1、12Serial Point-to-Point ConnectionsRouter connectionsNetwork connections at the CSU/DSUEIA/TIA-232EIA/TIA-449EIA-530V.35X.21CSU/DSUEnd user deviceService ProviderDTEDCE3Point-to-point orcircuit-switched connectionCO SwitchCustomer Premises EquipmentDemarcationLocal LoopWAN service provider toll netw

2、orkTrunks and switchesProvider assigns connection parameters to subscriberSSSSSSS45678910Layer 2 DesignDetermining the size of collision domains in hubbed and switched networks 11Layer 2 Design Diagramming hub placement in a standards-based extended star topology 12ARP地址解析協議知道IP地址，找MAC地址13Address Re

3、solution Protocol172.16.3.1172.16.3.2IP: 172.16.3.2 = ?I need the Ethernet address of 176.16.3.2.14Address Resolution Protocol172.16.3.1IP: 172.16.3.2 Ethernet: 0800.0020.1111172.16.3.2IP: 172.16.3.2 = ?I need the Ethernet address of 176.16.3.2.I heard that broadcast. The message is for me. Here is

4、my Ethernet address.15Address Resolution ProtocolMap IP EthernetLocal ARP172.16.3.1IP: 172.16.3.2 Ethernet: 0800.0020.1111172.16.3.2IP: 172.16.3.2 = ?I need the Ethernet address of 176.16.3.2.I heard that broadcast. The message is for me. Here is my Ethernet address.Example 1: Destination local16Fin

5、ding the MAC AddressRouter AExample 2: Destination not localHost ZHost YQueryBroadcastHost ZMAC ?Host ZResponseHost YMACRouter AMACRouting Table:Net forHost ZMap IP EthernetNot Local ARP17廣播 單播 能收到 能收到 能收到 收不到 收不到 收不到 HUBSWITCHROUTERA 與B通信，C是否收到？（集線器 交換機 路由器的區別）18Half-duplex EthernetEthernet is a ha

6、lf-duplex technology Most important are receive(RX),transmit(TX),and collision detection Ethernet physical connector provides several circuits19Ethernet 10BaseT transmission time Packet size in bytesTransmission time in ms6451.25124101000800151812142021 Microsegmentation Dedicated paths between send

7、ing and receiving hosts22LAN segmentation with bridges 23 How a switch learns addresses Learns a stations location by examining the source addressSend out all ports when the destination address is a broadcast, multicast or unknown address (except the port that the frame enter)Forward when the destination is located a different interfaceFilters when the destination is located on the same interface2425 Two switching methods PreambleSFDDestination hardwareAddressSourceHardwareAddressLengthDATAFCS7bytes 1byte 6bytes 6bytes 2bytes 46-1500 4bytesDefault switching: cut-through no error checking