Re: [sig-policy] prop-087: IPv6 address allocation fordeployment purpose
Hi Philip,
Thank you for your reply!
Just a clarifying question, you mean to use separate 6rd domain
for each IPv4 address prefixes?
# Again, I'm so sorry if I misunderstand your comment:-)
Yours Sincerely,
--
Tomohiro Fujisaki
From: Philip Smith <pfs at cisco dot com>
Subject: Re: [sig-policy] prop-087: IPv6 address allocation fordeployment purposes
Date: Tue, 17 Aug 2010 21:03:37 +1000
| > I'm sorry if I misunderstand your comment, but the problem is not
| > number of addresses but prefixes of the addresses.
| >
| > If ISPs use a same address prefix for all users, it is possible to
| > shorten the encoded prefix. I'm not sure how many ISPs request and get
| > additional address blocks under same IPv4 address prefixes, but I
| > suppose there are not so many ISPs that use a single prefix for all
| > of their customers.
|
| Okay, so the concern is about the situation where an ISP (I'll use
| private address space for my example) might use 172.16.0.0/16 for one
| group of 6rd customers. And then are allocated 172.17.0.0/16 for the
| next group. So they can't use the last 16-bits of the IPv4 address for
| 6rd because the IPv6 addresses would end up being the same in each pool.
| Can't they just use the last 17-bits then - or some other way of
| identifying the difference?
|
| If each 6rd customer is receiving an IPv6 /48 this way, each IPv4 /16
| allows a total of 65536 addresses. And presumably a total of 65536
| customers.
|
| If the ISP has two IPv4 /16s in use for their existing customers, that'd
| be 131072 IPv4 addresses in total - and 131072 /48s in IPv6 is the same
| as a /31. And an IPv6 /31 would be able to encode the last 17-bits of
| the IPv4 address for 6rd as I mentioned above.
|
| And if customers are getting less than an IPv6 /48 by way of 6rd, then
| there are more bits available to encode the IPv4 address in.
|
| As you can see, I'm still having trouble working out what the problem
| is. There must be some other scenario...?
|
| Thanks!
|
| philip
| --
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