Subject: Re: Unit_Sw_Version

From: "Allison, Art" <[email-masked]>
Date: Wed, 20 Jan 1999 16:00:42 -0500

Well to me it looks like it is too late for a unified unit_directory
approach.  The EIA 775 standard (which is based on/uses IEC 61883) has its
own unit directory in addition to the IEC_61883 unit directory in the config
ROM. The LSB of the unit_sw_version specifies AV/C per 61883[5]. OpenCable
uses the EIA directory, so products in the small part of the world known as
North America will have at least three unit directories when they implement
IP/1394 as well, as IP is NOT supported in EIA 775.
Also, FYI, the SCTE standard(s 194/195) documenting the OpenCable approach
calls out the work being done here as normative even though it is not
completed.
The SCTE standards have been adopted but have "No: votes to be resolved.
EIA 775 is final and is available from Global.
The train has left the station, lets finish building it... ( grin )
Art
::{)
-----Original Message-----
From: Joseph Joy [mailto:[email-masked]]
Sent: Friday, January 15, 1999 12:56 PM
To: [email-masked]
Subject: Re: Unit_Sw_Version

The larger issue than the specific choice for Unit_Sw_Version, is whether to
have a single unit directory for all protocols that are implemented on the
node, as I am proposing, or whether to have one unit directory for each
protocol (or each ether type). Clearly if we are to have a single unit
directory per nodde, it does not make sense to base the Unit_SW_Version on
EtherType or any other protocol-specific entity.

As far as the choice of the Unit_SW_Version, the fundamental constraint is
that the combination of Unit_Spec_ID and Unit_SW_Version *must* be globally
unique. Obviously, to be rigorous about this, the ip/1394 working group can
not unilaterally come up with a value for Unit_Spec_ID, because it would be
impossible to guarantee that it is unique with respect to all of IANA.

I strongly favor a single "1394 networking device" unit directory per
physical node, for the following reasons:
1. Having a single unit directory per node simplifies the plug'n'play
process on systems which create one internal device object per unit
directory.
2. Each unit directory typically represents a logical device -- a drive, a
scanner, and so on. Associating a unit directory with each packet type
(IPv4, IPv6, MCAP, ARP and so on), or each network protocol that is
implemented on the node does not fit into this model. On the other hand,
having a single unit directory to represent a logical network device on the
node *does* fit into this model. As I suggest in the proposal, any
protocol-specific information may be included within this unit directory,
either as immediate entries or as leaf entries.
3. In general it is good to minimize the number of unit directories as well
as the total size of the config rom. Larger crom space means longer
enumeration times which degrades the pnp experience and make the system less
responsive. By just using leafs or even better direct offsets, you save
space on a system implementing more than one prototocol/EtherType.

Joseph.

-----Original Message-----
From: Hattig, Myron [mailto:[email-masked]]
Sent: Wednesday, January 13, 1999 10:12 AM
To: [email-masked]
Subject: Unit_Sw_Version

We have two options discussed for the value of the Unit_SW_version
in the IP/1394 Unit Directory.

Joseph - thanks for the complete proposal!! - suggested we have
the IANA define a new group of numbers then rely on the IANA to
allocate numbers. Others have suggested simply using the EtherType.

We have already agreed to use the IANA's value for the Unit_Spec_id.

The IANA allocates IP addresses, domain names and protocol parameters.
I don't know if the IANA would be willing consider the Unit_Sw_Version
a protocol parameter or not, but based on the current set of numbers,
I suspect they would be willing. The complete list of protocol numbers is
at http://www.iana.org/numbers.html.

I don't have a strong opinion, but since the EtherType meets all
of our current and future needs - it identifies IPv4, IPv6, ARP, MCAP
- I don't see any benefits in bothering IANA.

-myron