Simulating Network Latency?

ixmo asks: "I've just come around an interesting problem: to simulate low-bandwidth network links without buying expensive WAN simulators, I can connect two old Cisco routers back to back with serial cables, and control the bandwidth via the 'clock rate' IOS command, but how can I simulate network latency? Is there some OS tool or patch (for Linux/OpenBSD) that allows for tuning of network delay? Any hints?"

Comments

Download a copy of SP2

[Marxist Hacker 42]

This may be the oddest use for this yet- but any large file would work >200MB. Set up your Serial port for a slow connection, say 110 baud, then start an ftp transfer in the background of SP2 from one machine to the other. That ought to simulate latency errors just fine.

Re:In related news

[SuiteSisterMary]

Go type 'southern hemisphere monitors' into Google.

use a traffic limiter (shaper)

[wotevah]

Use a bandwidth limiter that throttles your send rate. Someone else mentioned PF for BSD. On linux you can use the shaper module. My old notes go something like this, it might still work. Assuming eth0 is your output interface (the limiter works only on outgoing traffic, so you need the other end to do the same):

modprobe shaper
shapecfg attach shaper0 eth0
shapecfg speed shaper0 9600 # in baud
ifconfig shaper0 <eth0-address> netmask <eth0-netmask>
# remote automatic route added by above
route del -net <eth0-network> netmask <eth0-netmask> dev shaper0
# add routes to be choked
route add -host <otherhost> dev shaper0
# or if going through a router
route add -net <othernet> gw <router> dev shaper0

...you get the idea. I wonder if iptools makes this a bit less hacky.