Q & A – Network/LAN Bandwidth Benchmark

Q & A – Network/LAN Bandwidth Benchmark

This document provides some frequently asked questions about Sandra. Please read the Help File as well!

Q: I get Packet too large for Network/Host error

Sandra uses large blocks to test the transfer rate. Some interfaces do not support packets this large, but only smaller packets. You can try the following:

  • Try the latest network drivers from the network card manufacturer. In most cases the built-in Windows drivers are scaled-down versions.
  • Check the driver settings – there may be a setting to allow large packet fragmentation or change max. packet size.
  • If you’ve used a modem speed booster make sure you’ve changed only the dial-up settings and not the LAN settings too. Go back to the defaults and/or clear all the settings from the registry.
  • Use a decent network adapter, e.g. Intel/3Com/HP/Compaq/etc with an internal buffer.
  • As a last resort, try a clean install of Windows.

Q: I get Cannot get IP address of host error

Go to a console and try to ping the host by name. If you cannot, make sure DNS/WINS is correctly set up, otherwise enter the host names and their IP addresses in the HOSTS file.

Q: Why are there no workgroups/domains visible?

Check that you’ve set your computer to be part of a workgroup or the correct domain and that you’re running the Microsoft Networks Client.

Q: Why are there no computers on the domain/workgroup?

Check that the network settings are correct. Try to connect to some of the computers you know should be on the network or ping them.

Q: Why is my computer not listed in the domain/workgroup?

There would be no point benchmarking the local interface, thus your computer is not shown if the workgroup/domain it is in is selected.

Q: Why don’t I get ~100MB/s for my Gigabit connection?

Unless you have a PCI Express, PCI-X/64-bit adapter or connected to an internal bus (e.g. Intel’s CSA) the normal PCI bus cannot provide enough bandwidth and you’ll be limited to 30-50% of total bandwidth. Of course, first check the cable is CAT6 and that the switch/system are linked at GBit with no dropped packets.

Q: I’ve moved my GBit-capable NAS to GBit connection but get only ~10-20% higher bandwidth! What’s wrong?

Most likely your NAS does not have enough internal bandwidth to fully use a GBit connection; it may not perform better than on 100MBit connections. Of course, first check the cable is CAT6 and that the switch/NAS are linked at GBit with no dropped packets.

Q: Why don’t I get 54Mbit for my 54Mbit Wi-Fi connection?

The MAC layer speed is not the same as the theoretical maximum speed. See table below:

Wireless LAN Specifications
WiFi Standard 802.11a 802.11b 802.11g Turbo-G MIMO-G Super-A 802.11n
Phy Speed 54Mbit 11MBit 54MBit 125MBit 125MBit 108MBit 300MBit
MAC Speed 23MBit 4MBit 20MBit 30MBit 30MBit 33MBit 120MBit
Band 5GHz 2.4GHz 2.4GHz 2.4GHz 2.4GHz 5GHz 2.4/5GHz

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