[Dnsmasq-discuss] slowing down dhcp

[Eric Johansson]

I have some really old ip phones (polycom ip 430). they are sending lease
requests but it ooks like they are not catching the reply. I put dnsmasq
on a vm (on a slower system) and the phone starts to catch the requests
after 4-5 tries. I'm interpreting this as phones that are too slow for the
modern network

any idea on how I can slow down just the dhcp exchange to test out this
conjecture?

[Rick Jones]

Post by Eric Johansson
I have some really old ip phones (polycom ip 430). they are sending
lease requests but it ooks like they are not catching the reply. I put
dnsmasq on a vm (on a slower system) and the phone starts to catch the
requests after 4-5 tries. I'm interpreting this as phones that are too
slow for the modern network
any idea on how I can slow down just the dhcp exchange to test out
this conjecture?

Under Linux there is something called "netem" (network emulator) which
can be pushed onto the stack as a tc qdisc to control bandwidth and
delay among other things. I've only used it "universally" rather than
trying to slow-down just a specific traffic type, but I suspect it may
be possible to do some filtering/marking/whatnot to get the DHCP traffic
as the only traffic affected.

Under *BSD I think similar functionality can be found in something
called "dummynet."

Of course, if you were to build dnsmasq from source, you could probably
just put a sleep/usleep/whatnot somewhere in the reply path.

happy benchmarking,

rick jones