This chapter highlights how accounting and performance management technologies can be used for billing.
Merriam-Webster's Online Dictionary defines the term billing as the "total amount of business or investments within a given period." In the world of information technology, billing can be defined as the process in which a provider of a service creates an invoice to a customer, related to the usage of that service. In this case, a service provider can be a corporation that delivers internal services to employees, an ISP offering Internet access, a data center operator delivering hosting services, and others. A simple definition of billing is "Creating an invoice related to the use of infrastructure and services."
The focus of this chapter is billing from the network infrastructure perspective (Layer 3 services). Therefore, application server-based billing is not covered in detail, because it requires different account mechanisms.
The rating function at the billing application transforms accounting records into billing records. A monetary tariff is applied to the data volume, duration, and type and quality of service. The major difference between accounting and billing is that accounting collects the usage details (also known as metering), and billing applies the tariffs. Note that the tariffs applied may also depend on the particular customer. This means that the same accounting records may result in different bills, depending on what pricing scheme and tariff are applied.
Therefore, network elements always collect accounting records, not billing records.
Chapter 1, "Understanding the Need for Accounting and Performance Management," describes the relationship between accounting and billing in more detail. The focus of this chapter is applying the technologies and products associated with accounting and performance management.
Figure 17-1 shows the network blueprint for the billing use case. Multiple billing scenarios are shown:
ISP 1 delivers Internet access to Company A (Sites 1 and 2) and Company B (Site 2).
ISP 1 and ISP 2 have a peering agreement.
ISP 2 offers wireless access at public sites, such as at airport lounges or cafes.
ISP 2 also provides dial-in access and broadband services to private users.
ISP 2 supplies Internet connectivity services to Company B's Site 1.
Company A charges departments for Internet usage, but intranet access is free.
This figure also demonstrates that ISPs need to exchange traffic with each other. An example is Company B's VPN service that spans both ISPs. This situation occurs if ISP 1 is not present at Company B's Site 1 or Company B chooses two ISPs for redundancy purposes. The described situation is a simplified scenario; it gets more complex if inter-provider QoS or MPLS services across multiple ISPs are considered.
In addition to Internet access, ISP 1 offers accounting services to Company A. The accounting records distinguish user traffic within the intranet from traffic to the Internet. The billing records are provided in two groups: an aggregated total amount of traffic for intranet services and a detailed list for Internet access.
From a technology perspective, the ISPs might use different metering techniques:
ISP 1 implements NetFlow services at the provider edge (PE) routers.
ISP 2 uses Interface MIBs at the PE routers to meter the total amount of traffic both from Company B and at the peering point to ISP 1.
In addition, ISP 2 deploys access servers for dial-in, a AAA server for wireless access connectivity, and the Cisco Service-Selection Gateway (SSG) for end-user access to video on demand (VoD) and other services.