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

["Hemant Singh (shemant)" <shemant@cisco.com>]

Barbara,

Thanks for this email. For the purposes of description of behavior of a
CPE Router, all we are asking for is how many physical WAN interface
ports will the CPE Router have? We have recommended one. We could care
less about any other physical layer behavior. We are defining routing
behavior that sits abstracted from link or physical layers. Where a
layer 2 affects IPv6 ND protocol behavior, we mention it - like PPP
address acquisition does not perform DAD. 

Hemant

-----Original Message-----
From: Stark, Barbara [mailto:bs7652@att.com] 
Sent: Tuesday, July 15, 2008 4:17 PM
To: Antonio Querubin; Hemant Singh (shemant)
Cc: v6ops@ops.ietf.org
Subject: RE: Comments on draft-wbeebee-ipv6-cpe-router-01.txt

I don't understand the relevance of mentioning PHY interfaces, PHY
modems, or pure Ethernet switches, in a document about IPv6 behavior of
CPE routers. A physical instantiation of a CPE router may indeed contain
a PHY modem and Ethernet switch, but I don't see why that's relevant or
needs to be called out in this document.

I don't see any functionality described in this draft that changes based
on the link layer or below. Certainly not if the link layer is Ethernet.

I know that there do exist WAN PHY interfaces that do not have the IP
running over either  Ethernet link layer or PPP. Such IP interfaces will
either exhibit the same behavior as described in this document, or they
won't. If they do, that can be mentioned. If they don't, but have mass
market relevance, it can be described how they differ. The WAN interface
as an Ethernet link layer interface will cover all mass market retail
routers, and the vast majority of DSL modem/routers. I can't speak for
DOCSIS or UMTS, since I don't know those protocol stacks very well. If
they don't use Ethernet for their link layers, do they have some other
link layer that is similar to Ethernet? Is there any reason why that
link layer shouldn't be considered the "WAN interface"?
Barbara

-----Original Message-----
From: Antonio Querubin [mailto:tony@lava.net]
Sent: Tuesday, July 15, 2008 2:00 PM
To: Hemant Singh (shemant)
Cc: Stark, Barbara; v6ops@ops.ietf.org
Subject: RE: Comments on draft-wbeebee-ipv6-cpe-router-01.txt

On Tue, 15 Jul 2008, Hemant Singh (shemant) wrote:

> Date: Tue, 15 Jul 2008 11:34:29 -0400
> From: "Hemant Singh (shemant)" <shemant@cisco.com>
> To: "Stark, Barbara" <bs7652@att.com>, v6ops@ops.ietf.org
> Cc: Antonio Querubin <tony@lava.net>
> Subject: RE: Comments on draft-wbeebee-ipv6-cpe-router-01.txt
> 
> Barbara,
>
> Since Antonio also raised a point about IPv6 addresses assigned to the

> WAN interface (and the number of WAN interface(s)), we are combining a

> reply to both you and Antonio.
>
> Barbara, when you say,
>
> "We have considered the possibility of a separate IP address for our
> TR-069 management of the CPE routers that we supply, but would want
this
> to be a
> configurable option."
>
> could you please elaborate. Does this separate IPv6 address get
assigned
> to the WAN side of the CPE Router? If yes, if the WAN interface is
only
> assigned a link-local address, then what network interface on the WAN 
> side does this IPv6 address get assigned to? One choice we have is to 
> assign the IPv6 address to the Loopback interface facing the WAN side.
> Also, when reviewers ask for another network interface on the WAN
side,
> or another IPv6 address on the WAN side, could reviewers please 
> appreciate the fact that another WAN interface can mean two things for
a
> router. Either we have second physical WAN interface with a new 
> mac-address or we still have one WAN interface and the second WAN 
> interface is just a logical interface bound to the physical WAN 
> interface such that both the physical WAN interface and the logical 
> interface share a mac-address between them. Antonio and Barbara, which

> one of these two interfaces are you talking about? Further, if one is 
> spawning logical interfaces on any router, once doesn't have to stop
at
> one extra interface. Go ahead and spawn more if one wants.

Actually the discussion is confusing because the 'WAN' interface appears

to mean different things depending on whether the layer 2 modem is
integrated into the CPE router.  For discussion purposes, in a general
network configuration where all the components are separate you'll have:

                     PCs
                      |
                      |
                      |
----- modem ----- switch ----- router/firewall ----- switch ----- PCs
   1     A     2      B     3         C           4      D     5    E

Devices B and D are just plain ethernet switches.  Although the focus of

this document seems to be on device C, it's interfaces, and the customer

devices (E) behind it, the CPE router being discussed potentially
encompasses functionality of devices A, B, C, and D.

In the case where the modem is integrated, the interface that internally

links the modem to the internal router device C may or may not be
accessible to the consumer via external physical ports.  If they are
physically accessible, they need a different name than "WAN" if "WAN" is

defined to be 1 above.

If the modem is not integrated into your CPE device, then the "WAN" 
interface is just 2 and/or 3 above depending on whether additional "WAN"

ports are provided by the vendor.

However these multiple definitions of WAN interfaces are confusing,
hence my earlier suggestion of using different names for the
modem-router interface and the access provider interface.

> Further, Antonio, when you say,
>
> "Additionally, for those vendors that wish to integrate the layer 2
> (DSL/cable) modem as part of the CPE router (where the "WAN"
> encapsulation is not ethernet), perhaps a separately named interface 
> definition might be appropriate to avoid confusion with "WAN"."
>
> In such a case, the WAN interface is a logical interface that bridges 
> the CPE Router to the broadband modem. We clarified the WAN interface 
> definition as follows with new text
>
> WAN interface - a single physical network interface on the standalone 
> CPE Router that is used to connect the router to the access network of

> the Service Provider. When the CPE Router is embedded in a device that

> connects to the WAN, this interface is a logical network interface
that
> bridges the device to the CPE Router. Some devices which can have an 
> embedded CPE router are: a cable or DSL modem, or a cellular
telephone,
> etc.
>
> When we publish our next revision of the draft, we will include new
text
> for the WAN interface definition.

How about this.  If you want to tie the WAN interface to the internal
router:

WAN interface - a network interface on the CPE Router that is used to
connect the router to the access network of the Service Provider.  When
a CPE Router is embedded in a device that connects to the service
provider

via a non-ethernet connection, this interface is the logical interface
that connects the internal router to the internal bridge.  Some devices
which can have an embedded CPE router are: a cable or DSL modem, or a
cellular telephone, etc.

SPA (service provider access) interface - a non-ethernet physical
network interface that is bridged to the WAN interface and directly
connects to the access network of the Service Provider.

But if you want to keep the definition of WAN tightly coupled with the
physical external port then something like this might be more suitable:

WAN interface - a network interface on the CPE Router that is used to
connect the router directly to the access network of the Service
Provider. 
When a CPE Router is embedded in a device that connects to the service
provider via a non-ethernet connection, this physical interface is
bridged to the router via an internal modem.  Some devices which can
have an embedded CPE router are: a cable or DSL modem, or a cellular
telephone, etc.

WANEA (WAN Ethernet Access) interface - an optional ethernet interface
that is bridged to the WAN interface and provides additional direct
access to the Service Provider network.

You may want to call it something other than WANEA :)

Antonio Querubin
whois:  AQ7-ARIN

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