# Custom Services

When you create a policy, you must define a service for it. You can select one of the predefined services from the Service Book, or select a custom service. A custom service is a service created by a user. Each policy can reference either a single service, or a service group.

Currently, a NetScreen device supports over 30 predefined services, such as HTTP, SNMP, FTP. You can also create service groups that contain any combination of predefined and custom services. You can then apply these service groups to a policy, thus simplifying administration. You cannot modify predefined services, only user-created custom services or service groups.

## Viewing the Custom Service List

This table lists all custom services created on the NetScreen device and contains the following information:

Name: Indicates the name of the custom service.

Transport Protocol and Parameters: Indicates the type of protocol the service uses (TCP or UDP for example), the range of source (internal) port numbers that are valid for the service, and the range of destination (external) port numbers that receive the service request.

Timeout: Indicates the timeout (in minutes) for the service session.

Configure: Click Edit to modify an entry, or click Remove to delete it.

Note: You cannot modify or remove any of the predefined services.

### To add a Custom Service

To add a new custom service to the Service Book, click New. For more information, see Custom Service Configuration.

### To Modify an Existing User-Defined Service Entry

1. In the Configure column, click Edit for the service that you want to modify.

The Service Configuration page appears.

2. Enter the new information, and then click OK to save your changes.

### To Remove an Existing Service Entry

1. In the Configure column, click Remove for the service that you want to delete.

A system message prompts you to confirm the removal.

2. Click Yes to remove the service, or No to cancel.