Re: Subject: I-D ACTION:draft-clausen-ipdvb-enc-00.txt

["Thomas 'Dent' Mirlacher" <dent@cosy.sbg.ac.at>]

--snip/snip

> > > Without layer 2 source address, how do we recognize our own datagrams,
> > > when we get them back on the link several ms after sending them.
> > > ...
> > >
> > > If we are really convinced that in some cases either the destination
> > > and/or source MAC address are uneeded, and if the goal is to save some
> > > bits not having them, we could use 2 bits out of the length field
> > > The length field would then be 14 bits ([0,16383])
> > > MAC_FLAG
> > >
> > > 00 : no dst MAC, no src MAC
> > > 01 : dst MAC, no src MAC
> > > 10 : src MAC, no dst MAC
> > > 11 : dst MAC, src MAC
> > >
> > > MAC is IEEE 48 bits
> > > no dst MAC is equivalent to a broadcast: ff:ff:ff:ff:ff:ff
> > >
> > > +--+--------------+----------------+----------
> > > |00|    length    |      type      |Payload
> > > +--+--------------+----------------+----------
> > >
> > > +--+--------------+----------------+-----------  --+----------
> > > |01|    length    |      type      |48 bits dst ~  | Paylaod
> > > +--+--------------+----------------+-----------  --+----------
> > >
> > > +--+--------------+----------------+-----------  --+----------
> > > |10|    length    |      type      |48 bits src  ~ | Paylaod
> > > +--+--------------+----------------+-----------  --+----------

in case "10" you're exaclty at the bandwidth-consumtion where MPE is
(well +/- 2 byte per PDU)

also it's a point to discuss if you need all the fields in the MPE
header - but at least it's a start, after having the requirements
to go from (probably most of the people wouldn't be happy with the
MAC address layout in the MPE header ...)

	++Thomas

-- 
in some way i do, and in some way i don't.