On Wed, 16 Jun 2010 18:31:17 EDT erik quanstrom <quans...@quanstro.net> wrote: > On Wed Jun 16 18:17:45 EDT 2010, n...@lsub.org wrote: > > On programs where I control the client and the server, I simulated > > it by spawning a process that did sleep and then do the write. > > > > That is, you could send many things at once (i.e., same bandwidth) > > but you could pretend the thing was delayed. > > One tricky point was to be sure that sends were still in order, but that > > was a non-issue in my case. > > > > Perhaps being able to trigger delays on ip for testing/measuring > > with a ctl would be a lot better, in the line of what you've done. > > the ethernet, or shim ethernet, device seems like a better place for this.
Agreed. [Thinking aloud...] You'd need some plumbing in devether to demultiplex incoming packets addressed to this device (assuming it has its own MAC address). Something like a tap device would allow you to simulate high latency link, a level-2 bridge or whatever in usercode. [BTW, is there a strong reason why devether.c is in 9/pc/ and not 9/port/? vlan code can be factored out from various ether*.c to a similar portable file (if not devether.c)] > ip is not the only protocol! that's what loopback(3) does, but without > the real network. it would be good to plug loopback or similar into a real > ethernet. it's also worth looking at loopback's implementation strategy, Or bridge(3). > which allows for µs delays. sleep is just too course-grained for my > testing. > > dialing up random reordering would seem to me to be a feature at > this level. A user level simulator will make it easy to add random drops, reordering, filtering, NAT, etc.
