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[802.3BA] PHY nomenclature letters


There has been a lot of discussion over comment #255 
that Brad submitted against IEEE P802.3ba D2.1 in relation to consistent 
use of nomenclature letter. Due to this I tried to record where I think we 
are in respect to PHY naming in IEEE 802.3, I have attached this 
information at the end of this email and summarized in the attached pdf.

Based on this I'd say that I do not believe we have ever been particularly 
consistent with PHY nomenclature from project to project - and instead we 
have 'evolved' it where we agree there is a need to do so - which I think 
is reasonable. For example we moved from just indicating media ('F' for 
fibre) in 100 Mb/s to wavelength ('S' and 'L' for short and long 
wavelength) in 1 Gb/s since we had more than one fibre PHY. Further we 
have allowed a nomenclature letter to have different meaning dependant on 
position ('S' and 'L' mean short and long reach as a second letter where 
encoding is not indicated). What however I do not believe we have ever 
done is create what I will characterise as a conflicting definition - 
where the same letter in the same position means something different.

Based on the above I believe that comment #255 points out that IEEE 
P802.3ba will result in a conflicting definition in IEEE 802.3. I believe 
that this is acknowledged in IEEE P802.3ba D2.1 subclause 80.1.4 
'Nomenclature' since it states the existing IEEE Std 802.3-2008 meaning, 
then redefines the meaning for 40Gb/s and 100Gb/s, of the first letter 
'S', 'L' and 'E' (from Short, Long and Extra long Wavelength to Short, 
Long and Extra long Reach).

In respect to the suggested remedy, to change 100GBASE-ER4 to 100GBASE-HR4 
using 'H' to indicate high-power (or higher sensitivity) long wavelength, 
while not in conflict with what has been done in the past, would I believe 
evolve what the first letter has been used for up to now (Media or 
Wavelength) and I'm not personally convinced of the need to do that in 
this case.

Instead I suggest an alternative approach to the 100GBASE-ER4 PHY name. 
With the first letter after the dash based on either the Media or 
Wavelength the 'E' should be changed to an 'L' as it is a 1310 nm (long 
wavelength) based solution. The second letter either indicates encoding 
or, if encoding is not indicated, reach. Based on this I believe it should 
remain 'R'. This would result in no differentiation between this 40 km PHY 
and the 10 km single mode PHY so additional differentiation is required. 
In the IEEE 802.3ah project this was dealt with by adding a number (e.g. 
1000BASE-LX10), but we can't do this here as at speeds of 10Gb/s and above 
the number is used to indicate the number of lanes.

I therefore propose we add a third letter, possibly 'E' for extended 
reach. I propose this to partially address the concern the Task Force has 
that the market associates E with 40km which John D'Ambrosia pointed out 
to me. The 100GBASE-ER4 PHY would therefore be renamed 100GBASE-LRE4 PHY. 
Based on that I suggest that the comment can be entirely satisfied by two 

[1] Deleting the contents of subclause 80.1.4 'Nomenclature' that states 
that the meanings of S, L and E are being changed and making changes as 
required to align to this.
[2] Renaming the 100GBASE-ER4 PHY to be the 100GBASE-LRE4 PHY.

One final thought. We may not have done a fantastic job of formally 
recording what these letters and numbers actually meaning. As an example 
while we do state that in subclause 1.4.35 '10GBASE-L' that it is a '.. 
PMD specifications for 10 Gb/s serial transmission using long wavelength.' 
we don't actually ever say that 'L' as a first letter means Long 
Wavelength and as a second letter means Long Reach. I think that has 
contributed to a situation where there are some, including participants in 
IEEE 802.3, that are of the opinion, for example, that Long reach, Long 
wavelength and the first letter 'L' are synonymous.

Moving forward there may be a benefit to recording the entire nomenclature 
but I believe that is out of scope of the IEEE P802.3ba project. I believe 
however that Wael plans to add an agenda item to the Maintenance Task 
Force to discuss this.

Best regards,

The following is a more detail description of what I show in the slides. 
With the exception of the FOIRL MAU (which is now deprecated) I'll break 
the naming down into three portions as follows:



n     is MAU/PHY data rate.
TYPE  is MAU/PHY modulation type.
ADD   is MAU/PHY additional distinction (which is broken down further 

n - data rate

This defines the data rate that the MAU/PHY can operate and consists of an 
integer followed conditionally by a multiplier. Where only one number is 
used the MAU/PHY operates at the same data rate both downstream and 
upstream, when two numbers are used separated by a forward slash the first 
number defines the downstream (from OLT to ONU) data rate, the second 
number defines the upstream (from ONU to OLT) data rate. Where the 
multiplier is not used the number(s) define(s) the data rate in Mb/s, 
where the optional multiplier is 'G' the number(s) define(s) the data rate 
in Gb/s. Data rates in use so far are:

2      2Mb/s
10     10Mb/s
100    100Mb/s
1000   1000Mb/s
10G    10Gb/s
10/1G  10Gb/s downstream, 1Gb/s upstream

Notes - (a) This is the data bit rate, not the Baud (encoded data) rate. 
(b) In the case of IEEE 802.3ah Ethernet in the First Mile copper PHYs 
this is the nominal maximum data rate since these PHYs can operate at 
multiple bit rates (see 2BASE-T and 10PASS-TS, Clause 61, 62 and 63). (c) 
I've included the designations added by IEEE P802.3av 10Gb/s EPON as the 
last recirculation just closed with 100% approval and no comments.

TYPE - modulation type

The modulation type indicates how encoded data is transmitted on the 
medium. Modulation types in use so far are:

BASE    Baseband
BROAD   Broadband
PASS    Passband

Notes - Before Hugh points it out I acknowledge that fibre optics MAU/PHYs 
are actually modulating a carrier of a few hundred THz - however lets not 
go there please :-)

ADD - Additional distinction

There are two basic formats that the additional distinction can take. The 
first, which is a legacy format, consists simply of a number after the 
modulation type. This format can be summarized as (m). The second consists 
of a dash followed by one to three letters, conditionally a number, 
conditionally a dash and a letter, then conditionally a number. This 
format can be summarized as (-LLLm-Eo). These are both described in more 
detail below:

m format additional distinction

Where the additional distinction consists of digits directly after the 
modulation type the digits define the maximum segment length, rounded up 
to the nearest 100 meters, divided by 100 meters. An example is 10BASE2 
which has a maximum segment length of 185 meters. This is a legacy format 
that was only used for 10Mb/s Coax MAUs.

-LLLm-Eo  format additional distinction

Where the additional distinction starts with a dash there will follow a 
minimum of one, and up to three, letters. The meaning of the letters are 
position dependant and those in use today are defined as follows:

First letter (media or wavelength)

B  Bidirectional optics 
C  Twin axial copper
E  Extra long wavelength (1550nm)
F  Fiber
K  Backbone
L  Long wavelength (1310nm)
P  Passive optics
S  Short wavelength (850nm)
T  Twisted pair

Second letter (reach or PCS encoding)

B  Backbone
L  Link (10BASE-FL), Long reach (2BASE-TL)
P  Passive optics
R  Scrambled coding (64B66B)
S  Short reach
W  WAN coding (SONET/SDH)
X  External sourced coding (block coding included by reference, 4B5B, 

Third letter

M  Multimode
X  External sourced coding (block coding included by reference, 4B5B, 

Where two encoding are included the first letter represents the downstream 
encoding, and the second letter represents the upstream encoding. An 
example is 10/1GBASE-PRX-D1 where 64B66B scrambled encoding is used 
downstream while 8B10B block encoding is used upstream.

For optical PHYs where the data rate is 1000 Mb/s or less, if number (m) 
is present, it represents the maximum segment length in km. For Twisted 
pair PHYs where the data rate is 100 Mb/s, if number (m) is present, it 
represents the number of pairs used. Where the data rate is 10Gb/s or more 
the number (m) represents the number lanes, the absence of a number 
indicating single lane operation. Examples are 100BASE-LX10 which has a 
maximum segment length of 10 km, 100BASE-T4 which operates over 4 pairs 
and 10GBASE-LX4 which operates over four lanes.

For asymmetrical PHY types the dash and letter (-E) indicates if the PHY 
is a network-end (OLT, Central office) or subscriber-end (ONU) PHY. The 
values currently used to indicate the end are:

D  Downstream (OLT)
U  Upstream (ONU)
O  Central Office
R  Subscriber

For Passive optical PHY types that support multiple optical power budgets 
the number (o) attached to the end indication indicates which of the power 
budget the PHY supports. The values currently used to indicate the power 
budget are:

1  10 km and a split ratio of at least 1:16
2  10 km and the split ratio of at least 1:32
3  20 km and a split ratio of at least 1:32

Note - The PCS and PMD family names based on use of either the first or 
second letter. Examples are 10GBASE-L for 10Gb/s long wavelength PMD 
family and 10GBASE-R for 10Gb/s scrambled encoding PCS family.

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