RE: draft-arberg-pppoe-mtu-gt1492-00

Jerome Moisand writes:
> Not exactly sure what non-IEEE-compliant mechanism you are referring to?
> 
> Using a PPP MRU of 1500 over PPPoE clearly implies the use of an
> Ethernet frame size larger than 1500 bytes, but IEEE standards now
> support such technology (aka jumbo-frames, mini jumbo frames, etc).

Really?  Can you cite which published IEEE standard actually supports
jumbo frame operation?  (And, better still, describes how the
interoperability problems are mitigated, as that's the crucial bit I
think we're missing here.)

I can't seem to locate the standard that supports this idea.

I know that many products (even from Sun and Juniper) support jumbo
frame operation, but unless I'm missing something I don't see where
it's actually been adopted as a standard.

The last I'd heard was that the 802.3 WG "feels that Jumbo frames are
a bad idea."  Has this been amended?

> So if all network segments between the PPPoE "newer" client and the
> PPPoE server support such larger frame as a deployment rule, then we
> have no issue,

Right.  But we simply have no way of knowing that this is true, and
failure modes are both catastrophic and potentially (due to STP)
latent.

I'm really uncomfortable with publishing an RFC that clearly depends
on essentially arbitrary deployment rules in order to function
correctly.  It seems like bad practice to me.

> and this seems to me as being fully IEEE compliant.

That's the part I'm missing.

> Practically speaking, the DSL topologies that we have in mind would
> indeed have such property.
> 
> Yet we need the mitigation mechanism to deal with legacy cases, and
> notably home LANs limited to 1500 Ethernet frames.

Ditching PPPoE as an unnecessary expense and just using plain old IP
on Ethernet would fix that problem neatly.

-- 
James Carlson, KISS Network                    <[email protected]>
Sun Microsystems / 1 Network Drive         71.234W   Vox +1 781 442 2084
MS UBUR02-212 / Burlington MA 01803-2757   42.497N   Fax +1 781 442 1677

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