Subject: RE: IPv6 Addr/Prefix clarification

From: "Michel Py" <[email-masked]>
Date: Fri, 1 Feb 2002 14:29:14 -0800

> Tim Chowm wrote:
> The question is, if a service provider wants to follow the
recommendation
> for a /48 allocation for a connected site, and the provider wants to
> offer static /48's to always-on sites, won't it hit trouble whether it
is
> using a /35 or a /29?   If you say "either there are enough prefixes
to 
> route the currently connected customers or there aren't" then you're
> saying either we will have ISP's out there who can allocate static
/48's
> to sites, or we won't.  It'd be nice if the answer was that we will...
> even if that provider has a million customers.

Tim,

I fail to see your point here. Lots of people will settle with a dynamic
/64. (they won't even pay 5 bucks a month more to get a static one).

Some will want a static /64 because they have thap mp3 server that
their want their buddies to access and also because they want to be able
to telnet to their linux box from the office. Let's say the ISP will
sell
the static /64 prefix for $5/mo more.

Finally, a small number of seriously sick geeks (count me in) that want
their refrigerator to be the only IPv6 device on its very own subnet,
and
of course businesses, will request a static /48. That might cost twice
as
much as a /64, or more.

Given that a /29 is half-a-million /48 prefixes, and with the most
pessimistic figures about the /64 to /48 ratio, a /29 will serve a
million customers with ease.

Michel.

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From: Tim Chown <[email-masked]>
Date: Fri, 1 Feb 2002 23:41:48 +0000 (GMT)

> /64. (they won't even pay 5 bucks a month more to get a static one).

As Pekka pointed out, in draft-iesg-ipv6-addressing-recommendations-03.txt
it states:

"In particular, we recommend:

      - Home network subscribers, connecting through on-demand or
        always-on connections should receive a /48."

OK, so it is a recommendation, and ISP's can, if they choose, offer a
static (or dynamic) /64, at whatever price they choose.

(One comment for the IESG here is that in only one example is static
 allocation specifically mentioned; perhaps this should be considered
 for the document as a whole?)
 
> sell the static /64 prefix for $5/mo more.

I think the market forces will lead to static /64's being available
free of charge.   There will be enough providers who can offer that for
free, that those charging extra will lose business.   

While the recommendation may be a /48 (which may of course be subject to
a charge by some providers) it's questionable at present as to whether
any home networks would use it in the early deployment.
 
> million customers with ease.

You assume that the /29 can be deployed in such a way that there is
100% utilisation.  Is that really the case? (If I consider how a /29
may be used by a national academic research network provider, then 
the regionalisation of the networks mean it won't be, and on top of
that you would presumably be making an address plan with growth in 
mind, e.g. for regional PoPs).  

Tim

---

From: "Tony Hain" <[email-masked]>
Date: Fri, 1 Feb 2002 16:21:06 -0800

> mind, e.g. for regional PoPs).

And you are arguing that the national academic research network provider
needs more than 10 bits to serve its customers. While this is probably
true for the IPv4 space since the customers acquired their allocations
independently from the provider and are therefore disjoint, consider
that the process of moving allows the provider to structure the
boundaries according to density. If your argument is that this does not
align perfectly with current topology, how much of that could/would be
fixed if address management required it? In other words, how much of
current topology is there because it can be as opposed to it needs to
be? Granted there will be cases where topology can't be perfectly
aligned to achieve 100% allocation efficiency, but I don't see anyone
demanding 100%. Have you tried to get an allocation large enough to
cover the network by allocating /48's to the current customers? If so
what was the response?

Tony

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From: "Murugan KAT" <[email-masked]>
Date: Sat, 2 Feb 2002 15:18:52 +0530

Hi,

As per ND specification the Neighbor Advertisement message contains  "O"
Flag (OverRide flag).
What is the purpose of this flag. Or when the nodes is supposed  set this
Flag. Or when the nodes are not supposed to set this flag.

I suppose whenever the receiver finds a difference between the sent link
address and the address what it has in its ND cache it can modify the value.

Why is this extra bit...?

Thanks,
KAT

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From: Tim Chown <[email-masked]>
Date: Sat, 2 Feb 2002 16:58:34 +0000 (GMT)

Good points Tony - I guess we will have to wait until a large provider
puts in a significant request, which may be some time yet.   There are
certainly more homes than universities+colleges (though of course most
universities offer dialup to stduent homes :-)

Tim