Detailed performance specifications for routers? X-post

[David]

Some time back I was pointed to detailed specifications of various routers; I think it was related to DD-WRT.

This included things like CPU power.

Ah!

Can someone please remind me how to extrapolate from there to the expected peak performance?

For example the WZR-600DHP2 I am currently using to front my network behind a Virgin Media Super Hub shows the processor as "Broadcom BCM47081A0 @800" whilst the TP-Ling TP-WDR3600 shows the processor as "Atheros AR9344 @560".

I know the Buffalo can support 165 Mb/sec but the TP-Link can't seem to get above 140 Mb/sec when connected to the Super Hub.

The difference in CPU frequency might explain this, but both include a Gigabit switch so the assumption is that they can switch internally at Gigabit speeds.

Not that I am relying on that as I have a separate Gigabit switch to support the wired network in the house.

So how can you estimate what the maximum line speed is that a cable router can support?

As usual Google (or DuckDuckGo) Fu is not my friend today.

Cheers

Dave R

[John Rumm]

Switching speeds are a very different from routing speeds. Switches these days are all hardware, and most will have the capability to run all ports flat out - at least in the Domestic and SOHO market.

You can't easily. There are many factors that will have an impact - many related to usage (how many clients, are you running NAT, doing VPN pass through, and even what applications are you running). The CPU and RAM will have a significant effect on that, although some routers will have hardware assistance for some tasks, and hence rely on shear CPU grunt alone less.

Searching out the maximum throughput on the router spec would probably be a better way, or failing that, running one and making your own measurements.

[dennis]

Routers can also be virtually all hardware, you just need a big enough CAM to hold the routing table for the most used routes. They can have computed the exit point before the rest of the frame has arrived and hence updated it and linked it ready to go.

Then the odd one that results in a CAM miss will have to be processed by a CPU, that CPU can be a big wide one dedicated to matching routes.

The big problem is computing the routes if you have to match a lot of IPv4 address scattered around at random.

There are a lot of updates and if the router crashes it can take quite a while to recover the routing table. This is why it can take hours to recover if a big node goes down on the internet.

Hopefully IPv6 will fix this problem unless some idiots start handing out the wrong type of address to the wrong people.

I don't expect many SOHO routers to do much in hardware other than what the chip manufacturers build into their chips. Most just use one chip for a switch and ~one chip and a cpu for a router. More chips for more ports I have seen 12 port chips but that was a few years ago when I was actively looking at routers, I expect there are much better chips now.

[The Natural Philosopher]

+1. No CPU involved really.

I suspect most routers can basically support line speed more easily than they can support multiple NAT sessions.

and from my persoective line speed is a function of ADSL/VDSL type hardware rather than the CPU grunt. But of course yours is simply acting as an edge router behidn a cable mode,mm. so thats not in the equation.

And actual download speeds are more a function of internet congestion than pure lines speed.

You could put a computer on the WAN port and try a transfer between that and the LAN ports and te WiFi.

.

[Theo]

*Can be*. Not necessarily are. And the routing bit is easy, but NAT/firewall/VPN/DPI/etc are often implemented in software.

A lot of chips are just a slower-than-phone CPU with some basic networking hardware, possibly with a little bit of support for NAT offload and some crypto. Frequently the drivers for those aren't open source, so if you install a different OS on the router you just get a ~500MHz single core CPU with no hardware acceleration for networking.

good for finding what's inside things.

Theo

[dennis]

I don't think we are talking about the same things. Think in terms of hundreds of thousands of routes in the table and a couple o hundred interfaces. CPUs with enough cpu power and memory to run a database of the entire UK population with hundred of queries a second and you might get the idea.

[Theo]

We aren't. The OP asked about a router to connect to their home broadband, not for a Facebook datacenter. That doesn't have thousands of routes in the table and a hundred interfaces. It has two interfaces and exactly two routes. It also costs about fifty quid, and sometimes isn't very good at what it does.

Theo

[dennis]

But that is why I stated you wouldn't find them in a SOHO router in the post you replied to.