11 Feb
1999
11 Feb
'99
2:56 a.m.
Sorry, I know this wasn't classic computer stuff but, I figured that you
guys would know the answer.
Let me push the question a bit more....
-How do they squeeze that much data down the line? Fiber-optics cabling
only? Data multiplexing?
-How do they discriminate the beginning of one packet from the end of
another when running at such high speeds?
Arfon, this isn't "classic computer
material." However, they work by being
very fast. There are several architectures that support multigigahertz
operation and by processing in parallel you get added avantages. Some of
the first Gbit routers had several processors one for each packet that came
in. I believe the Terabit routers are still doing this.
--Chuck
At 02:33 PM 2/10/99 -0600, you wrote:
Can anyone tell me how they gigabit ethernet
works?
How can they get such high data transfer rate and how can the cards process
the packets so fast???
11 Feb
11 Feb
3:03 a.m.
New subject: eGroups / this list
A while ago there was brief discussion of adding search and moderation
capability to the list, and eGroups was mentioned. Somebody posted "don't
use eGroups - it's terrible" or something to that effect. Well, as
maintainer of a mailing list, about slide rules, I thought I'd give it a go,
despite the warning. So I did.
What can I say? It's great. A little blurb at the bottom of each posting
(like a .sig), but other than that I have extensive moderation capability,
membership listings, privacy for members emails, and a FULL SEARCH
capability, statistics on visitors and more. I have not noticed any spam
eventuating from my creating/joining this list. I'd heartily recommend
egroups for this list.
I think that this list so desperately needs a search capability on the
archives. eGroups does this gratis. I'd really like to know WHY the other
gent canned it so mercilessly as nothing but trouble. Best thing that I've
used, as a list maintainer, since sliced bread.
The sliderule list, btw, is [sliderule]. Visit
http://www.egroups.com/list/sliderule to play around with the search stuff
and/or join my list. Currently we're discussing a recent comic involving
Bill Gates in bed with Ookie, his slide rule. No kidding. Oh, and slide
rule lubrication.
A
--
adavie(a)mad.scientist.com
visit the Museum of Soviet Calculators at
http://www.comcen.com.au/~adavie/slide/calculator/soviet.html
a Yahoo!, Netscape, Wall Street Journal, Newsweek and New Scientist Cool
Site!?
4:52 a.m.
New subject: OT: Re: How does gigabit ethernet work?
Sorry, I know this wasn't classic computer stuff
but, I figured that you
guys would know the answer.
Try an OT header next time.
Let me push the question a bit more....
-How do they squeeze that much data down the line? Fiber-optics cabling
only? Data multiplexing?
What about trying to think ? How do they squeze some 160+ MBit, as needed
for a simple TV chanel within a cable (~512x625x25x16) - and they put not
only one one, but rather some dozends of _uncompressed_ chanels within one
cable, one simple copper cable as installed in hundreds of million places
and they do it since 40+ years .... much data come on - if you would ask
for 1,000 GBit connections maybe :)
-How do they discriminate the beginning of one packet
from the end of
another when running at such high speeds?
How can they seperate even a single Byte from each other at the ridicoulous
speed of 300 Bd - even more, how they seperate two bits ?
C'me on - it's the same water than ever - and it boils still at the same
pressure/temperature combination.
Gruss
H.
--
Ich denke, also bin ich, also gut
HRK
5:25 a.m.
New subject: Dayton Hamfest
Just curious if anyone on the list will be going to the Dayton Hamvention in
May? At this point, I plan on being there since some ARDF stuff is on the
agenda, but it also would be a fun time to get together for anyone on the
list who might be there. The URL is:
http://www.erinet.com/hamvention/index.html
I've never been there before, but I have heard a lot of good things about
the flea market there!
6:56 a.m.
New subject: Dayton Hamfest
Just curious if anyone on the list will be going to the Dayton Hamvention in
May?
I usually do, two years out of three since 1981.
I've never been there before, but I have heard a
lot of good things about
the flea market there!
It's *HUGE*, but there is a lot of crap. Over the years I have picked up
an ASR-33, a couple of PDP-8/L's, a COSMAC VIP, some VIC-20's, Rainbows, an
Informer SNA (3274/3270) dialup portable terminal and a few other assorted
Classic goodies. Mostly now, I get discrete components for my bench and
networking parts. Probably the strangest thing I ever bought there was a
pair of aluminum eight-foot-tall Air Force surplus aircraft maintenance
platforms. I use them as short scaffolding.
Friday is good for selection, Sunday after 14:00 is good for bargains,
especially if it's raining. Oh, yeah... parking sucks, too.
-ethan
5:32 a.m.
New subject: OT: Re: How does gigabit ethernet work?
Let me push
the question a bit more....
-How do they squeeze that much data down the line? Fiber-optics cabling
only? Data multiplexing?
What about trying to think ? How do they squeze some 160+ MBit, as needed
for a simple TV chanel within a cable (~512x625x25x16) - and they put not
only one one, but rather some dozends of _uncompressed_ chanels within one
cable, one simple copper cable as installed in hundreds of million places
and they do it since 40+ years .... much data come on - if you would ask
for 1,000 GBit connections maybe :) > -How do they discriminate the beginning of one
packet from the end of
> another when running at such high speeds?
Well, I was assuming that gigabit ethernet was a single serial connection
and that the packet header detector has to operate at frequencies several
multiples faster than the incomming data stream to detect new packets then
send a complete packet to a processor for address resolution. But, I take
it this is not the case. So, how do they do it?
How can they seperate even a single Byte from each other at the ridicoulous
speed of 300 Bd - even more, how they seperate two bits ?
C'me on - it's the same water than ever - and it boils still at the same
pressure/temperature combination.
Gruss
H.
--
Ich denke, also bin ich, also gut
HRK
12:40 p.m.
New subject: OT: Re: How does gigabit ethernet work?
Arfon Gryffydd <arfonrg(a)texas.net> wrote:n
Well, within a cable signal, it's analog (you can
therefore relate that to
a parallel digital signal), it's also multiplex using different frequencies...
So, I assume that the answer is, gigabit ethernet uses some local
oscillators and modulates a butt-ton of frequencies using many parallel
bits. That would be the closest correlation to how cable TV works.
No. What you describe is a broadband network. AFAIK, gigabit ethernet over
copper still uses baseband techniques.
However, it's not accurate to characterize the difference between baseband and
broadband as digital vs. analog. A high-frequency signal on a cable is
*always* an analog signal. Cables won't pass digital signals. If you put in
a square wave at one end, you don't get a square wave at the other. For
sufficiently low frequencies on suitably terminated cable, you may get a
good enough approximation of a square wave. But this doesn't scale up
to very high frequencies. So usually the waveform driven into the cable
(and expected at the other end) is a carefully engineered analog signal.
It is the job of the transceiver to generate that analog signal at the
transmitting end, and recover the digital data at the receiving end.
12 Feb
12 Feb
10:05 a.m.
New subject: OT: Re: How does gigabit ethernet work?
On 11 Feb 1999, Eric Smith wrote:
*always* an analog signal. Cables won't pass
digital signals. If you put in
But the pind of a microchip are also cables, of sorts. What's the
difference?
--Max Eskin (max82(a)surfree.com)
10:29 a.m.
New subject: OT: Re: How does gigabit ethernet work?
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11:12 a.m.
New subject: OT: Re: How does gigabit ethernet work?
>*always* an analog signal. Cables won't pass
digital signals. If you put in
But the pind of a microchip are also cables, of sorts.
What's the
difference?
Simple answer:
There is no digital signal at all - nowhere - all analogoue.
(Please don't invite von Klitzing :)
Gruss
H.
--
Traue keinem Menschen der 5 Tage blutet und immer noch nicht tod ist.
1:18 p.m.
New subject: OT: Re: How does gigabit ethernet work?
On 11 Feb 1999, Eric Smith wrote:
*always* an analog signal. Cables won't pass
digital signals. If you put in
Max writes:
But the pind of a microchip are also cables, of sorts.
What's the
difference?
1. They aren't multiple meters long.
2. They actually do have transmission line effects. If you're not careful,
there can be enough ringing on the signals (due to lack of proper
termination) to cause undesired behavior.
If you look at bus signals on a 33 MHz bus with a 100 MHz scope, they look
fairly square (unless things are badly designed and/or broken). Now look
at those same signals with a 1 GHz scope. The difference is *amazing*.
At best, all you can do with high speed stuff is get a good enough
*approximation* of the desired digital signal. And the higher the speed
the harder it is to make that approximation good enough.
When you're talking about "digital" signals above 500 MHz (as would be
found on gigabit ethernet twisted pairs), it is very hard to convincingly
describe them as digital. Sure, they are enocded from digital bits, and
the are decoded back into digital bits at the other end, but what happens
inbetween is analog (and basically black magic at that).
Eric
11 Feb
11 Feb
12:26 p.m.
About gigabit ethernet:
Let me push the question a bit more....
-How do they squeeze that much data down the line? Fiber-optics cabling
only? Data multiplexing?
1 Gbps on fiber isn't that much harder than OC12 (622 Mbps). Of course,
it's easy for me to say that, but one of my friends who works for HP's
optoelectronics division designing the laser diodes and transceiver modules
might disagree. But from the point of view of a maker of NIC cards or hubs,
the magic is all encapsulated in a nice little plastic package.
For twisted pair, they use four pairs at 250 Mbps each, half duplex. For
comparison, 100-base-TX uses a single CAT 5 pair at 100 Mbps for transmit,
and a second pair for receive, so they can optionally support full duplex.
And 100-base-T4 uses four CAT 3 pairs at 25 Mpbs, half duplex.
-How do they discriminate the beginning of one packet
from the end of
another when running at such high speeds?
Basically the same way they do it at lower speeds; by looking for coding
violations.
9287
days inactive
9288
days old
11 comments
8 participants
participants (8)
-
adavie＠mad.scientist.com -
ard＠p850ug1.demon.co.uk -
arfonrg＠texas.net -
erd＠infinet.com -
eric＠brouhaha.com -
Hans.Franke＠mch20.sbs.de -
marvin＠rain.org -
max82＠surfree.com