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Re: IP MPE payload
On Wed, 31 Oct 2001, Gorry Fairhurst wrote:
> Let me try to clarify a few points - especially for those
> who do not have a copy of the EN 301 192 being quoted.
register at www.etsi.org and you get three free downloads. That's
how I got my pdf copy... the latest copy is 1999 1.2.1, btw.
Patrick suggested:
> > > LLC_SNAP_flag == 0 means payload raw IPv4
> > > LLC_SNAP_flag == 1 means whatever is in the AAL5 (see RFC1483)
> > > if AAL5 Ethertype == 0x86DD then IPv6
> >
> > Ah, that's slightly clearer and I understand your previous mails
> > better...
> >
> > ...but then you wouldn't need the flag, since IPv4 has an Ethertype
> > anyway. And if you used the flag this way you'd favour IPv6 rather
> > than 4 - since IPv6 has bigger headers and MTU requirements, and
> > benefits from the added space resulting from removing the encap.
> >
>
> The EtherType is not carried in the normal MPE header (without LLC).
Yes, you would need an Etherype-aware encap in there.
> > ...but there is no mention of AAL5 in EN 301 192. Why would you want
> > the additional overhead of AAL5 encapsulation/checksumming etc - and
> > when you say 'the standard', which standard are you referring to?
> >
>
> There isn't a reference in the EN to an RFC describing IP over LLC/SNAP!!
no change there in the latest version. they presume IP (4 and 6) is
carried raw.
> The latest rev of EN 301 192 that I have seen is V1.1.1 (1997-08)
the 1999 copy is available from www.esti.org after you jump through
some annoying give-details hoops.
> > And EN 301 192 (V1.2.1 199-06) talks about IP, not IPv4.
1999-06, sorry.
> This is a nuisance. The EN appears to only support IPv4 without LLC/SNAP,
> but this is NEVER explicitly stated. Indeed it didn't differentiate IPv4
> or IPv6. There isn't even a ref to an IP RFC!!!!
...and they make me register to read it, so I thought it was going to
be GOOD!
L.
<L.Wood@surrey.ac.uk>PGP<http://www.ee.surrey.ac.uk/Personal/L.Wood/>