Re: [dhcwg] I-D Action: draft-ietf-dhc-rfc3315bis-09.txt - questions about Solicit Prefix Delegation

Ted Lemon <> Tue, 18 July 2017 08:54 UTC

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From: Ted Lemon <>
Date: Tue, 18 Jul 2017 10:53:55 +0200
Message-ID: <>
To: Vízdal Aleš <>
Cc: Alexandre Petrescu <>, dhcwg <>, "Bernie Volz (volz)" <>
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Subject: Re: [dhcwg] I-D Action: draft-ietf-dhc-rfc3315bis-09.txt - questions about Solicit Prefix Delegation
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I think the issue here is not that it's not clear what should be happening,
but rather that Alexendre has observed bad behavior in the wild.   So it is
worth getting to the bottom of the bad behavior.   I have no argument with
that.   I'm just saying that once we have characterized the bad behavior,
if it is a bug in the implementation, that should be fixed, and if it were
a bug in the tunneling specification (which you are saying it is not) we
would want to fix that.

But what we definitely would not want to do is require behavior that's
contrary to the internet architecture in 3315bis in order to paper over a
bug that isn't a bug in DHCP.

On Tue, Jul 18, 2017 at 10:40 AM, Vízdal Aleš <>

> I believe it is not a bug / problem, since the IP-link between the UE
> (handset) in the Mobile Network and the first L3 hop (GGSN/PGW or Mobile
> Core if you will) is a virtual-link. There are intermediate nodes between
> the UE and GGSN, but these are not touching the UE originated packets nor
> do any TTL / hop-limit changes since all IP forwarding is done based on GTP
> (or IPSec, since in some networks this traffic is secured by IPSec)
> The GGSN/PGW usually acts as a DHCP server or a relay, so a DHCP packet
> with a TTL=1 / hop-limit=1 will reach it.
> Does it clarify?
> Ales
> *From:* Ted Lemon []
> *Sent:* Tuesday, July 18, 2017 10:17 AM
> *To:* Vízdal Aleš <>
> *Cc:* Alexandre Petrescu <>; dhcwg <
>>; Bernie Volz (volz) <>
> *Subject:* Re: [dhcwg] I-D Action: draft-ietf-dhc-rfc3315bis-09.txt -
> questions about Solicit Prefix Delegation
> I believe what Alexandre was proposing was not that we re-cast 3gpp specs
> as RFCs, but rather that we add text to 3315bis that explicitly says what
> hop limit to use, and that the hop-limit should be what I would describe as
> "incorrect."​   I realize that this is a somewhat judgmental way of
> describing it, but I don't know a different way.   If in fact the 3GPP
> architecture requires this, that's a bug, and it's not clear to me that
> RFC3315 is the right place to address that bug.
> But I'd really like for us to try to figure out whether this is in fact a
> bug, or whether it's just an artifact of the way that the ISC DHCP client
> is transmitting DHCP packets, which can be addressed by fixing that, rather
> than by updating RFC3315 to require behavior that is effectively a
> violation of the internet architecture.
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