update service sync (#250)

kubernetes/deployment-concerns.adoc

@@ -5,6 +5,7 @@ This guide focusses on the following goals:
 
 * xref:increased-traffic[]
 * xref:high-availability[]
+* xref:service-sync[]
 
 // Type:procedure
 [id="increased-traffic"]
@@ -101,3 +102,6 @@ data:
 Setting the number of routers to more than two does not provide increased availability and can adversely affect performance.
 
 Note: Clients must reconnect when a router restarts or traffic is redirected to a backup router.
+
+
+include::service-sync.adoc[leveloffset=+1]

kubernetes/service-sync.adoc

@@ -0,0 +1,58 @@
+// Type: reference
+[id="service-sync"] 
+= Service synchronization
+
+By default, creating a site enables that site to synchronize all services from other default sites.
+This means that all services exposed on the service network are available in the current site.
+For example, if you expose the backend service in the `east` site, that service is automatically created in the `west` site. 
+
+However, if you want more granular control over which services are available, you can disable `service-sync`.
+This might be required if:
+
+* You expose many services and not all are required on all sites.
+* You are concerned that a specific service is not available on a specific site.
+
+To disable service synchronization:
+
+[source, bash, subs=attributes+]
+----
+$ skupper init --service-sync false
+----
+
+or use the following YAML:
+
+[source, yaml, subs=attributes+]
+----
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: skupper-site
+data:
+  name: my-site
+  service-sync: false
+----
+
+To check whether synchronization is enabled, check the value for `service-sync` in the output from the following command:
+
+[source, bash, subs=attributes+]
+----
+$ kubectl get cm skupper-site -o json 
+----
+
+If you disable service-sync and you want to consume an exposed service on a specific site, you can create that service using the following command:
+
+[source, bash, subs=attributes+]
+----
+skupper service create <name> <port>
+----
+
+where `<name>` is the service name on the site where the service is exposed
+and `<port>` is the port used to expose that service.
+
+
+Notes:
+
+* When considering whether services are synchronized between two sites, `service-sync` must be enabled on both sites.
+* If you use the command `skupper service delete` on a site, that command only works if the service was created on that site.
+* Podman sites do not support `service-sync`.
+