A Survey of Worldwide Censorship Techniques
draft-irtf-pearg-censorship-04
pearg J. Hall
Internet-Draft Internet Society
Intended status: Informational M. Aaron
Expires: January 14, 2021 CU Boulder
S. Adams
CDT
A. Andersdotter
B. Jones
Princeton
N. Feamster
U Chicago
July 13, 2020
A Survey of Worldwide Censorship Techniques
draft-irtf-pearg-censorship-04
Abstract
This document describes technical mechanisms censorship regimes
around the world use for blocking or impairing Internet traffic. It
aims to make designers, implementers, and users of Internet protocols
aware of the properties exploited and mechanisms used for censoring
end-user access to information. This document makes no suggestions
on individual protocol considerations, and is purely informational,
intended as a reference.
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
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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 January 14, 2021.
Hall, et al. Expires January 14, 2021 [Page 1]
Internet-Draft draft-irtf-pearg-censorship July 2020
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Technical Prescription . . . . . . . . . . . . . . . . . . . 3
4. Technical Identification . . . . . . . . . . . . . . . . . . 4
4.1. Points of Control . . . . . . . . . . . . . . . . . . . . 4
4.2. Application Layer . . . . . . . . . . . . . . . . . . . . 6
4.2.1. HTTP Request Header Identification . . . . . . . . . 6
4.2.2. HTTP Response Header Identification . . . . . . . . . 7
4.2.3. Instrumenting Content Distributors . . . . . . . . . 8
4.2.4. Deep Packet Inspection (DPI) Identification . . . . . 9
4.3. Transport Layer . . . . . . . . . . . . . . . . . . . . . 12
4.3.1. Shallow Packet Inspection and Transport Header
Identification . . . . . . . . . . . . . . . . . . . 12
4.3.2. Protocol Identification . . . . . . . . . . . . . . . 13
5. Technical Interference . . . . . . . . . . . . . . . . . . . 14
5.1. Application Layer . . . . . . . . . . . . . . . . . . . . 14
5.1.1. DNS Interference . . . . . . . . . . . . . . . . . . 14
5.2. Transport Layer . . . . . . . . . . . . . . . . . . . . . 17
5.2.1. Performance Degradation . . . . . . . . . . . . . . . 17
5.2.2. Packet Dropping . . . . . . . . . . . . . . . . . . . 17
5.2.3. RST Packet Injection . . . . . . . . . . . . . . . . 18
5.3. Multi-layer and Non-layer . . . . . . . . . . . . . . . . 19
5.3.1. Distributed Denial of Service (DDoS) . . . . . . . . 19
5.3.2. Network Disconnection or Adversarial Route
Announcement . . . . . . . . . . . . . . . . . . . . 20
6. Non-Technical Interference . . . . . . . . . . . . . . . . . 21
6.1. Manual Filtering . . . . . . . . . . . . . . . . . . . . 21
6.2. Self-Censorship . . . . . . . . . . . . . . . . . . . . . 21
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