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: "Pascal Thubert (pthubert)" <[email-masked]>
Date: Mon, 17 Nov 2003 07:33:28 -0000

All:

Just 2 comments:

1) I agree with the idea. But DHAAD is an option and I believe HA still
must echo the R bit.
2) Since this is about the same functionality as the 'R' bit, why not
naming it 'R' as well in  DHAAD?

Pascal

> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]] On Behalf Of
Vijay Devarapalli
> Sent: samedi 15 novembre 2003 04:02
> To: [email-masked]
> Cc: [email-masked]
> Subject: Re: [nemo] NEMO DHAAD instead of bit in BAck?
> 
> 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
> 
> [email-masked] wrote:
> > Hi all,
> >
> >     |
|
> >     +
+
> >     .
.
> >     .                      Home Agent Addresses
.
> >     .
.
> >     +
+
> >     |
|

---

From: "Pascal Thubert (pthubert)" <[email-masked]>
Date: Tue, 18 Nov 2003 10:13:18 -0000

> the only other way (apart from DHAAD) a Mobile Router acquires Home
> Agent information is through manual configuration. so why do we need
> a flag in the Binding Ack? the Mobile Router should not attempt
> registration with a Home Agent that does not support Mobile Routers.
> 

I'd put it there for consistency, and to check for config errors. If you
look at it, many error codes and operations we have actually detect
invalid config and report that to the admin. 

Eg: DAD on the Home Link. Since the Home Address is configured on the
MR, it's as 'good' as any fixed address on any fixed node. In other
words it's not autoconfigured. We're looking for an erroneous config (or
change of config). This test is not really costly to implement, and then
you're 100% sure that the 0 in the binding ack means OK for a basic Nemo
registration.

I'd say it 'nice to have' + 

Pascal