A domain name may point to multiple IP addresses to provide server redundancy for the services offered, a feature that is used to manage the traffic of large, popular web sites.
Web hosting services, on the other hand, run servers that are typically assigned only one or a few addresses while serving websites for many domains, a technique referred to as virtual web hosting. Such IP address overloading requires that each request identifies the domain name being referenced, for instance by using the HTTP request header field Host:, or Server Name Indication.
Domain registration information is maintained by the domain name registries, which contract with domain registrars to provide registration services to the public. An end user selects a registrar to provide the registration service, and that registrar becomes the designated registrar for the domain chosen by the user.
Only the designated registrar may modify or delete information about domain names in a central registry database. It is not unusual for an end user to switch registrars, invoking a domain transfer process between the registrars involved, that is governed by specific domain name transfer policies.
When a registrar registers a com domain name for an end-user, it must pay a maximum annual fee of US$7.85 to VeriSign, the registry operator for com, and a US$0.18 annual administration fee to ICANN. Most domain registrars price their services and products to address both the annual fees and the administration fees that must be paid to ICANN. Barriers to entry into the bulk registrar industry are high for new companies without an existing customer base.
Many registrars also offer registration through reseller affiliates. An end-user registers either directly with a registrar, or indirectly through one or more layers of resellers. As of 2010, the retail cost generally ranges from a low of about $7.50 per year to about $35 per year for a simple domain registration, although registrars often drop the price far lower - sometimes even free - when ordered with other products such as web hosting services.
