[Home](./index.md) > [sip.js](./sip.js.md) > [Dialog](./sip.js.dialog.md) > [sequenceGuard](./sip.js.dialog.sequenceguard.md) ## Dialog.sequenceGuard() method If the remote sequence number was not empty, but the sequence number of the request is lower than the remote sequence number, the request is out of order and MUST be rejected with a 500 (Server Internal Error) response. https://tools.ietf.org/html/rfc3261\#section-12.2.2 Signature: ```typescript protected sequenceGuard(message: IncomingRequestMessage): boolean; ``` ## Parameters | Parameter | Type | Description | | --- | --- | --- | | message | IncomingRequestMessage | | Returns: `boolean` True if the program execution is to continue in the branch in question. Otherwise a 500 Server Internal Error was stateless sent and request processing must stop.