[Home](./index.md) > [sip.js](./sip.js.md) > [Session](./sip.js.session.md) > [sessionDescriptionHandler](./sip.js.session.sessiondescriptionhandler.md) ## Session.sessionDescriptionHandler property Session description handler. Signature: ```typescript readonly sessionDescriptionHandler: SessionDescriptionHandler | undefined; ``` ## Remarks If `this` is an instance of `Invitation`, `sessionDescriptionHandler` will be defined when the session state changes to "established". If `this` is an instance of `Inviter` and an offer was sent in the INVITE, `sessionDescriptionHandler` will be defined when the session state changes to "establishing". If `this` is an instance of `Inviter` and an offer was not sent in the INVITE, `sessionDescriptionHandler` will be defined when the session state changes to "established". Otherwise `undefined`.