Re: Comments on draft-wbeebee-ipv6-cpe-router-01.txt

["tom.petch" <cfinss@dial.pipex.com>]

----- Original Message -----
From: "Antonio Querubin" <tony@lava.net>
To: "Hemant Singh (shemant)" <shemant@cisco.com>
Cc: "Stark, Barbara" <bs7652@att.com>; <v6ops@ops.ietf.org>
Sent: Friday, July 18, 2008 5:57 PM
Subject: RE: Comments on draft-wbeebee-ipv6-cpe-router-01.txt


> I wonder, for those who feel a loopback interface is important, is that
> because you want the CPE router to be pingable regardless of any PHY
> interface status?  If that's so, since the document's focus is on router
> behaviour, perhaps it is this behaviour should be explicitly mentioned.

For me, it is not just pingable but all aspects of control and management.  I
have always thought the term 'loopback' misleading.  I first encountered it with
routing protocols, with the need to have a stable IP address to which to send
updates, even, especially, when an interface was down and so packets could not
be sent to the address of that interface -  and there was never any way of
knowing which interfaces were still up.  I see such a concept, although not
necessarily with the same name, in use with ftp, to download configurations and
code updates; with snmp, for general purpose management; with telnet, ditto;
even with icmp.  Commonly, it is possible to have multiple such addresses, to
split the traffic and security for different applications, but I expect there to
be at least one, whose status is divorced from the physical status of any or all
the interfaces.

I am talking, as you may deduce, of experience with IPv4, not with IPv6, and
appreciate that IPv6 has lots of clever additions, but suspect that the
principle remains, that if an interface goes down, then it will not be possible
to send packets to the address of that interface, and so a virtual interface
address is needed.  I assume that the address must be global although where the
prefix comes from is a subtlety I have yet to understand.  With IPv4, all the
routers in a domain could share the prefix with the individual /32 being
advertised.

Tom Petch

> Section 5, paragraph 1 states 'optional Loopback network interface, facing
> the Service Provider upstream, which initiates stateless DHCPv6'.  A
> loopback interface doesn't really 'face' any direction.  You might want to
> change the wording to something along the lines of 'optional Loopback
> network interface initiates a DHCPv6 request toward the upstream SP'
>
> Also I notice in the same paragraph, "recommend the CPE Router WAN
> interface acquire its global IPv6 address using stateful DHCPv6 for
> administrative control of the router".  This makes it sound like DHCP is
> recommended for administrative control where I think you mean the global
> address is recommended for administrative control and provisioning of
> proxied services to the downstream devices.  Why not just say "recommend
> the CPE Router acquire a global IPv6 address for administrative control
> ..."
>
> Antonio Querubin
> whois:  AQ7-ARIN
>