Computer Networking

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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 [àutlain]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 [mì: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


9stack [stk]vt. & vi. implement [ìmplimnt]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 [ìmplimnt]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 [èlimnt]n.() grammar [`rm]n. semantics [si`mntiks]n. timing [`taimi]n. HDLCHigh Level Data Link Control

IBMBSC

5-8

www.gxmu.edu.cnTIMING SAMPLE


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 [,haipuètikl]adj. intricacy [ìntriksi]n.,TCP/IP

4.8

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


16Protocol stack

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


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

Tangzhong Network Management and Operation

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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.)


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


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


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


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 [èkwitbl]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

www.gxmu.edu.cnSegmentation and Reassembly

PDUNPDUN-1HPDUN-1HPDUNPDUNHPDUNHH

Figure 4-4 An illustration of message fragmentation and reassembly. Chapter 4 Introduction to Protocols Network Management and Operation

30segmentation [,semn`tein]n. reassemble [,ri:`sembl]vt., vi.0>400040003000 TH1 TH2.NAH1 NAH2270001www.gxmu.edu.cnChapter 4 Introduction to Protocols Network Management and Operation

www.gxmu.edu.cnFlow of data in the OSI model123456AP1AP2123456H4H3H2T21010011010111010H5H612


header

32www.gxmu.edu.cn TCP HEADIP HEADLLC HEAD0101110101001000010MAC HEAD

segmentpackageframePDUFCSFCSPDUs in TCP/IPByteChapter 4 Introduction to Protocols Network Management and Operation

33www.gxmu.edu.cnConnection is usually a logical association between the entities Virtual circuit

Connection-oriented setup time at the beginning of the communication.Key attribute :Assigns sequence numbers to each PDU. Sequence numbers used for Ordered delivery Flow control Error control

4.5.3 Connection ControlChapter 4 Introduction to Protocols Network Management and Operation

34logical [`ldikl]adj. association [,suièin]n., entity [èntiti]n. attribute [`tribju:t]vt.; assign [`sain]vt.;sequence [`si:kwns]n., sequence number n. delivery [di`livri]n., PDUPDUPDUwww.gxmu.edu.cnConnectionless

No setup timeallows an application to send a message to any destination ,an any time.

UDPIn the TCP/IP protocol suite, connectionless transport is provided by the UDP .Chapter 4 Introduction to Protocols Network Management and Operation

35destination [,desti`nein]n., provided [pr`vaidid]conj.,Vt www.gxmu.edu.cn4.5.4 Ordered DeliveryPDUS may be out of sequence,why?

The PDUs take different paths (routes) through several networks.How to do ? Sequence numbers Chapter 4 Introduction to Protocols Network Management and Operation

36Sequence Number sequence [`si:kwns]n.PDUs can arrive at the destination out of sequence because _____. they take different routes through the network4.17 PDUPDUPDUPDUwww.gxmu.edu.cnSequence numbers function The sequence numbers in PDUs serve multiple purposes because they allow the receiving end to check to ensure that all PDUs have been received, that they are in the right sequence, and that none have been duplicated.


37sequence [`si:kwns]n., duplicate [`dju:plikit]n., none [nn]pron.

PDUPDU4.18 PDUPDUPDUwww.gxmu.edu.cn4.5.5 Flow ControlWhy is Flow control required in computer based communication systems because sometimes the sending computer transmits data at a rate faster than the receiving computer can handle it.

The term used to describe the ability of the receiving end of the transmission to limit the amount or rate of data sent by the transmitting end is flow control.Chapter 4 Introduction to Protocols Network Management and Operation

38 amount [`maunt]n. rate [reit]n., (); www.gxmu.edu.cn

Flow ControlStop and wait Xon/Xoff ACK/NAKSliding window Fixed window size Credit scheme


39PDU PDU-PDUPDUSliding window www.gxmu.edu.cn4.5.6 Error ControlGuard against loss or damage at various levels

Types of ErrorsDetectionCorrection


40guard against , various [`vris]adj.PDU PDU PDUwww.gxmu.edu.cnError ControlAll transmission media have potential for introduction of errors.Error Control refers to the facts that errors must be:Detected reliablySomething should be done to retransmit the frame that has been received in errorChapter 4 Introduction to Protocols Network Management and Operation

41potential [p`tenl]adj.,

www.gxmu.edu.cn

Single-bit errorMultiple-bit error

Burst error

Types of ErrorsChapter 4 Introduction to Protocols Network Management and Operation

42burst error www.gxmu.edu.cnDefineError controlError correctionError detectionError detection is usually accomplished by having the sender insert an error detecting code.


43

4.7 PDU

www.gxmu.edu.cnCheck character Error detecting code=check character It is calculated mathematically as a part of the error checking process when transmitting and receiving a message.

*An error detection code corrects all of the errors it finds during a transmission.FChapter 4 Introduction to Protocols Network Management and Operation

44=

www.gxmu.edu.cnParity Examples - Using Even Parity

Simple ParityLRC/VRC


45parity [`priti]n., Simple Parity LRC: Longitudinal Redundancy Check

VRC: 4.16 1001011010010100111

www.gxmu.edu.cnError correctionRetransmission.If no acknowledge in given time, re-transmit.Sequence numberingDuplicate PDUs discard


46retransmission [,ri:trnz`min]n., sequence number n. duplicate[dju:plikit]n., discard [dis`k:d]vt.acknowledge [k`nlid]vt., www.gxmu.edu.cnNOTENetwork access layer : Each PDU is received correctly.Transport layer : All PDUs are received and that none are duplicated.Chapter 4 Introduction to Protocols Network Management and Operation

47PDUwww.gxmu.edu.cn4.5.7 AddressingPDU headers often contain both the sender`s and receiver`s addresses.Different layers of the protocol contain different addresses.Addresses are unique and not [email protected] LayerEmail application addressNetwork access layerIp addressChapter 4 Introduction to Protocols Network Management and Operation

48ambiguous [m`bijus]adj. [q y]; , The transport header contains the address of the email application on the receiving computer that is to process the data.4.14 PC

www.gxmu.edu.cn4.5.8MultiplexingWhen a computer uses a single communications circuit to establish multiple connections to different applications.

Many to one/one to manySupporting multiple connections on one machineChapter 4 Introduction to Protocols Network Management and Operation

49multiplexing [`mltipleksi]n. establish [is`tbli]vt., When a computer uses a single communication circuit to establish multiple connections to different applications, it is called Multiplexing.ftpwww.gxmu.edu.cnMultiplexing vs. No Multiplexing

Types of multiplexing

Network Management and Operation

50FDMFrequency-division multiplexing TDM www.gxmu.edu.cnFigure 8-3WCB/McGraw-Hill The McGraw-Hill Companies, Inc., 1998Multiplexing, Frequency DomainFDM

FDM, Time Domain

Demultiplexing, Time DomainChapter 4 Introduction to Protocols Network Management and Operation

51time domain www.gxmu.edu.cn4.5.9 Transmission ServiceA protocol may provide transmission services such as a. the ability to prioritize messagesb. the ability to specify required throughput ratesc. the ability to provide some kind of security to the message


52prioritize [prai`ritaiz]vt. throughput [`ru:put]n.,,

www.gxmu.edu.cnSummarySimplified hypothetical model .To help us learn the concepts of protocols.Chapter 4 Introduction to Protocols Network Management and Operation

www.gxmu.edu.cn4.6 Transport protocolsThe major function and responsibility To assure that messages are exchangeed reliably between the sender and the receiver.

Two primary elements :1)the arrival of all of the data at the destination.2) their presentation to the receiving application in the same order the sending application intended. Provide an end-to-end data transfer service.


5412 www.gxmu.edu.cnProvide the two types of serviceConnection-oriented serviceHave setup time at the beginning of the communication.

TCP FTPTelnetSMTPHTTPPOP3A telephone call is an example of a connection-oriented service.Chapter 4 Introduction to Protocols Network Management and Operation

55Virtual [`v:tjul]adj.circuit www.gxmu.edu.cn3-way handshake

Connection-oriented serviceChapter 4 Introduction to Protocols Network Management and Operation

56TCP/IPTCP syn(syn=j)SYN_SEND synSYNack=j+1SYNsyn=kSYN+ACKSYN_RECV SYNACKACK(ack=k+1)ESTABLISHED www.gxmu.edu.cnConnectionless service

UDPNo setup time at the beginning of the communication.Allows an application to send a message to any destination ,at any time. don`t guarantee the delivery of a message. UDP DNSSNMPQQ


57guarantee [,rn`ti:]vt.; sequence number n.

www.gxmu.edu.cnPort Port The process of distinction

The only signs=hostip+porthttp://10.100.48.100:8080


58distinction [distikn]n.www.gxmu.edu.cnAdv: There is no setup time at the beginning of the communication.Disadv: There is no guarantee that a message will be delivered.


www.gxmu.edu.cnService process normally use a fixed port. RPCSNMPTFTPSMTPFTPTelnet11116169252123UDPTCPIPChapter 4 Introduction to Protocols Network Management and Operation

www.gxmu.edu.cnFTPSMTPTFTPDNSTelnetSNMP2123255369161TCP UDPapplicationtransport layerportTCP and UDP Principle of transmission of information Chapter 4 Introduction to Protocols Network Management and Operation

61TCPUDP(port)

www.gxmu.edu.cn

Port AddressesChapter 4 Introduction to Protocols Network Management and Operation

www.gxmu.edu.cn4-7 DATA LINK PROTOCOLSThe major function :To deal with the specifics of the particular type of circuit that used between the sender and receiver and to ensure that each PDU arrives accurately and with no errors.Not concerned : Sequence duplicated missing.Chapter 4 Introduction to Protocols Network Management and Operation

634.15particular [p`tikjul]adj., accurately PDUPDU PDU A major function of data link protocols is to ensure that each PDU arrives accurately and with no errors.TData link protocols do not concerned with whether PDU`s arrive in sequence.

www.gxmu.edu.cnSituations that occur during data communicationcommunication startup character identificationPDU identification Error controlTermination


64situation [,sitjuèin]n.; identification [ai,dentifi`kein]n., occur [`k:]vi. termination [`t:mnein]n., --PDU,---www.gxmu.edu.cnSUMMARYhas introduced information about the various protocols that are required to make a communication system work.TCP/IP has become very widely used .Chapter 4 Introduction to Protocols Network Management and Operation

65various [`vris]adj., foundation [faun`dein]n., This chapter has introduced information that gives you foundation information about the various protocols that are required to make a communication system work.A address2. The _____ field in a header tells the destination of a message or PDU. .AB destinationD block checkC segmentationAnswerRedoNextChapter 4 Introduction to Protocols Network Management and Operation

D multiplexing.3. When a computer uses a single communication circuit to establish multiple connections to different applications, it is called .DAmulticastingB multitaskingC multiprogrammingAnswerRedoNextChapter 4 Introduction to Protocols Network Management and Operation

D b, and c.4. Protocols are most often implemented in .DAhardwareB softwareC layersAnswerRedoNextChapter 4 Introduction to Protocols Network Management and Operation

C the peer layer in the receiving computer5. The header in a PDU contains information to be used by .CA the user at the receiving endB the owner of the communications circuiD the workstation at the transmitting endAnswerRedoNextChapter 4 Introduction to Protocols Network Management and Operation

6. The transmitter or sender of a message is also called the ________

sourceAnswer7.The vehicle through which a message travels from sender to receiver is called the ______________ .

mediumAnswer8.A set of rules that guide the progress of a message from sender to receiver is called a ______________ .

protocolAnswerChapter 4 Introduction to Protocols Network Management and Operation

9. The company that passed up the opportunity to own the basic patents on the telephone was ___________ .

Western UnionAnswer10.Signals that are continuous are called_________________,.

analog signals AnswerChapter 4 Introduction to Protocols Network Management and Operation

www.gxmu.edu.cnThank You !

Tangzhong Network Management and Operation

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