[Spce-user] Limit CPS per peer gw

Jon Bonilla (Manwe) manwe at sipdoc.net
Mon Aug 8 17:07:28 EDT 2022

Hi all

Recently a customer of mine (Questblue Inc) asked me a way of limiting CAPS
to their peer gateways. So I created a custom preference and a patch for them.

Here's de howto:

- Create a peer preference custom_caps to set the maximum number of INVITE
request per second a peer gateway could allow (attached

- Send the preference to the lb in proxy.cfg:

if(pv_isset("$xavp(callee_peer_prefs[0]=>custom_caps)")) {
  $(x_hdr(P-QB-CAPS)[*]) = $xavp(callee_peer_prefs[0]=>custom_caps);

- whitelist the header in sems sbcprofile (trivial)

- Add a new htable entry in lb (I also added separate timer processes for high

modparam("htable", "htable", "caps=>size=11;initval=0;autoexpire=5;")
modparam("htable", "timer_interval", 10)
modparam("htable", "timer_procs", 4)

- Set the logic in the kamailio lb to check for caps:

if(is_present_hf("P-QB-CAPS")) {
  $var(cps) = $rd + ":" + $timef(%S);
  $var(cps) = $shtinc(caps=>$var(cps));
  $var(capslimit) = $hdr(P-QB-CAPS);
  if ($var(cps) > $var(capslimit)) {
     sl_send_reply("503", "CAPS limit reached for this destination $rd");

I'm using $rd because my customer doesn't use "hostname" in the gw definition
but it could be changed for destination IP based on P-D-URI or similar.

This setup has been running in Questblue's sip:carrier like spce cluster with
more than 1500CAPS of traffic without issues.

Questblue agrees on upstreaming this patch if Sipwise is interested on it. I
think it can be a useful feature.



PekePBX, the multitenant PBX solution
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