on a RADIUS environment. Some vendors have build NAS monitoring
tools either into their RADIUS servers, either directly or as
auxiliary deamons, that can check the session status of the
controlled NASes by SNMP or proprietary methods.
Other vendors monitor the RADIUS accesses and accounting messages and
derive state information from the requests. This monitoring is not
as reliable as directly auditing the NAS, but it is also less vendor
specific, and can work with any RADIUS NAS, provided it sends both
streams to the same server.
Some of the approaches used:
Mitton Informational [Page 10]
RFC 2882 Extended RADIUS Practices July 2000
- SNMP commands
- Telnet monitor deamon
- Accounting monitor
6.4. Authorization Changes:
To implement an active changes to a running session, such as filter
changes or timeout and disconnect, at least one vendor has added a
RADIUS "server" to his NAS. This server accepts messages sent from an
application in the network, and upon matching some session
information, will perform such operations.
Messages sent from Server to NAS
- Change Filter Request
- Change Filter Ack / Nak
- Disconnect Request
- Disconnect Response
Filters are used to limit the access the user has to the network by
restricting the systems and protocols he can send packets to. Upon
fulfilling some registration with an authorization server, the
service provider may wish to remove those restrictions, or disconnect
the user.
7. Policy Services
Some vendors have implemented policy servers using RADIUS as the
control protocol. Two prominent Policy Managers act as RADIUS proxy
filters and use RADIUS messages to deny access to new sessions that
exceed active policy limits.
One implementation behaves like a RADIUS proxy server, but with a
policy process governing it's forward decisions. Typically a pre-
authentication message (like the new RADIUS draft Service-Type =
CallCheck) is emitted by the NAS upon call arrival. This message will
contain only the Dialed-Number information in the Username field.
The server receives the Access-Request messages and processes them
against it's knowledge of the network state and the provisioned
policies.
An Access-Accept will be returned to the system to accept the call,
and many also contain dynamic policy information and Virtual POP
specific default parameters. When the real PPP authentication is
engaged, the proxy will forwards the Access-Request to a RADIUS
server, if this session was approved at pre-auth. It can also
process Access-Requests that were not preceded by a pre-auth
(74 paginas)
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