If you're attempting to network containers, you'll have to use one of two plug-ins. One of them talks to libnetwork, the library developed by Docker Inc. for networking Docker containers.

Networking startup Weaveworks, in code being released today, is formalizing its support for the other option — the Container Network Interface (CNI). Specifically, Weave Net 1.5 includes a plug-in for the version of CNI that's included in Kubernetes 1.2.

Weaveworks intends that "apps running on Kubernetes can support the kind of networking we provide," says Matthew Lodge, Weaveworks' chief operating officer. Kubernetes is an open source container orchestration platform, originated by Google, which has become popular in Docker environments.

Weaveworks has already been talking about CNI support. Today's release makes it formal and syncs up Weaveworks with the latest Kubenetes release.

Weaveworks describes this move as a step toward making containers more plug-and-play, so that operators can vary their choices of container networking and orchestration platforms. But it's also a way to broaden the potential audience for Weave Net, which is still on its way to becoming a commercial product.

Founded in September 2014, Weaveworks offers its software in open source form. A commercial version of the product is still being fleshed out and won't appear until late this year, Lodge says.

Weave Net uses virtual overlay networks to connect containers together into a kind of "micro SDN," as noted in the SDxCentral report, "Inside the Linux Container Ecosystem."

Overlays are becoming the preferred way to network containers. What makes Weave Net different is that it uses Layer 3 routing. Each Docker host includes a router container, and these containers talk to one another just as routers do.

What that buys you is resilience. No external database is keeping track of network state for each node, unlike with Docker networking. When a router goes down, the network routes traffic around the dead spot until the router can recover. (Weave Net 1.5 also includes improvements that speed up this recovery process, according to Lodge.)

Another factor that makes Weave Net stand out is its support for multicast networking, says Lodge. This could appeal to the financial industry, where market data needs to be spread to hordes of applications. Multicast happens to be used by Weaveworks' marquee customer, the International Securities Exchange.

Photo: By Owen Byrne on Flickr. CC2.0 license. Photo has been cropped.