Re: Multicast Query

[Gorry Fairhurst <gorry@erg.abdn.ac.uk>]

Krishna Vora wrote:
> Hi,
>
> I would like to have some information regarding use of Multicast IP for
> a DVB-S Set Top Box scenario. Is the STB user required to first contact
> some network centre to be a part of a multicast group. 
> Similarly how is the multicast MAC addressing done?

In ULE the rules for multicast MAC addressing are described in section 4.5,

" 4.5 SNDU Destination Address Field

   The SNDU Destination Address Field is optional (see section 4.1).
   This field MUST be carried (i.e. D=0) for IP unicast packets
   destined to routers that are sent using shared links (i.e., where
   the same link connects multiple Receivers). A sender MAY omit this
   field (D=1) for an IP unicast packet and/or multicast packets
   delivered to Receivers that are able to utilise a discriminator
   field (e.g. the IPv4/IPv6 destination address), which in combination
   with the PID value, could be interpreted as a Link-Level address.

   When the SNDU header indicates the presence of a SNDU Destination
   Address field (i.e. D=0), a Network Point of Attachment, NPA, field
   directly follows the SNDU Type Field.  NPA destination addresses are
   6 Byte numbers, normally expressed in hexadecimal, used to identify
   the Receiver(s) in a MPEG-2 transmission network that should process
   a received SNDU. The value 0x00:00:00:00:00:00, MUST NOT be used as
   a destination address in a SNDU. The least significant bit of the
   first byte of the address is set to 1 for multicast frames, and the
   remaining bytes specify the link layer multicast address. The
   specific value 0xFF:FF:FF:FF:FF:FF is the link broadcast address,
   indicating this SNDU is to be delivered to all Receivers. "

The draft is available from:

http://www.ietf.org/internet-drafts/draft-ietf-ipdvb-ule-03.txt

Gorry