An organization that registers i-names and i-numbers for the XRI naming system (see XRI). I-brokers also provide services for the registrant. They may offer any number of services, but contact, OpenID and forwarding are mandatory. After registering an i-name, the i-broker creates an XRDS document that includes the i-name and i-number for that registrant along with the URLs to the various services. The location of the XRDS is managed by the global XRI resolution system operated by NeuStar at xri.net. When xri.net resolves an i-name, it returns the URL of the appropriate service to the program that requested it, which could be the user's browser. Resolving an i-name to the XRDS document is similar to resolving a domain name to an IP address in the DNS system (see DNS). Contact Service The contact service provides a messaging application that can be published without the risk of generating spam, because users must verify their e-mail addresses or i-names. It is generally the default service, and a plain resolution request redirects the user to the contact service. In the example below, the contact page is delivered if only the i-name for Alan Freedman, editor of this encyclopedia, is presented. OpenID Service I-brokers serve as an OpenID identity provider for the i-name registrant. OpenID, an emerging single sign-on system, supports i-names as identifiers (see OpenID). Forwarding Service The i-broker forwarding service redirects a user to any URL. For example, to go to Alan Freedman's company website, "+work" is appended to the i-name (=alan.freedman/+work). To send an e-mail message, +email is appended (alan.freedman/+email). The i-broker forwarding service provides persistent addresses to the outside world. If registrants change their employment, they only need to change the URLs in their i-broker forwarding service. See i-name, XRI and XRDS.