ETHERNET

-BY 09BIT059(MIHIKA SHAH)

ETHERNET•Firstly created by Robert Metcalfe

•Known as DIX ethernet

•IEEE standardized 802.3

•Uses manchester encoding

•Ethernet framing

•CSMA/CD algorithm

FAST ETHERNET (802.3u)

•Fast Ethernet was designed to compete with LAN protocols such as FDDI (Fiber Distributed Data Interface) or Fiber Channel.

•IEEE created Fast Ethernet under the name 802.3u.

•Fast Ethernet is backward-compatible with Standard Ethernet, but it can transmit data 10 times faster at a rate of 100 Mbps.

Fast Ethernet Topology

Fast Ethernet Implementation

•Bit rate is reduced to 10 ns from 100 ns.

GIGABIT ETHERNET (802.3z)

•The need for higher data rate resulted in the design of the Gigabit Ethernet (1000 Mbps).

•The IEEE committee calls the standard 802.3z.

•All configurations of gigabit Ethernet are point to point.

•Point-to-point, between two computers or one computer – to –switch.

•It supports two different modes of operation: full duplex mode and half duplex mode.

•full duplex is used when computers are connected by a switch.

•No collision, CSMA/CD is not used.

•Half duplex is used when computers are connected by a hub.

•Collision in hub is possible and so CSMA/CD is required.

•The 802.3z committee considered a radius of 25 meters to be unacceptable and added two new feature to increase the radius.

•Carrier Extension tells the hardware to add its own padding bits after the normal frame to extend the frame to 512 bytes.

•Frame Bursting allows a sender to transmit a concatenated sequence of multiple frames in a single transmission.

•If the total burst is less than 512 bytes, the hardware pads it again.

SWITCHED ETHERNET

•The heart of the system is a switch containing a high speed back-plane and room for typically 4 to 32 plug-in cards, each containing one to eight connectors.

•When a station wants to transmit a frame,it outputs a frame to switch.The plug-in card checks to see if the frame is for the other station on the same card.

•If so, it is copied there otherwise it is sent over high speed back-plane to destination station’s card.

•What happens if two machines attached to the same plug-in card transmit frames at the same time?

•It depends in how the card is constructed. All ports on the same card are wired together to form a local on-card LAN.

•Collisions on this on-card LAN are detected and handled using CSMA/CD protocol.

•One transmission per card is possible at any instant.

•All the cards can transmit in parallel. With this design each card forms its own collision domain.

•In other design, each input port is buffered, so incoming frames are stored in the card’s on board RAM.

•It allows all input ports to receive(and transmit) frame at same time.

THANK YOU