Can You Purchase Switch Hardware Without an OS?

dhahn asks: "I have a project where I'm building a large Linux router (about 40 ports or so). At this point, my only hardware solution is to purchase a box with lots of PCI-ish slots and fill them multi-port ethernet cards. I've looked into currently available solutions and haven't found anything that gives me the control I want. Does anyone know of where I could purchase a 'naked switch?' I just want the switch hardware with enough guts to allow me to customize a Linux OS and load it up." If anyone else has been in this situation, what did you do?

Comments

bandwidth limitations, and large PCI backplanes

[Robbat2]

Limitations:
- PCI bus bandwidth is going to hurt you hard. 32-bit PCI @ 33Mhz = 127Mbyte/sec. 64-bit PCI-X @ 66Mhz = 508Mbyte/sec.
- 100Mbit ethernet = ~10Mbyte/sec (assume 10b8 encoding, easier numbers).
- 127Mbyte/sec / ~10Mbyte/sec = 12 100Mbit ports only.

If you aren't deterred by this:
1. Get a motherboard.
2. Get a decent PCI backplane. A quick Google search brings this company:
http://www.commell.com.tw/Product/Peripheral/Backp lane/backplane.HTM
and they have a backplane with 17 PCI slots.
3. Buy 4-port PCI 100mbit network cards (http://www.americanpredator.com they don't list it on their site, but I'm certain they do custom quad port cards, or can point you to somebody that can, $500/card for industrial grade hardware).
4. 17*4 = 68x 100Mbit ethernet ports.

Re:bandwidth limitations, and large PCI backplanes

[kneecap]

Use PCI Express instead, it has dedicated serial bandwidth to each slot instead of shared bandwidth for all PCI or PCI-X slots connected to a PCI controler.

From http://en.wikipedia.org/wiki/List_of_device_bandwi dths
PCI 32-bit/33 MHz 1066.66 Mbit/s 133.33 MB/s
PCI Express (x1 link) 2500 Mbit/s 250 MB/s
PCI 64-bit/33 MHz 2133.33 Mbit/s 266.66 MB/s
PCI 32-bit/66 MHz 2133.33 Mbit/s 266.66 MB/s
PCI 64-bit/66 MHz 4266.66 Mbit/s 533.33 MB/s
PCI-X 133 8533.33 Mbit/s 1066.66 MB/s
PCI Express (x4 link) 10000 Mbit/s 1000 MB/s
PCI Express (x8 link) 20.00 Gbit/s 2 GB/s
PCI Express (x16 link) 40.0 Gbit/s 4 GB/s

The big routers and switches use PCI/PCI-X on their backplanes and when some of them started doing 10Gig ethernet ports the ran into the PCI-X bandwidth limit of abouth 8.5 Gbit. So do like Cisco & the others did and start using PCI-E. I saw another post here mentioning multiport gigabit ethernet cards for PCI-E slots made by Silicom: http://www.silicom-usa.com/

Re:VLAN

[silas_moeckel]

Your numbers are fairly correct, the biggest interface that you can buy for a PC is 10ge assuming multiple cards per server you can get some decent bandwidth. Now PC's are not designed to do this they have high latency's and comparatively slow bus speeds as compared to say a cisco 6509 (very common managed switch) I would assume that they are looking to something more complex than just switching.

linuxdevices

[marros]

If you go to www.linuxdevices.com and look around, there are several vendors who sell sbc's that have ethernet switches as backplanes, you can add as many as you want. The underlying cpu is either a strong arm, or x86 compat cpu, some have mini-pci slots, etc. And they all run linux!

Re:VLAN

[operagost]

You do realize that 64-bit, 66 MHz PCI cards are readily available and nearly universally supported in enterprise hardware? And that PCI-X cards running at 133 MHz are not exotic? Oh yeah... and there's PCI-Express.

You're not even correct about the crossover. Automatic crossover is supported on all kinds of 100baseT gear, although it is not required as it is in the 1000baseT standard (because the Fast Ethernet standard predates the tech).

Re:VLAN

[Short Circuit]

Thanks for the info. And the civil tone.