RE: Issues concerning 10GbE speed standards
- To: Drew Perkins <drew.perkins@xxxxxxxxxxxx>
- Subject: RE: Issues concerning 10GbE speed standards
- From: "David Martin" <dwmartin@xxxxxxxxxxxxxxxxxx>
- Date: Mon, 28 Jun 1999 13:33:35 -0500
- Cc: "'stds-802-3-hssg@xxxxxxxx'" <stds-802-3-hssg@xxxxxxxx>
- Sender: owner-stds-802-3-hssg@xxxxxxxxxxxxxxxxxx
If everything is kept equal (i.e. line rate, SNR, BER), then the issue of
8B/10B encoding vs schemes
with a longer run length (e.g. scrambled) is more one of design choices
rather than design cost. The
DC balance, digital sum variance and run lengths of a pattern impact the RX
design in two ways.
1) Data recovery: The shorter the pattern length (e.g. 10 bits), the
higher you can choose the lower cutoff
frequency of the RX passband. This means the capacitor has to be
well-behaved over a narrower range
of frequencies (its upper performance end needs to be at about half
the line rate). The selection of the
capacitor value and type must be done carefully, but this isn't a
cost issue.
2) Clock recovery: The shorter the run length of all zeroes/ones, the
less inertia or lower Q value required
by the RX to extract a clock. The lower the Q value, the more input jitter
can be tolerated and thus the more
jitter that the TX can be allowed to generate. The design value of Q, again
translates to choices in
component values (for the RX PLL). A relaxed jitter generation spec on the
TX may relieve some packaging
performance constraints, but in volume the associated cost differences tend
to wash out.
If the line rate is now 25% higher from a baseline of 10G, although this is
still within the same technology
realm, there will be a cost penalty due to lower yield of the electro-optics
module & electro-optics interface
components. How substantial this delta would be I leave to the parts
suppliers out there to answer.
...Dave
David W. Martin
Nortel Networks
+1 613 765-2901
+1 613 763-2388 (fax)
dwmartin@xxxxxxxxxxxxxxxxxx
========================
-----Original Message-----
From: Drew Perkins [SMTP:drew.perkins@xxxxxxxxxxxx]
Sent: Monday, June 28, 1999 1:11 PM
To: 'nuss@xxxxxxxxxx'
Cc: Paul Bottorff; 'Peter_Wang@xxxxxxxx'; 'rabynum@xxxxxxxxxxx';
'stds-802-3-hssg@xxxxxxxx'
Subject: RE: Issues concerning 10GbE speed standards
Martin,
I really like your point 4. It's the same argument I was
using about
the WAN. I suspect that your points 1 and 3 are correct too, but
they depend
a lot on point 2. That's where there is still some question in my
mind and I
think we ought to focus. Can some people who are more expert than
myself
please comment on the cost penalties for not having a balanced code?
If you
assume the same raw baud/bit rate (after coding), then how much less
expensive is 8B/10B because it's balanced? Now if you factor in the
coding
inefficiency penalty (i.e. you raise the baud/bit rate for 8B/10B by
25%),
how are the costs affected?
Drew
---------------------------------------------------------
Ciena Corporation Email: ddp@xxxxxxxxxxxx
Core Switching Division Tel: 408-865-6202
10201 Bubb Road Fax: 408-865-6291
Cupertino, CA 95014 Cell/Pager: 408-829-8298
-----Original Message-----
From: Martin Nuss [mailto:nuss@xxxxxxxxxx]
Sent: Monday, June 28, 1999 8:20 AM
To: Drew Perkins
Cc: 'Paul Bottorff'; 'Peter_Wang@xxxxxxxx'; 'rabynum@xxxxxxxxxxx';
'stds-802-3-hssg@xxxxxxxx'
Subject: Re: Issues concerning 10GbE speed standards
All,
I think we are making a mistake by talking about scrambling in the
WAN
and 8B/10B in the LAN. There are a lot of good reasons why we need
to
look at scrambling in the LAN as well:
1) a serial 10-Gig solution is definitely going to be the cheapest
one
by the time 10G Ethernet sales seriously take off. That is true in
the
LAN as well. You do not want to exclude an option that promises to
be
the cheapest one!
2) there is no significant cost advantage in 8B/10B coding over
scrambling from an optics and electronics point of view
3) there is however a cost penalty going to higher speed optics and
electronics. 10 Gb/s can be achieved rather readily for both optics
and
electronics, but a 25% overhead likely makes things more expensive
4) the lower line rate (10.00 vs. 12.5 Gb/s) directly translates
into
longer distances supported, more power budget, and less penalties
(such
as DMD).
Martin Nuss
Drew Perkins wrote:
>
> Paul,
> You hit on another very good reason for the WAN version to
use
> scrambled encoding. Let me rephrase it for emphasis. I believe it
is a
> requirement that 10 Gb/s Ethernet be able to ride over existing
DWDM
spans.
> These spans have already been engineered for 10 Gb/s channels.
Increasing
> the bit rate would increase the optical bandwidth, and would
require
> increasing the optical power as well. Thus an 8B/10B 12.5 Gb/s
signal
would
> not be able to ride on most existing spans, but would instead
require
> completely new spans to be engineered. This will not be acceptable
to many
> carriers. Therefore, using scrambling is clearly a hard
requirement for 10
> Gb/s Ethernet over DWDM systems.
>
> This is, of course, not a factor in the decision whether to use
8B/10B or
> scrambling in the LAN.
>
> Drew
> ---------------------------------------------------------
> Ciena Corporation Email: ddp@xxxxxxxxxxxx
> Core Switching Division Tel: 408-865-6202
> 10201 Bubb Road Fax: 408-865-6291
> Cupertino, CA 95014 Cell/Pager: 408-829-8298
>
> -----Original Message-----
> From: owner-stds-802-3-hssg@xxxxxxxxxxxxxxxxxx
> [mailto:owner-stds-802-3-hssg@xxxxxxxxxxxxxxxxxx]On Behalf Of Paul
> Bottorff
> Sent: Saturday, June 26, 1999 9:20 AM
> To: Drew Perkins; 'Peter_Wang@xxxxxxxx'; 'rabynum@xxxxxxxxxxx'
> Cc: 'stds-802-3-hssg@xxxxxxxx'
> Subject: RE: Issues concerning 10GbE speed standards
>
> Drew:
>
> The data I've seen agrees exactly with your outlook that the total
system
> cost is considerably higher using 12.5 Gig rather than 10 Gig. In
addition,
> the installed base of transmission systems, which has many
available
> lambda, is definitely 10 Gig. The 12.5 Gig solutions can only be
used in
> for new installations.
>
> Our current research indicates that the scrambled encoders do not
increase
> the cost of components versus 8b/10b when used for the same
application.
> Infact, we believe scramblers are less costly than 8b/10b due to
the lower
> frequencies. The current analysis of 8b/10b considers the effects
of
jitter
> compared to the worst case conditions for scrambled coding. This
analysis
> does not give an accurate picture of the requirements for
scrambled
> encoding since the probability of the imbalance used in the
comparison is
> once in more than 10,000 years. Scramblers are statically DC
balanced, it
> is necessary to look at the requirements statistically rather than
in the
> worst case.
>
> Paul
>
> At 10:21 PM 6/25/99 -0700, Drew Perkins wrote:
> >
> >Peter and Roy,
> > The cost of higher speed in the WAN is not so much that of
the
> >electronic parts, but rather the fact that you need more of them
for long
> >distances. This is because most optical effects such as
dispersion
increase
> >with the square of the distance. Thus increasing the speed by 25%
increases
> >the optical effects by 56%, and that tends to decrease the
distance you
can
> >go by about a third. Then you need 33% more spans to go the same
distance.
> >Also, in order to send 25% more bits, you wind up increasing the
power by
> >25%, and you use more optical bandwidth. And since you are
sending more
> >bits, you are using more optical bandwidth. These facts result in
fewer
> >optical channels being supportable on a fiber, resulting in more
fibers
> >being used, resulting in more line systems, etc. The result
again is
more
> >equipment and higher costs.
> >
> >Actually, the electronic parts might become less expensive with
the 25%
> >extra speed. The balanced nature of the 8B10B code decreases the
cost and
> >attention that must be paid to jitter.
> >
> >Drew
> >---------------------------------------------------------
> >Ciena Corporation Email: ddp@xxxxxxxxxxxx
> >Core Switching Division Tel: 408-865-6202
> >10201 Bubb Road Fax: 408-865-6291
> >Cupertino, CA 95014 Cell/Pager: 408-829-8298
> >
> >
> >-----Original Message-----
> >From: owner-stds-802-3-hssg@xxxxxxxxxxxxxxxxxx
> >[mailto:owner-stds-802-3-hssg@xxxxxxxxxxxxxxxxxx]On Behalf Of
> >Peter_Wang@xxxxxxxx
> >Sent: Friday, June 25, 1999 8:35 PM
> >To: rabynum@xxxxxxxxxxx
> >Cc: stds-802-3-hssg@xxxxxxxx
> >Subject: Re: Issues concerning 10GbE speed standards
> >
> >
> >
> >
> >
> >Roy,
> >
> >>From a number of the component vendors' presentations at CFI, I
don't
> recall
> >anyone claiming that the cost of the electronic parts (SiGe or
GaAs) will
> be
> >much different between 10 & 12.5 Gbps. The primary cost issue
seemed
that
> >of
> >the relative laser performance (e.g. temperature stablization).
Also, if
> >you
> >are talking about "converting" an existing Sonet chip to silicon
(meaning
> >that
> >the existing desing is in GaAs) and throwing away a bunch of
circuits, I
> >wouldn't be so sure that the development cost would be much less.
In any
> >case,
> >assuming the volume is large (which I'm sure everyone's hoping),
the
> >development
> >cost will be amortized, and hence not a significant factor. But
this is
a
> >discussion for LAN (or enterprise) applications. I was trying to
> understand
> >the
> >economics of applying Ethernet to WAN but forcing it within the
existing
> WAN
> >practice, and hoping you could provide some insight.
> >
> >Peter
> >
> >
> >
> >
> >Roy Bynum <rabynum@xxxxxxxxxxx> on 06/25/99 04:50:23 PM
> >
> >Please respond to rabynum@xxxxxxxxxxx
> >
> >Sent by: Roy Bynum <rabynum@xxxxxxxxxxx>
> >
> >
> >To: Peter Wang/HQ/3Com
> >cc: stds-802-3-hssg@xxxxxxxx
> >Subject: Re: Issues concerning 10GbE speed standards
> >
> >
> >
> >
> >
> >Peter,
> >
> >Just because a SONET OC192C framing is used, does not mean that
the OAMP
> >functionality is active in the LAN interface. If OAMP processing
is not
> >needed, only the existing SONET chip set, converted to silicon,
with
> >most active functionality, other than path BER can be disabled.
This
> >will leverage the existing technology without the higher cost of
the
> >APS, line and section overhead, etc.
> >
> >Having worked on devices before, I know that the higher the bit
signal
> >rate the more expensive the devices. With a PHY that is 1/4
higher in
> >bit rate, compared the 8B/10B signal rate, the OC192 rate may be
less
> >expensive.
> >
> >Roy
> >
> >
> >
> >Peter_Wang@xxxxxxxx wrote:
> >>
> >> It will help a great deal if you could point out specific
aspects and
> >approaches
> >> where an Ethernet extended to support all of the existing
common
carrier
> >O&M
> >> requirements, encapsulated within the existing Sonet/SDH
structure,
> >running
> >over
> >> existing OC192/STM64 facilities, will actually come out costing
> >significantly
> >> less that the current solution?
> >> - Peter
> >>
> >> Roy Bynum <rabynum@xxxxxxxxxxx> on 06/20/99 07:34:08 AM
> >>
> >> Please respond to rabynum@xxxxxxxxxxx
> >>
> >> Sent by: Roy Bynum <rabynum@xxxxxxxxxxx>
> >>
> >> To: wthirion@xxxxxxxxxx
> >> cc: stds-802-3-hssg@xxxxxxxx, stds-802-3-hssg-speed@xxxxxxxx
(Peter
> >> Wang/HQ/3Com)
> >> Subject: Issues concerning 10GbE speed standards
> >>
> >> Walt, et al,
> >>
> >> The issue of speed is one of economics. The existing GbE
standard does
> >> not allow for any operations support for the optical fiber
facility.
> >> This makes GbE very expensive to maintain and support over a
MAN/WAN
> >> environment. The cost of ownership of GbE will prevent it from
having
a
> >> masive impact directly on the cost of MAN and WAN data
communications.
> >>
> >> Common carrier protocols, such as DS1/DS3/SONET/SDH have
operations and
> >> maintencance functionality incorporated in the overhead of the
> >> protocol. DS1 and DS3 have a subcarrier that provides remote
and
> >> reverse signalling outside of the transport "payload". This
allows
> >> carriers to troubleshoot and maintain remote systems without
haveing to
> >> dispatch someone for every little issue. In some respects, GbE
fails
to
> >> meet the 802.3 functional requirements for interoperation with
common
> >> carrier systems.
> >>
> >> 1000BaseSX and 1000BaseLX are optical networking standards.
Whether
> >> this was the intention or even the perception of the 802.3
working
> >> group. The working group did not include any support for
operations or
> >> maintenance in the optical domain for this protocol. The
functional
> >> operations of copper LAN facilities are well understood by the
802.3
> >> working group, but when you get beyond multi-mode, 850nm,
optical
> >> transport, it is no longer a LAN, it is a WAN. Some will say
that 30km
> >> is a MAN, not a WAN. If you apply the same function processes
> >> distictions to optical systems that are applied to copper
systems, you
> >> will discover that a MAN is actually a WAN within a single
central
> >> office domain. When I was actively working on Ethernet, when it
left
the
> >> building, it was no longer a LAN, it was a WAN.
> >>
> >> In order for 10000BaseX to support MAN/WAN systems within
common
carrier
> >> facilities, common carrier operations and maintance support
must be
> >> within the protocol. SONET/SDH are the current, and most
widely
> >> deployed transport protocols within the common carrier domain.
> >> SONET/SDH use the transport overhead to provide that
functionality.
> >> That functionality allows the common carriers to reduce the
operations
> >> and support costs for the fiber optic transport systems, and
thus lower
> >> the overall costs passed on to the end users. This will be the
economic
> >> breaking point for 10GbE. Can it directly support the fiber
optic
> >> transmission system? Is there any reason why it should not be
able to
> >> directly provide operations support for the optical fiber
systems?
> >>
> >> A second economic issue of speed for 10GbE is one of utilizing
existing
> >> technology and standards at the ~10Gigabit speed range. A
masive
> >> install base of facilities and support already exist for
OC192/STM64 on
> >> a global scale. Optical amplifers, signal and clock recovery
> >> regenerators, and other systems are already in place to carry
> >> OC192/STM64 signals in metropolitan as well as wide are
networks. I
> >> would not want to contemplate the economic impact of having to
install
> >> totally seperate technology to support 10GbE. If it can not
use the
> >> existing ~10Gb technology and facilities, Other than "dark
fiber",
10GbE
> >> will have to be installed over a totaly new, and totaly
seperate
> >> facilities. Is there any reason why 10GbE should not support
and make
> >> use of the existing ~10Gb transport facilities?
> >>
> >> I hope that this message has not been too long. As an employee
of a
> >> common carrier company, I have a recognizable vested interest
in
looking
> >> toward 10GbE as a major economical alternative to existing data
tranport
> >> technolgy, such as TDM or ATM. I have almost 20 years of
designing,
> >> installing, and supporting LAN, MAN, and WAN systems. I have
seen the
> >> economics change as more self-supporting protocols and
technologies
have
> >> become available. The key is to provide a protocol that allows
remote
> >> operations support, which reduces the number of "warm bodies"
that are
> >> required to support the systems. This is what I am asking for.
Is
> >> there any reason why this can not be done?
> >>
> >> Thank you,
> >> Roy Bynum
> >> MCI WorldCom
> >
> >
> >
> >
> >
> >
> Paul A. Bottorff, Director Switching Architecture
> Bay Architecture Laboratory
> Nortel Networks, Inc.
> 4401 Great America Parkway
> Santa Clara, CA 95052-8185
> Tel: 408 495 3365 Fax: 408 495 1299 ESN: 265 3365
> email: pbottorf@xxxxxxxxxxxxxxxxxx