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1、协议基础 OSIModelOverview DataFlowLayers Transport Data Link Network Physical RoleofApplicationLayers TelnetFTP UserInterface Examples Application TelnetFTP ASCIIEBCDICJPEG UserInterface HowdataispresentedSpecialprocessingsuchasencryption Examples Presentation Application RoleofApplicationLayers TelnetF
2、TP ASCIIEBCDICJPEG Keepingdifferentapplications dataseparate UserInterface HowdataispresentedSpecialprocessingsuchasencryption OperatingSystem ApplicationAccessScheduling Examples Session Presentation Application RoleofApplicationLayers Keepingdifferentapplications dataseparate Userinterface Howdata
3、ispresentedSpecialprocessingsuchasencryption Transport Data Link Network Physical Examples Session Presentation Application RoleofApplicationLayers RoleofDataFlowLayers EIA TIA 232V 35 Examples Physical MovebitsbetweendevicesSpecifiesvoltage wirespeed andpin outcables 802 3 802 2HDLC EIA TIA 232V 35
4、 Examples RoleofDataFlowLayers DataLink Physical CombinesbitsintobytesandbytesintoframesAccesstomediausingMACaddressErrordetectionnotcorrection MovebitsbetweendevicesSpecifiesvoltage wirespeed andpin outcables 802 3 802 2HDLC EIA TIA 232V 35 IPIPX Examples RoleofDataFlowLayers Network DataLink Physi
5、cal CombinesbitsintobytesandbytesintoframesAccesstomediausingMACaddressErrordetectionnotcorrection MovebitsbetweendevicesSpecifiesvoltage wirespeed andpin outcables Providelogicaladdressingthatroutersuseforpathdetermination TCPUDPSPX 802 3 802 2HDLC EIA TIA 232V 35 IPIPX Examples RoleofDataFlowLayer
6、s Transport DataLink Physical ReliableorunreliabledeliveryErrorcorrectionbeforeretransmit CombinesbitsintobytesandbytesintoframesAccesstomediausingMACaddressErrordetectionnotcorrection MovebitsbetweendevicesSpecifiesvoltage wirespeed andpin outcables Network Providelogicaladdressingthatroutersusefor
7、pathdetermination TCPUDPSPX 802 3 802 2HDLC EIA TIA 232V 35 IPIPX Presentation Application Session Examples RoleofDataFlowLayers ReliableorunreliabledeliveryErrorcorrectionbeforeretransmit CombinesbitsintobytesandbytesintoframesAccesstomediausingMACaddressErrordetection notcorrection Movebitsbetween
8、devicesSpecifiesvoltage wirespeed andpinoutcables Transport Data Link Physical Network Providelogicaladdressingthatroutersuseforpathdetermination EncapsulatingData Transport Data Link Physical Network Upper LayerData Upper LayerData TCPHeader Data IPHeader Data LLCHeader 0101110101001000010 Data MAC
9、Header Presentation Application Session Segment Packet Bits Frame PDU Upper LayerData De encapsulatingData LLCHdr IP TCP Upper LayerData MACHeader IP TCP Upper LayerData LLCHeader TCP Upper LayerData IPHeader Upper LayerData TCPHeader 0101110101001000010 Transport Data Link Physical Network Presenta
10、tion Application Session TCP IPProtocolStack 7 6 5 4 3 2 5 4 3 2 Application Presentation Session Transport Network Data Link Physical 1 Application Transport Internet Data Link Physical 1 ApplicationLayerOverview UsedbytheRouter Application Transport Internet Data Link Physical FileTransfer TFTP FT
11、P NFSE Mail SMTPRemoteLogin Telnet rlogin NetworkManagement SNMP NameManagement DNS TransportLayerOverview TransmissionControlProtocol TCP UserDatagramProtocol UDP Application Transport Internet Data Link Physical Connection OrientedConnectionless TCPSegmentFormat SourcePort 16 DestinationPort 16 Se
12、quenceNumber 32 HeaderLength 4 AcknowledgmentNumber 32 Reserved 6 CodeBits 6 Window 16 Checksum 16 Urgent 16 Options 0or32ifAny Data Varies 20Bytes Bit0 Bit15 Bit16 Bit31 PortNumbers TCP PortNumbers FTP TransportLayer TELNET DNS SNMP TFTP SMTP UDP ApplicationLayer 21 23 25 53 69 161 RIP 520 TCPPortN
13、umbers SourcePort DestinationPort HostA 1028 23 SP DP HostZ TelnetZ Destinationport 23 SendpackettomyTelnetapplication SendSYN seq 100ctl SYN SYNReceived HostA HostB TCPThree WayHandshake OpenConnection SendSYN seq 100ctl SYN SYNReceived SendSYN ACK seq 300ack 101ctl syn ack HostA HostB SYNReceived
14、TCPThree WayHandshake OpenConnection SendSYN seq 100ctl SYN SYNReceived SendSYN ACK seq 300ack 101ctl syn ack Established seq 101ack 301ctl ack HostA HostB SYNReceived TCPThree WayHandshake OpenConnection TCPSimpleAcknowledgment WindowSize 1 Sender Receiver TCPSimpleAcknowledgment WindowSize 1 Sende
15、r Receiver Send1 Receive1 TCPSimpleAcknowledgment WindowSize 1 Sender Receiver Send1 Receive1 ReceiveACK2 SendACK2 TCPSimpleAcknowledgment WindowSize 1 Sender Receiver Send1 Receive1 ReceiveACK2 SendACK2 Send2 Receive2 TCPSimpleAcknowledgment WindowSize 1 Sender Receiver Send1 Receive1 ReceiveACK2 S
16、endACK2 Send2 Receive2 ReceiveACK3 SendACK3 TCPSimpleAcknowledgment WindowSize 1 Sender Receiver Send1 Receive1 ReceiveACK2 SendACK2 Send2 Receive2 ReceiveACK3 SendACK3 Send3 Receive3 WindowSize 1 Sender Receiver Send1 Receive1 ReceiveACK2 SendACK2 Send2 Receive2 ReceiveACK3 SendACK3 Send3 Receive3 ReceiveACK4 SendACK4 TCPSimpleAcknowledgment TCPSequenceandAcknowledgmentNumbers SourcePort DestinationPort Sequence Acknowledgment Source Dest Seq Ack 1028 23 10 1 Ijustsentnumber10 TCPSequenceandAck
