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RE: Wide Area Networking for the Rest of US - the debate on BER a nd other issues

I believe that there will be lots of creativity with what I called item 1.
IP/Ethernet.  There are merits and they should be discussed.  What you
propose is a good example.

I believe that Bill was saying let's not burden Ethernet with SONET issues.
If you want SONET then bolt IP/Ethernet to SONET to get IP/Ethernet/SONET.

As for if anyone cares.  I think the answer is yes people care.  There is a
lot of OC-192 based SONET and DWDM systems being deployed today.  It would
be much better if we were consistent with the current status quo as well as
the brave new world of long-haul Ethernet.


-----Original Message-----
From: Paul Gunning [mailto:paulg@xxxxxxxxxxxx]
Sent: May 28, 1999 10:32 AM
To: Iain Verigin;
Cc: bin.guo@xxxxxxx; rtaborek@xxxxxxxxxxxxxxxx;
dwmartin@xxxxxxxxxxxxxxxxxx; stds-802-3-hssg@xxxxxxxx;
sachs@xxxxxxxxxxxxxx; widmer@xxxxxxxxxx widmer@xxxxxxxxxx
Subject: Re: Wide Area Networking for the Rest of US - the debate on BER
a nd other issues

Iain, Bill &c.

Why not...

	Layer 3		IP
	Layer 2		Ethernet (10GbE = serial 10Gbit/s -> 12.5GBaud with
	Layer 1		Optics 	  (N * 12.5 GBaud via N WDM channels)

then have a generic PHY termination onto which one of three possible 
optical "modules": 

a)	850nm VCSELs for short reach using multimode fibre (<300m)

b)	1300nm Fabry-Perot or VCSELs for short-to-intermediate reach (<30km)

c)	1550nm temperature controlled DFB lasers for long reach (>30km)

can be plugged? Want to increase capacity? Use WDM! (Just consider
each WDM channel as a "virtual" fibre!)

Option b) can make use of mature 1300nm TWSOA (Travelling Wave
Optical Amplifier) technology to extend the link length.

Option c) can make use of mature EDFA technology to extend the 
transmission span. Moreover the use of temperature control "locks"
the position of the DFB wavelength i.e channel, within the EDFA
which is 50 THz of bandwidth (anyone for Terabit Ethernet?)
assuming 1535nm <-> 1565nm; 1580nm <->1610nm are used.
Consequently a long-distance, optically-amplified, fibre 
transmission path could happily carry a mixture of 
SONET/SDH _AND_ 10 GbE traffic simultaneously. For example, 
1535nm <-> 1565nm would carry 16 * 10 GbE channels;
1580nm <-> 1610nm would carry 16 * OC-192/STM-48 channels?  
Each distinct channel is assigned a distinct wavelength.
Use simple passive "blue/red" WDM couplers to MUX/DEMUX
the SONET wavelength band from the GbE wavelength band
at the termination points at either end of the trabsmission

	That's 320 Gbit/s of data!!!

For the 10GbE standard is it _REALLY_ necessary to map 10 GbE 
into SONET/SDH frames? Why not aim for simplicity? For long distances 
over grey fibre (i.e. partially "lit"= available optical amplifer 
bandwidth not fully exploited; dark fibre is "unlit") this is 
desirable. Remember SONET and 10 * GbE can co-exist happily. Moreover
1300nm intermediate haul 10 GbE could also be carried along with the 
1550nm traffic mix!

Has anyone considered exploiting Air Blown Fibre e.g.

as a simple method for installing and/or upgrading the fibre 
plant within a building or campus to single-mode?

Finally, serial 100 GbE will be possible soon. It will use a 
pragmatic mix of optics and electronics. Therefore the choices
that are adopted for 10GbE will have a crucial bearing on the 
ease with which serial 100GbE will become a reality. 

(Note that by using WDM as "virtual" fibre 10 * 100GbE = 1 TbE !) 

Keep it serial, keep it simple.

I would welcome your comments and criticisms of the above. 


Iain Verigin wrote:
> As I know it, there could be three IP stacks at 10G.  Two exist today at
> lower rates, they are:
> 1. IP/Ethernet - General use is intra-CO (LAN) interconnect.
> 2. IP/Packet-over-Sonet (POS) RFC 1619 - General use is inter-CO (WAN)
> interconnect.
>    (Note IETF RFC 1619 has been revised to include OC-192c.)
> I agree with Bill that we should investigate a third stack that would be
> consistent with today's WAN infrastructure.
> 3. IP/Ethernet/SONET.
> * there are many reasons for this. I believe one of the strongest is that
> removes the need for Layer 3 processing that POS imposes.  A negative is
> that it adds more bytes, an Ethernet tax, which may not be desirable on
> haul links.
> * the IEEE could work on this because no other standards body is.
> Iain Verigin
> PMC-Sierra
> -----Original Message-----
> From: Bill St. Arnaud []
> Sent: May 28, 1999 5:52 AM
> To: bin.guo@xxxxxxx; rtaborek@xxxxxxxxxxxxxxxx;
> dwmartin@xxxxxxxxxxxxxxxxxx
> Cc: stds-802-3-hssg@xxxxxxxx; sachs@xxxxxxxxxxxxxx; "widmer@xxxxxxxxxx
> widmer@xxxxxxxxxx widmer"
> Subject: Wide Area Networking for the Rest of US - the debate on BER and
> other issues
> All:
> I have been following the interesting debate about BER. Let me bring some
> further issues into the debate.
> I am assuming that on WAN and long haul GbE the upper layer protocol will
> only be IP.
> On most IP links, even ones with BERs of 10^-15 there is about 1-3% packet
> loss and retransmission.  This is due to a number of factors but most
> typically it relates to TCP flow control mechanism from server bound
> congestion (not network congestion) and the use of WRED in routers.
> So, on most IP links the packet loss due to BER is significantly less than
> that due to normal TCP congestion.  As long as that ratio is maintained it
> is largely irrelevant what the absolute BER value is.  There will be many
> more retransmissions from the IP layer than there will be at the physical
> layer due to BER.
> Other protocols like Frame Relay and SNA are a lot more sensitive to high
> BERs.  IP ( in particular TCP/IP) is significantly more robust and can
> quite effectively in high BER environments e.g. TCP/IP over barbed wire.
> I would like to suggest that the 802.3 HSSG group consider an 2 solutions
> for 10xGbE WAN:
> (1) native 10xGbE using 8b/10b; and
> (2)10xGbE mapped to a SONET STS OC-192 frame
> For extreme long haul solutions SONET makes a lot of sense as a transport
> technology.  However for intermediate long haul (up to 1000 km) and WAN
> native 10xGbE is more attractive. Native GbE can be either transported on
> transparent optical network or carried directly on a CWDM system with
> transceivers. In medium range networks coding efficiency is not as
> as it is in long haul networks. If coding efficiency is important then in
> opinion, it does not make sense to invent a new coding scheme for 10xGbE
> when it would be just as easy to map it to a SONET frame.
> The attraction of native 10xGbE for the WAN is that it is a "wide area
> networking solution for the rest of us".  You don't need to hire
> SONET engineers to run and manage your networks.  The 18 year old kid who
> running your LAN can now easily learn to operate and manage a WAN.
> In Canada and the US, there are several vendors who are willing to sell
> fiber at a very reasonable cost.  Right now the cost of building a WAN
> 10xGbE and CWDM is substantially less (for comparable data rates) than
> SONET equipment.
> Bill
> -------------------------------------------
> Bill St Arnaud
> Director Network Projects
> > -----Original Message-----
> > From: owner-stds-802-3-hssg@xxxxxxxxxxxxxxxxxx
> > [mailto:owner-stds-802-3-hssg@xxxxxxxxxxxxxxxxxx]On Behalf Of
> > bin.guo@xxxxxxx
> > Sent: Thursday, May 27, 1999 7:28 PM
> > To: rtaborek@xxxxxxxxxxxxxxxx; dwmartin@xxxxxxxxxxxxxxxxxx
> > Cc: stds-802-3-hssg@xxxxxxxx; sachs@xxxxxxxxxxxxxx; "widmer@xxxxxxxxxx
> > widmer@xxxxxxxxxx widmer"
> > Subject: RE: 1000BASE-T PCS question
> >
> >
> >
> > Rich,
> >
> > The DC balance can be directly translated into jitter (when timing is
> > concerned) and offset (when threshold slicing is concerned).  You
> > only need
> > to deal with the former if the signal is 2-level NRZI, while you need to
> > deal with both if multi-level signal modulation is used.
> >
> > For long term DC imbalance, it translates into low frequency jitter and
> > it's low enough(<1 KHz ?), it's called baseline wonder.  For
> > short term, it
> > relates to Data Dependent Jitter, which is more difficult for timing
> > recovery to handle since it's not from system or channel imparity, and
> > therefore it's harder to compensate.
> >
> > When you have a lot of jitter margin, for example in lower speed
> > the amount of jitter, translated from DC drift resulted from data
> > imbalance
> > coupled by AC circuit, percentage wise is a small portion of the clock
> > period and therefore does not contribute to much of the eye
> > closing.  On the
> > other hand, for high speed clocking at 10G (100 ps?), the jitter
> > translated
> > from the same amount of DC drift can be a significant portion of the
> > period, so contributes to much large percentage wise jitter which
> > results in
> > reduced eye opening -- higher BER.
> >
> > Dave said in his mail that "The limiting factor is enough RX optical
> > to provide a sufficiently open eye." but you still have to deal with the
> > data dependent jitter due to DC imbalance generated after O/E, that can
> > close the eye further again.
> >
> > Bin
> >
> > ADL, AMD
> >
> > > -----Original Message-----
> > > From:       Rich Taborek [SMTP:rtaborek@xxxxxxxxxxxxxxxx]
> > > Sent:       Thursday, May 27, 1999 3:23 PM
> > > To: David Martin
> > > Cc: HSSG_reflector; Sachs,Marty; Widmer,Albert_X
> > > Subject:    Re: 1000BASE-T PCS question
> > >
> > >
> > > Dave,
> > >
> > > Do you know of any research or other proofs in this area? You say that
> > > lower speed SONET links regularly achieves BERs of < 10 E-15. I have
> > > substantial experience with mainframe serial links such as ESCON(tm)
> > > where the effective system BERs are in the same ballpark. SONET uses
> > > scrambling with long term DC balance and ESCON uses 8B/10B with short
> > > term DC balance. The following questions come to mind:
> > >
> > > - How important is DC balance?
> > > - How does this importance scale in going to 10 Gbps?
> > >
> > > I'll see if I can get some 8B/10B experts to chime in here if you can
> > > get scrambling experts to bear down on the same problem.
> > >
> > > --
> > >
> > > >(text deleted)
> > > >
> > > >The point here is that the SONET scrambler is not the limiting issue
> > > >achieving low error rates. The issue is having enough photons/bit, or
> > > >optical SNR (eye-Q) to accurately recover the data.
> > > >
> > > >...Dave
> > > >
> > > >David W. Martin
> > > >Nortel Networks
> > > >+1 613 765-2901
> > > >+1 613 763-2388 (fax)
> > > >dwmartin@xxxxxxxxxxxxxxxxxx
> > > >========================
> >

Paul Gunning
Futures Lab
BT Laboratories

Phone:	+44 1473 647049
Fax:	+44 1473 646885