Daryl,
The problem described in the draft is that CPEs use 1918 space *and that
many of them can't deal with the fact that there might be addresses on
the outside interface that are the same as on the inside interface*. The
claim was made by Randy, among others, that only 192.168/16 space was
used by such unintelligent CPEs. I believe I have seen the claim that
10/8 space is also used in unintelligent equipment that can't deal with
identical addresses inside and outside. Is there reason to believe that
within the ISP network / back-office etc. that there is equipment that
can't deal with 17.16/12 space being on both the inside and outside? I
haven't seen anyone make that specific claim.
If we know that 172.16/12 used both inside and outside will break a
significant amount of sites that CGNs will be used with, we can ignore
this argument. But if not, then let's rewrite the document to say that
CGNs should use 172.16/12 and that any device that wants to use
172.16/12 needs the ability to deal with identical addresses on the
inside and the outside interface. Of course, all equipment should have
always been able to deal with identical addresses inside and outside for
all 1918 addresses anyway. But if we think the impact of using 172.16/12
for this purpose will cause minimal harm, then there's no compelling
reason to allocate new space for this purpose.
pr
On 11/30/11 3:04 PM, Daryl Tanner wrote:
It's not just about the CPE devices and customer LANs.
Address conflicts are also going to happen within the ISP network /
back-office etc. 172.16.0.0/12 <http://172.16.0.0/12> is used there.
Daryl
On 30 November 2011 20:52, Brian E Carpenter
<brian(_dot_)e(_dot_)carpenter(_at_)gmail(_dot_)com <mailto:brian(_dot_)e(_dot_)carpenter(_at_)gmail(_dot_)com>> wrote:
On 2011-12-01 09:28, Chris Grundemann wrote:
...
> It is more conservative to share a common pool.
It suddenly occurs to me that I don't recall any serious analysis
of using 172.16.0.0/12 <http://172.16.0.0/12> for this. It is a
large chunk of space
(a million addresses) and as far as I know it is not used by default
in any common CPE devices, which tend to use the other RFC 1918
blocks.
I realise that ISPs with more than a million customers would have to
re-use this space, whereas a /10 would only bring this problem
above 4M
customers, but at that scale there would be multiple CGN monsters
anyway.
Sorry to bring this up on the eve of the telechat.
--
Pete Resnick<http://www.qualcomm.com/~presnick/>
Qualcomm Incorporated - Direct phone: (858)651-4478, Fax: (858)651-1102
_______________________________________________
Ietf mailing list
Ietf(_at_)ietf(_dot_)org
https://www.ietf.org/mailman/listinfo/ietf