INF3190 – Data Communication University of Oslo
INF3190 - Data Communication
Summary (part 2)
Carsten Griwodz Email: [email protected]
INF3190 – Data Communication University of Oslo
§ Recap protocol terminology − several OSI terms are not
introduced by Tanenbaum
§ Remember the functions of the OSI model − very brief in the book − but terminology persists and is
used in unexpected contexts
Basics
INF3190 – Data Communication University of Oslo
Baseband transmission schemes (very brief in Tanenbaum pp. 145) § presented − binary encoding /
NRZ (non-return-to-zero) − NRZI − Manchester − Differential Manchester
Passband transmission (Tanenbaum pp. 110) § approximating digital signals § definition of bandwidth and wavelength § bits vs. bauds
− amplitude, frequency, phase
§ bitrate of a perfect channel (Nyquist’s theorem) § capacity of a noisy channel (Shannon’s theorem)
− reasons for noise
Physical layer
0!
Am
plitu
de (V
)!
f! 3f! 5f!
INF3190 – Data Communication University of Oslo
Framing (Tanenbaum pp. 217) § What are the options? Error correcting codes (Tanenbaum pp. 224) § Hamming distance § CRC
− generator polynomial − modulo-2-arithmetic: subtraction = XOR
Flow control (Tanenbaum pp. 235) § Protocol examples
− stop-and-wait, go-back-n, selective repeat
§ Sequence number ranges § Maximum link utilization
(very brief in Tanenbaum)
Data Link Layer
INF3190 – Data Communication University of Oslo
DNS (Tanenbaum pp. 629) § recursive and iterative queries § not in Tanenbaum
− caching − aliasing − zoning and load balancing
HTTP (Tanenbaum pp. 664) Email / SMTP (Tanenbaum pp. 641)
Application layer
www.google.com
mpg.ndlab.net
records.sigmm.org
drammen.ndlab.net
simula080.simula.no
INF3190 – Data Communication University of Oslo
Multimedia (not in Tanenbaum) § classes and characteristics of continuous media § UDP or TCP? § basic challenges
− delay, loss, jitter − jitter compensation − loss compensation
RTP (Tanenbaum pp. 564) § wrong section! not a transport protocol! § relation between RTP and Application
layer framing / Integrated layer processing § role of RTCP § mixers and translators (not in Tanenbaum)
Application layer
packets
time
packetsgenerated
packetsreceived
loss
rp p'
playout schedulep - r
playout schedulep' - r
INF3190 – Data Communication University of Oslo
Signaling protocols § RTSP (briefly mentioned in Tanenbaum p.733) § SIP (Tanenbaum pp.749)
− proxy mode and redirect mode
Quality adaptation (not in Tanenbaum) § Loss-Delay Adjustment Algorithm § Blurriness, noise and motion flicker
HTTP Adaptive Streaming (not in Tanenbaum) § comparison to RTP streaming § handling of bandwidth fluctuations
Application layer
INF3190 – Data Communication University of Oslo
Content Delivery Networks (Tanenbaum pp. 761) Modeling popularity (not in Tanenbaum) § use and misuse of
the Zipf distribution
Peer-to-peer networks (briefly discussed in Tanenbaum pp. 766) § Distributed Hash Tables
(DHT) § Chord – where most things
are O(log(n))
Application layer
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Files ordered by daily popularity
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ss fre
quen
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Actual popularity
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1 10 1000 100 1
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All files in system
Tim
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Actual number of hits
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