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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?
Limitations:
p lane/backplane.HTM
- 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/Back
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.
ICQ# : 30269588
"I used to be an idealist, but I got mugged by reality."
Even if you could buy just an "OS-less" switch, I don't think it would do you any good. Most switches have hardware fast-paths for switching packets. You'd have to completely disable the switching logic, and redirect all frames through the host CPU.
Some of the switch ASICs I'm familiar with [medium range broadcom, vitesse] are in fact slower at sending a packet through the host control interface, than at simply switching it to a port on which a host cpu might be connected. [Reference designs from the above have the host CPU connected to the host interface, and control packets, ssh, telnet, http, depending on the design captured and sent through it]. In that case, you'd need your host CPU to be connected to one of the ports of the switch, and then of course your routing speed is limited to the maximum speed that can be sent through a single port.
One of the posters above me mentioned buying a managed switch and using VLAN's, thats what I woulda suggested had he not beat me to it.
Good Luck!
The poster leaves a lot of stuff out - like what's the bandwidth per port? Are they routing analog dial-up lines or gigabit ethernet? What protocols are they routing? Do they need ACLs? How many? Other filtering? Proxying? And if the installation is really that big, just lay out the $jack for a layer-3 or higher switch or router or firewall or whatever.
Not to be a dick, but if the poster has to Ask Slashdot about this sort of configuration, he or she has no business messing with this and should leave the design and configuration to grown ups (unless it's a lab experiment or something).
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You want to build a router, but you are looking for switch hardware.
You are asking for independent ports. If you need to route through each port seperately and not 'switch' data between ports but 'route' it among them then you need router hardware not switch.
See the thing with switches is that chips are available with 4 ports or 8 ports and it automatically switches data in ASIC between ports. Usually these chips cannot be interfaced to a microcontroller and almost never have PCI interfaces.
You do need individual ports, not a switched collection of ports. So you need something with 7 PCI ports (7x4=28). There are plenty of 4-port PCI cards out there, but there must be 8-port cards too. I have seen plenty of 6-port motherboards. You will have to use PCI extension devices to get to 7 or 8 ports unless you find those 4+ port ethernet cards. Do keep in mind you cannot switch between all ports at wire speed. You'll need faster busses and powerful processors. At this point you're looking at highly specialized hardware like cisco juniper etc.
It is inefficient to route between that many ports on a single CPU. Its better to cascade entire routers if your design allows it or add switches to routers with fewer ports. Unless you are a telco providing high speed connections to ISPs or a central location breaking the bandwidth for many branches, I dont see why anyone will need a router with 30 ports. In any application when you need more processing power, you'd divide the algorithm and use multiple CPUs or multiple computers. In this case you can almost definitely use cascaded routers if you need that many ports in the first place.
I have a Cisco 4700M router with 12 10-mbit ethernet ports. Never needed more than 3.
"Give orange me give eat orange me eat orange give me eat orange give me you." -Nim Chimpsky
Hardware switches can look straight at layer 2 encapsulation and shuffle packets based on that information. The switch's main CPU never sees the packet. The "naked" version of the switch still has enough main CPU in it to program the switch controller chip(s). More "clothed" switches have the spanning tree protocol, SNMP bits, and any other cool features you might have.
Routers have to look at layer 3. Back when I was writing code for a major switch/router manufacturer, most switch chips didn't pass the (de-encapsulated) packet up to the main CPU (or back down). The chip only gave notification that a packet arrived (etc) in the form of an incremented register. This meant the chips were unsuitable for routing because the main CPU had no visibility into the packet whatsoever.
Either of these designs generally require a separate Ethernet NIC for the main CPU, as the switch ports are too busy with external connections. That NIC might be connected to the switch chip on the switch's main board, or it might appear externally as a "management interface port." You'll be programming this NIC, too-- but hopefully, just with ifconfig(1M)
Suggestion: Look for commercial switch chips that can pass the packet to and from the main CPU. Find a company which has a COTS switch with the combination of your favorite switch chip and a CPU that will run your Linux version (or uCLinux). Make sure the implementation hardware is wired properly to be able to get the packets to and from the main CPU-- your favorite chip might have a separate HW interface for communicating with the main CPU that could be unconnected in the implementation hardware. At this point, you essentially have the naked switch that can route. Learn how to boot Linux on the implementation hardware and build a flash filesystem that the switch's bootloader will read. Then start writing code to add the capability you require (to routed?).
Suggestion: Once it works, sell the thing. Or open the source up for others. You went through a lot of trouble to get that capability in the system, and it's got to be so cool because it isn't already in a commercial router. You might consider selling it on the open market yourself, or finding someone to sell it to. Or drop it on Sourceforge for others to upgrade.
Suggestion: Or, you can get your cool feature embodied as an RFC and get the main router vendors to build it in. Or contribute the code to routed(or whatever). You can probably skip the effort of building this one-off switch/router.
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