Posted on May 23, 2024

Project post originally published on the Istio blog by Lin Sun, Solo.io, for the Istio Steering and Technical Oversight Committees

Layer 4 & Layer 7 features are both now ready for production.

Today, Istio’s revolutionary new ambient data plane mode has reached Beta. Ambient mode is designed for simplified operations, broader application compatibility, and reduced infrastructure cost. It gives you a sidecar-less data plane that’s integrated into your infrastructure, all while maintaining Istio’s core features of zero-trust security, telemetry, and traffic management.

Ambient mode was announced in September 2022. Since then, our community has put in 20 months of hard work and collaboration, with contributions from Solo.io, Google, Microsoft, Intel, Aviatrix, Huawei, IBM, Red Hat, and many others. Beta status in 1.22 indicates the features of ambient mode are now ready for production workloads, with appropriate precautions. This is a huge milestone for Istio, bringing both Layer 4 and Layer 7 mesh features to production readiness without sidecars.

Why ambient mode?

In listening to feedback from Istio users, we observed a growing demand for mesh capabilities for applications — but heard that many of you found the resource overhead and operational complexity of sidecars hard to overcome. Challenges that sidecar users shared with us include how Istio can break applications after sidecars are added, the large consumption of CPU and memory by sidecars, and the inconvenience of the requirement to restart application pods with every new proxy release.

As a community, we designed ambient mode to tackle these problems, alleviating the previous barriers of complexity faced by users looking to implement service mesh. The new feature set was named ‘ambient mode’ as it was designed to be transparent to your application, ensuring no additional configuration was required to adopt it, and required no restarting of applications by users.

In ambient mode it is trivial to add or remove applications from the mesh. You can now simply label a namespace, and all applications in that namespace are added to the mesh. This immediately secures all traffic with mTLS, all without sidecars or the need to restart applications.

Refer to the Introducing Ambient Mesh blog for more information on why we built ambient mode.

How does ambient mode make adoption easier?

Istio’s ambient mode introduces lightweight, shared Layer 4 (L4) node proxies and optional Layer 7 (L7) proxies, removing the need for traditional sidecar proxies from the data plane. The core innovation behind ambient mode is that it slices the L4 and L7 processing into two distinct layers. This layered approach allows you to adopt Istio incrementally, enabling a smooth transition from no mesh, to a secure overlay (L4), to optional full L7 processing — on a per-namespace basis, as needed, across your fleet.

Ambient mode works without any modification required to your existing Kubernetes deployments. You can label a namespace to add all of its workloads to the mesh, or opt-in certain deployments as needed. By utilizing ambient mode, users bypass some of the previously restrictive elements of the sidecar model. Server-send-first protocols now work, most reserved ports are now available, and the ability for containers to bypass the sidecar — either maliciously or not — is eliminated.

The lightweight shared L4 node proxy is called the ztunnel (zero-trust tunnel). Ztunnel drastically reduces the overhead of running a mesh by removing the need to potentially over-provision memory and CPU within a cluster to handle expected loads. In some use cases, the savings can exceed 90% or more, while still providing zero-trust security using mutual TLS with cryptographic identity, simple L4 authorization policies, and telemetry.

The L7 proxies are called waypoints. Waypoints process L7 functions such as traffic routing, rich authorization policy enforcement, and enterprise-grade resilience. Waypoints run outside of your application deployments and can scale independently based on your needs, which could be for the entire namespace or for multiple services within a namespace. Compared with sidecars, you don’t need one waypoint per application pod, and you can scale your waypoint effectively based on its scope, thus saving significant amounts of CPU and memory in most cases.

The separation between the L4 secure overlay layer and L7 processing layer allows incremental adoption of the ambient mode data plane, in contrast to the earlier binary “all-in” injection of sidecars. Users can start with the secure L4 overlay, which offers a majority of features that people deploy Istio for (mTLS, authorization policy, and telemetry). Complex L7 handling such as retries, traffic splitting, load balancing, and observability collection can then be enabled on a case-by-case basis.

What is in the scope of the Beta?

We recommend you explore the following Beta functions of ambient mode in production with appropriate precautions, after validating them in test environments:

Alpha features

Many other features we want to include in ambient mode have been implemented, but remain in Alpha status in this release. Please help test them, so they can be promoted to Beta in 1.23 or later:

Roadmap

We have a number of features which are not yet implemented in ambient mode, but are planned for upcoming releases:

What about sidecars?

Sidecars are not going away, and remain first-class citizens in Istio. You can continue to use sidecars, and they will remain fully supported. For any feature outside of the Alpha or Beta scope for ambient mode, you should consider using the sidecar mode until the feature is added to ambient mode. Some use cases, such as traffic shifting based on source labels, will continue to be best implemented using the sidecar mode. While we believe most use cases will be best served with a mesh in ambient mode, the Istio project remains committed to ongoing sidecar mode support.

Try ambient mode today

With the 1.22 release of Istio and the Beta release of ambient mode, it is now easier than ever to try out Istio on your own workloads. Follow the getting started guide to explore ambient mode, or read our new user guides to learn how to incrementally adopt ambient for mutual TLS & L4 authorization policy, traffic management, rich L7 authorization policy, and more. You can engage with the developers in the #ambient channel on the Istio Slack, or use the discussion forum on GitHub for any questions you may have.

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