Networking Notes - April 2021

Welcome to the April 2021 edition of the Networking Notes newsletter.

This newsletter gathers the most recent news about the evolution of the networking field. Its main objective is to inform the students who have read the Computer Networking: Principles, Protocols and Practice ebook about the evolution of the field.

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The CNP3 ebook

The third edition of the Computer Networking: Principles, Protocols and Practice ebook continues to be improved by Quentin De Coninck who updates the chapters every week. We’ll have a revised text by the end of May and probably other interesting news about the ebook later.

Generic networking

On March 10, 2021, a fire broke at an OVH datacenter in Strasbourg. This caused a series of failures on websites and other services that are hosted in this and nearby datacenters. Rebuilding a destroyed datacenter is not an easy job, but a good exercise in disaster recovering. While many companies tend to hide the bad news that affect their operations, OVH is very open and provides regular updates on the evolution of their recovery and the problems they face. A must read if you manage network infrastructure and need to plan for the worst case…

Failures usually reveal interesting information about deployed networks because they highlight some design or configuration choices. A recent presentation discusses a failure that affected the T-Mobile network in 2020.

While most countries are trying to deploy fiber, AT&T officials argues that fiber is not required in the US. For AT&T, a broadband service of 25 Mbps download and 3 Mbps upload is largely sufficient. Maybe AT&T could suggest to reinstall dialup modems or ISDN…

Smartphones regularly phone home and send data to Google (for Android ones) or Apple (for iPhones). A recent study explores the data that these smartphones exchange and provide the details that allow you to reproduce it with your own smartphones.

Some governments decide to block Internet access during national exams, riots or elections. In these countries, network operators regularly stop announcing BGP routes for political reasons. CAIDA collects these disruptions and allows you to track them from the IODA website.

The Networking Channel organises a series of webinars on emerging networking topics. These webinars could be really interesting for networking students.

Network protocols

Application layer


While the large cloud providers promote the usage of DoH instead of using regular DNS, a recent statement reaffirms the importance of DNSSEC. DoH alone does not provide the same guarantees as DNSSEC.


Given the sanitary situation, many Internet users rely on web conferencing. Many of the popular web conferencing applications leverage webrtc, a set of protocols developed within the IETF. A recent article describes the evolution of these protocols.


For the Chrome team, HTTP should not be used without TLS. Starting in version 90, Chrome will use https by default when the user does not specify a protocol in the URL.

Some companies add some humour on the web page that they serve to indicate an error. Electricians will probably like Texas Instruments’ 404 error page


The IETF has recently deprecated TLS 1.0 and 1.1 with the publication of RFC8996. At the same time, Jan Kopriva published a short note showing that these versions of TLS are still enabled on more than 50% of the public web servers.

If you need to correctly configure TLS on a web site, check EFF’s certbot for the correct configuration for the software that you use.

Transport layer

Networking layer

Tony Li summarises in an APNIC Blog post the evolution of the architecture of Internet routers. An interesting read if you wan to understand how routers operate.

IPv4 and IPv6

A recent bug in a library that parses IP addresses reminds us on the difficulty of correctly parsing IP addresses. Do you see a difference between 0127.0.0.1 and ? Well, given that IP is mainly implemented in C language, you need to look at how C libraries parse a number that begins with zero. By default, this number is considered to be in octal and thus 0127.0.0.1 is equivalent to… If you need to parse IP addresses yourself, be sure to read the RFCs in detail on rely on existing libraries.

Interdomain routing (BGP)

Despite its importance in the Internet, BGP remains a complex protocol. Researchers have difficulties in completely explaining the reasons for some of the BGP messages that they observe. In a recent paper, Long-lasting Sequences of BGP Updates, L. Ariemma, S. Liotta, M. Candela, and G. Di Battista analyse the long sequences of BGP messages that were collected over the Internet. They also developed a website, which allows to explore these collected BGP messages.


Several companies launch satellites to provide Internet access services using low-earth orbit satellites. This brings lower delays compared to geostationary satellites. Starlink is one example of these services. Samknows analyses the performance of this new service with different performance metrics. As the service is still in beta, we’ll see whether this performance will still be achieved when many users are active.

Software and tools

curl is a popular command-line tool to interact with different types of servers. Daniel Stenberg, curl’s main author discusses his work in an interview on nixCraft.

When exploring a new protocol, it is always interesting to look at packet traces to see how it is used in practice, but collecting these traces can be difficult. Nick Russo provides dozen of packet traces covering many networking technologies, from layer 2 to routing protocols, network management and common enterprise applications.

Written on April 1, 2021