Re: [v6ops] draft-ietf-v6ops-64share

Mark Smith <markzzzsmith@yahoo.com.au> Sun, 20 January 2013 11:31 UTC

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Date: Sun, 20 Jan 2013 03:31:31 -0800
From: Mark Smith <markzzzsmith@yahoo.com.au>
To: Cameron Byrne <cb.list6@gmail.com>
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Cc: v6ops v6ops WG <v6ops@ietf.org>
Subject: Re: [v6ops] draft-ietf-v6ops-64share
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Hi,


>________________________________
> From: Cameron Byrne <cb.list6@gmail.com>
>To: v6ops@ietf.org 
>Sent: Sunday, 20 January 2013 12:23 PM
>Subject: [v6ops] draft-ietf-v6ops-64share
> 
>
>Hi,
>I posted this update as a WG draft
>http://tools.ietf.org/html/draft-ietf-v6ops-64share-00
>Please take the time to review this update and share your feedback.  I hoping that a clearly defined scope, clear need for this work,  as well running code will make it easy to advance. I am now aware of 3 implementations that approximately use this method (ios6, an LTE mifi router, and Dan Drown's Android submission)

Regarding this text, 

 9.  Since the address 2001:db8:ac10:f002:1234:4567:0:9/128 is the
       only instance of the assigned /64 on the 3GPP interface, there is
       no chance of an address conflict on that interface.  On the LAN
       interface, there is no chance of address conflict since the



Byrne                    Expires June 17, 2013                  [Page 4]
 
V6OPS Working Group   draft-ietf-v6ops-64share-00      December 14, 2012


       address is defended using Duplicate Address Detection (DAD).

I'd suggest adding something like "address is defended using Duplicate Address Detection (DAD), as the LAN interface is also assigned the address in use on the 3GPP interface."

I struggled a bit with working out what was going on until it became clear that the 3GPP and LAN interfaces are using the same global unicast address.

I also think it would be better to be clearer about the type of IPv6 address and also cover that their may be multiple IPv6 addresses, such as privacy addresses on the 3GPP/LAN interface. For example, in 3. Method for Sharing the 3GPP Interface /64 to the Tethered LAN, 

"The UE checks to make sure the 3GPP interfaces is active and has
       an IPv6 address.  If the interface does not have an IPv6 address,
       an attempt will be made to acquire one, or else the procedure
       will terminate."

Strictly, the 3GPP interface always has an IPv6 address because it always has a link local address, so the above would be better if it clarified that the type of address to check for is a global IPv6 address.

I'll have to do some digging, however I'm wondering if the sockets API might have an assumption that an individual IPv6 address is only assigned to a single interface. 

Actually, reviewing the IPv6 Addressing Model in RFC4291, it says, "An IPv6 unicast address refers to a single interface." 

Was a translational bridge model considered? That is, the 3GPP and LAN interfaces are part of a bridge instance, and a single bridge virtual layer 2/3 interface is assigned the UE's global unicast address within the /64, with a /64 prefix length. Enabling or disabling tethering would be a simple matter of administratively enabling/disabling the LAN interface.

Regards,
Mark.