TCP. The Segments/sec counter tells you the total number of TCP segments your computer has sent and received. Segments Retransmitted/sec shows the number of segments your computer must resend because of errors. This value isn't always zero, because network collisions can occur, but it should be only a fraction of the Segments Sent/sec. Screen 4 shows some TCP and IP/UDP counters.
IP/UDP. The IP Datagrams/sec counter shows the amount of TCP/IP network traffic, which is sent as datagrams. Datagrams are typically broadcasts. To reduce broadcast traffic, you need to know which services and processes use datagrams. The IP protocol splits the data into fragments that the receiving computer reassembles. The Fragment Re-assembly Failures counter might be telling you the receiving computer is having trouble putting the fragments back in order. Transmission errors and timeouts can cause this problem. The UDP counters measure datagrams at the transport layer, whereas the IP counters measure datagrams at the network layer. The Datagrams Outbound Discarded and Datagrams Received Discarded counters tell you how many datagrams your system is discarding even without transmission errors. An increase in these counters indicates insufficient network buffer space.
Network Interface
Screen 5 shows two Network Interface card instances, but the computer has only one card. The first instance is a loopback path, which is the local path through the protocol driver and network card. You'll want to check the second instance, which shows data your computer sent out onto the network. You can use this network card to measure total bytes and packets sent and received to analyze your system's throughput.
You might think the Current Bandwidth counter would monitor any network interface, but this counter shows theoretical rather than actual bandwidth. Similarly, you might think the Output Queue Length counter would show bottlenecked data requests. However, the network card doesn't handle transmission requests, so this counter is always zero. Instead, the network device interface specification (NDIS) software handles transmission requests.
The best counters to monitor for network card problems are Packets Outbound Errors and Packets Received Errors. Compare the Packets Outbound Discarded and Packets Received Discarded counters with the total packet throughput to see the number of error-free packets the system is dropping. The system might drop packets to free buffer space, so an increase in these counters tells you the network buffers are too small.
Network Segment
To add Network Segment counters, you must install the Network Monitor Agent. (Go to Control Panel, Network, Services.) When you monitor Network Segment counters in Performance Monitor, the network card is in promiscuous mode. The network card typically rejects network traffic intended for other network cards, but in promiscuous mode the network card accepts this traffic and passes it to the computer for analysis. This activity drains the resources of the computer you're analyzing, so you'll want to limit Network Segment monitoring.
Monitoring the Network Segment counters increases CPU use. As these counters process network traffic, they use additional system resources. A reasonable limit for an Ethernet network is %Network Use less than 30 percent. A higher value means you need to speed up the network or reduce the amount of traffic.
You can use the %Broadcast Frames and %Multicast Frames counters to view the percentages of broadcast and multicast traffic. Network cards pass broadcast and multicast frames to a higher-level software component before they act on or discard them. This extra activity results in additional CPU use. In Screen 6, you see a spike in broadcast traffic after a file transfer. As the requesting computer connects to find the server computer's network address, it generates broadcast traffic. Frame traffic increases as the server transfers the files.
Server
You can easily overlook the Server object, because this counter is sometimes considered a service rather than a network object. The Server service sends resources over the network to clients, so how it responds to data requests is important to system performance. A fast network is useless if it connects you to a slow server.
On a domain controller, you need to monitor the Logon Total and Logons/sec counters. Logon Total is a cumulative counter that shows the number of logons since you booted the server (not the number since you started Performance Monitor). You can use the Logons/sec counter to ensure the system is adding users efficiently during peak logon traffic.
If your system primarily functions as a domain controller rather than a file and print server, you can tune it to optimize logon performance. From Control Panel, Network, Services, open the Properties dialog box for the Server service. Select Maximize Throughput for Network Applications, as Screen 7 shows, and click OK.
Resources and Recommendations
The Microsoft Windows NT Server 4.0 Resource Kit is the best reference for Performance Monitor. (The server resource kit CD-ROM also includes the workstation resource kit text.) The Microsoft Windows NT 3.51 Resource Kit has an excellent chapter called "Detecting Network Bottlenecks" that isn't in the 4.0 kit, so you'll want to refer to that version if you still have it. Microsoft's current TechNet CD-ROM contains several useful performance tuning articles. TechNet also explains Performance Monitor counters in detail. Try searches such as NetBEUI Object and IP Object.
End of Article
Prev. page
1
[2]
next page -->
