ATM (Automated teller machine)

ATM 7/19/2010 1 Fast Relay Networks ④ Relaying traffic as quickly as possible Fast Relay Frame Relay (Variable size PDUs – frames) Cell Relay (Fixed size PDUs – cells) PVC SVC (LAPD) (Q.931) ATM based (For B-ISDN) 802.6 based (For SMDS) PVC SVC (Q.2931) 7/19/2010 2 Transfer Mode ④ Transfer mode ④ Specific way of transmitting and switching through the network ④ Synchronous Mode ④ Synchronous systems negotiate the connection at the data-link level before communication begins. Basic synchronous systems will synchronize two clocks before transmission. ④ Asynchronous mode ④ 7/19/2010 Asynchronous systems do not send separate information to indicate the encoding or clocking information. The receiver must decide the clocking of the signal on it`s own. This means that the receiver must decide where to look in the signal stream to find ones and zeroes, and decide for itself where each individual bit stops and starts. 3 Switching technologies ④ Circuit Switching ④ circuit is established for the complete duration ④ based on TDM (Time Division Multiplexing) ④ also referred to as STM (Synchronous Transfer Mode) ④ very inflexible, since once the duration of time slot is determined, the relative ④ bit rate is fixed ④ Packet Switching ④ user information is encapsulated in packets ④ packets contain additional information used inside the network for routing, ④ error correction, flow control, etc ④ packets have variable length and hence require complex buffer management ④ inside of the network ④ Frame relaying ④ eliminates as much as possible of the overhead of packet switched networks ④ no hop-by-hop flow control and error control ④ can be viewed as streamlined version of X.25 7/19/2010 4 Switching technologies (cont.) Circuit switching Direct connection Copper, wireless No such thing Very fast Message switching Store & forward Copper, wireless Variable, large to small Slow Packet switching Hold & forward Copper, wireless, optical Variable, large to small Fast Frame Relay (switching) Hold & forward Copper, wireless, optical Variable, large to small Faster Cell Relay (switching) Hold & forward Copper, wireless, optical Fixed, very small Very fast 7/19/2010 5 ... - tailieumienphi.vn