topics 3.3 ethernet_ratan kumar mondal

8/2/2019 Topics 3.3 Ethernet_Ratan Kumar Mondal

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LINK LAYERCHAPTER 3

3.3 ETHERNET(IEEE 802.3)

Ratan Kumar Mondal


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Contents

3.3.1 Ethernet Evolution: A Big Picture

3.3.2 The Ethernet MAC

3.3.3 Selected Topics in Ethernet


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Ethernet Evolution: A Big Picture


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The major trends :

From low to high speed : Prototype running at 3 Mbps 10 Gbps

IEEE 802.3ba aim: Data rate up to 40 Gbps and 100 Gbps

Ethernet built into motherboard

From shared to dedicated media :

Original Ethernet: Bus topology with Co-axial cable CSMA/CD MAC algorithm

Collisions in common sharing Bus

Development of 10BASE-T: Dedicated mediabetween two devices become the majority

Full-duplex Ethernet: Allows both stations to transmit over the dedicated media simultaneously, which in effect

doubles the bandwidth


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The major trends From LAN to MAN and to WAN :

Richer medium : Media: coaxial cables, twisted pairs, and optical fibers.

Ethernet is Multimedia! by Rich Seifert

LAN WANMAN


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The major trends


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3.3.2 THE ETHERNET

MAC


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The Ethernet MAC

Ethernet Framing, Addressing, and Error Control:

Medium Access Control: Transmission and Reception Flow


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The Ethernet MAC

Frame Transmission Flow of CSMA/CD


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The Ethernet MAC

Frame reception flow of CSMA/CD:


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The Ethernet MAC

Can Collision Cause Bad Performance?

Maximum Frame Rate: Example: 100Mbps System

A frame transmission occupies

(7 + 1 + 64 + 12) 8 = 672 bit times

(7-byte preamble and a 1-byte SFD, Frame minimum size 64 bytes, 12 bytes IFG)Maximum Frame Rate= frames/second

collision sounds terrible!

Where can a collision occur?


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The Ethernet MAC

Full-Duplex MAC :

IEEE 802.3x Task Force added full-duplex operation

CS, MA & CD are all gone!

Three conditions should be satisfied in order to run full-duplex Ethernet:

The transmission medium must be capable of transmitting and receiving on

both ends without interference. The transmission medium should be dedicated for exactly two stations, forming

a point-to-point link.

Both stations should be able to be configured into the full-duplex mode.

Ethernet Flow Control:

Flow control in Ethernet depends on the duplex mode False carrier : If the receiver cannot afford more incoming frames, it can transmit a

carrier. The transmitter will sense the carrier and defer its subsequent transmission

Force collision: When a frame transmission is detected the congested receiver canforce a collision

False carrier and Force collision are collectively called Back Pressure


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Open Source Implementation 3.5: CSMA/CD

Block Diagram Host interface

Transmit (TX) module

Receive (RX) module

MAC control module Media Independent Interface

(MII) management module


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Data Structures and Algorithm Implementations

State Machines: TX and RX

FIGURE 3.20 The TX (upper) and RX (lower) state machines


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3.3.3 SELECTED TOPICS IN

ETHERNET


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Gigabit Ethernet

Two task forces: 802.3z and 803.3ab

Gigabit Ethernet transmits ten times faster than 100 Mbps Ethernetdoes, making the distance restriction ten times shorter.

IEEE 802.3 standard appends: carrier extension, extends the framelength without changing the minimum frame size

the resultant throughput is poor

Full-duplex Ethernet: implementation is simpler

than half-duplex Ethernet

The throughput is much higher

the restriction on distance is no

longer a concern


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10 Gigabit Ethernet

Just like Moores Law, the speed of Ethernet has also grown

exponentially since its early days

Key features of 10 Gigabit Ethernet:

Full duplex only

Compatibility with past standards

The frame format

MAC operations

Move toward the WAN market

longest distance in the new standard is 40 km

WAN PHY: interface with OC-192 in SONET infrastructure


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Ethernet in the First Mile

New topologies :point-to-point on fiber

point-to-multipoint on fiber

point-to-point on copper.

New PHYs : Point-to-point optics

Point-to-multipoint optics

Point-to-point copper

Far-end operations, administration, and maintenance

(OAM) :remote failure indicationremote loopback

link monitoring

Ethernetin the

First Mile


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Summary

Introducing to the evolution and philosophy of Ethernetbased on CSMA/CD

Full-duplex operation is the dramatic change in Ethernet,Therefore, CS, MA and CD are all gone!

Introducing some efficient topics in Ethernet evolutionsuch as Gigabit Ethernet , 10 Gigabit Ethernet, Ethernet inthe First Mile.


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