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I’ve predicted that virtual networks will be hot in 2023, but that begs the question of what exactly a “virtual network” is. One definition says, “not physically existing as such but made by software to appear to do so”, and that surely makes you wonder how businesses would be willing to commit to such a thing. Truth is, they already have, but I think it’s time to look closely at the concept of virtual networks, and to categorize what exactly is going on there. Why look at something that isn’t real and only appears to be?  We’ll see.

I could offer a lot of discussions on the early days of virtual network evolution here, but they’re probably as useless as a debate on where your lap goes when you stand up, an example of worthless effort I recall from a childhood book. Instead, let’s look at virtual networks from two directions—the user and the application—and see how those two directions are shaping virtual network technology, increasing its importance, and converging on a new network model overall.

The most ubiquitous virtual-network thing we have in the data center may not be what you’d think of as a virtual network at all. I doubt there are any users anywhere who don’t use private IP addresses. Your home internet is supported on a private IP address, and popular container technologies use private IP addresses as well. These addresses are called “private” because they exist only inside an IP subnet, and using them in container networks means that components of an application can communicate locally but can’t be externally referenced unless they’re explicitly exposed by linking them to a public address.

The problem with private IP addresses is that they aren’t unique, which means users’ traffic and connectivity could get mingled, creating security and SLA issues. The data center usage of what we could perhaps call “real” virtual networks came about as a way to keep users (tenants) of cloud and other virtual-hosting services separated. Public clouds use virtual networks, and vendors including Cisco, Juniper, IBM/Red Hat, Nokia, and VMware offer commercial virtual-network products. These are based on what’s called an “overlay” technology, meaning that traditional LAN or IP networks carry another layer of addressing, the virtual network addresses, and there’s another layer of routing that directs packets based on the addresses at this new layer.

This virtual-network model reaches beyond the data center, too. You can create a virtual network that’s laid on top of your real IP network, and its users can communicate only with other members of the same virtual network, which is sort of like a closed user group. That means that modern virtual networks can separate tenants/users, applications, organizations, or whatever you like, all without changing the real network below.  It’s almost application- or mission-centric networking. However, enterprises have been slow to adopt a comprehensive virtual-network model.

Arguably the biggest development in virtual networking came along from the user side as a result of the growing cost concerns regarding the connecting of small sites to the company VPN. Traditional VPNs based on MPLS require usage of border gateway protocol (BGP), routers, and often some form of carrier Ethernet access, all of which can drive small-site connection costs so high that CFOs cringe at any suggestion that the sites should be on the company network. But, as worker empowerment through application and data access became more important to businesses, they were trapped.  So along came SD-WAN.

Copyright © 2023 IDG Communications, Inc.


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