Re: Wide Area Networking for the Rest of US - the debate on BER and other issues

["Mike Dudek" <mdudek@xxxxxxxxxxxx>]

I do not agree that the BER must be improved with data rate increase in order to
obtain the higher throughput.  At least for packet based transmission with
retransmission of errored packets, the throughput increases in proportion to the
data rate for the same BER, assuming that the packet length (in bytes) remains
fixed.  I do not think that anyone has proposed changing the packet length, but
if they did then the BER might have to be improved.  The throughput is of course
the number of good packets in any interval of time.

"Chang, Edward S" wrote:

> Bin:
>
> Yes, I agree.  The BER should be improved with data rate increase, if the
> through put gained from higher data rate is to be maintained.  In addition
> to the retry times wasted, the external sources of noise remain the same,
> which further requires the lower BER.  These are the correct design goals we
> should work on.  Although, we also should keep the cost-effectiveness in
> mind to maintain optimum balance between performance and cost.
>
> Ed Chang
> Unisys Corporation
>
> -----Original Message-----
> From: bin.guo@xxxxxxx [mailto:bin.guo@xxxxxxx]
> Sent: Friday, May 28, 1999 4:57 PM
> To: Edward.Chang@xxxxxxxxxx; bill.st.arnaud@xxxxxxxxxx;
> rtaborek@xxxxxxxxxxxxxxxx; dwmartin@xxxxxxxxxxxxxxxxxx
> Cc: stds-802-3-hssg@xxxxxxxx; sachs@xxxxxxxxxxxxxx; "widmer@xxxxxxxxxx
> widmer@xxxxxxxxxx widmer"@us.ibm.com
> Subject: RE: Wide Area Networking for the Rest of US - the debate on BER
> a nd other issues
>
> Ed,
>
> If the specified BER for 1000BASE-X is 10^ -12, then to have the equal
> error-free period the specified BER for 10G should be at least 10^ -13.
> Based on Rich T and Rich S's BER number:
>
> A system BER of 10 E - 8 @  10 Mbps = a bit error every 10 seconds.
> (10BASE-T)
> A system BER of 10 E-12 @ 100 Mbps = a bit error every 166 minutes, 40
> seconds.        (100BASE-X)
> A system BER of 10 E-10 @     1 Gbps = a bit error every 1 minutes, 40
> seconds.                (1000BASE-T)
> A system BER of 10 E-12 @     1 Gbps = a bit error every 16 minutes, 40
> seconds.        (1000BASE-X)
> A system BER of 10 E-12 @   10 Gbps = a bit error every 1 minutes, 40
> seconds.
> A system BER of 10 E-13 @   10 Gbps = a bit error every 16 minutes, 40
> seconds.
>
> If the TCP/IP is the only protocol 10G PHY needs to support, then the above
> specified BER may be more than enough.  Moving from 1G to 10G, the bit
> period is scaled 10X smaller while jitter and noise from some sources are
> not scaled the same way -- much tight control should be applied to achieve
> even the same BER.
>
> Bin
>
> ADL,AMD
>
>
>
>
> > -----Original Message-----
> > From: Chang, Edward S [SMTP:Edward.Chang@xxxxxxxxxx]
> > Sent: Friday, May 28, 1999 12:44 PM
> > To:   bill.st.arnaud@xxxxxxxxxx; Guo, Bin; rtaborek@xxxxxxxxxxxxxxxx;
> > dwmartin@xxxxxxxxxxxxxxxxxx
> > Cc:   stds-802-3-hssg@xxxxxxxx; sachs@xxxxxxxxxxxxxx; "widmer@xxxxxxxxxx
> > widmer@xxxxxxxxxx          widmer"@us.ibm.com
> > Subject:      RE: Wide Area Networking for the Rest of US - the debate on
> > BER a nd other issues
> >
> > Bill:
> >
> > I like your idea of implementing native 10xGBE for intermediate long haul
> > and WAN, which is a good move.  The advantage you are mentioning will
> > greatly reduce the cost to users.
> >
> > It is true, in a TCP/IP links, the TCP flow control causes more
> > retransmission than BER. Therefore, the extremely low BER, 10^-15, does
> > not
> > necessarily gain any more advantage than the specified BER of 10^-12.
> >
> >
> > Ed Chang
> >
> > -----Original Message-----
> > From: Bill St. Arnaud [mailto:bill.st.arnaud@xxxxxxxxxx]
> > Sent: Friday, May 28, 1999 8:52 AM
> > To: bin.guo@xxxxxxx; rtaborek@xxxxxxxxxxxxxxxx;
> > dwmartin@xxxxxxxxxxxxxxxxxx
> > Cc: stds-802-3-hssg@xxxxxxxx; sachs@xxxxxxxxxxxxxx; "widmer@xxxxxxxxxx
> > widmer@xxxxxxxxxx widmer"@us.ibm.com
> > 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
> > work
> > 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
> > a
> > transparent optical network or carried directly on a CWDM system with
> > transceivers. In medium range networks coding efficiency is not as
> > important
> > as it is in long haul networks. If coding efficiency is important then in
> > my
> > 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
> > specialized
> > SONET engineers to run and manage your networks.  The 18 year old kid who
> > is
> > 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
> > dark
> > fiber at a very reasonable cost.  Right now the cost of building a WAN
> > with
> > 10xGbE and CWDM is substantially less (for comparable data rates) than
> > using
> > SONET equipment.
> >
> > Bill
> >
> >
> >
> >
> >
> > -------------------------------------------
> > Bill St Arnaud
> > Director Network Projects
> > CANARIE
> > bill.st.arnaud@xxxxxxxxxx
> > http://tweetie.canarie.ca/~bstarn
> >
> >
> >
> >
> >
> >
> >
> > > -----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"@us.ibm.com
> > > 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
> > if
> > > 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
> > clocking,
> > > 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
> > clock
> > > 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
> > power
> > > 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
> > in
> > > > >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
> > > > >========================
> > >