The SRT Protocol
draft-sharabayko-srt-00
Network Working Group M.P. Sharabayko
Internet-Draft M.A. Sharabayko
Intended status: Informational Haivision Network Video, GmbH
Expires: 9 September 2021 J. Dube
Haivision Systems, Inc.
JS. Kim
JW. Kim
SK Telecom Co., Ltd.
8 March 2021
The SRT Protocol
draft-sharabayko-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.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 9 September 2021.
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license-info) in effect on the date of publication of this document.
Sharabayko, et al. Expires 9 September 2021 [Page 1]
Internet-Draft SRT March 2021
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . 4
1.2. Secure Reliable Transport Protocol . . . . . . . . . . . 5
2. Terms and Definitions . . . . . . . . . . . . . . . . . . . . 6
3. Packet Structure . . . . . . . . . . . . . . . . . . . . . . 6
3.1. Data Packets . . . . . . . . . . . . . . . . . . . . . . 7
3.2. Control Packets . . . . . . . . . . . . . . . . . . . . . 9
3.2.1. Handshake . . . . . . . . . . . . . . . . . . . . . . 10
3.2.2. Key Material . . . . . . . . . . . . . . . . . . . . 18
3.2.3. Keep-Alive . . . . . . . . . . . . . . . . . . . . . 22
3.2.4. ACK (Acknowledgment) . . . . . . . . . . . . . . . . 23
3.2.5. NAK (Loss Report) . . . . . . . . . . . . . . . . . . 25
3.2.6. Congestion Warning . . . . . . . . . . . . . . . . . 26
3.2.7. Shutdown . . . . . . . . . . . . . . . . . . . . . . 27
3.2.8. ACKACK . . . . . . . . . . . . . . . . . . . . . . . 27
3.2.9. Message Drop Request . . . . . . . . . . . . . . . . 28
3.2.10. Peer Error . . . . . . . . . . . . . . . . . . . . . 29
4. SRT Data Transmission and Control . . . . . . . . . . . . . . 30
4.1. Stream Multiplexing . . . . . . . . . . . . . . . . . . . 30
4.2. Data Transmission Modes . . . . . . . . . . . . . . . . . 31
4.2.1. Message Mode . . . . . . . . . . . . . . . . . . . . 31
4.2.2. Buffer Mode . . . . . . . . . . . . . . . . . . . . . 32
4.3. Handshake Messages . . . . . . . . . . . . . . . . . . . 32
4.3.1. Caller-Listener Handshake . . . . . . . . . . . . . . 35
4.3.2. Rendezvous Handshake . . . . . . . . . . . . . . . . 37
4.4. SRT Buffer Latency . . . . . . . . . . . . . . . . . . . 43
4.5. Timestamp-Based Packet Delivery . . . . . . . . . . . . . 44
4.5.1. Packet Delivery Time . . . . . . . . . . . . . . . . 45
4.6. Too-Late Packet Drop . . . . . . . . . . . . . . . . . . 47
4.7. Drift Management . . . . . . . . . . . . . . . . . . . . 48
4.8. Acknowledgement and Lost Packet Handling . . . . . . . . 50
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