Introduction

1 Accounting on the SBC

RADIUS is an accounting, authentication, and authorization (AAA) system. In general, RADIUS servers are responsible for receiving user connection requests, authenticating users, and returning all configuration information necessary for the client to deliver service to the user. This document focuses on capturing call accounting data.

You can configure your SBC to send call accounting information to one or more RADIUS servers. This information can help you to see usage and QoS metrics, monitor traffic, and even troubleshoot your system. For more information about QoS, refer to the Admission Control and QoS chapter of the Configuration Guide.

Accounting data may also be written locally in a friendly CSV format in standard text files. You can automate systems to retrieve these files from the SBC's directories, or you can configure the SBC to SFTP the files at regular intervals to remote servers within your network.

Finally, accounting information may be relayed to servers, often in an VoLTE network, using the Rf charging interface which runs on the Diameter protocol. The SBC can output either RADIUS or Diameter based accounting information, but not both simultaneously.

Entitlement

In order to use RADIUS with your SBC, you must have the Accounting entitlement installed and activated on your system. For more information, see the Getting Started chapter of the Configuration Guide.

Accounting Features

For H.323, SIP, and calls being interworked between H.323 and SIP (IWF), you can obtain records that contain information to help you with accounting and that provide a quantitative and qualitative measurement of the call. For H.323 and SIP calls, the SBC generates one set of records; for calls requiring IWF, the SBC generates two sets of records.

You can use the RADIUS records generated by your SBC to assist you with:

Usage accounting—See the calling and called parties for a call, the protocol used, the realm the call traversed (as well as local and remote IP address and port information), and the codec used
Traffic monitoring—You can see information about the setup, connect, and disconnect times, as well as the SIP or H.323 disconnect cause
SLA monitoring—The SBC supports RADIUS attributes that provide information about jitter, latency, and loss for H.323, SIP, and calls that require interworking between H.323 and SIP
Troubleshooting—Obtain information about calls that can help you to identify and address issues with quality and how calls are setup and torn down.

RADIUS Account Server Prioritization

Especially useful for customers with multiple SBCs, the RADIUS account server prioritization feature allows you to assign a priority to each of the account servers you configure. Setting the priority for RADIUS accounting servers allows you to load balance traffic across the servers.

Without this feature, the SBC sorts RADIUS accounting servers by their IP addresses and ports. For example, if you have a pre-existing accounting server with the IP address and port combination of 10.1.31.2:1813 and then configure a new server at 10.0.3.12:2145, the new server will take priority over the pre-existing one. Of course, you always have the option of allowing the system to set the priority or your accounting servers in this way.

The prioritization feature works with all of the strategy types you set in the accounting configuration. However, it is most applicable to the hunt or failover strategies. You can assign a number to each server to mark its priority, or you can leave the priority parameter set to 0 (default) so the SBC prioritizes them by IP address and port.

ACLI Instructions

This section tells you how to access and set parameters for accounting support. To use the SBC with external RADIUS (accounting) servers to generate CDRs and provide billing services, you need to configure account configuration and one or more account servers.

Create an Account Configuration

You set the account configuration parameters to define high level accounting information. After setting initial parameters in the account-config, you must create one or more accounting-servers that define the systems where RADIUS accounting CDRs are sent.

To configure the account configuration:

Access the account-config configuration element.

ORACLE# configure terminal
ORACLE(configure)# session-router
ORACLE(session-router)# account-config
ORACLE(account-config)#

hostname—Defaults to and must remain localhost.
port—Retain the default value of 1813 or enter the number of the UDP port associated with the SBC from which RADIUS messages are sent.
- minimum: 1025
- maximum: 65535
strategy—Indicate the strategy you want used to select the accounting servers to which the SBC will send its accounting messages. The following table lists the available strategies:
- hunt—Selects accounting servers in the order in which they are listed. If the first accounting server is online, working, and has not exceeded any of the defined constraints, all traffic is sent to it. Otherwise the second accounting server is selected. If the first and second accounting servers are offline or exceed any defined constraints, the third accounting server is selected. And so on through the entire list of configured servers.
- failover—Uses the first server in the list of predefined accounting servers until a failure is received from that server. Once a failure is received, it moves to the second accounting server in the list until a failure is received. And so on through the entire list of configured servers.
- round robin—Selects each accounting server in order, distributing the selection of each accounting server evenly over time.
- fastest round trip time—Selects the accounting server that has the fastest round trip time (RTT) observed during transactions with the servers (sending a record and receiving an ACK).
- fewest pending—Selects the accounting server that has the fewest number of unacknowledged accounting messages (that are in transit to the SBC).
protocol—Retain the default value to use RADIUS accounting, or change this to diameter, for Diameter Rf charging.
state—Retain the default value enabled if you want the account configuration active on the system. Enter disabled if you do not want the account configuration active on the system.
max-msg-delay—Retain the default value of 60 seconds or indicate the length of time in seconds that you want the SBC to continue trying to send each accounting message. During this delay, the SBC can hold a generic queue of 4096 messages.
- Minimum: zero (0)
- Maximum: 4294967295
max-wait-failover—Retain the default value of 100 messages or indicate the maximum number of accounting messages the SBC can store its message waiting queue for a specific accounting server, before it is considered a failover situation.

Once this value is exceeded, the SBC attempts to send it accounting messages, including its pending messages, to the next accounting server in its configured list.
- Minimum: one (1) message
- Maximum: 4096 messages
trans-at-close—Retain the default value of disabled if you do not want to defer the transmission of message information to the close of a session. Enter enabled if you want to defer message transmission.
- disabled—The SBC transmits accounting information at the start of a session (Start), during the session (Interim), and at the close of a session (Stop). The transmitted accounting information for a single session might span a period of hours and be spread out among different storage files.
- enabled—Limits the number of files on the SBC used to store the accounting message information for one session. It is easiest to store the accounting information from a single session in a single storage file.
Type done to save your configuration.

Continue to the next section to create accounting servers.

Create Accounting Servers

You must establish the list of servers which the SBC sends accounting messages. Create the account server list to store accounting server information for the account configuration. Each account server can hold 100 accounting messages. RADIUS will not work if you do not enter one or more servers in a list.

Access the account-server configuration element.

ORACLE# configure terminal
ORACLE(configure)# session-router
ORACLE(session-router)# account-config
ORACLE(account-config)# account-server
ORACLE(account-server)#

hostname—Add the host associated with the account server as an IP address.
port—Retain the default 1813 or enter the number of the UDP port associated with the account server to which RADIUS messages are sent.
- minimum: 1025
- maximum: 65535
state—Retain the default enabled to enable the account servers on the system or enter disabled to disable them.
min-round-trip—Retain the default 250 milliseconds or indicate the minimum round trip time of an accounting message.
- minimum: 10 milliseconds
- maximum: 5000 milliseconds
A round trip consists of the following:
- The SBC sends an accounting message to the account server.
- The account server processes this message and responds back to the SBC.
If the fastest RTT is the strategy for the account configuration, the value you enter here can be used to determine an order of preference (if all the configured account servers are responding in less than their minimum RTT).
max-inactivity—Retain the default 60 seconds or indicate the length of time in seconds that you want the SBC with pending accounting messages to wait when it has not received a valid response from the target account server.
- minimum: 1 second
- maximum: 300 seconds
  
  Once this timer value is exceeded, the SBC marks the unresponsive account server as disabled in its failover scheme. When a server connection is marked as inactive, the SBC attempts to restart the connection and transfers pending messages to another queue for transmission. RADIUS messages might be moved between different account servers as servers become inactive or disabled.
restart-delay—Retain the default 30 seconds or indicate the length of time in seconds you want the SBC to wait before resending messages to a disabled account server.
- minimum: 1 second
- maximum: 300 seconds
bundle-vsa—Retain the default enabled if you want the account server to bundle the VSAs within RADIUS accounting messages. Enter disabled if you do not want the VSAs to be bundled. (Bundling means including multiple VSAs within the vendor value portion of the message.)

In a bundled accounting message, the RADIUS message type is vendor-specific, the length is determined for each individual message, and the vendor portion begins with a 4-byte identifier, and includes multiple vendor type, vendor length, and vendor value attributes.
secret—Enter the secret passed from the account server to the client in text format. Transactions between the client and the RADIUS server are authenticated by the shared secret; which is determined by the source IPv4 address of the received packet.
NAS-ID—Optional. Enter the NAS ID in text format (FQDN allowed). The account server uses this value to identify the SBC for the transmittal of accounting messages.

The remote server to which the account configuration sends messages uses at least one of two potential pieces of information for purposes of identification. The SBC accounting messages always includes in the first of these:
- Network Access Server (NAS) IP address (the IP address of the SBC’s SIP proxy)
- NAS ID (the second piece of information) provided by this value. If you enter a value here, the NAS ID is sent to the remote server.
  
  If you have more than one SBC pointing to the same account server, the NAS ID can be used to identify which SBC generated the record.
priority—Enter the number corresponding to the priority you want this account server to have in relation to the other account servers to which you send traffic. The default for this parameter is 0, meaning the prioritization feature is turned off—and that the SBC will therefore prioritize accounting servers by IP address and port.