Enterprise Service Bus (ESB) - Guide to Cloud Computing for Business and Technology Managers - page 205

Typical examples are an online reservation system, which interacts
with the user as well as various service providers (airline ticketing,
insurance claims, mortgage and credit product applications, etc.).
In addition, in order to be successful in business environments, it
is extremely important that the ESB provides certain transactional
guarantees. More specifically, the ESB needs to be able to ensure that
complex transactions are handled in a highly reliable manner, and if
failure should occur, transactions should be capable of rolling back
processing to the original, prerequest state. Long-duration transac-
tional conversations could be made possible if implemented on the
basis of messaging patterns using asynchrony, store and forward,
and itinerary-based routing techniques. It should be noted that the
base definition of an ESB as currently used by the ESB analyst and
vendor community does not mandate a long-duration transaction
manager.
8. Security capabilities : Generically handling and enforcing security is
a key success factor for ESB implementations. The ESB needs both
to provide a security model to service consumers and to integrate
with the (potentially varied) security models of service providers.
Both point-to-point (e.g., SSL encryption) and end-to-end security
capabilities will be required. These end-to-end security capabilities
include federated authentication, which intercepts service requests
and adds the appropriate user name and credentials, validation of
each service request and authorization to make sure that the sender
has the appropriate privilege to access the service, and, lastly,
encryption/decryption of XML content at the element level for both
message requests and responses. To address these intricate security
requirements, the ESB must rely on WS-Security and other security-
related standards for Web Services that have been developed.
9. Integration capabilities : To support SOA in a heterogeneous environ-
ment, the ESB needs to integrate with a variety of systems that do
not directly support service-style interactions. These may include
legacy systems, packaged applications, or other EAI technologies.
When assessing the integration requirements for ESB, several types
or styles of integration must be considered, for example, process ver-
sus data integration.
10. Management and monitoring capabilities : In an SOA environment,
applications cross system (and even organizational) boundaries, they
overlap, and they can change over time. Managing these applications
is a serious challenge. Examples include dynamic load balancing,
failover when primary systems go down, and achieving topological
or geographic affinity between the client and the service instance.
Effective systems and application management in an ESB requires
a management framework that is consistent across an increasingly