Technology base of LAN: conflict domain and broadcast domain

In the LAN technology, the conflict domain and the broadcast domain these two words have the very big influence to the network performance, below lets us see how these two words affect the network performance.

The conflict domain of LAN technology

If you want to drive out of the freeway, but every time you try, there's a car blocking your way. If forced out, collisions can occur, similar to what happens on Ethernet using a carrier-listening multichannel access (CSMA/CD) protocol with conflicting detection. The Institute of Electrical and Electronic Engineers (IEEE) defines CSMA/CD ethernet as the 802.3 standard, which is now used throughout the network. The media access control (MAC) layer of the second layer of the Open Systems Interconnection model (OSI) is the use of the CSMA/CD protocol to access physical media.

All nodes in the network can send data whenever they need it, while the CSMA/CD network strives to ensure that only one node at any one time sends the data. However, it is possible for two nodes to send data at the same time, such as Node 1 and Node 4 in Figure 1-1. If this happens, it can cause a collision. This is the same as what we just said about driving the car out of the highway, because we didn't see another car get in the way, and when you pulled out, the other car hit you at 100 miles per hour.

But, unlike a crash on a motorway, it's hard to recover when a car crashes, and network nodes can continue to listen to the line. If a device detects a collision, it stops sending and notifies the other node of the collision. All other nodes that are being sent are notified to stop sending. Collisions occur only in Ethernet. The only thing we care about is how much the collision frequency will affect the performance of the network. I wonder if this metaphor will make you understand what a conflict domain is.

The concept of the conflict domain can also be explained in the diagram below, in the work of the Ethernet hub on the front panel LEDs can help users detect when the network segment conflict saturation. Even if there are several tools that can detect slow network speed and bottleneck problems, I still think that the LED on the hub is fast and convenient. There is a network segment, its hub on the impact of the LED lights are always on the light, but surprisingly, I have never heard the network paragraph any user has complained. I know it may be hard to believe, but it's true!

Figure 1-1 Two nodes in Ethernet are sent simultaneously

Broadcast domain of LAN technology

Before discussing the broadcast domain, you must first understand what is broadcast. A broadcast is data that is sent to all nodes on a network segment, not to a single node or a set of nodes. This can be achieved by sending the data to the Mac 0xFFFFFFFFFFFF on the node to be broadcast. Therefore, the broadcast domain consists of a set of nodes that can receive broadcast messages from all other nodes in the same group. Typically, all nodes on a router-by-hub connection form a broadcast domain, as shown in Figure 1-2.

For the above network, all 1 6 nodes constitute this broadcast domain. Node 2 on h U B 3 broadcasts not only to hosts on H U B 3, but also to all hosts on H U B 1, h U B 2, and H U B 4. The hosts on H U B 1, h U B 2 and h U B 4 also broadcast to all other nodes.

The number of broadcast message encounters in broadcast domain increases with the expansion of network scale. All of these broadcast messages do affect the performance of the network, and if mismanaged, it can even cause the entire network to crash.

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