Abbreviated as NAS, a network access server
is an access gateway
between an external communications network
and an internal network. A common use of NAS is by Internet service providers (ISP
) where the user dials into the ISP and is given access to the Internet
after being authorized by the access server. Network access server (NAS) is also referred to as a remote access server
(RAS) or as a media gateway. The IETF
Network Access Server Requirements Working Group is responsible for defining the requirements for modern network access servers.