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DNS VNF Dynamic Scaling with Zero Touch Provisioning

October 22, 2020 | Written by: Surinder Paul | ,

Dns Nfv

Virtualization is reaching the network world with network function, scaling, Network as a Service and Zero Touch Provisioning (ZTP). As we discussed in our previous blog on 5G and NFV, the DNS service is a really good candidate for automatic instantiation and scaling, helping to optimize costs and improve UX . DNS architecture intrinsically proposes such evolution and there is room for hybrid DNS topologies which combine hardware and software. Dedicated hardware DNS covers the need for high performances as we propose with our DNS Blast. DNS VNF (Virtual Network Function) covers the edge design and rapid scaling situations in the 5G space and obviously in any corporation with a large number of clients and DNS requests to handle.

VNF needs specific metrics

In any elastic application environment where resources are started and stopped in order to maintain a good service quality, scaling needs to be triggered by intrinsic metrics, not only on used CPU or network bandwidth as those do not provide an accurate state of the service. In the case of the DNS recursive service, it is interesting to use the number of QPS (queries per second), the average response delay or the cache hit ratio, in order to allow scaling up or down with efficiency. This is typically what we propose when DNS is running in a NFV environment, because VNF can host a DNS recursive service, even a secondary one with DNS firewall for edge filtering.

DNS SmartArchitecture for ZTP

In the following demonstration video, we present how the SOLIDserver and its unique SmartArchitecture product eases Zero Touch Provisioning of DNS VNF. We also demonstrate how a DNS VNF manager can leverage internal metrics like the sliding average of QPS in order to perform the scaling up and down through the hypervisor layer. The SmartArchitecture used for managing the DNS service allows applying predefined topology templates validated by the industry and automatically add or remove nodes at any position in the design with respect to the topology.

For example, in a DNS stealth security topology that should be used to host exposed public authoritative zones, when adding a DNS server it is simply required to specify its role: hidden primary, primary or secondary and all the tricky configuration parts are performed automatically by the SmartArchitecture solution. It also sets all the parameters of the DNS server such as forwarding and caching, recursion, RPZ filtering, or rate limiting. Therefore, you are sure that all the servers, with respect to their position in the SmartArchitecture, are always configured and working the same exact way and that any modification performed at the SmartArchitecture level will be automatically synchronized to all the members.

Zero Touch Provisioning requires a SmartArchitecture type of solution. It would not be reasonable to maintain a repository of all the configuration templates to be applied whenever a DNS VNF is started, it just doesn’t scale and requires too much preparation and knowledge.

The setup

In the video, we assemble all these concepts into a very realistic demonstration on how to scale the DNS recursive service based on the QPS received at the service level. The main components used in this demonstration are:

  • A SOLIDserver for SmartArchitecture management, API endpoint, statistics, security, DNS management for the infrastructure components zone
  • A DNS VNF ready to run in our hypervisor
  • A VNF manager able to gather metrics (here the QPS of each DNS VNF) and take all scaling decisions (up or down)
  • A load balancer able to distribute the traffic between the available DNS VNF, we could have used also Anycast distribution, but for our demonstration, a load-balancer is enough with regards to expected performances
  • An observability platform to monitor how our DNS recursive service is running, the number of VNF deployed and the QPS in near real time
  • A DNS traffic injector that can be configured to send more or less requests by dynamically modifying the inter frame delay. It simulates real ISP traffic with regards to top domains, errors and cache hit ratio volumes

The demo

In the video, we show that the DNS service automatically adjusts the number of servers started. We have tuned the triggers limit in order for the demo to be reactive, each implementation will adapt these with regards to the service level that needs to be achieved and the abilities of the whole infrastructure, especially the hypervision service that may present different performances than on our demo setup.

For the purpose of the demo, we adjust the traffic injector parameters to send DNS requests through the load-balancer to the DNS service and we set 2 arbitrary limits at the VNFm that are expressed in QPS for automatic scaling:

  • >= 1500 QPS: add a VNF in the SmartArchitecture if the average number of queries per second on the DNS service is higher than 1500 QPS,
  • <= 500 QPS: delete a VNF from the SmartArchitecture when the traffic falls below 500 queries per second on the DNS service; we leave at minimum one VNF

DNS SmartArchitecture is designed for VNF

We can conclude that effectively DNS is an excellent candidate for VNF and especially in a 5G model where resources should vary throughout the day; being adjusted to the number of clients in specific areas and the stress they put on the network, in order to bring cost savings and enhance customer experience. Zero Touch Provisioning is key for dynamic scaling. A solution that enables fully automated addition and removal of a DNS server in a pre-designed topology and doesn’t require a complex external configuration process is absolutely mandatory as it will limit the number of errors and incidents. For telcos to advance on their journey towards autonomous networks, this is vital. VNFm using real service metrics for taking scaling decisions rather than CPU, network or memory usage is obvious. The value proposition of the SmartArchitecture solution covers most of the requirements asked by telcos and corporates deploying NFV like solutions, so it deserves to be tried out.

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