Subject: RE: [magma] multicast senders behind an IGMP Proxy

From: "Dan Wing" <[email-masked]>
Date: Mon, 13 Aug 2007 10:32:20 -0700

> -----Original Message-----
> From: Prashant Jhingran [mailto:[email-masked]] 
> Sent: Friday, June 22, 2007 3:01 AM
> To: 'Dan Wing'; [email-masked]; [email-masked]
> Cc: 'Toerless Eckert'
> Subject: RE: [magma] multicast senders behind an IGMP Proxy
> 
> Hi,
> 
> I would like to suggest following methods to  resolve this
> issue:
> 
> - TTL scoping can be used to control the distribution of
> multicast traffic with the objective of easing stress on
> scarce resources viz. bandwidth.

Toerless and I went back and forth on this suggestion, and
finally decided on the following text in the appendix of
multicast-09 (which we're about to publish):

   A multicast source that wants its traffic to not traverse a router
   (e.g., leave a home network) may find it useful to send traffic with
   IP TTL=1.  Both ASM and SSM sources may find this useful.

-d

> - Another way (and probably a preferred choice) would be to
> use administratively scoped IP multicast [rfc2365]. 
>
> Moreover, these methods can (to a certain extent) help in
> achieving privacy.
> 
> PS: "sending audio to all of your IP-enabled speakers
> distributed throughout your house" seems to be very
> ambitious usage of multicast :-) 
> 
> Regards,
> Prashant Jhingran
> 
> Huawei Technologies
> +91-80-41117676 Ext -7175
> +91-9448927814
> 
> "Sing, dance, serve, meditate and celebrate" 
>  - www.artofliving.org  
> 
> -----Original Message-----
> From: Dan Wing [mailto:[email-masked]] 
> Sent: Friday, June 22, 2007 5:48 AM
> To: [email-masked]; [email-masked]
> Cc: Toerless Eckert
> Subject: [magma] multicast senders behind an IGMP Proxy
> 
> During WGLC, there was clear consensus from MAGMA and MBONED
> that supporting
> multicast senders behind the IGMP Proxy device was
> desirable.  However,
> while wrapping up draft-ietf-behave-multicast-07, Toerless
> pointed out a
> problem with multicast senders behind an IGMP Proxy device
> (any IGMP Proxy
> device -- not just an IGMP Proxy in a NAT).
> 
> The problem is that any multicast flows generated behind the
> IGMP proxy will
> be forwarded up the access link towards the Internet -- even
> for flows that
> you want to keep within your network.  Concrete examples of
> generating
> multicast within a home network include:
> 
>  * sending audio to all of your IP-enabled speakers
> distributed 
>    throughout your house,  
>  * IP-enabled intercom system, 
>  * HD video to multiple telvision sets (kitchen and living
> room).
> 
> In each case, you "could" do unicast, but especially for HD
> one might easily
> envision not having sufficient bandwidth or not wanting to
> waste the
> bandwidth (which might be used for other things).
> 
> Does anyone have suggestions on how this might be resolved?
> 
> -d
> 
> 
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