All things related to multicast

[Alan Crosswell <>]

multicast BoF notes 1/21/08

Stig presented mcview, a tool to view multicast state that uses SNMP and
a group of agents
http://software.uninett.no/mcview

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?

Possibility of adding WiFi to the LAN portion of hands-on workshops:
  - WiFi interaction/interference with host site is a concern.


/a