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Flex 7500 Wireless Branch Controller Deployment Guide
Client ACL Support
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Cisco 7510 Controller
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Cisco 8510 Controller
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Cisco WiSM-2 Controller
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Cisco 2504 Controller
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vWLC
IGMPv2 is the supported version on all of the controllers.
VideoStream is supported on 802.11n models of APs consisting of Cisco Aironet 1140, 1250, 1260,
1520, 1530, 1550, 1600, 2600, 3500, 3600 series APs and 802.11ac models 3700 and 2700 series APs.
Theory of Operation
Before going into details about the VideoStream feature, you should understand some of the shortfalls
in Wi-Fi multicast. 802.11n is a prominently discussed wireless technology for indoor wireless
deployments. Equally prominent requirement is seen in multimedia service on an enterprise and branch
network, in particular, video. Multicast does not provide any MAC layer recovery on multicast and
broadcast frames. Multicast and broadcast packets do not have an Acknowledgement (ACK), and all
packet delivery is best effort. Multicast over wireless with 802.11a/b/g/n does not provide any
mechanism for reliable transmission.
Wireless deployments are prone to interference, high channel utilization, and low SNR at the edge of the
cell. There are also many clients sharing the same channel but have different channel conditions, power
limitations, and client processing capabilities. Therefore, multicast is not a reliable transmission
protocol to all the clients in the same channel because each client has different channel conditions.
Wireless multicast does not prioritize the video traffic even though it is marked as Differentiated Service
Code Point (DSCP) by the video server. The application will see a loss of packets with no ACK, and
retries to the delivery will be bad. In order to provide reliable transmissions of multicast packet, it is
necessary that the network classify queues and provisions using Quality of Service (QoS). This virtually
removes the issue of unreliability by eliminating dropped packets and delay of the packets to the host by
marking the packets and sorting them to the appropriate queue.
Even though the 802.11n, and now 802.11ac, adaptation has gained momentum both with the network
and clients, wireless multicast has not been able to use the 802.11n and 802.11ac data rates. This has
also been one of the factors for an alternate mechanism for wireless multicast propagation.
VideoStream
VideoStream provides efficient bandwidth utilization by removing the need to broadcast multicast
packets to all WLANs on the AP regardless if there is a client joined to a multicast group. In order to get
around this limitation, the AP has to send multicast traffic to the host using Unicast forwarding, only on
the WLAN that the client is joined and at the data rate the client is joined at.
VideoStream can be enabled globally on the controller. The feature can also be enabled at the WLAN
level, and provides more control to the administrator to identify specific video streams for Multicast
Direct functionality.
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