GTP Tunnel Calculator
Size GTP-U transport for a bearer population, including encapsulation overhead and packet-per-second load.
Inputs
Encapsulated Transport Load
31.350Gbps
User-Plane Payload
30.000Gbps
Encapsulation Overhead
4.50%
Packet Rate
4.688Mpps
Step by step
Values used
Active bearers = 200,000 bearers; Average throughput per bearer = 150 kbps; Average user packet size = 800 bytes; GTP-U + UDP + IP header = 36 bytes
GTP Tunnel
transport = user payload × (1 + header bytes ÷ average packet size); packet rate = payload bits ÷ (packet size × 8).
Encapsulated Transport Load
= 31.350 Gbps
User-Plane Payload
= 30.000 Gbps
Encapsulation Overhead
= 4.50
Packet Rate
= 4.688 Mpps
How it works
GTP-U wraps every user packet in an 8-byte GTP header, an 8-byte UDP header and a 20-byte outer IP header. Because that cost is per packet, the percentage overhead depends entirely on the average packet size — small-packet traffic such as signalling or gaming pays far more than bulk video. S1-U and N3 backhaul is dimensioned in Gbps but policed in packets per second, and forgetting 36 bytes of encapsulation is a reliable way to saturate a link at 96% of its nominal capacity.
Formula
GTP Tunnel
transport = user payload × (1 + header bytes ÷ average packet size); packet rate = payload bits ÷ (packet size × 8).
- header bytes
- GTP-U 8 + UDP 8 + outer IPv4 20 = 36
- payload
- bearers × average per-bearer rate
Frequently Asked Questions
How is GTP Tunnel calculated?
transport = user payload × (1 + header bytes ÷ average packet size); packet rate = payload bits ÷ (packet size × 8). GTP-U wraps every user packet in an 8-byte GTP header, an 8-byte UDP header and a 20-byte outer IP header. Because that cost is per packet, the percentage overhead depends entirely on the average packet size — small-packet traffic such as signalling or gaming pays far more than bulk video.
Why does GTP Tunnel matter?
S1-U and N3 backhaul is dimensioned in Gbps but policed in packets per second, and forgetting 36 bytes of encapsulation is a reliable way to saturate a link at 96% of its nominal capacity.
What values do I need to enter?
This calculator takes 4 inputs: Active bearers, Average throughput per bearer, Average user packet size, GTP-U + UDP + IP header. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.