Cisco Cisco Catalyst 6000 Multilayer Switch Feature Card MSFC2 White Paper
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Design Point #1: Establish and Validate a Per-Connection Bandwidth Requirement
How much bandwidth does each user require on average? In Table 1, the nominal throughput requirements for
several popular applications and use cases in a higher education setting are shown.
Table 1.
Bandwidth Requirements per Application
Application by Use Case
Nominal Throughput
Web - Casual
500 kilobits per second (Kbps)
Web - Instructional
1 Megabit per second (Mbps)
Audio - Casual
100 Kbps
Audio - Instructional
1 Mbps
On-demand or Streaming Video - Casual
1 Mbps
On-demand or Streaming Video - Instructional
2-4 Mbps
Printing
1 Mbps
File Sharing - Casual
1 Mbps
File Sharing - Instructional
2-8 Mbps
Online Testing
2-4 Mbps
Device Backups
10-50 Mbps
In all cases, it is highly advisable to test the target application and validate its actual bandwidth requirements.
Software designers are often required to pick just one average number to represent the application’s requirements
when there are actually many modes and deployment decisions that can make up a more accurate number. It is
also important to validate applications on a representative sample of the devices that are to be supported in the
WLAN. Additionally, not all browsers and operating systems enjoy the same efficiencies, and an application that
runs fine in 100 kilobits per second (Kbps) on a Windows laptop with Microsoft Internet Explorer or Firefox, may
require more bandwidth when being viewed on a smart phone or tablet with an embedded browser and operating
system.
Once the required bandwidth throughput per connection and application is known, this number can be used to
determine the aggregate bandwidth required in the WLAN coverage area. To arrive at this number, multiply the
minimum acceptable bandwidth by the number of connections expected in the WLAN coverage area. This yields
the target bandwidth needed for the need series of steps.
Design Point #2: Calculate the Aggregate Throughput Required for the Coverage Area
If this design guide was for a wired rather than wireless network, calculating aggregate throughput requirements
would entail dividing the aggregate capacity by the channel bandwidth available. Then, the number of channels
would be established and these would be plugged into a switch. But in a WLAN, a channel’s speed is effected by
multiple factors including protocols, environmental conditions, and operating band of the adapter. Before
calculating aggregate throughput, several things must be considered.
In the aggregate throughput calculation, the connections instead of the seats were used as the basis for
calculation. The number of connections in a cell is what determines the total throughput that will be realized per
connection instead of the number of seats. Most users today carry both a primary computing device (such as a
smartphone, tablet computer, or laptop) as well as a second device (such as a smartphone). Each connection
operating in the high-density WLAN consumes air time and network resources and will therefore be part of the