In telephony, a trunk line is a circuit that connects telephone switchboards (like a PBX system) to individual telephones. Essentially, a trunk contains telephone numbers. One trunk can contain one telephone number or a group of telephone numbers. Users can have a group of trunks that all serve the same or different purposes.
For example, did you know that not all call centers are set for two-way calling?
There are inbound call centers that only receive incoming calls and outbound call centers that only make outgoing calls. Some call centers are equipped to do both. The call center can have a group of trunks, one for inbound, one for outbound and one for two-way calling.
The most common trunk found in telephony is SIP Trunks. To use a SIP trunk, you need:
- A PBX system
- A VoIP telephone
- And an Internet Service Provider (ISP)
A SIP Trunk is a virtual IP conduit that uses the Internet to make and receive calls. Your VoIP provider gives you the trunk, channels and phone numbers. When a user places a phone call, the PBX will connect the call to the SIP Carrier and it will be sent over the internet (thanks to the ISP). It will then arrive at the local switched network of the destination number.
Sounds confusing, but the SIP trunk kind of acts like a tunnel for your phone call. Therefore, it is important for users to protect the front doors of the tunnel (your PBX system) and take precautions to avoid SIP attacks. Unfortunately, businesses using or selling VoIP are exposed to SIP attacks every day. Some of these attacks can cost a company thousands of dollars in seconds!
Bicom Systems offers an extremely effective application that provides real-time protection from various SIP/TFTP/Scanner attacks called sipPROT. Imagine your PBX is a nightclub, sipPROT acts as your doorman checking for IDs. This module works in real-time with live traffic, actively blocking and unblocking IP addresses that threaten the system.