Subject: [SIP] a simple query but important....

From: "rahul pande" <[email-masked]>
Date: Tue, 22 Aug 2000 03:38:04 GMT

hello all,
   just a general query that has come up. I have got to know that many 
organizations who have a big LAN(i.e. consisting of various subnets attached 
with routers), allow only unicast  enabled routers to exist in their LAN, 
because of the premonition of excess network traffic etc... In this scenario 
how can i do conferencing (using multicasting and not MCU).Can i do 
something at the SIP stack level(i.e. software level) or i need to ask the 
network adm. to enable multicast packets also to pass through routers. Would 
something like Mbone work inside the LAN(i'm not sure!!!). Please give some 
insight into the above situation.
        Thanking you all,
           rahul.
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From: Jonathan Rosenberg <[email-masked]>
Date: Tue, 22 Aug 2000 01:31:57 -0400

rahul pande wrote:
> how can i do conferencing (using multicasting and not MCU).

You can run tunnels.

Can i do
> network adm. to enable multicast packets also to pass through routers. 

Neither. SIP has nothing whatsoever to do with this. Running tunnels to
an mbone router requires only that your admin pass IP in IP, which I
would guess will work fine.

> Would
> something like Mbone work inside the LAN(i'm not sure!!!).

If it runs IP, it can be carrier pidgeon
(http://www.normos.org/ietf/rfc/rfc1149.txt), LAN, whatever.

-Jonathan R.
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From: Samir Chatterjee <[email-masked]>
Date: Tue, 22 Aug 2000 10:18:24 -0700

Rahul:
Many large organizations that have enterprise networks comprising of several
LANs and routers typically are often not multicast enabled. To do multicasting,
certain subnets and their associated routers would have to run mrouted (or some
of the newer protocols PIM etc) so that multicast addressing can be understood
and forwarded. To be connected to the MBONE, it is also important to set up a
tunnel (IP-over-IP) to the nearest MBONE node so that intermediate routers can
still forward multicast packets.
Now related to your concerns about doing conferencing. If you run an MCU
somewhere (assuming SIP based), then it could still mix media traffic using
unicast streams and send the content to respective IP hosts who have joined a
session. However, if your network is multicast enabled, then of course you gain
efficiency using multicasting the content from the MCU. I am not sure if there
is anything special you have to do inside the SIP stack. But your application
should send packets to a multicast session address if multicasting is supported.

Samir

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