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Re: [v6ops] [homenet] default LAN routing protocol for IPv6CE router

"Pascal Thubert (pthubert)" <pthubert@cisco.com> Sat, 06 August 2011 13:43 UTC

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Date: Sat, 06 Aug 2011 15:42:37 +0200
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Thread-Topic: [homenet] [v6ops] default LAN routing protocol for IPv6CE router
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References: <9E2FAA01116B084A9B10EC34D6015A07482B9D9DB1@DENEXMAIL1.ARRS.ARRISI.COM><CA5EA133.97E6%d.sturek@att.net><067E6CE33034954AAC05C9EC85E2577C0599B4A0@XMB-RCD-111.cisco.com><0EB9D7EF-7B37-45B3-B6E4-5F946B19AC45@bogus.com><80215711-1B7D-428C-9B7B-75D61BFAC66E@apple.com> <73A004D0-2CC2-4B19-A3B2-0ADB79081582@cisco.com>
From: "Pascal Thubert (pthubert)" <pthubert@cisco.com>
To: "Ralph Droms (rdroms)" <rdroms@cisco.com>, james woodyatt <jhw@apple.com>
X-OriginalArrivalTime: 06 Aug 2011 13:44:16.0223 (UTC) FILETIME=[EF0D3EF0:01CC543E]
Cc: IPv6 Operations <v6ops@ietf.org>, homenet@ietf.org
Subject: Re: [v6ops] [homenet] default LAN routing protocol for IPv6CE router
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Hi James;

As Ralph indicates, RFC4944 describes a L2.5 fragmentation mechanism and
recommends a MTU of 1280 on 802.15.4 links.

That fragmentation mechanism does not allow forwarding at L3 (each L3
hop needs to reassemble). It is also sensitive to frame loss, which
sadly is frequent in 802.15.4 though it was mitigated in some
environment such as industrial (see WiHART, ISA100.11a, 802.15.4e).
Both issues (loss and forwarding) are addressed in
http://tools.ietf.org/html/draft-thubert-6lowpan-simple-fragment-recover
y but the draft is homeless at the moment.

4944 is also partially obsoleted by RFC-to-be 6282 for the header
compression piece.

Finally, I'd recommend to take a look at
http://tools.ietf.org/html/draft-thubert-6lowpan-backbone-router-02.
This work was initially a component of the registration based ND that
was designed at 6LoWPAN, and was split in midflight. You'll see in the
overview that the concept is to use a backbone router that proxies ND
between the 802.15.4 meshes and a higher speed Ethernet (or emulated
Ethernet such as WIFI infra mode), with the assumption that the backbone
runs classical ND whereas the  meshes use the registration-based ND.

Cheers,

Pascal


> -----Original Message-----
> From: homenet-bounces@ietf.org [mailto:homenet-bounces@ietf.org] On
> Behalf Of Ralph Droms (rdroms)
> Sent: Wednesday, August 03, 2011 8:12 PM
> To: james woodyatt
> Cc: Joel Jaeggli; IPv6 Operations; homenet@ietf.org
> Subject: Re: [homenet] [v6ops] default LAN routing protocol for IPv6CE
> router
> 
> RFC 4944
> 
> - Ralph
> 
> On Aug 3, 2011, at 2:09 PM 8/3/11, james woodyatt wrote:
> 
> > On Aug 3, 2011, at 10:00 , Joel Jaeggli wrote:
> >>
> >> got a better idea for interconnecting 802.15.4 and 802.3 networks
than at
> layer-3?
> >
> > How does 802.15.4 achieve the 1280 octet minimum MTU size required
by
> IPv6?  I'm sure this is explained in an RFC somewhere, but I don't
know.
> Hoping someone knows off the top of their head and can quickly rattle
off a
> citation from memory.
> >
> >
> > --
> > james woodyatt <jhw@apple.com>
> > member of technical staff, core os networking
> >
> >
> >
> > _______________________________________________
> > v6ops mailing list
> > v6ops@ietf.org
> > https://www.ietf.org/mailman/listinfo/v6ops
> 
> _______________________________________________
> homenet mailing list
> homenet@ietf.org
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