Migration Impact Model · v1.0
The PQC bandwidth calculator
A first-approximation model for the network capacity impact of hybrid post-quantum cryptography on TLS and VPN traffic at the enterprise scale. Designed for capacity planning, not measurement.
Organisation01
Total users
5,000
Remote / VPN users
30%
New TLS handshakes / user / day
2,000
Peak-hour concentration
3.5×
Cryptography02
X25519 + ML-KEM-768
Classical signatures retained.
Handshake delta: ~2,300 B
Classical signatures retained.
Handshake delta: ~2,300 B
Capacity03
Internet egress
1,000 Mbps
VPN concentrator capacity
500 Mbps
Existing peak utilisation
65%
Daily handshakes
10.0M
10,000,000 / day
New TLS connections across the organisation
Added daily volume
46
GB / day · bidirectional
Net new traffic created by the larger handshake
Peak hour overhead
36
Mbps · added during busiest hour
The number that matters for capacity planning
Internet egress
Perimeter firewall
Pre-PQC650 Mbps
Post-PQC686 Mbps
of capacity68.6%
Within comfortable headroom.
VPN concentrator
Remote workers · IKE + tunnel
Pre-PQC325 Mbps
Post-PQC336 Mbps
of capacity67.2%
Within comfortable headroom.
Remote user latency
Per-connection overhead
Added handshake bytes2,300 B
Est. added latency~80 ms
Connections / min at peak11.7
Modest user-visible impact.
Working day load profile
Internet egress · added handshake bandwidth across a typical day
06:0009:0012:0015:0018:0021:00
Existing baseline
Post-PQC total
Capacity
Assessment
Within manageable bounds.