Subject: [IP1394]Fwd: [1394-net] Multicast on 1394? IP on 1394?

From: Peter Johansson <[email-masked]>
Date: Fri, 02 May 2003 12:27:51 -0700

>From: [email-masked]
>Subject: [1394-net] Multicast on 1394? IP on 1394?
>To: [email-masked], [email-masked], [email-masked]
>Date: Fri, 2 May 2003 14:18:56 -0500
>
>I looked at this some time ago and thought that you could not do multicast
>over 1394. Is this true? If not, how (briefly) do you do a multicast
>message?
>
>Also, I know that IP over 1394 has been developed and is supported by
>multiple vendors. at one time there were more than one solution to this. I
>don't know that the solutions were inter-operable. Has the industry settled
>upon a method for interoperability? Where can I find a brief description of
>this implementation?
>
>Thanks.
>
> >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
>Greg Arundale, Principal Computer Architect
>Rockwell Collins, Advanced Technology Center
>400 Collins Rd. NE, M/S 108-206
>Cedar Rapids, IA 52498
>Phone: 319-295-4097, FAX: 319-295-2005
>mailto:[email-masked]

---

From: Peter Johansson <[email-masked]>
Date: Fri, 02 May 2003 16:54:32 -0700

At 02:18 PM 5/2/2003 -0500, [email-masked] wrote:

>over 1394. Is this true? If not, how (briefly) do you do a multicast message?

No, it's not true. Stream data, whether asynchronous or isochronous, is 
inherently broadcast and therefore suited to multicast. At the highest 
level, the channel number (zero to 63) is used to multiplex the data flows: 
simply tell members of "your" multicast group the channel number to which 
they should listen. If the data flow is on a well-known channel, i.e., the 
default broadcast channel (31), data flows are additionally multiplexed by 
a 64-bit identifier that precedes the data.

>don't know that the solutions were inter-operable. Has the industry 
>settled upon a method for interoperability? Where can I find a brief 
>description of this implementation?

IP datagrams intended for multicast group addresses are broadcast in global 
asynchronous stream packets (GASP) and are therefore received by all 
IP-capable nodes. Additional information in each GASP multiplexes the data 
flows for particular multicast groups. RFC 2734 contains a complete and 
interoperable specification of these multicast methods.

Although the preceding is true for multicast data flows that use default 
quality of service (QoS), the industry has yet to agree upon a common 
method to identify multicast data flows that merit a higher QoS. This is a 
challenge that is not limited to IP1394---it also affects other media, such 
as Ethernet. What are needed are higher-level, IP-based protocols to 
identify such streams. Should such protocols exist and become widely 
implemented, RFC 2734 already contains methods to map high-quality 
multicast data flows to Serial Bus isochronous streams. At present, these 
IP1394 capabilities go unused because of the lack of the higher-level 
protocols.

Regards,

Peter Johansson

Congruent Software, Inc.
98 Colorado Avenue
Berkeley, CA  94707

(510) 527-3926
(510) 527-3856 FAX

[email-masked]