Intent-based-networking (IBN) is the shiny new object in networking. Analysts and vendors alike are touting it as transformative to the data center and Cisco’s CEO said “Intent-Based Networking will redefine networking for the next 30 years”. Apstra pioneered Intent-Based Networking and delivered the first and only complete system which enables Cisco, Juniper, Arista, HP and white box customers to deploy an IBN system through the Apstra Operating System (AOS™). We are experiencing a phenomenon called “intent washing,” which Gartner predicted would happen. Vendors are rebranding existing products as “intent-based”. Some are even rebranding complete product lines. It’s confusing to discern marketing and reality — the ads, white papers and slides — vs shipping products that deliver on the value proposition of Intent-Based Networking.
In this article, I’d like to cut through this confusion by listing and defining the foundational aspects of an IBN system. I encourage you to spend the time to internalize them, and use them as criteria when considering or evaluating new products.
The main motivation behind IBN is to allow companies to run their networks reliably and cost-effectively while offering more agility and control, both in terms of new features and vendor choices. To achieve that, the hard problem is how to compose the complex infrastructure capabilities in order to serve business needs in the presence of constant change in device capabilities and business rules?
The composition problem is a consequence of the fact that today’s data centers act as scale-out computers and there is a need to compose this infrastructure consisting of compute, network, and storage. But this is only one dimension of this composition problem. Another one is how do you incorporate complex business rules and policies? Infrastructure capabilities, as well as mechanisms to consume them, are subject to constant change. And the situation with business rules is even worse, both in terms of the frequency and the complexity of the changes. Every time a change happens, you are required to perform some composition. If you take something out, is what is left still acting as a coherent whole? If you add or modify something, is the new composite valid? With a single compute virtualization node, the problem the operating system has to deal with involves partitioning of resources as well as dealing with isolation. But with the data center acting as a scale-out computer, the distributed operating system first has to perform composition and only then again resource partitioning and isolation. But if you fail at composition due to changes in infrastructure and business rules, you will never even get to consuming your precious and expensive scale-out compute resources.
When we first spoke about our vision of Intent-Based Networking, one aspect about IBN mentioned by analysts was orchestration, but there is much more than that. Orchestration is an execution workflow and is less concerned with the state. So in that model, it is assumed that someone else creates the single source of truth about the state of infrastructure and business policies; and that this state is then fed into the orchestration workflow. In IBN, that single source of truth, originating from intent, (which we define more precisely below) is at the core of the platform, and drives everything else.
Definition So what is the intent? At the highest level, intent is a declarative specification of the desired outcome. And the desired outcome is complete automation of the whole network service lifecycle, which consists of the following phases:
design, build, deploy, validate. See
our videos from Networking Field Day 16 for more details about what these phases entail.
At a high level, Intent defines the “what” not the “how”. A key observation is that intent is dynamic, and a fundamental requirement of an IBN system is that it should be capable of ensuring that intent’s expectations are met in the presence of change. And changes can come from either the operator (business rule change) or the infrastructure (operational status change).
In order to enforce that intent expectations are met, the IBNS has to be the
single source of truth (regarding the intended state of both your infrastructure and your business rules) that one can
programmatically reason about in the presence of
In the absence of this you will be spending most of your time immersed in accidental complexity developing a coordination layer that synchronizes a growing number of sources of truth that come with different formats and semantics.
One can argue that “everything can be done in software” and so can the reasoning logic described above. In a worst case example, one could envision writing a script that consolidates a set of all sources of truth scattered across various files and databases and then reason about the resulting output. Beyond simple automation tasks, the complexity of the system will quickly become unmanageable. Add the requirement for intent to be dynamic, and this solution becomes quickly unworkable
Reasoning about intent programmatically is the key enabler for the automation of all aspects of the service lifecycle such as design, build (including resource allocation), semantic validation, configuration rendering, expectation generation, test execution, anomaly detection, troubleshooting, change request validation and refutation.
And reasoning about intent needs to be maintainable and testable in the presence of change. In order to achieve this, the IBN solution is required to have the following capabilities:
Ability to easily extend the schema of this single source of truth to address new business rules and infrastructure capabilities.
Ability to programmatically decompose the single source of truth into subsets of elements of interest as it grows in size and complexity. This decomposition is the key to deal with scaling issues — i.e. an architecture that results in every piece of logic reacting to every change in intent will not scale.
Ability to get notified reactively about the nature of a change (addition, update, deletion) in the intent. This asynchronous, reactive capability (as opposed to polling) is another key to addressing scaling issues as intent gets more complicated.
Ability for components to communicate in reaction to a change in intent.
Ability for network operators to insert their expertise by enabling them to insert their own logic and programmatically reason about the intent, all in the presence of change.
Ability to add support for new innovative features offered by modern infrastructure platforms.
Ability to add support for a collection of new telemetry data.
Ability to launch Intent-Based Analytics to extract knowledge out of raw telemetry data.
We recommend that you use the above list as a checklist for validating IBN compliance when evaluating IBN solutions.
In summary, the intent definition language (allowing you to define that single source of truth) AND reasoning about intent has to be built into the IBN platform.
Why does “built into the IBNS platform” matter? Because it means less code (bugs) to write, review, and maintain, less tests to write, review, and maintain. In short, more agility and availability. In its absence you can expect the complexity of your solution to spiral out of control in the presence of change.
Intent-Based Networking brings the best software practices into network service lifecycle management. The benefit of starting with a good foundational architecture is a measurable increase in feature velocity. Another critical advantage resides in the opportunity to become hardware vendor independent. We encourage you to test drive a complete IBN system and explore the benefits today. We believe that you’ll be pleased by how quickly it will enable you to design, build, operate and validate your network — providing more agility and reliability than you have ever experienced before, while slashing your operational costs.
Network Field Day 16 was a good day for Apstra. Sasha Ratkovic, our CTO and cofounder, Damien Garros, Consulting Systems Engineer, and I all presented to a great group of people. This was our first opportunity to show the world what the Apstra Operating System (AOS™) looks like under the hood. We were excited to show developers and DevOps minded folk, who might leverage AOS to build custom network automation applications, the power that they have at their fingertips.
We first talked a little bit about how the network engineering family is growing with a new specialized persona: the Network Automation Architect. This isn’t necessarily a developer, but someone who has deep network engineering expertise that can work with developers to model end-to-end network services and their supporting mechanisms. By providing developers or DevOps folks with the right details (and using AOS as the automation platform), people in this new role will have serious impact on the operational effectiveness and service delivery capabilities of the broader organization. Fewer mistakes, more uptime, faster application delivery. Isn’t that what IT is all about?
For the remainder of the presentation Sasha and Damien went back and forth as they walked the audience through a few examples, with demos (all this is real, no slideware here!) showing how one might approach the problem of modeling where applications are located at the edge of the network. With this information we can craft interesting queries for AOS such as “show me where congestion is happening for application foo.” We also talked briefly about more complicated examples such as using VRFs to establish isolated forwarding domains in the network to contain various security zones. I do love me some VRFs!
There was a very important theme, however, throughout the presentation: Test-driven engineering. Both for the network and for developers building on top of our platform. At Apstra, we firmly believe that any Intent-Based Networking System must validate the state of the underlying systems both at the device and the more abstract inter-device level. In other words, changes in the network should always be tested by examining the resulting state of the network. For developers building apps on top of AOS, they need the right development tools to validate that their apps are working as expected before they are deployed. Again, AOS provides that!
Click on the links to the right to watch each of section of our presentation. When done, reach out to us if you have any questions. In fact, schedule an on-site demo! It’ll cost you nothing but time, and I promise it’ll be worth every second!