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CECS 474 Computer Network Interoperability
Network Interconnection Devices
Repeaters, Hubs, Bridges, Switches, and Routers
Repeaters and Hubs
A repeater is a network interconnection device that regenerates signals coming in one link onto another. Repeaters use no logic in regenerating signals, so data and noise are both sent through the repeater. Repeaters can be used to extend the range of a single LAN. A hub is a network interconnection device that accepts an input signal from an incoming port and copies it onto all of its output ports.
Physically, hubs are: Small electronic devices Have connections for several computers (e.g., 4 or 20) Logically, hubs: Operate only on signals Propagate each incoming signal to all connections Are similar to connecting segments with repeaters Do not understand packets so it cannot filter them Hubs have extremely low cost.
A bridge (sometimes called a transparent bridges ) is a network interconnection device that forwards data frames coming in from one connection to the outgoing link that corresponds to the MAC destination address in the frame. A bridge : Is a hardware device Connects two LAN segments Forwards frames Does not forward noise or collisions from the incoming connection Learns addresses and filters frames based on those addresses A bridge is used to connect two local-area networks (LANs), or two segments of the same LAN, that are the same type.
A switch is a network interconnection device that accepts a frame from an incoming port and forwards the frames to the outgoing link that corresponds to the MAC destination address in the frame. A switch : Is physically similar to a hub Is logically similar to a bridge o It operates on frames o It understands MAC addresses o It only forwards frames when necessary Permits separate pairs of computers to communicate at the same time Has higher cost than a hub Switches can be used in heavily loaded networks to isolate data flow and improve performance. Switch prices are dropping so that there is very little difference from hub prices.
A router is a network interconnection device that accepts an IP datagram from an incoming port and forwards the datagram to the outgoing link that corresponds to the IP destination address in the frame. 134.139.5. 192.168.10. 192.168.45. 10.34.0.
A router: Forwards data depending on IP addresses , not Hardware (MAC) addresses. Isolates each LAN into a separate subnet, with separate IP addresses. Needs to be set up before they are used. Once set up, they can communicate with other routers and learn the way to parts of a network that are added after a router is initially configured.
