The idea behind this new feature:
- Multicast packets are always sent on the highest mandatory rates from the AP to the wireless client (might not reach clients at the edge of the cell, if the mandatory rate is not configured properly).
- No Ack for the multicast packets.
- Multicast packets are sent using best effort between the WLC and the AP then transmitted as multicast (using WLAN QoS) from the AP to the wireless clients.
WLC — (multicast as BE) –> AP — (highest mandatory rate, no ACK, WLAN QoS) –> Wireless client
The solutions will be very simple, don’t sent the packets as BE send them as Video (AF 41, CoS 4) & send them as uni-cast from the AP to the client to solve the reliability and the data rate issue. Hence VideoStream combines several elements that work together to improve the video user experience.
Note: The AP will convert multicast to unicast frames in hardware using Direct Memory Access (DMA).
VideoStream enables you to define multicast streams on the controller and reserve bandwidth on the AP radios for these streams, called resource reservation control (RRC ) and to give a priority value to each stream, to privilege the streams.
Video Stream Configurations:
Step 1: Multicast setting
- enable multicast globally
- set multicast mode to multicast-multicast
- enable IGMP snooping
Step 2: Enable Video Stream
- This can be done globally (recommended) or per radio band.
- Enable it per WLAN (This new check box will appear after enabling it globally not per band)
Step 3: Adjust the configurations per radio band
- Unicast Video Redirect: enabled automatically while enabling Multicast Direct globally which means the AP will send unicast to clients.
- Multicast Direct Admission Control:
- CAC for Video Stream which is the sum of voice and video traffic on a radio interface.
- Decide the percentage of the AP bandwidth that can be allocated to media streams (video and voice), 85% by default.
- Decide the minimum data rate for the client to be allocated a media stream (voice or video)
- Decide how many of the lost packets should be re-sent, default is 80%
- Media Stream – Multicast Direct Parameters:
- Number of video streams are allowed per AP radio and per client.
- Best Effort QoS Admission check box to allow non WMM clients to request and receive. Video Stream as video will be sent using WMM marking, only WMM clients are expected and allowed to request and use the unicast video stream.
Step 4: Create the streams and customize them
Set stream name, destination multicast address or range and expected bandwidth.
Bandwidth Reservation Control (RRC) Parameters:
- RRC helps the controller analyze the available bandwidth on the AP radio to only admit streams that have the space and allow to set priority which will take effect if no enough space in the cell, the WLC will privileges the streams with the higher priorities.
- Set average packet size and keep the RRC Periodic Update to force the controller to check the bandwidth availability at regular interval and alter the multicast stream admission accordingly.
- Set Violation option to decide what should happen if there is not enough space in the cell.
Note: to configure what message should be sent to users of a stream that has been dropped: Wireless -> Media Stream -> General page -> Session Message Config section.
- Optimizing Enterprise Video Over Wireless LAN White Paper
- Cisco Unified Wireless Network Solution: VideoStream Deployment Guide
- Configuring Video Streams 7.0