RE: v6-v4 transition scenarios, take 2

["Templin, Fred L" <Fred.L.Templin@boeing.com>]

>-----Original Message-----
>From: Nathan Ward [mailto:v6ops@daork.net] 
>Sent: Monday, August 04, 2008 8:49 AM
>To: Templin, Fred L
>Cc: v6ops WG
>Subject: Re: v6-v4 transition scenarios, take 2
>
>On 5/08/2008, at 3:26 AM, Templin, Fred L wrote:
>
>> The idea is that the cusomter NAT becomes an IPv6 router.
>> It does ISATAP on the customer-facing side and some other
>> IPv6 capability on the SP-facing side. That could be a
>> native IPv6 service, 6to4, or it could even be another
>> ISATAP domain that is distinct and separate from the
>> customer's ISATAP domain.
>
>Right, your assumption is that the customer NAT device changes - my  
>assumption is that the customer NAT device stays the same, which is  
>where we're differing here.

The NAT box would be a natural location for the ISATAP
router function, and I don't think entirely out of
the question for change given the benefit. But, I'm not
entirely sure that it is the only location; I will have
to study more on what is meant by "Internet Connection
Sharing" on Windows, for example. 

>I agree with you - ISATAP is absolutely appropriate inside customer  
>networks that have IPv4-only internal routing equipment, but have an  
>IPv6 capable NAT box and hosts, and at least a single IPv6 /64.
>
>It is not clear to me how ISATAP can be used between the ISP and the  
>customer CPE, should that CPE support ISATAP. My understanding 
>is that  
>ISATAP gives hosts single addresses, not a /64 as would be 
>required by  
>a second ISATAP domain, or by a subnet behind the CPE.

ISATAP is about *hosts* receiving a single IPv6 address
with an embedded IPv4 address. VET is about *routers*
receiving IPv6 prefixes for sub-delegation on their
site-internal interfaces:

http://tools.ietf.org/html/draft-templin-autoconf-dhcp-14

The ISP/CPE routing region would use VET, which can be
thought of as ISATAPv2.

Fred
fred.l.templin@boeing.com

>> If the SP can't provide an IPv6 service of any kind,
>> then there is always the possibility to use Teredo.
>
>Yes - however Teredo is selected after 6to4 on Windows. There are two  
>ways a customer might use, for example, an ADSL service:
>1) Have a NAT box. Teredo will work fine.
>2) Plug their Windows PC in to an ADSL device that lets the ISP  
>assigned IPv4 address exist on the PC ("modem"). The PC tries 
>to bring  
>up 6to4, as in my recommendation RFC1918 addressing is not 
>used by the  
>ISP for customer assignments to avoid address conflicts. Teredo will  
>not come up, as a Windows host will assume 6to4 is functioning.
>
>The two ways to avoid (2) being a problem are in my initial post in  
>this thread, under "There are two work-arounds for this that I can  
>see, and I think it is a good idea to do both.".
>
>--
>Nathan Ward
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