ETHERNET DEVICES -BY MUJTABA FARAZ

OBJECTIVES CSMA/CD Algorithm Hubs Bridges Ether Switches Working of Ethernet switches

CSMA/CD Algorithm Working of CSMA/CD: CSMA/CD logic helps to prevent collisions and also defines how to act when a collision does occur. Working of CSMA/CD: Step 1: A device with a frame to send listens until the Ethernet is not busy Step 2: When the Ethernet is not busy the sender(s) begin sending the frame Step 3: The sender(s) listen to make sure that no collision occurred Step 4: If a collision occurs, the devices that had been sending a frame each send a jamming signal to ensure that all stations recognize the collision Step 5: After the jamming is complete, each sender randomizes a timer and waits that long before trying to resend the collided frame Step6: When each random timer expires, the process starts over with step 1

Draw Backs of CSMA/CD: It does not prevent collision rather it ensures that the Ethernet works well even though collision occurs Only one device can send frame at any one instant of time The logic of waiting to send a frame until a LAN is silent makes the Ethernet half duplex Random timing after the jamming signal effects the speed of the Ethernet

HUBS Hubs are also known as repeaters with multiple physical ports Hubs regenerates the electrical signal that comes in one port and sends the same signal out every other ports Hubs has one Collision and broadcast domain Draw Backs of Hub: High collision rate Overall Network Performance is low Not efficient for big network

Network Bridges Bridges are intelligent devices They have the ability to learn MAC addresses Bridges divides the network into multiple collision domains Draw backs: Bridges are slow devices Separate software is used learning the MAC address

SWITCHES Ethernet switches eliminates the collisions in the network Each port of a switch is one collision domain Communication in a switch is full duplex High Speed Communication

How Does Switch..Switches