Page 291 - Cloud computing: From paradigm to operation

Framework and requirements for cloud computing 1

In the body of this Recommendation and its appendices, the words should, and may sometimes appear, in
which case they are to be interpreted, respectively, as is recommended, and can optionally. The appearance
of such phrases or keywords in an appendix or in material explicitly marked as informative are to be
interpreted as having no normative intent.

6 Introduction

Inter-cloud computing describes the interworking of cloud service providers (CSPs) in order to deliver services
for the users. Inter-cloud relationship between CSPs can be realized by using a service from the peer CSP or
by providing a service to the peer CSP.
The case where two peer CSPs interact with each other through an inter-cloud relationship is illustrated in
Figure 6-1. As shown by a pair of two arrows pointing in opposite directions in Figure 6-1, CSP A is making
use of the services provided by CSP B. In this relationship, CSP A is considered as being the primary CSP while
CSP B is the secondary CSP. Note that the reverse situation where CSP B is using the services offered by CSP
A may also exist and in such case CSP A and CSP B are involved in two inter-cloud relationships, one for
providing services to the peer CSP and the other for using the services of the peer CSP.

Inter-cloud relationship

CSP A Use service from CSP B
p s
Provide service to

p Primary CSP in the inter-cloud relationship
s Secondary CSP in the inter-cloud relationship Y.3511(14)_F6-1

Figure 6-1 – Inter-cloud relationship between peer CSPs

Figure 6-2 illustrates in a different way the inter-cloud relationship between CSP A and CSP B, i.e., CSP A uses
the service of CSP B through the application programming interface (API) provided by CSP B, shown as API
(B). Although the arrow in Figure 6-2 is only one and is shown as unidirectional from CSP A to CSP B, it should
be understood as being equivalent to the inter-cloud relationship shown in Figure 6-1, i.e., covering the "use
service from" and "provide service to" arrows in Figure 6-1.

Inter-cloud relationship

CSP A CSP B
API (B)
p s

p Primary CSP
s Secondary CSP
API (X): API provided by CSP X Y.3511(14)_F6-2

Figure 6-2 – Inter-cloud relationship using API

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