Mixing Gigabit, Copper, and Linux

iampgray writes: "With copper-based gigabit cards selling for less than $36 these days, what kind of performance can you expect -- especially in the often-overlooked Linux market? We sought out to test exactly what you could expect from copper-based gigabit solutoins for the desktop interface through the cluster-targeted products. Name brands and off-brands were put through the wringer. How'd they fare? Interesting results to say the least."

Comments

Gigabit and Linux

[GigsVT]

Well, check out the docs first off. It's hard to get much out of GBit, since most of the utilities don't call the socket open with properly sized buffers/window/whatever.

I set up optical gigabit for some NAS type things at work, and out of the box, GBit performed maybe 30% better than 100 Mbit. We are talking about 110Mbit peaks, compared to 80Mbit peaks with 100Mbit switched.

Setting the MTU to 6144 (max that I could set it to with the ns83820.o) I started to get peaks around 300Mbit/sec.

I tried recompiling the module for higher limits, since in the source it has:

#define RX_BUF_SIZE 6144 /* 8192 */

But if I put in 8192, or 9000 like I wanted it to be, it would crask or lock up.

Anyway, it's not trivial to get good performance out of GBit, and definitely don't expect anywhere near 10X gain.

Switches aren't cheap.

[Christopher Thomas]

apparently Pricewatch.com has D-Link 8-port 10/100/1000baseT auto-detect switches listed for under $150!

These are for 8x100-base-T with a gigabit uplink. I researched this a while ago, when speccing out my dream network ;).

The cheapest full-gigabit switch D-link sells is about $1500.

Re:Huh.

[WolfWithoutAClause]

> Are we even to the point when a normal PC could handle Gigabyte?

Yes. Some memory parts are 333 Mhz and are 4 bytes parallel and instructions/s (as opposed to the clock rate) is over 1 GIP I think. So a PC can just about knock out a gigabyte/s if it has to, but it hasn't got much time to think about anything.

But this article is talking about gigaBITs/s. That's 8x slower. So that too.

Cheap NICs, costly switches

[Jah-Wren Ryel]

The cards are well priced for home use, and CAT5E cabling is cheap too. The problem with gigabit ethernet is not the cards, it is the lack of switches or even plain hubs at an affordable price point. There are lots of switches out there with a single gigabit port, but even those are a couple of hundred dollars. If you want multiple gigabit ports, you are looking at more than $600 for the bottom rung products.

My experiences with DGE500T

[redelm]

I bought a pair of DLink DGE500T's about 6 months ago, just to see what I could wring out of them.

I got about 32 MByte/s one-way with `ttcp` [UDP] between a 1.2GHz K7 and 2*500 Celeron (BP-6) through a plain crossover cable.

Not bad, but only 25% of wirespeed (125 MByte/sec). I figured the main limit was the PCI bus, which would only burst at 133 MByte/s, and I strongly suspected that the bursts were too short to achieve anything like this speed. I have yet to play with the PCI latency timer.

One thing for sure -- it isn't the CPU speed or Linux network stacks. The K7 will run both ends of ttcp through the localhost loopback at 570 MByte/s, and the BP6 around 200 MB/s.

Re:I didn't even notice 1000bT was so cheap...

[ncc74656]

Nope... apparently Pricewatch.com has D-Link 8-port 10/100/1000baseT auto-detect switches listed for under $150!

D-Link's site is nearly impossible to navigate (maybe it requires JavaScript, which I've shut off), but the Pricewatch description of the DES-1009G indicates that Gigabit Ethernet is only available on one port as an uplink connection; the rest of the switch is your run-of-the-mill 10/100 job. The DGS-1008T is D-Link's 8-port unmanaged 10/100/1000 switch; the cheapest entry on Pricewatch for that is $595.

BTW, I have the entire site downloaded. Maybe I'm insane to even think about mirroring a /.'ed article on my home cable-modem link, but here it is. I've converted all the charts to PNG so they'll load slightly faster, and I got rid of most of the godawful "super-31337" yellow-on-black text to improve readability. You can also choose this link to download the entire page (images and all) in one shot.

Great uses for gigabit Ethernet on Linux

[IGnatius T Foobar]

Gigabit Ethernet comes in really handy on Linux when you add 802.11q VLAN tagging.

For those of you who don't know how this works, here's a bit of a primer: basically, you set the port on your big data center grade switch to "trunk" and then you enable 802.1q on your Linux box. Then you don't just have one Ethernet interface with one address --- you have up to 4096 virtual ones, each on its own VLAN and each with an IP address that's valid on that VLAN. So you'd have eth0.1, eth0.2, eth0.3, etc... each talking to the machines on that VLAN.

Once you've got that running, you can do all sorts of neat stuff, including:

• A router! You're on every VLAN anyway, so why not? It's not nearly as fast as a hardware-based Layer 3 switching module, but it's several orders of magnitude cheaper.
• Really complex firewalls. You could put different parts of your organization (or whatever) on different VLAN's and then use your nifty Linux box to dictate what kind of policy is used to route between them.
• If you're in a big building with multiple tenants, each with their own VLAN on a shared network, you can reduce the number of Internet access NAT/firewall boxes. Instead of one for each tenant, you've got a single one.
• How about a VPN gateway that can place the caller directly on his or her department's own VLAN instead of having to route to it?

As you can see, it's limited only by your imagination. And with that much stuff potentially running through the box, you're going to need that 1 Gbps of speed. Happy hacking!