S8HR vs LBO (voice)
For VoLTE roaming, GSMA defines two architectures. S8 Home Routing (S8HR) anchors media and IMS at the home network. Local Break-Out (LBO) terminates IMS in the visited network with home-routed control only.
| Attribute | S8HR | LBO (voice) |
|---|---|---|
| IMS anchor | HPLMN | VPLMN |
| Media path | Via HPLMN | Direct from VPLMN |
| Lawful intercept | Home | Visited |
| Complexity | Simpler for operator, higher latency | Complex IMS interworking |
| Adoption | Dominant | Limited to specific partnerships |
Verdict
S8HR won on operational simplicity. The trade is media latency and heavier HPLMN load — not security. LI jurisdiction is the real regulatory factor operators cite when they revisit the choice.