The network monitor is a process of controlling the behavior of one or more network monitoring terminals (hardware) in the network through the network monitor software.
Network monitor
Network monitor is through
A common monitor is equipped with a network card to provide a network interface. At present, many domestic manufacturers can realize the grafting of network interfaces, so this type is selected.
Network Monitor is a Microsoft Systems Management Server and Microsoft Windows 2000 Server provider utility. You can use Network Monitor (also known as NetMon) to capture and view communication patterns and problems on your network.
Step 1: When launching Network Monitor, it will display the capture window . The capture window contains four frames:
Pane name
content
relation chart
current
Instructions
Before using the network monitor, we need to know the transmission mode of the frame, that is, Unicast Frame, Multicast Frame, and Broadcast Frame.
1.Unicast frames
Unicast frames are also called "point-to-point" communications. At this time, the frame is received and transmitted only between two nodes. The destination MAC address of the frame is the MAC address of the other party. The network device (referring to the switch and router) forwards the frame according to the destination MAC address in the frame.
Multicast frames
Multicast frames can be understood as one person speaking to multiple people (but not everyone present), which can improve the efficiency of the call. Multicast accounts for a small portion of the network, and is mainly used for internal communication of network equipment, online video conferencing, and online video on demand.
Broadcast frames
The broadcast frame can be understood as one person speaking to everyone present. The advantage of this is that the call is efficient and the information can be transmitted to the whole person at once. In the broadcast frame, the destination MAC address in the frame header is "FF.FF.FF.FF.FF.FF.FF", which represents the MAC addresses of all host network cards on the network.
Broadcast frames are indispensable in the network. For example, the process of a client automatically obtaining an IP address through DHCP is implemented through broadcast frames. Moreover, since devices also need to communicate with each other, even if no user sends broadcast frames artificially in the network, a certain number of broadcast frames will appear on the network.
Compared to unicast and multicast, broadcast occupies almost all the bandwidth of the network within the subnet. There cannot be a large number of broadcast frames in the network for a long time, otherwise there will be a so-called "broadcast storm" (the number of broadcast frames per second is more than 1000). Take the conference as an example. Only one person can speak at the conference. If everyone speaks at the same time, it will be a mess. Broadcast storm is that the network is occupied by a large number of broadcast data packets for a long time, which makes normal point-to-point communication unable to work normally. The external performance is that the network speed is extremely slow. There are many reasons for a broadcast storm. A faulty network card may send broadcast packets on the network for a long time and cause a broadcast storm.
Using routers or Layer 3 switches can isolate broadcast storms between different subnets. When a router or a Layer 3 switch does not process a broadcast frame when it receives it, it can no longer pass it to other subnets, so as to isolate the broadcast storm. Therefore, in large and medium-sized local area networks composed of hundreds or even thousands of computers, in order to isolate broadcast storms, subnetting must be performed.
How to understand Network Monitor
After the above understanding, we can understand the parameters of the network monitor. Click "Start Programs Administrative Tools Network Monitor" in Windows 2000 Server to run "Network Monitor". When running for the first time, you will be prompted to choose which network card to monitor for network traffic. After selecting, click the [OK] button, the network monitor will only monitor the specified network card, and the indicators generated are for this network card. Click the triangle button in the toolbar to start monitoring the traffic of the specified network card.
The network monitor provides network communication monitoring functions such as "network utilization", "frames per second", "bytes per second", and "broadcasts per second". These parameters are very useful for network troubleshooting and network monitoring Important role.
Among them, "network utilization" is the ratio of the current network load to the maximum theoretical load. The LANs we use today are all Ethernet. The maximum network utilization of shared Ethernet (using a hub) is only about 50%. If this value is exceeded, the network is saturated and the network speed will be very slow. Switched Ethernet ( Using switches), the maximum utilization rate can reach about 80%. "Frames per second" refers to the number of frames sent and received by the monitored network card per second. It can be used as an indicator of network traffic. "Bytes per second" refers to the sum of the frame values sent and received by the monitored network card. It is also an indicator of network traffic. "Broadcasts per second" is the number of broadcast frames sent and received by the monitored network card. Under normal circumstances, the number of broadcast frames per second is relatively small. It depends on the number of computers on the network. At this time, the number of broadcast frames per second is very high, up to more than 1000 frames per second.
