Subject: newbee question

From: "Bakstad, Jacob" <[email-masked]>
Date: Mon, 9 Jul 2001 12:05:49 +0200

Hi all,

I'm pretty new to the concept of MANET, and have a banal question. Please
don't look at this as Spam, 'cause it's an issue to me at the moment.

Is IGMP an issue when constructing a multicast routing protocol in MANET. I
mean, of course a multicast protocol must support the concept of IGMP, but
can a implementation of a routing protocol, use and control IGMP packets? In
my head, the multicast protocol can't see or/and alter the IGMP packets,
because it's a call the OS. So if you want control over the IGMP you'll have
to alter the OS, but then you'll lose kernel compatibility.

When constructing the protocol, you can set a requirement to the OS on which
the protocol runs, that it supports IGMP. So the program which wants the use
multicast, sends a OS call requesting to join a group. IGMP is done, and the
multicast protocol can use the table which is created by IGMP.

This might be a wild guess, so please correct me if I'm wrong.

Regards

Jacob Bakstad

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From: "Per Olesen" <[email-masked]>
Date: Tue, 10 Jul 2001 23:36:13 +0200

Hi all,

I would like to share my thoughts on IGMP and manet multicast.

Existing multicast applications in wired networks all use existing OS system
calls to join/leave multicast host groups, which results in the IP stack
issuing IGMP packets, to make the router know about group memberships on the
local net. If these existing applications are to work on a multicast routed
manet, without changing either one of the application and the OS api, IGMP
must be an issue to a manet multicast routing protocol.

A manet multicast routing protocol is to build the multicast routing table,
and to do this, it must know about the group memberships. A manet multicast
routing protocol implementation, running in user space to preserve kernel
compatibility, to my knowledge, is not able to intercept the local multicast
group join/leave calls, nor see the IGMP packes on the net. If anyone know
something about this being possible, I would be delighted to hear about it.

As Jacob mentions, it could be a solution, if the multicast routing protocol
implementation (again, running in user-space), could "look into" the group
membership tables which the IP-stack maintains, maybe even get
acknowledgements when it gets updated. Can anyone share some light on if
some OS calls for this exists (or not exists)?

Regards, Per Olesen