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
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.