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

[Lloyd Wood <l.wood@eim.surrey.ac.uk>]

On Wed, 24 Apr 2002, Patrick Cipiere wrote:

> Gorry wrote:
>
> > Just to be sure... A small payload will normally be padded to the
> > Ethernet Minimum frame size - this involves sending padding bytes to
> > make the frame >= 64B (incl 4B FCS).
>
> Got the point.
> My understanding: the padding is only needed at the physical layer, so
> I think in our design there is no use to add padding because in this
> case ethernet is not at the physical layer.

you might want to take a look at the martini drafts in mpls/pwe3,
which have been making a Big Thing of the ethernet padding.

draft-martini-l2circuit-encap-mpls has a fixup length field to cater
just for this, rather than having a sensible per-payload length field:

   The next 6 bits provide a length field, which is used as follows: If
   the packet's length (defined as the length of the layer 2 payload
   plus the length of the control word) is less than 64 bytes, the
   length field MUST be set to the packet's length. Otherwise the length
   field MUST be set to zero. The value of the length field, if non-
   zero, can be used to remove any padding. When the packet reaches the
   service provider's egress router, it may be desirable to remove the
   padding before forwarding the packet.

lots of heated discussion of this on the pwe3 list.

L.

> mpeg2, MPE and the new design will have their own padding if needed.
>
> Patrick.
> --
> UDcast: Full IP over Broadcast Media
>
> Phone:  (+33) (0)4 93 00 16 99
> Mobile: (+33) (0)6 14 21 55 98
> Fax:    (+33) (0)4 93 00 16 61                 http://www.UDcast.com
>

<L.Wood@surrey.ac.uk>PGP<http://www.ee.surrey.ac.uk/Personal/L.Wood/>