Discussion on Bridges in Networking Computer Science YouTube Lecture Handouts

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Disscussion on Bridges

Complete notes and preparation module at

Computer Science

Topics to Be Covered

1. Definition

2. Connection representation

3. Types of Bridging

4. Simple Bridging

5. Multiport Bridging

6. Transparent Bridging

7. Implementation of Bridging

8. Forwarding

9. Shortest path Bridging

10. MCQs

Definition

A network bridge is known as computer networking device which is able to create one aggregate network from various communication networks or with the segments of network, called networking bridging.

Representation of Connections

Representation of Connections

Types of Bridges

Types of Bridges

Simple Bridging

  • Simple Bridging is basically used to connect two network segments by operating transparently and taking decision on a frame-by-frame basis, not to forward from one network to any other.
  • A store and forward technique is used as part of forwarding and in this frame integrity is verified on network allocated to source and delays are basically possible on the destination.

Working of Simple Bridging

Working of Simple Bridging

Transparent Bridging

  • This bridging mostly uses table which is known as forwarding information. Its base working is to control forwarding of frames between different segments of networks.
  • This bridging also operates over devices having multiple ports.
  • Two-port Bridge reads frame destination address then decides either to forward or filter.

Working of Transparent Bridging

Working of Transparent Bridging

Multiport Bridging

  • This bridging used to connect multiple networks and it usually operates transparently to take decision regarding to forward traffic basis on frame-by-frame.
  • Apart from this, it must decide the direction of traffic movement.
  • Likewise, multiport bridge typically perform state and forward operations similar as simple bridging technique.
  • The functions of this bridging serves as the basis of network switches.

Working of Multiport Bridging

Working of Multiport Bridging

Implementation

  • The forwarding information base mostly stored in content-addressable memory (CAM) which is empty at its initial state.
  • For received Ethernet frame bridges mostly learn the MAC addresses from the frame source.
  • Bridges forward frame to interface found in CAM which is based on frames destination MAC address.
  • If destination address in not familiar then switch send frame out from all interfaces, process known as unicast flooding.

Forwarding

  • After learning the addresses of connected nodes, bridges prefers to forward the date through data link layer by using method, named layer-2 forwarding.
  • There are four different methods included in forwarding which are given below:-
Methods of Forwarding

Explanation of Methods of Forwarding

  • Store and forward:- In this method mostly switch buffers and work on verification of each frame before forwarding it and frame also received in its entirely before forwarding it.
  • Cut through:-thereีšs no error checking in this method. Ehen outgoing port is busy then switch prefers to fall back to store and forward operation. Moreover, switch starts forwarding process when it receives frame destination address. Last but not the least, by using store and forward method, port is running faster as compared to ingress port.
  • Fragment free: - It is method which attempts to retain the advantages of both methods i.e.. store and forward and cut through method. It checks first 64 bytes of frame where addressing information is stored.
  • Adaptive Switching: - It is the method which is automatically selecting between the other three modes of forwarding.

Shortest Path Bridging

  • It is specified in IEEE802 standard, which is computer networking technology refers to simplify creation and configuration of networks though out multipath routing enable.
  • It is developed for the replacement of spanning tree protocol which used to block any redundant paths that may resulted in layer2 loop.
  • This method allows all paths to be active with multiple equal cost paths.
  • This method basically enhances the count of VLANs allotment on a layer 2 network.

MCQs

Q1. How many types of brides are there in networking?

a) Two

b) Eight

c) Three

d) None of these.

Answer: c

Q2. Which method is automatically selected between other three modes?

a) Fragment free

b) Cut through

c) Store and forward

d) Adaptive Switching

Answer: d

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