thinQmaster Virtual testing partner Adaptive practice exams that find your weak spots and drill them. Every answer explained. From $69
Enroll

thinQmaster

Find your exam

Five questions free, before you decide.

Step 1 · choose a vendor

In one of our camps? Your practice exams come with the tuition — they are on your study page already.

Commonly confused · Collaboration, Voice & AV

PRI vs SIP Trunk: What's the Difference?

A PRI is a traditional digital circuit that delivers a fixed number of voice channels over a T1 or E1 line. A SIP trunk delivers voice service over an IP connection, scales by simply adding concurrent call capacity, and is usually cheaper and more flexible.

PRI (ISDN Primary Rate Interface)

vs
PRISIP Trunk
TransportDedicated T1/E1 circuitIP network (Internet or private WAN)
ChannelsT1: 23 bearer + 1 D channel; E1: 30 bearer + 1 D (plus framing)Concurrent calls limited by license and bandwidth
SignalingQ.931 on the D channelSIP
ScalingAdd whole circuitsAdd call paths in software
HardwareVoice gateway with PRI interfaceSession Border Controller (CUBE or similar)
CostHigherLower
Disaster recoveryTied to a physical locationCalls can be rerouted to other sites easily
Remember it

PRI is a fixed bundle of 23 phone lines on copper; SIP trunks are phone lines delivered as data.

Exam tip

Know the channel counts for T1 PRI (23B+D) and E1 PRI (30B+D), and that SIP trunks connect through a session border controller. Bandwidth per call depends on the codec chosen.

Tested on

More Collaboration, Voice & AV look-alikes