TCP Usage Guidance in the Internet of Things (IoT)
draft-ietf-lwig-tcp-constrained-node-networks-03
LWIG Working Group C. Gomez
Internet-Draft UPC
Intended status: Informational J. Crowcroft
Expires: December 12, 2018 University of Cambridge
M. Scharf
Nokia
June 10, 2018
TCP Usage Guidance in the Internet of Things (IoT)
draft-ietf-lwig-tcp-constrained-node-networks-03
Abstract
This document provides guidance on how to implement and use the
Transmission Control Protocol (TCP) in Constrained-Node Networks
(CNNs), which are a characterstic of the Internet of Things (IoT).
Such environments require a lightweight TCP implementation and may
not make use of optional functionality. This document explains a
number of known and deployed techniques to simplify a TCP stack as
well as corresponding tradeoffs. The objective is to help embedded
developers with decisions on which TCP features to use.
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 December 12, 2018.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions used in this document . . . . . . . . . . . . . . 4
3. Characteristics of CNNs relevant for TCP . . . . . . . . . . 4
3.1. Network and link properties . . . . . . . . . . . . . . . 4
3.2. Usage scenarios . . . . . . . . . . . . . . . . . . . . . 5
3.3. Communication and traffic patterns . . . . . . . . . . . 6
4. TCP implementation and configuration in CNNs . . . . . . . . 6
4.1. Path properties . . . . . . . . . . . . . . . . . . . . . 7
4.1.1. Maximum Segment Size (MSS) . . . . . . . . . . . . . 7
4.1.2. Explicit Congestion Notification (ECN) . . . . . . . 7
4.1.3. Explicit loss notifications . . . . . . . . . . . . . 8
4.2. TCP guidance for small windows and buffers . . . . . . . 8
4.2.1. Single-MSS stacks - benefits and issues . . . . . . . 8
4.2.2. TCP options for single-MSS stacks . . . . . . . . . . 9
4.2.3. Delayed Acknowledgments for single-MSS stacks . . . . 9
4.2.4. RTO estimation for single-MSS stacks . . . . . . . . 10
4.3. General recommendations for TCP in CNNs . . . . . . . . . 10
4.3.1. Error recovery and congestion/flow control . . . . . 10
4.3.2. Selective Acknowledgments (SACK) . . . . . . . . . . 11
4.3.3. Delayed Acknowledgments . . . . . . . . . . . . . . . 11
5. TCP usage recommendations in CNNs . . . . . . . . . . . . . . 11
5.1. TCP connection initiation . . . . . . . . . . . . . . . . 12
5.2. TCP connection lifetime . . . . . . . . . . . . . . . . . 12
5.2.1. Long TCP connection lifetime . . . . . . . . . . . . 12
5.2.2. Short TCP connection lifetime . . . . . . . . . . . . 12
5.3. Number of parallel connections . . . . . . . . . . . . . 13
6. Security Considerations . . . . . . . . . . . . . . . . . . . 13
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14
8. Annex. TCP implementations for constrained devices . . . . . 14
8.1. uIP . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
8.2. lwIP . . . . . . . . . . . . . . . . . . . . . . . . . . 15
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