Re: Comments on draft-wbeebee-ipv6-cpe-router-01.txt

[Iljitsch van Beijnum <iljitsch@muada.com>]

(Sorry about the large number of messages...)

On 17 jul 2008, at 23:10, Stark, Barbara wrote:

> Yes, the WAN interface absolutely *must* have a global IP address that
> it uses for sending and receiving IP messages, as far as I'm  
> concerned.

Huh? Didn't you say the exact opposite earlier?

There three questions:

1. Should the CPE have a global address that it can use to send  
outgoing packets on the WAN interface

2. Should it be an option for the ISP to not provide address  
configuration over the WAN link (obviously they must do DHCPv6 PD)

3. If both 1 and 2, then what? Options:
3a: use a loopback interface and take a subnet from the PD prefix  
(even if it's only a /128, but that still makes a /64 unusable for  
anything else)
3b: use an address from a LAN interface (issue with usability of this  
address if LAN interface is down)
3c: take a subnet from the PD prefix (even if it's only a /128) and  
use it on the WAN interface

Note that 1 MUST be answered with YES if there is the possibility that  
a LAN interface has a smaller MTU than the WAN interface in order to  
get PMTUD to work, and SHOULD be yes for the purpose of other ICMPv6  
messages.

3b and 3c have the issue that they eat up address space, so if the ISP  
only provides a /64 you're in trouble. 3c also has the issue that it  
doesn't make much sense because the ISP doesn't know the address is on- 
link.

3b seems to make sense.