Re: [dhcwg] [EXTERNAL] Question to DHCPv6 Relay Implementors regarding draft-ietf-dhc-dhcpv6-pd-relay-requirements

otroan@employees.org Wed, 07 October 2020 14:39 UTC

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From: otroan@employees.org
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Date: Wed, 7 Oct 2020 16:39:05 +0200
Cc: "ianfarrer@gmx.com" <ianfarrer@gmx.com>, v6ops list <v6ops@ietf.org>, 6man WG <ipv6@ietf.org>, dhcwg <dhcwg@ietf.org>
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To: "Templin (US), Fred L" <Fred.L.Templin@boeing.com>
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Subject: Re: [dhcwg] [EXTERNAL] Question to DHCPv6 Relay Implementors regarding draft-ietf-dhc-dhcpv6-pd-relay-requirements
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> On 7 Oct 2020, at 16:26, Templin (US), Fred L <Fred.L.Templin@boeing.com> wrote:
> 
> Ole, are you talking about the amnesiac client case - such as, the client reboots
> and then comes back to life again with no memory of its past lifetime? Our
> lease lifetimes are short - generally about 30 seconds - so any stale leases
> should be very transient. But, our relays also retain knowledge about the
> client<->server interactions and in some sense act as a proxy for the client.
> So, the relay itself will clean up after an amnesiac client when it detects
> that the client has suffered a traumatic event.

No the routing loop detection code on the relay.

Cheers,
Ole

> 
>> -----Original Message-----
>> From: otroan@employees.org [mailto:otroan@employees.org]
>> Sent: Wednesday, October 07, 2020 6:55 AM
>> To: Templin (US), Fred L <Fred.L.Templin@boeing.com>
>> Cc: ianfarrer@gmx.com; v6ops list <v6ops@ietf.org>rg>; 6man WG <ipv6@ietf.org>rg>; dhcwg <dhcwg@ietf.org>
>> Subject: Re: [dhcwg] [EXTERNAL] Question to DHCPv6 Relay Implementors regarding draft-ietf-dhc-dhcpv6-pd-relay-requirements
>> 
>> This message was sent from outside of Boeing. Please do not click links or open attachments unless you recognize the sender and
>> know that the content is safe.
>> 
>> 
>> 
>>> On 7 Oct 2020, at 15:50, Templin (US), Fred L <Fred.L.Templin@boeing.com> wrote:
>>> 
>>> We implement DHCPv6 PD on relays. The relay is always co-resident with the
>>> delegating server and behaves according to RFC6221. Are we covered?
>> 
>> What's your experience with implementing section 3.5 / R-4?
>> 
>> Cheers,
>> Ole
>> 
>>> 
>>> Thanks - Fred
>>> 
>>> From: dhcwg [mailto:dhcwg-bounces@ietf.org] On Behalf Of ianfarrer@gmx.com
>>> Sent: Wednesday, October 07, 2020 3:26 AM
>>> To: v6ops list <v6ops@ietf.org>rg>; ipv6@ietf.org
>>> Cc: dhcwg <dhcwg@ietf.org>
>>> Subject: [EXTERNAL] [dhcwg] Question to DHCPv6 Relay Implementors regarding draft-ietf-dhc-dhcpv6-pd-relay-requirements
>>> 
>>> This message was sent from outside of Boeing. Please do not click links or open attachments unless you recognize the sender and
>> know that the content is safe.
>>> 
>>> 
>>> Hi,
>>> 
>>> We are currently finishing WGLC for this draft. It describes requirements for a 'DHCPv6 Delegating Relay' - this is a router functioning
>> as the L3 edge and DHCPv6 relay (only) with prefix delegation. This is a common deployment scenario, but RFC3633/8415 only really
>> describes PD using a Delegating Router - i.e the L3 edge also functions as a DHCPv6 server with no relay. When the relay and server
>> functions are performed by separate devices a number of problems with how relays behave have
>>> been observed, so this document addresses them.
>>> 
>>> During WGLC for this, Ole raised a comment related to one of the routing requirements:
>>> 
>>> R-4:    If the relay has learned a route for a delegated prefix via a
>>>           given interface, and receives traffic on this interface with
>>>           a destination address within the delegated prefix (that is
>>>           not an on-link prefix for the relay), then it MUST be
>>>           dropped.  This is to prevent routing loops.  An ICMPv6 Type
>>>           1, Code 6 (Destination Unreachable, reject route to
>>>           destination) error message MAY be sent back to the client.
>>>           The ICMP policy SHOULD be configurable.
>>> 
>>> The problem that this is trying to solve is:
>>> 
>>> 3.5.  Forwarding Loops between Client and Relay
>>> 
>>>   If the client loses information about a prefix that it is delegated
>>>   while the lease entry and associated route is still active in the
>>>   delegating relay, then the relay will forward traffic to the client
>>>   which the client will return to the relay (which is the client's
>>>   default gateway (learnt via an RA).  The loop will continue until
>>>   either the client is successfully reprovisioned via DHCP, or the lease
>>>   ages out in the relay.
>>> 
>>> Ole’s comment: "And I would also be happy if we could have some implementors chime in with a "we are happy and able to
>> implement this requirement”.”
>>> 
>>> 
>>> We would appreciate any feedback on this, especially from anyone with experience implementing DHCPv6 relays with PD.
>>> 
>>> 
>>> Thanks,
>>> Ian
>>> 
>>> 
>>> Current draft version: https://datatracker.ietf.org/doc/draft-ietf-dhc-dhcpv6-pd-relay-requirements/
>>> 
>>> 
>>> _______________________________________________
>>> dhcwg mailing list
>>> dhcwg@ietf.org
>>> https://www.ietf.org/mailman/listinfo/dhcwg
>