Ethernet 1/21

Ethernet 1/21

Applied Network Research Group Department of Computer Engineering, Kasetsart University

Local Area Networks

Surasak Sanguanpong nguan@ku.ac.th http://www.cpe.ku.ac.th/~nguan

Last updated: 11 July 2000

Ethernet 2/21

Applied Network Research Group Department of Computer Engineering, Kasetsart University

LAN Characteristics

• Confined within geographical area

• relatively high Data rate

• under single management

• Ingredients

• ^Topology

• bus, star, ring

• ^Medium

• Twisted pair, coaxial fiber optics, wireless

• Medium access Techniques

• protocol to coordinate the sharing of media

hub

hub

hub

hub

router

server

station

stations

stations

Ethernet 3/21

Applied Network Research Group Department of Computer Engineering, Kasetsart University

Topology

• A topology defines how nodes/stations are connected

• Typical topology :

• Bus : all nodes connect to a common medium

• Star : all nodes are joined to a central node

• Ring : Nodes form a ring by point-to point links to adjacency neighbors

bus star ring

Ethernet 4/21

Applied Network Research Group Department of Computer Engineering, Kasetsart University

Topology : Bus

Application Presentation

Session Transport

Network Data Link

Physical Application

Presentation Session Transport

Network Data Link

Physical

D D B and C

A B C D

D

Ethernet 5/21

Applied Network Research Group Department of Computer Engineering, Kasetsart University

Topology : Ring

• A node function as a repeater

• Only destination copies frame to it, all other nodes have to discarded the frame

• Unidirectional links

A

C ignores frame A

B

C

A

B C

B transmits frame addressed to A

A copies frame

A

A

B C

C absorbs returning frame

A

A

B

C

Ethernet 6/21

Applied Network Research Group Department of Computer Engineering, Kasetsart University

Topology :Star

• Each station attaches to a central node

• Two alternatives operation

• broadcasting

• switching

A B C

A

A B

C

A B C

A A

In a shared hub environment, the packet is broadcast to every port but only the station A copies the packet

In a switched hub environment, the packet is directly sent to the station A.

C transmits a frame addresses to A

Ethernet 7/21

Applied Network Research Group Department of Computer Engineering, Kasetsart University

Medium Access Control

• Protocol for controlling access to transmission medium

• Defined as a part of Data Link layer

• The protocol :

• performs functions related to medium access (MAC sublayer)

• concerns with the transmission of a link-level between two nodes (LLC sublayer)

Network Data Link

Physical

LLC MAC

Logical Link Control

Medium Access Control sublayer

Ethernet 8/21

Applied Network Research Group Department of Computer Engineering, Kasetsart University

MAC Address

zMAC address is hardware built in within a network interface card

00:00:0C:52:72:EB

Vendor code : 24 Serial number : 24

Ethernet 9/21

Applied Network Research Group Department of Computer Engineering, Kasetsart University

Overview of LAN standard

z 802.2 Logical Link Control z 802.3 CSMA/CD (Ethernet) z 802.4 Token Bus

z 802.5 Token Ring

z FDDI Fiber Distributed Data Interface

Ethernet 10/21

Applied Network Research Group Department of Computer Engineering, Kasetsart University

Ethernet

z

Every node can receive a transmission by all other nodes

z

Only destination copies frame to it, all other nodes have to discard the frame

A B C A B C

A B C A B C

C find that the bus is free

C transmits a frame addressed to A

B ignores the frame A copies the frame

A

A A

Ethernet 11/21

Applied Network Research Group Department of Computer Engineering, Kasetsart University

Token Ring

z

Token ring LAN continuously pass a token

A

T = 0 T = 0

T A

T = 0 T = 0

T

A

T = 1 T = 1

T Data

Ethernet 12/21

Applied Network Research Group Department of Computer Engineering, Kasetsart University

FDDI

FDDI

Dual Ring