The SRT Protocol
draft-sharabayko-mops-srt-01

Document Type Active Internet-Draft (individual)
Authors Maria Sharabayko  , Maxim Sharabayko  , Jean Dube  , Joonwoong Kim  , Jeongseok Kim 
Last updated 2020-09-09
Stream (None)
Intended RFC status (None)
Formats plain text pdf htmlized (tools) htmlized bibtex
Stream Stream state (No stream defined)
Consensus Boilerplate Unknown
RFC Editor Note (None)
IESG IESG state I-D Exists
Telechat date
Responsible AD (None)
Send notices to (None)
MOPS                                                     M.P. Sharabayko
Internet-Draft                                           M.A. Sharabayko
Intended status: Standards Track           Haivision Network Video, GmbH
Expires: 13 March 2021                                           J. Dube
                                                               Haivision
                                                                 JS. Kim
                                                                 JW. Kim
                                                    SK Telecom Co., Ltd.
                                                        9 September 2020

                            The SRT Protocol
                      draft-sharabayko-mops-srt-01

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.

Status of This Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 13 March 2021.

Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.

Sharabayko, et al.        Expires 13 March 2021                 [Page 1]
Internet-Draft                     SRT                    September 2020

   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components
   extracted from this document must include Simplified BSD License text
   as described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Motivation  . . . . . . . . . . . . . . . . . . . . . . .   3
     1.2.  Secure Reliable Transport Protocol  . . . . . . . . . . .   4
   2.  Terms and Definitions . . . . . . . . . . . . . . . . . . . .   5
   3.  Packet Structure  . . . . . . . . . . . . . . . . . . . . . .   6
     3.1.  Data Packets  . . . . . . . . . . . . . . . . . . . . . .   7
     3.2.  Control Packets . . . . . . . . . . . . . . . . . . . . .   8
       3.2.1.  Handshake . . . . . . . . . . . . . . . . . . . . . .   9
       3.2.2.  Key Material  . . . . . . . . . . . . . . . . . . . .  17
       3.2.3.  Keep-Alive  . . . . . . . . . . . . . . . . . . . . .  21
       3.2.4.  ACK (Acknowledgment)  . . . . . . . . . . . . . . . .  22
       3.2.5.  NAK (Loss Report) . . . . . . . . . . . . . . . . . .  24
       3.2.6.  Shutdown  . . . . . . . . . . . . . . . . . . . . . .  25
       3.2.7.  ACKACK  . . . . . . . . . . . . . . . . . . . . . . .  26
   4.  SRT Data Transmission and Control . . . . . . . . . . . . . .  26
     4.1.  Stream Multiplexing . . . . . . . . . . . . . . . . . . .  27
     4.2.  Data Transmission Modes . . . . . . . . . . . . . . . . .  27
       4.2.1.  Message Mode  . . . . . . . . . . . . . . . . . . . .  27
       4.2.2.  Live Mode . . . . . . . . . . . . . . . . . . . . . .  28
       4.2.3.  Buffer Mode . . . . . . . . . . . . . . . . . . . . .  28
     4.3.  Handshake Messages  . . . . . . . . . . . . . . . . . . .  28
       4.3.1.  Caller-Listener Handshake . . . . . . . . . . . . . .  31
       4.3.2.  Rendezvous Handshake  . . . . . . . . . . . . . . . .  33
     4.4.  SRT Buffer Latency  . . . . . . . . . . . . . . . . . . .  39
     4.5.  Timestamp-Based Packet Delivery . . . . . . . . . . . . .  40
       4.5.1.  Packet Delivery Time  . . . . . . . . . . . . . . . .  42
     4.6.  Too-Late Packet Drop  . . . . . . . . . . . . . . . . . .  43
     4.7.  Drift Management  . . . . . . . . . . . . . . . . . . . .  44
     4.8.  Acknowledgement and Lost Packet Handling  . . . . . . . .  46
       4.8.1.  Packet Acknowledgement (ACKs, ACKACKs)  . . . . . . .  46
       4.8.2.  Packet Retransmission (NAKs)  . . . . . . . . . . . .  47
Show full document text