NETWORK DESIGN CONCEPT

NETWORK REQUIREMENTS


~ Stay up all the time

~reliably deliver applications

~provide reasonable response times

~Should be secure

~ easy to modify to adapt to network growth

~ easy to troubleshooting

~ finding and fixing a problem not to be time consuming

~ Ease of management

Application Response Time

Fast recovery

Fast Troubleshooting

NETWORK DESIGN GOAL

Scalability

Manageability

Availability

Security

network can grow to include new user groups and remote sites

support new applications without impacting the level of service delivered to existing users

network can delivers consistent, reliable performance, ~ 24 hours a day,
~ 7 days a week

the failure of a single link or piece of equipment should not significantly
impact network performance.

Security is a feature that must be designed into the network, not added on after the
network is complete

Planning the location of security devices, filters, and firewall features is critical
to safeguarding network resources

The available network staff must be able to manage and support the network.


A network that is too complex or difficult to maintain cannot function effectively and efficiently.

Architecture Of Flat Network Design

A flat network topology, is adequate for small networks and is implemented using Layer 2 switching.

This is no hierarchy with a flat network design, and because each network device within the topology

is performing the same job, a flat network design can be easy to implement and manage.

The flat network topology is not divided into layers or modules and can make troubleshooting and

isolating of network faults a bit more challenging than in a hierarchical network.

In a small network, this might not necessarily be an issue, as long as the network stays small and manageable

Screenshot (1732)

Advantages of hierarchical network design
vs. flat network design

Hierarchical networks have advantages over flat network designs.

The benefit of dividing a flat network into smaller, more manageable hierarchical blocks is that local traffic remains local.

Only traffic destined for other networks is moved to a higher layer.

Layer 2 devices in a flat network provide little opportunity to control broadcasts or to filter

undesirable traffic. As more devices and applications are added to a flat network, response times

degrade until the network becomes unusable

Three-layer hierarchical network design

The networks are
organized in a layers. The hierarchical design model has three basic layers

Core layer: Connects distribution layer devices.

Distribution layer: Interconnects the smaller local networks (LANs)

Access layer: Provides connectivity for network hosts and end devices

The Cisco Enterprise Architectures

Used to further divide the three-layer hierarchical design into modular areas.

Modules represent areas that have different physical or logical connectivity.

Three areas of focus in modular network design :

Enterprise campus: Contains the network elements required for independent operation within a single campusor branch location. This is where the building access, building distribution and campus core are located

Server farm: A component of the enterprise campus, the data centre server farm protects the server resources and provides redundant, reliable high-speed connectivity.

Enterprise edge: This area filters traffic from the external resources and routes it into the enterprise network. It contains all the elements required for efficient and secure communication between the enterprise campus and
remote locations, remote users, and the Internet.

Methodology

STEP 1

STEP 2

STEP 3

Network designer and customer/client,document the goals of the project.

Business goals:Focus on how the network can make the business more successful

Technical Requirement:Focus on how the technology is implemented within the network

Information about the current network and
services is gathered and analysed.

compare the functionally of the existing network with the defined goals of the new project

The designer determines whether any existing equipment ,infrastructure,and protocols can be reused, and what new equipment and protocols are needed to complete the design

A common strategy for network design is ti take a top-down approach

whem the design is complete, a prototype or proof-of -concept test is performed

Cisco Lifecycle Services

Designed to support evolving networks.

A six-phase approach (PPDIOO).

Each phase includes the activities required to successfully deploy and operate Cisco technologies.

It specifies how to maximise performance throughout the lifecycle of a network.

SIX phases – Prepare, Plan, Design, Implement, Operate & Optimise.

PPDIOO Phases

The Prepare phase:

Establish the organisational requirements

Develop a network strategy

Propose a high-level conceptual architecture with best-suited technologies

Also establish a financial justification for network strategy by assessing the business case for the proposed architecture.

The Plan phase:

Identify initial network requirements based on goals, facilities, user needs, and so on.

Characterise sites and assess any existing networks.

A project plan is useful to help manage the tasks, responsibilities, critical milestones, and resources required to implement changes to the network

The project plan should align with the scope, cost, and resource parameters established in the original business requirement

The Design phase:

The initial requirements from the Plan phase leads the activities of the network design specialists.

Support availability, reliability, security, scalability, and manageability

The Implement phase:

Network is built, or additional components are included as in the design specifications.

Integrate devices without disturbing the existing network or creating points of vulnerability

The Operate phase:

Final test of the appropriateness of the design.

Maintains network health in daily operations, includes high availability and reducing expenses.

The Optimize phase:

▪ Involves proactive management of the network.

▪ Proactive management is to identify and resolve issues before they affect the organization.

▪ May prompt a recommendation for network redesign.

▪ Redesign may be necessary if too many network problems and errors occur.

Approaches for network design

TOP DOWN

adapts the network infrastructure to the needs of the organisation.

• clarifies the design goals and initiates the design from the perspective of the required applications and network

solutions, such as IP telephony, content networking, and video conferencing.

• The PPDIOO methodology uses the top-down approach.

BOTTOM-UP

A common approach but not recommended.

• The network designer selects network devices and technologies based on previous experience rather than prior

understanding of the organisation.

• Does not include information on the business goals, the proposed network design may not be able to support the required

applications.