diff --git a/assets/images/osi-model.png b/assets/images/osi-model.png
new file mode 100644
index 0000000..36fd733
Binary files /dev/null and b/assets/images/osi-model.png differ
diff --git a/categories/devops.md b/categories/devops.md
index aee3d94..3451914 100644
--- a/categories/devops.md
+++ b/categories/devops.md
@@ -53,6 +53,9 @@
 		- 172.16.0.0 – 172.31.255.255
 		- 192.168.0.0 – 192.168.255.255
 
+## OSI Model( 7 layers network)
+
+![OSI Models](https://raw.githubusercontent.com/wahyd4/knowledge-mind-mapping/master/assets/images/osi-model.png)
 # tools
 - git
 	- cherrypick
diff --git a/categories/devops/docker.md b/categories/devops/docker.md
index 6f8d849..3289460 100644
--- a/categories/devops/docker.md
+++ b/categories/devops/docker.md
@@ -3,6 +3,8 @@
 ## Orchestration
 
 ### Rancher
+
+Easy to use, just drag and drop things.
 ### Kubernetes
 
 - Pod
@@ -51,6 +53,17 @@
 Links:
 * [Kubernetes NodePort vs LoadBalancer vs Ingress? When should I use what?](https://medium.com/google-cloud/kubernetes-nodeport-vs-loadbalancer-vs-ingress-when-should-i-use-what-922f010849e0)
 
+#### Zero down time deployment
+Set strategy type to `RollingUpdate` instead of `Recreate`
+```yaml
+spec:
+  replicas: 1
+  strategy:
+    type: RollingUpdate
+    rollingUpdate:
+      maxUnavailable: 50%
+      maxSurge: 1
+```
 ## Benefits
 
 	- escape the app dependency matrix