Réf. : Re: Alcatel Space interest about IP/DVB

[Stephane.Combes@space.alcatel.fr]

Hi Horst,

Thanks a lot for your reviewing and comments !

By "Ethernet-like" we only mean "connectionless layer 2 based on broadcast
medium". Nevertheless we do not propose to re-use the addressing scheme of
Ethernet. As I said in my previous e-mail, using a label uniquely identifying a
"source" in a "subnet" may be enough and much more flexible for the systems we
target.

MPEG-2 layer would indeed be seen like ATM layer where PID would bear a
significance analogous to the VPI (aggregation of flows - but here from
different sources and towards several destinations - , first level of
filtering).
 It would indeed be very nice if a new link layer protocol could be transported
seamlessly over MPEG and ATM (very interesting for DVB-RCS systems which use
MPEG as forward link and ATM as return or mesh link).
The filtering performed at the level of this new link layer on top of MPEG would
be similar to MPE filtering (we do not need to have the MPE address in each TS
packet), at least for Gateway Terminals transmission (if we consider Gateways do
not share the same PID for emission). For user Satellite Terminals (sharing a
DVB-RCS access for instance), the additional label would indeed be included in
each TS (if we consider several such terminals share the same PID for emision).

As far as switching is concerned, only the PID would be used for such a purpose
(not the additional link layer label). For example, we could have a MPEG switch
on-board the satellite. And in such a case, we are very very limited by the PID
numbering space. Therefore this additional label would be needed.

So I guess we basically agree with you that Ethernet addressing is not the ideal
solution for networks other than Ethernet. But such proposal for a complete "MPE
replacement" (although trying to keep a similar filtering and re-assembly
process) would indeed only be justified for new systems. We propose to explore
this for multiple-feeds and "mesh" capable systems (allowing direct
terminal-to-terminal communication).

Does this clarify our requirements ?

Cheers,

Stéphane

ALCATEL SPACE INDUSTRIES
Research Department/Advanced Telecom Satellite Systems
Tel : +33 (0)53435 6938  /  Fax : +33 (0)53435 5560
Porte : F1027  /  E-Mail : stephane.combes@space.alcatel.fr