Transcript LAN/WAN and Router Basics

Demystifying Quality of Service
(QoS)
What Is Quality of Service?
 Ability of a network to provide improved
service to selected network traffic over
various underlying technologies
 Provides improved and more predictable
network service by:
•Supporting dedicated bandwidth
•Improving loss characteristics
•Avoiding and managing network congestion
•Shaping and policing network traffic
•Setting traffic priorities across the network
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Introduction to QoS
 Where the data traffic (LAN or WAN) on a
network is subject to scrutiny and control
 Primarily an IP/Layer 3 concept
 Relevant at Layer 2 within the Ethernet environment
and also within the WAN technologies such as
Frame Relay and ATM
 Driving factors: growth of multimedia traffic
(voice and video) and traditional data traffic
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Reasons for QoS
 The introduction of real-time delay sensitive
applications such as VoIP and video over the
Wide Area Network (WAN)
 Shortage of bandwidth because network links
are oversubscribed
 Packets being lost due to congestion during
“bursty” periods
 End-to-end delay made up by a number of
factors
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Why the Need for QoS?
 WAN access is a pinch-point in the network
 100Mbps: 1Mbps speed difference is typical
 Lack of QoS results in unacceptable delay, jitter, loss
 Protect your reputation
 QoS reduces call-backs due to poor voice quality
 VoIP users expect toll-quality phone service
 Poor performance = service calls, lost customers
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Functions of QoS
 QoS needs to enable:
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Predictable response times
Management of delay sensitive applications
Management of jitter sensitive applications
Control of packet loss when congestion occurs
during a burst
Setting of traffic priorities
Dedication of bandwidth on a per application basis
Avoidance of congestion
The management of congestion when it occurs
Need for QoS Support
 Surging data applications can block voice calls
 Delays of less than 1/6-second can impact call
quality
 Varying delay (jitter) degrades quality even with no
loss
Typical network without a QoS solution
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Affect of QoS Prioritization
 Used to prioritize Voice over IP traffic
 Email and data traffic share remaining traffic
Typical network with a QoS solution
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Clear the Traffic Jam in Your Network
No QoS:
Critical traffic excessively delayed
With QoS:
Critical traffic gets “Express Lane”
Multi-lane prioritization for options
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The BIG “Gotcha” with QoS!!
 What is in the “Cloud?”
 Local access types
 T1 leased lines? Point-to-point or to a service providers
data network?
 Cable local loops? Local cable segment congestion?
 Service provider network?
 Can THEY support QoS?
 Service Level Agreement (SLA) support
 The Big “I” Internet?
 Inherently does not support QoS end-to-end
 QoS is only as reliable as the weakest
element in a network!
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Thank You!
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