Page 636 - Cloud computing: From paradigm to operation

3 XaaS

Pre-conditions – There is no connectivity between XaaS CSC A and XaaS CSP Y.
(optional) – There is no connectivity between XaaS CSP X and XaaS CSP Y.
– Either XaaS CSC A or XaaS CSP Y requests the connectivity between them with their end-
point identifiers and associated characteristics (referring to QoS and security aspects)
for the connectivity.
– Either XaaS CSP X or XaaS CSP Y requests the connectivity between them with their end-
point identifiers and associated characteristics (referring to QoS and security aspects)
for the connectivity.
Post-conditions – XaaS CSC A and XaaS CSP Y can communicate with each other.
(optional) – XaaS CSP X and XaaS CSP Y can communicate with each other.
Requirements – On-demand network configuration
– Heterogeneous networks compatibility
– QoS-guaranteed connectivity
– Secured connectivity
– Common control mechanism for NaaS connectivity (refer to clause 9.1)
NOTE – The first 4 requirements belong to general requirements of NaaS which are
provided in [ITU-T Y.3501].

II.4.2 Detailed use cases
II.4.2.1 NaaS connectivity use case for dynamic transport network

Title NaaS connectivity use case for dynamic transport network
Description CSC demands a geographically distributed connectivity service and dynamic traffic capacity
which can accommodate cloud bursting (e.g., VM migration or the transfer of large data
files across data centres which sit in different places) which brings a surge of traffic passing
through the backbone of the CSP.
IP and transport networks of the CSP are separately managed and therefore cannot
provide the common control mechanism for dynamic bandwidth adjustment. In order to
guarantee the service continuity and consistent SLA to the CSC, such CSP would have to
offer over-provisioning of links, most of which being not used effectively and thus causing
resource waste.
The CSP is recommended to cope with the surge of transit traffic which traverses its
backbone without making use of traditional over-provisioning approaches of the
networking resources.
Roles CSC, CSP

Figure
(optional)
Pre-conditions
(optional)
Post-conditions
(optional)
Derived – Unified SLA for multiple optimized networks (refer to clause 9.2)
requirements – Leveraging transport networks dynamically (refer to clause 9.3)
– Unified network control mechanism (refer to clause 9.4)

II.4.2.2 NaaS connectivity use case for flexible and extended VPN

Title NaaS connectivity use case for flexible and extended VPN
Description The different VPN sites are connected via BGP/MPLS IPVPN. The processing resources and
the corresponding subnet are migrated from the CSC's data centre to the CSP's data centre,
which is not yet involved in the VPN as a VPN site. In order to add this new site in the

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