Service URL (Service Location Protocol Administration Guide)

Service Location Protocol Administration Guide

A service URL line has three required fields and one optional field, separated by commas:

First field - This field contains the service URL to be advertised. The service URL can be either a generic URL or a service: URL. See RFC 2609 for the specification of how to form a service: URL.
Second field - This field designates the language of the advertisement. In the previous example, the field designated English, en. The language is an RFC 1766 language tag.
Third field - This field establishes the lifetime of the registration, measured in seconds. The lifetime is restricted to an unsigned 16 bit-integer. If the lifetime is less than the maximum, 65535, slpd times out the advertisement like any other advertisement. If the lifetime is 65535, slpd refreshes the advertisement periodically, and the lifetime is considered permanent, until slpd exits.

Note -
As a practical matter, nonpermanent proxy registrations are of limited usefulness, because once slpd removes the advertisement, it is no longer accessible to UAs. Both advertisements in the example are permanent.
Service type field (optional) - If used, this field defines the service type. If the service URL is a generic URL, then it is possible to change the service type under which the URL is advertised. In the previous example of a proxy registration file, line 12 contains a generic FTP URL, and the optional type field causes it to be advertised under the service type name src-server. The service: prefix is not added by default to the type name.