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Gigabit Crossover Connection

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July 13, 2004 6:47:29 PM

I want to speed up data transfer between two computers and my first solution was to connect them both via firewire (winXp running tcp/ip over firewire).
But now I am thinking about getting two gigabit adapters, to be precise two Netgear GA311. The question I have: Can I connect these two adapters with a crossover cable or do I need a switch in between ? I wanted to avoid having the switch as it is only two machines. I am also not sure if I need the crossover cable, as there is some auto-uplink feature which can detect the cable mode.
Any ideas/comments/help is welcome.
Thanks !

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July 18, 2004 5:28:37 AM

i standard crossover will not work. most people dont realise that a 100 mbit connection only uses 2 pairs of a 4 pair cable. gigabit connections use all 4 pairs. a standard "oldschool" crossover connector wont work for gigabit.

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July 20, 2004 7:04:50 PM

From what I've read in the past, gigabit is a smart interface. Supposedly all you need is straight cable, CAT 5E or CAT 6 cable (or CAT 5 as long as all 4 pairs are wired).

Although, most people were talking about the Intel NICs so maybe it's not universal.

I've never tried it. I don't have gigabit adapters.

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July 22, 2004 1:42:12 PM

no way any one really needs cat 6 yet.

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August 7, 2004 12:57:20 AM

2 nics and a crossover will yeld the same results as that of two PCs connected to a switch.

I have found that on the server 2000 and 2003 you can allocate more resources to help with the bottleneck of two many trying to get on. I have also seen that the NICs that can take advantage of DMA will also help out. but I realy think that the gig lan will run as fast as the giglan spec will allow it.

Watch your performance and see where the bottleneck is. Maybe your system is taxed by other services or un-needed protocols.

Crossover: boy I don't know if I was seeing things or maybe thought I was seeing a gigabit connection but; I can swear that Two peeps at a lanparty had a free gigport between their servers and used a crossove to do some file swapping.. I could be wrong....

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August 22, 2004 8:24:55 PM

The main bottleneck will be your Hard Drive, and unless you have a good 10,000RPM Hard Drive it will probably top out at about 45MB/s, slightly less than the theoretical maximum of the firewire connection. Then again Ethernet would give you better compatability and upgradeability, so its really a question of how many comps you might have in the future?

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September 18, 2004 5:02:01 AM

To correct a few things, since this caught my eye...

The bottleneck will not be the hard drive, a hard drive operates about the same speed or slightly faster (sequential read/write) than a gigabit card is capable of when plugged in to either a PCI bus or the funky thing Intel did with some of their built-in motherboard gigabit adapters. PCI gigabit cards get around 30's to mid 40's MB/sec tops, I think due to overhead in the PCI and TCP protocols and the low throughput of PCI. To get gigabit speeds you need a system with 64-bit, 66-100-133 MHz PCI slots.

You don't need a crossover cable in gigabit networking, ever. If you look at gigabit switches, you'll notice they never have an "uplink" port on them anymore. All gigabit ports auto-sense the other port and connect appropriately. i.e. you can run a gigabit cable straight from one PC to the other and it will connect perfectly.

You might actually get better performance from firewire than from gigabit. I don't know what kind of speeds you get from firewire, but my assumption is that it might require less overhead since firewire devices don't need to be able to route packets through a global network. But I'm just guessing here.
February 23, 2006 7:07:42 PM

You DO need a cross over. The switch ports will support auto cross over, not NIC's. Especialy not a Netgear nic.

Firewire is a nice soultion if the PC's are next to each other. If they are more than 2m appart.. then ethernet is the next best option.
February 26, 2006 9:18:30 PM

crossover always gets me reduced network performance (30% crossover, 80+% with switch) - does anyone else get that?
August 14, 2006 7:48:04 AM

Actually, the Gigabit NICs do support what is called auto-negotiation (auto-MDX), so a straight cable will work between the two. I have tried that myself with different brands. Even a Gigabit connected with a 100BaseTX card will work with the straight cable. In short, just go ahead and try the normal, straight cable, it won't hurt.
August 14, 2006 1:12:40 PM

Quote:
I want to speed up data transfer between two computers and my first solution was to connect them both via firewire (winXp running tcp/ip over firewire).
But now I am thinking about getting two gigabit adapters, to be precise two Netgear GA311. The question I have: Can I connect these two adapters with a crossover cable or do I need a switch in between ? I wanted to avoid having the switch as it is only two machines. I am also not sure if I need the crossover cable, as there is some auto-uplink feature which can detect the cable mode.


1 gigabit is a theoretical number, and there's some way to go before you can achieve that. In general, you can get a significant benefit, but when you're starting with firewire, the amount of benefit won't be so large -- firewire, if done right, isn't bad to start. You are going to be bottlenecked by HD and file transfer protocol, etc,. to some degree -- even with a perfect GbE network, you wouldn't hit 1000 Mb/s. The best I've personally been able to hit for file transfers so far is around 720 Mb/s, and this is with RAID on both sides.

So, I'd suggest that you're probably just fine with firewire, and that the gains from GbE wouldn't be as large as the theoretical numbers might suggest.

If you still want to go ahead...

From the picture on their web site, the Netgear uses a RealTek chip. This chip is very CPU intensive, and that can cause you problems / loss of performance. I'd recommend looking for an Intel NIC instead -- you can find the Pro 1000 MT desktop adapter for around $21-$29 online. If you have a fast dual core CPU, you can perhaps get away with the Netgear; otherwise, if you want to be able to hit high speeds, I'd suggest another NIC.

Again, your performance will most likely be limited by your HD's, and in this case, your NICs won't be running full speed, and so their CPU usage won't be 100%. However, that high CPU utilization can eventually be a barrier to performance / system smoothness.

You can use a straight-through cable between 2 GbE NICs -- it's part of the standard. I've done it many times. And when you do so, you get the ability to use jumbo frames for "free" -- you don't need a special switch and network setup -- you just need to set the MTU in the registry, and enable jumbo frames in the NIC properties. For at least PCI gigabit NICs, this generally gives a significant performance improvement.

But again, you're going to be limited by the HD's typically, so having an uber GbE network is not necessarily going to get you the sorts of performance figures you might otherwise think.

30 MB/s (240 Mb/s) is a reasonable practical target for GbE. This is around 3x as fast as 100 Mb/s, making that leap to gigabit worthwhile. But you should already be around 30 MB/s with firewire, so you'd likely gain nothing getting here with GbE.

50-60 MB/s (400-480 Mb/s) is also reasonably achievable with GbE with fast drives in the outer sectors or RAID arrays. If you have such drives, and take the trouble to set up decent NICs etc., you should be able to get this fast.

The initial jump from "fast" ethernet to gigabit/firewire, say 10 MB/s to 30 MB/s, is a 200% increase. The increase from 30 MB/s to 60 MB/s is "only" a 100% increase, and is harder -- diminishing returns have already kicked in, and you might not even get that performance.
August 25, 2006 3:00:20 AM

Quote:
You DO need a cross over. The switch ports will support auto cross over, not NIC's. Especialy not a Netgear nic.


Not correct. As someone said. Some NIC's will and some won't. but a good deal of them do.
August 25, 2006 3:35:28 AM

Quote:
You DO need a cross over. The switch ports will support auto cross over, not NIC's. Especialy not a Netgear nic.

Firewire is a nice soultion if the PC's are next to each other. If they are more than 2m appart.. then ethernet is the next best option.


And you DO need to research before posting. This is a Planet NIC, very cheap, which supports Auto-MDI and hence straight or crossover cables.

Auto-MDI
August 25, 2006 4:22:23 AM

Quote:
You don't need a crossover cable in gigabit networking, ever. If you look at gigabit switches, you'll notice they never have an "uplink" port on them anymore. All gigabit ports auto-sense the other port and connect appropriately. i.e. you can run a gigabit cable straight from one PC to the other and it will connect perfectly.


You're thinking of a hub, as far as the uplink port that you don't see anymore. You don't see them anymore because you rarely see hubs nowadays. Switches still have uplink ports in the higher end segments, I believe. Like a 24 port 100mbit switch will have a pair of gigabit fiber ports or something like that.

http://netgear.com/Products/Switches/Layer2ManagedSwitc...
September 22, 2006 4:32:47 AM

i made my own crossover cable, cut cut cut cut tie them and tape

I DIDNT SEE ANY PERFORMENCE LOSS, it goes 80%+ when the file transfer is peaking (goes to 3% when my hdd seeks and transfer small files, u know, the hdd is the bottle neck on lots of small files transfers)
September 2, 2011 8:15:30 PM

CcAgan said:
You DO need a cross over. The switch ports will support auto cross over, not NIC's. Especialy not a Netgear nic.

Firewire is a nice soultion if the PC's are next to each other. If they are more than 2m appart.. then ethernet is the next best option.


please read around

[ http://en.wikipedia.org/wiki/IEEE_802.3 ]

[ http://en.wikipedia.org/wiki/Crossover_cable_(ethernet) ]

Automatic crossover

If one of two connected devices has the automatic MDI/MDI-X configuration feature there is no need for crossover cables. Introduced in :sol:  1998, this made the distinction between uplink and normal ports and manual selector switches on older hubs and switches obsolete.[2]
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