Before go into details of “video stream” feature we will look at how WLC handle a multicast packet without this feature. I have used the following basic setup for testing.

WLC is configured for multicast as outlined in “Configuring Multicast on WLC” post. Group address 239.255.255.101 is used for WLC->AP multicast. Multicast traffic coming from streaming source will be marked as AF41  at the fa1/0/19 switch port. When we look at traffic coming from the multicast source to WLC we will see something like this.

Since we have configured multicast on WLC this traffic will send to group address configured on WLC(i.e 239.255.255.101). Then all access points registered to this controller get this traffic. (In unicast mode WLC has to send this stream to each AP as unicast & hence it is not efficient & loading the WLC as this conversion is process intensive). You will see packet going from WLC to AP as below. Note that outer CAPWAP destination IP address changed to WLC multicast address & hence dest mac as well.

Even though outer CAPWAP is mapped to  AF41 marking, if you look at UP set by WLC (Monitor > Multicast > 239.255.255.200 ) you will see it is set to UP=0 & treat as normal multicast.

Now if you capture the wireless traffic over the air,  where my receiving laptop associated (in my case CH149) you can see the traffic received by wireless client. You will notice that 802.11 frame destination address is multicast MAC address and data rate is 24 Mbps (Highest mandatory data rate configured on 802.11 band). No user priority (UP) value set on wireless frame &  hence no QoS within the wireless cell.

Now if you go to client laptop & join to this multicast stream ,everything is perfect but video quality. Here is  a sample of video I can see on one of VLC client joined to 239.255.255.200  multicast group.

As highlighted in a previous post here are the drawback of legacy multicast configured on a WLC.

1. Multicast does not provide any MAC layer recovery on frame loss.
2. Video delivery (multicast) is at the highest mandatory data rates configured. Even client is associated with 802.11n data rates (max of 144 Mbps with 20MHz channel width) they cannot take any advantage of that to send these multicast traffic.
3. Wireless multicast does not prioritize video traffic even though DSCP marked by video server.

Now we will see how we will overcome these limitations by using “Video Stream” feature in WLC. This feature will make this multicast delivery more reliable by converting it to unicast at the AP. In this way if a frame is lost it can be communicated back to AP & packet will be re-transmitted. Also since it is unicast, it can send in  a rate where end device is associated to AP (not limited to highest mandatory data rate). Also WLC will give correct QoS UP for the frames send into wireless media eventually get the required priority.

Below section describe how you configure this feature & how you can verify its effect on video packets. First of all you need to enable this globally under Wireless->Media Stream section.

Then you need to add multicast stream details that you want to prioritize. You have to have clear idea about bandwidth utilization of your multicast stream. According to that you need to set max expected bandwidth. If you keep it low your video quality will be compromised, if you keep it high number of video clients can service from a given radio will be reduced. If you have multiple video streams (different group addresses) you can include that range in the start & end multicast IP address field. In my example I have used only single stream with single multicast group address. Hence start & end IP is same.

For the RRC parameters, there are pre-defined templates also available. If you application bandwidth is closely match with those profile values you can choose one of those profiles. Otherwise you have to configure these parameters manually. I have shown here manual settings I did.

RRC priority value range between 1-8 and value 8 mean highest priority. If your network has a most important video stream (CIO’s speech to everyone, Board meetings, etc), then you need to give that the highest priority. Traffic profile violation can be set to “best effort” or “drop”. It is recommended to keep it “best effort” as video is time sensitive & drop packet could cause noticeable quality degrade.

Once you enable VideoStream globally , then you can configure this under the radio band  or WLAN (per SSID) . It is always recommended to implement this on 5GHz band with 802.11n clients as they can take maximum benefit of this. Under 802.11a/n (or 802.11b/g/n) -> Media need to tick “Multicast Direct” feature. If you need you can control  max stream per radio & per client. If you tick “Best Effort QoS Admission” then no client will be rejected (even over subscription situation, but admit them with default QoS). It is recommended to leave it unticked , then  in a situation of over-subscription new video client will not accepted. Max media bandwidth is total bandwidth allocate to Voice & Video applications in wireless media. Therefore Voice & Video tab combined bandwidth configuration should be less than the value you configure in here (75% in my case)

Here is Voice & Video tab’s configuration in my example. Note that I have selected value 15% & 60%, so combined value is 75% which is configured under media tab.

You can enable this feature per SSID as well. To do this you have to select the WLAN -> QoS & select “Multicast Direct” feature.

That’s all for the configuring this feature. Now to verify you can check a video quality  of a multicast stream from a client perspective.This is the same video received by the client laptop once you configure VideoStream feature on WLC. See the difference it made.

Now if you look at a sniffer capture you would see what makes this difference. If you look at carefully, given packet has transmitted 104 Mbps (in legacy mode limited to highest mandatory data rate configured) & taken advantage of being “N” client with higher data rate capability. Also destination MAC  address of the wireless frame is Unicast (in the legacy mode it is Multicast) & hence improve the reliability of packet delivery.

QoS (User Priority ) of wireless frame correctly set to Video (in the legacy mode no UP set in wireless frame, even though CAPWAP header is having AF41 DSCP) & therefore traffic will get prioritized within the wireless cell. You can verify the same under Monitor > Multicast > Select the MGID for correct multicast group address (see below)

Here are few show commands you can use to verify in CLI mode.

(WLC1) >show media-stream group summary

Stream Name   Start IP       End IP         Operation Status
————- ————– ————– —————-
MRN-TV-CH1    239.255.255.200 239.255.255.200 Multicast-direct

(WLC1) >show media-stream group detail MRN-TV-CH1

Media Stream Name………………………….. MRN-TV-CH1
Start IP Address…………………………… 239.255.255.200
End IP Address…………………………….. 239.255.255.200
RRC Parmmeters
Avg Packet Size(Bytes)…………………….. 1200
Expected Bandwidth(Kbps)…………………… 3000
Policy…………………………………… Admit
RRC re-evaluation…………………………. periodic
QoS……………………………………… Video
Status…………………………………… Multicast-direct
Usage Priority……………………………. 8
Violation………………………………… fallback

(WLC1) >show media-stream multicast-direct state

Multicast-direct State……………………… enable
Allowed WLANs……………………………… 2,3

(WLC1) >show media-stream client summary

Number of Clients………………………….. 1

Client Mac         Stream Name  Stream Type  Radio WLAN  QoS    Status
—————–  ———–  ———–  —-  —-  —— ——-
a0:88:b4:35:c2:f0  MRN-TV-CH1   MC-direct    5     3     Video  Admitted

(WLC1) >show media-stream client MRN-TV-CH1

Media Stream Name………………………….. MRN-TV-CH1
IP Multicast Destination Address (start)……… 239.255.255.200
IP Multicast Destination Address (end)……….. 239.255.255.200

Client Mac         Dest IP Address  AP Mac             Radio  WLAN  QoS      Status
—————–  —————  —————–  —–  —-  ——-  ———-
a0:88:b4:35:c2:f0  239.255.255.200  a0:cf:5b:9e:e8:20  5     3     Video  Admitted