What is the s11 interface?
Earlier we have discussed some interfaces (e.g s6a ) in EPC. Here we will discuss the s11 interface. S11 interface is between MME and the SGW. Both MME and SGW are in the roaming network. The protocol over the s11 interface is GTP. GTP is a tunnelling protocol that is used to set up a data tunnel for the internet to a mobile subscriber.
GTP runs over UDP. So the s11 interface used UDP as the network protocol. The interface uses signalling to setup PDP sessions for the internet. SGW, in turn, does signalling towards the PGW on another interface.
When a mobile phone attaches it does signalling with HSS over the S6a interface and then on the s11 interface. The following are the messages name exchanges on the s11 interface.
- Create Session request/response.
- Delete Session request/response.
- Modify-Bearer request/response.