Controllerless Networks

Dear All,

 I have a multicasting speed degradation problem with details as below topology.

Basic setting like below:

-Unicasting Routing protocol is OSPF. Working normal.

-On the middle point, two IAP-277 have connection with P2P Bridging Mode(Mesh Portal/Point). No special configuration for multicasting.

-PIM-SM is multicasting protocol to get neighborship for each L-3 Switches(router). I can see the normal working status on “show ip multicast forward” on Alcatel-Lucent OmniSwitch command.

-RP role is the right side switch, ip 10.20.11.254 for temporary testing.

I see the below problem:

1. Multicast traffic speed is too slow, so we cannot see proper image of CCTV, too bad image quality.
2. When we play VLC Player as multicasting client, we watch the TCP Monitor Plus program to see traffic flow and statistics. The traffic flow is too much fluctuated range between  1Mbps and 4Mbps.
3. VMS(Video Management System) request around 10 Multicast Stream to CCTVs. We can see only one video stream and also video quality is too bad. We try to view multiple CCTV Channel that has each seperate multicast address, but We only see one CCTV Channel.
   
4. We are using 802.11ac/5Ghz Only/ 80Mhz/3SS/VHT Mesh Link.

My Question is:’

1. I think is some kind of "Basic Rate" problem. How cat I maximize rate for Multicast transmisstion?
   
2. Can Only One Mesh Portal/Point do support only one Multicast Channel on Aruba IAP-277?
   
3. Would you send or recommand me some check point on configuration of IAP-277 to solve this problem?
4. Would you send or recommand me some configuration for IAP-277 to increase Multicasting Traffic Performance.

Best Regards,

Moon-Kee Bahk.

Attachment(s)

R02-AP-V200-VC.txt   3 KB 1 version

My advice would be to open a TAC case. WIthin IAP there are some settings not exposed or configurable within an IAP mesh deployment that is exposed with a controller-based deployment. 

There may also be some enhancements for IAP coming in IAP 4.3 (expected Sept/Oct), but again TAC would need to run this down to be sure it would apply to your config. 

In the interim, the best you can do is disable all but the 36, 48, and 54Mbps rates on the 5Ghz radio to hopefully force the 'basic' rate to 36Mbps, which should force the multicast rate (which by the standard is defined as the lowest basic rate) to be fast enough to carry your traffic. USUALLY this would be set as part of the ESSID profile, but I'm not sure how to adjust that for a mesh cluster RF profile (as it may not yet be exposed). 

Also to your other question, if you need to carry qty 10 multicast streams at 10Mbps each, that will likely never work over a mesh link. A single multicast stream can eat up the channel utilization by itself (it's the nature of multicast traffic when sent over the air). If opening a TAC case to hopefully uncover the rate adjustment for basic rates doesn't work or doesn't provide enough headroom, you may need to look and see if you can convert those cameras to unicast data streams and subscribe via RTSP or some other control mechanism. 

Dear jhoward,

Thanks for your good advice, so helpful to me.

You mention about 

". A single multicast stream can eat up the channel utilization by itself (it's the nature of multicast traffic when sent over the air). ". 

My understanding is that the mulicast can support only one channel, can not support multiple channels simutaneously. is it correct?

if it is correct, how about this.

If we use controller-based AP-277 with Mesh Link, this kind of limitation will happend same.

if we use MSR-2000 or MSR-4000 Series with Mesh Link, this kind of limitation will happend same.

if we use other vender product like Cisco, Aerohive, will happend same on Point-to-Point Mesh Link.

Regards,

Moon-Kee Bahk.

With controller-based AOS, you can better configure the mesh radio configuration to drop all but the highest basic rates. MSR2K/4K would allow that as well, BUT you're better off with 11ac than 11n. 

I'm not sure what you mean by 'multiple channels', are you talking about multiple RF channels at the same time? If that's the case, you are correct, there is no product that would let you put each mcast stream on a different RF channel on the 5Ghz. 

The same issues apply on any vendor. Carrying true multicast traffic over the air is very difficult due to the nature of the mcast traffic. You are going in the right direction by looking at disabling the lower data rates and forcing mcast out at the higher data rates, but IAP limits you in not being able to configure that.

My meaning of multiple mcast channel is multiple different mcast stream(have Multiple mcast addresses) transmit together on one RF Channel.

You mean that one RF Channel can send/receive multiple mcast stream simultaneously. This is very, very important point for me. Is it correct?

But the RF bandwidth of multicast are limit with “basic rate, the 36, 48, and 54Mbps rates on the 5Ghz radio”, can not support RF Channel bonding, Right?

Even though IAP-277 can not config basic rate to 54Mbps. Is this right?

Also, every RF vendor has same kind of bandwidth limitation which use only basic rate for multicast transmission.

Moon-Kee Bahk.

You can try to push more than one multicast stream over the same AP, the bandwidth or rate of the multicast stream dictates whether you can get most of each stream or not. For example, pushing multiple mcast streams where each stream is a few hundred kbps, that might be OK. Pushing multiple multicast streams where each stream is 10Mbps is not. 

Correct, multicast streat, by their spec, are carried at either the lowest basic rate, or if there is a configuration option to raise that value, it can be modified. IAP doesn't support raising that value currently. There might be a release of Instant code in the Sept/Oct time frame that MAY work over mesh, but I haven't seen it yet so I can't test it to know. 

Yes every vendor should be following the multicast specification.

For summary, please give answer to me about:

1. What is the maximum bandwidth for multicast can use on IAP-277 Mesh Link now?
2. What is the maximum bandwidth for multicast can use on Controller-based AP-277 Mesh Link now?
3. What is the maximum bandwidth for multicast can use on MSR-2000 or MSR-4000 Series now?

If you need a firm answer for #1, I would check with TAC but my guess would be whatever your radio basic rate is set to. What I don't know and cannot test right now is if the mesh SSID defaults to the radio config or if it gets it's own rate config.

For #2, you can go as high as 54Mbps by disabling all basic rates below 54Mbps. 

For #3, should be the same as #2. But you should engage TAC so that the specialists can answer. There are multicast enhancements for BSS, but it's not clear if this applies to the mesh radio carrying wired multicast traffic over the air.