[magma] Question about IGMPv3 state change

Kunal Shah <kunal.shah@ericsson.com> Mon, 14 February 2011 19:58 UTC

Return-Path: <kunal.shah@ericsson.com>
X-Original-To: magma@core3.amsl.com
Delivered-To: magma@core3.amsl.com
Received: from localhost (localhost []) by core3.amsl.com (Postfix) with ESMTP id 711263A6C4E for <magma@core3.amsl.com>; Mon, 14 Feb 2011 11:58:41 -0800 (PST)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -1.998
X-Spam-Status: No, score=-1.998 tagged_above=-999 required=5 tests=[BAYES_00=-2.599, HTML_MESSAGE=0.001, J_CHICKENPOX_21=0.6]
Received: from mail.ietf.org ([]) by localhost (core3.amsl.com []) (amavisd-new, port 10024) with ESMTP id n2KTS66IPS9u for <magma@core3.amsl.com>; Mon, 14 Feb 2011 11:58:40 -0800 (PST)
Received: from imr3.ericy.com (imr3.ericy.com []) by core3.amsl.com (Postfix) with ESMTP id 9FF053A6AB1 for <magma@ietf.org>; Mon, 14 Feb 2011 11:58:40 -0800 (PST)
Received: from eusaamw0707.eamcs.ericsson.se ([]) by imr3.ericy.com (8.13.8/8.13.8) with ESMTP id p1EJx1Fh022926 (version=TLSv1/SSLv3 cipher=AES128-SHA bits=128 verify=FAIL) for <magma@ietf.org>; Mon, 14 Feb 2011 13:59:04 -0600
Received: from EUSAACMS0703.eamcs.ericsson.se ([]) by eusaamw0707.eamcs.ericsson.se ([]) with mapi; Mon, 14 Feb 2011 14:59:02 -0500
From: Kunal Shah <kunal.shah@ericsson.com>
To: "magma@ietf.org" <magma@ietf.org>
Date: Mon, 14 Feb 2011 14:58:55 -0500
Thread-Topic: Question about IGMPv3 state change
Thread-Index: AcvMgZxM5AA0HHReTdmY+c/rHq15Hg==
Message-ID: <4FD1E7CD248BF84F86BD4814EDDDBCC150EA194541@EUSAACMS0703.eamcs.ericsson.se>
Accept-Language: en-US
Content-Language: en-US
acceptlanguage: en-US
Content-Type: multipart/alternative; boundary="_000_4FD1E7CD248BF84F86BD4814EDDDBCC150EA194541EUSAACMS0703e_"
MIME-Version: 1.0
X-Mailman-Approved-At: Mon, 28 Feb 2011 05:05:35 -0800
Subject: [magma] Question about IGMPv3 state change
X-BeenThere: magma@ietf.org
X-Mailman-Version: 2.1.9
Precedence: list
List-Id: Multicast and Anycast Group Membership <magma.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/listinfo/magma>, <mailto:magma-request@ietf.org?subject=unsubscribe>
List-Archive: <http://www.ietf.org/mail-archive/web/magma>
List-Post: <mailto:magma@ietf.org>
List-Help: <mailto:magma-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/magma>, <mailto:magma-request@ietf.org?subject=subscribe>
X-List-Received-Date: Mon, 14 Feb 2011 19:58:41 -0000

Hi all,

I have a question about IGMPv3 state machine. If a group is in EX(X,Y) and a TO_IN(A) is received, the new state according to the RFC is EX (X+A, Y-A). I think this mean remove all the elements of A from Y and add all elements of A to X. This also implies that sources not removed from Y will still end up being added to X. My question is why cant we add only those elemets of A to X which are removed from Y as opposed to adding all the elements of A to X ??

If only the elements that are removed from Y are added to X, the new state would look like EX (X+(Y*A), Y-A).

Am I missing something here??