Cisco Digital Media System 3.5 User manual

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Cisco Access Registrar 3.5 Concepts and
Reference Guide
July 2004
Customer Order Number:
Text Part Number: OL-2683-02

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Cisco Access Registrar 3.5 Concepts and Reference Guide
Copyright © 2002, 2003, 2004 Cisco Systems, Inc.
All rights reserved.

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CONTENTS
About This Guide ix
Obtaining Documentation ix
World Wide Web ix
Ordering Documentation x
Documentation Feedback x
Obtaining Technical Assistance x
Cisco.com x
Technical Assistance Center xi
Contacting TAC by Using the Cisco TAC Website xi
Contacting TAC by Telephone xi
CHAPTER 1Overview 1-1
RADIUS Protocol 1-1
Steps to Connection 1-2
Types of RADIUS Messages 1-3
Packet Contents 1-3
The Attribute Dictionary 1-4
Proxy Servers 1-4
Basic Authentication and Authorization 1-5
CHAPTER 2Understanding Cisco Access Registrar 2-1
Cisco Access Registrar Hierarchy 2-1
UserLists and Groups 2-2
Profiles 2-2
Scripts 2-2
Services 2-2
Session Management Using Resource Managers 2-3
Cisco AR Directory Structure 2-4
Program Flow 2-4
Scripting Points 2-5
Client or NAS Scripting Points 2-5
Authentication and/or Authorization Scripting Points 2-6
Session Management 2-7
Failover by the NAS and Session Management 2-7

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Script Processing Hierarchy 2-8
Cross Server Session and Resource Management 2-9
Overview 2-9
Session-Service Service Step and Radius-Session Service 2-10
Configuring a Front Line Cisco Access Registrar 2-10
Configure Central AR 2-11
CHAPTER 3Cisco Access Registrar Scripts 3-1
Using Cisco AR Scripts 3-1
ACMEOutgoingScript 3-1
AltigaIncomingScript 3-1
AltigaOutgoingScript 3-2
ANAAAOutgoing 3-2
AscendIncomingScript 3-2
AscendOutgoingScript 3-2
AuthorizePPP 3-2
AuthorizeService 3-2
AuthorizeSLIP 3-2
AuthorizeTelnet 3-3
CabletronIncoming 3-3
CabletronOutgoing 3-3
CiscoIncoming 3-3
CiscoOutgoing 3-3
CiscoWithODAPIncomingScript 3-3
ExecCLIDRule 3-3
ExecDNISRule 3-4
ExecFilterRule 3-4
ExecNASIPRule 3-4
ExecRealmRule 3-4
ExecTimeRule 3-4
LDAPOutage 3-5
MapSourceIPAddress 3-5
ParseAAARealm 3-5
ParseAAASRealm 3-5
ParseAARealm 3-5
ParseAASRealm 3-5
ParseProxyHints 3-6
ParseServiceAndAAARealmHints 3-6
ParseServiceAndAAASRealmHints 3-6

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ParseServiceAndAARealmHints 3-6
ParseServiceAndAASRealmHints 3-6
ParseServiceAndProxyHints 3-6
ParseServiceHints 3-7
ParseTranslationGroupsByCLID 3-7
ParseTranslationGroupsByDNIS 3-7
ParseTranslationGroupsByRealm 3-7
UseCLIDAsSessionKey 3-7
USRIncomingScript 3-7
USRIncomingScript-IgnoreAccountingSignature 3-7
USROutgoingScript 3-8
CHAPTER 4Understanding Replication 4-1
Replication Overview 4-1
How Replication Works 4-2
Replication Data Flow 4-2
Master Server 4-2
Slave Server 4-3
Security 4-3
Replication Archive 4-3
Ensuring Data Integrity 4-3
Transaction Data Verification 4-4
Transaction Order 4-4
Automatic Resynchronization 4-4
Full Resynchronization 4-5
Understanding Hot-Configuration 4-5
Replication’s Impact on Request Processing 4-5
Replication Configuration Settings 4-5
RepType 4-6
RepTransactionSyncInterval 4-6
Master 4-6
Slave 4-6
RepTransactionArchiveLimit 4-6
RepIPAddress 4-7
RepPort 4-7
RepSecret 4-7
RepIPMaster 4-7
RepMasterIPAddress 4-7
RepMasterPort 4-7

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Rep Members Subdirectory 4-8
Rep Members/Slave1 4-8
Name 4-8
IPAddress 4-8
Port 4-8
CHAPTER 5Understanding SNMP 5-1
Overview 5-1
Supported MIBs 5-1
RADIUS-AUTH-CLIENT-MIB 5-1
RADIUS-AUTH-SERVER-MIB 5-2
RADIUS-ACC-CLIENT-MIB 5-2
RADIUS-ACC-SERVER-MIB 5-2
SNMP Traps 5-2
Supported Traps 5-3
carServerStart 5-3
carServerStop 5-3
carInputQueueFull 5-3
carInputQueueNotVeryFull 5-3
carOtherAuthServerNotResponding 5-4
carOtherAuthServerResponding 5-4
carOtherAccServerNotResponding 5-4
carOtherAccServerResponding 5-5
carAccountingLoggingFailure 5-5
Configuring Traps 5-5
Directories Searched 5-5
Configuration File Types 5-6
Switching Configuration Files in Mid-File 5-6
Community String 5-7
CHAPTER 6Prepaid Billing Solution 6-1
Overview 6-1
Configuring Prepaid Billing 6-3
Generic Call Flow 6-4
Call Flow Details 6-4
Access-Request (Authentication) 6-5
Access-Accept (Authentication) 6-6
Access-Request (Authorization) 6-6
Access-Accept (Authorization) 6-6

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Accounting Start 6-7
Data Flow 6-7
Access-Request (Quota Depleted) 6-8
Accept-Accept (Quota Depleted) 6-8
Accounting Stop (Session End) 6-9
Accounting Response (Final Status) 6-9
Vendor-Specific Attributes 6-10
G LOSSARY

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About This Guide
This document provides information to help you understand RADIUS concepts and to help you develop
a better understanding of the Cisco Access Registrar 3.0 server. This document contains the following
chapters:
•Chapter 1, “Overview,” overview of the RADIUS server, including connection steps, RADIUS
message types, and using Cisco Access Registrar as a proxy server.
•Chapter 2, “Understanding Cisco Access Registrar,” describes the Cisco Access Registrar object
structure, and explains when Cisco Access Registrar references each of these objects during the
processing of client requests.
•Chapter 3, “Cisco Access Registrar Scripts,” describes the scripts provided with Cisco Access
Registrar.
•Chapter 4, “Understanding Replication,” describes Cisco Access Registrar's configuration
replication features, functions, limitations and operation.
•Chapter 5, “Understanding SNMP,” provides information about Cisco Access Registrar support for
SNMP.
•Chapter 6, “Prepaid Billing Solution,” describes the generic call flow between the three components
required to support a prepaid billing solution using the RADIUS protocol: the AAA client, the Cisco
Access Registrar 3.0 server, and a prepaid billing server.
This guide also contains a Glossary and an Index.
Obtaining Documentation
The following sections provide sources for obtaining documentation from Cisco Systems.
World Wide Web
You can access the most current Cisco documentation on the World Wide Web at the following sites:
•http://www.cisco.com
•http://www-china.cisco.com
•http://www-europe.cisco.com

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Obtaining Technical Assistance
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About This Guide
Obtaining Technical Assistance
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The Cisco TAC website is available to all customers who need technical assistance with a Cisco product
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Contacting TAC by Using the Cisco TAC Website
If you have a priority level 3 (P3) or priority level 4 (P4) problem, contact TAC by going to the TAC
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Obtaining Technical Assistance

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1
Overview
The chapter provides an overview of the RADIUS server, including connection steps, RADIUS message
types, and using Cisco Access Registrar as a proxy server.
Cisco Access Registrar is a RADIUS (Remote Authentication Dial-In User Service) server that allows
multiple dial-in Network Access Server (NAS) devices to share a common authentication, authorization,
and accounting database.
Cisco Access Registrar handles the following tasks:
•Authentication—determines the identity of users and whether they may be allowed to access the
network
•Authorization—determines the level of network services available to authenticated users after they
are connected
•Accounting—keeps track of each user’s network activity
•Session and resource management—tracks user sessions and allocates dynamic resources
Using a RADIUS server allows you to better manage the access to your network, as it allows you to store
all security information in a single, centralized database instead of distributing the information around
the network in many different devices. You can make changes to that single database instead of making
changes to every network access server in your network.
RADIUS Protocol
Cisco Access Registrar is based on a client/server model, which supports AAA (authentication,
authorization, and accounting). The client is the Network Access Server (NAS) and the server is Cisco
Access Registrar. The client passes user information on to the RADIUS server and acts on the response
it receives. The server, on the other hand, is responsible for receiving user access requests, authenticating
and authorizing users, and returning all of the necessary configuration information the client can then
pass on to the user.
The protocol is a simple packet exchange in which the NAS sends a request packet to the Cisco Access
Registrar with a name and a password. Cisco Access Registrar looks up the name and password to verify
it is correct, determines for which dynamic resources the user is authorized, then returns an accept packet
that contains configuration information for the user session (Figure 1-1).

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Chapter 1 Overview
RADIUS Protocol
Figure 1-1 Packet Exchange Between User, NAS, and RADIUS
Cisco Access Registrar can also reject the packet if it needs to deny network access to the user. Or, Cisco
Access Registrar may issue a challenge that the NAS sends to the user, who then creates the proper
response and returns it to the NAS, which forwards the challenge response to Cisco Access Registrar in
a second request packet.
In order to ensure network security, the client and server use a shared secret, which is a string they both
know, but which is never sent over the network. User passwords are also encrypted between the client
and the server to protect the network from unauthorized access.
Steps to Connection
Three participants exist in this interaction: the user, the NAS, and the RADIUS server. The following
steps describe the receipt of an access request through the sending of an access response.
Step 1 The user, at a remote location such as a branch office or at home, dials into the NAS, and supplies a name
and password.
Step 2 The NAS picks up the call and begins negotiating the session.
a. The NAS receives the name and password.
b. The NAS formats this information into an Access-Request packet.
c. The NAS sends the packet on to the Cisco Access Registrar server.
Step 3 The Cisco Access Registrar server determines what hardware sent the request (NAS) and parses the
packet.
d. It sets up the Request dictionary based on the packet information.
e. It runs any incoming scripts, which are user-written extensions to Cisco Access Registrar. An
incoming script can examine and change the attributes of the request packet or the environment
variables, which can affect subsequent processing.
f. Based on the scripts or the defaults, it chooses a service to authenticate and/or authorize the user.
Step 4 Cisco Access Registrar’s authentication service verifies the username and password is in its database.
Or, Cisco Access Registrar delegates the authentication (as a proxy) to another RADIUS server, an
LDAP, or TACACS server.
Step 5 Cisco Access Registrar’s authorization service creates the response with the appropriate attributes for
the user’s session and puts it in the Response dictionary.
Step 6 If you are using Cisco Access Registrar session management at your site, the Session Manager calls the
appropriate Resource Managers that allocate dynamic resources for this session.
Step 7 Cisco Access Registrar runs any outgoing scripts to change the attributes of the response packet.
N
A
S
Radius
22036
Jane
xyz
request
response
Name=Jane
Password=xyz

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Chapter 1 Overview
RADIUS Protocol
Step 8 Cisco Access Registrar formats the response based on the Response dictionary and sends it back to the
client (NAS).
Step 9 The NAS receives the response and communicates with the user, which may include sending the user an
IP address to indicate the connection has been successfully established.
Types of RADIUS Messages
The client/server packet exchange consists primarily of the following types of RADIUS messages:
•Access-Request—sent by the client (NAS) requesting access
•Access-Reject—sent by the RADIUS server rejecting access
•Access-Accept—sent by the RADIUS server allowing access
•Access-Challenge—sent by the RADIUS server requesting more information in order to allow
access. The NAS, after communicating with the user, responds with another Access-Request.
When you use RADIUS accounting, the client and server can also exchange the following two types of
messages:
•Accounting-Request—sent by the client (NAS) requesting accounting
•Accounting-Response—sent by the RADIUS server acknowledging accounting
Packet Contents
The information in each RADIUS message is encapsulated in a UDP (User Datagram Protocol) data
packet. A packet is a block of data in a standard format for transmission. It is accompanied by other
information, such as the origin and destination of the data.
lists each message packet which contains the following five fields:
Table 1-1 RADIUS Packet Fields
Fields Description
Code Indicates what type of message it is: Access-Request,
Access-Accept, Access-Reject, Access-Challenge,
Accounting-Request, or Accounting-Response.
Identifier Contains a value that is copied into the server’s response so the
client can correctly associate its requests and the server’s responses
when multiple users are being authenticated simultaneously.
Length Provides a simple error-checking device. The server silently drops
a packet if it is shorter than the value specified in the length field,
and ignores the octets beyond the value of the length field.

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Chapter 1 Overview
RADIUS Protocol
The Attribute Dictionary
The Attribute dictionary contains a list of preconfigured authentication, authorization, and accounting
attributes that can be part of a client’s or user’s configuration. The dictionary entries translate an attribute
into a value Cisco Access Registrar uses to parse incoming requests and generate responses. Attributes
have a human-readable name and an enumerated equivalent from 1-255.
Sixty three standard attributes exist, which are defined in RFCs 2865, 2866, 2867, 2868, and 2869. There
also are additional vendor-specific attributes that depend on the particular NAS you are using.
Some sample attributes include:
•User-Name—the name of the user
•User-Password—the user’s password
•NAS-IP-Address—the IP address of the NAS
•NAS-Port—the NAS port the user is dialed in to
•Framed Protocol—such as SLIP or PPP
•Framed-IP-Address—the IP address the client uses for the session
•Filter-ID—vendor-specific; identifies a set of filters configured in the NAS
•Callback-Number—the actual callback number.
Proxy Servers
Any one or all of the RADIUS server’s three functions: authentication, authorization, or accounting can
be subcontracted to another RADIUS server. Cisco Access Registrar then becomes a proxy server.
Proxying to other servers enables you to delegate some of the RADIUS server’s functions to other
servers.
You can use Cisco Access Registrar to “proxy” to an LDAP server for access to directory information
about users in order to authenticate them. Figure 1-2 shows user joe initiating a request, the Cisco
Access Registrar server proxying the authentication to the LDAP server, and then performing the
authorization and accounting processing in order to enable joe to log in.
Authenticator Contains a value for a Request Authenticator or a Response
Authenticator. The Request Authenticator is included in a client’s
Access-Request. The value is unpredictable and unique, and is
added to the client/server shared secret so the combination can be
run through a one-way algorithm. The NAS then uses the result in
conjunction with the shared secret to encrypt the user’s password.
Attribute(s) Depends on the type of message being sent. The number of
attribute/value pairs included in the packet’s attribute field is
variable, including those required or optional for the type of service
requested.
Table 1-1 RADIUS Packet Fields (continued)
Fields Description

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Chapter 1 Overview
Basic Authentication and Authorization
Figure 1-2 Proxying to an LDAP Server for Authentication
Basic Authentication and Authorization
This section provides basic information about how Cisco Access Registrar performs the basic RADIUS
functions of authentication and authorization as defined in Internet RFC 2865.
•Authentication—determining the identity of a user of a client NAS through user identification and
password validation and deciding whether to grant access
•Authorization—determining the level of network services available to authenticated users after a
connection has been established
The Cisco Access Registrar (AR) server provides authentication and authorization service to clients
which are network access servers (NAS). The following paragraphs describe the steps to a connection.
1. The process begins when user dials into the NAS and enters a user name and a password. The NAS
creates an Access-Request containing attributes such as the user's name, the user's password, the ID
of the client, and the Port ID the user is accessing.
2. The Cisco AR server determines which hardware (client NAS) sent the request, parses the packet,
and determines whether to accept the request.
The Cisco AR server checks to see if the client's IP address is listed in
/Radius/Clients/<Name>/<IPAddress>.
3. After accepting the request, the Cisco AR server does the following:
– Sets up the Request Dictionary based on the packet information
– Runs any incoming scripts (user-written extensions to Cisco Access Registrar)
An incoming script can examine and change the attributes of the request packet or the
environmental variables which can affect subsequent processing.
– Based on default values or scripts, it chooses a service to authenticate and authorize the user.
The Cisco AR server directs the request to the appropriate service, which then performs
authentication and/or authorization according to the type specified in
/Radius/Services/<Name>/<Type>.
– Performs session management, directing the request to the appropriate Session Manager.
NAS
Access
registrar
LDAP
22035
user=joe
password=xyz request
response
1
6
2
5
34
Authorization
accounting
Authentication

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Basic Authentication and Authorization
– Performs resource management for each Resource Manager in the Session Manager. The Cisco
AR server directs the request to the appropriate resource manager listed in
/Radius/SessionManagers/<Name>/<ResourceManagers>/<Name>. The resource manager
then allocates or checks the resource according to the type listed in
/Radius/<ResourceManagers>/<Name>/<Type>.
4. The Cisco AR server finally creates and formats an Access-Accept, Access Reject, or Access
Challenge response, then sends it to the client (NAS).

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2
Understanding Cisco Access Registrar
This chapter describes the Cisco Access Registrar object structure, and explains when Cisco Access
Registrar references each of these objects during the processing of client requests.
Cisco Access Registrar lets you manipulate configuration objects, which define the properties or
behavior of the RADIUS server. Cisco Access Registrar also lets you invoke custom scripts to affect the
behavior of the RADIUS server.
To better understand the role each of these objects plays in the program, it is helpful to look at the steps
Cisco Access Registrar performs from receipt of an Access-Request packet to the sending of an
Access-Response packet.
Cisco Access Registrar Hierarchy
Cisco Access Registrar’s operation and configuration is based on a set of objects. These objects are
arranged in a hierarchical structure much like the Windows 95 Registry or the UNIX directory structure.
Cisco Access Registrar’s objects can themselves contain subobjects, just as directories can contain
subdirectories.
These objects include the following:
•Radius— the root of the configuration hierarchy
•UserLists—contains individual UserLists which in turn contain users
•UserGroups—contains individual UserGroups
•Clients—contains individual Clients
•Vendors—contains individual Vendors
•Scripts—contains individual Scripts
•Services—contains individual Services
•SessionManagers—contains individual Session Managers
•ResourceManagers—contains individual Resource Managers
•Profiles—contains individual Profiles
•RemoteServers—contains individual RemoteServers
•Advanced—contains Ports, Interfaces, Reply Messages, and the Attribute dictionary.

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Chapter 2 Understanding Cisco Access Registrar
Cisco Access Registrar Hierarchy
UserLists and Groups
Cisco Access Registrar lets you organize your user community through the configuration objects
UserLists, users, and UserGroups.
•Use UserLists to group users by organization, such as Company A and Company B. Each list
contains the actual names of the users.
•Use users to store information about particular users, such as name, password, group membership,
base profile, and so on.
•Use UserGroups to group users by function, such as PPP, Telnet, or multiprotocol users. Groups
allow you to maintain common authentication and authorization requirements in one place, and have
them referenced by many users.
For more information about UserLists and UserGroups, refer to Access Registrar Server Objects in the
Cisco Access Registrar User’s Guide.
Profiles
Cisco Access Registrar uses Profiles that allow you to group RADIUS attributes to be included in an
Access-Accept packet. These attributes include values that are appropriate for a particular user class,
such as PPP or Telnet user. The user’s base profile defines the user’s attributes, which are then added to
the response as part of the authorization process.
Although you can use Group or Profile objects in a similar manner, choosing whether to use one rather
than the other depends on your site. If you require some choice in determining how to authorize or
authenticate a user session, then creating specific profiles, and specifying a group that uses a script to
choose among the profiles is more flexible. In such a situation, you might create a default group and then
write a script that selects the appropriate profile based on the specific request. The benefit to this
technique is each user can have a single entry, and use the appropriate profile depending on the way they
log in.
For more information about Profiles, refer to Access Registrar Server Objects in the Cisco Access
Registrar User’s Guide.
Scripts
Cisco Access Registrar allows you to create scripts you can execute at various points within the
processing hierarchy.
•Incoming scripts—enable you to read and set the attributes of the request packet, and set or change
the Environment dictionary variables. You can use the environment variables to control subsequent
processing, such as specifying the use of a particular authentication service.
•Outgoing scripts—enable you to modify attributes returned in the response packet.
For more information about Scripts, refer to Access Registrar Server Objects in the Cisco Access
Registrar User’s Guide.
Services
Cisco Access Registrar uses Services to let you determine how authentication, authorization, and/or
accounting are performed.