why should i listen?
DESCRIPTION
Why Should I Listen?. Session Title: QoS & Network Management for Successful Enterprise VoIP Deployment. In other words: How do I roll out VoIP with assurances over network quality while containing network costs?. Raymond Russell, CTO, Corvil [email protected]. - PowerPoint PPT PresentationTRANSCRIPT
Why Should I Listen?
Session Title:
QoS & Network Management for
Successful Enterprise VoIP
Deployment
In other words:
How do I roll out VoIP with
assurances over network quality while containing network costs?
Raymond Russell, CTO, [email protected]
What’s The Business Imperative? VoIP rollouts promise a rich
user experience with substantial OpEx savings
But: If WAN bandwidth costs are
too high, network savings will not materialize
If WAN bandwidth is not sufficient, network quality & user experience will be poor
CIOs need a deterministic way to control both network quality and network costs for VoIP….
BEFORE committing to rollout
Corporate Headquarters
VoIP Users
Service Provider
WAN
What Quality? - how can I be assured about
network performance?
How Much Bandwidth? – how do I know if I’m over-spending for no return in quality?
Problem is Lack of Knowledge, Not Bandwidth
Bandwidth wrongly blamed for latency problems in Network Infrastructure
For decades LAN and WAN network design has focused on providing appropriate bandwidth, and has addressed performance problems by adding more. Network managers must now adopt new procedures and tools to correctly diagnose network performance problems.
Businesses that do not consider latency issues when deploying new global applications across the WAN — or IP voice on the LAN or WAN — will face poor performance, reduced reliability, disgruntled users and, potentially, the failure of major projects for application deployment.
Where the problem is incorrectly diagnosed as too little bandwidth, it will be discovered that adding more bandwidth won't resolve the issue, and misdirected expenditures will never be recovered.
Enterprise Networking Predictions for 2005
Adequate bandwidth is essential for application performance
The tighter the QoS target, the more bandwidth may be required, and vice versa
Depends on how well the traffic multiplexes
QoS, Bandwidth and Traffic (QBT) for the network are inter-dependent
Full control requires an integrated approach to QBT
You need to know your Bandwidth Requirement as it relates to your QoS objectives for your different traffic
IP Network Traffic over Time
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Too Much Bandwidth:Unacceptable OpEx Costs
Too Little Bandwidth:Unacceptable Quality
Key is Understanding QoS, Bandwidth & Traffic as One
?What is my Bandwidth Requirement to meet
my QoS objective
Let’s Get Technical
In IP networks, QoS is determined by three basic criteria: End-to-end delay Hop-by-hop delay variation (jitter) Packet loss
The primary cause of jitter and packet loss is the behaviour and performance of router packet buffers
Packet Delay, Loss & Jitter in Router Buffers
5 4 3 2 16
No room!!!
Router queue
Output link
Queuing causes Delay and Jitter
Full queues cause Packet
Loss
Human beings are highly sensitive to excessive delay
Echo cancellation systems are highly sensitive to jitter
Most codecs are highly sensitive to packet loss
Real-Time Traffic Bursts
Application traffic is bursty at short timescales
• These bursts cause instantaneous queue build-up
• Queue build-ups can take tens and hundreds of milliseconds to clear causing degradation in user-perceived quality
The feature of traffic on which application quality depends is totally invisible to mean-rate measurement
• It is not possible to manage what you cannot control, and you cannot control what you cannot measure
Time
Mean Traffic Rate E.g., 300 Kbps over a 5-minute period
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What you see today
Buffer Behaviour Is A Millisecond Phenomenon
Peter DruckerManagement Guru
Setting QoS Thresholds to meet Service Level Objectives
Different Applications can tolerate different levels of packet loss and delay, which are expressed as statistical limits
e.g. VoIP => .1% packet loss and 10ms delay for 99.9% of packets
These are referred to as Service Level Objectives (SLO)
SLOs may or may not form the basis of a legal contract, but if they are not met the application will not operate correctly
Current technologies do not help the network manager to meet these targets for application traffic
.05-
.1%25-50ms
0.1%
Application Dependent,150ms(50ms)
Interactive
.05-
.1%100-500ms
0.1%
Application Dependent.Typically < 1000ms
Transactional
.5-1%15-30ms
1% 150ms(30ms)
Interactive Video
.05-
.1%10-40ms
0.1% <150ms(20-40ms)
Voice
Per-hop Loss
Per-hop
Delay
End-to-end Loss
End-to-EndDelay
(J itter)Class
.05-
.1%25-50ms
0.1%
Application Dependent,150ms(50ms)
Interactive
.05-
.1%100-500ms
0.1%
Application Dependent.Typically < 1000ms
Transactional
.5-1%15-30ms
1% 150ms(30ms)
Interactive Video
.05-
.1%10-40ms
0.1% <150ms(20-40ms)
Voice
Per-hop Loss
Per-hop
Delay
End-to-end Loss
End-to-EndDelay
(J itter)Class
How Does It Work? Allows the user to specify
the maximum loss and delay limits for any traffic and input these on the router
Measures the key statistical properties of real-time traffic at the millisecond level
Reports the minimum bandwidth required (in bits/sec) to meet the quality targets
Basis for Network Dimensioning, Monitoring, Troubleshooting, QoS Optimization, Capacity Planning, Just-in-Time Bandwidth Provisioning, New Application Roll-outs, Service Provider Policing
Time
Too MuchBandwidth
What you need to know:CORVIL BANDWIDTH (CB)
E.g., the CB is 460 Kbpsfor this application to achieve no more than
250ms delay & 0.1% loss
Too LittleBandwidth
Mean Traffic Rate E.g., 300 Kbps over a 5-minute period
Real-Time Traffic BurstsBan
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What you see today
New Approach to Efficient Control of IP QoS
Case Study: Enterprise VoIP Corvil “what-if” capability was used to
determine the impact of VoIP on the existing network prior to deployment
5 simultaneous VoIP calls with Silence Suppression were added to current traffic with a delay target of 40ms
The network manager quickly established the Corvil Bandwidth as 3.9Mbps
Next he ran a “what-if” scenario on Corvil to determine the bandwidth saving from turning on QoS in the router
He quickly discovered that by placing Voice in the priority queue and all other traffic in the best-effort queue, the overall bandwidth requirement could be reduced to 2.37Mbps
Corvil “What-If” After Adding VoIP (No QoS on Router)
Corvil “What-If” After Putting Voice Traffic in Priority Queue
Who is Corvil? Software & hardware company based in
Dublin, Ireland with sales offices in New York & London
Founded in 2000, now at 75 employees
Patents based on core mathematics expertise – key insight: “measure directly the entropy of packet traffic”
Cisco Systems is an investor & partner
World Economic Forum ‘Technology Pioneer 2004’ – “technology with the potential to have a substantial long-term impact on business and society in the future”
For more information visit www.corvil.com