Introduction to Network Bottlenecks
Running programs over the network is likely to result in network bottlenecks. Other causes
of high network activity are, roaming profiles, file copying or large print jobs.
Use performance monitor to create a log and calculate the network utilization.
Network Topics
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Begin by selecting these counters:
Network Interface\ Bytes Total/sec
Network Interface\ Bytes Sent/sec
Network Interface\ Bytes Received/sec
Network Interface\ Current Bandwidth
Before you launch in detecting network bottlenecks, it's worth checking,
and eliminating, hardware problems with the NIC, or a broken cable. If
you are not sure have a look at the device manager or even the system logs.
Any doubts, try changing the network card and the cable, especially if this
is an intermittent problem. Counters that may confirm a hardware
problem are: Packets Outbound Errors and Packets Received Errors counters
This network example assumes that your hardware is working properly. There are several cautionary tales with
the performance monitor chart below. Let me see if I
can convince you that the maths prove a network bottleneck.
The Bytes / Sec average 913,999. Beware, System Monitor never
uses thousand separators which make the figures awkward to read. I
have often revisited the data because I was out by a factor of ten.
For example, at a glance you could mis-read 913999 as approximately 91,399 or
even 9,1399,999.
Diagram 1
You may think that just comparing the red line (Current Bandwidth) with
the white line (Bytes /Sec) proves that the network is at full capacity. On
closer inspection of the Scale, you realize that the red line is 10x bigger than the white
line. Now you may revise you estimate and believe that the network is only running at 10%
of capacity.
However, there is one more factor, the red line is in bits while the white
line is in
bytes. 1 bytes = 8 bits. When you compute all these factors, the network is actually running at
73%.
Summary
of Diagram 1
- White Line Bytes /Sec = 913,999 bytes x 8
- White Line Bytes /Sec = 7,311,992 bits.
- Red Line Current bandwidth = 10,000,000 bits
- Network Utilization = 73.12%
Background to Networks
One of the amazing features of the original ethernet network is that only one
machine can transmit at a time. Once the network reaches 30% capacity,
pure chance means that two machines try and send a packet at the same
instant. The result is more and more collisions start
happening, this leads to re-transmissions and a slow down of network
traffic.
Networks bottlenecks occur at surprisingly low levels of utilization.
40% would normally be considered a bottleneck, and the only reason that I
got a higher value was that there are only three machines on my test
network. The more machines the greater the risk of collisions from two
machines wanting to transmit at once. However, with modern production networks two items of technology have alleviated the above bottleneck problem:
a) Switched networks replacing hubs
b)
Faster
network cards replacing the old 10MB cards.
Guy Recommends: SolarWinds LANSurveyor
LANSurveyor will produce a neat diagram of your network topology. But that's
just the start;
LANSurveyor can
create an inventory of the hardware and software
of your machines and network devices. Other neat features include dynamic
update for when you add new devices to your network. I also love the ability to export
the diagrams
to Microsoft Visio.
Finally, Guy bets that if you take a free trial of LANSurveyor then you will
find a device on your network that you had forgotten about, or someone else
installed without you realizing!
Download a Free Trial of LANSurveyor
The problem is that it seems to have been discontinued in Windows 2000
onwards. Several respected sites claim you can install Network Segment
via the Network Monitor, or Protocol Driver. For what its worth I have
tried numerous techniques of getting the counter to appear in performance
monitor without success - I agree
with Microsoft Network Segment is no longer available.
Microsoft's TechNet article 253790 Says:
SUMMARY
In Windows 2000, installing Network Monitor does not add the Network Segment
object in System Monitor as in Microsoft Windows NT.
MORE INFORMATION
To increase the stability and reliability of the Windows Management
Instrumentation (WMI) interface, this object has been removed from System
Monitor in the Performance tool in Windows 2000.
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