Network Design - Internet Engineering - Lecture Slides, Slides of Internet and Information Access

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Internet Engineering Course

Network Design

Contents

• Define and analyse an organization network

requirements

• Discuss about the appropriate solutions
  • Identify important factors in network design
  • Find appropriate structure

Small sized Network (<80 users)

• Low budget for IT expense
• Little expertise in various technologies
• Mostly off the shelf applications
  • Low bandwidth consumption
• Mostly basic requirements, such as email, word

processing, printing and file sharing

• One or two administrators
  • Responsible for every aspects of network (generalist)
  • Server management, backup tasks, connecting new devices, installation of workstations and troubleshooting PC problems

Requirements for SSN

• Low cost equipment
• Shared bandwidth for most users, switched for a

selective few

• A central switch acting as a backbone
• Flat network design
• Little fault tolerance
• Minimal management required
• High growth provisioning of 20-50%

Connectivity design

• The aim is to have a design that is both cost effective and provisioned for future expansion
• There is a server room with all the connecting devices and servers
• The printers are fitted with built in Ethernet ports distributed in the building
• There are two groups of users, power users group and non power users
• Power group need to print a lot of documentation, take large documents from server or save presentation files into the server

Connectivity design (cont.)

• Non power users do more manual tasks such

as answering phone calls

• They use the network mainly for reading

emails and do some simple word processing

• They use low-end PCs

Physical diagram – expansion plan

Logical network design

Addressing and Naming

• For this size of network a Class C address should be used.
• A private Class C address is used: 192.168.1.0 to 192.168.1.
• Dynamic or Static IP assignment?
  • It might be hard and maintain a DHCP server
  • Therefore for small sized network we may decide to use static IPs.
• How about a DNS server?
  • Again setting and maintaining a DNS for this size of network may not be beneficial
  • Therefore a simple naming scheme maybe used

Connecting the network to the

Internet

• In the design we used private IP addresses:
  • Computers can’t use Internet directly, there is a need for NAT functionality
  • There exists the advantage of security of network
• It is decided to use a router with built-in NAT

functionality

• It is not cost effective to host email and Web service

inside the organization

• Therefore such servers are outsourced

A sample firm

• Connecting 300 users to a network
• The company has a AS/400 host and 8 Windows NT file servers
• There are 6 departments in the company, each with its own applications: - Marketing – mainly email with external customers, calendaring, word processing, presentation applications - Customer support – mainly handling customer queries, accessing the host for in-house developed applications - MIS – development of applications on AS/ - Human Resources – Mainly word processing - Engineering – make use of CAD/CAM workstations

Connectivity design

• Power users, such as the Engineering department, will have 100 Mbps switched connections to the desktop
• Because Marketing users deal with graphics presentation, they will be connected to the 10 Mbps switch in a ratio of 16 users to a switch.
• Since Customer Support and Human Resources users require fewer computing resources, they are connected to the 10 Mbps switch in a ratio of 24 to a switch.
• Except for the server in the Engineering department, all the servers are
• connected to the backbone switch at 100 Mbps. The engineering server is connected to the switch in the Engineering department at 100 Mbps.

Logical network design

Logical network design (cont.)

• With a network of this size it is beneficial to

have a DHCP server

• Also it is better to have a DNS for name

resolution: