[16NG] Resolutions to issues raised during 2nd WGLC of I-D draft-ietf-16ng-ipv6-over-ipv6cs-04 [1]

Issues raised during the LC of I-D:

[Junghoon Jee]
1. [Page 8]
For transmission of IPv6 packets via the IP specific part of the
Packet CS of 802.16, the IPv6 layer interfaces with the 802.6 MAC
directly.  

s/802.6/802.16

Raj> Done.

2. 13.2.  Informative References

  [FRD]      Choi, JH., Shin, DongYun., and W. Haddad, "Fast Router
              Discovery with L2 support", August 2006, <http://
              www.ietf.org/internet-drafts/draft-ietf-dna-frd-02.txt>gt;.

 [RFC4135]  Choi, JH. and G. Daley, "Goals of Detecting Network
              Attachment in IPv6", RFC 4135, August 2005,
              <ftp://ftp.isi.edu/in-notes/rfc4135>.

Raj> Based on feedback and earlier discussion, we decided to not reference
the DNA work. However the reference section has not been revised. I
have deleted both these references from the IR section.

[Alex Petrescu]

3. draft says:
> The AdvDefaultLifetime in the router advertisement MUST be either
> zero or between MaxRtrAdvInterval and 43200 seconds.  The default
> value is 2 * MaxRtrAdvInterval.

This formulation is ambiguous.  I'd prefer using 'MUST' followed by a
single sentence, not by an 'or'.

If the Router Lifetime is 0 then the BS or AR is not a Default Router.
Or I don't see a deployment scenario where the BS/AR are not default
routers for the SS.

Raj> If you look at the AdvDefaultLifetime specification in 2461bis,
its is specified the same way (MUST be either zero or between
MaxRtrAdvInterval and 9000 seconds).
So I think the sentence is acceptable as written.
There are situations when you would want to configure a RTR that you
are adding to the network with Lifetime=0. For hosts that are being
served by an AR, the lifetime is obviously non-zero. I think this is
pretty well understood.

4. draft:
> The MaxRtrAdvInterval value specified in this document over-rides the
>  recommendation in RFC2461 [RFC2461].  The MaxRtrAdvInterval MUST be
>  no less than 4 seconds and no greater than 21600 seconds.  Thee
> default value for MaxRtrAdvInterval is 10800 seconds.

[nit: Thee]

Raj> Fixed.

Actually it only over-rides the upper limit and the default value (2461
says 1800s vs draft 21600s, and 600s vs draft 10800s respectively).
This draft does not override 2461's lower limit of 4s.

Raj> True. Practically speaking you would not want to send periodic
RAs over an air-interface. I had co-authored an I-D earlier where I
had proposed that it should be possible to configure an RA to not send
periodic RAs at all
(draft-madanapalli-ipv6-periodic-rtr-advts-00.txt). However because of
backward compatibility issues this is not possible. The next best
thing is to have a large gap (time) between periodic RAs. Hence the
lower limit of 4s is just fine.

It means that an IPv6-over-IPv6CS handover would take a long 4s in the
worst case; which is too long.  But Mobile IPv6 3775 allows for
MaxRtrAdvInterval as low as 0.03s.  How does this draft position with
respect to 3775?  Can this draft be over-ridden by 3775 in addition to
over-riding 2461?

Raj> Movement detection as specified in RFC3775 is based on RAs. Hence
it makes sense to have a small value in that case. However movement
detection in 802.16 is handled by the lower layer and there is no
reason for the host to depend on RAs to detect if it has moved across
ARs. Hence there is no reason for any change w.r.t 3775 and I do not
see RFC3775 over-riding the values specified here.

-Raj

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