Figure 9.5 Layers in SS7 MTP:Message transfer part SCCP:Signaling connection control point TUP TCAP:Transaction capabilities application port Upper layers TCAP ISUP TUP:Telephone user port ISUP:ISDN user port SCCP Network layer MTP level 3 Data link layer MTP level 2 Physical layer MTP level 1 9.99.9 Figure 9.5 Layers in SS7