Network capability discovery focuses on discovery of
the services offered by networks, not just the capabilities
of individual points of attachment. By acquiring additional
information on access network characteristics, it is possible
for users to make a more informed access decision.
These characteristics may include:
; o Roaming relationships between the access network provider and
; other network providers and associated costs. Where the
; network access client is not preconfigured with an
identity and credentials corresponding to a local access
network, it will need to be able to determine whether
one or more home realms are reachable from an access network
so that successful authentication can be possible.
; o EAP authentication methods. While the EAP authentication
; methods supported by a home realm can only be determined by
; contacting the home AAA server, it is possible that the
local realm will also support one or more EAP methods.
For example, a user may be able to utilize EAP-SIM to
authenticate to the access network directly, rather than
having to authenticate to the home network.
; o End-to-end quality of service capability. While local
quality of services capabilities are typically advertised
by the access network (e.g. support for WMM), the availability
of end-to-end QoS services may not be advertised.
; o Service parameters, such as the existence of middleboxes or
; firewalls. If the network access client is not made aware
of the Internet access that it will receive on connecting to
; a point of attachment, it is possible that the user may not
; be able to access the desired services.
; Reference [IEEE.11-04-0624] classifies the possible steps at which
IEEE 802.11 networks can acquire this information:
o Pre-association
o Post-association (or pre-authentication)
; o Post-authentication
In the interest of minimizing connectivity delays, all of
the information required for network selection (including both
; access network capabilities and global characteristics) needs to
be provided prior to authentication.
; By the time authentication occurs, the node has
typically selected the access network, the NAI to be used to
authenticate, as well as the point of attachment. Should it learn
information during the authentication process that would cause it to
revise one or more of those decisions, the node will need to select a
new network, point of attachment, and/or identity, and then go
through the authentication process all over again. Such a process is
likely to be both time consuming and unreliable."
internaut.