TDC 363 Greg Brewster, DePaul University 87
IP Router Operates at Layers 1, 2 and 3 IP 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 Table If 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 different collision domains and different broadcast domains Routers do not forward layer 2 broadcast frames Greg Brewster, DePaul University 88 TDC 363
Forwarding Example: Client #1 sends to Web Server Greg Brewster, DePaul University 89 IP RouterWeb ServerIP 126.96.36.199MAC 00:01:02:03:04:22Interface Fa0/0IP 188.8.131.52MAC 00:01:02:03:04:02Interface Fa0/1IP 184.108.40.206MAC 00:01:02:03:04:11Client #1IP 220.127.116.11MAC 00:01:02:03:04:09Client #3IP 18.104.22.168MAC 00:01:02:03:04:07EthernetHubEthernetHubClient #2IP 22.214.171.124MAC 00:01:02:03:04:06EthernetSwitchFa0/0Fa0/1Fa0/2TDC 363
Decision Factors in Physical Plant 90 •Network topology •Cost per location •Distance Limitations •Other Limitations (interference) •Bandwidth (data flows, type) TDC 363 Greg Brewster, DePaul University
Ethernet Physical Standards Ethernet 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 standard defined by the IEEE 802.3 committee There is only one layer 2 Ethernet standard, specifying packet header format, access methods, switch operations, that works over any of these different physical networks. TDC 363 Greg Brewster, DePaul University 91
Ethernet Network Cabling Coaxial Cable Widely used in 1980s, but not today Expensive, difficult to manage Twisted Copper Pair Least expensive Limited distance - typically max. 100 meters (330 feet) Susceptible to electromagnetic noise Fiber Optic Cable Most expensive Longest distance –possibly up to 60 miles Highest bandwidth TDC 363 Greg Brewster, DePaul University 92
Network Cabling Coaxial Cable Central copper core surrounded by an insulator Braidinginsulates coaxial cable Sheathis the outer cover of a cable Foundation for Ethernet network in the 1980s TDC 363 Greg Brewster, DePaul University 93
Network Cabling Thinnet (10Base2) Also known as thin Ethernet, was most popular medium for Ethernet LANs in the 1980s TDC 363 Greg Brewster, DePaul University 94
Network Cabling Twisted-Pair (TP) Cable Consists of color-coded pairs of insulated copper wires twisted around each other and encased in plastic coating Twists help reduce effects of
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- Fall '09
- DePaul University, Greg Brewster