Subject: [SAM] Mobility in SAM problem.

From: Shiv <[email-masked]>
Date: Mon, 25 Sep 2006 20:03:25 +0530

Dear Buford,

I work in the multicast area. I was reading the sam problem statement 
draft (draft-irtf-sam-problem-statement-00.txt).
I think you have succinctly summarised the problem.  I have some 
comments to the draft.
Please let me know if these are relevant.

we see that there are 2 mobility scenarios associated with multicast:

If the mobileip is the mobility solution of choice and the overlay is 
transparent to this: (example scenarios with native multicast is given 
below):

Section 4 Mobility:

1 - If foreign network has multicast router, mobile node can join the 
multicast group through that multicast router.
        a - If mobile node is coloacated then it uses coa as the source 
address of control mesages, otherwise Mobile Node MAY use its home 
address(But if mobile node want to send packets to multicast group in 
foreign network, source ip of packets should be coloacated ip).
        b - causes  a leave-join sequence.
        c - If router is not a part of  multicast SPT, joining in 
foreign network causes delay.

2 - Home agent tunnels packets to/from mobile node.
        a - mobile node used home address for multicast control messages.
        b - No need to join/leave during handoff.
        c - may result in duplicate packets if MN is not coloacated. 
Consider two mobile nodes belonging to different network which are in 
the same foreign network. Both subscribe to same group, then packets of 
same multicast group are coming from two networks. Possible solutions to 
this are:
        1 - Applications in mobile node will take care of duplicate packets.
        2 - Multicast packets will be  sent to mobile node as unicast 
packets(Mobile IPv4 uses this solution).
        But in case of coloacated MN multicast packets are directly 
tunneled to MN.

It would be good to add both these scenarios in the problem statement draft.

Need to consider  the movement scenario between heterogenous multicast 
networks (say, from native multicast region to overlay(OL/ALM) multicast 
region or viceversa).
Yet another problem is that some of the solutions to the packet loss 
advocates buffering packets at HA:
This may result in duplicate packets. If foreign network already has 
mobile node subscribed to same group, when handoff happens these 
buffered packets are duplicate packets to that mobile node.
        a - potential solutions might be to transfer the buffered 
packets to mobile node as unicast packets.
        b - let the applications handle duplicate detection.
Instead of buffering at HA, it is better to buffer at old router(Access 
router/FA).

how to handle multicast service advertisements?
        multicast advertisements are also multicast packets with well known
multicast group ip and port number. Should these multicast service 
packets be
tunneled to mobile nodes which are in foreign network? If not how mobile 
nodes
will come to know about services provided by the home network.

5 Security:
        Will sam specify the interworking between the security 
mechanisms of the heterogenous mc mechanisms?

Thanks,
Shivanand Kadadi.

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SAM mailing list
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https://www1.ietf.org/mailman/listinfo/sam

---

From: "John Buford" <[email-masked]>
Date: Mon, 25 Sep 2006 11:05:09 -0400

Shiv,
Thanks for your comments on the Problem Statement.

The two IP Multicast mobility scenarios you
provide would be a good addition to the mobility
section.

Your other points about heterogeneous movement,
buffering, and multicast service advertisements
are also good ones.

Regarding the security question, interoperability
of existing mc security mechanisms is in scope.

Would you be able to edit section 4 of the
draft to incorporate your scenarios and issues?
If so, send me the revised text you propose and
we can issue a new draft for comment by the mailing
list.

John

-----Original Message-----
From: Shiv [mailto:[email-masked]]
Sent: Monday, September 25, 2006 10:33 AM
To: [email-masked]
Cc: Gangaram Vihang-A20783; Ram O V Vishnu-A14676
Subject: [SAM] Mobility in SAM problem.

Dear Buford,

Section 4 Mobility:

5 Security:

Thanks,
Shivanand Kadadi.

---

From: Jun Lei <[email-masked]>
Date: Tue, 26 Sep 2006 12:21:21 +0200

Dear all:
      It's so great to hear some voices from SAM. Overaly technologies 
could be well used in Mobility solutions and several researches have 
been focusing on this topic.

  John:  Regarding the draft, I am just wondering whether the following 
issue fall into the problem statement as well?

- In Section 2.2, you've mentioned "regional transitions". How about the 
transience of group members? Since application level multicast systems 
are mainly dependent on the group members to maintain such an overlay 
network.
    - If we need to consider the transience of nodes, then two 
situations are required: graceful leave & unexpected leave
      a. graceful leave: need to consider tree re-construction
      b. ungraceful leave: failure detection + failure recovery

By the way, I am currently focusing on above topic. I will try to give 
an brief overview on this topic by next week.

Best Regards

Jun

-- 
Jun Lei
PhD Student

Address:
Georg-August-Universitaet Goettingen
Institut fuer Informatik
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Email: [email-masked]