Subject: RE: Open issues list? [Re: New (-02) version of IPv6 CPE Router draft is available for review]

From: Francois-Xavier Le Bail <[email-masked]>
Date: Wed, 30 Jul 2008 05:28:05 -0700 (PDT)

What consideration about MLD snooping [RFC4541] on the LAN bridge ?
Without it, a multicast flow will flood all segments on all ports.
Significant bandwidth can be wasted by flooding.

       +------------------------+
       | Routing CPE w/ bridge  |
       | +------+     +------+  |
 Port1-|-|      |     |      |  |
       | |Bridge|-----|Router|--|----WAN
 Port2-|-|      |  LAN|      |  |
       | +------+     +------+  |
       +------------------------+
(David's reference for a routing CPE with internal MAC bridge)

Francois-Xavier

--- On Tue, 7/29/08, Hemant Singh (shemant) <[email-masked]> wrote:

> From: Hemant Singh (shemant) <[email-masked]>
> Subject: RE: Open issues list? [Re: New (-02) version of IPv6 CPE Router draft is available for review]
> To: "Brian E Carpenter" <[email-masked]>, [email-masked]
> Cc: "Alain Durand" <[email-masked]>
> Date: Tuesday, July 29, 2008, 4:29 AM
> Brian,
> 
> I and Wes can recall only two issues that have not reached
> consensus.  
> 
> The big one was Addressing of the CPE Router WAN interface
> because NTT,
> AT&T, a few folks from the DSL Forum were not in
> complete agreement - I
> and Wes are working this one and this is close to closure. 
> We talked
> with NTT yesterday and David Miles who works in the DSL
> Forum.  We will
> send email on this closure sometime today.
> 
> Next one is use of ULA for the home network on the LAN
> interface(s) of
> the CPE Router.  What we have in mind ULA lasts on the
> device till the
> next reboot (ULA will not be renumbered on the device
> acquiring a GUA)
> upon which the same ULA or a different ULA may be generated
> by the
> device.  We are saying the LAN interface(s) will use ULA
> for the
> lifetime of the CPE Router till the router reboots.  Alain
> is one person
> who would like to renumber the ULA on the LAN interface
> acquiring a GUA.
> I didn't see enough justification from him to change
> the draft in the
> ULA regard.  Remi has also replied to Alain's concerns
> and claimed they
> are non-issues.  
> 
> Thanks.
> 
> Hemant
> 
> -----Original Message-----
> From: [email-masked]
> [mailto:[email-masked]] On
> Behalf Of Brian E Carpenter
> Sent: Monday, July 28, 2008 11:34 AM
> To: [email-masked]
> Cc: Alain Durand
> Subject: Open issues list? [Re: New (-02) version of IPv6
> CPE Router
> draft is available for review]
> 
> There wasn't time in the meeting today for me to ask
> this:
> 
> Where is the open issues list for this draft, so that we
> can identify
> the non-consensus items and drive them to a resolution?
> 
>      Brian

---

From: "Hemant Singh (shemant)" <[email-masked]>
Date: Wed, 30 Jul 2008 11:14:32 -0400

Of course, if there is a bridge to the LAN, then MLD snooping is
required.  But a CPE Router may not include a bridge to the LAN in which
case no MLD snooping is required.  Our new mcast section, that
essentially references RFC4605, will add such a statement.

Hemant 

-----Original Message-----
From: Francois-Xavier Le Bail [mailto:[email-masked]] 
Sent: Wednesday, July 30, 2008 1:28 PM
To: [email-masked]; Hemant Singh (shemant); Wes Beebee (wbeebee)
Cc: Brian E Carpenter
Subject: RE: Open issues list? [Re: New (-02) version of IPv6 CPE Router

Francois-Xavier

--- On Tue, 7/29/08, Hemant Singh (shemant) <[email-masked]> wrote:

> I and Wes can recall only two issues that have not reached consensus.
> 
> The big one was Addressing of the CPE Router WAN interface because 
> NTT, AT&T, a few folks from the DSL Forum were not in complete 
> agreement - I and Wes are working this one and this is close to 
> closure.
> We talked
> with NTT yesterday and David Miles who works in the DSL Forum.  We 
> will send email on this closure sometime today.
> 
> the CPE Router.  What we have in mind ULA lasts on the device till the

> next reboot (ULA will not be renumbered on the device acquiring a GUA)

> upon which the same ULA or a different ULA may be generated by the 
> device.  We are saying the LAN interface(s) will use ULA for the 
> lifetime of the CPE Router till the router reboots.  Alain is one 
> person who would like to renumber the ULA on the LAN interface 
> acquiring a GUA.
> I didn't see enough justification from him to change the draft in the 
> ULA regard.  Remi has also replied to Alain's concerns and claimed 
> they are non-issues.
> 
> Thanks.
> 
> Hemant
> 
> Subject: Open issues list? [Re: New (-02) version of IPv6 CPE Router 
> Where is the open issues list for this draft, so that we can identify

---

From: Francois-Xavier Le Bail <[email-masked]>
Date: Wed, 30 Jul 2008 09:35:59 -0700 (PDT)

--- On Wed, 7/30/08, Hemant Singh (shemant) <[email-masked]> wrote:
> Of course, if there is a bridge to the LAN, then MLD
> snooping is required.
> [...]
> Our new mcast section, that essentially references RFC4605,
> will add such a statement.

Good,

Francois-Xavier

---

From: Mikael Abrahamsson <[email-masked]>
Date: Thu, 31 Jul 2008 09:31:45 +0200 (CEST)

> Significant bandwidth can be wasted by flooding.

I would just like to highlight a scenario that everybody should be aware 
of, sorry if this is obvious to everybody here, I know not enough people 
in other places are aware of it.

With most ATA/VOIP boxes, the uplink interface is 10/half. A multicast 
stream SDTV might be 6-8 megabit/s, so when channel zapping, there might 
be a short while (100ms) where two streams are being sent out on the local 
segment. If the L2 switch connecting the devices doesn't do IGMP/MLD 
snooping, the ATA box port will be take more than 10 meg of potential 
traffic for the duration of the burst, which hurts voice quality (since 
this will most likely cause packet loss). Since most cheaper L2 devices 
also do not have per-port buffers, but instead have shared buffers, it 
means that this problem might hurt traffic on other ports as well, 
incurring packet loss there also.

So, what I like about IPv6 and DHCPv6-PD is that these kind of low-speed 
devices that should never get multicast traffic, can be put on another L2 
domain and have L3 separation from the devices that actually need to 
listen to the multicast.

I don't know how this might fit into the CPE router draft, but my 
recommendation for CPE router is that it should have at least 4 LAN ports 
and it should be possible for these 4 LAN ports to be 4 separate routed 
interfaces to enable L3 separation between different devices.

This can also be solved by MLD snooping and personally I'd like to see 
both, but it might be cheaper for the CPE manufacturer to implement routed 
ports than to get a built in L2 switch that actually does MLD.

-- 
Mikael Abrahamsson    email: [email-masked]

---

From: "Hemant Singh (shemant)" <[email-masked]>
Date: Thu, 31 Jul 2008 03:56:01 -0400

The CPE Router will NOT mandate how many LAN ports does the device have
- it's left to a vendor.  Further, we have left it to the vendor as well
for LAN interface(s) to be bridged, switched, or routed ports.  See the
definition in our Terminology section.

[LAN interface(s) - a set of network interfaces on the CPE Router that
are used to connect hosts in the home. This set of ports could be
switched, bridged, or routed.] 

Please rest your case.  That's the most the CPE Router will specify.
Please talk to CPE Router vendors, not authors of this draft.

Hemant 

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On
Behalf Of Mikael Abrahamsson
Sent: Thursday, July 31, 2008 8:32 AM
To: [email-masked]
Subject: RE: Open issues list? [Re: New (-02) version of IPv6 CPE Router
draft is available for review]

With most ATA/VOIP boxes, the uplink interface is 10/half. A multicast
stream SDTV might be 6-8 megabit/s, so when channel zapping, there might
be a short while (100ms) where two streams are being sent out on the
local segment. If the L2 switch connecting the devices doesn't do
IGMP/MLD snooping, the ATA box port will be take more than 10 meg of
potential traffic for the duration of the burst, which hurts voice
quality (since this will most likely cause packet loss). Since most
cheaper L2 devices also do not have per-port buffers, but instead have
shared buffers, it means that this problem might hurt traffic on other
ports as well, incurring packet loss there also.

So, what I like about IPv6 and DHCPv6-PD is that these kind of low-speed
devices that should never get multicast traffic, can be put on another
L2 domain and have L3 separation from the devices that actually need to
listen to the multicast.

I don't know how this might fit into the CPE router draft, but my
recommendation for CPE router is that it should have at least 4 LAN
ports and it should be possible for these 4 LAN ports to be 4 separate
routed interfaces to enable L3 separation between different devices.

This can also be solved by MLD snooping and personally I'd like to see
both, but it might be cheaper for the CPE manufacturer to implement
routed ports than to get a built in L2 switch that actually does MLD.

---

From: Mikael Abrahamsson <[email-masked]>
Date: Thu, 31 Jul 2008 10:14:41 +0200 (CEST)

> The CPE Router will NOT mandate how many LAN ports does the device have

I didn't ask for "mandate". I just thought the scenario is not an obvious 
one and would make sense to have it in some kind of informational section 
or separate document, but you seem very adamant that it doesn't apply...

> Please rest your case.  That's the most the CPE Router will specify.

Well then.

---

From: "Hemant Singh (shemant)" <[email-masked]>
Date: Thu, 31 Jul 2008 04:43:26 -0400

Sorry, didn't mean to sound adamant.  There are several other cases in
home deployments that deserve to be mentioned, but our draft is not in
the business of mentioning such example cases. 

Thanks.

Hemant   

-----Original Message-----
Sent: Thursday, July 31, 2008 9:15 AM

> The CPE Router will NOT mandate how many LAN ports does the device 

I didn't ask for "mandate". I just thought the scenario is not an
obvious one and would make sense to have it in some kind of
informational section or separate document, but you seem very adamant
that it doesn't apply...

Well then.

---

From: Mikael Abrahamsson <[email-masked]>
Date: Thu, 31 Jul 2008 10:47:51 +0200 (CEST)

> the business of mentioning such example cases.

So, I do feel it's important information to explain how a home network 
might look like for triple play services to work well. Would it make sense 
to create a new document outlining deployment scenarios? Is there already 
a document where this information might fit?

---

From: Brian E Carpenter <[email-masked]>
Date: Thu, 31 Jul 2008 21:06:52 +1200

>> Please rest your case.  That's the most the CPE Router will specify.

Actually, if this is to become a WG draft, it will specify whatever
the WG consensus turns out to be. fwiw, my view is that Hemant is correct,
and it isn't for the IETF to specify how many ports a vendor might
choose to include in their product. (Of course, if it's going to be
an independent submission, the draft can say whatever its authors want.)

     Brian

---

From: "Hemant Singh (shemant)" <[email-masked]>
Date: Thu, 31 Jul 2008 05:16:13 -0400

As usual, I have to thank Brian for another email.  I am also planning
for the day when one day this document becomes a WG document.  Folks
should realize we'll thrash forever soon as someone proposes including 4
ports on the CPE Router, someone else will say 5 or 6 - even specifying
"at least" 4 ports is the same slippery slope.  The number of LAN ports
is best left to the vendors to differentiate their products in any way
they want. 

Thanks.

Hemant 

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On
Behalf Of Brian E Carpenter
Sent: Thursday, July 31, 2008 10:07 AM
To: Mikael Abrahamsson
Cc: [email-masked]
Subject: Re: Open issues list? [Re: New (-02) version of IPv6 CPE Router
draft is available for review]

>> Please rest your case.  That's the most the CPE Router will specify.

Actually, if this is to become a WG draft, it will specify whatever the
WG consensus turns out to be. fwiw, my view is that Hemant is correct,
and it isn't for the IETF to specify how many ports a vendor might
choose to include in their product. (Of course, if it's going to be an
independent submission, the draft can say whatever its authors want.)

     Brian

---

From: james woodyatt <[email-masked]>
Date: Thu, 31 Jul 2008 11:52:33 +0100

> Please talk to CPE Router vendors, not authors of this draft.

The sentence at the end of section 1, Introduction, which reads, "Each  
LAN interface is Ethernet encapsulated," should be elided altogether.

--
james woodyatt <[email-masked]>
member of technical staff, communications engineering

---

From: "Hemant Singh (shemant)" <[email-masked]>
Date: Thu, 31 Jul 2008 10:54:55 -0400

James,

Thanks for this catch.  We will remove the sentence you asked to be
nuked. 

We missed the fact that some LAN interfaces may be USB or some new LAN
port types.

Hemant 

-----Original Message-----
From: james woodyatt [mailto:[email-masked]] 
Sent: Thursday, July 31, 2008 11:53 AM
To: Hemant Singh (shemant)
Cc: IPv6 Operations
Subject: Re: Open issues list? [Re: New (-02) version of IPv6 CPE Router

On Jul 31, 2008, at 08:56, Hemant Singh (shemant) wrote:
> - it's left to a vendor.  Further, we have left it to the vendor as 
> well for LAN interface(s) to be bridged, switched, or routed ports.  
> See the definition in our Terminology section.
>