[streaming] Re: what happend when roaming

[Jean-Paul Saman]

Rémi Denis-Courmont wrote:

>Le Samedi 5 Mars 2005 08:04, Yong Chu Eu (������) a écrit :
>  
>
>>i stream video (based on MH's home address,IPv6 Multicast Address and
>>IPv4 Multicast address ) from my FreeBSd Multicast router to MH which
>>cover by my 2 access point. When i roam from my home network to
>>another network, the video stop for few second (i think around 4-5
>>second) then recover soon, later i type to change to another subnet
>>which have different essid, the same thing happen. Anyone can explain
>>tis? What happen inside? My test-bed is compile with MIPL 1.1 (Mobile
>>Ipv6).
>>    
>>
>
>I have no experience with Mobile IP, but I'm not sure if it is supposed 
>to handle multicast anyway (?) rather than just unicast.
>
>  
>
On some WLAN AP multicast is supported. Usually the implementation is 
not that well tested and leaves room for improvements.

>I'd assume the delay is due to the fact that the laptop does not send an 
>IGMP/MLD membership report as soon as it gets its new connectivity 
>(plus, maybe, some delay on the multicast router).
>  
>
In this case however:
1) a connection over which multicast is running is terminated, because 
of roaming. This results in the mutlicast being tore down if this takes 
more then x-seconds before the other WLAN AP requests the same multicast.
2) a new connection must be build up. It depends on the WLAN chip and 
driver how much time this takes. Standard drivers handle this between 10 
- 60 seconds
3) When the new connection is setup (this will take x-seconds) a request 
for multicast is made. The multicast routers in between the new WLAN AP 
and the former WLAN AP forward the request to sent the multicast stream.

Greetings,
Jean-Paul Saman.

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