Understanding Cloud Characteristics - Deploying and Managing a Cloud Infrastructure - page 10

There are a couple of aspects that have to be kept in mind regarding ubiquitous access:
Security Cloud tenants typically connect with the cloud provider for resource management
over the network. The most popular way is to use Secure Shell (SSH) to access your cloud
account and perform operations. Most cloud providers enable users to allow or block network
IP addresses and ports. This would not mean that the cloud provider is not offering ubiquitous
access or pseudo-ubiquitous access.
Security has become one of the top concerns within the cloud, and therefore security is
something that has to be prioritized over easy access. This wouldn't make a cloud less
ubiquitous because the vendor enables tenants to customize their access levels based on
their security concerns.
Ubiquitous Network Cloud tenants should be able to connect to the platform regardless
of how the internal network backbone is implemented within the vendor's data centers.
Every major public cloud vendor has geographically distributed data centers across con-
tinents, and tenants can provision resources in any of the available zones based on the
physical proximity of their majority user base. Access to the cloud platform for the tenants
should be abstracted from the underlying details of how the network requests would be
routed to the right data center.
Metering Resource Pooling
There are two types of cloud infrastructure offerings: bare metal and virtual (with fur-
ther divisions within virtual). With a bare metal infrastructure, the physical server would
be allocated with the same specification you placed an order for. This is popular among
scientific- and compute-based financial users because they need the performance that
bare metal would guarantee; the cloud vendor would make a commitment to not onboard
multiple tenants to the same physical servers. However, these users form a tiny subset of
the overall user base of cloud vendors, and therefore cloud offerings are not geared toward
allocating silicon instead of virtual machines. Also, on the scale of the cloud, rolling out a
bare metal offering would be complex and not only incur additional cost but also diminish
profits for the cloud vendors. This is one of the reasons Amazon does not offer bare metal
cloud instances.
Resource pooling refers to virtualizing the physical resources available in the cloud
vendor's centers. From virtual machines (VMs) to software defined networking (SDNs),
the physical layer has been totally abstracted, not only from the tenants but also from the
infrastructure and data center engineering teams within the cloud vendors.
Virtualization brings in a whole new set of challenges when it comes to metering the
resources consumed by individual tenants. Keep in mind that metering is critical to cloud
vendors' operations and commercial viability and any inaccuracy could result in massive
losses in the form of unbilled resources.