1. There are several integration topologies that can be used depending on the number and nature of components that need to be connected, including point-to-point connection, broker, message bus, and publish/subscribe. 2. A point-to-point connection involves direct connections between all systems, requiring each system to implement logic for data translation. As the number of connections grows, this approach has high operational costs. 3. A broker decouples source and target systems by providing routing and transformation services. This reduces duplication and configuration costs compared to point-to-point. Common broker examples include message brokers, direct brokers, and indirect brokers.

1. 1
Systems Integration
Lecture 4

2. 2
Integration Topologies

3. 3
Intro
 System integration is multifaceted and can be
approached through different architectural
models, depending on the number and nature of
components that need to be connected.
– Point-to-Point Connection
– The Broker (and its variants)
– Message Bus.
– Publish/Subscribe

4. 4
Point – to – Point Integration (P2P)
 P2P is the architectural pattern in which every system is
directly connected to all other systems and apps it needs to
work in tandem and share information with.
 This model can be realized via APIs, webhooks, or custom
code.
 With a P2P connection, data is extracted from one system,
modified or formatted, and then sent to another system.
 Each application implements all the logic for data
translation, transformation, and routing, taking into account
the protocols and supported data models of other integrated
components.

5. 5

6. 6
P2P
 With P2P as the size of your integration network grows and
as the frequency of change increases, the operational cost
associated with this approach becomes significant.
 Major advantage of the Point-to-Point Connection pattern
is simplicity of implementation.
 The weakness of the Point-to-Point Connection pattern is
the duplication of transformation and routing code between
systems, and the high configuration cost of endpoint
address changes.
 To minimize these weaknesses, you can add another layer
of indirection between endpoints that contains a broker.

7. P2P: When to use it
 Say, to interconnect six modules you need to
perform 15 integrations. This results in the
so-called star/spaghetti integration.
 This approach suits companies that don’t
have complex business logic and run their
operations on just a few software modules. It
is also a perfect option for businesses aiming
at connecting to SaaS applications.
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8. Broker
 The Broker pattern and its variants are often used in both application
design and integration design.
 The intent of a broker is to decouple source systems from target
systems.
 In the context of Distributed Object Integration, the source system may
send a marshaled set of parameters when the source system requests a
method invocation from the target system.
 In the context of Service-Oriented Integration, the source system may
send a message that requests a service from a target system. While the
contexts vary significantly, both use a Broker pattern to decouple the
source systems and the target systems.
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9. Broker
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 There are three responsibilities that are involved in
communication as follows:
 Routing. Routing involves determining the location of a
target system, and it is performed by using direct and indirect
communication.
 Endpoint registration. Endpoint registration is the
mechanism that a system can use to register itself with the
Broker so that other systems can discover that system.
 Transformation. Transformation is the process where an
element is converted from one format to another.

10. Broker
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11. Broker
 A Direct broker establishes initial communication between endpoints.
After the initial communication, the two endpoints communicate
directly by using client-side and server-side Proxies.
 The Indirect broker behaves like a middleman such that all the
communication between endpoints passes through it. Using an
indirect broker allows a sender to be unaware of target details and
provides central control of the message flow. In this way, Indirect
Broker is similar to Mediator.
– While the Indirect Broker pattern is useful when you need to
control communications, Direct Broker offers better
performance, especially when an additional intermediary is
not needed for all communications.
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12. Broker: Message Broker
 A Message Broker communicates exclusively by using
messages and indirect communication. The Message
Broker is an important and frequently used integration
pattern. It is often referred to as a Hub-and-Spoke
architecture.
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13. Hub – and – Spoke
 The hub-and-spoke model is a more advanced type of
integration architecture that addresses the issues of point-
to-point. The connections between all subsystems are
handled by a central hub (message broker), so they don’t
communicate with each other directly.
 The hub serves as a message-oriented middleware with a
centralized integration engine to translate operations into a
single canonical language and route messages to the right
destinations. The spokes (adapters) connecting the hub to
the subsystems are managed individually.
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14. Hub – and – Spoke
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15. Hub – and – Spoke
 Pros and cons: Since every system has only one connection to the
central hub, things get better in terms of security and architecture
simplicity.
 However, the centralization of the hub can be a weakness in such a
model. The whole infrastructure is dependent on the single
integration engine which can become the key bottleneck as the
workload increases.
 When to use it: The hub-and-spoke model is widely-used in e-
commerce, financial operations, and payment processing. Besides,
it’s a preferable architecture for highly regulated industries that face
significant security risks.
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16. Broker examples
 Five examples of the Broker pattern:
– Microsoft Distributed Common Object Model (DCOM)
– Microsoft .NET Framework Remoting
– Common Object Request Broker Architecture (CORBA)
– Universal Description Discovery and Integration (UDDI)
– Microsoft BizTalk Server 2004
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17. Message Bus
 A Message Bus provide a common communication
mechanism between disparate systems.
 To provide this common mechanism, the systems must have
three elements:
– A set of agreed-upon message schemas
– A set of common command messages
– A shared infrastructure for sending bus messages to recipients
 This shared infrastructure can be achieved either by using a
Message Router or by using a Publish/Subscribe
mechanism.
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18. Message Bus
 The Publish/Subscribe pattern describes a collaboration
where one system subscribes to change messages or to
event messages that are produced by another system.
 In the Message Bus context, a system can subscribe to
bus messages. After the system subscribes, the system is
then sent all the messages that are addressed to this
common bus.
 Although message buses often use Publish/Subscribe
implementations, these implementations are used by
other topologies as well.
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19. Message Bus
 The advantage of a message bus is that once it is established,
the cost of adding new applications is minimal. A new
application can subscribe to bus messages without affecting
other subscribers.
 The disadvantage of a message bus is the significant amount of
work that is involved in creating common message schemas,
command messages, and shared infrastructure within an
enterprise.
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20. Publish/Subscribe
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 Publish/Subscribe pattern helps keep cooperating
systems synchronized by one-way propagation of
messages because one publisher sends a message to
any number of intended subscribers.
 However, there are significant differences in the next
level of design within the pattern.
 These differences lead to three refinements of the
Publish/Subscribe pattern:
– List-Based Publish/Subscribe,
– Broadcast-Based Publish/Subscribe, and
– Content-Based Publish/Subscribe.