There's a sort of vision of what's needed for a high end router:

A multi-core x86-64-based system, fanless, very low TDP, with the CPU probably integrated on the mainboard, and with onboard gigabit ethernet switch controller and ports, and where data bus architecture design is critical.

The conventional PCI bus is obsolete now. A standard 32bit PCI bus has a bandwidth of just 133Mb/s maximum. And where there are multiple masters on that bus - e.g. where a riser board is used to connect multiple gigabit NICs - then each PCI master draws from that maximum 133Mb/s bandwidth. Four gigabit NICs sharing a single 133Mb/s PCI bus isn't going to work.

In theory, the newer x16 PCI-Express bus has a bandwidth of 4GB/s in each direction. However, the low-end mini-ITX boards seem to be limited to x1 or x4 PCI-Express slots. And they max out at 250Mb/s per lane, each way.

If the same PCI-e x1 bus is used for arbitrating multiple PCI-e devices, then the bus traffic is soon going to hit the buffers in the same way as it did on the older PCI-based boards. It's a bit disingenuous even selling a gigabit NIC for use on a 250Mb/s PCI bus!

To build a router board based on the x86-64 to stand the test of time, would probably cost several hundred pounds. And there's not much choice in terms of fanless CPUs with reasonable power to them.

The big question is how deep does the packet inspection need to be? At what layer of the network protocol stack is the filtering going to take place? The deeper that inspection - (i.e. the higher up the stack) - the larger the data queues need to be, the faster the buffer memory must be, and the more processing power that is needed by the router board. That's why BTOpenreach, showing surprising wisdom, kept the HG612 as a fairly primitive device, with just layer 2 filtering (VLAN tags) as standard.

A ballpark figure for such a DIY router board might be £400. My feeble DIY router effort that cost about £150, using a 1200MHz dual-core Athlon64 S1g1 board, turned out to be useless. Because of the limitations of the PCI-e bus on the low-cost Fujitsu-Siemens mini-ITX board that was chosen.

It's a harder exercise than it looks!

cheers, a

Edited by deleted (Sat 26-Jan-13 22:32:33)

You raise very valid points, but I just did some quick research (and thanks for bringing it up, it's very interesting), and it looks like modern chipsets have more or less solved that problem. The motherboard I've shortlisted (the Intel DN2800MT) has the NM10 chipset, which provides 4 PCI Express (PCIe) 2.0 x1 interfaces. Each PCIe 2.0 lane provides 500 MBps (megabytes per second) full-duplex, or 4 Gbps (gigabits per second) full duplex, i.e. 4 Gbps sending and 4 Gbps receiving simultaneously. So in total the NM10 chipset provides 16 Gbps full-duplex (16 send and 16 receive simultaneously). That's a LOT of data to push around. Of the 4 interfaces, one is used by the on-board Gigabit Ethernet controller, two are used by the two mini PCIe slots, and the fourth is provided as a PCIe 2.0 x1 slot (which in my case would have a Gigabit Ethernet card in it). In my opinion Intel has made the perfect choices, for this application anyway.

In addition, two SATA 3 Gbps ports are provided, which hang off the chipset independently (i.e. they don't consume PCIe interfaces), plus a bunch of USB ports, COM and LPT ports, audio, etc.

Even though PCIe 1.1 only provides half the bandwidth that 2.0 does, it's still 2 Gbps each way per lane, which is double what is required for a Gigabit Ethernet interface; so having 4 of them on a mini ITX motherboard would still be at least double what was needed for a very powerful router.

Check out page 18 of this: http://downloadmirror.intel.com/20714/eng/DN2800MT_T...

I worked out the cost (for the smallnetbuilder forum) to be $300 USD including two Intel 6300 3x3 MIMO 802.11N cards, RAM, case, power supply, everything. So maybe £200 - £250 tops. Still a lot more than the £108 the Asus RT-N66U currently goes for, but you're getting something with at least 5x the amount of raw processing power.

Here's the full post:
http://forums.smallnetbuilder.com/showpost.php?p=588...

I completely agree that you have to be very careful with a lot of your choices, and if I do end up building one, I will make every effort to make sure it is as future-proof as possible.

In reply to a post by rotor2k:

...Using the BT-provided Home Hub 3 I can achieve around 310 Mbps...

Your connection is 75x times faster than my maximum over ADSL (No FTTP where I live). *Only* getting 200Mbps from your preferred router is the kind of problem I'd like to have

Sounds like you've made some great choices. Be sure to keep us all informed on progress!

What operating system will the router be running? Some flavour of Linux?

cheers, a

In reply to a post by asbokid:

What operating system will the router be running? Some flavour of Linux?

I really like RouterOS (by a company called Mikrotik). You can get a free version, or there's a very reasonably-priced full-featured commercial license (you can get it for USD $30). I have one running as a VM, and it uses 16 MB of RAM, which is pretty remarkable.

If you have a moment, could you make a spec from www.scan.co.uk and post the link for the items.

In reply to a post by rotor2k:

I don't want to use the HH3 as it is very restricted in its configuration, and e.g. I have no control over the BT-Wifi sharing of my connection to the general public.

What is your objection to sharing?

If you are getting 300Mb/sec it isn't likely to cause much (any?) slowdown.

The data transferred over the Fon bit doesn't come out of your allowance and is completely partitioned away from your network.

Or are you just a misanthrope who dislikes helping others?

In reply to a post by asbokid:

There's a sort of vision of what's needed for a high end router:

A multi-core x86-64-based system, fanless, very low TDP, with the CPU probably integrated on the mainboard, and with onboard gigabit ethernet switch controller and ports, and where data bus architecture design is critical.

The conventional PCI bus is obsolete now. A standard 32bit PCI bus has a bandwidth of just 133Mb/s maximum. And where there are multiple masters on that bus - e.g. where a riser board is used to connect multiple gigabit NICs - then each PCI master draws from that maximum 133Mb/s bandwidth. Four gigabit NICs sharing a single 133Mb/s PCI bus isn't going to work.

In theory, the newer x16 PCI-Express bus has a bandwidth of 4GB/s in each direction. However, the low-end mini-ITX boards seem to be limited to x1 or x4 PCI-Express slots. And they max out at 250Mb/s per lane, each way.

If the same PCI-e x1 bus is used for arbitrating multiple PCI-e devices, then the bus traffic is soon going to hit the buffers in the same way as it did on the older PCI-based boards. It's a bit disingenuous even selling a gigabit NIC for use on a 250Mb/s PCI bus!

To build a router board based on the x86-64 to stand the test of time, would probably cost several hundred pounds. And there's not much choice in terms of fanless CPUs with reasonable power to them.

The big question is how deep does the packet inspection need to be? At what layer of the network protocol stack is the filtering going to take place? The deeper that inspection - (i.e. the higher up the stack) - the larger the data queues need to be, the faster the buffer memory must be, and the more processing power that is needed by the router board. That's why BTOpenreach, showing surprising wisdom, kept the HG612 as a fairly primitive device, with just layer 2 filtering (VLAN tags) as standard.

A ballpark figure for such a DIY router board might be £400. My feeble DIY router effort that cost about £150, using a 1200MHz dual-core Athlon64 S1g1 board, turned out to be useless. Because of the limitations of the PCI-e bus on the low-cost Fujitsu-Siemens mini-ITX board that was chosen.

It's a harder exercise than it looks!

cheers, a

PCI bus is 133 MegaBYTES per second not megabits\s = 1066mbps - plenty fast enough.

Edited by deleted (Sun 27-Jan-13 15:06:02)

In reply to a post by hoopla:

Or are you just a misanthrope who dislikes helping others?

Troll.

Edited by deleted (Sun 27-Jan-13 15:05:44)

In reply to a post by Yaz:

If you have a moment, could you make a spec from www.scan.co.uk and post the link for the items.

Here's the list:

DN2800MT Motherboard £80
http://skinflint.co.uk/746927

1 GB RAM DDR3 SO-DIMM £9
http://skinflint.co.uk/?cat=ramsoddr3&xf=1454_1024#x...

Case (M350) £37
http://linitx.com/product/12488

Riser card + IO shield (to allow a 2nd NIC) £12
http://linitx.com/product/13552

AC Power Adapter £19
http://www.logicsupply.co.uk/power-supplies/ac-adapt...

Additional Intel Gigabit NIC £21
http://skinflint.co.uk/351749

Intel 6300 Ultimate-N 450 Mbps £20
http://skinflint.co.uk/616661

mSATA 32GB £36 (this is a luxury, I would say just boot from a USB stick)
http://skinflint.co.uk/?cat=hdssd&sort=p&xf=2646_mSA...


Total with one Ultimate-N card (and excluding the mSATA): £198
Add £20 for a second card to provide simultaneous dual-band support.

Please note these are all indicative, I haven't researched every last detail in terms of compatibility, but this is the rough bill of materials needed.