how to measure router WAN to LAN latency

[Jeroen1000]

Hello,

I think for sure Tim is going to know this. So I connected my Laptop (wired) to the WAN port of the router and put it in the same subnet as the (static) WAN IP I assigned to the router.

Next, I connected my desktop to a LAN-port and I put its IP as DMZ in the router.

So, the laptop is in the 10.0.0.x/8 subnet, the desktop is in the 192.168.0.x/24 subnet and is set as the DMZ device in the router. Pinging between the laptop and the desktop (and vice verso) yields a ping of 1ms or lower.

1. Is this a valid test for latency testing? I'm kind of surprised it is so low.
2. Should I test with bigger packets than the standard 32 byte ping?

thanks,
Jeroen

 

[thiggins]

The test is fine and the results sound correct. This is why I stopped testing router latency years ago. ISP latency dominates.

Why would you think router latency would be high?

 

[Jeroen1000]

Well, I have a too large latency variance in the LAN or on the LAN to WAN boundry (> 10 ms up to 35 ms).

Everything up to the router is fine as proven by my latest test. So I now assume the issue occurs when the router is under high load:

- it is a Linksys WRT54GL with DD-WRT capable of routing about 33 megabit.
- I upgraded my internet to 50 megabit and be it coincidence or not, I'm having issues now.

So the router is the only device that could choke. I don't think ping will actually make it break a sweat and it is not designed to stress-test anyways.
How would one test this? Connect a switch to the WAN port and then 2 workstations to the switch. Download a large file from one of the workstations, while pinging the other?

I'm looking for something that measures latency while stressing the router. IXchariot may be able to do this but that would be a costly test me thinks

 

[thiggins]

How are you detecting the latency issue?

To run your proposed test, you would need four computers. Two to do the file transfer and the other two to run the ping test. Otherwise you risk interaction.

If your router is slower than your Internet link, you should replace it or it will be a choke point.

 

[Thatguy]

Force NIC

I would also force your NIC link speed and WAN link speed to match. Auto-negotiate can act funny sometimes. Typically one of the first things I do when troubleshooting network latency. Gotta start with the basics right?

 

[Jeroen1000]

Partly because of the feeling of slowness and some confirmation when I was using bittorrent, the ping (ping -n 100 or even more packets) to my ISP's 'speedtest server' and other addressess I know well, was very variable during the download. When the download stopped, it was fine again although it sometimes takes a while to return to normal.

So it is either too many connections, or too high a load for the router to sustain, too large packets, or whatever (perhaps it treats ping at a lower priority than TCP or UDP when the load gets too high).

But, since ping is inherently variable over the internet I want to perform some tests in a more controlled environment.

A file transfer test would probably help to induce a high load, but it does not make as many connections as bitorrent does so it might still not make the issue apparent.

I'm googling for some tools that can simulate certain loads while keeping latency statistics but feel free to recommend something .

 

[thiggins]

Or just get a router with higher throughput. The WRT54GL is pretty long in the tooth.

 

[onnoossendrijver]

You should NOT disable autonegotiation on home-targeted equipment. Messing with negotiation can severely affect speed in a negative way.
Like Tim says the WRT54G has a very limited cpu by todays standards. I think you need a faster router for your 50 mbit/s internet connection.