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RE: [802.3ae] Clarification on Clause 45




Devendra,

The design implication (for a STA or PHY) is very minor to differentiate
between a Clause 22 management frame and a Clause 45 management frame.  The
advantage to these schemes is that it provides STAs that wish to control
multiple PHY types to use existing Clause 22 managed PHYs and new Clause 45
managed PHYs with minor modification to the management protocol.  Those that
wish to develop PHYs that previously used the Clause 22 management interface
to use the Clause 45 management interface may do so, but that is beyond the
scope of the task force's PAR.  We did keep the primary registers (0, 1, 2
and 3) very similar between Clause 22 and 45 to decrease the impact on
management software.

Cheers,
Brad

Brad Booth
IEEE P802.3ae Editor-in-Chief

-----Original Message-----
From: Devendra Tripathi [mailto:tripathi@covisible.com]
Sent: Monday, April 22, 2002 7:52 PM
To: THALER,PAT (A-Roseville,ex1); David Law
Cc: stds-802-3-hssg@ieee.org
Subject: RE: [802.3ae] Clarification on Clause 45



Hi Pat,

> There isn't any reason to put the Clause 22 registers into the Clause 45
> register space. Reserved device addresses are a very limited resource and
> are reserved for future use such as the needs of future higher speed PHYs.
> One can of course do whatever one wants with the vendor specific devices,
> but as there are only two, I wouldn't use that scarce resource for
registers
> that already have a way to be accessed.

I am fine with that.

But isn't it worth having a path where the STA does not have worry about two
types of PHY access schemes ?

I think this issue will be faced by all mixed speed PHY vendors. Somehow it
seems odd that we would be enforcing the requirement of two access schemes
forever. Whereas the real intent of keeping Clause22 type addressing (that
is what I think), was to keep compatibility with legacy devices. Since 1G
and lower speeds registers are already defined, it makes sense to define a
way such that STA can access them as well as 10G specific device registers
using a single protocol (means write address, read/write data).

It seems so obvious that I feel, I am missing something here.

Regards,
Devendra Tripathi
CoVisible Solutions, Inc
90 Great Oaks Blvd #206
San Jose, Ca 95119
Tel: (408)226-6800,
Fax: (408)226-6862

-----Original Message-----
From: THALER,PAT (A-Roseville,ex1) [mailto:pat_thaler@agilent.com]
Sent: Monday, April 22, 2002 5:24 PM
To: Devendra Tripathi; David Law
Cc: stds-802-3-hssg@ieee.org
Subject: RE: [802.3ae] Clarification on Clause 45


Devendra,

As David pointed out, a device that has both 1 Gbit/s or lowerer PHY
capability and 10 G PHY capabiliity can respond to  both the Clause 22
register space and the Clause 45 register space. There would be no need to
put the Clause 22 registers into the Clause 45 register space. If the ST
bits are 01, then the clause 22 registers are addressed with the clause 22
frame structure. If the ST bits are 00, then the Clause 45 registers are
addressed with the Clause 45 frame structure.

Note that 802.3ae does not use or support autonegotiation so the
autonegotiation registers would only apply to the 1 Gbit/s (or lower speed)
PHY.

There isn't any reason to put the Clause 22 registers into the Clause 45
register space. Reserved device addresses are a very limited resource and
are reserved for future use such as the needs of future higher speed PHYs.
One can of course do whatever one wants with the vendor specific devices,
but as there are only two, I wouldn't use that scarce resource for registers
that already have a way to be accessed.

Pat Thaler

-----Original Message-----
From: Devendra Tripathi [mailto:tripathi@covisible.com]
Sent: Monday, April 22, 2002 4:09 PM
To: David Law
Cc: stds-802-3-hssg@ieee.org
Subject: RE: [802.3ae] Clarification on Clause 45



Thanks David,

The "orthogonality of address space" is clear now.

I would like to know what options I have if I want to use uniform Clause45
access and I have mixed PHY for 1G and 10G. Looks like the only option is to
put all Clause22 registers (including autonegotiation ones) in "Vendor"
device.

Please note that this becomes important because the Clause 45 device
definitions are not downward compatible (the bit definition are only for 10G
and above).

I would like to think of a better arrangement (a defined device which could
accomodate all these registers). Any thoughts ?

What about Device 0, (which is marked reserved right now) or 6 ?

Regards,
Devendra Tripathi
CoVisible Solutions, Inc
90 Great Oaks Blvd #206
San Jose, Ca 95119
Tel: (408)226-6800,
Fax: (408)226-6862

-----Original Message-----
From: David Law [mailto:David_Law@eur.3com.com]
Sent: Monday, April 22, 2002 1:52 PM
To: Devendra Tripathi
Cc: stds-802-3-hssg@ieee.org
Subject: Re: [802.3ae] Clarification on Clause 45




Hi Devendra,

I believe the simple answer is that the Clause 22 register would, as always,
be
put in the (10/100/1000Mb/s) PHY which they monitor/control. This could be a
totally separate PHY however Clause 45 makes the provision that these Clause
22
register could optionally be placed in the same package (the definition of
the
term package is vendor specific and could be a chip, module or other similar
entity) as one of the 10Gb/s Sublayers if the implementer so chooses. If,
for
example, a implementer manufactured a module that included a 10Gb/s PCS and
the
Clause 22 registers for a 1Gb/s PHY, as you suggest below, then that
implementer
would indeed set the Clause 22 registers present bit (bit 3.5.0) in the PCS
devices in package register. The implementer is of course free to implement
any
other combination they choose so long as the bit in the associated devices
in
package register are set correctly. It is also perfectly acceptable not to
'mix'
these devices and have a totally separate 10/100Mb/1000Mb/s PHY with its
associated the Clause 22 registers. In all cases these Clause 22 register
are
access using the Clause 22 Management Frame Format.

As far as the addressing is concerned, to open up additional address space,
and
to enable different vendors to supply the different sublayers that form a
single
port, a second 'layer' of addressing was added above that provided in Clause
22.
This additional 'layer' is called the Device Address. In addition, what was
called the PHY address in Clause 22 is called Port Address in Clause 45.
Hence
in Clause 22 the address consisted of the PHY Address + Register Address. In
Clause 45 the address consists of the Port Address + Device Address +
Registrar
Address. To differentiate between a Clause 22 access and a Clause 45 access
on
the MDC/MDIO signals, the Start of Frame pattern is 01 for a Clause 22
access
and 00 for a Clause 45 access. These two Start of Frame pattern provide two
totally non overlapping address maps.

I hope this helps.

Best regards,
  David Law







"Devendra Tripathi" <tripathi@covisible.com>@majordomo.ieee.org on
22/04/2002
17:15:54

Sent by:  owner-stds-802-3-hssg@majordomo.ieee.org


To:   <stds-802-3-hssg@ieee.org>
cc:
Subject:  [802.3ae] Clarification on Clause 45



Hi,

Could some one clarify which device to put Clause 22 registers in, if they
are present?

If the answer is that they need to be mixed in specific device (say PCS),
how should one map the 16 registers of Clause 22 (including autonegotiations
ones). In this case, I presume, I need to set the bit 0 of register 5 of the
given device (say PCS) to '1'.

Also, when we say (D4.3, page 185, line 9) that MDIO address space is
orthogonal to MII register space, it is not clear how it is so.  Could
someone explain that ? As I see it, we have replaced device address by port
address and register address by device address. But this by itself, does not
make it orthogonal (unless we say that a fixed device, say, device 0 on any
port is defined as MII device).

Regards,
Devendra Tripathi
CoVisible Solutions, Inc
90 Great Oaks Blvd #206
San Jose, Ca 95119
Tel: (408)226-6800,
Fax: (408)226-6862