All things related to multicast

["Roberts, Geoffrey P" <>]

Alan,

I am organizing a cisco - Meru "shootout" within the next weeks and will
have a lab set up with 30 PC's, 5 AP's and a server.   I can add a
multicast "test" to the mix, if indeed either vendor support.

Regards Paul Roberts

-----Original Message-----
From: Alan Crosswell 
[mailto:]
 
Sent: Wednesday, April 16, 2008 12:00 PM
To: wg-multicast
Subject: call for volunteers: WiFi multicast vendor survey

At the last Joint Techs, we discussed that now that we had IP multicast
on wired networks all figured out(;-), it was time to start over from
scratch with IP multicast over WiFi.  The following rough notes
collected some of the questions to send to WiFi vendors to get their
responses.  I'm hoping some of you will volunteer to:

a) Review these questions and improve upon them.
b) Fill in the answers where you know them.
c) Contact your WiFi vendor(s) and ask them to respond to the questions
d) Report back to the group with your findings.

Please let me know if you can help with this.

/a

WiFi Multicast

driven by apps: iTunes sharing, zattoo, arootz, IPTV, etc.

Problems:

- flooding to all APs serving an SSID since there's no snooping.
- multicast sent at broadcast base rate (1 Mbps) to ensure all listeners
hear it
- unicast tunnels between lightweight APs and controller replicate
traffic

... and some hope or workarounds:

- IPv6 support requires multicast
- several vendors coming out with IGMP(MLD) snooping to:
  - distribute between controller and APs
  - limit traffic to only APs that have receivers associated
- some vendors using known state of slowest multicast receiver to
dynamically set the broadcast base rate.

Questionnaire for vendors:
 - please improve on these questions
 - please volunteer to take to your vendor (or potential vendors) and
report back to the group

- How is multicast sent to AP from the controller?
- Is multicast flooded to all APs in the SSID or just to AP with
interest?
- Is IGMP snooping implemented?  What version(s)?
- What about IPv6?  IPv6 requires multicast.
- Is MLD snooping implemented?
- Can multicast base rate be set higher than the broadcast rate?  What
are the limitations?
- How does multicast work w/WPA2 security?  Broadcast group key?
Multiple unicast?
- How does this work with 802.11n multipath?
- Is multiple unicast better due to retransmissions at 802.11 layer?