Transcript Chapter 6 High Speed LANs

High Speed Networks and
Internets: Multimedia Transportation
and Quality of Service
Meejeong Lee
Objectives

What is required to transport
– Large volumes of traffic
– With different QoS requirements
– Over networks operating at very high
data rates
The Need for Speed and QoS
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Emergence of high-speed LANs
– Explosive growth of processing power of
personal computers
– Network computing
– Examples of requirements that calls for HSL
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Centralized server farms
Power workgroups
High-speed local backbone
– Examples of HSL: Fast Ethernet, Gigabit
Ethernet, High speed wireless LAN, ATM LAN
The Need for Speed and QoS
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Corporate Wide Area Networking
needs
– Intranet computing among dispersed
employees
– Internet access with graphical interfaces
– Huge volumes of data with unpredictable
traffic patterns
The Need for Speed and QoS
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Digital electronics
– Digital Video Disk (DVD)
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Huge storage capacity and vivid quality
PC games and educational software with more video
New crest of traffic over the Internet and intranets as
the material is incorporated into web sites
– Digital still camera
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Convenience for use in networks
Dramatic growth in the amount of on-line image and
video traffic
The Need for Speed and QoS

QoS on the Internet
– Internet and IP were designed to provide
best-effort delivery service
– With tremendous increase in traffic
volume, and the introduction of new
real-time, multimedia, and multicasting
application, the traditional Internet
services are woefully inadequately
The Need for Speed and QoS

QoS requirements of Internet applications
– Elastic traffic

Email, file transfer, network management, interactive
applications(rlogin, web access)
– Inelastic traffic
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Voice and video
Throughput, delay, delay variance, packet loss
– Figure 0
Figure 0. A Comparison of Application Delay Sensitivity
and Criticality in an Enterprise [ CROL00]
QoS in IP Networks

Design requirements
– Control congestion
– Provide low delay
– Provide high throughput
– Support QoS
– Provide fair service
QoS in IP Networks
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Two complementary architectures
– Integrated services
– Differentiated services
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Protocols for QoS support
– RSVP: support the IS architecture by enabling
the reservation of resources in a datagram
environment
– MPLS: framework for labeling traffic and routing
based on traffic flows
– RTP: transport level support for real-time
application
Integrated Services
Architecture (ISA)

Tools for controlling congestion in IPbased internet
– Routing algorithm
– Packet discard
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ISA approaches
– Admission control
– Routing algorithm
– Queueing discipline
– Discard policy
Integrated Services
Architecture (ISA)
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ISA components
– Background functions
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Reservation protocol
Admission control
Management agent
Routing protocol
– Main task: forwarding of packets
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Classifier and route selection
Packet scheduler
– Figure1
Figure 1. Integrated Services Architecture Implemented in Router
Integrated Services
Architecture (ISA)
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ISA services
– Guaranteed
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Assured capacity level or data rate
Specified upper bound on the queueing delay through
the network
No queueing losses
– Controlled load
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Approximates the behavior with the best-effort
service under unloaded conditions
No specified upper bound on the queueing delay, but
supposed to impose almost no queueing delay
Almost no queueing loss
– Best effort
Integrated Services
Architecture (ISA)

Traffic description: Tspec
Figure 2. Token Bucket Scheme
Integrated Services
Architecture (ISA)
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Queueing discipline
– FIFO
 No special treatment for higher priority or
delay sensitivity
 Inefficiency when smaller packets are
queued behind a long packet
 Greediness is not punished
– Figure 3
Figure 3. FIFO and Fair Queuing
Integrated Services
Architecture (ISA)

Queueing discipline
– Fair Queueing
– Processor Sharing
– Bit-Round Fair Queueing
– Generalized Processor Sharing
– Weighted Fair Queueing
Integrated Services
Architecture (ISA)
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Discard policy
– Random Early Detection (RED) design
goals
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Congestion avoidance
Global synchronization avoidance
Avoidance of bias against bursty traffic
Integrated Services
Architecture (ISA)
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RED algorithm (Figure 4)
if avg < THmin
queue packet
else if Thmin <= avg <THmax
Calculate probability Pa
with probability Pa
discard packet
else with probability 1-Pa
queue packet
else if avg >= THmax
discard packet
Figure 4. RED Buffer
Differentiated Services (DS)
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DS configuration and operation:
Figure 5. DS Domains
Differentiated Services (DS)
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Per-Hop Behavior (PHB)
– Expedited Forwarding PHB: appears to
the end points as a point-to-point
connection or leased line
– Assured Forwarding PHB: a service
superior to best-effort