Subject: [16ng] WGLC: draft-ietf-16ng-ipv6-link-model-analysis-00 - REMIND

From: "Soohong Daniel Park" <[email-masked]>
Date: Thu, 19 Oct 2006 09:03:34 +0900

REMIND: Please go through the document below, then make your comments
on this call. One week is past..

==============

Folks,

This is a two week WGLC on draft-ietf-16ng-ipv6-link-model-analysis-00.

Please review the I-D and submit your comments to the authors or to
the list directly. The WGLC will exipre on October 26 (Pacific Time).

o I-D: http://www.ietf.org/internet-drafts/draft-ietf-16ng-ipv6-link-model-analysis-00.txt

o Intended publication: Informational RFC

-- 

Daniel (Soohong Daniel Park)
Mobile Convergence Laboratory, SAMSUNG Electronics.
_______________________________________________
16ng mailing list
[email-masked]
http://eeca16.sogang.ac.kr/mailman/listinfo/16ng

---

From: Alexandru Petrescu <[email-masked]>
Date: Thu, 19 Oct 2006 15:33:13 +0200

draft-ietf-16ng-ipv6-link-model-analysis-00

Hi authors of this draft and the WG.

> This document provides different IPv6 link models that are suitable 
> for 802.16 based networks and provides analysis of various 
> considerations for each link model and the applicability of each link
>  model under different deployment scenarios.

Are the link models considered in this draft pertaining to the Mobile, 
or just generic 802.16?  The draft mentions "last mile" at some point, 
but usually last mile doesn't necessarily mean the mobile itself; "last 
mile" usually means a connection to a private SOHO or enterprise, whose 
competitors are usually copper xDSL and optical fiber.

The document also mentions MS at several points, for Mobile Station.

Just for clarification, are those link models concerning a mobile 
station (under the form of a handset, laptop, etc) or not?

>         +-----+
>         | MS1 |-----+
>         +-----+     |
>                     |
>                     |
>         +-----+     |     +-----+          +--------+
>         | MS2 |-----+-----| BS1 |----------|   AR   |-------[Internet]
>         +-----+     |     +-----+          +--------+
>            .        |           ____________
>            .        |          ()__________()
>         +-----+     |             L2 Tunnel
>         | MSn |-----+
>         +-----+
> 
> 
>                Figure 1. Shared IPv6 Prefix Link Model

What is an "L2 tunnel"?  Is it an L2 header packet appended to another 
one?  Are those headers MAC headers?  (dst, src, type).

What is the need for L2 tunnels between BS1 and AR?  Why not straight IP 
  links over Ethernet?  Why encapsulation.  Why not a straight L2 link.

Alex

---

From: "Soininen Jonne (Nokia-NET/Espoo)" <[email-masked]>
Date: Thu, 19 Oct 2006 17:26:11 +0300

Hi again Alex,

It seems to be me and you mostly discussing on this list (with an occational
intervention from Jouni).

Please, find my comments below:

> competitors are usually copper xDSL and optical fiber.

Generally, the last mile in wireless/cellular/mobile networking terms can be
the transport between the BS (wireless, wired, whatever) and the rest of the
network or the link between MS and it's Access Router. It is not only a term
reserved for fixed Internet access (like copper or fiber).

> station (under the form of a handset, laptop, etc) or not?

The link-model concern the link between the MS and the AR.
 
>   links over Ethernet?  Why encapsulation.  Why not a straight L2 link.

Theoretically the headers can be MAC headers, or GRE encapsulation.

The tunnels, and tunnel management is needed especially in the case of
mobility. The local mobility is handled by tunnels between the BS and the
AR. When the MS moves to another BS the tunnel is updated between the new BS
and the AR. This way the MS does not notice the movement and can keep its
current IP address.

I hope this helps,

Jonne.

-- 
Jonne Soininen
Nokia

Tel: +358 40 527 46 34
E-mail: [email-masked]

---

From: Alexandru Petrescu <[email-masked]>
Date: Thu, 19 Oct 2006 17:11:16 +0200

> intervention from Jouni).

Well, I'll try to follow more the discussion.

> reserved for fixed Internet access (like copper or fiber).

Yes but 802.16 (without e) is specifically for wireless fixed Internet 
access.  Is this document for those cases or not for those cases.  If 
it's not for those cases then it should only talk 802.16e.

> The link-model concern the link between the MS and the AR.

Ok.

> Theoretically the headers can be MAC headers, or GRE encapsulation.

Huh?  I don't think GRE encapsulation can be qualified as "L2 Tunnel". 
The Delivery Header of GRE is IPv4 or IPv6, not MAC.

> and the AR. This way the MS does not notice the movement and can keep its

I see, so it's for mobility that the 'L2 Tunnels' are there.

I think this draft should be clearer what 'L2 Tunnels' are, in absence 
of mobility.  Or maybe ignore them entirely.

The other comment I had is that the overall conclusion of the draft 
seems to incline to the 'per-mobile' prefix model, and so because it is 
simpler to do DAD and does not break existing apps; it also says that 
the shared prefix model could be defined if interest from the service 
provider community.  Basically - let's wait and see.

Alex

---

From: "Soininen Jonne (Nokia-NET/Espoo)" <[email-masked]>
Date: Thu, 19 Oct 2006 18:29:54 +0300

Hi Alex,

On 10/19/06 6:11 PM, "ext Alexandru Petrescu"
<[email-masked]> wrote:

[snip]
> it's not for those cases then it should only talk 802.16e.

I believe you're right.

[snip]
> The Delivery Header of GRE is IPv4 or IPv6, not MAC.

Right, I guess what the draft is trying to say (editors/authors please tell
me if I'm right) that the tunnel is _underneath_ the MS's IP. (IP/GRE/MS'es
IP) The tunnel is L2 from the MS's point of view.

True, this can be confusing for the reader. Maybe this is something to be
changed.

> of mobility.  Or maybe ignore them entirely.

They can be used also to connect the MS to its own AR even in a fixed
scenario, when there are multiple ARs in the network. Maybe the use of the
tunnels could be spelled out more clearly.

> provider community.  Basically - let's wait and see.

Yes, this was the conclusion where the WG came to in the consensus call.

Cheers,

Jonne.

-- 
Jonne Soininen
Nokia

Tel: +358 40 527 46 34

---

From: Alexandru Petrescu <[email-masked]>
Date: Thu, 19 Oct 2006 20:40:24 +0200

Syam Madanapalli wrote:
> Hi Alex,
> 
> On 10/19/06, Alexandru Petrescu <[email-masked]> 
> wrote:
>>> This document provides different IPv6 link models that are 
>>> suitable for 802.16 based networks and provides analysis of 
>>> various considerations for each link model and the applicability 
>>> of each link model under different deployment scenarios.
>> 
>> Are the link models considered in this draft pertaining to the 
>> Mobile, or just generic 802.16?  The draft mentions "last mile" at 
>> some point, but usually last mile doesn't necessarily mean the 
>> mobile itself; "last mile" usually means a connection to a private 
>> SOHO or enterprise, whose competitors are usually copper xDSL and 
>> optical fiber.
>> 
> We considered all of these deployment scenarios for both 802.16 and 
> 802.16e. The current recommendation is to use Eth CS for the 
> fixed/nomadic deployment scenarios,

For fixed _or_ for nomadic?  For fixed _and_ for nomadic?  Fixed is 
usually different than nomadic.

>> What is an "L2 tunnel"?  Is it an L2 header packet appended to 
>> another one?  Are those headers MAC headers?  (dst, src, type).
> 
> As Jonne mentioned in one of his mails, it is IP in IP tunnel, may be
>  we will change it in the next revision.

YEs, suffices it to call it L3 tunnel, not L2 tunnel.

>> What is the need for L2 tunnels between BS1 and AR?  Why not 
>> straight IP links over Ethernet?  Why encapsulation.  Why not a 
>> straight L2 link.
> 
> If there is no tunnel, the IP link ends at BS, and BS should be a 
> router.

If BS has two IP addresses and two interfaces it's almost a router
anyways.  Could the BS be a router in WiMax?

> If not tunnel there should be other mechanisms that preserves the IP
> header till the packet reaches the AR.

A router doesn't change the IP headers, right?  Neither does a bridge.

An L3 tunnel is only needed if there is at least one intermediary router 
between BS and AR.  It's not pictured.

Alex

> 
> Thanks, Syam
> 
>> 
>> Alex
>> 
>> _______________________________________________ 16ng mailing list 
>> [email-masked]

---

From: "Syam Madanapalli" <[email-masked]>
Date: Fri, 20 Oct 2006 00:28:33 +0530

> usually different than nomadic.

OK, it is fixed and nomadic.

> YEs, suffices it to call it L3 tunnel, not L2 tunnel.

OK

> anyways.  Could the BS be a router in WiMax?

Yep, In this case BS and AR would be in one box.

> A router doesn't change the IP headers, right?  Neither does a bridge.

Hop limit?

> between BS and AR.  It's not pictured.

The other reason we may need a tunnel between BS and AR is to identify
an MS when it sends a RS with unspecified address. There will be a tunnel
each MS between BS and AR.

Thanks,
Syam

---

From: Alexandru Petrescu <[email-masked]>
Date: Thu, 19 Oct 2006 21:30:50 +0200

Syam Madanapalli wrote:
>>>> Just for clarification, are those link models concerning a 
>>>> mobile station (under the form of a handset, laptop, etc) or 
>>>> not?
>>> 
>>> We considered all of these deployment scenarios for both 802.16 
>>> and 802.16e. The current recommendation is to use Eth CS for the

Errr... so a mobile host would run same Ethernet CS layer as a fixed
host, ok.

>>> As Jonne mentioned in one of his mails, it is IP in IP tunnel, 
>>> may be we will change it in the next revision.
>> 

Right, it's written in the draft.

>>> If not tunnel there should be other mechanisms that preserves the
>>>  IP header till the packet reaches the AR.
>> 

Hop limit changes ok - and?  PAcket is still delivered, and no entity in
the operator network cares about it other than decrementing it.  It's
not like an address entry in the binding cache or in SA, SPD; nor a
firewall ingress filtering...

Why do you think decrementing the hop-limit in IP packet is bad for the
MS-BS-AR network?

>> An L3 tunnel is only needed if there is at least one intermediary 
>> router between BS and AR.  It's not pictured.
> 
> The other reason we may need a tunnel between BS and AR is to 
> identify an MS when it sends a RS with unspecified address.

Instead of the unspecified address why not using the fe80::IID, IID
given by IPv6 LCP PPP AR to the MS?

> There will be a tunnel [for] each MS between BS and AR.

An IP-in-IP tunnel?  An IP-in-L2?  It implies it's not a 'tunnel', but 
normal inclusion of L3 messages in L2 messages.  You mean a 'connection' 
instead of 'tunnel'?

(In TCP/IP terms a 'tunnel' is when one has two IP headers preceding the
payload.  Logical extension to 'L2 tunnel' makes think of two L2 headers
preceding the L3 datagram.)

Or do you mean encapsulating an L2 message into an L3 message and back 
into L2?  That's an ugly hack - it generates huge packets, and can be 
avoided by rewriting the L2 address (necessary to AR) or by making BS 
act as a more transparent bridge, if you wish.

Thanks, trying to understand it myself,

Alex

---

From: "Syam Madanapalli" <[email-masked]>
Date: Thu, 19 Oct 2006 23:44:03 +0530

Hi Alex,

We considered all of these deployment scenarios for both 802.16 and
802.16e. The current recommendation is to use Eth CS for the fixed/nomadic
deployment scenarios, for mobile WiMAX the recommendation is to use
IP CS. In either case there can be a network behind an MS.

> one?  Are those headers MAC headers?  (dst, src, type).

As Jonne mentioned in one of his mails, it is IP in IP tunnel, may be we
will change it in the next revision.

>   links over Ethernet?  Why encapsulation.  Why not a straight L2 link.

If there is no tunnel, the IP link ends at BS, and BS should be a router.
If not tunnel there should be other mechanisms that preserves the IP
header till the packet reaches the AR.

Thanks,
Syam

---

From: "Syam Madanapalli" <[email-masked]>
Date: Fri, 20 Oct 2006 22:22:06 +0530

Hi,

> Errr... so a mobile host would run same Ethernet CS layer as a fixed

I do not understand this.
Anyways, if a mobile node supports Ethernet CS, it should be able to
connect to any BS that supports Ethernet CS, though the expectation
is that, the mobile hosts implement IP CS. On the other hand, portable
(e.g. laptops) and fixed device would implement Ethernet CS for
broadband connectivity.
[cut]
> Why do you think decrementing the hop-limit in IP packet is bad for the

May be you have not come across the following draft on issues with
Multilink Subnet
http://www.ietf.org/internet-drafts/draft-iab-multilink-subnet-issues-00.txt

> given by IPv6 LCP PPP AR to the MS?

RS can be sent even before the link local address is configured.
And right now no CS have been defined for PPP over 802.16.

> preceding the L3 datagram.)

It's two IP headers preceeding the payload.

Thanks,
Syam