Other ISDN messages

Other ISDN messages may occur. For more information:

On ISDN Layer 2 frames see

ITU-T Q.921

On ISDN Layer 3 messages or Information elements see

• ITU-T Q.931 standards
• ETSI (European Telecom Standards Institute) ETS 300 102-1 User-network interface Layer 3
• The relevant 5ESS or Northern Telecom ISDN Primary Rate Interface Specifications.