# What is an MSC (Mobile Switching Centre)?

> The MSC (Mobile Switching Centre) is the core 2G/3G network node that switches voice calls and relays SMS for the handsets currently in its coverage area. For a mobile-terminated SMS, the sending SMSC uses SS7 MAP MT-ForwardSM to hand the message to the recipient's serving MSC, which pages the handset and delivers it. Each MSC is paired with a VLR that caches subscriber data for the devices it serves.

- Canonical URL: https://www.broadnet.me/answers/what-is-msc
- Language: en
- Last reviewed: 2026-07-22
- Publisher: BroadNet (https://www.broadnet.me)

## The MSC in the SMS-MT flow

Delivery is a two-step SS7 exchange: the SMSC sends SendRoutingInfoForSM to the HLR to find the serving MSC, then MT-ForwardSM to that MSC, which pages the handset, delivers the SM, and returns the outcome that becomes your DLR. See /answers/ss7-map-explained and /answers/what-is-dlr.

## The MSC on 4G and 5G

In an all-IP 4G/5G network the MSC's role is taken by the MME (4G) and the AMF (5G). SMS is then delivered either via SGs fallback through a legacy MSC, or over IMS (SMS-over-IP). This is why SS7 and the MSC persist for SMS even as voice and data move fully packet-switched. See /answers/diameter-s6a-explained.

## Related

- [All answers](https://www.broadnet.me/answers)
- [Glossary](https://www.broadnet.me/answers)
- [What is a VLR (Visitor Location Register)?](https://www.broadnet.me/answers/what-is-vlr)
- [What is an HLR (Home Location Register)?](https://www.broadnet.me/answers/what-is-hlr)
- [SS7 MAP — what it is and why messaging still depends on it](https://www.broadnet.me/answers/ss7-map-explained)
- [Diameter S6a — the 4G equivalent of MAP](https://www.broadnet.me/answers/diameter-s6a-explained)
- [Signaling & CDR Intelligence](https://www.broadnet.me/platforms/signaling-cdr)
- [SS7 Firewall](https://www.broadnet.me/operators/ss7-firewall)