Presentation

Transcription

Presentation

VoIP Over the Internet: Is Toll Quality
Achievable?
Mansour Karam, Technical Lead
SCV Communications Society
May 12, 2004
© 2004 RouteScience Technologies, Inc.
1
Agenda
•
•
•
•
•
•
Introduction
VoIP versus “VoIP over the Internet”
Challenges for VoIP over the Internet
Technological advances that address today’s challenges
An overview of adaptive networking technology
Case studies
Agenda
2
Introduction: Migration to VoIP is compelling
•
As VoIP vendors will tell you, migration to a converged
voice/data network is compelling for many reasons
– More effective communications
– Reduction in CapEx and OpEx
– Enhanced flexibility and resiliency (in theory)
•
Some pointers
– http://telecomreseller.com/avayaextra/
– http://www.nwfusion.com/columnists/2002/0916taylor.html
– http://www1.avaya.com/enterprise/news/docs/lp/ccs.html?c=SIP&n
=SIP_AvCom_ThoughtLdrship&t=internal
– http://www.cisco.com/warp/public/cc/so/neso/vvda/iptl/msipt_bc.pdf
•
Hence the spotlight on VoIP
Introduction
3
Introduction: VoIP versus VoIP over the Internet
•
•
Today’s VoIP deployments work great over local area networks
•
However, VoIP deployments do not work so well over the Internet,
because:
– Internet is a “best effort” infrastructure…
– Internet infrastructure shared across a large number of competing
Today’s VoIP deployments work reasonably well over dedicated
(expensive) private wide area networks
– Frame relay, ATM, leased lines
applications with widely different characteristics
– Highly demanding applications (such as Voice) experience quality and
availability problems
•
Regardless of WAN fabric, availability is orders of magnitude away
from 99.999% or “5 nines”
Introduction
4
Introduction: adaptive networking
•
Enterprises generally engineer into their network some
level of redundancy
•
•
In particular, more than one path is commonly available
Adaptive networking leverages inherent redundancy,
through:
– Monitoring of available paths
– Assessment of paths according to a set of criteria
– Dynamic route adjustments to steer traffic through the path that
makes the best business sense at any given time
•
Adaptive networking is Air Traffic Control for your WAN
Introduction
5
What is the public Internet?
•
Collection of networks that have little incentive to work
together
Internet
VoIP vs “VoIP on the Internet”
6
What is it like to use the public Internet?
•
•
•
•
•
•
Switches
Routers
Firewalls
VPN gateways
Load balancers
Packet shapers
•
•
•
•
Maintenance windows
Software anomalies
Feature set compatibilities
Technology in constant flex
Internet
VoIP vs “VoIP on the Internet”
7
Data collected between RouteScience POP
locations, June 2001
AND
EWR
SJC
THR
ASH
Source: A. Markopoulou, F. Tobagi, M. Karam, "Assessing the quality of Voice Communications over Internet Backbones", IEEE
Transactions on Networking, October 2003
“VoIP on the Internet” data
8
Delay and loss characteristics
•
Delay
• East coast: 3.25-11.8 ms
• Coast-Colorado: 28.3-77.8 ms
• Coast-to-coast: 31.3-47.2 ms
– Delay variability:
Delay in ms
– Propagation delay:
• Pattern: mainly spikes
• During the day
•
Loss
Time
– Mainly outages – reliability problems
• Happen at least once per day for 6 out of 7 providers
• Usually preceding changes in the propagation delay
9
Converting delay and loss into MOS
Speech
Transmission Quality
(user satisfaction.)
Desirable
Acceptable
Best (very satisfied)
High (satisfied)
Medium (some users
dissatisfied)
Low (many users
dissatisfied)
Poor (nearly all
dissatisfied)
Mean Opinion Score
(MOS)
4.5
4.3
4.0
3.6
3.1
2.6
Not
recommended
1
Reference: ITU-T G.107/Annex B
10
Percentage of calls with MOS ≤ x
Results from joint Stanford/Routescience study
Threshold of
acceptable quality
Availability
97%
Worst MOS for call
MOS at the end
of call
63% of the calls
exhibit a worst
period having
unacceptable
quality
3% of the calls
have unacceptable
quality
11
12% of the calls
exhibit a worst
period having
unacceptable
quality
Percentage of calls with MOS ≤ x
100
Worst MOS for call
MOS at the
end of call
10
2% of the calls
have unacceptable
quality
Threshold of
acceptable quality
1
Availability
1
2
MOS
3
4
98%
12
“… Backbones networks are over-provisioned and thus
expected not to be the bottleneck on the path of a flow.
Although this might be the case for data traffic, this is not
always the case for VoIP traffic. We observed poor VoIP
performance on a large number of ISP backbone networks
under favorable end-system configurations”
Source: A. Markopoulou, F. Tobagi, M. Karam, "Assessing the quality of Voice
Communications over Internet Backbones", IEEE Transactions on Networking, October
2003
13
Bad minutes per month
Enterprise customer case study, January 2003
345
bad minutes
Brownouts: 254 minutes
(74%)
Blackouts: 91 minutes
(26%)
26 bad seconds
Internet:
PSTN norm:
99.2% availability
99.999% availability
14
VoIP over a private network
•
Major VoIP equipment vendors recommend the use of
private networks:
– Owned/leased networks
– Frame Relay
– ATM
Private Networks
15
Frame Relay case study: Online financial
services firm
VoIP over Frame Relay
Headquarters
ISP 1
IP/PBX
IP/PBX
Headquarters
Eastern Data Center
OC-3
OC-3
OC-3
ISP 1
Internet
ISP 2
ISP 2
OC-3
IP/PBX
DS-3
DS-3
Frame Relay DS3
End-to-end measurements collected for 11 days
Private Networks
16
Example performance problems over Frame Relay
and Internet
Delay spike
High packet loss
Link failure
•
Configuration
Bad Minutes
Reliability
(%)
Frame Relay
5.4
99.966
Internet
126.2
99.203
The resulting end-to-end system still does not deliver Toll
Quality voice
Private Networks
17
Cost of private network
•
•
•
Private links are costly
Private link costs increases with distance
Inter-continental private link costs are very high
Private Networks
18
Technological landscape
Technology category
Adaptive networking
Technology function
Sidestep “brownouts”
QoS
Example companies
RouteScience
Router vendors
Scheduling techniques
Packet sequencing
Sitara
Cetacean
Packet shaping
Metering lights
Compression
Stuffing more in a
packet
MPLS
Traffic Engineering
Buffer Management
schemes
Filtering
Packeteer
Peribit
Router vendors
Caspian
Router vendors
Other…
Technological Advances
19
QoS example: DiffServ combined with
sophisticated queue scheduling
•
DiffServ ToS marking allows traffic to be categorized as
Voice or Data.
•
Scheduling gives voice traffic priority access to the
resources using your favorite scheduling technique
Voice
Data traffic
Scheduler
•Priority Queuing
•WRR
20
Challenges of traditional QoS
•
QoS in IP networks largely remains an elusive goal, even
though over-provisioning not economically viable in the
long run
•
QoS challenges:
–
–
–
–
Strict prioritization degrades under load
Architecture scales, but QoS doesn’t
How is provisioning done for various, different QoS requirements
Hard translation from delay, jitter, loss requirements to classes of
service
– Requires cooperation across different ISP backbones
•
All the above challenges impede the actual implementation
21
Challenges of traditional QoS
“(…) The crucial issue is that we are trying to get
deterministic performance for multiple classes of traffic. If the
QoS story were just best effort and one premium class, then
queuing mechanisms of today work (…) With multiple realtime classes—voice, video, machine-to-machine, telemetry
and others—you will degrade back to best effort.
It’s just too much to do the packet-by-packet
routing and the queuing calculations and figure out where
and in which queue to stick each packet. Forget it! It’s too
complicated (…)”
Peter Sevcik, Business Communications Review, September 2003
22
Alternative: packet sequencing
•
In effect, circuit switching, wherein different types of circuits
can be created
•
How does it work?
– Creates itineraries for various flows admitted to the network
– Insures that the collection of itineraries meet a given schedule
– A schedule is a collection of appointments, wherein an appointment
consists of the deadline by which a packet of a given size is to be
processed by a switch
– Relies on admission control: Call only accepted if an itinerary that
satisfies each router’s schedule is found
23
Packet sequencing
•
Performance credentials
– Sub 2-second call setup times
– Has been tested to provide 99.999% (5 nines) in the lab
•
Challenges:
– For technique to be effective, requires all network
elements in the path to be capable of packet
sequencing
– Very expensive to deploy
– Difficult to scale
24
Applications succeed only when ALL of the
infrastructure works
Data Centers
•
Business objectives are dynamic
– New applications, new partners, new policies
•
Applications, and users, are getting more demanding
– VoIP, video conferencing
•
Applications are being stretched over longer distances
•
The wide area network is the key point of vulnerability
– How do you avoid problems in fabric you don’t own?
•
“Brownouts” are sudden, and require instant response
– How do you spot a brownout?
Network
Infrastructure
Users
Adaptive networking
25
Virtualized infrastructure
•
Like the servers and the storage devices, the key is
– Virtualization
– Redundancy with intelligent “oversight”
•
Redundancy should also apply in the WAN:
– Multiple paths
– A combination of private and public links, architected as appropriate
•
Define policy for availability requirements
– Manage the performance – cost tradeoff
– Monitor / assess / adjust / notify
Adaptive networking
26
The key to adaptive networking
Good/Bad
Quality Metric
•
“Bad” means an application quality
problem caused by the network
•
Application Delay
Transport Delay
Raw Latency, Loss, Jitter, etc
•
•
“Star ratings” comparable
across apps
•
Delay for a typical app
transaction
•
Transport layer impact of
low level scores
•
Low level measures
Individual network-level metrics do not determine absolute quality
What is “good” for one application type may be “bad” for another
Adaptive networking
27
Closing the loop with automated repair
Application Quality
Metrics
•
•
•
•
Application needs
User location
User importance
WAN status
RouteScience
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•
Assess alternate paths
•
•
•
React quickly
Actively control network to:
– Sidestep brownouts
– Increase app performance
– Reduce costs
Maintain stability
Validate effectiveness
Adaptive networking
28
Managing the application through the fabric
29
What adaptive networking can do for VoIP
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•
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Add a 9 to VoIP availability
Eliminate 90% or more of bad minutes
Eliminate network upgrades
Provide WAN visibility
Improve quality of 1-800 services to India
30
MOS
Case study: ISP problem during business hours
Threshold of acceptable VoIP quality
7pm
•
•
•
Midnight
5am
10am
3pm
EST
All ISPs suffer unpredictable performance problems
No single ISP can deliver sufficient quality for VoIP,
24x7x365
On Net is not always best
Case study
31
MOS
Adaptive networking delivers sustainable voice
quality
7pm
Midnight
5am
10am
3pm
EST
7pm
Midnight
5am
10am
3pm
EST
MOS
Improvement
7pm
Midnight
5am
10am
3pm
Case study
EST
32
Case study: Online financial services firm
Eastern Data Center
Headquarters
ISP 1
OC-3
OC-3
OC-3
IP/PBX
IP/PBX
Headquarters
ISP 1
Internet
ISP 2
ISP 2
OC-3
IP/PBX
DS-3
DS-3
Frame Relay DS3
End-to-end measurements collected for 11 days
Case study
33
Sample hour
Adaptive networking-induced route
changes:
• From green to cyan
• From cyan back to green
Link failure
Packet loss
Performance problem
Quality threshold
5 bad minutes for default routing
0.2 bad seconds for Optimized
path
Case study
34
Example of delay spike
RTT (ms)
Delay spike
Time (hour of day)
35
RTT (ms)
Example of delay fluctuations
Adaptive
networking induced route
change from
green to cyan
Adaptive
networking induced route
change from
cyan back to
green
Time (hour of day)
36
Impact on VoIP availability
Frame
Relay
•
•
•
•
Internet
RS optimized
Internet
Configuration
Bad Minutes
Reliability (%)
Frame Relay
5.4
99.966
Internet
126.2
99.203
Optimized
Internet
14.7
99.907
Optimized path
over Internet +
Frame Relay
0.4
99.997
RS over Internet
+ Frame Relay
Study comparing suitability of private, public and hybrid
options
Sidestep brownouts on “in-flight” calls
Deliver a 10-fold increase in availability
Reduce bad minutes up to 90%
Case study
37
General observations
•
All networks have quality failures
–
–
–
–
–
–
Delay spikes
Packet loss
Link failures
Delay fluctuations
Large jitter due to layer-2 round-robin
Congestion effects due to worms
Case study
38
General observations
•
•
•
Problems rarely occur in all networks at once
•
Adaptive networking effectively avoids performance
problems by implementing route changes
Bandwidth is clearly not the problem
Performance problems result in multi-minute application
outages affecting, for minutes, inter-PBX calls
Case study
39
Conclusion
VoIP availability
99.999%
Toll quality
99.99%
99.9%
Availability
gap
Adaptive networking
Underlying network
99%
90%
2001
•
2003
2005
2007
Adaptive networking fills the availability gap, allowing Toll
Quality VoIP over the Internet to become a reality now
Conclusion
40

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