ZNDP 42 – Intent Based Networking With Phil Gervasi

Network Community, Network Design, Podcast, ZNDP

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Hey Nerds, Geeks, and Ziglets out there.  Today’s show is covering Intent Based Networking, its a market term, a sales term, and potentially much more but before we start lets introduce our guest expert, my good friend Phil Gervasi. 

 Guest Expert: Phil Gervasi

Phil has authored a number of industry blogs and white papers, has hosted The Network Collective Podcast, has produced several videos explaining new concepts in networking, and has been a delegate to Networking Field Day numerous times. He has been working in our industry for over 10 years as a Senior Network Engineer focusing on the Enterprise vertical and Software Defined Networking solutions. He currently works for a Value added Reseller (VAR) in upstate New York. Phil is an extremely passionate teacher, always wanting to give back to this industry we all love. Please welcome my good friend Phil Gervasi to our show!!  Welcome Phil!

Phil joins the Zigbits Network Design Podcast today to discuss his vendor neutral understanding, experience and research over the last 3 years on Intent Based Networking.

Introduction to Intent Based Networking

With Intent based networking we create a shift in how we do network operations moving forward. This requires a mindset shift in how we believe networks and IT systems should be operated and maintained.

Intent based networking, or IBN, is not necessarily an appliance but a workflow that leverages known methods in a new way to the networking industry in order to create a change in methods of network operations. For example, applying a Continuous Integration and Continuous Development (CI/CD) workflow just like people already do in the developer world but instead to network infrastructure. Of course applying something like this, thats not necessarily new but is new to the network industry poses some new problems. In the past CI/CD was only concerned with software and developer lifecycles. It can be especially difficult in the network space because the network is made of physical and virtual appliances that have a lot of ephemeral (short lived) information. Think of a mac address table as an example of ephemeral information. It’s important to understand here that IBN is not simply an advanced automation or orchestration solution.

The journey into the IBN world is a progression from automation to a “closed loop system”. Automation makes pulling information from appliances and pushing configurations more efficient and with fewer errors. Orchestration goes a couple of steps further by, applying machine-to-machine automation and some level of abstraction between devices and the network operator… but this is still pulling information and pushing configuration based on operator intervention.

IBN goes even further than automation and orchestration by applying a continual process of pulling telemetry data to validate the known state against a benchmark (intent) state and then acts autonomously to resolve discrepancies from the benchmark. This cycle continues perpetually in an automated, closed loop workflow.

What is the intent of Intent Based Networking?

The easy and quick answer to this question is what the network operator wants the network to do. The important item to remember here is that the focus is on the macro configurations and not on the micro configurations.

The network operator now creates a reference architecture, also referred to as a benchmark or blueprint. This reference architecture is a pre-determined state represented logically by abstractions written in lines of code.

This is best explained with an example. Lets take a reference architecture for a spine-leaf Clos topology. In this reference architecture it would include all of the elements and objects, with all of their associated attributes and what parameters they should meet within the network operators determined Clos topology. This would be BGP configurations, IP addresses, interface configurations, etc… The network operator’s intent is captured in the reference architecture and then in a CI/CD workflow the known state can be validated against it.

How does Intent Based Networking work?

Everything in the network must be abstracted and relationships must be created based on those levels of abstractions. Of course this is done differently among the IBN vendors today as the relationships among the logical abstractions is a difficult problem to solve. Here are just a couple examples of current ways to solve it:

  • Graph database (Apstra)
  • Complex mathematical algorithms to represent network components (Forward Networks, Veriflow)

The logical abstractions need to be very modular which is why the well known tools already used today are popular: Python, C code, and structured data in JSON. This is why tools like Ansible and Swagger are used. These languages and tools are used to create logical abstractions of every single thing in the network including the reference architectures. Now everything can be plugged into a workflow which can discover information, verify information, and make changes to devices all relatively autonomously.

All the millions of objects in a network including the very sophisticated CI/CD workflows are what together comprise an IBNS. An IBNS can be a server that interacts with devices, agent based, therefore either centralized or distributed or some combination thereof. The understanding here is that there is an appliance somewhere, but its not simply a matter of adding a new shiny network appliance to a network and saying “I have an Intent Based Network”. Developers work hard to write standard code to accommodate many reference architectures and best practices. They are incorporating many network devices from different vendors and operating systems.

Communication with the network devices themselves is actually the least interesting part because its just pulling information or pushing configuration to the network devices which can be done any way that the device will accommodate. It’s important to remember here that at the end of the day, IBN is actually about configuring network appliances!

Applications of Intent Based Networking

Realistically, this is very difficult to do in real-time, production networks at any significant scale. Some IBN vendors focus on one place in the network as a result such as the Data Center (DC) or Wide Area Network (WAN).

IBN makes sense in a larger network that has numerous changes occurring regularly such as a large company with a complex DC environment that pushes out new applications to its end users or customers regularly. IBN may not make as much sense for a simple network, even a large one, such as a school district that has a huge number of ports and possibly even a somewhat sophisticated pair of data centers but extremely little change occurring.

IBN is difficult to back into an existing network and is easier to implement greenfield.

The Intent Based Networking “Hype”

The new marketing term!! Doesn’t mean IBN itself is hype… Just means that many vendors misappropriate the term. IBN is still a very compelling paradigm shift in Network operations.

The Article in Network World, A taxonomy of Intent-Based Networking (IBN), written by Sasha Ratkovic describes 4 basic levels of IBN today:

  • Level 0: Basic Automation
  • Level 1: Single Source of Truth
  • Level 2: Real-time Change Validation
  • Level 3: Self-Operation

Most solutions out there today that use the term IBN are likely advertising a level of automation in a box platform (level 0) or possibly doing advanced automation with real-time information gathering (level 1). These a great things but not a true fully intent based network as we have described it here. We need to go to the next levels of validating that information against a reference architecture and resolve discrepancies autonomously.

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