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MAC addresses are mapped to outgoing ports in the Forwarding TableIf an address is not found in the Forwarding Table, then the frame is broadcast out all ports (that is, switch reverts to acting like a hub).If frames are received on more than 1 port at the same time, this is no problem. Each is buffered and forwarded individually.Devices connected to a switch are in different collision domainsEach switch port defines a separate collision domainDevices connected to a switch are in the same broadcast domainSwitch will forward a layer 2 broadcast frame out every port except the one it came in on.Rami Ghannam, DePaul University98TDC 413
Switched EthernetData delivery via intelligent switchEthernet SwitchTwisted Pair#4#3#2#1Example: PC #1 puts MAC address “#2” into Destination Address field of Ethernet header and transmits data frame to SwitchSwitch checks its MAC Forwarding Table and ONLY transmits data frame to #2.TDC 413Rami Ghannam, DePaul University99
IP RouterOperates at Layers 1, 2 and 3IP packets received on any port are stored temporarily in a memory buffer and sent out an interface determined by the destination IP address in the IP header.IP subnets are mapped to outgoing interfaces in the Routing TableIf an address is not found in the Routing Table, then If there is a default route, then the packet is forwarded based on this route.If no default route, the packet is dropped and an ICMP error message sent back to the sender. If frames are received on more than 1 port at the same time, this is no problem. Each is buffered and forwarded individually.Devices connected out different router ports are in differentcollision domains and differentbroadcast domainsRouters do not forward layer 2 broadcast framesRami Ghannam, DePaul University100TDC 413
Decision Factors in Physical Plant102•Network topology•Cost per location•Distance Limitations•Other Limitations (interference)•Bandwidth (data flows, type)TDC 413Rami Ghannam, DePaul University
Ethernet Physical StandardsEthernet can run over several different types of physical cables (copper wire, coaxial cable, optical fiber) at several different transmission rates (10 Mbps, 100 Mbps, 1 Gbps, 10 Gbps)For each (cable type, data rate) pair, there is a unique layer 1 (physical) Ethernet standarddefined by the IEEE 802.3 committeeThere is only one layer 2 Ethernet standard, specifying packet header format, access methods, switch operations, that works over any of these different physical networks.