Network Analysis, Architecture & Design, Second Edition
This book works through the processes of analysis, architecture, and design step by step, giving network designers a solid resource for making good design decisions.
TABLE OF CONTENTS Network Analysis, Architecture & Design, Second Edition
3.8: Developing Capacity Requirements
3.8 Developing Capacity Requirements
In evaluating application capacity requirements, we want to consider applications that require large amounts of capacity and those that require a specific value (e.g., peak, minimum, sustained) or a range of capacities. When an application requires a large amount of capacity, it is important to know when the application has a real (measurable and verifiable) requirement for high capacity and when it (or the transport protocol it is using) will just attempt to use whatever capacity is available.
Applications that use TCP as their transport mechanism, without any additional conditions or modifications from the higher-layer protocols (or from the application itself), will receive performance levels based on the current state of the network (i.e., best-effort). This is done through communicating and adjusting TCP transmission parameters (across the TCP control channel between the two devices in the TCP session) throughout the TCP session to react to conditions of apparent congestion in the network.
3.8.1 Estimating Data Rates
Estimating a data (or maybe more accurately, information) rate is based on how much information you know about the transmission characteristics (e.g., traffic flow) of the application and how accurate the estimation needs to be. Data rates that are often used are peak data rate, sustained data rate, minimum data rate, or combinations of these. These data rates may be measured at one or more layers in the network (e.g., physical, data link, network, transport, session).
The data rates of all applications are bound by some limiting factor. This may...
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