RFC 7710 - Captive-Portal Identification Using DHCP or Router Advertisements (RAs)

Olafur Gudmundsson
IETF RFC, Internet Engineering Task Force (2015), pp. 8
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Abstract

In many environments offering short-term or temporary Internet access
(such as coffee shops), it is common to start new connections in a
captive-portal mode. This highly restricts what the customer can do
until the customer has authenticated.

This document describes a DHCP option (and a Router Advertisement
(RA) extension) to inform clients that they are behind some sort of
captive-portal device and that they will need to authenticate to get
Internet access. It is not a full solution to address all of the
issues that clients may have with captive portals; it is designed to
be used in larger solutions. The method of authenticating to and
interacting with the captive portal is out of scope for this
document.