Gigabit Ethernet
- Thread starter MatiasZ
- Start date
Ouch... didn't think about it. Yeah, that's really weird. The only thing I can think about is this reply from the Yukon Support guys:
"It should help to have a switch or router as they should take care of any "fragmented" or "oversize" packets between the two systems."
But still... it's weird. When I connected the new switch it was like magic, it started flying and everything is running really smooth.
"It should help to have a switch or router as they should take care of any "fragmented" or "oversize" packets between the two systems."
But still... it's weird. When I connected the new switch it was like magic, it started flying and everything is running really smooth.
I can't really understand that. I would expect a PC driver to have more RAM to re-assemble and re-order packets than a switch, unless you have a cheap network card with a lousy driver.
All I can think of is that it could be that the more expensive switch maybe negotiates speed and protocol better with the ethernet cards than the Netgear switch does or the cards do with each other. Another possibility might be that your cable(s) are a little flaky and the Netgear switch is more conservative and switches down to 100Mb/s more readily.
All I can think of is that it could be that the more expensive switch maybe negotiates speed and protocol better with the ethernet cards than the Netgear switch does or the cards do with each other. Another possibility might be that your cable(s) are a little flaky and the Netgear switch is more conservative and switches down to 100Mb/s more readily.
A few things I can add to this thread...
First, crossover cables don't work with gigabit ethernet. I know, it's counter-intuitive, but you can't run gigE over a crossover cable between two machines; it doesn't work that way.
Second, in all versions of Windows XP and the "unpatched" version of Server 2003 that uses the standard NDIS 5.1 network stack, using the PC to fragment and re-assemble fragmented frames is very slow. Why? Because each packet generates an interrupt, and if you need to assemble six packets(9000 byte frame broken into six 1500 byte packets) for each frame, you're going to have abysmal performance as your kernel usage on the PC goes to hell.
If you have a good NIC, Server 2003 SP1 operating system and download the Scalable Network Pack update from Microsoft, you can potentially get rid of a lot of that overhead. But what likely happend was, your upgraded switch is doing the proper thing and setting the proper header information so your card can obtain the correct MTU value (or at least allowing the OS to detect it properly)
With your new switch, it's likely that you can try again with the 9000-byte frames. It's essentially impossible to completely utilize a gigE link with two machines and an MTU of ~1500 bytes, but with MTU's of 9000 bytes or more, you can get very close. One thing to do: change the TCP receive buffer window on your Windows OSes. You can find information on the appropriate registry entries by searching "RFC 1323 Options" on Microsoft's knowledgebase site.
First, crossover cables don't work with gigabit ethernet. I know, it's counter-intuitive, but you can't run gigE over a crossover cable between two machines; it doesn't work that way.
Second, in all versions of Windows XP and the "unpatched" version of Server 2003 that uses the standard NDIS 5.1 network stack, using the PC to fragment and re-assemble fragmented frames is very slow. Why? Because each packet generates an interrupt, and if you need to assemble six packets(9000 byte frame broken into six 1500 byte packets) for each frame, you're going to have abysmal performance as your kernel usage on the PC goes to hell.
If you have a good NIC, Server 2003 SP1 operating system and download the Scalable Network Pack update from Microsoft, you can potentially get rid of a lot of that overhead. But what likely happend was, your upgraded switch is doing the proper thing and setting the proper header information so your card can obtain the correct MTU value (or at least allowing the OS to detect it properly)
With your new switch, it's likely that you can try again with the 9000-byte frames. It's essentially impossible to completely utilize a gigE link with two machines and an MTU of ~1500 bytes, but with MTU's of 9000 bytes or more, you can get very close. One thing to do: change the TCP receive buffer window on your Windows OSes. You can find information on the appropriate registry entries by searching "RFC 1323 Options" on Microsoft's knowledgebase site.
That's not true, crossover cables work just fine for gigE. However, 10/100mbit Ethernet only uses 2 signal pairs (4 wires) and typical crossover cables only cross these two pairs. There are crossover cables available which work just fine for gigabit Ethernet (crossing all 4 pairs).
Actually, you would be correct. It's hard to explain the differences to most people; I should've known better on this website
My apologies...Actually, you would be correct. It's hard to explain the differences to most people; I should've known better on this website
Lot's of info! Thank you both! The cable I used to test the cross-over was a regular non-crossed 568-B cable which I patched myself, since I saw on the specifications of the card that it would detect it automatically. And it did
however, it might have been the reason why it didn't work as expected.Moving on to the Jumbo frames, I've read a lot on it but still can't come with a conclusion. Right now, in my network there are:
- PC 1 - NF4 Gigabit NIC - Windows XP SP2
- PC 2 - D-LINK DGE-530T Gigabit NIC - Windows XP SP2
- PC 3 - Conceptronic Wireless 802.g - Windows XP SP2
- Server - Marvell Yukon Gigabit NIC - openSuSe Linux 10.0
- Linksys Router (with the Wireless AP built-in for PC 3)
- Gigabit Switch
Can I use jumbo frames and still access the internet regularly? What and how should I set it up?
Well, here are some potential problems:
First, jumbo frames can cause problems with "cheap" equipment. Most basic consumer-level hardware just doesn't have the intelligence to deal with non-standard sized frames properly. So, when you mention "gigabit switch", it really becomes important who manufactured that switch and what model it is. If you bought a Cisco-branded unit, then I'm pretty sure it's going to work. If you bought a DLINK unit, I'm going to wager Jumbo frames will throw it for a loop. (Hey, I have a DLINK wireless router and it's never given me problems... but I know its limits )
Second, jumbo frames can cause problems when you need to "hop" to a network that uses smaller packets. Want a great example? Your internet connection. The huge packets will have to be broken down into smaller pieces in order to be transmitted across a link with a smaller packet size. So even if you have a quality gigabit switch, chances are your router doesn't support jumbo frames.
As such, the switch will have to break down your 9000-byte packets into multiple individual ~1500 byte packets before it can be sent to the router. When the router gets ahold of them, they'll likely get broken down further into 1472, 1400 or even smaller packets before being sent over the internet. All of that packet "breakdown" is called fragmentation, and excessive fragmentation is even worse for a network than it is for your hard drive.
Finally, jumbo frames are great for making sure that a point-to-point connection can get the absolute most out of your high speed network. But if you've got more than two PC's on that network, you can still get good use out of gigabit ethernet with 1500-byte frames simply because you have a lot more backplane bandwidth to get all those boxes talking simultaneously.
So -- if you want uber bandwidth between two points, jumbo frames are definitely the way to do it. But if you just want a much faster home network without odd limitations on what other network devices you use, stick with the standard frame size and live with the "only half bandwidth useable"
First, jumbo frames can cause problems with "cheap" equipment. Most basic consumer-level hardware just doesn't have the intelligence to deal with non-standard sized frames properly. So, when you mention "gigabit switch", it really becomes important who manufactured that switch and what model it is. If you bought a Cisco-branded unit, then I'm pretty sure it's going to work. If you bought a DLINK unit, I'm going to wager Jumbo frames will throw it for a loop. (Hey, I have a DLINK wireless router and it's never given me problems... but I know its limits
)Second, jumbo frames can cause problems when you need to "hop" to a network that uses smaller packets. Want a great example? Your internet connection. The huge packets will have to be broken down into smaller pieces in order to be transmitted across a link with a smaller packet size. So even if you have a quality gigabit switch, chances are your router doesn't support jumbo frames.
As such, the switch will have to break down your 9000-byte packets into multiple individual ~1500 byte packets before it can be sent to the router. When the router gets ahold of them, they'll likely get broken down further into 1472, 1400 or even smaller packets before being sent over the internet. All of that packet "breakdown" is called fragmentation, and excessive fragmentation is even worse for a network than it is for your hard drive.
Finally, jumbo frames are great for making sure that a point-to-point connection can get the absolute most out of your high speed network. But if you've got more than two PC's on that network, you can still get good use out of gigabit ethernet with 1500-byte frames simply because you have a lot more backplane bandwidth to get all those boxes talking simultaneously.
So -- if you want uber bandwidth between two points, jumbo frames are definitely the way to do it. But if you just want a much faster home network without odd limitations on what other network devices you use, stick with the standard frame size and live with the "only half bandwidth useable"
Why use crossover cables at all? You don't need it with gigabit networking since the equipment autodetects which pairs are senders or receivers... Even a lot of 100mbit stuff works that way, all my dlink shit for example handles straight cables just fine.
Well, just to clarify, not all gigabit equipment works that way. The good stuff does, but there are consumer-grade gigabit adapters out there that just don't work like that.
Thank you for the great explanation! Considering the switch I just bought is a D-LINK unit (hehe) and that I don't want to harm my internet connection, I think I'll follow your advice and stick with 1500 MTU on all the equipment.
By the way, with the D-LINK it works almost as good as with the 24port switch. It's a DGS-1008D 8 port Gigabit Switch, and I got it for 70€ tax included.
Sounds like a good deal! And it sounds like a good plan by staying with the 1500 byte MTU. You won't get full wire speed transfer to each workstation, but you'll probably be able to get ~500mbit to each one individually without having issues talking to other network devices such as future print servers or other servers on the internet.
Cartoon Corpse
Veteran
can you crossover cable Gbit (pc) to a 10/100mbit PCI card (pc)?
just curious. not a networking expert at all...i know very little about it, so "not an expert" is probably an exagerration. lol.
just curious. not a networking expert at all...i know very little about it, so "not an expert" is probably an exagerration. lol.
If you plug in a "standard" crossover cable into a GbE network card, it will only run at 100mb max speed anyway. So to answer your question - yes, you can use a standard crossover cable between GbE and 100mbit cards without issue.
Cartoon Corpse
Veteran
would a spare card-modem cable work? what's the difference between crossover and card-modem cable? if any.
I'm not familiar with the term "card modem", sorry
Cartoon Corpse
Veteran
i just made it up. lol! it's the cable that runs from my LAN card to my modem. sorry, shoulda been more clear.
The cable between your PC and your DSL/Cable modem isn't a "crossover" unit at all. As such, the only time that cable would work is if you're using a set of network cards where at least one of them supports "Audo MDI-X". Most gigabit cards should support this, but you may want to check the documentation to be sure.
Cartoon Corpse
Veteran
thanks, i'll try it when i get home tonight.
That's very weird, because I read quite a while ago that autosensing was part of the gigabit spec to eliminate the need for crossover cables... Probably because many cables only cross the pairs used by 100Mbit, and it would create a lot of irritation and confusion when people can't get their gigabit stuff to work with a standard crossover cable.
Oh well. I guess it wouldn't be the first time computer manufacturers skimp where it comes to following specs...
Cheers for the clarification mate!Similar threads
