CPSC614:Graduate Computer Architecture Network 1: Definitions, Metrics Prof. Lawrence Rauchwerger. Based on lectures of Prof. David A. Patterson UC Berkeley. System. server. Queue. Proc. IOC. Device. Review: A Little Queuing Theory.
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Based on lectures of
Prof. David A. Patterson
DeviceReview: A Little Queuing Theory
r average number of arriving customers/secondTser average time to service a customer (tradtionally µ = 1/ Tser)u server utilization (0..1): u = r x Tser Tq average time/customer in queue Tsys average time/customer in system: Tsys = Tq + TserLq average length of queue: Lq = r x Tq Lsys average length of system : Lsys = r x Tsys
0: Please send data from Address
1: Packet contains data corresponding to request
00: Request—Please send data from Address
01: Reply—Packet contains data corresponding to request
10: Acknowledge request
11: Acknowledge reply
1: Application copies data to OS buffer
2: OS calculates checksum, starts timer
3: OS sends data to network interface HW and says start
3: OS copies data from network interface HW to OS buffer
2: OS calculates checksum, if matches send ACK; if not, deletes message (sender resends when timer expires)
1: If OK, OS copies data to user address space and signals application to continue
(size ÷ bandwidth)Universal Performance Metrics
(size ÷ bandwidth)
Total Latency = Sender Overhead + Time of Flight+
Message Size ÷ BW +Receiver Overhead
Includes header/trailer in BW calculation?
Copper, 1mm think, twisted to avoid
attenna effect (telephone)
"Cat 5" is 4 twisted pairs in bundle
Used by cable companies: high BW, good noise immunity
Braided outer conductor
Light: 3 parts are cable, light source, light detector.
Note fiber is unidirectional; need 2 for full duplex
– Laser Diode
(A. K. A. data switching
interface message processors)