Subject: [nemo] Short comment on draft-thubert-nemo-basic-usages-00

From: Alexandru Petrescu <[email-masked]>
Date: Thu, 06 Nov 2003 23:01:18 +0100

Hi to authors of draft-thubert-nemo-basic-usages-00.txt

I think the words "Examples of basic nemo usages" in the title are
claiming more than the draft actually describes.  The draft mainly
describes the architecture of the home network, or NEMO is about the
home network _and_ the mobile network.  I would suggest a better title
to say "Examples of home networks for NEMO".

> Home Link: The link attached to the interface at the Home Agent on 
> which the Home Prefix is configured. The interface can be a virtual 
> interface, in which case the Home Link is a virtual Home Link.

...and in which case there is no need for Proxy ND (an essential feature
of MIPv6), or there is a need for a Virtual Proxy ND, to be figured out.

> With  Mobile IPv6, the Home Network is generally a physical network 
> interconnecting the Home Agents,

It would sound better IMHO to say that a MIPv6 Home Network is a
physical _link_ (instead of a physical network).  Network sounds to me
like yes being physical, but having routers connecting links, or the
MIPv6 home network linking the HA's together has no routers in between.

Finally, I think that the draft misses an important opportunity to first
describe a simple MIPv6 home network that accomodates NEMO mobile
networks (implicit and explicit network modes), which is the following:

              |
    route     v  /48

              HA
              | /52
   --+-----+--+- . -+- . -+--
     |     |        |     |
     MR1   MR2      MRi   MRN
     /56   /56      /56   /56

In this home network the prefixes are aggregated.

If one wonders how can a link be assigned a shorter-than-64 prefix and
still have the stateless autoconfiguration work then one needs to
consider that the length of the prefixlen advertised by RA on that link
is not necessarily the prefix len in the routing tables of routers
pointing to that link.  In other words, HA's rt entry towards MR1 would
be len 56 but MR1 would send RA's with prefix len 64 inside on its first
link such that its first-level LFN's could configure IPv6 addresses with
their Ethernet-like cards.

Note that RFC2462 does not relate the prefix lens in the RA to the 
prefix lens existing in routing tables.  That doc acknowledges that most 
people use EUI-64 and asks that:
> It is the responsibility of the system administrator to insure that 
> the lengths of prefixes contained in Router Advertisements are 
> consistent with the length of interface identifiers for that link 
> type.

So, I would suggest to add a simple description of this simple home
network and say what are its problems.

Alex
GBU

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From: Vijay Devarapalli <[email-masked]>
Date: Thu, 06 Nov 2003 14:27:11 -0800

hi Alex,

>              HA

the draft currently has

                  HA
                  | /56                       Aggreg /56
          --+-----+--+- . -+- . -+--
            |     |        |     |
            MR1   MR2      MRi   MRN
         ------  ------  ------ ------
            /64   /64     /64   /64           Aggreg|i /64  0 < i <= N

arent both same? only the prefix lengths are different.

Vijay

---

From: Vijay Devarapalli <[email-masked]>
Date: Thu, 06 Nov 2003 14:27:11 -0800

hi Alex,

the draft currently has

                  HA
                  | /56                       Aggreg /56

Vijay

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From: Alexandru Petrescu <[email-masked]>
Date: Thu, 06 Nov 2003 23:42:36 +0100

>                  | /56                       Aggreg /56

Right, looks to me like being the same; I had this doubt: having /64 
below the MR suggests to me that there can not be another FR below MR 
that could support aggregation too (because can't reasonably have a /66 
prefix below that FR and still send RA's with prefix len /64).

Second, I find that, if we are on the same wavelength with the above 
descriptions, then they should appear at the beginning of the document 
(_before_ the extended, since it is the most basic home network).

Third, section 5 that describes the above configuration says:
>    Note: a Mobile Router coming Home sees overlapping prefixes between
>    the ingress and the egress interface and some specific support may be
>    needed.

I do not see any specific support that may be needed.

>    Thus, the Home Agent MUST intercept all the packets to the MNNs on
>    the registered prefixes. In order to do so, the Home Agent MAY
>    perform ND proxying for all addresses in all registered Mobile
>    Network Prefixes, and protect the Mobile Network Prefix space from
>    autoconfiguration by uncontrolled visitors on the Home Link.

This paragraph I truly do not understand.  In the picture of the home 
network that I did above there is no need for HA to perform ND proxying 
for all addresses in all registered Mobile Network Prefixes.  HA does 
proxy ND only for the home addresses of the MR's.

I do not understand also how does HA protect the MNP space from 
autoconfiguration by uncontrolled visitors on the Home Link.  Is this a
PANA or SEND or AAA related method?

Alex

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From: Alexandru Petrescu <[email-masked]>
Date: Thu, 06 Nov 2003 23:42:36 +0100

Alex