1 ram dantu university of north texas, practical networking
DESCRIPTION
3 PerformanceTRANSCRIPT
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Agenda Nuts and Bolts of Internet Access, Edge, and Core Networks LAN Design End-user Protocols, Services and QoS Edge and Core Networks Performance
Bandwidth and Delay Security
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Performance
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Different Types of Links
Sometimes you install your own!Category 5 twisted pair 10-100Mbps, 100m50-ohm coax (ThinNet) 10-100Mbps, 200m75-ohm coax (ThickNet) 10-100Mbps, 500mMultimode fiber 100Mbps, 2kmSingle-mode fiber 100-2400Mbps, 40km
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Bigger Pipes!
Sometimes leased from the phone company
STS: Synchronous Transport Signal
Service to ask for Bandwidth you getISDN 64 KbpsT1 1.544 MbpsT3 44.736 MbpsSTS-1 51.840 MbpsSTS-3 155.250 MbpsSTS-12 622.080 MbpsSTS-24 1.244160 GbpsSTS-48 2.488320 Gbps
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Delay in packet-switched networkspackets experience delay
on end-to-end path four sources of delay at
each hop
nodal processing: check bit errors determine output link
queueing time waiting at output
link for transmission depends on congestion
level of router
A
B
propagationtransmission
nodalprocessing queueing
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Delay in packet-switched networksTransmission delay: R=link bandwidth (bps) L=packet length (bits) time to send bits into
link = L/R
Propagation delay: d = length of physical
link s = propagation speed in
medium (~2x108 m/sec) propagation delay = d/s
A
B
propagationtransmission
nodalprocessing queueing
Note: s and R are very different quantitites!
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Bandwidth (throughput) Amount of data that can be transmitted per time unit Example: 10Mbps link versus end-to-end Notation
KB = 210 bytes Mbps = 106 bits per second
Performance
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Latency (delay) Time it takes to send message from
point A to point B Example: 24 milliseconds (ms) Sometimes interested in in round-trip
time (RTT) Components of latency
Latency = Propagation + Transmit + Queue + Proc.Propagation = Distance / SpeedOfLightTransmit = Size / Bandwidth
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Relative importance of bandwidth and latency small message (e.g., 1 byte): 1ms vs. 100ms
dominates 1Mbps vs. 100Mbps large message (e.g., 25 MB): 1Mbps vs.
100Mbps dominates 1ms vs. 100ms
Consider two channels of 1Mbps and 100 Mbps respectively. For a 1 byte message, the available bandwidth is relatively insignificant given a RTT of 1 ms. The transmit delay for each channel is 8 s and 0.08 s, respectively.
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Delay x Bandwidth Product
e.g., 100ms RTT and 45Mbps Bandwidth = 560KB of data
We have to view the network as a buffer. This may have interesting consequences: How much data did the sender transmit
before a response can be received?
Bandwidth
Delay
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Example: Hospital Network
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W
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Intensive Care Unit
Operating Room
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R
S
Q
O N M
FG
Out-patient RIS
Floors
HIS
PACS Network
INTERNET
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HospitalDistribution
PACS B
C
D
E
H
IJK
L
X
PACS Network and Remote Connectivity