network = net + work what is flowing ? what different forms flow ? what rules govern flow ? where...
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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
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