Text over IP / Real-Time Text Information Site

Text over IP (ToIP), also known as Real-Time Text (RTT), is a means of sending text over IP networks within the context of a multimedia session. This page provides links to related specifications and a error rate calculator to help those engineering the network better understand character loss.

Real-Time Text (RTT) Specifications


  • RFC 4102 - Registration of the text/red MIME Sub-Type
  • RFC 4103 - RTP Payload for Text Conversation
  • RFC 4351 - Real-Time Transport Protocol (RTP) Payload for Text Conversation Interleaved in an Audio Stream
  • RFC 5194 - Framework for Real-Time Text over IP Using the Session Initiation Protocol (SIP)
  • RFC 9071 - RTP-Mixer Formatting of Multiparty Real-Time Text


Real-Time Text (RTT) Related Links