Using Kamailio and Asterisk to Create Secure and Scalable Solutions

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

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

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

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

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What is Kamailio?

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

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What isn’t Kamailio?

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

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Selected Benefits
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Open Source
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Longevity
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Small Footprint
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Interoperability
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Fast
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Modular

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Kamailio is Modular

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

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

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

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

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What’s new in 5.4?

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

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

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

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Common Deployment Scenarios

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Simple Edge Router

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Bridge

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Bridge

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Dispatcher / Load Balancer

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Dispatcher / Load Balancer

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Examples

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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;
}

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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;
}

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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;
}

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Dispatching Requests
# 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;
}
}
}

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

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Failure Routes FTW
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Check for reply, CANCEL, status code
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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();
}

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

37. Astricon 2020 Fred Posner
Thank You!
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kamailio.org
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Mail lists, IRC, Matrix
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YouTube (kamailioworld)
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@kamailio