Subject: RE: DAD in node requirements draft

From: "Laurent Montini (lmontini)" <[email-masked]>
Date: Thu, 3 Apr 2003 20:31:08 +0200

In 3GPP, when setting an IPv6 PDP Type (whatever 2.5G or 3G), the GGSN
first provides the link-local address to the MT.
The GGSN will then send/forward an unique /64 prefix given for that PDP
Context (static, stateful or stateless allocation).

From the link-local address the MT will strip the unique IID.
The IID will be used for link-local address and then avoids DAD (and any
overhead traffic over air interface).
The GGSN is managing all the IID given to each IPv6 PDP Context that
GGSN will setup. 
The IID may be used with the /64 global prefix if the UE is not able to
create is own IID.
Thus the global address is built with the /64 prefix and with either the
IID given by the GGSN or any other IID the TE wants (e.g. TE MAC
address). The TE can also use RFC3041 addresses.

TS 23.060 and 29.061 are the 2 main documents to look at (for Rel99/3,
Rel4 and Rel5).

.lm

-----Original Message-----
From: Ole Troan [mailto:[email-masked]] 
Sent: 25 March 2003 20:29
To: Peter Barany
Cc: Mika Liljeberg; [email-masked]; [email-masked];
[email-masked]
Subject: Re: DAD in node requirements draft

[...]

> During 3GPP (UMTS) work on PDP context activation, it was agreed to 
> make the /64 prefix unique per primary (and associated secondary) PDP 
> contexts so that DAD would not have to be performed (particularly 
> since privacy addresses are specified for use in 3GPP). See RFC 3314 
> and, I believe, 3G TS 23.060 (and/or maybe another document in the 
> 3GPP 24 series).
>
> 3GPP2 (cdma2000) uses PPP and not a PDP context. In IS-835-B it is 
> stated that the /64 prefix(es) must be unique to that PPP link ... 
> again avoiding DAD when privacy addresses are used.

requiring that a /64 is unique on a link does not avoid DAD. doesn't the
3GPP specs restrict one end of the link to not use any addresses from
the prefix, if so DAD is not needed.

> Since the IETF IPv6 WG is in the process of updating the IPv6 PPP RFC 
> 2472 (more specifically IPV6CP), my question is: What changes are 
> being planned to that RFC? Do any of these changes pertain to the 
> granularity/uniqueness of the /64 prefix? Thanks.

the only thing I can see requiring an update is that the value of
DupAddrDetectTransmits should default to 1 not 0.

you can turn off DAD in your environment if you know you don't need it.

/ot

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