Computer Network Devices

Lecture 2: Computer Network Devices

• This lecture covers unicast, multicast, and broadcast frames.
• It aims to give a understanding of the functions completed by computer network devices.

Unicast, Multicast and Broadcast Frames - Recap

• A unicast frame is a data frame sent to a specific destination.
• Each unicast frame has a unique 48-bit destination MAC address.
• The source MAC address of such a frame is always a unicast address.
• A multicast frame is destined for a group of stations.
• A broadcast frame is intended for all stations within a network segment or broadcast domain.
• The destination MAC address for a broadcast frame is FF-FF-FF-FF-FF-FF in hexadecimal.
• This hexadecimal address translates to 48 binary 1s

Network Devices

• Network devices constitute electronic products designed to:

  • Facilitate connections between hosts.
  • Link network segments.
  • Expand the network's size.
  • Improve network performance.
  • Integrate separate subnetworks or networks.

• Examples of network devices:

  • Repeaters/Hubs
  • Switches
  • Routers

Repeaters

• Repeaters clean, amplify, and send signals.
• They operate at the physical layer of the OSI reference model.

Hubs

• Hubs act as multi-port repeaters
• Hubs serve as junction boxes, linking cables from several computers on a network.
• Some hubs support connections for different types of cabling, including UTP and coax.

Layer 2 Switches

• Operate at the data link layer of the OSI reference model
• Divide a network into segments
• Designed to be more intelligent than hubs
• Can analyze and filter traffic based on MAC addresses
• Provide dedicated point-to-point connections between nodes.
• They allow high frame forwarding and tighter network security
• Layer2 switches forward Ethernet frames based on the destination MAC address of the frames
• A switch must learn the MAC addresses of devices connected to it.
• As a switch learns devices' MAC addresses, it builds a MAC address table using content addressable memory (CAM).
• The switch uses the MAC address table to determine how to forward traffic.
• If a switch receives a frame with a destination MAC address not found in its table, it sends it out of all ports except the one it was received on.

Layer 3 Switches

• Layer 3 switches operate at the network layer, making forwarding decisions based on layer 3 information, i.e., IP addresses.
• Layer 3 switches are very similar to routers in functionality.
• However, they differ in how they implement packet switching.
• Layer 3 switches are capable of performing layer 3 and layer 2 load sharing.
• They load share by destination IP or VLAN.

Routers

• Routers route data packets between different networks or subnetworks based on IP addresses.
• Routers select the best path to deliver the data packets.
• By default, routers do not forward broadcast traffic.