[SR-Users] [OT] sems [and kamailio] in risk-of-life service

[Daniel-Constantin Mierla]

just forwarding from SEMS mailing list an interesting story of using 
kamailio and sems in emergency services...

-------- Original Message --------
Subject: 	[Sems] sems in risk-of-life service
Date: 	Thu, 24 May 2012 15:29:38 +0800
From: 	Jeremy A <jeremy at electrosilk.net>
To: 	sems at lists.iptel.org



Hi,

This is a belated report on the use of SEMS in a risk of life service.

The system uses kamailio in a distributed architecture of dozens of Fire 
& Rescue stations. This is heavily based on distributed and replicated DNS.

A single '911' style headquarters has duplicate hot swap-over control 
rooms at other locations.

The headquarter and alternate posts have servers that service HQ 
operator positions with SIP phones. These provides sidecar indication of 
F&R Station state for up to 64 F&R stations - using BLF. These phones 
are hooked into an integrated analogue audio management system.

Each Fire and Rescue station has an embedded SIP based controller that 
runs Kamailio and proprietary software to control the F&R station 
electrical and safety systems as well as provide public address 
functions to alert the F&R staff of a new emergency. These PA 
announcements are SIP based using a DSL network and are live from the HQ 
positions, plus computer synthesized voice, as well as alerting tones.

Each station also has multiple SIP phones for in-station and station to 
station calling.

The network is decentralized so failure of the central control system 
still allows point to point communications between Fire and Rescue stations.

The headquarter systems uses SEMS as the primary operator manager to 
perform multiple simultaneous deployment calls to remote Fire and Rescue 
stations. SEMS is used to create a dynamic conference between an 
operator and multiple Fire & Rescue stations. These are automatically 
initiated by SEMS and answered by the F&R embedded systems. This means 
an operator can broadcast a deployment message and initiate station 
control activities at up to five stations (fifth alarm) This is only 
constrained by the bandwidth available at the headquarters. Our SEMS 
packages have been designed to handle non-answered calls to the 
conference and provide operator indication by 'SMS' messages to the 
handsets and audio feedback.

The system provides full forensic recording by using rtpproxy at all 
locations. These recordings are archived by an out-of-band process.

Control of the system is purely SIP based - so every item in the system 
is a SIP based entity. This includes servers, embedded systems, and phones.

The phones are physically integrated into operator positions that also 
handle PSTN, PBX, and radio traffic. The interface is purely keyboard on 
the operator phones.

Options for integration of the SIP system into CAD (Computer Aided 
Dispatch) are obvious. The only drawback is the rusty and ancient 
systems and the unbelievable process required to get approval to integrate.

The system as provided provides at least 5 nines reliability. Probably a 
lot better. The only downside is the DSL network (provided by others at 
amazing expense) that provides a system with a lousy 2 nines 
reliability. We are in the process of developing an offering using 
redundant DLS/3G routing to improve this.

The field stations are a hybrid Centos 5/Slax  system running out of 
flash. The HQ systems are straight Centos 5 systems running off disk or 
off flash. Future versions will be pure Centos out of flash with no 
fancy memory overlay - flash is well good enough.

The system has been live for over a year with no major issues. I can't 
say how many lives have been saved, but certainly quite a few. At least 
we haven't been sued yet :-)

Cheers.



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