--- title: Using the Stream Control Transmission Protocol (SCTP) --- # Using the Stream Control Transmission Protocol (SCTP) {#using-sctp} As a cluster administrator, you can use the Stream Control Transmission Protocol (SCTP) on a bare-metal cluster. ## Support for SCTP on OpenShift Container Platform {#nw-sctp-about_using-sctp} As a cluster administrator, you can enable SCTP on the hosts in the cluster. On Red Hat Enterprise Linux CoreOS (RHCOS), the SCTP module is disabled by default. SCTP is a reliable message based protocol that runs on top of an IP network. When enabled, you can use SCTP as a protocol with pods, services, and network policy. A `Service` object must be defined with the `type` parameter set to either the `ClusterIP` or `NodePort` value. ### Example configurations using SCTP protocol {#example_configurations_using-sctp} You can configure a pod or service to use SCTP by setting the `protocol` parameter to the `SCTP` value in the pod or service object. In the following example, a pod is configured to use SCTP: ```yaml apiVersion: v1 kind: Pod metadata: namespace: project1 name: example-pod spec: containers: - name: example-pod ... ports: - containerPort: 30100 name: sctpserver protocol: SCTP ``` In the following example, a service is configured to use SCTP: ```yaml apiVersion: v1 kind: Service metadata: namespace: project1 name: sctpserver spec: ... ports: - name: sctpserver protocol: SCTP port: 30100 targetPort: 30100 type: ClusterIP ``` In the following example, a `NetworkPolicy` object is configured to apply to SCTP network traffic on port `80` from any pods with a specific label: ```yaml kind: NetworkPolicy apiVersion: networking.k8s.io/v1 metadata: name: allow-sctp-on-http spec: podSelector: matchLabels: role: web ingress: - ports: - protocol: SCTP port: 80 ``` ## Enabling Stream Control Transmission Protocol (SCTP) {#nw-sctp-enabling_using-sctp} As a cluster administrator, you can load and enable the blacklisted SCTP kernel module on worker nodes in your cluster. **Prerequisites** - Install the OpenShift CLI (`oc`). - Access to the cluster as a user with the `cluster-admin` role. **Procedure** 1. Create a file named `load-sctp-module.yaml` that contains the following YAML definition: ```yaml apiVersion: machineconfiguration.openshift.io/v1 kind: MachineConfig metadata: name: load-sctp-module labels: machineconfiguration.openshift.io/role: worker spec: config: ignition: version: 3.2.0 storage: files: - path: /etc/modprobe.d/sctp-blacklist.conf mode: 0644 overwrite: true contents: source: data:, - path: /etc/modules-load.d/sctp-load.conf mode: 0644 overwrite: true contents: source: data:,sctp ``` 2. To create the `MachineConfig` object, enter the following command: ```terminal $ oc create -f load-sctp-module.yaml ``` 3. Optional: To watch the status of the nodes while the MachineConfig Operator applies the configuration change, enter the following command. When the status of a node transitions to `Ready`, the configuration update is applied. ```terminal $ oc get nodes ``` ## Verifying Stream Control Transmission Protocol (SCTP) is enabled {#nw-sctp-verifying_using-sctp} You can verify that SCTP is working on a cluster by creating a pod with an application that listens for SCTP traffic, associating it with a service, and then connecting to the exposed service. **Prerequisites** - Access to the internet from the cluster to install the `nc` package. - Install the OpenShift CLI (`oc`). - Access to the cluster as a user with the `cluster-admin` role. **Procedure** 1. Create a pod starts an SCTP listener: 1. Create a file named `sctp-server.yaml` that defines a pod with the following YAML: ```yaml apiVersion: v1 kind: Pod metadata: name: sctpserver labels: app: sctpserver spec: containers: - name: sctpserver image: registry.access.redhat.com/ubi9/ubi command: ["/bin/sh", "-c"] args: ["dnf install -y nc && sleep inf"] ports: - containerPort: 30102 name: sctpserver protocol: SCTP ``` 2. Create the pod by entering the following command: ```terminal $ oc create -f sctp-server.yaml ``` 2. Create a service for the SCTP listener pod. 1. Create a file named `sctp-service.yaml` that defines a service with the following YAML: ```yaml apiVersion: v1 kind: Service metadata: name: sctpservice labels: app: sctpserver spec: type: NodePort selector: app: sctpserver ports: - name: sctpserver protocol: SCTP port: 30102 targetPort: 30102 ``` 2. To create the service, enter the following command: ```terminal $ oc create -f sctp-service.yaml ``` 3. Create a pod for the SCTP client. 1. Create a file named `sctp-client.yaml` with the following YAML: ```yaml apiVersion: v1 kind: Pod metadata: name: sctpclient labels: app: sctpclient spec: containers: - name: sctpclient image: registry.access.redhat.com/ubi9/ubi command: ["/bin/sh", "-c"] args: ["dnf install -y nc && sleep inf"] ``` 2. To create the `Pod` object, enter the following command: ```terminal $ oc apply -f sctp-client.yaml ``` 4. Run an SCTP listener on the server. 1. To connect to the server pod, enter the following command: ```terminal $ oc rsh sctpserver ``` 2. To start the SCTP listener, enter the following command: ```terminal $ nc -l 30102 --sctp ``` 5. Connect to the SCTP listener on the server. 1. Open a new terminal window or tab in your terminal program. 2. Obtain the IP address of the `sctpservice` service. Enter the following command: ```terminal $ oc get services sctpservice -o go-template='{{.spec.clusterIP}}{{"\n"}}' ``` 3. To connect to the client pod, enter the following command: ```terminal $ oc rsh sctpclient ``` 4. To start the SCTP client, enter the following command. Replace `` with the cluster IP address of the `sctpservice` service. ```terminal # nc 30102 --sctp ```