Re: [dhcwg] I-D Action: draft-ietf-dhc-dhcpv6-pd-relay-requirements-00.txt

["Bernie Volz (volz)" <[e-mail]>]

   WPD-5:  Any packet received by the CE router with a destination
           address in the prefix(es) delegated to the CE router but not
           in the set of prefixes assigned by the CE router to the LAN
           must be dropped.  In other words, the next hop for the
           prefix(es) delegated to the CE router should be the null
           destination.  This is necessary to prevent forwarding loops
           when some addresses covered by the aggregate are not
           reachable [RFC4632].

This doesn't apply as the CE Router has not yet received the prefix(es) delegated. Perhaps it is just poorly written as its intent was to prevent forwarding ANY traffic back out the WAN interface.

> See the sentence above the one you quoted.

Which was:

>>A CPE should never provide transit.
>>I.e it should never forward a packet received on it's WAN interface back out the WAN interface.

But that is not a requirement mentioned. Hence, why Tim probably raised it as some CPE implemented obviously didn't consider it.

Yes, not sure exactly how the text should read. Seems like you are coming around to having some text?

- Bernie

-----Original Message-----
From: [e-mail] <[e-mail]> 
Sent: Wednesday, April 8, 2020 10:37 AM
To: Bernie Volz (volz) <[e-mail]>
Cc: Timothy Winters <[e-mail]>; [e-mail]; [e-mail]
Subject: Re: [dhcwg] I-D Action: draft-ietf-dhc-dhcpv6-pd-relay-requirements-00.txt

>> A more specific rule for that is in 7084 and possibly in 3633, requiring a blockhole route on the requesting router for the delegated prefix.
> 
> But Tim is talking about BEFORE the PD is assigned?

See the sentence above the one you quoted.

> Do you know which requirement that is in 7084? My quick glance/search at the document did not turn up such a requirement? 

WPD-5.

> I doubt 3633 applies because that is only about PD and not what happens before PDs are assigned?
> 
> And as Tim raised it, seems likely that it must be happening frequently enough that whatever may be there is not clear enough?
> 
> Is there ever a case where a CPE should forward a packet received on the WAN interface back out the WAN interface? Probably not as it is designed to be router between the WAN and LAN interfaces only.

As I said, a CPE should not provide transit.
Not quite sure how you would best implement that though, so I'm unsure what the text should be. Perhaps something aking to this paragraph from 4443:

"One specific case in which a Destination Unreachable message is sent
   with a code 3 is in response to a packet received by a router from a
   point-to-point link, destined to an address within a subnet assigned
   to that same link (other than one of the receiving router's own
   addresses).  In such a case, the packet MUST NOT be forwarded back
   onto the arrival link."

Cheers,
Ole