Cirrus Logic CS485 Instrukcja Użytkownika Pobierz pdf (Strona 61)

CS485G Spring 2015 61

3. An internetwork is an interconnected set of networks; the Internet is

the best example.

4. Lowest level: ethernet segment

(a) Hosts (computers) are connected via wires (CAT-5 twisted pairs,

for instance) to a hub.

(b) Each host has a network interface card (NIC) that connects to

the bus on one side and the wire on the other side.

(d) Each NIC has a unique 48-bit media access control address (MAC

address), represented in a fashion like 00:16:ea:e3:54:e6.

(e) Hosts send information on the lines in chunks called frames.

(f) The hub copies frames from every port to every other port (broad-

casting).

(g) A frame includes a destination NIC (by including its MAC ad-

dress); only the host to which the frame is addressed takes it.

(h) Hubs have mostly been supplanted with switches and routers,

which do not broadcast.

5. A bridge connects internet segments, spanning a building or a cam-

pus.

(a) A bridge is typically a switch.

(b) Switches learn which MAC addresses are reachable on each phys-

ical port and then selectively copy frames only to the correct

port.

6. A router connects multiple LANs together into an internet.

(a) The different LANs might run different protocols, such as Eth-

ernet and Wiﬁ.

(b) The router bases its port decision on a higher-level address ﬁeld,

such as in internet protocol (IP) address and tables.

7. Lecture 35, 4/27/2015

8. Ad-hoc internets have no particular topology, and the routers and

links might have a variety of capacities.

(a) The routers bridge the network, but they may send similar pack-

ets along different routes.

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Cirrus Logic CS485 Instrukcja Użytkownika Strona 61