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RE: [EFM] 1 Gbps != 999.9 Mbps


Thank you.  I will remember what you have said.

My confusion is how can a "repeater/hub" be a manageable "system" and not 
have 802.1 functionality?  Please see the attached product sheet that was 
downloaded from a public web site.  Perhaps there needs to be a "little" 
more granularity to the terms "hub" and "repeater".  I would argue that the 
term "repeater", as a "system", carries with it the connotation that it 
does not have any 802.1 functionality and thus can not be managed through 
the Ethernet MAC.  I would also argue that a "hub", as a "system", in order 
to have management capability, would have 802.1 functionality in order to 
be managed through the Ethernet MAC.  Perhaps this is not currently the 
technically correct usage, but we are about to get into an area of 
"systems" definitions for subscription services support in which the 
currently technically correct usage is now inadequate.  In order to 
preserve the existing "terminology" new terms need to be agreed on.

In the transmission world the term "Customer Service Unit" (CSU) refers to 
a "system" that "repeats" the full duplex customer revenue data stream, 
while being "managed" though the "out-of-band" overhead by the service 
provider.  What ever it is called, EFM needs to standardize on PHYs that 
such "systems" could be built from.

Thank you,
Roy Bynum

At 07:07 AM 9/28/01 +0100, Tony Jeffree wrote:
>Roy -
>I can see where your confusion comes from, if what you do is to use the 
>marketing information on products as your basis for an understanding of 
>what these terms mean, rather than going to the standards that define them 
>and then trying to understand what is in the products.  Let me give you an 
>There is a product, manufactured for the SO/HO market by one of the usual 
>names in Ethernet equipment, that my local networking supplier describes 
>as an "8-port, 10/100 Hub". (Actually, there are a number of manufacturers 
>that build similar devices.) Now, we know from Std 802 that a hub is a 
>multi-port repeater designed for star-wired network cabling, so it is a 
>shared medium (half-duplex) device. And we know from the 802.3 specs that 
>you cannot mix 10 megs and 100 megs on the same shared medium. So what is 
>going on here? On the face of it, this device cannot exist, as its spec 
>claims to offer mix-and-match, auto sensing, 10 or 100 megs on each of its 
>8 ports.
>Look further at the product spec for this device, and it says that the hub 
>has Bridge functionality that will do address filtering between 10 megs 
>ports and 100 megs ports. So what is really going on in this particular 
>device is that, logically, it consists of three major components:
>- An 8-port 10 megs hub (i.e., a shared medium 8-port 10 megs repeater);
>- An 8-port 100 megs hub (i.e., a shared medium 8-port 100 megs repeater); and
>- A 2-port Bridge connecting the two hubs together (so actually, the hubs 
>have 9 ports, with one port on each hub permanently connected to the bridge).
>So this "box" consists of three separate standardized functions, and there 
>is no recognized, standardized name for the combination. The nearest 
>match, from the marketing viewpoint, is to call it a hub (repeater), as 
>the external ports are all attached to half duplex, shared medium LAN 
>segments, and the delivered functionality is therefore understandable. 
>However, as it also incorporates a bridging function, it is not a hub 
>according to the way that term is defined in 802 - it is 2 hubs and a 
>bridge that happen to have been packaged in the same box, and which happen 
>to be able to share the same set of 8 external RJ45 connectors. From the 
>manufacturers' point of view, it may well be easier to call it a hub than 
>it is to go through a more standards accurate description for the benefit 
>of the relatively small percentage of customers that would actually 
>understand or care about the difference.
>Moral: If you don't want to get confused (or confuse others) in a 
>standards forum, or if you simply don't want to remain "just an ignorant 
>customer" (your words, not mine!), it is a very smart move to base your 
>terminology on the definitions contained in the standards that that forum 
>uses/develops, rather than on the marketing information written by 
>companies that develop products based on those standards.
>At 22:38 27/09/2001 -0500, Roy Bynum wrote:
>>I am just an ignorant customer.  When I go to a computer store and buy a 
>>"hub", what I get is 802.1d bridge that has half duplex Ethernet 
>>ports.  I have an old "hub" that I got from a just such a store.  The box 
>>claims 802.1d bridge support.  Perhaps I am guilty of using the 
>>vernacular meanings of some terms.  But then, I am just a customer.
>>Thank you,
>>Roy Bynum
>>At 10:51 PM 9/27/01 -0400, Vladimir Senkov wrote:
>>>Absolutely agree.
>>>I didn't want to repeat myself (here and was trying to do that via 
>>>personal e-mails), but i guess I just have to say that those who test they:
>>>1) Test equipment vs. technology
>>>2) Know what they are testing and what they are expecting as a result
>>>Those who sell testing equipment:
>>>1) Also sell methodologies, training and certification.
>>>2) Some of those methodologies are in the RFCs. There are other 
>>>standards for that as well.
>>>Those who sell equipment:
>>>1) Tell customers exactly what they are selling
>>>2) No matter how much they want otherwise, they are going to sell the 
>>>EFM, but not the "pure 1G story"
>>>EFM needs to address specific needs of those who are going to buy it.
>>>Those needs may include: delivering data, video, voice, whatever . . . 
>>>to whatever distance, concentration of users, etc. Those needs may 
>>>include: security, pricing, etc, etc.
>>>but not just "1G". "1G" is not a need. it is more like a sign on a 
>>>freeway or something . . .
>>>let's say "upto 1G". even with OAM in-band, it will still be "upto 1G".
>>>I'll also repeat that Ethernet performance (to the end user anyway) is 
>>>NOT measured in bits per second. And nobody is selling 10Mbps 
>>>repeaters/hubs (yes hub IS a repeater :) for example. They sell Ethernet 
>>>hubs instead.
>>>Therefore, customer who buys such a hub knows that he is not going to 
>>>sue the seller for not delivering 10Mbps. Customer will only expect 
>>>performance characteristics of that device to be tested against Ethernet 
>>>performance measurement methodologies.
>>>-----Original Message-----
>>>From: Andrew Smith 
>>>Sent: Thursday, September 27, 2001 10:21 PM
>>>To: Roy Bynum
>>>Cc: 'stds-802-3-efm'
>>>Subject: RE: [EFM] 1 Gbps != 999.9 Mbps
>>>I'd be interested to see how you propose measuring one of your
>>>802.3x-pause-rate-limited services against one of these "certification"
>>>testers. But seriously, folks, to paraphrase that doctor-patient story
>>>"Patient: Doctor, it hurts when I sell my customers 1000000000.0000 bps
>>>service. Doctor: then don't sell them that, sell them what you can
>>>Andrew Smith
>>>-----Original Message-----
>>>Behalf Of Roy Bynum
>>>Sent: Thursday, September 27, 2001 4:36 PM
>>>To: bob.barrett@xxxxxxxxxxxxxxx; Harry Hvostov; fmenard@xxxxxxxxxxxxxxx;
>>>'Denton Gentry'
>>>Cc: 'stds-802-3-efm'
>>>Subject: RE: [EFM] 1 Gbps != 999.9 Mbps
>>>You would be surprised at how little bandwidth loss it takes for equipment
>>>to fail certification in a services infrastructure deployment approval
>>>process.  If we tell our customers that we are delivering a GbE, then we
>>>deliver a GbE that will pass their most rigorous performance test,
>>>including throughput.
>>>Thank you,
>>>Roy Bynum
>>>At 12:11 AM 9/28/01 +0100, Bob Barrett wrote:
>>> >Harry et al
>>> >
>>> >yup, all the IP 'stuff' is payload as far as the demarcation point is
>>> >concerned.
>>> >
>>> >The demarc is a PHY that carries packets at the end of the day. Some
>>> >may be buried inside a bigger system, however, the standard must also 
>>> cater
>>> >for stand alone demarc devices. My expectation as a user would be that at
>>> >the demarc the bandwidth was the same capacity as my enterprise MAC 
>>> and PHY
>>> >of the same spec.
>>> >
>>> >Would I miss 10k per second on a 1GE, I doubt it.
>>> >
>>> >Would my test gear pick it up on an end to end private circuit test, I
>>> >know, anyone on the reflector tried this?
>>> >
>>> >Bob
>>> >
>>> > > -----Original Message-----
>>> > > From: Harry Hvostov 
>>> [<mailto:HHvostov@xxxxxxxxxxxx>mailto:HHvostov@xxxxxxxxxxxx]
>>> > > Sent: 27 September 2001 17:41
>>> > > To: 'fmenard@xxxxxxxxxxxxxxx'; 'Denton Gentry';
>>> > > bob.barrett@xxxxxxxxxxxxxxx
>>> > > Cc: 'stds-802-3-efm'
>>> > > Subject: RE: [EFM] 1 Gbps != 999.9 Mbps
>>> > >
>>> > >
>>> > > And how about the ICMP and IGMP traffic from the same CPE devices?
>>> > >
>>> > > Harry
>>> > >
>>> > > -----Original Message-----
>>> > > From: Francois Menard 
>>> [<mailto:fmenard@xxxxxxxxxxxxxxx>mailto:fmenard@xxxxxxxxxxxxxxx]
>>> > > Sent: Thursday, September 27, 2001 6:05 AM
>>> > > To: 'Denton Gentry'; bob.barrett@xxxxxxxxxxxxxxx
>>> > > Cc: 'stds-802-3-efm'
>>> > > Subject: RE: [EFM] 1 Gbps != 999.9 Mbps
>>> > >
>>> > >
>>> > >
>>> > > Or for that matter, what about ARP traffic unsolicited from my CPE
>>> > > devices ?
>>> > >
>>> > > -=Francois=-
>>> > >
>>> > > -----Original Message-----
>>> > > From:
>>> > > 
>>> [<>] 
>>> On Behalf Of Denton
>>> > > Gentry
>>> > > Sent: September 26, 2001 3:12 PM
>>> > > To: bob.barrett@xxxxxxxxxxxxxxx
>>> > > Cc: stds-802-3-efm
>>> > > Subject: [EFM] 1 Gbps != 999.9 Mbps
>>> > >
>>> > >
>>> > >
>>> > > > Service providers have a desire to offer a full 1GE service and not
>>> > > > use any of it's bandwidth for OAM. The rule of conservation of
>>> > > > bandwidth means the OAM needs to go somewhere other then in the
>>> > > > bandwidth reserved for the 1GE payload. I take it as read that 100%
>>> > > > utilisation of a 1GE is unlikely, but that is not the point. The 
>>> point
>>> > >
>>> > > > is that service providers want to offer 1GE service period, not a
>>> > > > 999.9Mbit service.
>>> > >
>>> > >   Does the existence of the Mac Control PAUSE frame therefore make
>>> > > Ethernet unsuitable for service providers?
>>> > >
>>> > > Denton Gentry
>>> > > Dominet Systems