ANSWER:

tc, iptables etc can all do this, but just to be different:

You can use Linux kernel feature cgroups and its net_cls module for limiting xapian-replicate-server. Something like this should do:

mount -t cgroup -onet net /sys/fs/cgroup
cd /sys/fs/cgroup
mkdir xapian-replicate-server
/bin/echo $$ > xapian-replicate-server/tasks
/bin/echo 2048 > xapian-replicate-server/net.tcp
/bin/echo 4096 > xapian-replicate-server/net.tot
however_you_launch_xapian-replicate-server

This would create a new cgroup for Xapian and give it total of 2048 kilobytes/s TCP traffic bandwidth and 4096 kilobytes/s of total whatever network traffic bandwidth.

by Janne Pikkarainen from http://serverfault.com/questions/382551