Network bandwidth requirements for Lync 2013 Media traffic

An important aspect of site planning is ensuring that the network can handle the media traffic generated by Lync Server. This section helps you plan media traffic. Media Traffic Network usage

Media traffic bandwidth usage can be difficult to calculate due to the number of different variables, such as codec usage, resolution, and activity level. Bandwidth usage is a function of the codec and flow activity that is used, which differs in different scenarios. The following table lists the audio codecs that are commonly used in Lync Server 2013 scenarios. Audio Codec Bandwidth

Audio Codec	Programme	Audio Load bit rate (KBPS)	bandwidth-only audio load and IP header (Kbps)	bandwidth audio load, IP header, UDP, RTP, and SRTP (Kbps)	bandwidth audio load, IP header, UDP, RTP, SRTP, and forward error correction (Kbps)
RTAudio Broadband	Point-to-point	29.0	45.0	57.0	86.0
RTAudio narrowband	Peering, PSTN	11.8	27.8	39.8	51.6
g.722	Meeting	64.0	80.0	95.6	159.6
g.722 Stereo	Equivalence, meeting	128.0	144.0	159.6	223.6
G.711	Pstn	64.0	80.0	92.0	156.0
Siren	Meeting	16.0	32.0	47.6	63.6

The bandwidth values in the table above are based on the 20 millisecond data sub-packet (50 packets per second) of Siren and g.722, which contains additional secure real-time Transport protocol (SRTP) overhead (in the conference scenario), and assumes that the flow is 100% active. If packet loss occurs on a link, forward error correction (FEC) is used dynamically to help maintain the quality of the audio stream.

The stereo version of the g.722 codec is used by a system that is based on Lync meeting room Edition, which enables stereo headset capture to allow listeners to better discern multiple speakers in a conference room.

For video, the default codec is the H.264/MPEG-4 Part 10 Advanced video encoding standard and its scalable video encoding extension for temporary scalability. To maintain interoperability with Lync 2010 or Office Communicator R2 clients, Rtvideo codecs are still used for peer calls between Lync 2013 and Legacy Clients. In a meeting session that uses both Lync 2013 and the Legacy Client, Lync 2013 endpoints may encode video using video codec and send the H. E Bitstream to Lync 2013, sending the Rtvideo bitstream to Lync 2010 or Office Comm Unicator R2 Client.

The required bandwidth depends on the resolution, quality, and frame rate. Each resolution has two correlated bit rates: maximum load bit rate The Lync 2013 endpoint uses this bitrate for the resolution of the maximum frame rate that the resolution can support. This value is important because it provides the highest quality and highest frame rate video.
minimum load bit rate when this bit rate is lower, the Lync 2013 endpoint switches to the next lower resolution. To ensure a specific resolution, the available video payload bitrate must not be lower than this minimum bitrate for that resolution. This value allows you to understand the lowest possible value when the maximum bit rate is not available or impractical, so it is worth paying attention to. For some users, this low bitrate video experience may be considered an unacceptable video experience, so be cautious when considering using these minimum video load bit rates. Note that for video scenes where the user moves little or no user movement, the actual bit rate may also be temporarily below this minimum bit rate.

Lync 2013 supports more resolutions. This allows you to better tune to different network bandwidth and receive client features. Additionally, the default aspect ratio for Lync 2013 has been changed to 16:9. The network camera still supports a 4:3 aspect ratio, which does not allow capture at 16:9 aspect ratio. Video resolution Bandwidth

Video Codec	resolution and aspect ratio	maximum video load bit rate (Kbps)	minimum Video load bit rate (Kbps)
H.	320x180 (16:9) 212x160 (4:3)	250	15
H.264/rtvideo	424x240 (16:9)) (4:3	350	100
H.	480x270 (16:9) 424x320 (4:3)	450	200
H.264/rtvideo	640x360 (16:9) 640x480 (4:3)	800	300
H.	848x480 (16:9)	1500	400
H.	960x540 (16:9)	2000	500
H.264/rtvideo	1280x720 (16:9)	2500	700
H.	1920x1080 (16:9)	4000	500
H.264/rtvideo	960x144 (20:3)	500	15
H.	1280x192 (20:3)	1000	250
H.	1920x288 (20:3)	2000	500

Video FEC is included when using the video payload bitrate, so the video FEC values are the same or not used.

The endpoint does not continuously flow out of audio or video packets. Depending on the scenario, the level of flow activity is also different, and these levels indicate how often packets are sent for the stream. The flow activity depends on the media and the scenario, not on the codec being used. In a peering scenario: The endpoint sends an audio stream only when the user is talking.
Both parties will receive the audio stream.
If you use video, both endpoints send and receive video streams during the entire call.
For a video scene with little or no movement, the actual bit rate may be temporarily very low if the video codec skips the encoded area of the video without making changes.

In a meeting scenario: The endpoint sends an audio stream only when the user is talking.
All participants will receive the audio stream.
If you use video, all participants will receive a maximum of 5 receive video streams and a panorama (for example, Aspect ratio 20:3) video stream. By default, 5 receive video streams are based on the current speaker history, but users can also manually select the participants from whom to receive the video stream.
Each contributor that enables a user to send a video stream will send one or more video streams. Lync 2013 adds the ability to send up to 5 video streams to optimize video quality for all receiving clients. The actual number of video streams that will be sent is determined by the sender based on the CPU capacity, the available uplink bandwidth, and the number of receiving clients requesting a specific video stream. The most common scenario is when the old client joins the meeting, sending 1 H. x and a Rtvideo video stream. Another common scenario is to send several H + + video streams (for example, using different video resolutions) to accommodate different receiver requests.

In addition to the bandwidth required for real-time Transfer Protocol (RTP) traffic for audio and video media, the real-time Transport Control Protocol (RTCP) also requires bandwidth. The RTCP is used to report the statistics and out-of-band control of RTP streams. When planning, use the bandwidth values in the following table to plan for RTCP traffic. These values represent the maximum bandwidth used for RTCP, and these values for the audio stream and the video stream vary depending on the control data. RTCP Bandwidth

Media	RTCP Maximum bandwidth (Kbps)
Audio	5
Video (only H. E or rtvideo being sent/received)	10
Video (H. E and Rtvideo being sent/received)	15

For capacity planning purposes, the following two bandwidths are important: the maximum bandwidth that will be used by the maximum bandwidth stream that does not use FEC , including typical flow activity in scenarios that do not use FEC, and typical codecs used. This is a stream that is 100% active and does not have the bandwidth to trigger the use of FEC because of lost packets. It is important to calculate the amount of bandwidth that must be allocated to allow the codec to be used by a given scenario.
The maximum bandwidth used for the maximum bandwidth flow using FEC includes typical flow activity in scenarios using FEC and typical codecs used. This is the bandwidth at which the stream is 100% active and triggers the use of FEC to improve quality due to loss of packets. This is important for calculating the amount of bandwidth that must be allocated to allow for the use of codecs for a given scenario, and to allow the use of FEC to maintain quality under conditions of packet loss.

Another bandwidth value, "Typical bandwidth", is also listed in the following table. This is the average bandwidth used by the stream, including the typical flow activity in the scenario and the typical codec used. This bandwidth can be used to estimate the amount of bandwidth used by media traffic over a given time, but not for capacity planning, because individual calls exceed this value when the activity level is above the average level. The typical video stream bandwidth in the following table is based on a combination of different video resolutions observed in the measured customer data. For example, in a peer session, most users will use the default Video rendering window, but a certain percentage of users will increase or maximize the Lync application to achieve higher video resolution.

The table below provides these three bandwidth values in different scenarios. audio/video capacity planning for peering sessions

Media	codec	typical stream bandwidth (Kbps)	maximum flow bandwidth without FEC	maximum flow bandwidth using FEC
Audio	RTAudio Broadband	39.8	62	91
Audio	RTAudio narrowband	29.3	44.8	56.6
Primary video When you call a Lync 2013 endpoint	H.	460	4010 (for maximum resolution 1920x1080)	Not applicable
Primary video When you call a Lync 2010 or Office Communicator R2 endpoint	Rtvideo	460	2510 (for maximum resolution 1280x720)	Not applicable
Panorama video When you call a Lync 2013 endpoint	H.	190	2010 (for maximum resolution 1920x288)	Not applicable
Panorama video When you call a Lync 2010 or Office Communicator R2 endpoint	Rtvideo	190	510 (for maximum resolution 960X144)	Not applicable

audio/video capacity planning for meetings

Media	a typical codec	typical stream bandwidth (Kbps)	maximum flow bandwidth without FEC	maximum flow bandwidth using FEC
Audio	g.722	46.1	100.6	164.6
Audio	Siren	25.5	52.6	68.6
Master Video Reception	H. I and/or Rtvideo	260	8015	Not applicable
Main video Send	H. I and/or Rtvideo	270	8015	Not applicable
Panoramic Video reception	H. I and/or Rtvideo	190	2010 (for maximum resolution 1920x288)	Not applicable
Panorama Video Send	H. I and/or Rtvideo	190	2515 (for sending bitstream using multiple resolutions/codecs)	Not applicable

For the main video, the typical and maximum stream bandwidth is used for all received video streams and for all the aggregated bandwidth of the sending video stream. Even for multiple video streams, the typical video bandwidth is less than the peer scenario, because many video conferencing uses content sharing, which causes the video window to be much smaller, resulting in a lower video resolution. For example, if there are two incoming 1920x1080p video streams, the maximum aggregated video load bandwidth that will be used for both the send and receive streams is 8000 Kbps.

The typical streaming bandwidth for panoramic video is based on the devices currently available, which stream only the largest 960x144 panoramic video. Once a device with 1920x288 Panorama video becomes available, the typical stream bandwidth should be increased. Audio Capacity Planning for the PSTN

Media	a typical codec	typical stream bandwidth (Kbps)	maximum flow bandwidth without FEC	maximum flow bandwidth using FEC
Audio	G.711	64.8	97	161
Audio	RTAudio narrowband	30.9	44.8	56.6

The network bandwidth values in these tables represent only one-way traffic, including the RTCP traffic overhead of 5 Kbps assigned to each stream. For video, the maximum video bit rate is used to calculate the maximum stream.