TCP Usage Guidance in the Internet of Things (IoT)
draft-ietf-lwig-tcp-constrained-node-networks-03
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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
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 December 12, 2018.
Copyright Notice
Copyright (c) 2018 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
Gomez, et al. Expires December 12, 2018 [Page 1]
Internet-Draft TCP in IoT June 2018
publication of this document. 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
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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