To correctly understand the specific meaning of broadcast storms, we must understand how network devices working on the network work. At present, network equipment working in Internet cafe networks are basically switches. When it comes to switches, people don't really understand how they work.
1. Basic knowledge of switches
1. Definition of a switch: A switch is a network device based on MAC (hardware address of a network card) identification and can complete the function of encapsulating and forwarding data packets. The switch can "learn" the MAC address and store it in the internal address table. By establishing a temporary exchange path between the originator and the target receiver of the data frame, the data frame can directly reach the destination address from the source address.
Now, the switch has replaced the network device hub, also known as Hub, which we were familiar with. But that doesn't mean we don't need to understand the basics of Hub.
2. Definition of hub: Hub (HUB) is a basic device in data communication systems. Like transmission media such as twisted pair, it is a hardware device that does not require any software support or requires little management of software management. It is widely used in various occasions. The hub works in a local area network (LAN) environment, like a network card, and is applied to the first layer of the OSI reference model, so it is also called a physical layer device. The hub uses electrical interconnection. When the environment for maintaining the LAN is a logical bus or ring structure, it is possible to use the hub to establish a physical star or tree network structure. In this regard, the hub plays a role equivalent to a multi-port repeater. In fact, a hub is actually a type of repeater. The only difference is that the hub can provide more port services, so a hub is also called a multi-port repeater.
2. The difference between switches and hubs
Now, we often have a technical misunderstanding. We use switches and all data is forwarded point-to-point, so why does a broadcast storm still occur? After fully understanding the functional differences between switches and hubs, we will understand why there is a broadcast storm in networks that use switches as network devices.
1. The essential difference between a switch and a hub: a network composed of a hub is called a shared network, while a network composed of a switch is called a switched network. The main problem with shared Ethernet is that all users share bandwidth, and the actual available bandwidth of each user decreases with the increase of the number of network users. This is because when information is busy, multiple users may "contact" one channel at the same time, and one channel is only allowed to occupy one user at a certain moment. Therefore, a large number of users are often in a monitoring and waiting state, resulting in jitter, stagnation or distortion during signal transmission, which seriously affects the performance of the network.
2. In switched Ethernet, the switch provides a dedicated information channel to each user. Unless two source ports attempt to send information to the same destination port at the same time, multiple source ports and destination ports can communicate at the same time without conflict. Through experiments, in a LAN composed of multiple servers, the actual maximum transmission speed of switched Ethernet in half-duplex mode is 1.7 times that of shared network, while the actual maximum transmission speed of switched Ethernet operating in full duplex mode can reach 3.8 times that of shared network. Switches are just different from hubs in terms of working methods. Others such as connection methods and speed selection are basically the same as hubs. Current switches are also divided into 10M, 100M and 1000M in terms of speed, and the number of ports provided is mostly 8 ports, 16 ports and 24 ports. Switches are mainly used in LANs to connect to workstations, Hubs, servers or to decentralized backbone networks.
3. Causes of broadcast storms
Through understanding the above network equipment, we can simply analyze the reasons for the broadcast storm on the Internet. Generally speaking, there are several main reasons for the Internet broadcast storm:
1. Reason for network equipment: We often have this misunderstanding that switches are point-to-point forwarding and will not cause broadcast storms. When we purchase network settings, the switch we purchase is usually a smart Hub, but is sold by profiteers as a switch. In this way, when the network is a little busy, a broadcast storm will definitely occur.
2. Network card damage: If the network card of the network machine is damaged, a broadcast storm will also occur. The damaged network card constantly sends a large number of data packets to the switch, resulting in a large number of useless data packets and a broadcast storm. Due to the broadcast storm caused by physical damage to the network card, it is difficult to eliminate the fault. Since the damaged network card can generally be accessed online, we generally borrow Sniffer LAN management software to view network data traffic to determine the location of the fault point.
3. Network loop: During a network troubleshooting, I found a ridiculous error, a twisted pair cable, inserted at both ends on different ports of the same switch, which caused a sharp decline in network performance and it was very difficult to open a web page. This kind of failure is a typical network loop. The emergence of network loops is generally caused by the two ends of a physical network line being connected to a network device at the same time.
4. Internet viruses: At present, some of the more popular Internet viruses, such as Funlove, oscillator wave, RPC, etc., will be immediately spread through the Internet once the machine is poisoned. The spread of network viruses will lose a large amount of network bandwidth, cause network blockage, and cause broadcast storms.
5. Use of hacking software: At present, some Internet users often use hacking software such as network law enforcement officers and network scissors hands to attack the internal network of Internet cafes. Due to the use of these software, the network may also cause a broadcast storm.
In order to make a quick judgment of the fault, good and solid basic knowledge is indispensable. Therefore, in your future study, don’t ignore the learning of basic knowledge!
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