This document discusses voice quality issues in communications systems. It covers various types of voice quality problems like dropped calls, delayed audio, distorted audio, noise, echo, and one-way audio. It then discusses potential root causes like network issues, core performance problems, gateway issues, and device problems. It provides guidance on network considerations like acceptable and optimal values for jitter, packet loss, and latency. It also covers protocols like SIP and SRTP/RTCP. The document includes charts showing bandwidth requirements for different codecs with and without forward error correction. It provides an example scenario for configuring a controlled admission policy for a WAN link. Finally, it lists upcoming training sessions on Communications Server.

3. Voice Quality

6. Voice Quality Issues
Call Reliability Audio Quality
Dropped Failed Broken Delayed Distorted Low One Way
Noise Echo
Calls Calls Up Audio Audio Audio Volume Audio
Network Core Performance Gateways Devices

7. Network Considerations

8. Network Conditions Acceptable Quality Optimal Quality
Interarrival packet jitter (avg) ≤ 10ms ≤ 5ms
Interarrival packet jitter(max) ≤ 80ms ≤ 40ms
Packet loss rate (avg) ≤ 10% ≤ 2%
Network latency RTT ≤ 200ms ≤ 120ms

9. SIP
SRTP / RTCP
1 2 3 4 5
1 2 3 4 5

10. SIP
SRTP / RTCP
1 2 4 5
1 2 4 5
1 2 3 4 5
F
E
C
1 2 2 3 3 4 4 5

12. Codec RTAudio - RTAudio - Siren G.711 G.722 RTVideo - RTVideo - RTVideo -
8Khz 16 Khz CIF 15fps VGA 30fps HD 30fps
Typical
Bandwidth 25.9 kbps 34.8 kbps 22 kbps 59.8 kbps 42.8 kbps 203 kbps 492 kbps 1230 kbps
– No Fec
Upper Limit
– No FEC 39.8 kbps 57 kbps 51.6 kbps 92 kbps 99.6 kbps 250 kbps 600 kbps 1500 kbps
Upper Limit
- FEC 51.6 kbps 86 kbps 67.6 kbps 156 kbps 163.6 kbps n/a n/a n/a
Bandwidth numbers include overhead for framing, encryption, and IP routing information in addition to actual encoded
media and based on 20ms audio p-times
Typical bandwidth values bit rate are measurements of typical activity level values under good network conditions (i.e.
no FEC for audio sessions)
Typical BW number can be used for capacity planning to assess if a network should be considered „right provisioned‟
Average can be used for initial capacity planning where most calls are within enterprise network
Monitor actual Bandwidth usage of UC sessions and then refine

15. Example Scenario
CAC Profile Type WAN Link Per Available Audio WAN Link per Session Available Video
Session Audio Limit Video Limit
Optimized for Session 60 kbps RTAudio NB + FEC 350 kbps RTVideo – CIF (15fps)
Count Siren + FEC RTVideo – Pano (15fps)
(w/ Wide Band P2P) RTAudio WB (no FEC)
Balanced 95 kbps (Above plus) 600 kbps (Above plus)
RTAudio WB + FEC RTVideo – VGA (30fps)
G.711 (no FEC)
G.722 (no FEC)
Optimized for Quality 165 kbps (All Above plus) 1500 kbps (All Above plus)
G.711 + FEC RTVideo – HD (30fps)
G.722 + FEC
WAN Link Policy:
Audio Session Limit = 60 kbps
RT Audio WB (no FEC)
Redmond New Orleans

16. Example Scenario
CAC Profile Type WAN Link Per Available Audio WAN Link per Session Available Video
Session Audio Limit Video Limit
Optimized for Session 60 kbps RTAudio NB + FEC 350 kbps RTVideo – CIF (15fps)
Count Siren + FEC RTVideo – Pano (15fps)
(w/ Wide Band P2P) RTAudio WB (no FEC)
Balanced 95 kbps (Above plus) 600 kbps (Above plus)
RTAudio WB + FEC RTVideo – VGA (30fps)
G.711 (no FEC)
G.722 (no FEC)
Optimized for Quality 165 kbps (All Above plus) 1500 kbps (All Above plus)
G.711 + FEC RTVideo – HD (30fps)
G.722 + FEC
WAN Link Policy:
Audio Session Limit = 60 kbps
RT Audio WB (No FEC)
Internet
Redmond New Orleans

17. Example Scenario
CAC Profile Type WAN Link Per Available Audio WAN Link per Session Available Video
Session Audio Limit Video Limit
Optimized for Session 60 kbps RTAudio NB + FEC 350 kbps RTVideo – CIF (15fps)
Count Siren + FEC RTVideo – Pano (15fps)
(w/ Wide Band P2P) RTAudio WB (no FEC)
Balanced 95 kbps (Above plus) 600 kbps (Above plus)
RTAudio WB + FEC RTVideo – VGA (30fps)
G.711 (no FEC)
G.722 (no FEC)
Optimized for Quality 165 kbps (All Above plus) 1500 kbps (All Above plus)
G.711 + FEC RTVideo – HD (30fps)
G.722 + FEC
WAN Link Policy:
Audio Session Limit = 60 kbps
RT Audio NB (+ FEC)
Internet
Redmond New Orleans

18. 1440x900
1280x800
1680x1050
1920x1200
Screen Size
1 Mbps
512 Kbps
384 Kbps
768 Kbps
Acceptable
2000
5000
1000
3000
4000
0
19:21,1
29:36,1
39:51,1
50:06,1
00:21,1
10:36,1
20:51,1
31:06,1
41:21,1
51:36,1
01:06,0
2 Mbps
Optimal
1.5 Mbps
3.5 Mbps
06:06,1
2.75 Mbps
11:21,1
16:21,1
22:51,1
33:06,1
43:21,1
53:36,1
03:51,1
Kilobits/sec sent by Sharer
14:06,1
24:21,1
34:36,1
44:51,1
55:06,1
05:21,1

19. Media Type Per Hop Queuing and Notes:
Behavior Dropping
Audio EF Priority Queue Low loss, low latency, low jitter, assured bandwidth
Pair with WAN Bandwidth Policies on constrained links
Video AF41 BW Queue + DSCP Class 4. Low drop priority.
WRED Pair with WAN Bandwidth Policies on constrained links
SIP Signaling CS3 BW Queue Class 3.
Bandwidth allocation should be sufficient to avoid drops
App Sharing AF21 BW Queue + DSCP Class 2. Low drop priority.
WRED Pair with End User Policy Caps
File Transfer AF11 BW Queue + DSCP Class 1. Low drop priority.
WRED Pair with End User Policy Caps

24. Core Performance, Devices and
Gateways

25. In Microsoft Communications Server “14” media for calls within a
site can go directly to PSTN Gateway
Improves audio quality and reduces numbers of servers
Today 5pm UNC314 CS “14”: Voice Deployment

26. Thursday 9:45AM - UNC208 CS “14”: What's New in Devices

27. E2E Experiences: Admins

28. Weds 1.30pm - UNC316 - CS “14”: Monitoring and Reporting

29. E2E Experiences: End Users

31. Admin Extensibility

33. Succeed at Voice Quality with Microsoft’s software powered
Unified Communications and redefine what it means to
communicate in your business!

34. Monday 4:30PM UNC320 CS “14”: What's New in Communicator “14” Experience & Backend Amit Gupta
9:45AM UNC311 CS “14”: Architecture Mahendra Sekaran
1:30PM UNC313 CS “14”: Voice Architecture and Planning for High Availability Jamie Stark
Tuesday
3:15PM UNC312 CS “14”: Network Considerations Neil Deason
5:00PM UNC314 CS “14”: Voice Deployment Jamie Stark
8:00AM UNC318 CS “14”: What's New in Conferencing Experience & Backend Cameron & Tim
9:45AM UNC317 CS “14”: Management Experience Anand & Cezar
Wednesday 11:45AM UNC321 CS “14”: Interoperability: Voice, Video, Conferencing, IM, & Presence Francois Doremieux
1:30PM UNC316 CS “14”: Monitoring and Reporting Jared & Neil
5:00PM UNC315 CS “14”: Setup and Deployment Peter Schmatz
Thursday 9:45AM UNC208 CS “14”: What's New in Devices Avi & Sachin

35. TechEd Online
microsoft.com/communicationsserver
Technical Library
NextHop DrRez on Twitter
Communications Server Exchange Server
Partner Link Customer Link
Exchange 2010 SP1 Beta download

36. www.microsoft.com/teched www.microsoft.com/learning
http://microsoft.com/technet http://microsoft.com/msdn

38. Sign up for Tech·Ed 2011 and save $500
starting June 8 – June 31st
http://northamerica.msteched.com/registration
You can also register at the
North America 2011 kiosk located at registration
Join us in Atlanta next year