Contributed from microsoft resource

Lync Bandwidth Requirements

The bandwidth requirements for Lync are difficult to determine for a given customer installation especially since the nature of Lync is to change how people communicate. The starting point for understanding the network bandwidth requirements are documented on Technet and Microsoft have released a bandwidth calculator.
The bandwidth usage is determined by a number of factors, the Codec used (along with overhead), the Stream activity level and for video, the resolution/quality and frame rate.

Audio Codec Bandwidth

Audio codec
Scenarios
Audio payload bitrate
Add IP header only
Also add UDP, RTP and SRTP
Also add FEC
RTAudio Wideband
Peer-to-peer
29.0
45.0
57.0
86.0
RTAudio Narrowband
Peer-to-peer, PSTN
11.8
27.8
39.8
51.6
G.722
Conferencing
64.0
80.0
95.6
159.6
G.711
PSTN
64.0
80.0
92.0
156.0
Siren
Conferencing
16.0
32.0
47.6
63.6

The bandwidth rates are in Kbps (as are all bandwidth rates in this post) and assume 100% stream activity, which is not the normal case. (Note: The online Technet document shows KBPS (i.e. Kilo Bytes per second for the base Audio payload bitrate, it should be Kbps – reference Wikipedia)

Video Resolution Bandwidth

Video codec
Resolution
Maximum video payload bitrate
Minimum video payload bitrate
RTVideo
Main Video CIF
250
50
RTVideo
Main Video VGA
600
350
RTVideo
Main Video HD
1500
800
RTVideo
Panoramic Video
350
50

The maximum bitrate values shown (Kbps) are applicable for maximum frame rate and maximum quality. The minimum bitrate is for 1fps. HD Video is only available for peer-to-peer sessions. By default, only SD video is allowed, to allow HD video at Global or Site level use Set-CsMediaConfiguration –Identity:Global -MaxVideoRateAllowed HD720p15m

Bandwidth usage by participant

The raw bandwidth specified above is used only when the situation requires it, in other words, depending on what individual users are doing with the session determines their bandwidth requirements.

Peer-to-Peer

·Endpoints send audio streams only when the users speak.

·Both participants receive audio streams.

·If video is used, both endpoints send and receive video streams during the entire call.

Conference

·Endpoints send audio streams only when the users speak.

·All participants receive audio streams.

·If video is used, only two endpoints send a video stream at a time (the active speaker and the previous active speaker).

·If video is used, all participants receive video streams.

Stream Activity Levels

Scenario
Media
Estimated stream activity (%)
Peer-to-peer sessions
Audio
61
Peer-to-peer sessions
Main video CIF
84
Peer-to-peer sessions
Main video VGA
83
Peer-to-peer sessions
Main video HD
80
Peer-to-peer sessions
Panoramic video
74
Conferencing
Audio
43
Conferencing
Main video CIF
84
Conferencing
Main video VGA
83
Conferencing
Main video HD
80
Conferencing
Panoramic video
74
PSTN
Audio
65

This is based on customer data gathered by Microsoft.
Added to the media bandwidth requirements is the requirement for control traffic in the form of Real Time Control Protocol (RTCP)

RTCP Bandwidth

Media
RTCP maximum bandwidth
Audio
5
Video
10

Overall Bandwidth by session type

Combining all this information together, Microsoft have come up with a table of maximum bandwidth utilisation (with and without FEC) and also typical bandwidth utilisation.

Audio/Video Capacity Planning for Peer-to-Peer Sessions

Media
Codec
Typical stream bandwidth
Maximum stream bandwidth without FEC
with FEC
Audio
RTAudio Wideband
39.8
62
91
Audio
RTAudio Narrowband
29.3
44.8
56.6
Main video CIF
RTVideo
220
260
Not applicable
Main video VGA
RTVideo
508
610
Not applicable
Main video HD
RTVideo
1210
1510
Not applicable
Panoramic video
RTVideo
269
360
Not applicable

Audio/Video Capacity Planning for Conferences

Media
Typical codec
Typical stream bandwidth
Maximum stream bandwidth without FEC
with FEC
Audio
G.722
46.1
100.6
164.6
Audio
Siren
25.5
52.6
68.6
Main video CIF
RTVideo
220
260
Not applicable
Main video VGA
RTVideo
508
610
Not applicable
Panoramic video
RTVideo
269
360
Not applicable

Audio Capacity Planning for PSTN

Media
Typical codec
Typical stream bandwidth
Maximum stream bandwidth without FEC
with FEC
Audio
G.711
64.8
97
161
Audio
RTAudio Narrowband
30.9
44.8
56.6

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