網路概論Class 1-Protocols, Architecture and Tran

smission Media

授課老師楊人順

2001/09/26

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Presentation Outlines

• Network Classifications• Network Devices• Network Software• Network Topologies• Network Protocols• Switching Techniques• Group Discussion

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Network Classification in terms of transmission technology

• Switch (Inter-media) Network– Circuit-Switched Network

– Message-Switched Network

– Packet-Switched Network

– Virtual Packet-Switched Network

• Broadcast (non-inter-media) Network– LAN: Ethernet 10BASE5 and 10BASE2

– Packet Radio Network

– Satellite Network

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Network classification in term of scale

• Local Area Network (LAN)– Ethernet, Ether-switch– Token Ring, Token Bus– ATM LAN, Wireless LAN

• Metropolitan Area Network– DQDB

• Wide Area Network– ISDN, B-ISDN, Internet

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Network Devices

• Repeater : electronically repeating (信號放大 /電氣層隔離 ) (layer 1)

• Bridge : only to connect LANs with different/some protocol (實際地址登記辨識 /資料流隔離 )(layer 2)

• Router : Connect different Network (LAN, MAN, WAN) and routing + protocol transformation (layer 3)

• Gateway : Connect different Network (WAN-to-WAN) and protocol transformation (layer 3 or layer 4-7)

• Wireless Devices : wireless Hubs for LAN and Mobile communication systems

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Network Software• Telnet• FTP• Email• WWW• Teleshopping (SET-Secure Electronic Transactions安全電子交易 )

– 它是一個用來保護在任何網路上付款卡交易的開放式規格。 SET規格融合了從 RSA資料安全的公開鑰匙 (Public Key)編成密碼文件 (Cryptography)的使用，以保護任何開放型網路上個人和金融資訊的隱密性。

• Network Game• Video-on-Demand(隨選視訊 )• Video-Conference(視訊會議 )• Point-of-Sale(POS) accounting

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Network Topologies

• Point-to-point

• Multipoint Broadcast

• Switched Network

• Internet

(please referred as page 34 Figure 2.1)

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Network Protocols

• What is a Protocol ?– A communication language between one-to-one or among many

computers in hardware or software.– Why standardization ? (next slide)– Functions (pp.35-44)

• Encapsulation• Segmentation and reassembly• Connection control (pp.38 Figure 2.3)• Ordered delivery• Flow control• Error control• Addressing (pp. 41 Figure 2.4) and addressing modes (pp. 42 Table 2.1)• Multiplexing• Transmission services

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Why standardization

Standardprotocol

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Three Layer Protocol Model

Application

Transport

Network Access

Application

Transport

Network AccessCommunicationsNetwork

Application protocol

Transport protocol

Network accessprotocol

Network accessprotocol

A simplified layer model

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Why Layering

• Discussion :– Design: separate layers to handle different function,

and collect similar functions into the same layer

– Maintain: errors are easier to be located, each layer boundaries with its upper and lower layer only

– Replace: allow changes without affecting other layers

– software engineering issues

• Principles Used in Defining the OSI layers– (pp. 45 Table 2.2)

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Open System Interconnection (OSI)

• Developed by International Organization for Standardization.

• A reference model for current and future protocols• Layers Descriptions (three layer model OSI)

– Network access Physical, Data link and Network layers

– Transport Transport and Session layers– Application Presentation and Application layers

• OSI layer on network equipments (next slide)

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OSI Reference layers

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Transmission Control Protocol/Internet Protocol (TCP/IP)

Application

TCP

IP

Network access

PhysicalSubnet : Hardware and Firmware

Packet operations : addressing/routing, p-t-p link management and network resource managements

connection operations : end-to-end connection maintained, flow/error control and connection resource managements

Socket Interface

(OSI v.s. TCP/IP : pp.22 Figure 1.11)

(pp.59 Application protocols by using TCP/IP as platform)

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OSI v.s. TCP/IP

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Protocol Data Units (PDUs) Segment/Reassembly

Application data (application PDU)

Transport SDU Transport SDU

Network SDU Network SDU

Transportheader

Transportheader

Networkheader

Networkheader

Transport PDU Transport PDU

Network PDUNetwork PDU

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Why add Header and Tailor

• Addressing (next slide)

• Synchronization : Intra-Connection and Inter-Connection synchronization

• Flow and Error Control (Quality of Service)

• Other controls : packetization information

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Addressing Concepts

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Address Modes

Destination Network Address System Address Port/SAP Address

Unicast Individual Individual Individual

Individual Individual Group

Multicast Individual All Group

All All Group

Individual Individual All

Broadcast Individual All All

All All All

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Switching Techniques

• Circuit Switch

• Message Switch

• Packet Switch

• Virtual Packet Switch

Group Discussion