Page 292 - Cloud computing: From paradigm to operation

1 Framework and requirements for cloud computing

7 Patterns of inter-cloud

This clause introduces three patterns of inter-cloud for describing relations and interactions involving
multiple CSPs, i.e.,:
– The inter-cloud peering;
– The inter-cloud federation;
– The inter-cloud intermediary.

7.1 Inter-cloud peering

In inter-cloud peering, two CSPs interwork directly with each other in order to use the services provided by
the peer CSP.

NOTE 1 – Inter-cloud peering does not necessarily imply reciprocal relationships in terms of service use and service
providing between the two CSPs.
NOTE 2 – Inter-cloud peering is a fundamental pattern, which may exist on its own or can be used in the two patterns
described in clauses 7.2 (inter-cloud federation) and 7.3 (inter-cloud intermediary).

In inter-cloud peering, each CSP exposes its own API for cloud interworking and the CSPs interwork with each
other directly by using the other CSP's API. As shown in Figure 7-1, CSP A interworks with CSP B using the API
provided by CSP B and vice versa. Since the inter-cloud peering pattern can be used in the other pattern
described in clauses 7.2 and 7.3, use of a common API between CSP A and CSP B is not precluded
(see Figure 7-2).

Inter-cloud peering

CSC 1 Service X
p API (B) s
CSP A API (A) CSP B
Service Y s p
CSC 2
Y.3511(14)_F7-1
p Primary CSP
s Secondary CSP
API (X): API provided by CSP X

Figure 7-1 – Inter-cloud peering

As shown in Figure 7-1, the inter-cloud peering pattern consists of two inter-cloud relationships, CSP A to CSP
B relationship and CSP B to CSP A relationship. CSP A is a primary CSP when using the services of CSP B
provided by API (B) for providing services to its own customers (CSC1 and CSC2) and is also a secondary CSP
when providing services to CSP B through its own API (A).

Inter-cloud peering

CSC 1 Service X
p s
CSP A Common API CSP B
Service Y s p
CSC 2

Y.3511(14)_F7-2
p Primary CSP
s Secondary CSP

Figure 7-2 – Common API in the peering pattern

Figure 7-2 illustrates the case where a common API is used between CSP A and CSP B, i.e., API (A) and API (B)
in Figure 7-1 are the same.

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