Smart DNS for the New Network: Optimizing Content Delivery
This is the third in a series of blog posts that will discuss how smart DNS resolvers can enhance ongoing internet service provider (ISP) and mobile network operator (MNO) network transformation efforts, such as the transition to 5G, better integration of Wi-Fi, and new network designs that optimize the edge to improve service delivery and network efficiency.
There's lots of excitement about new services being designed to take advantage of new network technologies and architectures. Underneath the sizzle, content delivery will remain a foundational service in almost all networks. Sophisticated endpoints delivering richer video, immersive gaming encounters, and more sophisticated reality experiences will all depend on smart networks.
DNS has always played a central role in content distribution, and smart DNS resolution can make important contributions to enhance the user experience and improve network efficiency. DNS resolvers situated at the network edge can enable better traffic steering so users always get connected to the best source of gaming, video, and other content, and providers can manage delivery costs -- all without the costly packet inspection that typically increases latency. Details on how this works, and considerations for mobile networks, which have some unique constraints, will be discussed below.
DNS-based value-added services widely deployed by ISPs and MNOs to protect families and businesses and allow them to personalize their internet access also continue to evolve. These services can be enhanced to give parents (and business managers!) more control as online games and other content move to streaming using http. DNS queries act as a control point to manage access to content, and particular streams, such as games or videos, can be directed to smart proxies or caches where streams can be paused or stopped altogether.
EDNS Client Subnet and Equivalence Classes
The EDNS Client Subnet (ECS) defined in RFC 7871 optimizes where content is sourced and optimizes the cost of serving that content. The goal is to shape high-volume traffic to better align content sources with network architectures and cost structures. ECS incorporates the subnet of a client in recursive requests to authoritative servers. Given a client subnet, an authoritative server has better information about where a client is located, and it can make a more informed decision about what source of content a requestor should use.
The original ECS specification had limitations that could adversely impact resolvers -- cache size and load could grow exponentially and, in worst-case scenarios, overwhelm resolvers altogether. To address these problems, Akamai DNSi CacheServe resolvers have a capability called Equivalence Class, which aggregates groups of CIDR address blocks into a single "representative address" that indicates the group.
For example, all subscriber subnets behind an edge router are configured to use one representative address in ECS requests. CacheServe resolvers create a corresponding "view" of the cache that represents each arbitrary group of address blocks and answer queries from those clients accordingly.
Smart Content Delivery in Mobile Networks
Content delivery in mobile networks is complicated by the fact that all mobile IP traffic to and from the internet is handled by centralized gateways -- like the PDN Gateway in 4G/LTE or User Plane Function in 5G networks. New wireless architectures also now enable what is being called Local Break Out (LBO) of traffic much closer to the mobile edge as depicted in the figure below.
LBO of traffic at mobile edge sites opens the possibility of greatly improving the subscriber experience with content and other services hosted locally. Smart DNS resolution at the edge can provide better location awareness and enable a number of other useful capabilities.
This means that, unlike in wireline/fixed networks, mobile device IP addresses do not provide a reliable indication of their actual topological location within a network. As described in the section above, this problem can be minimized with the ECS DNS extensions that permit better mapping between content sources and requesters. Recursive DNS becomes another crystallized edge service, and placing smart resolvers at each LBO accurately conveys the proper ECS information to over-the-top CDNs and other collocated managed services such as a can.
As mentioned, Akamai CacheServe resolvers have a rich framework for ECS that allows different settings for various CDNs or other applications so device traffic can be optimized for each service. Akamai also has 20 years of worldwide leadership in operating a public CDN on its global edge platform, and recent private CDNs deeply deployed at carrier edge points demonstrate the technical experience and expertise necessary to arrive at a superior user experience and tighter management of content delivery costs.
Summary
A vast array of connected devices and subscriber expectations for more immersive experiences are causing a rethink of ISP and MNO service strategies. New network technology is enabling new network architectures with innovative edge services that meet the requirements of next-generation applications. Efforts to build smart edge services need to incorporate smart recursive DNS infrastructure. Akamai has been a DNS leader for many years, and CacheServe resolvers have a long history of innovation that will serve ISPs and MNOs well as they transform their networks for tomorrow's markets.
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