Maximum length of the connection between an adapter and the hub is 100 meters. The maximum length between any two nodes is 200 meters
Bit arrival from one interface, transmit onto all the other interfaces. Net management, detect and disconnect the malfunctioning adaptor. Gather information and report the info to a host that connects directly to the hub.
Provides a degree of graceful degradation. If any one of the departmental hubs starts to malfunction, the backbone hub can detect the problem and disconnect the departmental hub from the LAN. And the remaining departments can continue to operate and communication while the faulty departmental hub gets repaired.
Filtering is the ability of a switch to determine whether a frame should be forwarded to some interface or should just be dropped. Forwarding is the ability to determine the interface to which a frame shouldd be directed, and then directing the frame to those interfaces. Switch filtering and forwarding are done with a Switch table.
Suppose that each connection in the network uses two pairs of twisted-pair cooper wire, one pair for transmitting from host to switch, and the other pair for transmitting from switch to host. Because of the dedicated access, when Host A transmits a frame on its upstream wire pair, there is no possibility that the frame will collide with a transmission from some other host or from the switch. Switches “store and forward”, the switch will transmit at most one frame at a time onto any one of the downstream wire pairs. In fact each link becomes a point-to-point link, obviating the need for a medium-access protocol.
To support for multitude of physical media types and transmission rates, switch manufacturers often tout that their switches use cut-through switching rather than store-and forward packet switching, used by router. Switch has input port and output port. When there are packets queued at the output ports, no difference. When the output buffer is empty, the switch can start to transmit the front of the packet while the back of the packet continues to arrive, rather than gather the entire packet before transmit the whole packet. 1) In a network, latency, a synonym for delay , is an expression of how much time it takes for a packet of data to get from one designated point to another. In some usages (for example, AT&T), latency is measured by sending a packet that is returned to the sender and the round-trip time is considered the latency.
CSMA collisions collisions can still occur: propagation delay means two nodes may not hear each other’s transmission collision: entire packet transmission time wasted spatial layout of nodes note: role of distance & propagation delay in determining collision probability
used to get datagram from one interface to another physically-connected interface (same network)
48 bit MAC address (for most LANs) burned in the adapter ROM
LAN Addresses and ARP Each adapter on LAN has unique LAN address Broadcast address = FF-FF-FF-FF-FF-FF = adapter 1A-2F-BB-76-09-AD 58-23-D7-FA-20-B0 0C-C4-11-6F-E3-98 71-65-F7-2B-08-53 LAN (wired or wireless)