Network Design and Implementation

Network Design and Implementation

Article is on Strategies and methods used to systematically setup Network Design and Implementation, such as the hierarchical network design model and the Cisco enterprise architecture.
As a company grows, its network requirements also increase. Companies rely on network infrastructure to provide essential services. Network interruptions can cause profit and customer losses. Network designers must design and build a business network that is scalable and highly available .
Companies are increasingly turning to their network infrastructure to provide mission-critical services. As companies grow and evolve, they hire more employees, open branches and expand to global markets. These changes directly affect the network requirements. The network used to support the business activities of the company is called the business network .
A business network must support the exchange of various types of network traffic, including data files, email, IP telephony and video applications for various business units.
Table of Contents

1. Commercial Devices for Companies
2. Hierarchical Network Design
3. Cisco Enterprise Architecture
4. Failure domains

Commercial Devices For Companies

Users expect business networks, such as the one shown in Image 2, to be active 99.999% of the time. The interruptions that occur in business networks prevent companies from carrying out their normal activities, which can lead to loss of profits, customers, data and opportunities.

In order to reach this level of reliability, advanced technology equipment of enterprise class is usually installed in the business network. Business teams, designed and manufactured to meet stricter standards than cheaper devices, carry a large volume of network traffic.
High-tech equipment is designed to be reliable, with features such as redundant power supplies and migration capacity in case of failures. Failover capability is the ability of a device to move from a module, service or device that does not work to one that does without interrupting the service or with minimal interruption.

Hierarchical Network Design

To optimize bandwidth in an enterprise network, the network must be organized so that traffic is maintained at the local level and does not spread unnecessarily to other parts of the network. The use of the three-layer hierarchical design model helps to organize the network.

In above figure, in this model the functionality of the network is divided into three different layers.

1. Access layer
2. Distribution layer
3. Core layer

Each layer is designed to fulfill specific functions.
The access layer provides connectivity to users. The distribution layer is used to send traffic from one local network to another. Finally, the core layer represents a high-speed backbone between the dispersed networks. User traffic starts at the access layer and passes through the other layers if you need to use the functionality of those layers.

Although the hierarchical model consists of three layers, a two-tier hierarchical design may be implemented in some small business networks. As shown in Image 4, in a two-tier hierarchical design , the core and distribution layers are combined into one, which reduces cost and complexity.

Cisco Enterprise Architecture

The Cisco enterprise architecture divides the network into functional components , while maintaining the core, distribution and access layers.

As shown in Image 5, the main modules of the Cisco enterprise architecture include the following:

1. Business campus
2. Business perimeter
3. Perimeter of the service provider
4. Remote

 Business campus

The business campus module is composed of all the campus infrastructure and includes the access, distribution and core layers.

• The access layer module includes layer 2 or layer 3 switches to provide the required port density. In this module, the implementation of VLANs and trunk links to the building's distribution layer occurs. Redundancy to building distribution switches is important.
• The distribution layer module adds access to the building through layer 3 devices. In the distribution layer module, routing, access control and QoS are carried out.
• The core layer module provides high-speed inter connectivity between the distribution layer modules, the data center server farms and the business perimeter. In this module, the central axis of the design is redundancy, rapid convergence and fault tolerance.

In addition to these modules, the business campus may include other sub-modules, such as the following:
Data center and server farm module : this area provides high speed connectivity and protection for servers. It is very important to provide security, redundancy and fault tolerance.
Services module : this area provides access to all services, such as IP telephony services, wireless controller services and unified services.

Business perimeter

The business perimeter module is composed of the Internet, VPN and WAN modules that connect the company to the service provider's network. This module extends the company's services to remote sites and allows the company to use Internet and partner resources. Provides QoS, policy reinforcement, service levels and security.

Perimeter of the service provider

The perimeter module of the service provider provides Internet, public switched telephone network (PSTN) and WAN services .
The composite business network (ECNM) model passes through an end device. This is the moment in which the packages can be analyzed and the decision can be made as to whether they should be allowed to enter the business network. Intrusion detection systems (IDS) and intrusion prevention systems (IPS) can also be configured on the business perimeter to provide protection against malicious activities.

Failure domains

A well-designed network not only controls traffic, but also limits the size of fault domains . A fault domain is the area of ​​the network that is affected when an essential device or network service experiences problems.
The function of the device that initially fails determines the impact of the fault domain. For example, a switch that malfunctions in a network segment usually affects only the hosts in that segment. However, if the fault occurs in the router that connects this segment with other segments, the impact is much greater.
The use of redundant links and reliable high-tech equipment minimizes the chances of interruptions to network services. If the domains of failures are smaller, the impact of the failures on the productivity of the company is reduced. In addition, they simplify the problem-solving process, which reduces downtime for all users.

Limitation of fault domain size

Since a failure in the core layer of a network can have a great impact, the network designer often focuses on efforts to prevent failures. These efforts can lead to a large increase in the cost of network implementation. In the hierarchical design model, it is easier and generally more economical to control the size of a fault domain in the distribution layer. In this layer, network errors can be contained in a smaller area, so that fewer users are affected. When layer 3 devices are used in the distribution layer, each router functions as a gateway for a limited number of users in the access layer.

Implementation of a switch block

Routers, or multilayer switches, are generally implemented in pairs, and access layer switches are divided equally between them. This configuration is called " building switch block " or "department". Each block of switches works independently. As a result, the failure of a single device does not deactivate the network. Not even the failure of a whole block of switches affects a large number of end users.