DataTransferin Layered model The unit of data send between peer entities is called aProtocol Data Unit(PDU，协议数据单元）N LayerN LayerPDUAB(atiayerN)EntityEntity Scenario: Layer-N at A sends a layer-N PDU to layer-Nat B
The unit of data send between peer entities is called a Protocol Data Unit (PDU，协议数据单元 ) Scenario: Layer-N at A sends a layer-N PDU to layer-N at B N Layer Entity PDU (at layer N) N Layer Entity A B
Encapsulation andDemultiplexing封装与拆封 As data is moving down the protocol stack, eachprotocol is adding layer-specific control informationUserdataHTTPHTTP Header+UserdataTCP+TCPHeaderHTTPHeaderUserdataIPTCPsegmentIP HeaderTCPHeaderHTTPHeaderUserdataEthernetIPdatagramEthernetEthernetIPHeaderTCPHeaderHTTPHeaderUserdataHeaderTrailerEthernetframe
As data is moving down the protocol stack, each protocol is adding layer-specific control information HTTP TCP IP Ethernet User data HTTP Header User data TCP Header IP Header TCP Header IP Header TCP Header Ethernet Header Ethernet Trailer IP datagram TCP segment Ethernet frame HTTP Header User data HTTP Header User data HTTP Header User data
Example of data transferHTTPHTTPHTTPprotocol全TCPTCPTCPprotocol??IPIPIPIPprotocolIPprotocol??EthernetEthernetEthernetEthernet-Ethernet→-Ethernet→argon.tcpip-neon.tcpip-lab.edurouter71.tcpip-router137.tcpiplab.edu128.143.71.21lab.edulab.edu128.143137.144128.143.137.1128.143.71.100:e0:f9:23:a8:20
HTTP TCP IP argon.tcpip- lab.edu 128.143.137.144 Ethernet Ethernet Ethernet IP HTTP TCP IP neon.tcpip-lab.edu 128.143.71.21 Ethernet router71.tcpip- lab.edu 128.143.137.1 00:e0:f9:23:a8:20 router137.tcpip- lab.edu 128.143.71.1 HTTP protocol TCP protocol IP protocol Ethernet IP protocol Ethernet
Example of data transferHTTPHTTPSend HTTP Reguesttoneon?AEstablishaconnectiontoTCPTCPOpen TCp connection to28an128.143IP datagram is a TCP金金segment for port 80SendSend IP datagrIPIPto 128.143.71.21COn128.143.71.21Frame is an IPFrameisanIPdatagramdatagramSend the datagram tosendtheEthernetnelgram128.143.72LO-lab.eduardrouteFpi1.tcpiper7Send Ethernet frameSend Ethernetframe43.71.21ab.edulab.to128.10oce0:f9:23:a8:20o. 743.137.1128. 00.20.af:03:98:2800:e0:f9:23:a8:20
HTTP TCP IP argon.tcpip- lab.edu 128.143.137.144 Ethernet Ethernet Ethernet IP HTTP TCP IP neon.tcpip-lab.edu 128.143.71.21 Ethernet router71.tcpip- lab.edu 128.143.137.1 00:e0:f9:23:a8:20 router137.tcpip- lab.edu 128.143.71.1 Send HTTP Request to neon Establish a connection to 128.143.71.21 at port 80 Open TCP connection to 128.143.71.21 port 80 Send a datagram (which contains a connection request) to 128.143.71.21 Send IP datagram to 128.143.71.21 Send the datagram to 128.143.137.1 Send Ethernet frame to 00:e0:f9:23:a8:20 Send Ethernet frame to 00:20:af:03:98:28 Send IP data-gram to 128.143.71.21 Send the datagram to 128.143.7.21 Frame is an IP datagram Frame is an IP datagram IP datagram is a TCP segment for port 80
NetworkDevicesNetwork devices are components used to connectcomputers or other electronic devices together Besides the various modems for connecting intoInternet, the following devices are most commonlyused. NIC( Network Interface Card)。 Hub。Switch。Router
Network devices are components used to connect computers or other electronic devices together Besides the various modems for connecting into Internet, the following devices are most commonly used. ◦ NIC( Network Interface Card) ◦ Hub ◦ Switch ◦ Router