Category Archives: Technology

Troubleshoot a Slow Computer Network – Your Computer is Slow and Not the Network

Slow Data Transfer is not Always caused by the Network

Slow data transfers are sometimes caused by a slow computer. Determine if the computer is the reason by comparing the transfer speed with a different computer connected on the same switch port. If the speed is the same, the problem is your network. If you get faster data transfers with a different computer then the problem is the computer.

A computer could be slow because of various reasons:

A bad network card. Troubleshoot: Swap the network card and test the data transfers afterwards.
The computer is outdated and it runs software that needs more resources. Troubleshoot: change the computer.
Slow hard-drive. The hard-drive will always be the computer’s bottle neck. It is the slowest part of a desktop computer. Old hard-disks are very often seen in new computers. Hard-disk fragmentation is a frequent reason for slow computers. Troubleshoot: Defragment often your hard-drive and reserve a 25% free space on the drive.
The computer might be infected with a virus or a Trojan. Troubleshoot: scan the computer for viruses. On a Windows machine run the command “netstat -a -b” to see what ports are being used and which program is using them. Use a network sniffer and monitor the network activity on the specific computer.
The transfer is intermittently slow, check what background processes are using the CPU, Memory, and hard-drives. Windows Vista can sometimes be a resources hog by allocating too many resources for background processes such as indexing and running the antispyware. Antivirus or other antimalware can consume a lot of the computers’ resources. Troubleshoot: Change the schedule for maintenance tasks to a time when you are not using the computer. Check what other programs are running in the background and configure accordingly. Some antivirus programs enable scanning the network drives by default.
A slow network printer. A slow network printer can be caused by the power save feature. If you use the printer very often you might consider turning off the power save.
A slow Network Attached Storage device. A slow NAS could be caused by improper SAMBA configuration or a disk power save feature. The power save feature is fairly easy to fix, just disable it if you find that you are using the drive very often. The SAMBA tune up is more difficult and usually it is complicated to have terminal access to the device itself. Many manufacturers do not allow direct access to the OS. SAMBA is a free implementation of Microsoft’s SMB protocol. SAMBA, SMB and CIFS offer file and print sharing services for Windows and Linux/Unix machines

This article is part of a five posts series regarding Network Troubleshooting.

Troubleshoot a Slow Computer Network – Only One Computer on the Network is Slow

Only One Computer on the Network is Slow

Client Computer Network Mask Wrongly Configured
Your network is a class C network, (net-mask 255.255.255.0), and your client computer has its IP address configuration on a class B network, (255.255.0.0). Change the network mask of the client to match the network configuration.

Poor network cards
Bad network cards or bad drivers are very often the reason for poor transfer rates. Test the transfer rate with a different network card.
An outdated computer can also slow down your network transfer.

Bad Network Configuration
DNS Configuration
can be the cause a of slow network connections.
Wrong DNS address in the IP configuration can slow your network dramatically. Your DNS client will try to connect to an inexistent or not working DNS server then give up and try your secondary DNS server. This translates in slowdowns and sometimes even DNS resolution errors.
Fix: Ping the DNS address or, even better, use nslookup and connect to both of your DNS servers to check if they work.

The TCP/IP protocol stack corrupted.

Sometimes no matter what you do you can’t fix the network and this is because the TCP/IP becomes corrupted. The only thing that fixes it is a reset. On older Operating Systems, such as Windows 98 and Windows NT, the fix was to uninstall and reinstall the whole TCP/IP suite of protocols.
Fix: issue the following command to reset it: netsh int ip reset c:\resetlog.txt.

More Than One Default Route
Advanced Lan SettingsA very common mistake is to assign more than on default route to the same computer. Do not confuse load balancing with multiple Default Gateways. You are configuring two network cards, and both of them have a default gateway. This configuration will not work. Usually, a Windows computer will warn you that this is not a good idea, but some users will choose to ignore the warning.
This is a typical problem for laptop users, they connect into the Lan environment and leave the wireless connection on. This will create a lot of problems for corporate users and even for home users.
In order for this type of configuration to work, special routing rules and IP configuration is needed. it is easier to turn the wireless of or have an adapter manager that will automatically do that for you based on your rules.
Advanced Tcp/IP Settings
On a Windows XP there is a way to assign priorities to network cards using a graphic interface. from the Network Connections applet in the Control Panel, click on the Advanced menu and choose Advanced Settings.
On the Advanced Settings window arrange the network cards according to the correct priority.
Another way to achieve this is to change the gateway’s metric for each of the network adapters on the computer. To do this, open the TCP/IP properties on each of the network addapters with a default gateway configured, and click on the Advanced button. On the Advanced TCP/IP Settings window, uncheck the Automatic Metric for the Default Gateway, and enter a value according to your network topology. The lower the metric, the higher the preference for a default route.

This article is part of a five posts series regarding Network Troubleshooting.

Troubleshoot a Slow Network – Slow Server

Slow Server

How do we know the server is slow and the problem is not elsewhere?
Make a file transfer between any two other computers on the network. Compare the measurements with the server’s transfer rates.
What are the reasons for a slow server?
There are many reasons for a slow server. The server is many times the bottle-neck of a network. Here are a few reasons for a slow server:
An average, or below average network card, (you need good quality network cards for a server).
Server Network Card Underutilized. Connect your server on the backbone or on 1GB switch ports to make use of the high speed network card. You probably want to limit all your clients to transfer at 100Mb so that there is no traffic discrimination. If your server and switches support higher transfer rates, (10GB ports), make sure you make use of it.
Slow disks. Poor hardware is many times the main reason. Improper configuration, such as choosing the wrong RAID type, or not using write caching can be another reason.
Too many clients on a server. If too many clients make requests to the same single server this could overload the server and it will perceived as a slow network by the users. Measure your server’s performance on load using the performance logs and alerts and the system monitor in Windows. Usually the performance is changing over the course of a day based on the number of users who access the server at the same time. Sometimes adding another network card would be sufficient. Enabling cache writing on the SCSI card can help a lot, (make sure you install a cache battery), adding a new SCSI card and additional disks to offload the existing ones could be of help. Sometimes adding another CPU can make a difference, (if you have free CPU slots). Memory is very often the most used method of upgrading, but most of the times it is not the needed solution. Use the performance logs and alerts and the system monitor and compare with the recommended thresholds to determine what your bottleneck is.
Slow server response, (packet sniffer to determine the handshake time), Adjust the server’s configuration to optimize the handshaking time; (this is a fairly advanced optimization task).

This article is part of a five posts series regarding Network Troubleshooting.