1.3. Service Mesh and Istio differences

The main difference between a multitenant installation and a cluster-wide installation is the scope of privileges used by the control plane deployments, for example, Galley and Pilot. The components no longer use cluster-scoped Role Based Access Control (RBAC) resource ClusterRoleBinding.

Every project in the ServiceMeshMemberRoll members list will have a RoleBinding for each service account associated with the control plane deployment and each control plane deployment will only watch those member projects. Each member project has a maistra.io/member-of label added to it, where the member-of value is the project containing the control plane installation.

Red Hat OpenShift Service Mesh configures each member project to ensure network access between itself, the control plane, and other member projects. The exact configuration differs depending on how OpenShift software-defined networking (SDN) is configured. See About OpenShift SDN for additional details.

If the OpenShift Container Platform cluster is configured to use the SDN plug-in:

Upstream Istio has two cluster scoped resources that it relies on. The MeshPolicy and the ClusterRbacConfig. These are not compatible with a multitenant cluster and have been replaced as described below.

The command line tool for Red Hat OpenShift Service Mesh is oc.  Red Hat OpenShift Service Mesh  does not support istioctl.

The upstream Istio community installation automatically injects the sidecar into pods within the projects you have labeled.

Red Hat OpenShift Service Mesh does not automatically inject the sidecar to any pods, but requires you to opt in to injection using an annotation without labeling projects. This method requires fewer privileges and does not conflict with other OpenShift capabilities such as builder pods. To enable automatic injection you specify the sidecar.istio.io/inject annotation as described in the Automatic sidecar injection section.

Istio Role Based Access Control (RBAC) provides a mechanism you can use to control access to a service. You can identify subjects by user name or by specifying a set of properties and apply access controls accordingly.

The upstream Istio community installation includes options to perform exact header matches, match wildcards in headers, or check for a header containing a specific prefix or suffix.

Red Hat OpenShift Service Mesh extends the ability to match request headers by using a regular expression. Specify a property key of request.regex.headers with a regular expression.

apiVersion: "rbac.istio.io/v1alpha1"
kind: ServiceRoleBinding
metadata:
  name: httpbin-client-binding
  namespace: httpbin
spec:
  subjects:
  - user: "cluster.local/ns/istio-system/sa/istio-ingressgateway-service-account"
    properties:
      request.headers[<header>]: "value"

apiVersion: "rbac.istio.io/v1alpha1"
kind: ServiceRoleBinding
metadata:
  name: httpbin-client-binding
  namespace: httpbin
spec:
  subjects:
  - user: "cluster.local/ns/istio-system/sa/istio-ingressgateway-service-account"
    properties:
      request.regex.headers[<header>]: "<regular expression>"

Red Hat OpenShift Service Mesh replaces BoringSSL with OpenSSL. OpenSSL is a software library that contains an open source implementation of the Secure Sockets Layer (SSL) and Transport Layer Security (TLS) protocols. The Red Hat OpenShift Service Mesh Proxy binary dynamically links the OpenSSL libraries (libssl and libcrypto) from the underlying Red Hat Enterprise Linux operating system.

Red Hat OpenShift Service Mesh includes CNI plug-in, which provides you with an alternate way to configure application pod networking. The CNI plug-in replaces the init-container network configuration eliminating the need to grant service accounts and projects access to Security Context Constraints (SCCs) with elevated privileges.

OpenShift routes for Istio Gateways are automatically managed in Red Hat OpenShift Service Mesh. Every time an Istio Gateway is created, updated or deleted inside the service mesh, an OpenShift route is created, updated or deleted.

A Red Hat OpenShift Service Mesh control plane component called Istio OpenShift Routing (IOR) synchronizes the gateway route. For more information see the "Automatic route creation" section.