On Fri, 03 Dec 2004 09:22:02 +0000
Gorry Fairhurst <gorry@erg.abdn.ac.uk> wrote:
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?
Multicast group address allocations are described by rfc3171 (and its references)
http://www.ietf.org/rfc/rfc3171.txt
The 239/8 address range is analgous to 10/8 for unicast (i.e., these are internal addresses that can
be used freely as long as they don't leak out).
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 th
In IP multicast, there is a mapping between the IP Group address
of the multicast, and the MAC address. For example, in IPv4,
multicast MAC addresses start with 01:00:5E, followed by a zero bit, followed
by the low order 23 bits of the multicast group address. Was there a
specific reason why not to follow this ?
Regards
Marshall Eubanks