Network = Net + Work

• What is flowing ?

• What different forms flow ?

• What rules govern flow ?

• Where does the flow occur ?

Data Network

• What is flowing ?– Data

• What different forms flow ?– Text, Graphic, Video ...

• What rules govern flow ?– Standard, Protocol ...

• Where does the flow occur ?– Wire, Cable, Atmosphere ...

Evolution of Networking (1)

Individual Computers

Evolution of Networking (2)

• Duplicate equipment and resources

• Difficult to communicate

• Difficult to provide management

Evolution of Networking (3)

LAN: Local Area Network

Evolution of Networking (4)

WAN: Wide Area Network

LAN = Local Area Network

• 高速、低錯誤率且涵蓋較小地理範圍 (到數千公尺 ) 的數據網路

• 可連接在同一大樓或地理限制內的工作站、周邊設備、終端機和其他設備等。

• LAN 的標準指定了纜線，以及 OSI 模型之實體和資料鏈結層的傳訊。乙太網路、 FDDI 、記號環網路都是廣泛被使用的 LAN 技術。

• 全時段連線

LAN Equipment: Repeater

Regenerates and Repeats the signal.

LAN Equipment: HUB

Multiport Repeater

LAN Equipment: Bridge

Filter traffic based on MAC Addresses.

LAN Equipment: Switch

Multiport Bridge

LAN Equipment: Router

Path determination

Packet switching

WAN = Wide Area Network

• 服務廣大區域使用者的資料通訊網路，通常使用電信公司所提供的傳輸設備。

• 訊框中繼、 SMDS 和 X.25 等都是廣域網路的實例。 • 頻寬較低 (與 LAN 比較 )• 全時段或部分時段

WAN Media: ISDN & PSTN

Part-time connectivity (Dial-up by modem)

WAN Media: Frame Relay

Full-time connectivity

WAN Media: Leased Line

Full-time connectivity

WAN Equipment: Modem

MODEM = MOdulate and DEModulate

Syn Modem, Asyn Modem

WAN Equipment: Comm. Server

Remote Access Server

WAN Equipment: WAN Switch

Frame Relay switch

WAN Equipment: Router

LAN and WAN connectivity

MAN= metropolitan-area network

• MAN - 大都會區域網路 (metropolitan-area network) 。

•擴展至大都會區域的網路。• MAN 所擴展的區域會大於 LAN ，但小於 WAN 。

Digital Bandwidth

• How much information can flow from one place to another in a given amount of time.

Comparing Speed & Distance

Media Bandwidth Distance

10Base2 10-100Mbps 185m

10Base5 10-100Mbps 500m

10BaseT 10Mbps 100m

100BaseTX 100Mbps 100m

100Base-FX 100Mbps 2000m

1000Base-LX 1000Mbps 3000m

Analogy for Bandwidth: Pipe

Analogy for Bandwidth

Brainstorming

• Highway

• Radio system

Highway Analogy for Bandwidth

Audio Analogy for Bandwidth

When we say our Lab is capable of 100Mbps, what do we call that

speed?

BandwidthDo we get the full 100Mbps?

No!What do we call what we actually get?

Throughput

Throughput

• 資訊抵達或經過網路系統中的某一特定點的速率 • The throughput is effected by:

– Internetworking devices

– Type of data being transferred

– Topology

– Number of users

– User's computer

– Server computer

– Power and weather-induced outages

<= Bandwidth<= Bandwidth

Time Calculations

The importance of Bandwidth

• Finite

• Save money

• A key measure of network performace

• A key to understanding the Internet

• Increases constantly

Maximum Bandwidths and Length Limitations

Typical Media Max. Theoretical Bandwidth

Max. Physical Distance

50-Ohm coaxial cable (thinnet)

10-100 Mbps 185m

75-Ohm coaxial cable (thicknet)

10-100 Mbps 500m

CAT5 UTP 10 Mbps 100m

CAT 5 (Fast Ethernet) 100 Mbps 100m

Multimode Fiber 100 Mbps 2000m

Singlemode Fiber 1000 Mbps (1 Gbps) 3000m

Wireless 11 Mbps A few hundred meters

WAN Services and Bandwidths

Type of Service

Typical User Bandwidth

Modem Individuals 56 Kbps

ISDN Telecommuters and small businesses 128 Kbps

Frame Relay Small institutions and reliable WANs56 Kbps to 1544

Mbps

T1 Larger entities 1.544 Mbps

T3 Larger entities 44.736 Mbps

STS-1 (OC-1) Phone companies/Backbones 51.840 Mbps

STS-3 (OC-3) Phone companies/Backbones 155.251 Mbps

STS-48 (OC-48)Phone companies/Backbones

2.488320 Gbps