[Kea-users] Congestion Handling/General Perf Tuning

Dave Swager dave at waveville.net
Wed Jun 17 19:41:12 UTC 2020

We run a moderately busy (~200qps) kea-1.6.2. hot-standby pair of servers.
Clients are handed dynamic addresses from multiple large dedicated pools
serviced via Cisco DHCP proxy, i.e. the Cisco router "spoofs" the servers
functionality by rewriting GIADDR and source IP in the server's reply
packets. Leases are in memfile.

We've experienced service impairment/outages a couple times whose symptoms
are described in kea's congestion handling documentation
although we haven't gone deep enough into tcpdumps to make a hard
correlation. Implementation of congestion handling seems to have
alleviated the problem.

When problems were occurring, CPU/Memory showed nowhere near capacity,
leading me to think that it's possible we could simply do some system
tuning to address this rather than the congestion handling.

What I'm looking for here are some general recommendations in terms of best
practice, e.g:
- Can we substitute tuning of appropriate system buffers for the ring
buffer and if so how?
- If the ring buffer is the best solution, what is the best way to
appropriately monitor/size it?
- Any other recommendations?


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