All things related to multicast

[Stig Venaas <>]

Prashant Jhingran wrote:
> Hi,
>
> It’s very difficult to pin point the problem with such limited
> information. However following is my prediction.
>
> The receiver should initially send IGMP or MLD unsolicited joins (for
> IPv4 and IPv6 respectively) for receiving a mcast streams. The receiver
> should also send IGMP/MLD join messages on receiving periodic IGMP/MLD
> queries (in response) from the router in order to continuously receive
> the mcast streams. If it doesn't then the receiver will encounter the
> problem which you are experiencing.

Yes, I think this is a likely reason, I've seen this happening several 
times. 4 minutes is longer than I would expect though. If you never 
respond to the regular IGMP/MLD queries, it should fail earlier.

Another similar problem I've seen was with PIM. The tree was created 
initially, but after about 3 minutes (I think it might be 210 seconds) 
multicasdt stopped. The reason was an MTU mismatch. The initial join 
messages reached the source, but for the periodic ones, the router with 
to large MTU configured had aggregated so many j/p's in one PIM message 
that it exceeded the MTU of its peer.

This seems more like your problem... At least that the problem is with 
sending/receiving periodic PIM joins at some location.

> However for receiving from local source (lying on the same LAN), the
> receiver needn’t send IGMP joins (in response to queries, in fact no
> need of a router itself). Thus for local source, lying on the same LAN
> there would never be a problem.

Unless an IGMP snooping/proxying switch is involved.

Stig

> Therefore I feel that the application which you are using for receiving
> the stream is not responding to the IGMP/MLD queries sent periodically
> by the router and hence the router is deleting the multicast tree thus
> freezing the streams once IGMP/MLD entries expire. Some mcast apps send
> periodic IGMP/MLD unsolicited reports thus serving the purpose of
> periodic refresh of IGMP/MLD entries.
>
> BTW Which mcast app are you using for receiving mcast stream? Try "VLC"
> free ware it works fine.
>
> -Regards,
> Prashant Jhingran
>
> Huawei Technologies
> Shenzhen, P R China
> Off#+86-755-28976431
> Mobile#+86-13480651542
> ==================================================================
> "You define your responsibilities and you define your limits" 
> -Sri Sri Ravi Shankar www.artofliving.org
> ==================================================================
>
> -----Original Message-----
> From: Ramon Sierra [mailto:] 
> Sent: Wednesday, July 19, 2006 10:33 PM
> To: 
>
> Subject: Help
>
>
> Hi,
>
> I need help with the following problem.  All multicast streams I am 
> receiving get freeze after 4 mins or so.  If I'm the source or any of my
>
> campuses is the source there is no problem.  Anyone is having the same 
> problem?  Anyone has any clue about what could be the problem?
>
> Any suggestion will be appreciate it,
>
> Ramón