Subject: [v6ops] I-D Action: draft-ietf-v6ops-ipv6rtr-reqs-00.txt

From: [email-masked]
Date: Fri, 05 May 2017 15:01:34 -0700

A New Internet-Draft is available from the on-line Internet-Drafts directories.
This draft is a work item of the IPv6 Operations of the IETF.

        Title           : Requirements for IPv6 Routers
        Authors         : Zaid Ali Kahn
                          John Brzozowski
                          Russ White
	Filename        : draft-ietf-v6ops-ipv6rtr-reqs-00.txt
	Pages           : 29
	Date            : 2017-05-05

Abstract:
   The Internet is not one network, but rather a collection of networks.
   The interconnected nature of these networks, and the nature of the
   interconneted systems that make up these networks, is often more
   fragile than it appears.  Perhaps "robust but fragile" is an
   overstatement, but the actions of each vendor, implementor, and
   operator in such an interconneted environment can have a major impact
   on the stability of the overall Internet (as a system).  The
   widespread adoption of IPv6 could, particularly, disrupt network
   operations, in a way that impacts the entire system.

   This time of transition is an opportune time to take stock of lessons
   learned through the operation of large scale networks on IPv4, and
   consider how to apply these lessons to IPv6.  This document provides
   an overview of the design and architectural decisions that attend
   IPv6 deployment, and a set of IPv6 requirements for routers,
   switches, and middleboxes deployed in IPv6 networks.  The hope of the
   editors and contributors is to provide the neccessary background to
   guide equipment manufacturers, protocol implemenetors, and network
   operators in effective IPv6 deployment.

The IETF datatracker status page for this draft is:
https://datatracker.ietf.org/doc/draft-ietf-v6ops-ipv6rtr-reqs/

There are also htmlized versions available at:
https://tools.ietf.org/html/draft-ietf-v6ops-ipv6rtr-reqs-00
https://datatracker.ietf.org/doc/html/draft-ietf-v6ops-ipv6rtr-reqs-00

Please note that it may take a couple of minutes from the time of submission
until the htmlized version and diff are available at tools.ietf.org.

Internet-Drafts are also available by anonymous FTP at:
ftp://ftp.ietf.org/internet-drafts/

---

From: Lorenzo Colitti <[email-masked]>
Date: Mon, 8 May 2017 11:10:48 +0900

>         Filename        : draft-ietf-v6ops-ipv6rtr-reqs-00.txt

As Ted has stated many times, this text:

======
 Routers supporting IPv6, and intended for user facing
   connections, MUST support:

   o  [RFC3646]: DNS Configuration options for Dynamic Host
      Configuration Protocol for IPv6 (DHCPv6).
======

needs clarification. Does it mean that:

   1. A router MUST contain a stateless DHCPv6 server implementation that
   supports the DNS option?
   2. A router MUST contain a DHCPv6 relay implementation that supports the
   DNS option?
   3. If a router contains an DHCPv6 server or relay implementation, then
   that implementation supports the DNS option?

#1 or #2 would be a change to the IPv6 node requirements, which say
<https://tools.ietf.org/html/rfc6434#section-12.3>:

====
   support for DHCP
   server functionality on routers is optional.  However, routers
   targeted for deployment within more complex scenarios (as described
   above) SHOULD support relay agent functionality
====

I don't think it makes sense to say #1 or #2 and thus say that all IPv6
routers MUST support DHCPv6, because:

   1. Other than for home gateways where DHCPv6 is required, I'd expect
   that the vast majority of routers don't actually support it at all (at
   least not in all feature sets).
   2. In most places in the network there's not even any point in
   supporting it, because it will never be used. DHCPv6 can only ever be used
   in routers that serve as first-hop routers for hosts, so a backbone router
   will never need a DHCPv6 server or relay.

#3 does make sense.

---

From: Richard Hartmann <[email-masked]>
Date: Mon, 8 May 2017 09:16:48 +0200

> needs clarification. Does it mean that:

This section could use some extra clarification, indeed.

> A router MUST contain a stateless DHCPv6 server implementation that supports
> the DNS option?
> A router MUST contain a DHCPv6 relay implementation that supports the DNS
> option?
> If a router contains an DHCPv6 server or relay implementation, then that
> implementation supports the DNS option?

#1 is the only logically consistent interpretation.
#2 would merely shift the problem outside of what you call "first-hop
routers" and the draft calls "Routers supporting IPv6, and intended
for user facing connections". And then the draft would not apply to
those devices any more.
#3 is essentially a no-op and runs counter to the apparent/obvious
intent of draft-ietf-v6ops-ipv6rtr-reqs

Again, this should be cleared up.

> #1 or #2 would be a change to the IPv6 node requirements, which say:

This is inherent to the current chicken-and-egg situation. The way I
read the draft, it partially wants to address exactly this stand-off
of mutually-assured non-complete-stack between RAs & DHCPv6, enabling
more comprehensive IPv6 adoption, instead.

> routers MUST support DHCPv6, because:

It does not say that "all IPv6 routers", it says "Routers supporting
IPv6, and intended for user facing connections".

> Other than for home gateways where DHCPv6 is required, I'd expect that the
> vast majority of routers don't actually support it at all (at least not in
> all feature sets).

I would argue that this also includes corporate/campus settings.

> In most places in the network there's not even any point in supporting it,
> because it will never be used. DHCPv6 can only ever be used in routers that
> serve as first-hop routers for hosts, so a backbone router will never need a
> DHCPv6 server or relay.

All of this is neatly addressed in the draft as it limits the scope of
DHCPv6 MUST to routers intended for end-user networks.

Richard

---

From: Tim Chown <[email-masked]>
Date: Mon, 8 May 2017 10:32:18 +0000

Hi,

> On 8 May 2017, at 03:10, Lorenzo Colitti <[email-masked]> wrote:
> 
> 	• A router MUST contain a stateless DHCPv6 server implementation that supports the DNS option?
> 	• A router MUST contain a DHCPv6 relay implementation that supports the DNS option?
> 	• If a router contains an DHCPv6 server or relay implementation, then that implementation supports the DNS option?
> I don't think it makes sense to say #1 or #2 and thus say that all IPv6 routers MUST support DHCPv6, because:
> 	• Other than for home gateways where DHCPv6 is required, I'd expect that the vast majority of routers don't actually support it at all (at least not in all feature sets).
> 	• In most places in the network there's not even any point in supporting it, because it will never be used. DHCPv6 can only ever be used in routers that serve as first-hop routers for hosts, so a backbone router will never need a DHCPv6 server or relay.
> #3 does make sense.

Worth noting that the node requirements document is undergoing an update, so its text might change.

I would certainly say that #3 is a minimum

There are also of course enterprises that wish to run DHCPv6, but I’d assume they would do so using first-hop relays. In that light, adding at least a SHOULD for RFC6939 would be good, if its not in this draft already. 

The text should probably talk about DHCPv6 requirements for routers that may typically be deployed in client-facing scenarios.

Tim