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. Computer Networking. . . . . DI. 1. 2. 3. CHAPTER 4 Introduction to Protocols. The first section. Exercises. Online lecture. Homes. Buildings. Appliances. . . . Computers. People. Transportation Vehicles. $. Vending Machines. Smart Cards. - PowerPoint PPT Presentation

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Computer Networking

DI1The first section2Exercises3Online lectureCHAPTER 4Introduction to ProtocolsDepartment of Computer Networking Application Network Management and Operation

2www.gxmu.edu.cnChapter 4 Introduction to Protocols4-1 Introduction 4-2 A Definition of the Need for Protocols4-3 A Simple Protocol Suite4-4 Protocol Layers 4-5 Protocol Functions 4-6 Transport Protocols4-7 Data Link Protocols Network Management and Operation

4outline [`autlain]n. definition [,defi`nin]n., suite [swi:t]n. function[fkn]n.www.gxmu.edu.cnKEY TERMSApplication layer Fragmentation Segmentation Check character Multiplexing Transport layer Connectionless Network access layer Connection-oriented UDPTDP PDU Virtual circuit

Chapter 4 Introduction to Protocols Network Management and Operation

5term [t:m]n.; segmentation [,semn`tein]n. check character fragmentation [,frmen`tein]n., www.gxmu.edu.cn4.1 INTRODUCTION1The concept of protocols.

3The principles of protocols2The need for protocolsTcp/ip will be used as an example Chapter 4 Introduction to Protocols Network Management and Operation

6principle [`prinspl]n., TCP/IP www.gxmu.edu.cn4-2 A DEFINTION AND THE NEED A protocol is a set of rules or guidelines that govern the interactions between people, between people and machines, or between machines.

*

*Communications protocols define what needs to be done but not how to do it.FChapter 4 Introduction to Protocols Network Management and Operation

7guidelines n. govern [`vn]vt. & vi. interaction [,ntr`kn]n., , machine [m`i:n]n.,4.14.2

www.gxmu.edu.cnWhy must Protocols for computer communication be more precisely defined than the protocols humans use?Because computers dont have the human ability to interpret subtleties in the tone of a voice or to apply judgment when unusual or unexpected events occur.Chapter 4 Introduction to Protocols Network Management and Operation

8precisely [pri`saisli]adv.; to interpret subtlety [`stlti]n. judgment [ddmnt]n. unusual [nju:ul]adj.,unexpected [,nik`spektid]adj. occur [`k:]vi.; precisely [pri`saisli]adv. , subtlety [`stlti]n., judgment [,ddmnt]n. define [di`fain]vt.4.10www.gxmu.edu.cn Where is protocols Protocols are most often implemented in software and layers.

The binding protocolsProtocols with the network card driverA number of protocols can be bundled with a card An agreement can bind to multiple card

Chapter 4 Introduction to Protocols Network Management and Operation

9stack [stk]vt. & vi. implement [`implimnt]vt. developed [di`velpt]adj.

www.gxmu.edu.cnWhy protocols layered ?

To make it easy to develop ,test, and modify the protocol software,it is generally developed layer by layer.

N-1

N-1

systemAsystemBN+1 NN+1 NN+1Protocol NProtocolN-1ProtocolChapter 4 Introduction to Protocols Network Management and Operation

10stack [stk]vt. & vi.www.gxmu.edu.cnProtocol stack(Protocol Suite ) A protocol stack is the collection of software modules that implement a protocol.This collection of software modules is normally call a protocol stack.

TCP/IPIPX/SPXAppleTalk etc Network Management and Operation

11module [`mdju:l]n., implement [`implimnt]vt. stack [stk]vt. & vi. suite [swi:t]n.,www.gxmu.edu.cnThe Principle of Peer layer communicationBan on direct communication between the peer layers (WHY?)Each layer must rely on the lower layer of the services provided.

Network Management and Operation

12ban [bn]vt., rely on , www.gxmu.edu.cn Grammar what to do

Semantics how to do HDLCFlag(7EH)BSCSOH(01H)STX(02H)ETX(03H)

Timing when to do

Telephone Traffic lights

Protocol Three elements FlagAddressCtrlDataFCSSFlagSOHHEADSTXTEXTETXBCCBSCHDLC Network Management and Operation

13element [`elimnt]n.() grammar [`rm]n. semantics [si`mntiks]n. timing [`taimi]n. HDLCHigh Level Data Link Control

IBMBSC

5-8

www.gxmu.edu.cnTIMING SAMPLE

Chapter 4 Introduction to Protocols Network Management and Operation

14----------Acknowledgement [k`nlidmnt]n.,-------www.gxmu.edu.cn4-3 A SIMPLE PROTOCOL SUITEA hypothetical protocol suite that has some similarity to TCP/IP.Application : Don`t deal directly with all the intricacies of the communication process.Communication services: Collection of activities .Network access: E-mail commands and data are exchanged .Chapter 4 Introduction to Protocols Network Management and Operation

15hypothetical [,haipu`etikl]adj. intricacy [`intriksi]n.,TCP/IP

4.8

www.gxmu.edu.cnFigure 4-1 The layers of a hypothetical protocol.

Chapter 4 Introduction to Protocols Network Management and Operation

16Protocol stack

www.gxmu.edu.cnFigure 4-2 The flow of data and commands in the protocol stack.

Chapter 4 Introduction to Protocols Network Management and Operation

17flow [flu]vi., 12A.B.2

Tangzhong Network Management and Operation

18:

www.gxmu.edu.cnTCP/IP Protocol SuiteTCPIGMPARPRARPICMPIPUDPSMTPDNSSNMPFTPUnderlying-LayerLAN or WAN TechnologyChapter 4 Introduction to Protocols Network Management and Operation

www.gxmu.edu.cn4-4 PROTOCOL LAYERSPDU (Protocol Data Unit):The combination of data from the next higher layer and the header from the current layer is called a PDUPDU =HEADER+DATA

Each layer of the smallest unit of data transmission The header in a PDU contains information to be used by the peer layer in the receiving computerChapter 4 Introduction to Protocols Network Management and Operation

20combination [,kmbi`nein]n., , current [`krnt]adj. layer [`lei]n.,

PDU

www.gxmu.edu.cnFigure 4-3 Examples of the data contained in the headers of the transport and network access PDUs.

* Error detection codes are typically the result of a mathematical function performed on the contents of an entire message. F (the remainder of the PDU that has been calculated by the sending transport layer.)

Chapter 4 Introduction to Protocols Network Management and Operation

21PDUcontained [kn`teind]v.++PDU PDU+PDU PDU PDU

Error detection codes are typically the result of a mathematical function performed on the contents of an entire message. FPDU

www.gxmu.edu.cnApplicationMessageTransportSegment NetworkPacket()Data linkFramePhysical LinkBitPDU specific namesChapter 4 Introduction to Protocols Network Management and Operation

www.gxmu.edu.cn4-5 PROTOCOL FUNCTIONS Encapsulation Fragmentation and reassemblyConnection controlOrdered deliveryFlow controlError controlAddressingMultiplexingTransmission services

Chapter 4 Introduction to Protocols Network Management and Operation

23function [`fkn]n.; ; encapsulation [in,kpsju`lein]n. fragmentation [,frmen`tein]n. reassemble [,ri:`sembl]vt connection [k`nekn]n., Ordered delivery [di`livri] Flow control error control addressing [`dresi]n. multiplexing [,mltipleksi]n. Transmission services www.gxmu.edu.cnThe process of adding control information to data from a higher layer is called encapsulation.De-encalsulation.Encapsulation: control info+data

DATAHEAD()DATA4.5.1EncapsulationChapter 4 Introduction to Protocols Network Management and Operation

24encapsulation [in,kpsju`lein] n.,PDU

www.gxmu.edu.cnControl information Three general categories1)Address PDU headers often contain both the senders and receivers addresses. The address field in a header tells the destination of a message or PDU.2)Error detection code. Typically a mathematically calculated check sum.3)Protocol control. additional information

Chapter 4 Introduction to Protocols Network Management and Operation

25general [`denrl]adj. category [`ktiri]n., destination [,desti`nein]n. typically [`tipikli]adv.,mathematical [,mi`mtikl]adj. sum [sm]n.

PDU--check sum -www.gxmu.edu.cnEncapsulation example

Chapter 4 Introduction to Protocols Network Management and Operation

www.gxmu.edu.cn4.5.2 Fragmentation and ReassemblyFragmentation Various levels of the protocol may require that the PDU be broken into smaller blocks. This process is call either fragmentation or segmentation. Fragmentation= Segmentation

*Segmentation is the error control process that is employed when only part of a message is delivered to the receiver. FChapter 4 Introduction to Protocols Network Management and Operation

27fragmentation [,frmen`tein] segmentation [,semn`tein]n. n.reassemble [,ri:`sembl]vt., vi. employe [im`plii]n., PDU www.gxmu.edu.cnWhy Fragment?AdvantagesMore efficient error controlMore equitable access to network facilitiesShorter delaysSmaller buffers needed

DisadvantagesResults in more overheads.Less efficient transmission.More processing timeChapter 4 Introduction to Protocols Network Management and Operation

28fragment [`frmnt]n.equitable [`ekwitbl]adj., facility [f`siliti]n. , overheads n. , (4096

Chapter 4 Introduction to Protocolswww.gxmu.edu.cnReassemblyThe process of reassembling a message that has been fragmented is called reassembly.

At the receiving end,the fragmented data must be reassembled into messages corresponding to those that were originally sent by the application level. Network Management and Operation

29reassemble [,ri:`sembl]vt., vi. fragmented [fr`mentid,`frmntid]adj.correspond [kris`pnd]vi.with

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