Signalling protocols for end-to-end connection

ISUP

Q.931

Q.921

I.430

Q.931

Q.921

I.430

MTP 3

MTP 2

MTP 1

Q.931

Q.921

I.430

Q.931

Q.921

I.430

ISUP

MTP 3

MTP 2

MTP 1

contains the signalling messages for call control

User interface

User interface

PSTN Network

DSS1

SS7

DSS1