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First Gigabit Ethernet Chip Demo
An anonymous reader writes "Broadcom demonstrated the
world's first Gigabit Ethernet transceiver chip for
existing CAT5 copper cabling yesterday at
NetWorld+InterOp '99. Packaged in a 256-pin TBGA, Broadcom
has begun delivering initial samples at $75/chip. No word on
when full production starts or
when to expect hubs, switches, or NICs based on the chip."
Of course, >99% of Gigabit Ethernet is full-duplex so there are no collisions. This is partly because, up until now, all GigE was fiber-based, and most fiber topologies have one strand for transmit, one for receive (i.e. no way to collide). If you did build half-duplex, I believe the collision domain would be like 20 meters, not very useful.
:-)
The reason Broadcom's chip is so complicated is that for full-duplex GigE on copper, all 4 pairs in the cable are used, _in both directions_. This means the chip uses fancy DSP techniques to subtract what is transmitting from what is receiving. It handles FEXT and NEXT (far-end and near-end cross-talk) as well.
The only other concern is that the end-station just cannot create frames fast enough @ 1518 bytes, so there is a proposal for jumbo frames to enable endstations to lower their rate of frame generation. Still, for decent TCP stacks you can see 500-800 Mbps right now, which is a good bit better than 100Mbps.
The ATM fixed-53B cell is an interesting idea, since it allows for uniform memory allocation per cell (versus ethernet, where you don't know if you need 64 or all the way up to 1518), but in hardware, often the implementation for Ethernet is to use linked-lists of buffers (say of 128B) which will have good efficiency.
Problems like these can always be solved, and Ethernet is cheap and standard.
Death to ATM!
1 Gigabit/s, bah humbug! What I want is 10 Gigabit/s like the folks at Lucent/Bell Labs are playing around with. No sh*t folks, 10!
They'll be showing this off this week. You can get the info about a LAN and a multiplexer.
This sort of makes our workplace upgrade to a 100Base-T switch look sort of feeble.:)
Maybe because fiber sucks and is much more expensive. You can still by 100Mbps fibre stuff - check out the prices.
I would guess that most of the early 100Mbps short range fiber installations have been pulled in favor of cat5. 1000BaseT opens a huge market - I would suspect that prices will soon fall to around $1000 per switched port, which is affordable if you need it.
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I would guess that most unixy slashdot types don't have much experience with Token Ring, which is too bad, because it's actually very solid technology.
Even standard 16Mbps token "feels" faster than your typical office 100Mbps non-switched ethernet segment. It's good to hear that the technology isn't being junked.
--
Business. Numbers. Money. People. Computer World.
Most Ethernets seem to start having collision problems above 50% utilization. The worst case was a Sun
implementation of Ethernet where the wait time after a collision was fixed at the minimum, resulting in the NICs
dropping into lockstep when collisions started and network utilization dropping to 0%.
Then the SUN implementation was not to spec. True Ethernet devices are supposed to wait a random, or pseudo random, time before trying to retransmit after a collision. I'd say their implementation was broken.
Also, if you are talking full-duplex connections, there is no such thing as a collision anymore. Since you can transmit and receive at the same time, you can't have a collision. Buffers can backup on the switches and you could drop traffic, but you wouldn't have a "collision." "Good" switches can also do flow-control, so that their buffers will not overflow. See the 802.3x spec.
Looking at the Gigabit Ethernet Alliance FAQ, it looks like they extend the carrier time and slot time to 512B from 512b. This, in effect, makes the minimum packet length 512B instead of 64B (The official min packet length is still 64B but it will pad it to 512B) for non-full duplex devices. So, unless you have full-duplex connections you are not gaining that much. However, it looks like they try to make up for this with the packet-burst feature, which allows stations to send out multiple consecutive packets without giving up control of the line (supposedly up to the 512B slot time).
Now THIS we can use around the office.
The hell with Win2k, GB-ether is nice for all those big CAD drawings, DB shuffles, Quake games!
Now, about that Internet backbone bandwidth:
If I have GB-ether on my desk, and so does everyone else (even if $75 is just a single chip, the card can't be that bad.. ) - we're going to choke the net to death.
Nevermind that a single PC can't pump data out that fast, a cubefarm of them can. We need significant backbone bandwidth improvements and faster routers.
Where's those danged pure-optical chips?
-- What you do today will cost you a day of your life.
All vendor/consortium links I'm afraid...
Sorry, no raw performance numbers :) I'm also not a networking guru...
Back when I was looking into things, I found a Lisa98 presentation by Curtis Preston called "Using Gigabit Ethernet to Backup 6 Terabytes" -- in his presentation he referred to gigabit ethernet as really being "200Base-T" based on the results he saw. Much depends on your TCP stack and support for jumbo frames, etc. etc.
The ATM vs gigabit ethernet debate totally depends on what "situation" you are talking about. ATM has alot of advantages and seems to be the fastest shipping bandwith available now (OC-48,etc.) It also has nifty billing/accounting/garanteed bandwith abilities and can easily handle both delay sensitive (isochronous) data like streaming media as well as more traditional computer network traffic.
I guess it all comes down to how you want to use it -- I chose Gigabit ethernet for my DNA crunching alphaservers because I knew I was going to have a small number of hosts carrying IP traffic only -- no need for extensive WAN or MAN interconnects or thousands of circuits, no need to deal with isochronous data alongside computer traffic and no real urgent need for the accounting/management features of ATM.
The biggest reason for my choice of gigabit over ATM was inhouse experience -- my group of biogeeks and the corporate IS people have tons of ethernet experience and no real ATM experience. This is why I think gigabit is going to _really_ take off in the LAN/intranet space-- being able to use your ethernet-aware people AND your existing Cat.5 copper wiring is very very attractive.
just my $.02
I was reading some articles on this topic and found some interesting discussions about gigabit ethernet vs. ATM transmission.
In a nutshell, one article suggested that ethernet began to perform less and less efficient the more data was pushed through the ethernet pipe (up to about 65 to 75% overall utilization), due to the differing packet sizes or something like that.
The article then went on to say that for large pipes of data, the single cell-? size of an ATM packet allowed it to scale "much" better than the ethernet network. They said up to something like 95% utilization.
Maybe gigabit ethernet wouldn't be as good of a decision if ATM worked better in this situation. Can anybody explain the difference to me? If you happen to have performance numbers, please post them.
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