Scaling Asterisk with Kamailio

Astricon 2020 Fred Posner
Scaling with Kamailio
Using Kamailio and Asterisk to
Create Secure and Scalable Solutions

Kamawhat?
●
Kah-mah-illie-oh
●
Hawaiian Word
●
To communicate

Who am I?
●
Fred Posner
●
qxork.com
●
@fredposner
●
Consultant

Agenda
●
What is Kamailio?
●
What’s new in
Kamailio 5.4?
●
Common Deployment
Scenarios
●
Examples

What is Kamailio?

What is Kamailio
●
SIP proxy server
●
SIP registrar server
●
SIP location server
●
SIP application server
●
SIP dispatcher server
●
SIP websocket server

What isn’t Kamailio?

Kamailio cannot be...
●
B2BUA
●
SIP Phone
●
Media server*

Selected Benefits
●
Open Source
●
Longevity
●
Small Footprint
●
Interoperability
●
Fast
●
Modular

Kamailio is Modular

Selected Modules: HTABLE
●
Hash Table Module
●
Stored in shared
memory
●
Custom cache system
●
Replication via DMQ

Selected Modules: KEMI
●
Python
●
LUA
●
JavaScript
●
Ruby
●
Squirrel
●
https://kamailio.org/docs/
tutorials/devel/kamailio-
kemi-framework/
●
Use other scripting
languages to write SIP
routing

Selected Modules: DMQ
●
Distributed Message
Queue
●
Replicate data to
other Kamailio nodes

Selected Modules: Dispatcher
●
SIP Load Balancer
●
Stateless, Lightweight
●
Various Algorithms
●
New: Latency based
dispatching

What’s new in 5.4?

New Modules: Kafka / DLGS
●
Produces and sends
messages to a Kafka
server
●
Tracks dialogs in
stateless mode

New Modules: MQTT / SECSIPID
●
Bidirectional
publish/subscribe
communication to a
MQTT Broker
●
STIR and SHAKEN IETF
extensions for SIP
(RFC8224, RFC 8588)

New in 5.4
●
New modules: 5
●
Updated modules: 70
●
KEMI optimizations
●
Core updates
●
And mucho, mucho mas

Common Deployment Scenarios

Simple Edge Router

Bridge

Dispatcher / Load Balancer

Examples

Blocking by User-Agent - $ua
if($ua =~ "friendly-scanner|sipcli|sipvicious|VaxSIPUserAgent") {
# silent drop for scanners - uncomment next line if want to reply
# sl_send_reply("200", "OK");
exit;
}

Adding to HTABLE
if($sht(ipban=>$si)!=$null) {
# ip is already blocked
xdbg("request from blocked IP - $rm from $fu (IP:$si:$sp)n");
exit;
}
...
if($ua =~ "friendly-scanner|sipcli|sipvicious|VaxSIPUserAgent") {
$sht(ipban=>$si) = 1;
# silent drop for scanners - uncomment next line if want to reply
# sl_send_reply("200", "OK");
exit;
}

Dispatching Requests
# Dispatch requests
route[DISPATCH] {
# round robin dispatching on gateways group '1'
if(!ds_select_dst("1", "4")) {
send_reply("404", "No destination");
exit;
}
xdbg("--- SCRIPT: going to <$ru> via <$du> (attrs: $xavp(_dsdst_=>attrs))n");
t_on_failure("RTF_DISPATCH");
route(RELAY);
exit;
}

# Try next destionations in failure route
failure_route[RTF_DISPATCH] {
if (t_is_canceled()) {
exit;
}
# next DST - only for 500 or local timeout
if (t_check_status("500")
or (t_branch_timeout() and !t_branch_replied())) {
if(ds_next_dst()) {
xdbg("--- SCRIPT: retrying to <$ru> via <$du> (attrs: $xavp(_dsdst_=>attrs))n");
t_on_failure("RTF_DISPATCH");
route(RELAY);
exit;
}
}
}

event_route[dispatcher:dst-down] {
xlog("L_ERR", "Destination down: $rm
$ru ($du)n");
http_client_query("$var(pagerduty)",
"$var(response)");
}

Failure Routes FTW
●
Check for reply, CANCEL, status code
●
Can be set as needed
if (t_check_status("5[0-9][0-9]")){
# I do not like the 5xx responses,
# so I give another chance to "foobar.com",
# and I drop all the replies to make sure that
# they are not forwarded to the caller.
t_drop_replies();
rewritehostport("foobar.com");
append_branch();
t_relay();
}

Fail / Reply / Branching / Serial
●
Status checks
●
CANCEL checks
●
Use your own logic to supply what to do
●
Great also for PSTN

Thank You!
●
kamailio.org
●
Mail lists, IRC, Matrix
●
YouTube (kamailioworld)
●
@kamailio

Scaling Asterisk with Kamailio

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