This document discusses how network design should consider application requirements and traffic flows. It identifies the main types of application communication and how to characterize applications. Key factors that affect network design are internal and external traffic patterns, hardware capabilities, and quality of service implementation. Specific application categories like voice/video, file transfer, and web traffic are examined for their network impacts. The document emphasizes documenting application network needs through diagrams of traffic flows within the local network and to remote sites.

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Identifying Application
Impacts on Network
Design
Designing and Supporting Computer Networks – Chapter 4

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Objectives
 Explain how applications and traffic flow can affect the
design of the network
 Identify application impacts on network design
 Explain how Quality of Service is implemented on the
LAN/WAN
 Explain the options for supporting voice and video
traffic on the network
 Document the network requirements of specific
categories of applications and diagram the application
traffic flows through the network

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Explain How Applications and Traffic
Flow Can Affect the Network Design
 Application performance depends on availability and
responsiveness
 Measurement: user satisfaction, throughput, technical
metrics

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Explain How Applications and Traffic
Flow Can Affect the Network Design
Four main types of application communication:
 Client-to-client
 Client-to-distributed server
 Client-to-server farm
 Client-to-enterprise edge

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Characterize applications by gathering information:
 Organizational output
 Network audit
 Traffic analysis
Explain How Applications and Traffic
Flow Can Affect the Network Design

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Explain How Applications and Traffic
Flow Can Affect the Network Design
 Internal traffic: identify areas where high bandwidth is
needed, and possible bottlenecks
 External traffic: determine placement of firewalls and
DMZ networks

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Explain How Applications and Traffic
Flow Can Affect the Network Design
 Installed hardware affects application performance
 Choose hardware after analyzing technical
requirements

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Identifying Application Impacts on
Network Design
Transaction-processing
applications:
 Additional operations
required
 Immediate response to
user requests
 Redundancy and security
required

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Identifying Application Impacts on
Network Design
Real-time streaming applications:
 Minimize latency and jitter
 Infrastructure may need to be upgraded

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Identifying Application Impacts on
Network Design
File transfer and email applications:
 Unpredictable bandwidth usage
 Large packet size
 Centralization of file and mail servers in a secure
location
 Redundancy to ensure reliable service

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Identifying Application Impacts on
Network Design
HTTP and web traffic:
 Network media
 Redundancy
 Security

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Identifying Application Impacts on
Network Design
Microsoft Domain Services:
 Active Directory Services
 Broadcast generation
 Tight integration between ADS, DNS, and DHCP

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Explain how Quality of Service is
Implemented on the LAN/WAN
 Capability of a network to provide preferential service to
selected network traffic
 Dedicated bandwidth, controlled jitter and latency, and
reduced packet loss

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Explain how Quality of Service is
Implemented on the LAN/WAN
Implementing traffic queues:
 Identify traffic requirements
 Define traffic classes
 Define QoS policies

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Explain how Quality of Service is
Implemented on the LAN/WAN
Set priorities to manage
traffic:
 Queue type
 Traffic assignment
 Size
 Filter traffic into high,
medium, normal and
low priorities

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Explain how Quality of Service is
Implemented on the LAN/WAN
Where QoS can be implemented to affect traffic flow:
 Layer 2 devices
 Layer 3 devices

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Explain the Options for Supporting Voice
and Video Traffic on the Network
Network design implications of converged networking:
 Strong performance
 Security features
 Mandatory use of QoS mechanisms

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Explain the Options for Supporting Voice
and Video Traffic on the Network
Network design implications of IP telephony:
 Power and capacity planning
 Identifying contending traffic flows
 Selecting components for the IP telephony solution

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Explain the Options for Supporting Voice
and Video Traffic on the Network
Live video:
• Streaming media files
• User sees content before all
packets have arrived
• No need to store large media
files before playing them
• Uses multicast packets to
many users at the same time
Video on Demand:
 Either stream or download
before viewing
 Users can store content and
view later
 Unicast packets to a specific
user requesting the service

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Explain the Options for Supporting Voice
and Video Traffic on the Network
Supporting remote workers with voice and video:
 Assess bandwidth requirements for WAN connection
 Permanent link or on-demand

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Document the Network Requirements of
Specific Categories of Applications
 Estimate the volume of application traffic during the
initial design phase.
 Document projected applications and associated
hardware in a network diagram.

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Document the Network Requirements of
Specific Categories of Applications
 Diagram the flow of traffic to and from hosts and
servers within the LAN

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Document the Network Requirements of
Specific Categories of Applications
 Diagram the flow of traffic to and from remote sites,
including VPN traffic

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Document the Network Requirements of
Specific Categories of Applications
 Diagram outgoing traffic flows destined for the Internet
gateway and incoming traffic from the Internet to
locally-provided services

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Document the Network Requirements of
Specific Categories of Applications
 Diagram extranet traffic flows to and from selected
trusted partners, customers, and vendors

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Summary
 End users evaluate network performance based on the
availability and responsiveness of their applications.
 The choice of hardware installed on a network can
affect the performance of the applications.
 When adding a new application, the designer must
consider the impact on the performance of existing
applications.
 Voice and video applications present unique
requirements, as they cannot tolerate delays.
 Security and reliability are primary concerns in a
network supporting high volumes of web traffic.
 The primary goal of QoS is to provide priority,
dedicated bandwidth, controlled jitter and latency, and
reduced packet loss.

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