SIP Trunking Glossary – Part I

We firmly believe that you don’t need to be a telecommunications expert to resell SIP trunking services or to use them. In fact, we think it is best to avoid using very technical terms that might make the approach seem intimidating to customers with limited technical resources. Having said that, however, there are a few key terms that it is helpful to understand. The field of telecommunications is full of arcane terms and acronyms, so this list is nowhere near exhaustive, but it covers the most important basics.

ATA (Analog Telephone Adaptor) – An ATA is a small, inexpensive device that connects conventional telephones, PBX systems, fax machines, door alarms and similar hardware to a digital telephone system or internet-based telephony network. An ATA can be used to connect PBX and key systems that are not internet enabled to a SIP trunking solution.

E911 – E911 is short for Enhanced 911. It is used to deliver a physical address, set by the customer, to the Public Safety Answering Point when a customer dials 911. This is built in to land lines, but calls made over the internet or cellular networks require this special service to automatically deliver the address and ensure a rapid response to the right place.

IP (Internet Protocol) – IP sets the rules for how data is moved between the destination and the source. It is the network layer protocol in the TCP/IP communications protocol suite. Telecommunications hardware that is designed for use over the internet is commonly called “IP enabled.” IP enabled phones may be referred to as “SIP Phones” or “VoIP Phones.”

Jitter – The term Jitter is used to describe quick fluctuations in the transmission of voice over the Internet. It results in a poor quality audio experience for callers. In SIP trunking, it may result from an abrupt variation in signal characteristics, such as when a data packet arrives either ahead or behind a standard clock cycle. It may also be caused by other data demands on the network.

Latency – Latency is the time between the moment a voice packet is transmitted and the moment it reaches its destination. This delay may be in nanoseconds but it is still used to judge the efficiency of networks. Too much latency in SIP trunking can make calls sound choppy.

PBX (Private Branch Exchange) – A PBX is the hardware and software that comprise a business telephone system.  Most modern PBX systems are IP enabled.

POTS (Plain Old Telephone Service) – Plain old telephone service is used to describe a single phone line with a single phone number. If you have a home phone, or dedicated analog FAX line, it is probably POTS.

PRI (Primary Rate Interface) – PRI is a physical connection to the public telephone network over a dedicated line that only serves voice transmission. Traditional business telephone systems leverage PRI, to which SIP is an alternative.

PSTN (Public Switched Telephone Network) – The PSTN is the combination of local, long-distance, and international carriers that make up the worldwide telephone network. It is the reason that any phone can dial any other phone.

QoS (Quality of Service) – QoS is a router setting that prioritizes voice traffic over data traffic. This improves the quality of SIP calls by making it so that other data demands don’t interfere with voice calls.

SIP (Session Initiation Protocol) – Session Initiation Protocol (SIP) is communications protocol used for conducting multi-media communication like voice and video calls using Internet networks.  It controls messages that are sent between various devices on the network and manages establishment, termination and other elements of the call.

SIP Channel – A SIP channel represents one connection to the PSTN. SIP trunks can have an unlimited number of channels, with each channel handling one concurrent telephone call. The number of SIP channels each business needs varies depending on call volume.

VoIP (Voice over IP) – Voice over Internet Protocol (VoIP) is a group of technologies that work to deliver voice and other multimedia sessions over Internet Protocol (IP) networks, most commonly the Internet.  SIP trunking is one method of achieving VoIP, others include the public internet and private point-to-point networks.

Our aim in this blog is to use language that most people will find accessible, but these terms are important to what we do. If you are new to the world of SIP trunking, hopefully this post has helped everything make a little bit more sense. In our next post, we’ll cover more telephony terms to know.