Introduction - 1 Introduction to Local Area Networks (LANs) All rights reserved. No part of this publication and file may be reproduced, stored in a.

Introduction - 1

Introduction to Local Area Networks (LANs)

All rights reserved. No part of this publication and file may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise,

without prior written permission of Professor Nen-Fu Huang (E-mail: [email protected]).

Introduction - 2

What is a LAN ?A LAN is a data communication system

allowing a number of independent devices to communicate directly with each other, within a moderately sized geographic area over a physical communications channel of moderate data rates.

ThusIndependent DevicesCommunicate DirectlyModerately Sized Geographic AreaModerate Data Rate

Introduction - 3

Basic Requirements of a LAN

Data rate of 1 to 1000 MbpsGeographic distances spanning at most

1-5 kmAbility to support several hundred

independent devicesSimplicity, or use of the simplest

mechanisms that have the required functionality and performance

Reliability and good error characteristics

Introduction - 4

Basic Requirements of a LAN

Minimal dependence on any centralized components or control

Efficient use of shared resources, including the network channel

Stability under high loadFair access (bandwidth, delay) to the

network by all devicesEasy installationEase of reconfiguration and maintenanceLow cost

Introduction - 5

LAN ComponentsComputers (Networking devices)Transmission System (Network

Cards, Cabling)

傳輸媒介 :同軸電纜 ,雙絞線 ,光

纖 ,無線電波等等

工作站

工作站

工作站

工作站

工作站

Introduction - 6

LAN Extension

LAN Segment 1 LAN Segment 2

Repeater

Introduction - 7

Network Topologies

StarSingle Star (IEEE 802.12 100VG-AnyLAN, ATM)Multiple Star (Snowflake) (ATM)

Bus/TreeSingle Bus (IEEE 802.3 CSMA/CD, IEEE 802.4

Token-Bus)Dual Bus (IEEE 802.6 DQDB)

RingSingle Ring (IEEE 802.5 Token Ring)Dual Ring (FDDI, FDDI-II)

Mesh

Introduction - 8

Network Topologies

A C E

A

E

B

D

B D F

A

E

B

D

A

E

B

D

C E

B D

F

A

A B C

C C C

Star Ring Dual Ring

Bus Tree Dual Bus

Introduction - 9

Network Topologies

A B C

A B C D

A

C E

B

DF

Dual Bus Dual Bus Mesh

A

G

B

E

D

F

C

H

Snowflake

Introduction - 10

Network Topologies

A

E

B

D

C F

J

G

I

H

K

O

L

N

M

橋接器

橋接器 橋接器橋接器

Bridged Ring Networks

C

A

BF

D

E

G

H

...

Hub or SwitchHub or Switch

Introduction - 11

Open System Interconnection (OSI) Model-- Seven Layers

應用層 (Application Layer)

表達層 (Presentation Layer)

會議層 (Session Layer)

傳輸層 (Transport Layer)

網路層 (Network Layer)

鏈結層 (Data Link Layer)

實體層 (Physical Layer)

Introduction - 12

Open System Interconnection (OSI) Model

Physical Layer. Responsible for transmission of bit streams across a particular physical transmission medium. Retransmission is not supported.

Encoding/DecodingData Link Layer. Responsible for

providing reliable data transmission from one node to another. Provides error-free transmission of frames.

Introduction - 13

LocalNetwork

G H

WAN

LocalNetwork

LocalNetwork

LocalNetwork

G

G G

G

GH

H

H

H

H

H

H

H

H

Transport Layer and up Layers (TCP/Telnet/FTP/Http)

Routing (Layer 3)

Layer 2

Introduction - 14

Open System Interconnection (OSI) Model

Network Layer. Concerned with routing data from one network node to another. Provides routing path selection.Establishing/maintaining/Terminating

network connectionTransport Layer. Responsible for

providing data transfer between two end users at an agreed on level of quality. Establishing/maintaining/Terminating

transport layer connection

Introduction - 15

Open System Interconnection (OSI) Model

Session Layer. Providing services used to organize and synchronize the dialog that takes place between users and to manage the data exchange.

Presentation Layer. Responsible for the presentation of information to the network users.Character code translation/ Data conversionData compression/expansionEncryption/Decryption

Introduction - 16

Open System Interconnection (OSI) Model

Application Layer. Provides services to application processes or users.File Transfer Protocol (FTP)Remote Login (Telnet)Transaction ServerNetwork ManagementWWW Server/VoD ServerBrowser (HTTP)Internet Telephony/Video Streaming/IPTV

Introduction - 17

Layering Concept

Service Access Point (SAP)Layer N provides services for layer N+1 by using the services provided by layer N-1.

Introduction - 18

Layering Concept

第 N-1 層

第 N 層

服務點第 N+1 層

通訊軟體通訊軟體

通訊軟體

通訊軟體

通訊軟體

通訊軟體 通訊軟體

第 N-1 層

第 N 層

第 N+1 層通訊軟體

通訊軟體通訊軟體

通訊軟體

通訊軟體

通訊軟體 通訊軟體

通訊協定通訊協定

系統 A 系統 B

Introduction - 19

Layering Protocols

應用層

表達層

會議層

傳輸層

網路層

鏈結層

實體層

應用層

表達層

會議層

傳輸層

網路層

鏈結層

實體層

應用軟體 X

鏈結層通訊協定

傳輸媒介

應用軟體 Y

網路層通訊協定

傳輸層通訊協定

會議層通訊協定

表達層通訊協定

應用層通訊協定

實體層通訊協定

系統 A 系統 B

Introduction - 20

Basic Functions of Protocols

Encapsulation/DecapsulationSegmentation/ReassemblyConnection EstablishingFlow ControlError ControlMultiplexing

Introduction - 21

Encapsulation/Decapsulation Mechanisms

應用層

表達層

會議層

傳輸層

網路層

鏈結層

實體層

應用層

表達層

會議層

傳輸層

網路層

鏈結層

實體層

應用軟體 X

AH

PH

SH

TH

NH

資料

資料

資料

資料

資料

資料

資料 F A C FCS F

位元串

通訊路徑

應用軟體 Y

往下送時訊框包裝 往上送時訊框拆裝

IP

TCP/UDP

FTP/HTTP/Telnet/DNS

FTP/HTTP/Telnet/DNS

TCP/UDP

IP

CSMA/CD CSMA/CD

資料資料資料

Introduction - 22

Preamble/SFD DA SA LEN IP TCP FTP Data FCS

8 6 6 2 < 1500 4 bytes

version IHL Type of Service Total length

Indentification Flags Fragment Offset

Time to Protocol Header Checksum

Source IP Address

Destination IP Address

Options + Padding

Data

0 3 8 15 19 31 4 6 1 1 1 1 1 1 16 位元Source port Destination port

Sequence numberAcknowledgment number

Dataoffset Rsvd

URG

ACK

P SH

RST

SYN

F IN

Window

Checksum Urgent pointerOptions + PaddingData (不固定長度)

Introduction - 23

Connections Multiplexing

Upward Multiplexing: Several layer N connections should be multiplexed into a layer N-1 connection.

Downward Multiplexing: a layer N connection uses several layer N-1 connections.

Introduction - 24

Connections Multiplexing

第 N-1 層

第 N 層

服務點

一對一向上多工 向下多工

通訊軟體通訊軟體

通訊軟體

通訊軟體

Introduction - 25

IEEE Project 802 Standards

IEEE 802.1 High Level InterfaceIEEE 802.1D Local Bridge (Spanning Tree Algorithm)IEEE 802.1w Fast Spanning Tree AlgorithmIEEE 802.1p Dynamic Multicast membershipIEEE 802.1Q Virtual LAN (VLAN)

IEEE 802.2 LLC (Logical Link Control) IEEE 802.3 CSMA/CD (Carrier Sense Multiple Access with C

ollision Detection IEEE 802.4 Token-Bus IEEE 802.5 Token-Ring IEEE 802.6 DQDB (Distributed Queue Dual Bus)

Introduction - 26

IEEE Project 802 Standards

IEEE 802.7 Broadband Technical Advisory Group IEEE 802.8 Fiber Optic Technical Advisory Group IEEE 802.9 Integrated Voice and Data LAN Working Group IEEE 802.10 LAN Security Working Group IEEE 802.11 Wireless LAN IEEE 802.12 Demand-Priority (100VG-AnyLAN) IEEE 802.14 CATV Networks (HFC) IEEE 802.16 WiMAX IEEE 802.17 Resilient Packet Ring Working Group IEEE 802.18, the Radio Regulatory Technical Advisory Group IEEE 802.21 Media Independent Handover (MIH).

Introduction - 27

802.3

CSMA/CD

802.4

Token-Bus

802.5

Token-Ring

802.6

DQDB

802.9

Isochronous

802.11

Wireless

802.12

100VG-AnyLAN Ethernet LAN

AX3T9.5

FDDI

802.2 LLC

802.1 網路連結技術

實體層

媒介擷取層

鏈結層

IEEE Project 802 Standards