[Home](./index.md) > [sip.js](./sip.js.md) > [ClientTransactionUser](./sip.js.clienttransactionuser.md) > [onRequestTimeout](./sip.js.clienttransactionuser.onrequesttimeout.md) ## ClientTransactionUser.onRequestTimeout property Callback for request timeout error. When a timeout error is received from the transaction layer, it MUST be treated as if a 408 (Request Timeout) status code has been received. https://tools.ietf.org/html/rfc3261\#section-8.1.3.1 TU MUST be informed of a timeout. https://tools.ietf.org/html/rfc3261\#section-17.1.2.2 Signature: ```typescript onRequestTimeout?: () => void; ```