Lecture-2

Computer Networks

  • Course: Computer Networks (CSET207)

  • Instructor: Dr. Ashish Tomar, Assistant Professor

Context

  • Slides are based on contributions from B. A. Forouzan and other freely available online materials.

Outline of Content

  • Network devices

  • Network types

  • Network topologies

Network Devices

Types of Devices

  1. Network Interface Card (NIC)

  2. Hub

  3. Bridge

  4. Switch

  5. Repeater

  6. Router

  7. Gateway

  8. Firewall

Network Interface Card (NIC)

  • Connects host devices to network media.

  • Essential for each gadget needing network access.

  • A printed circuit board fitting into motherboard expansion slots.

  • Often referred to as network adapters.

  • Identified by a unique Media Access Control (MAC) address for data communication control.

Repeater

  • Used to regenerate signals to combat transmission loss (attenuation).

  • Operates at the physical layer of the OSI model.

  • Lacks intelligence in packet forwarding.

Hubs

  • Connect multiple devices at the physical layer.

  • Functions as a multi-port repeater.

  • Cannot filter data; all packets are sent to all connected devices.

  • Active hubs concentrate hosts and regenerate signals.

Hubs Functionality

  • Acts as a 'dumb switch' that broadcasts data to all ports.

  • Maintains a single collision domain for all connected hosts.

Bridges

  • Connects multiple LANs to form a larger network.

  • Operates at the data link layer (2-port device).

  • Filters packets using MAC addresses; reads source and destination addresses.

Working of Bridges

  • Receives data packets from network segments.

  • Builds a MAC address table for direction.

  • Filters or forwards data based on destination network.

Switches

  • Used to create subnets; segments the network.

  • Operates at the data link layer and works in full duplex mode.

  • Buffers and performs error checking before forwarding data.

How Switches Function

  • Receives packets, reads headers for MAC addresses, and sends them to the correct port.

  • Sets up a temporary connection for communication, offering full bandwidth.

Routers

  • Forwards data packets across network boundaries.

  • Operates at layer 3 of the OSI model.

  • Responsible for routing traffic based on destination addresses.

Gateways

  • Connects networks with different configurations, often acting as protocol converters.

  • Operates up to layer 5 of the OSI model, managing data entry and exit.

Functionality of Gateways

  • Analyzes data packets for destination addressing.

  • May transform data format for compatibility before routing.

Firewalls

  • Monitors incoming/outgoing traffic based on security rules.

  • Controls security and access, rejecting requests from unrecognized sources.

Network Types

  1. Personal Area Network (PAN)

  2. Local Area Network (LAN)

  3. Metropolitan Area Network (MAN)

  4. Wide Area Network (WAN)

Personal Area Network (PAN)

  • Used in home environments; connects personal devices.

  • Supports document sharing and internet access.

Local Area Network (LAN)

  • Connects computers/devices within a building or premises.

  • Utilizes hubs, switches, and routers for connections.

  • Can be split into Virtual LANs (VLANs) for logical grouping.

Metropolitan Area Network (MAN)

  • Covers a larger geographic area by interconnecting LANs.

  • Ranges from 5-50 km; relies on local telecommunication protocols.

Wide Area Network (WAN)

  • Extends across states/countries; uses various transmission methods.

  • The Internet is the largest WAN implementations.

Network Topologies

  • Types: Bus, Ring, Star, Tree (Hierarchical), Mesh, Hybrid

Bus Topology

  • All devices share a single communication line.

  • Simple networking form; failure of a shared line affects all devices.

Star Topology

  • All hosts connect to a central device (hub).

  • Central device types can include hubs, switches, or routers.

Ring Topology

  • Each host connects to two other hosts in a circular layout.

  • Circulating messages require data to traverse intermediate nodes.

Mesh Topology

  • Hosts connected via point-to-point methods.

  • Types: Full Mesh (all-to-all connections), Partially Mesh (some hosts connected).

Hybrid Topology

  • Combines multiple topologies, inheriting their advantages and disadvantages.

Tree (Hierarchical) Topology

  • Hierarchical structure connected to a topmost node (root).

  • Typically has three or more levels for organizational purposes.