SIP.edu at Columbia

Networking > SIP.edu at Columbia

Introduction

Columbia is a parcitipant in the Internet2 Voice over IP Working Group's SIP.edu initiative which has the goal of SIP-enabling plain old telephone users via SIP to POTS gateways.

The Gateway

We have a bidirectional Cisco 2600 SIP gateway which is connected to the campus Siemens telephone switch via a PRI (T1) line. Incoming calls can be placed to this gateway via a small number of direct inward dialing numbers. For example, a call to +1 212-851-7548 will be routed from the Siemens to the gateway which in turn has a voice-peer with our SIP proxy. Finally, sip:[email protected] is an alias to my sip uri of sip:[email protected] so my IP phone(s) ring.

Outgoing calls are routed to the gateway via the SIP Proxy.

Using our LDAP directory from the SIP Proxy

We use the SIP Express Router from iptel.org. This is a GPL'd proxy that works great. Adding the LDAP lookup was easy. Right after SER looks in the user location database for a registered user agent and fails to find it, we added a call to an external script via the exec_dset() module:

 # native SIP destinations are handled using our USRLOC DB
 if (!lookup("location")) {
     if (!exec_dset("/etc/ser/sipldap")) {
          sl_send_reply("404", "Not Found");
          break;
     } else {
          log(1," sipldap call");
     };
 }; #!lookup

This script simply does an LDAP query for mail=user@columbia.edu or uni=uni and returns the telephonenumber attribute, rewritten as a sip uri that incorporates our various local tieline hacks:

#!/bin/sh
echo "$*" >/tmp/sipldap.log
m=`echo $1 | sed -e 's/^sip://'`
u=`echo $m | sed -e 's/@columbia.edu$//'`
f="(|(mail=$m)(uni=$u))"
num=`ldapsearch -LLL -b "" -P 2 -x -h ldap.cc.columbia.edu $f telephonenumber \
| grep '^telephonenumber' | sed -e 's/^telephonenumber: //'`

if [ -z "$num" ]
then
  echo "$*"
  exit 1
fi
num=`echo $num | sed -e 's/^+1 212-85\([1347]\)-\(....\)/\1\[email protected]/' \
		     -e 's/^+1 212-30\(5\)-\(....\)/51\1\[email protected]/' \
		     -e 's/^+1 845-365-\(....\)/95\[email protected]/' \
		     -e 's/^+1 212-678-\(....\)/94\[email protected]/' \
		     -e 's/^+1 212-870-\(....\)/80\[email protected]/' \
		     -e 's/^+1 212-939-\(....\)/\[email protected]/' \
		     -e 's/^+\(1\) \(...\)-\(...\)-\(....\)/93\1\2\3\[email protected]/'`
echo $num >>/tmp/sipldap.log
echo sip:$num
exit 0

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