We now employ DNS in an Anycast configuration. This means we have multiple instances of our DNS servers distributed across our network. We use a custom BGP configuration to ensure that our DNS services are available in multiple locations at the same IP address. We announce the BGP routes from those locations and the BGP path selection algorithms do the rest. Please get in touch for more information – we’re happy to share what we’ve learned in this production deployment with anyone interested.Posted on 19 November 2013 - Tech AnyCast DNS
A key design goal was to ensure that DNS is served from the closest location to the querying client, maintaining high performance, and that in the event of single or multiple DNS node failures there are sufficient alternative servers available to perform the role of the injured DNS.
A secondary goal was in-flight maintenance. Though work on core DNS is infrequent, multiple deployment means we can perform in-service maintenance on our DNS systems with minimal customer impact.
We utilise a database driven PowerDNS infrastructure. DNS changes made through our customer portal are replicated across the DNS estate in near-real time through a custom built engine and without a single centralized database dependency. This further decouples our DNS infrastructure from a single location improving its availability characteristics.
Currently all our DNS nodes are located inside our BGP Autonomous System, our backbone network stretching across the UK & Ireland. This gives us the degree of resilience we feel we need at this point.
We’re observing stability and have been satisfied with the results. Depending on further positive assessment, we’ll be seeking to roll out Any cast DNS to additional locations - both internal and external to our backbone network.
As ever we’re happy to share what we’ve learned with the community. Please feel free get in touch.