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

["Bill St. Arnaud" <bill.st.arnaud@xxxxxxxxxx>]

Drew:

The break even point is going to be dependent on a number of factors,
particularly the cost of fiber itself.  If the cost of dark fiber is very
expensive then the case for Ethernet over SONET probably will make more
sense at shorter distances.  But then you will also have to take in account
the cost of Packet over SONET and using relatively expensive POS routers
versus Ethernet over SONET and generally lower cost ADMs and Ethernet
switches.

But for universities, schools and smaller ISPs where cost is the overall
riding concern then low cost "gopher bait" or aerial fiber with long haul
GbE is very attractive.  This may not be a suitable solution for carriers or
large commercial enterprise networks, but I think it remains a substantial
market.  And I always like solutions that give customers a wider range of
choices.

Bill

-------------------------------------------
Bill St Arnaud
Director Network Projects
CANARIE
bill.st.arnaud@xxxxxxxxxx
http://tweetie.canarie.ca/~bstarn

 

 



> -----Original Message-----
> From: Drew Perkins [mailto:drew.perkins@xxxxxxxxxxxx]
> Sent: Friday, May 28, 1999 9:55 PM
> To: 'bill.st.arnaud@xxxxxxxxxx'; 'bin.guo@xxxxxxx';
> '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
> and other issues
>
>
> Bill,
> 	I'm in complete agreement on most of this. One number that you've
> proposed a number of times is the 1,000 km breakeven point
> between long-haul
> SONET/WDM and 10 GbE. You could very well be right, but have you
> worked out
> the numbers on this? I am curious about your assumptions. I would
> think the
> number should be closer to 2-3x a single span length, which is
> probably 100
> +/- 20 km, giving a breakeven in the 200-400 km range.
>
> Drew
> ---------------------------------------------------------
> Ciena Corporation                 Email: ddp@xxxxxxxxxxxx
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> 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 Bill St.
> Arnaud
> Sent: Friday, 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"@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
> > > >========================
> >
>