9. Extensions

Extension Type Field Usage

When implementing extensions, it's important to understand how the extension_type field in the message frame header should be set:

• The extension_type field identifies the extension that introduced and defined the non-TLV fields of a message.
• For messages defined in the core specification, extension_type MUST be 0x0000.
• For new messages introduced by an extension, extension_type MUST be set to that extension's identifier.
• When an extension modifies an existing message using TLV fields, the extension_type in the frame header does not change - it remains set to the extension that originally defined the message structure (or 0x0000 for core messages).

For a detailed explanation with examples, see Section 3.4.1 Extension Type Field Usage in the Protocol Overview.

Extension Registry