Thomas Norten pointed out to authors that <draft-ietf-ipngwg-1394-00.txt>
doesn't clearly describe if the MCAP (Multicast Channel Allocation
Protocol) is required (MUST) or not.
Since IEEE1394 has only 63 channels for multicast, both IPv4 over IEEE1394
(RFC2734) and IPv6 over IEEE1394 define all multicast addresses MUST be
share single broadcast channel by default. The intention of MCAP
is to split high rate data traffic from the default broadcast channel.
For this reason, RFC2734 says 224.0.0.1 and 224.0.0.2 MUST use broadcast
channel.
>From RFC2734 (IPv4 over IEEE 1394) "9. IP MULTICAST":
| By default, all best-effort IP multicast SHALL use asynchronous
| stream packets whose channel number is equal to the channel field
| from the BROADCAST_CHANNEL register. In particular, datagrams
| addressed to 224.0.0.1 and 224.0.0.2 SHALL use this channel number.
| Best-effort IP multicast for other IP multicast group addresses may
| utilize a different channel number if such a channel number is
| allocated and advertised prior to use, as described below.
Similarly, we, authors, would like to change the text of IPv6 over IEEE1394
as follows:
| 9. IPv6 MULTICAST
|
| By default, all best-effort IPv6 multicast MUST use asynchronous
| stream packets whose channel number is equal to the channel field
| from the BROADCAST_CHANNEL register. In particular, datagrams
| addressed to all-nodes multicast addresses, all-routers multicast
| addresses, and solicited-node multicast addresses [AARCH] MUST use
| the default channel specified by the BROADCAST_CHANNEL register.
|
| Best-effort IPv6 multicast for other multicast group addresses may
| utilize a different channel number if such a channel number is
| allocated and advertised prior to use, by a multicast channel
| allocation protocol (MCAP), as described in [IP1394]. The
| implementors are encouraged to use this protocol when transmitting
| high-rate multicast streams. When a node wishes to receive multicast
| data addressed to other than all-nodes multicast addresses, all-
| routers multicast addresses, and solicited-node multicast addresses,
| it MUST confirm if the channel mapping between a multicast group
| address and a channel number exists using MCAP, as described in "9.3
| Multicast Receive" in [IP1394].
|
| The MCAP 'type' value for IPv6 group address descriptor is {to be
| assigned by IANA}.
Comments?
Atsushi Onoe
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