Bright talk voip vofi webinar jan2015-v2

www.wildpackets.com © WildPackets, Inc.

VoIP and VoFi

Monitoring and Analysis January 2015

Jay Botelho

Director of Product Management

WildPackets

[email protected]

Follow me @jaybotelho

© WildPackets, Inc. 2

Agenda

• VoIP – Still Top of Mind in Network Performance

Monitoring

• VoIP/VoFi/Video Is Just Different!

• Key Metrics

• Monitoring and Analyzing VoIP/VoFi Issues


VoIP – Still Top of Mind in

Network Performance Monitoring


TRAC NPM Research

Demographics

Early 2014

406 participants

Company type: 70% - Enterprise

28% - Service

Providers

Company size: 41% - Large organizations

38% - Medium

21% - Small

Geography

56% - North America

24% - EMEA

14% - APAC


Key IT Initiatives Impacting

Network Performance

48%

54%

59%

65%

66%

69%

72%

BYOD

Public Cloud services

Video conferencing

Virtual desktops

Enterprise Mobility

Big Data

VoIP


36%

40%

41%

59%

64%

Ability to improve performance for homeoffice users

Managing recreational traffic

Increase in number of IP flows to be managed

Managing bandwidth consumption peruser/subscriber

Managing real-time applications (VoIP, video,etc.)

Key Challenges for

Managing Network Traffic


Key Challenges for

Managing UC Performance

24%

31%

38%

44%

44%

52%

Time spent on extracting session details

Inability to correlate multiple network layers

Visibility into bandwidth utilization

Visibility into the quality of user experience

Visibility into each session for UC technologies

Visibility into the impact of UC deployments onother applications on the network


And It’s Not Just VoIP …

• Percentage of all forms of video (TV, VoD, Internet,

and P2P) will be approximately 90 percent of global

consumer traffic by 2015

• Internet video to TVs will increase 17-fold by 2015

http://www.cisco.com/en/US/solutions/collateral/ns341/n

s525/ns537/ns705/ns827/white_paper_c11-481360.pdf

http://www.cisco.com/en/US/solutions/collateral/ns341/ns525/ns537/ns705/ns827/white_paper_c11-481360.pdf





VoIP/Video Is Just Different!


VoIP/Video Is Just Different!

• Packet delivery not guaranteed

• Small and consistent packet

sizes

• Highly regular packet spacing

• Reliable packet delivery

• Large and variable packet

sizes

• Widely varying packet

spacing

VoIP Data


The Impact of "Just One More Call"

• Although a network link may be able to support a

number of concurrent calls, one additional call is

often enough to cause quality problems …

x1113

x2111

x1112

x1111

1st Call

2nd Call

3rd Call x2112

x2113

Example: The WAN can support 2 simultaneous calls.

What happens when a third call is attempted???


The Impact of "Just One More Call"

• Although a network link may be able to support a

number of concurrent calls, one additional call is

often enough to cause quality problems …

x1113

x2111

x1112

x1111

1st Call

2nd Call

3rd Call x2112

x2113

Example: The WAN can support 2 simultaneous calls.

What happens when a third call is attempted???

Call #3 Causes Poor Quality for ALL Calls


Quantitative Interference Impacts on VoFi

Source: Farpoint Group


Quantitative Interference Impacts on VidFi

Source: Farpoint Group


Packet-by-Packet

VoFi Call

Wired VoIP Call


Key Metrics


Key RTP (VoIP/VoFi/Video) Metrics

CAMP IT Pinpointing the Problem 17

Packet Loss

Jitter Latency


Latency

Queue Latency &

Decision Latency

Network

Propagation

Delay

Encoding / Decoding

Compression / Decompression

Jitter Buffer Latency

0 ms

100 ms

200 ms

300 ms

400 ms

500 ms

600 ms

700 ms

800

ms The ITU

recommends a

maximum one-

way delay of

150 ms for

VoIP


Latency's Effects • Talkover

‒ Occurs when excessive latency delays audio

– Conversation cadence is not natural or comfortable

– Callers feel as if they must “push to talk” or say “over” to control the

conversation

• Echo

‒ The speaker’s voice feeds back into the listener’s microphone

‒ The speaker then hears his own voice returning from the listener’s end,

but delayed due to latency

‒ Most callers find it difficult to maintain normal speech when echo delay

is prolonged

‒ Some VoIP systems attempt to cancel echo, but are not always

successful

High latency may also cause additional troubles such as loss of

synchronization between audio and video for multimedia sessions.


Jitter • Jitter is the variance in packet delivery intervals to the listener

• Jitter buffer adds additional delay to voice reaching the ear piece in

case other packets need to catch up

• Packets delayed too long in the network are not allowed to enter the

jitter buffer

Packets delayed more than the buffer delay

(100 ms as an example) are dropped

. . .. .. . . ........ ......

Packets are buffered and

delayed at the Receiver

The “jitter” buffer releases

a G.711 packet every 20 ms

A G.711 packet sent

every 20 ms

Packet jitter and drops

3 1

2

4


Jitter's Effects

• Jitter causes weird “sound effects” that vary with

jitter severity and environmental factors

• Examples include: ‒ Static

‒ Stuttering or uneven audio – abnormal speech rhythm

‒ For multimedia systems, video may be “jerky” or irregular

• If jitter levels are high, packet loss can result ‒ In some cases, severe jitter may sound similar to packet loss,

even if no packets are actually dropped


Packet Loss

• Packet dropped due to physical layer corruption

• Congestion without adequate QoS provisions

• Jitter buffer discards due to excessive latency


Packet Loss Effects

• Causes missing sounds, syllables, words, or phrases

‒ DSP algorithms may compensate for up to 30 ms of missing data

‒ More than 30 ms of missing audio is noticeable by listeners

• An average person speaks at a rate of about 200 words per

minute

‒ That’s 3.33 words/sec = 300 ms per word

‒ For G.711, we would need to lose 15 consecutive RTP packets to lose

a whole word

‒ Dropping 15 packets/sec for G.711 would be a loss rate of 30%

• But losing only a few packets can still be very noticeable

‒ Loss of more than 2 consecutive packets will be heard

‒ Loss rates ≥ 2% will have a strong impact on quality

‒ Losses of 5 – 10% make calls all but intolerable

‒ Bursty periods of packet loss are worse than more dispersed loss


Measuring Key RTP Metrics


Making Sense of the Metrics

• A single value to reflect the user’s QoE (quality of experience)

• Mean Opinion Score (MOS) – several flavors

‒ Algorithmic simulation of subjective audio assessment

‒ Most commonly used varieties are MOS-LQ (listening quality) and

MOS-CQ (conversational quality)

‒ Possible range of 1 (poor) to 5 (excellent)

‒ Maximum possible MOS = 4.4 with G.711

‒ Typical range in most networks is 3.5 – 4.2

• R-Factor – several flavors

‒ Based on latency, jitter, packet loss, bit rate, and signal-to-noise ratio,

codec effects (for low bit-rate codecs) • The ITU algorithms consider about 20 quality inputs

‒ Possible range of 0 (poor) to 100 (excellent)

‒ Provides LQ, CQ, and other score variants


Measuring MOS and R-Factor


Review of Key RTP Metrics

• Latency

• Jitter

• Packet Loss

• MOS

• R-Factor


Data Impacts on VoIP


Got QoS?

• One of the most potent weapons for fighting VoIP troubles is to provision Quality of Service (QoS)

• QoS enables network devices to prioritize and give preference to packet streams that are sensitive to delay, packet loss, jitter, and other performance inhibitors

• Standards-based QoS methods include: ‒ IP Differentiated Services (DiffServ)

‒ MAC Layer QoS with IEEE 802.1p

‒ VLANs

• QoS may be obtained or supplemented via proprietary means, such as traffic shaping via various flow processing algorithms

• Watch for too much differentiated traffic!


Ready for QoS?

• QoS provisions are based on the “weakest link”

concept ‒ If any device in a data path does not support QoS, then media

streams will not be afforded the preference they require for good

performance

• Pre-deployment assessment must ensure that ALL

devices can recognize and respond to QoS

parameters in packet headers ‒ Switches, routers, firewalls, proxies, and any other devices that

touch RTP packets must be “VoIP-friendly”


Monitoring QoS Configuration


Troubleshooting RTP Issues


VoIP Dashboard View


Calls View


Media View


Call Data Record (CDR)

Provides comprehensive, real-time

statistical and quality report for base-

lining, and 100% visibility into calls


Down To The Details …


Identifying Unauthorized RTP Traffic

• Look for bandwidth hogs

• Use filters and alarms


Q&A

Thank You!

WildPackets, Inc.

1340 Treat Boulevard, Suite 500

Walnut Creek, CA 94597

(925) 937-3200

Bright talk voip vofi webinar jan2015-v2

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