RE: on the point of mobility & multihoming

["Kanchei Loa" <loa@ieee.org>]

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> > In my opinion, you just hit an important issue of multi6  architecture,
which
> > this WG is supposed to work on first. If we take Dave Croker's scenario
> > (suggested by Geoff Huston) and generalize it, the problem space is the
same
> > as depicted in Geoff's slide (page 3) of "An Architectural View of
Multi6
> > proposals" except that the solid line (wired fixed connection) between
the
> > exit route and ISP is replace by dotted lines (wireless dynamic
> > connections).
> >
> > In this architecture, mobility is just a special case of "dynamic ad hoc
> > multihoming", which has timing restriction on updates and discovery.
(You
> > don't have to call it mobility if that is more IETF political correct).
In
> > Dave's scenario, from IP network's point of view, there is no difference
> > between a laptop sitting on a bench switching among ISPs because of
> > interference and a laptop sitting in a car that is moving back and forth
> > among ISPs.
> >
> > Should multi6 architecture encompass wireless connections between the
exit
> > router and IPS? Or, Dave Croker's scenario is too far away in the future
to
> > be included in multi6 architecture, which has been focusing on
traditional
> > IP multihoming with fixed connections only? It is up to the WG to
decide.
> > But the architecture document should spell out the rational choice. The
> > "uncomfortable" wireless issues won't goes away if we just choose to
ignore
> > them or call it something else.

> Brian E Carpenter wrote:

> Actually, it isn't up to the WG to decide. We are chartered to deal with
> _site multihoming_. That is definitely a different problem space from host
> multihoming in the form of ISP roaming.
>

Now I know where the problem is. In Dave's scenario, the Personal Area
Network (PAN) surrounding him in the park is the "site", which consists of
laptop, PDA, game console, headphone, MP3 player, digital camera, and dual
mode handset (UMTS and 802.11b). The exit routers are laptop with 802.11g,
and handset with UMTS and 802.11b. Later, Dave's friend Geoff, sitting next
him on the same bench, join him to work on multi6 drafts. So, Dave's PAN and
Geoff's PAN are forming a new "site" with 4 exit routers (Dave's
laptop(802.11g), handset (UMTS, 802.11b), and Geoff's laptop (802.11a) and
handset  (WCDMA and 802.11g). This new "site" should be able to take full
advantage of 4 redundant wireless ISP connections, even the interference
might knock out one or two ISP from time to time.

If you consider above expanded scenario of a "site multioming" is too
"non-traditional", then let's try a traditional one. An branch office in
downtown has 4 exit routers to 5 ISP. Router a connects to ISP A through
wired cable modem (cost $55 per month) as primary Internet link. Router b
connects to ISP B through 802.16 wireless link (cost $60 per month) on the
roof top dish as backup Internet link. Router c connects to  ISP C through
802.11a corporate backbone (cost $100 per month) in adjacent building as
corporate resources access and backup Internet link. Router d connects to
local community networks (cost $50 per month), which are served by two
802.11b providers ISP Da and ISP Db. This branch office is setup to support
their business in local community. So, router d is as important as other
exit routers. When the weather is bad or other RF factors, traffic driving
by disconnects constantly changes branch office's preferred access point.

My point is that wireless exit connection to ISP is not an invisible wired
connection. It injects "ad hoc" factor into both traditional and
non-traditional site multihoming. That is definitely NOT a different problem
space from _site multihoming_ we are chartered to deal with unless you
exclude wireless in the charter. The host multihoming with "ISP roaming" is
just a special case of site multihoming where exit router and host are on
the same machine.

> (Also, I don't see what wireless has to do with it. If I sit in  front of
two
> Ethernet plugs leading to two ISPs, and move my connector from
> one to the other every two minutes, the problem is the same - but it is
*not* site
> multihoming.)
>
>    Brian

The "wireless" make  "ad hoc site multihoming" a practical engineering
problem for any Internet community who follows IETF's lead. Your example of
plug-and-unplug Ethernet belongs to academic research not IETF.  In above
scenario if all connection to ISPs are wired links, it won't make any sense
to create a multihoming protocol by this WG to deal with the situation that
a administrator plug-and-unplug Ethernet connector of exit routers at will
every two minutes. However, "wireless" causes the same plug-and-unplug
scenario a practical engineering problem we have to deal with. My opinion,
for what it's worth, is that  the arguments of ad hoc multihoming should be
thrown out if the consensus is that wireless is not in WG's equation.

In 1992 Dave Clark said "We reject kings, presidents, and voting. We believe
in rough consensus and running code". In my opinion, majority of the IPv6
running codes are going to be deployed on wireless networks.

-----------------
Kanchei Loa
loa@ieee.org