Subject: [nemo] NEMO DHAAD instead of bit in BAck?

From: [email-masked]
Date: Fri, 14 Nov 2003 13:50:51 +0100

Hi all,

I already talked about NEMO DHAAD with the authors of the basic
support draft and Vijay asked me to post this to the list.

So far according to the basic support draft, MR discovers HA's that
have MR support, by receiving binding acks with with non-zero status
code. This means MR has to cycle between HA's that have no MR support
up to HA's that do have MR support.

Being more specific during the HA discovery phase (DHAAD), could
improve this situation.

I'll attach a text I wrote some time ago, that contains the basic
idea.

Tim.

--- NEMO DHAAD ---
Additions to Dynamic Home Agent Address Discovery (DHAAD)

Since mobile routers need home agents with support for network
mobility, it is of use to extend the existing DHAAD mechanism, to
enable mobile routers to discover home agents supporting mobile
networks.

The modification consists in adding the mobile router home agent bit M
to the ICMP messages for home agent discovery (figures 2.24 and 2.25)
and to the home agent information option (figure 2.26).

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |     Type      |     Code      |            Checksum           |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |          Identifier           |M|          Reserved1          |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

  Figure 2.24: Extended ICMP Home Agent Address Discovery Request
Message

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |     Type      |     Code      |            Checksum           |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |           Identifier          |M|           Reserved1         |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    +                                                               +
    .                                                               .
    .                      Home Agent Addresses                     .
    .                                                               .
    +                                                               +
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

  Figure 2.25: Extended ICMP Home Agent Address Discovery Reply Message

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |     Type      |    Length     |M|         Reserved1           |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |     Home Agent Preference     |      Home Agent Lifetime      |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

  Figure 2.26: Extended Home Agent Information Option Format

Added to the ICMP home agent address discovery request message, the M
bit serves to indicate, that a mobile router is searching for
suitable home agents with mobile router support. If this request is
received by a normal home agent, it will ignore the M bit and send an
ICMP home agent information discovery reply message as specified in
[1], without the M bit set. This reply includes all known home agents
on the home network, regardless of the support for mobile routers.
Otherwise, if the recipient is a mobile router supporting home agent,
it will discover the M bit and send an extended ICMP home agent
address discovery reply message as response (with the M bit set to
one), containing only home agents with support for mobile networks.

The M bit in the home agent information option is used to indicate to
other home agents, whether the sending home agent is capable (and
willing) to act as home agent for mobile routers. A home agent, that
does not support the extension, ignores the M bit and adds the
supplied information to its normal home agent list, while a home agent
that does recognize the M bit, will add an entry to its mobile router
supporting home agent list (this list is kept in addition to the
standart home agent list).

[1] David B. Johnson, Charles E. Perkins and Jari Arkko. Mobility
Support in IPv6. Internet Draft draft-ietf-mobileip-ipv6-21.txt (Work in
Progress),  IETF, February 2003.
--- NEMO DHAAD ---

---

From: Alexandru Petrescu <[email-masked]>
Date: Fri, 14 Nov 2003 14:44:58 +0100

[email-masked] wrote:
> code.

With basic support, I think one could say that a side effect of error
processing is to identify a HA that has MR support.  The error
processing was not designed with the specific goal to "find" the HA with
MR support, but with the goal to try all possible HA's until one replies.

> This means MR has to cycle between HA's that have no MR support up to
>  HA's that do have MR support.

> Being more specific during the HA discovery phase (DHAAD), could 

Absolutely, having a better nemo-oriented DHAAD may help improve the
situation.

Having a DHAAD separate document sounds to me like a good idea.

Alex
GBU

---

From: Alexandru Petrescu <[email-masked]>
Date: Fri, 14 Nov 2003 14:44:58 +0100

Alex
GBU

---

From: Vijay Devarapalli <[email-masked]>
Date: Fri, 14 Nov 2003 17:20:06 -0800

> Having a DHAAD separate document sounds to me like a good idea.

IMO, we should add the M flag to the DHAAD messages because interworking
with MIPv6 home agents is essential for the Nemo Basic support spec. so 
the modifications Tim suggested should be added to the current draft.

Vijay

---

From: Vijay Devarapalli <[email-masked]>
Date: Fri, 14 Nov 2003 17:20:06 -0800

Vijay

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From: Vijay Devarapalli <[email-masked]>
Date: Fri, 14 Nov 2003 19:01:40 -0800

I agree with Tim here. to close this issue I suggest adding
a new section on modifications to Dynamic Home Agent Dicovery
messages to the draft.

a version of the draft with these modifications is at
http://people.nokia.net/vijayd/nemo/nemo_protocol_mod_dhaad.txt
there is a new section 7. please comment.

I also removed Binding Ack status 2.

Vijay

---

From: Vijay Devarapalli <[email-masked]>
Date: Fri, 14 Nov 2003 19:01:40 -0800

Vijay