or cost- constrained networks.  Real-World Examples 1. Military communication systems, 2. IoT networks, and 3. Backbone networks. 4. Full or partial mesh topologies are implemented in data centers to ensure fault tolerance and high performance. Communication Protocols  Communication Protocols: A communication protocol is a set of rules that govern how data is exchanged between devices, especially over a network. These protocols are essential for networking and telecommunications because they ensure that digital messages are sent and received consistently  Communication protocols are made up of hardware and software components that govern how devices connect.  Network Protocols Networking protocols are a set of rules and conventions that enable devices on a network to communicate and share data. These protocols define how data is formatted, transmitted, and processed across networks, ensuring seamless communication.  1. Transmission Control Protocol/Internet Protocol (TCP/IP) TCP/IP is the fundamental protocol suite for the internet and most networks. It combines the TCP (responsible for ensuring reliable data delivery) and IP (responsible for addressing and routing data).  Key Features 1. Ensures data packets are delivered in order and without errors. 2. Handles retransmission of lost packets. 3. Provides a foundation for other protocols (e.g., HTTP, FTP).  Applications 1. Web browsing 2. File transfers, and 3. Email communication.  2. HyperText Transfer Protocol (HTTP/HTTPS) HTTP is used for transferring web pages and data over the internet. HTTPS is a secure version that encrypts data to ensure privacy. Key Features: Stateless: Each request is treated independently. HTTPS ensures secure communication using SSL/TLS encryption.  Applications 1. Accessing websites, 2. APIs, and 3. Online applications  3. File Transfer Protocol (FTP) FTP allows transferring files between a client and server over a network. Key Features: Provides authentication for secure file transfers. Can transfer large volumes of data efficiently.  Applications Uploading files to websites and Downloading data from servers.  4. Simple Mail Transfer Protocol (SMTP) SMTP is used for sending and forwarding emails. Key Features: Works with other protocols like IMAP or POP3 for email retrieval. Ensures email delivery between mail servers.  Applications 1. Sending emails from client applications to servers. 5. Domain Name System (DNS) 1. DNS translates human- readable domain names (e.g., www.example.com) into IP addresses that computers use to identify each other on the network.  Key Features Provides hierarchical name resolution. Ensures users don't need to memorise numeric IP addresses. Applications: Browsing the internet.  6. Dynamic Host Configuration Protocol (DHCP) DHCP automatically assigns IP addresses to devices on a network. Key Features: Simplifies network management. Prevents IP address conflicts. Applications: Setting up LAN or enterprise networks.  7. Secure Shell (SSH) SSH provides a secure method for remote access and management of network devices. Key Features: Encrypts communication to prevent eavesdropping. Supports file transfers via SCP and SFTP.  Applications Remote administration of servers. OSI MODEL  HARDWARE DEVICES One of the problems in transmitting data down a public or private telephone wire is the possibility of distortion or loss of the message (or “noise”).  HARDWARE DEVICES There need to be some way for a computer to:  Detect whether there are errors in data transmission (e.g. loss of data, or data arriving out of sequence, i.e. in an order different from the sequence in which it was transmitted.  HARDWARE DEVICES  Take steps to recover the lost data, even if this is simply to notify the computer or terminal operator to telephone the sender of the message that the whole data package will have to be re- transmitted.  HARDWARE DEVICES A more “sophisticated” system can identify the corrupted or lost data more specifically and request re-transmission of only the lost or distorted parts. The mechanism used to detect and usually then to correct errors is known as a COMMUNICATIONS PROTOCOL.  HARDWARE DEVICES It is further defined as “An agreed set of operational procedures governing the format of data being transferred and the signals initiating, controlling and terminating the transfer.  OPEN SYSTEM INTERCONNECTION (OSI) Communications between interconnected computer systems is a complex activity which takes place at a number of different levels. At the lowest level there is the physical transmission of signals and at the highest level there may be communication of messages in everyday languages.  OPEN SYSTEM INTERCONNECTION (OSI) In an attempt to form a basis for standardizing such interconnections, the International Standards Organisation (ISO) has devised a standard based upon a set of seven distinct levels or layers of communication.  OPEN SYSTEM INTERCONNECTION (OSI) This model is known as the reference model for Open System Interconnection (OSI). It is a set of protocols which has been developed by ISO. The protocol was divided into seven functions in a SEVEN- LAYER REFERENCE MODEL.  OPEN SYSTEM INTERCONNECTION (OSI) The seven-layer OSI (Open systems Interconnection) model, created by the ISO (International Standards Organization), defines internetworking environments. It provides a description of how software and hardware interact to permit communication between computers.  OPEN SYSTEM INTERCONNECTION (OSI) An interface separates each layer from those above and below it; each layer provides services to the layer directly above it.  MNEMONIC FOR OSI MODEL 7. ALL APPLICATION 6. PEOPLE PRESENTATION 5. SEEM SESSION 4. TO TRANSPORT 3. NEED NETWORK 2. DATA DATA LINK 1. PROCESSING PHYSICAL  APPLICATION WHAT THE LAYER IS CORRESPONDING PROTOCOLS RESPONSIBLE FOR/SERVICES ETC. 1. Interface between the user & the computer (applications & Gateways). SNMP Provides services that directly support user applications, such as the FTP USER INTERFACE, E-MAIL, FILE TRANSFER, TELNET TERMINAL EMULATION, HTTP DATABASE ACCESS, etc. 2.API (Application Programming Interface) SMTP incorporated in this layer 3. Allows applications to use the network. DNS 4. Handles Network access, flow control & error recovery. 5. Messages are sent between layers.  PRESENTATION WHAT THE LAYER IS CORRESPONDING RESPONSIBLE PROTOCOLS FOR/SERVICES ETC. 1. Translation of data into understandable format for transmission (into a form usable by  JPEG the application layer i.e. translates data between the formats the network requires and  MIDI the computer expects). 2. Handles character encoding, bit order and  MPEG byte order issues. Encodes and decodes data. 3. Data compression and encryption takes  All kinds of music, place at this layer. pictures & movie 4.Generally determines the structure of data 5.Responsible for protocol conversion formats 6.Communicates through GATEWAYS and APPLICATION INTERFACES  SESSION WHAT THE LAYER IS CORRESPONDING RESPONSIBLE PROTOCOLS FOR/SERVICES ETC. 1. Responsible for opening, using and closing session.  Network File System That is. It allows applications on connecting systems to establish a session (Establishes and (NFS) maintains a connection). 2. Provides synchronization between  SQL communicating computers (nodes), messages are sent between layers (i.e. Manages upper layer errors).  RPC 3. Also places checkpoints in the data flow, so that if transmission fails, only the data after the last checkpoint needs to be retransmitted. 4. Handles remote procedure calls. 5. Communicates through Gateways & application interfaces.  TRANSPORT WHAT THE LAYER IS CORRESPONDING RESPONSIBLE PROTOCOLS FOR/SERVICES ETC. 1. Responsible for PACKET HANDLING. Ensures error free delivery. Repackages messages, divides  TCP messages into smaller packets (Fragments and reassembles data), and handles error handling 2. Ensures proper sequencing and without loss and  UDP duplication. 3.Takes action to correct faulty transmissions  SPX 4.Controls flow of data 5.Acknowledges successful receipt of data  NetBEUI 6. TCP - connection oriented communication for applications to ensure error free delivery. 7. UDP - connectionless communications and does not guarantee packet delivery between transfer points 8. Communicates through Gateway Services, routers & brouters.  NETWORK WHAT THE LAYER IS CORRESPONDING RESPONSIBLE PROTOCOLS FOR/SERVICES ETC. 1. Logical addressing - software addresses (IP address) to hardware addresses (MAC Address) are  Routers resolved (ARP/RARP).  Brouters 2.Routing of message (Packets) between hosts & networks (IP/IPX).  IP 3. Determining the best route (Makes routing decisions & forwards packets (a.k.a. DATAGRAMS)  RIP for devices that could be farther away than a single link.  ICMP 4. Moves information to the correct address.  ARP 5.Sends messages and reports errors regarding packet delivery (ICMP)  RARP 6.Reports host group membership to local multicast routers (IGMP)  OSPF 7. Communicates through GATEWAY SERVICES,  IGMP ROUTERS & BROUTERS  DATA LINK WHAT THE LAYER IS CORRESPONDING RESPONSIBLE PROTOCOLS FOR/SERVICES ETC. 1.Provides for flow of data over a single link from one device to another  HDLC 2.Controls access to communication  (High-level Data Link channel 3.Controls flow of data Control) 4. Packets placed into frames at this layer  LLC (i.e. Organizes data into logical frames - logical units of information).  Flow control. 5. CRC is added at this Layer (Error detection).  SLIP 6. If CRC fails at the receiving computer,  PPP this layer will request re-transmission.  DATA LINK WHAT THE LAYER IS CORRESPONDING RESPONSIBLE PROTOCOLS FOR/SERVICES ETC. 7.MAC addresses are resolved at this Layer (switches, brouters and bridges function on this layer using the MAC sub layer) 8. Sends data from network layer to physical layer. 9. Manages physical layer communications between connecting systems. 10. Ethernet, Token Ring & other communications occur here via frames. MAC- (802.3, 802.4, 802.5, and 802.12) communicates with adapter card. 11.Communicates through: SWITCHES, BRIDGES & INTELLIGENT HUBS  DATA LINK WHAT THE LAYER IS CORRESPONDING RESPONSIBLE PROTOCOLS FOR/SERVICES ETC. NOTE: The Data Link Layer contains two SUB-LAYERS. LLC (Logical Link Control) - The upper sub-layer, which establishes and maintains links Between communicating devices. Also responsible for frame error correction and hardware addresses. MAC (Media Access Control) -The lower sub-layer, which controls how devices share a media channel. Either through CONTENTION or TOKEN PASSING  PHYSICAL WHAT THE LAYER IS CORRESPONDING RESPONSIBLE PROTOCOLS FOR/SERVICES ETC. 1. Data (BITS) is sent across physical media like wires and hubs. 2.Responsible for encoding scheme (like Manchester encoding) 3. Defines cables, cards and physical aspects. 4. Provides electrical and mechanical interfaces for a network. 5.Specifies how signals are transmitted on network 6.Communicates through: REPEATERS, HUBS, SWITCHES, CABLES, CONNECTORS, TRANSMITTERS, RECEIVERS,  PHYSICAL WHAT THE LAYER IS CORRESPONDING RESPONSIBLE PROTOCOLS FOR/SERVICES ETC. Hubs  NONE Repeaters Amplifiers Transceivers Multiplexers Receivers Transmitters Connectors Cables Switches