> ## Documentation Index > Fetch the complete documentation index at: https://datum.net/docs/llms.txt > Use this file to discover all available pages before exploring further. # Network services > Give a workload's Instances a stable name and named ports on a gVPC network, and send load balancer traffic to them. A network service gives a workload's Instances on one network a stable name and named ports. Datum keeps the service's membership current as Instances start, stop, and move between locations, and sends each request to the nearest location that has a ready Instance. Datum's [Application Load Balancer](https://datum.net/docs/alb/overview.md) reaches a workload through a network service. > [!NOTE] > > gVPC is in preview, and the `networking.datumapis.com/v1alpha` API can change. ## How network services work A network service is a `NetworkService` resource with two parts: * **A selector:** labels that an Instance's network interface must carry to belong to the service. Every Instance of a workload carries the workload's name as a label, so a service usually selects one workload. * **Ports:** the ports the Instances listen on, each with a name, such as `http` on port `8080`. A load balancer refers to a port by its name, not its number. Keep the following points in mind: * **One network:** A service covers Instances on one network. If the selector matches Instances on more than one network, the service serves none of them. * **Ready Instances only:** A service sends traffic only to Instances that report themselves ready. An Instance that is starting, failing, or shutting down doesn't receive traffic. * **Nearest location first:** Each request goes to the nearest location with a ready Instance. If that location has none, the request goes to the next nearest. * **Created before the workload:** You can create a service before its workload exists. The service starts serving when matching Instances are ready. When you publish a workload with `datumctl compute deploy --http-port`, the command creates a network service named after the workload. For more information, see [Compute and ALB](https://datum.net/docs/compute/compute-and-alb.md). ## Before you begin * Install `datumctl`, log in, and select a project. For more information, see [Install datumctl](https://datum.net/docs/datumctl/install.md). * Install the `network` plugin. For more information, see [Install the plugin](https://datum.net/docs/galactic-vpc/operations.md#install-the-plugin). * To create, change, or delete network services, you need the **Network Admin** role in the project. ## Create a network service To create a network service for a workload, run the following command: ```bash theme={null} datumctl network service create SERVICE_NAME \ --workload=WORKLOAD_NAME \ --port=PORT_NAME:PORT_NUMBER ``` Replace the following: * `SERVICE_NAME`: a name for the service. You can't change the name later. * `WORKLOAD_NAME`: the name of the workload whose Instances answer for the service. * `PORT_NAME`: a name for the port, such as `http`. Use lowercase letters, numbers, and hyphens. * `PORT_NUMBER`: the port that your Instances listen on, such as `8080`. To add more ports, repeat `--port`. A service takes up to 16 ports, and each name and number must be unique. By default, a load balancer connects to a port over HTTP/1.1. For a port that serves gRPC or another HTTP/2 app without TLS (h2c), use the long form of `--port` with `app-protocol=h2c`, such as `--port=name=grpc,port=9090,app-protocol=h2c`. The load balancer then sends every request on that port as HTTP/2. Most servers accept WebSockets only over HTTP/1.1, so serve WebSockets on a different port. To select Instances by label instead of by workload, use `--selector`, such as `--selector app=web`. The labels must be on the Instances' network interfaces, not only on the workload. ## Send load balancer traffic to a network service To send a load balancer's traffic to a network service, name the service and one of its port names: ```bash theme={null} datumctl alb create LOAD_BALANCER_NAME \ --network-service=SERVICE_NAME \ --port=PORT_NAME ``` For more information, see [Create a load balancer](https://datum.net/docs/alb/operations/overview#create-a-load-balancer). ## Check a network service To see what a service selects, its ports, and where it's serving, run the following command: ```bash theme={null} datumctl network service describe SERVICE_NAME ``` The output ends with a diagnosis. If the service isn't serving, the output also lists the Instances that aren't ready and what each one reports. The following table describes the most common reasons that a service isn't serving: | Reason | Meaning | What to do | | - | - | - | | `NoMatchingInterfaces` | No Instance matches what the service selects. | Start the workload, or fix the selector. The output lists the workloads in your project so that you can compare names. | | `MultipleNetworks` | The selector matches Instances on more than one network. | Narrow the selector so that it matches Instances on one network. | | `NoServingLocations` | The service has Instances, and none of them is ready. | Check the workload. Its Instances might be starting or failing. | ## Change a network service To change which workload a service selects, run the following command: ```bash theme={null} datumctl network service update SERVICE_NAME --workload=WORKLOAD_NAME ``` To change a service's ports, run the following command: ```bash theme={null} datumctl network service update SERVICE_NAME --port=http:8080 --port=metrics:9100 ``` `--port` replaces the whole port list, so name every port that the service should keep. A load balancer that refers to a port name that you remove stops reaching the service. ## Delete a network service To delete a network service, run the following command: ```bash theme={null} datumctl network service delete SERVICE_NAME ``` Before it asks you to confirm, the command lists the load balancers that send traffic to the service. Those load balancers stop reaching anything on that route. ## What's next * To manage networks and Instances' network interfaces from the command line, see [Operations](https://datum.net/docs/galactic-vpc/operations.md). * To publish a workload with a load balancer in one step, see [Compute and ALB](https://datum.net/docs/compute/compute-and-alb.md). * To learn how Instances connect privately, see [Traffic and connecting](https://datum.net/docs/galactic-vpc/networks/traffic.md). This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.