Free from physical limitations of Network cables wireless mesh network roaming

The rise of WIFI:Since its advent, the Internet has gradually become an indispensable part of people's lives and work. At the same time, computers used as tools for people to access the Internet have also changed from expensive and scarce laboratory equipment to the case of thousands of households. As desktops become increasingly popular, laptops and PDAs become increasingly lightweight and powerful. This means that people can easily take their computers from one place to another. In such a situation, if the Internet is still only connected to the wall with a network cable, it will appear out of touch or even unreasonable.

Where there is demand or market, there will be technological innovation. In recent years, the emergence and prevalence of WIFI-dominated wireless Internet access technology has emerged. With WIFI, people get rid of the physical limitations of the network cable and gain a new kind of freedom. At home, you don't have to sit in a place with telephone lines or connections to access the Internet. You can go from the living room to the bedroom and still maintain network connection. At the company, you can go to the meeting room from your office and check your email at any time. On the street, you can watch the news online during a nap in the coffee house, or chat with friends from other places. Once at the airport, the station waited for a long time, and now it can also be used to access the Internet to handle important work or use online entertainment, games, and so on. Similar freedom brought about by wireless Internet access can be said to be numerous, which is also an important reason for the rapid popularity of WIFI. We can see that the convenience brought by liquidity is the key attraction.

What is roaming?

With a good wireless Internet access environment like wireless mesh network, if wireless Internet access is combined, it can be said that it is a "inherent" mobility characteristic, we will not realize that there is a demand that will become especially natural and urgent: roaming.

What is roaming? In WIFI technology, a user's terminal device, such as a laptop with a wireless network card, is usually connected to a wireless access point/AP) to obtain network services. However, a wireless access point has limited coverage. Due to the mobility characteristics of wireless Internet access, the user of the terminal device may quickly move out the coverage of the connected access point. In this case, a new access point that is closer to each other can be claimed, so that the terminal device can connect to the new wireless access point to maintain its original Internet services. The process of switching from the current wireless access point to another Wireless Access Point and maintaining network connection is called roaming.

We can easily see that the technical support of roaming includes two natural components: one is the support of user terminal devices. On the other hand, it supports wireless access points and wireless mesh networks. In terms of user terminal devices, the support for roaming is relatively mature, and the implementations of various vendors are basically the same. Here is a brief introduction. Generally, the client continuously monitors the signal quality of the connected access point. When the signal quality is lower than a certain degree, the client will actively scan the surrounding environment to find a better wireless access point. If yes, a connection request is sent to it to establish a connection with the new wireless access point.

Compared with client support, the support for wireless access points and wireless mesh networks is completely different. The client is mainly a process of finding a better access point. In terms of wireless access points and wireless mesh networks, it is a process of realizing that the client is connected to a new access point and making necessary adjustments so that the user's data flow can be correctly sent to the new access point.

Layer-2 and layer-3 wireless Mesh Networks

Before we introduce the roaming support for wireless mesh networks, we need to further introduce the two types of wireless mesh networks: A layer-2 wireless mesh network and a layer-3 wireless mesh network.

We know that in the OSI network layered model, the second layer is the data link layer, and the third layer is the network layer. From the TCP/IP perspective, simply put, a layer-2 wireless mesh network treats the entire wireless mesh network as an IP subnet. This IP subnet is a complete broadcast domain. The layer-3 wireless mesh network allows the entire wireless mesh network to be divided into multiple IP subnets. The communication between subnets is implemented through IP routing. The implementation of a layer-2 wireless mesh network may be simpler, but it has many disadvantages. For example, an IP subnet is a complete broadcast domain. In the network, broadcast traffic is a resource-consuming thing. Therefore, everyone tries their best to limit the range of a broadcast domain, otherwise the network performance will be intolerable. If it is hard to understand, let's think about it? Why do people divide the entire internet into so many IP address subnets? This is because only in this way can the range of broadcast domains be limited, so that it is easy to manage and the Internet can be scalable. Similarly, a wireless mesh network also needs to limit the range of broadcast domains. When the network is very small, the layer-2 method may not be a big problem, but if your wireless mesh needs to cover a slightly larger area, only a layer-3 wireless mesh network can be competent.

Wireless Mesh Network roaming

Layer-2 mesh network roaming

Now let's go back to the roaming topic. In a layer-2 wireless mesh network, it is relatively easy to implement roaming. The main reason is that, as we have mentioned, the entire wireless mesh network is treated as an IP subnet. Therefore, from the perspective of external IP address routing, the new access point and the old access point are still in the same destination, so there is no need to adjust the routing, but the forwarding information of the Second-layer bridge inside the mesh network needs to be adjusted, however, it is easy to implement. Although it is simple, we have already introduced that the layer-2 method cannot be used to spread the wireless mesh to a relatively large scale without affecting network performance, in this case, it is essential to support layer-3 cross-subnet roaming.

Layer-3 roaming-Mobile IP

Mobile ipmobile ip is a traditional three-tier roaming solution. Its advantage is standardization. However, since the advent of Mobile IP, Mobile IP is not very popular, for some reason. In the specific application of wireless mesh network, some disadvantages of Mobile IP are even more prominent. First, Mobile IP requires that the client software support mobile IP. This may sound like nothing, but in fact it is an unrealistic assumption that there are tens of millions of laptops and PDAs without saving the support of Mobile IP addresses. Another important disadvantage of Mobile IP is that its protocols are complex and costly. Because of its pure three-layer design, the trigger reaction to roaming events is slow, and it often cannot meet the time requirements of fast roaming. This is particularly evident in the application of IP speech.

A roaming solution combining Layer 2 and Layer 3

To sum up, for network scalability and network performance, a layer-3 wireless mesh network has obvious advantages, so that layer-3 cross-subnet roaming must be supported. However, the traditional three-tier roaming solution is difficult to meet the requirements in terms of performance and feasibility. To meet this challenge, adelia Technology Co., Ltd. has designed a solution that combines Layer 2 and Layer 3. Due to the close combination with 802.11 of the second layer of the network, this solution can quickly respond to roaming events, so as to take immediate action and minimize the roaming latency. Because its subject is still working on three layers of the network
The roaming solution allows the customer to freely roam within the coverage of the three-tier Wireless Mesh Network of adelia Technology Co., Ltd. More importantly, this solution does not require client devices to pre-install any additional software, making it simple and feasible.

Remarks: Introduction to wireless Mesh Networks

However, the traditional Wi-Fi products have not completely removed the limitations of Wired connection. Generally, each wireless access point is followed by a wired uplink port. Therefore, traditional online devices such as DSL are still essential at home. In a large office area, the wiring of a large area is also required. In the streets, only a few businesses with wired Internet access capabilities can provide wireless Internet access services. To further break these restrictions, wireless mesh networks have become a hot spot in the past two years.

What is a wireless mesh network? Let's take a look at the network before the emergence of the mesh. Whether it is a pure wired network or a traditional non-mesh wireless network, no matter whether the end user connects the network in a wired or wireless way, constitute the network equipment switches, routers, wireless access points, etc. of the network itself) they are all interconnected in wired mode. This means that there must be wiring problems between network devices. In the implementation of the wireless mesh network, the limitations of Wired interconnection are broken between network devices. This greatly expands the "sphere of influence" of wireless networks and truly makes wireless networks ubiquitous. At the same time, wiring troubles and astonishing costs are greatly reduced, further promoting the development of wireless networks. For example, a city can provide a uniform wireless mesh network, and its commercial areas and residential areas can enjoy the benefits of wireless Internet access. Compared with the economic benefits of deploying a wired network and the advantages of the wireless technology we have mentioned, the wireless mesh network is undoubtedly extremely attractive.