Software-Defined WAN (SD-WAN)

Software-Defined WAN (SD-WAN) is the second “software-defined” marketing attempt (after the original SDN) to dress a conglomerate of old technologies into shiny new clothes. Even Wikipedia article promotes some of the usual software-defined hype, quoting Network World claim that:

SD-WAN simplifies the management and operation of a WAN by decoupling the networking hardware from its control mechanism. This concept is similar to how software-defined networking implements virtualization technology to improve data center management and operation.

Is It Real?

Want to know how real those claims are? Start the journey with this series of myth-busting blog posts:

• Software-Defined WAN:Well-Orchestrated Duct Tape? (2015)
• Routing Protocols and SD-WAN: Apples and Furbies (2015)
• Do Enterprises Need MPLS? (2016)
• Lack of Fast Convergence in SD-WAN Products (2018)
• Lock-In and SD-WAN: a Match Made in Heaven (2019)
• Impact of Controller Failures in Software-Defined Networks (2019)
• Fast Failover in SD-WAN Networks (2020)

Does SD-WAN make sense? Sure:

• Business Case for SD-WAN (2015)
• Reliability of SD-WAN and Hybrid WAN Solutions (2015)

Need More Details?

I covered the basics of SD-WAN in Choose the Optimal VPN Service and SDN Use Cases webinars.

Pradosh Mohapatra described the basics of SD-WAN and its typical components and architectures:

• What Is SD-WAN?
• SD-WAN Reference Design
• SD-WAN Backend Architecture
• SD-WAN CPE Architecture
• Security Aspects of SD-WAN

Want to know more about Cisco’s SD-WAN solution (formerly known as Viptela)? Enjoy David Peñaloza Seijas’ deep dive into its architecture and implementation details:

• Going Beneath the Cisco SD-WAN Surface
• Cisco SD-WAN Fundamentals and Definitions
• Cisco SD-WAN Solution Architecture and Components
• Cisco SD-WAN Routing Goodness
• Cisco SD-WAN Onboarding Process
• Cisco SD-WAN Policies and Centralized Magic
• Cisco SD-WAN Policies Review
• Cisco SD-WAN Routing Design
• Cisco SD-WAN Site Design
• Cisco SD-WAN Policy Design

Real-Life SD-WAN

SD-WAN sounds great, but does it work as expected? Maybe not:

• SDN, SD-WAN and FCoE on Gartner Networking Hype Cycle (2015)
• SD-WAN Reality Gap (2019)
• Real-Life SD-WAN Experience (2019)
• Worth Reading: SD-WAN Scalability Challenges (2020)
• Feedback from Another SD-WAN Fan (2020)

Is it secure? Some products seem to be nothing more than a bunch of open-source component glued together with clueless Python code:

• Security Aspects of SD-WAN Solutions (2018)
• SD-WAN Security Under the Hood (2019)
• SD-WAN Security: A Product Liability Insurance Law Would Certainly Help (2020)
• Another SD-WAN Security SNAFU: SQL Injections in Cisco SD-WAN Admin Interface (2021)

Some service providers want to use SD-WAN to offer managed services. Not surprisingly, some people¹ don’t find that a good idea:

• SD-WAN: A Service Provider Perspective (2020)
• Managed SD-WAN Services (2022)
• Challenges of Managed SD-WAN Services (2022)

Then there are some technical details vendors love to gloss over:

• Does Unequal-Cost Multipathing Make Sense? (2021)
• Topology- and Congestion-Driven Load Balancing (2021)

Does it work within a public cloud? Yeah, sort of… with a few challenges:

• Azure Route Server: The Challenge (2021)
• Azure Route Server: Behind the Scenes (2021)

Want Even More?

Love marketing-related rants? Here are a few:

• Some Ridiculous SD-WAN Claims (2015)
• What Is Software-Defined Security? (2016)
• This Is Why I’m Not Doing SD-WAN Webinars (2016)
• The Ever-Increasing Complexity (2017)
• SD-WAN Vendor Landscape (2019)

Last, but definitely not least, you might enjoy these (more esoteric) solutions:

• DLSP – QoS-Aware Routing Protocol on Software Gone Wild (2015)
• Changing Cisco IOS BGP Policies Based on IP SLA Measurements (2019)
• Overlay Networking with Ouroboros on Software Gone Wild (2020)
• Scalable Policy Routing (2021)

Blog Posts I Forgot to Categorize

• Does EVPN/VXLAN over SD-WAN Make Sense?