Overview
The objective of the article is to give a glance at advantages of real time billing over batch billing, principles of work of real time ISP billing systems & prepaid billing, and the outlook for real-time service accounting systems.
The author is inspired by UTM5, an excellent, powerful, flexible and affordable billing system for ISPs able to collect traffic statistics and manage access in real time. The author considers UTM5 to be a pattern of up-to-date real-time ISP billing automation and service management systems.
Introduction
Real time billing is the capability of accounting for services in real time, where all financial data is being processed instantly and therefore a client's balance is being constantly updated. Real time ISP billing is that for Internet access service accounting (and other services, like VoIP, e-mail, Web-hosting, local area network resources access, iTV). The central tool of an ISP for realizing real time accounting for access services is a billing system that is a complex of software and hardware associated with networking equipment. Real time ISP billing systems additionally may have a capability of controlling access to the services provided. This makes possible to realize prepaid billing with blocking of access to services when a subscriber exhausts his funds. Such a system is more than just a billing system.
On the contrary, batch billing systems usually process usage records (CDR or IPDR) on regularly sheduled basis. And no matter how fast is the batch process, there always exist latency problems. As a result, batch billing systems are not suitable for prepaid service accounting as subscribers may go far in the red. Providers are unable to detect if the credit limit has been reached. The only possible way to realize prepaid billing is to use a real-time billing system.
Another common drawback of batch billing systems is the revenue leakage. As usage (e.g., a phone call) is not rated immediately, and when rating occurs after a batch cycle has been complete, the call is missed and revenue is lost.
Real time billing systems are able to cope with batch processes; batch systems cannot accomodate processes when time is a factor.
How Does a Real Time ISP Billing System Work?
Internet Access Billing
For rating IP services in real time it is necessary to have a high performance accounting engine steadily collecting usage data (statistics). For Internet access service, metered for traffic usage, it can be used a sniffing server which intercepts all network packets, extracts required data form packet headers and sends statistics to the billing server. However modern networking hardware (e.g., Cisco routers) is capable to export network usage statistics in Netflow, IP accounting, or another format (sFlow, RADIUS, etc) by sending special records in packets to a specified networking device (normally via UDP protocol). Stream of these packets is accepted by a collector and then statistics is cached and analyzed by a rating engine. Using Netflow technology reveals wide possibilities for classifying network traffic (e.g., it's easy to distinguish local traffic, native Internet, foreign Internet, peering, etc). If a router is not capable to export statistics, a traffic probe can be used. There are various Netflow traffic probes for different operating systems available on the Internet (e.g., NDSAD, ipcad, etc).
Prepaid billing requires controlling access to the services provided. That is why prepaid ISP billing should be able to manage firewalls. Firewall management module is necessary for both flat rate prepaid billing and usage based billing (time usage or traffic usage).
Real Time VoIP Billing
Batch billing systems rate telephony service by parsing CDR files. This is not suitable for prepaid billing as calls are rated after they have been already made. Real time billing requires a mechanism of limitation of call duration. A billing system should be able to estimate the highest possible call duration taking into account current balance of a subscriber and cost of a call that may depend on time of a day, telephone direction, etc and send the estimated value to a device that regulates VoIP calls (usually VoIP gatekeepers play this role). To be more exact the scheme is:
1. A subscriber is attempting to make a call. The phone turns to a gatekeeper for processing the call.
2. The gatekeeper requests the billing system if the call is possible, and for the highest possible call duration.
3. The billing system gives the gatekeeper necessary parameters for the call.
4. The gatekeeper establishes connection with the called device.
5. When the call is over, the gatekeeper sends all necessary call data to the billing server.
6. The billing system makes charge for the call.
This is a so called AAA scheme (authentication, authorization, accounting). RADIUS is the most popular up-to-date standard for authorization and accounting of telephone calls (and other services).
Outlook
Nowadays ISP companies prefer using real time billing systems that are replacing traditional batch systems ineffective for Internet access and other IP services accounting. Up-to-date ISP billing systems should allow a provider to link services, tariffs, accept payments and control access in real time. As a result it can be seen a trend of moving from flat-rate billing to usage-based IP services. It is more profitable for a provider and convenient for a subscriber to rate Internet access according to the line usage (cost per MByte).
See also:
Overview of the Billing System "UTM 5"
Basic ISP Billing Solutions
