数字数据通信网络基本概念.ppt

Need for Connectivity Devices Overcome the limitations of the LAN media Transport of data packets across multiple networks with different media access methods Communication between systems with incompatible protocols Network Device and OSI 1980 1986 1995 2000 2005 Layer 1 Layer 2 Layer 3 Layer 4 Layer 7 Repeater Preamble SFD Data Source Port Destination Port Sequence Number Acknowledge Number Window F I N S Y N R S T P S H A C K U R G Data Offset Reserved Checksum Urgent Pointer Options Padding Data ... FTP Server WWW Layer 3 Switch Router Metro Ethernet Switch V Total Length Identification TTL Source Address Data ... IHL TOS Fragment Offset Flags Protocol Header Checksum Destination Address Options Padding Bridge Layer 2 Switch DA SA L/T Data Pad FCS 8100 TCI 802.1Q VLAN tagging Repeater/Hub Application Presentation Session Transport Network Data Link Physical Application Presentation Session Transport Network Data Link Physical Repeaters work at layer 1 of the OSI model Their primary function is to regenerate signal Repeater Physical Physical Repeater/Hub Physical Layer devices. Protocol Independent. Interconnect two or more network segments (with the same type) to be a larger network segment. Regenerates the received digital signals. Does not process the received frames Repeater/Hub (5-4-3 Rule) Reperter Reperter Reperter Reperter IRL IRL DTE 1 DTE 1 DTE 2 DTE 3 IRL = Inter Reperter Length Hub (5-4 Rule) 10M Hub 10M Hub 10M Hub 10M Hub Station Station . . . 100meter 100meter 100meter 100meter 100meter 100meter 100meter Shared Network Collision Domain 10Base2 10Base5 10BaseT 100BaseT Hub Hub Hub CSMA/CD Share 10Mbps or 100Mbps Bridge/Switch Application Presentation Session Transport Network Data Link Physical Application Presentation Session Transport Network Data Link Physical Bridges work at layer 2 of the OSI model Their primary function is to relay frame Bridge Physical Data Link Physical Data Link Bridge/Switch MAC Layer devices Protocol Indep