[Home](./index.md) > [sip.js](./sip.js.md) > [SessionDelegate](./sip.js.sessiondelegate.md) > [onAckTimeout](./sip.js.sessiondelegate.onacktimeout.md) ## SessionDelegate.onAckTimeout() method Timeout waiting for ACK request. If no handler is provided the Session will terminated with a BYE. https://tools.ietf.org/html/rfc3261\#section-13.3.1.4 Signature: ```typescript onAckTimeout?(): void; ``` Returns: `void`