29 September 2020

Today’s blog post discusses DNS Flag Day, an annual day that this year falls on Thursday 1 October 2020. We look into the significance of DNS Flag Day and what it represents for the wider community and provide insight from our very own Domain Name System (DNS) expert, Howard Eland, Senior Director of DNS Infrastructure at Afilias.

Understanding the DNS

To understand what this day is all about, you will also need to have a clear understanding of the DNS. Luckily, Howard took the time in September 2019 to explain how the DNS works in .au, which we captured in this blog post. The post looks at DNS delegation in .au and its complexities as a hierarchical system by which computer addresses are translated from numerical strings called IP addresses (eg 172.16.21.3) into a form that is easily understood by humans, domain names (eg afilias.com.au).

What is DNS Flag Day?

As detailed on the DNS Flag Day website, this day is an annual effort for DNS professionals around the globe to concentrate on addressing particular issues that affect the performance of the DNS and its ability to ensure messages get to the correct addresses in the most efficient manner. The “DNS Flag Day” effort is community driven by DNS software and service providers, and supported by the DNS Operations, Analysis and Research Centre (DNS-OARC).

This year, the focus will be on IP fragmentation of DNS packets, which applies to changes that are made within a packet that carries data containing part of the message body, also known as an “IP Datagram”. Messages on the internet are — by design — broken broken up into smaller “packets” that are re-assembled on the receiving end. When these packets are large, they are occasionally fragmented along the way by typical network links, potentially causing loss of data or even security issues. For a closer look at IP fragmentation and how it impacts the fragility of internet communication refer to this article from the Internet Engineering Task Force.

Why is DNS Flag Day significant?

DNS Flag Day is a significant day for the backend developers and DNS operators who do a lot of the behind the scenes work that everyday internet users barely give a second thought, due to its complexity.

When asked his thoughts on DNS Flag Day 2020 Howard explained, “This year’s DNS Flag Day is focusing on ‘keeping things whole’ – in other words, reducing the likelihood that DNS packets will ‘fragment’, which can cause problems for DNS queries. To help with this, the DNS community has settled on a default minimum ‘safe’ size.” 

He continued: “Note this isn’t a ‘Flag Day’ in the truest sense of the phrase – things will not work one way on 30 September, and another on 1 October. Instead, this is the day when DNS software providers will make sure they have adhered to the new size, and operators should start upgrading software if needed.”

As internet users, it is interesting to learn about any changes to the DNS, big or small, such as those proposed each year on DNS Flag Day. It is reassuring to know that a dedicated group of DNS pros around the world are constantly working to keep the internet operating.

For .au domains, Afilias’ systems have long been configured to meet the new packet size guidelines, minimising the potential for fragmentation.

Have a question, comment or idea for a future blog post? Email us at blog@afilias.com.au

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