Xiao Bian recently saw a joke on the micro-blog, he said: landlord whim, to set up home WIFI name became who will love me, the password is nobody. The next day, the whole building are connected to the WIFI landlord.
The joke is a little exaggerated, but WIFI name which appeared just leads to the theme of this issue - this small series will introduce you to the basic concepts of the WLAN.
Weibo is mentioned in the "who will love me" First to introduce the grand, WLAN termed SSID. The SSID is the most contact with everyone in daily life, such as we go to Starbucks, sipping coffee while the Internet, when we search for wireless networks using a mobile phone, pop-up "CMCC-STARBUCKS" is the SSID. SSID stands for Service Set Identifier, which is a service set identifier for a set of services, according to most people's understanding, which is used to identify an available network. The so-called service set, is a set of wireless devices linked to each other, so to understand a little abstract, for example, at Starbucks offers wireless network, our phones, tablet PCs, laptop with a wireless card in this series the wireless terminal (referred to in the WLAN station STA, Station), as long as connected to the AP, in fact, constitute a set of services. Within this set of services, as long as the associated terminal and the AP, the terminal can communicate with each other (of course, need to AP), you can also access the external network through the AP.
If this coffee shop is very small, as long as the AP will be able to hold a live audience, that this is only one AP service set, then this set of services can be considered a basic service set BSS. Wireless network BSS Basic Service. All terminals associated to an AP, the AP cable to connect other devices and controls all the data transfer process and leading throughout the BSS.
If the cafe is very large, or if this is not a cafe, but a large mall, it is bound to be multiple AP, to know that a limited geographical area covered by the BSS, no more than 100 meters in diameter, this time there will be the concept of a service set ESS (extend service set) expansion.
ESS simple appreciated that the BSS plurality composition with the same SSID, but this implies the intermediate two conditions:
1, the BSS to next placement.
2, the BSS through a variety of distribution systems interconnected, wired and wireless can be, but are generally Ethernet.
Only after these conditions are met, we believe that these can be unified into a BSS ESS.
Of course, if it is provided by two Starbucks network, although the same network number provided, called "CMCC-STARBUCKS", but this is clearly not an ESS.
The use of the same SSID, we do not feel we are more connected to the BSS, but rather as connected to the same AP the same. And the like in the communication terminal in the BSS ESS, but if the BSS terminal A wants B and the communication terminal in another BSS, is the need to go through two access points AP1 and AP2, i.e., A-> AP1-> AP2 -> B.
In particular, the process in the same ESS between different BSS handover is called roaming. Also shown in the FIG terminal A (position A 'on the drawing) from the roaming region to the BSS1 BSS2, case A and B, the communication can still be maintained, but at the access point AP before and after the A roaming changed.
Xiao Bian has just told the foregoing, we SSID used to identify a network, remember. We are talking about SSID is usually a string of up to 32 characters, also known as the SSID ESSID, it is the identification of the ESS. Xiao Bian said that as long as a ESS, we are not feel connected to the BSS which is right, you do not know nothing, but the terminal equipment must know it, so there BSSID this concept. The BSSID is used to identify the BSS. This identifier is a string of 48-bit binary identifier, typically the MAC address of the AP inside the BSS.
Recall that we want in a coffee shop with wireless Internet network, but some will be found to the network name is very similar to several SSID. Why do they, in fact, there are things around. Will provide two SSID, is because one is available to the public, the password is public, but the quality is generally like the Internet, and the other is to provide internal staff access to quality will be better, but the password will not open it so it is generally in order to ensure the quality of internal staff online. According to the previous statement, one AP to build a set of services, then to set up such a network is not bound to need two AP it?
of course not. The device may also be configured Huawei VAP, WLAN provide differentiated services for users. VAP is called a physical entity in the virtual AP of a plurality of virtual AP, each AP is to be virtualized from a VAP, as a physical entity and provide each VAP AP function. VAP obvious advantages, multiple virtual AP work on the same hardware platform, improved hardware utilization; network administrator can set a different SSID for different VAP, security settings, QoS settings, policies and features, but also adds network flexibility.
See here, people ask Xiao Bian, you have talked about how to distinguish between a BSS in the ESS, but this is on a one AP ah, I know that ye are my pick of which VAP ah? In fact, VAP is also distinguished by a BSSID, but this is not the MAC address BSSID AP with the physical, but with the MAC address of VAP. While the MAC address and the MAC address of the VAP is actually the AP is a physical mapping relationship, see Fig.
VAP is a general first MAC is the same with the AP's MAC address, MAC address, VAP behind in the last AP of an order of the MAC plus one. Of course, BSSID ESSID not come easy to remember, after all, is a string of data out of order, so I will add a SSID for the VAP be easy to remember.
By the way, you can create on a 16 VAP AP.
Well, to sum up, the basic concepts of the current period to introduce are:
| concept |
Full name |
description |
| BSS |
The basic service set BSS (Basic Service Set) |
Basic wireless network service unit, generally consists of a plurality of wireless terminals and the AP. |
| ESS |
Extended Service Set ESS (Extend Service Set) |
A plurality of compositions with the same SSID BSS, BSS coverage limited to solve the problem. |
| SSID |
Service Set Identifier SSID (Service Set Identifier) |
Used to distinguish between different wireless networks. |
| ESSID |
Extended Service Set Identifier ESSID (Extended Service Set Identifier) |
Identifying one or a group of the wireless network, and the same SSID. |
| BSSID |
The basic service set identifier BSSID (Basic Service Set Identifier) |
VAP used to distinguish the same AP at the link layer, the same can also be used to distinguish the ESS BSS. |
| VAP |
Virtual access point VAP (Virtual Access Point) |
Out on the virtual AP function device business entity. Users can create different on a VAP AP to provide wireless access for different user groups. |
We want to know there is help WLAN, this issue will introduce here, the next issue we will introduce the line on the way and AP process for everyone, so stay tuned!
