All things related to multicast

[Bruce Curtis <>]

On Dec 11, 2009, at 2:15 PM, Mike McBride (mmcbride) wrote:

>>> The most successful iptv over wifi today combines 11n with unicast
>> over
>>> the air (multicast down to the edge then convert).
>> 
>>  That seems like a waste, the delivery over the air is a natural fit
>> for multicast, all of the clients will hear the packet and the packet
>> takes up a time slot whether it is unicast or multicast.
> 
> The problem is not the medium time reservation but that, unlike unicast
> packets, mcast packets are not acknowledged in 802.11. wifi typically
> operates with a PER of 1-10% (due to collisions, fading, interference)
> and you need acks. Packet error rates of multicast traffic can therefore
> be quite high. This doesn't bode well for iptv. The 802.11aa standard is
> looking at ways to address this issue and there are some vendor specific
> ways to get around this today including sending unicast.
> 
> mike

  Interesting problem, it sounds like 802.11aa will have a method of reliable 
multicast for the last hop (the wireless hop with the noticeable error rate.) 
 The number of clients per AP will have an upper bound but the channel could 
still be flooded with requests to retransmit a a packet lost due to 
interference unless the clients listen for other clients requesting the 
retransmission etc.

  

> 
>>> 
>>> AMT could therefore be another good solution here although that
> means
>>> you are dealing another tunnel in addition to CAPWAP.
>>> 
>>> mike
>>> 
>>>> -----Original Message-----
>>>> From: wiedel 
>>>> [mailto:]
>>>> Sent: Friday, December 11, 2009 8:57 AM
>>>> To: 
>>>> 
>>>> Cc: Bob Gerdes; wg-multicast
>>>> Subject: Re: Multicast implementations on Wireless
>>>> 
>>>> Folks,
>>>>    I don't want to be a commercial here, but you might check out
>>>> Ruckus Wireless if you are doing IPTV.   They grew up in that space
>>> and
>>>> have just patented some multicast delivery systems for IPTV.
>>>> Apparently
>>>> in use at several hotels with success for HDTV as well as standard
>>> def.
>>>> www.ruckuswireless.com would be their home page.
>>>>    James
>>>> 
>>>> 
>>>> 
>>>> Greg Shepherd wrote:
>>>>> This seems like an ideal deployment scenario for AMT.
>>>>> 
>>>>> Greg
>>>>> 
>>>>> On Thu, Dec 10, 2009 at 1:15 PM, Bob Gerdes
>> <>
>>>> wrote:
>>>>>> Greetings,
>>>>>>  In previous exchanges, there have been discussions regarding
>>>>>> implementations of multicast on various wireless networks (one
>>> noted
>>>> below).
>>>>>> In another, folks were going to check with specific vendors.
>>>>>> 
>>>>>>  We are looking for any cases where multicast (especially
>>> multiple
>>>> IPTV
>>>>>> channels) has been implemented on a wireless network for mobile
>>>> users.
>>>>>> 
>>>>>>  In checking with different vendors, we had a conversation with
> a
>>>>>> distributor who is suggesting that wireless vendors are
>>> implementing
>>>> a
>>>>>> streaming service to redistribute a multicast stream. In another,
>>>> apparently
>>>>>> some folks have had some success with Aruba, but haven't gotten
>>>> followup
>>>>>> info yet. So, hopefully you might have some better experiences or
>>>> updates
>>>>>> since last year.
>>>>>>   Thanks for your considersation,
>>>>>>     Bob
>>>>>> 
>>>>>> Backgroud: our group is working with our TV group on an IPTV
> pilot
>>>> service
>>>>>> using VideoFurnace/Haivision servers. We have been working with
>> our
>>>>>> networking group to get multicast working across campus. Our
>>>> Wireless group
>>>>>> uses Meru access points and BlueSocket for authentication and
>>>> policy, but
>>>>>> they have not been able to make progress with multicast on
>>> Wireless.
>>>> One
>>>>>> issue is that we would need to move the infrastructure to 802.11N
>>> or
>>>> better.
>>>>>> 
>>>>>> Bob Gerdes
>>>>>> Office of Instructional and Research Technologies (OIRT)
>>>>>> Rutgers, The State University
>>>>>> Phone: (732) 445-1438   Fax: 445-5539
>>>>>> 
>>>>>> On Wed, 15 Oct 2008, Alan Crosswell wrote:
>>>>>> 
>>>>>> Subject : Re: notes from BoF
>>>>>> 
>>>>>>> Multicast WG BoF Wed Oct 15, 2008
>>>>>>> 
>>>>>>> Items discussed follow:
>>>>>>> 
>>>>>>> * High bandwidth multicast over WiFi
>>>>>>> - no progress on getting any significant information from
> vendors
>>>> other
>>>>>>> than the realization that there are a number of problems with
>>>>>>> rate limiting, flooding, sending all multicast down tunnels to
>>>> APs, etc.
>>>>>>> - See Bruce's mail regarding Cisco APs and roaming.
>>>>>> 
>>> 
>> 
>> 
>> ---
>> Bruce Curtis                         
>> 
>> Certified NetAnalyst II                701-231-8527
>> North Dakota State University
> 
> 


---
Bruce Curtis                         

Certified NetAnalyst II                701-231-8527
North Dakota State University