If an entity sends a message that establishes a call reference in a VPN context, that entity shall include a VPN indicator information element in this message.
NOTE – As a network option, the Network-specific facilities information element may be used instead of the VPN indicator information element (see Appendix I to Annex M).
If an entity receives a message that establishes a call reference, and this message does not contain a VPN indicator information element, then the procedures for signalling in a public network context for all messages that use this call reference shall apply.
If an entity receives a message that establishes a call reference, and this message contains a VPN indicator information element, then the procedures for signalling in a VPN context for all messages that use this call reference shall apply.