[Home](./index.md) > [sip.js](./sip.js.md) > [UserAgentOptions](./sip.js.useragentoptions.md) > [sipExtension100rel](./sip.js.useragentoptions.sipextension100rel.md) ## UserAgentOptions.sipExtension100rel property Reliable provisional responses. https://tools.ietf.org/html/rfc3262 Signature: ```typescript sipExtension100rel?: SIPExtension; ```