resources are provided to users on request and the bills are generated on the
basis of resources actually consumed. Therefore, during periods of low demand,
the idle resources may cause financial loss to
Cloud Providers (CPs). While in peak load, user’s request may be rejected due
to insufficient resources. To manage
this issue of under or over provisioning of resources, different CPs may
voluntarily unite and efficiently utilize the resources in accordance with some
agreement among them, thus creating a Federation of Clouds. Accounting and
Billing of resources in such an environment is an important issue as inappropriate
calculation of bills may either cause loss to CPs due to undercharging or to users
by overcharging them. Taking this into consideration, this paper aims: To
perform a literature review of the existing accounting and billing solutions in
single CP and Federated Cloud Environment and; Identify the requirements and limitations
of the existing accounting and billing methods so as to justify and support the
need of a new framework for Accounting and Billing of infrastructural resources
in Federation of Clouds.
Keywords: Cloud Computing, Federation,
Cloud Computing (CC) is an established paradigm which provides
convenient, on demand network access to a shared pool of configurable computing
resources (e.g., networks, servers, storage, applications, and services) that
can be rapidly provisioned and released with minimal management effort or
service provider interaction 1. Its features like no upfront investment, low operating
cost, high scalability, easy access, reduced business and maintenance risk etc.
2 make it a much better option to use than traditional data centres 3.
In a standard CC model, resources of Cloud Providers (CPs) are shared
among different customers. This introduces many challenges 4. In case of
shortage of resources, either customer’s requests are denied or low priority services
that were already running on the system, are cancelled. This results in loss of
revenue from some services, apart from a loss of reputation and therefore a
loss of future customers 5. Relying on a single Cloud’s data centres also
makes it hard to implement adequate responsiveness and usability to clients
distributed worldwide. All these problems generate the requirement of
interconnecting Clouds i.e. creating Federation of Clouds. Cloud Federation
will allow sharing of resources among different CPs and thus help achieve
better Quality of Service (QoS), reliability and flexibility 4.
federated cloud environment, different Cloud Service Providers (CSPs) are
involved, each having its own different mechanism to charge customers for the
resources consumed. Appropriate accounting and billing of cloud resources in such
an environment is essential for both CSPs as well as customers and is a major area of concern 6. Presence of resources of different CSPs
may cause one to bear the cost of another if accounting is not properly done.
It may also cause the customer to pay more if bills are not calculated properly.
there is a need to gain insight into the work done in this area of research. Till
now, no systematic literature review has been performed
for accounting and billing of resources in
Cloud Federation or single CP environment that can
summarize the work done so far in this particular area of research. Taking this
into consideration, this paper reviews the existing literature of accounting
and billing in both Single CP and Federated Cloud environment and identifies
the requirements and limitations of current solutions. The limitations are
further analysed to identify the need of a new framework for accounting and billing in a Federation of Clouds.
The paper is structured as follows. Section 2 gives the
background and motivation for selecting accounting and billing for research. Section
3 highlights the review method. Accounting and Billing and its existing
solutions in CC and Cloud Federation are discussed in
Section 4. Requirements of Accounting and Billing are mentioned in Section 5. Limitations
of existing solutions are discussed in Section 6. Section 7 concludes
Background and Motivation
current scenario, actual usage patterns of many real-world application services
vary with time, most of the time in unpredictable ways e.g. Social networks
such as Facebook and MySpace are popular Web 2.0 based applications. They serve
dynamic content to millions of users, whose access and interaction patterns are
hard to predict. Load spikes can take place at different locations at any time
7. At present, no single hosting company can create a seemingly infinite
infrastructure capable to serve such applications and the increasing number of
on-line services, each having massive amounts of users and access at all times,
from all locations 8. To cater to such needs, it is required that workloads
and data from one CP can be easily moved to another or between private and
public Clouds 9 i.e. interconnection of Clouds is required. One way of doing
this is to create Federation of Clouds.
2.1 Cloud Federation
a concept of service aggregation characterized by interoperability features,
which addresses the vendor lock-in and provider integration problem 9. Interoperability feature allows users to move easily to different CPs,
if and when required. It also enables CPs to exchange and share resources in an
efficient manner thus solving the problem of under or over provisioning of
whole, Cloud Federation provides following benefits:
It is a
cost-efficient alternative to over dimensioning the amount of servers in order
to cope with peak loads.
resources are made available to other sites during periods of lower load thus
providing an extra source of income to CPs.
interoperability among different CPs thus solving vendor lock-in problem 1.
Though Cloud Federation provides many
benefits but some problems are associated with it. In 11, different issues
related to Cloud Federation have been discussed:
Portability (Virtual Machine (VM) Mobility, VM and Data Portability)
Service Level Agreement (SLA) (Federated SLA Management, Federation Level
Agreement, SLA Monitoring and Dependency, Legal Issues)
Security (Trust, Authorization and Identity Management,
Federated Policy and Semantic Interoperability)
Economy (Market, Pricing, Accounting and Billing) etc.
paper, the focus is on accounting and billing issue.
Accounting systems are responsible for tracking
service consumptions, charging customers for their usage and generating
revenues for their providers 12. Currently, lack of a fair and transparent
process of accounting and billing is one of the main reasons for hindering organizations
from embracing Cloud.
The process of accounting and billing of cloud resources also involves
some issues which are discussed below. These
issues create the requirement of studying and exploring this area of research in
Related to customers
It is difficult for customers
to reason about the expenses of their application due to the black-box and dynamic nature of the cloud
infrastructure. They have little or no visibility into the infrastructure.
CPs resources are shared. This may cause providers to incorrectly attribute
resource consumption to customers.
many shared resources that cannot be perfectly isolated and this can result in
unforeseen externalities that may inflate an application’s resource footprint 13.
Related to CPs
of CPs is not clear. This is because; it is difficult for CPs to precisely
monitor their own resource consumption and bill their customers’. As a result, some resources that are
difficult to monitor and attribute to client computations are not accounted
for, resulting in low revenue generation.
resources imposes costs that are challenging to measure. Consequently,
providers may incorrectly account for these costs, thereby, implicitly bearing
additional costs and increasing their own operating expenses and thus, reducing
their cost-effectiveness 13.
These issues can be solved with the help of appropriate accounting and
billing mechanisms that will provide following benefits with respect to the above
Customers related benefits
customers in making sense of the cost footprint of their outsourced computation
CP related benefits
estimating their Return on Investment.
CPs from losing revenue due to undercharging 6.
As a whole, availability of appropriate accounting and
billing mechanisms will encourage more customers to adopt
clouds thereby reducing their infrastructural investment cost and enabling them
to avail Cloud environment related other benefits. It will also be beneficial
for CPs as their infrastructure utilization will be increased and their profit
margins will improve 13.
the above discussion, accounting
and billing of cloud resources may be justified as a
suitable area for further research.