Hugh,
I don't really understand your 3+1 option.
In my view the criteria shall be as follows:
Suppose you have the following system configuration:
[Smartbits]----10BaseT----[EFMCu CO]----2BaseTL-----[EFMCu
RT]----10BaseT---[Smartbits]
ifSpeed=10Mbps ifSpeed=10Mbps ifSpeed=10Mbps
If the EFMCu link reports its ifSpeed as 10Mbps, provided that the MAC
bridge in the EFMCu CO and RT is wire-speed, there should be no packet loss
when I fire the Smartbits in full duplex 10Mbps 100% with min IFG with frame
length of 64 Bytes and 1518 Bytes.
It looks to me that option 3, i.e. sum of modem data rates without 64/65B
encapsulation and PAF overhead but with IFG, answers this criteria best.
The reported ifSPeed may not be super accurate, the error however should
always be positive, i.e. no possible packet loss in the configuration above.
Obviously option 2 (goodput) would work as well.
Regards,
-E.
-----Original Message-----
From:
owner-stds-802-3-efm@listserv.ieee.org on behalf of Hugh Barrass
Sent: Tue 8/3/2004 7:48 AM
To:
STDS-802-3-EFM@listserv.ieee.org
Cc:
Subject: Re:
[EFM] ifSpeed & 2BASE-TL/10PASS-TS
Matt,
I would go with 3) plus 1) - reasons:
0)
is just plain wrong!
1) The aggregated links appear to the MAC and
upper layers as a single
link. The aggregated link speed governs the rate
across the MII.
2) We've never accounted for "goodput"
before
3) That's how we have done it for all other PHYs. The overhead
of
encapsulation is absorbed by the link running at a faster rate than
the
MII (whether it's 4b5b, 8b/10b or 64b/66b). But the effect of the
IPG
depends on the frame size, so is ignored.
So, I think it
should be the aggregate rate at the MII for an imaginary,
infinite length
frame.
Hugh.
Matt Squire wrote:
>I figured I'd fire
off a note to the reflectors to get this discussion
started.
>
>During the discussions today in the hubmib WG, the
question arose as to what should be the ifSpeed for 2BASE-TL & 10PASS-TS
interfaces.
>
>Traditionally, it seems the ifSpeed has been tied
to the speed of the MAC (e.g. 10Mbps, 100Mbps, etc.). With
2BASE/10PASS, the PHY may be running at a much lower speed than the 100Mbps
MAC, so its not particularly useful to the administrator to call all of
these interfaces 100M when the PHYs aren't there.
>
>Options for
ifSpeed of 2BASE/10PASS seem to include the following:
>
>0) Use
100 Mbps (MAC speed).
>
>1) Sum the physical date rates of PMEs
in the aggregate (PHY speed).
>
>2) Use the rate of "goodput" on
the PHYs (e.g. how much data can ge thru). This would ignore any
overhead of the PHY (PAF, 64/65) and overhead of the MAC (preamble,
IPG). This most accurately reflects how much data can get
thru.
>
>3) Use the rate at the MAC/MII. E.g. include
preamble/IPG (even though its not transmitted), but not PHY overhead (PAF,
64/65). This seems consistent with other PHYs, but is kinda weird in
that we're not actually transmitting preamble/ipg.
>
>There are
probably other options too. Thoughts/opinions?
>
>-
Matt
>
>
>