ource</em> value, just like <em>destination</em>, specifies a FQDN of a service, either implicitly or explicitly.</p><p><em>2. Restrict to specific versions of the caller</em>. For example, the following rule refines the previous example to only apply to calls from version “v2” of the “reviews” service.</p><div class="language-yaml highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="na">apiVersion</span><span class="pi">:</span> <span class="s">config.istio.io/v1alpha