The SRT Protocol
draft-sharabayko-mops-srt-00

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MOPS                                                     M.P. Sharabayko
Internet-Draft                                           M.A. Sharabayko
Intended status: Standards Track           Haivision Network Video, GmbH
Expires: 10 September 2020                                       J. Dube
                                                               Haivision
                                                                 JS. Kim
                                                                 JW. Kim
                                                    SK Telecom Co., Ltd.
                                                            9 March 2020

                            The SRT Protocol
                      draft-sharabayko-mops-srt-00

Abstract

   This document specifies Secure Reliable Transport (SRT) protocol.
   SRT is a user-level protocol over User Datagram Protocol and provides
   reliability and security optimized for low latency live video
   streaming, as well as generic bulk data transfer.  For this, SRT
   introduces control packet extension, improved flow control, enhanced
   congestion control and a mechanism for data encryption.

Note to Readers

   Source for this draft and an issue tracker can be found at
   https://github.com/haivision/srt-rfc (https://github.com/haivision/
   srt-rfc).

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on 10 September 2020.

Sharabayko, et al.      Expires 10 September 2020               [Page 1]
Internet-Draft                     SRT                        March 2020

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   document authors.  All rights reserved.

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   Please review these documents carefully, as they describe your rights
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Motivation  . . . . . . . . . . . . . . . . . . . . . . .   3
     1.2.  Secure Reliable Transport Protocol  . . . . . . . . . . .   4
   2.  Conventions and Definitions . . . . . . . . . . . . . . . . .   5
   3.  Packet Structure  . . . . . . . . . . . . . . . . . . . . . .   5
     3.1.  Data Packets  . . . . . . . . . . . . . . . . . . . . . .   6
     3.2.  Control Packets . . . . . . . . . . . . . . . . . . . . .   8
       3.2.1.  Handshake . . . . . . . . . . . . . . . . . . . . . .   9
       3.2.2.  Keep-Alive  . . . . . . . . . . . . . . . . . . . . .  17
       3.2.3.  ACK (Acknowledgement) . . . . . . . . . . . . . . . .  18
       3.2.4.  NAK (Loss Report) . . . . . . . . . . . . . . . . . .  20
       3.2.5.  Shutdown  . . . . . . . . . . . . . . . . . . . . . .  21
       3.2.6.  ACKACK  . . . . . . . . . . . . . . . . . . . . . . .  22
   4.  SRT Data Transmission and Control . . . . . . . . . . . . . .  23
     4.1.  Stream Multiplexing . . . . . . . . . . . . . . . . . . .  23
     4.2.  Data Transmission Modes . . . . . . . . . . . . . . . . .  23
       4.2.1.  Message Mode  . . . . . . . . . . . . . . . . . . . .  23
       4.2.2.  Live Mode . . . . . . . . . . . . . . . . . . . . . .  24
       4.2.3.  Buffer Mode . . . . . . . . . . . . . . . . . . . . .  24
     4.3.  Handshake Messages  . . . . . . . . . . . . . . . . . . .  24
       4.3.1.  Caller-Listener Handshake . . . . . . . . . . . . . .  28
       4.3.2.  Rendezvous Handshake  . . . . . . . . . . . . . . . .  30
     4.4.  SRT Buffer Latency  . . . . . . . . . . . . . . . . . . .  36
     4.5.  Timestamp Based Packet Delivery . . . . . . . . . . . . .  37
       4.5.1.  Packet Delivery Time  . . . . . . . . . . . . . . . .  38
     4.6.  Too-Late Packet Drop  . . . . . . . . . . . . . . . . . .  40
     4.7.  Drift Management  . . . . . . . . . . . . . . . . . . . .  41
     4.8.  Acknowledgement and Lost Packet Handling  . . . . . . . .  42
       4.8.1.  Packet Acknowledgement (ACKs, ACKACKs)  . . . . . . .  43
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