The Equivalence of BSSID and SSID

SSID Short for Service Set Identifier, a 32-character unique identifier attached to the header of packets sent over a WLAN that acts as a password when a mobile device tries to connect to the BSS. The SSID differentiates one WLAN from another, so all access points and all devices attempting to connect to a specific WLAN must use the same SSID. A device will not be permitted to join the BSS unless it can provide the unique SSID. Because an SSID can be sniffed in plain text from a packet it does not supply any security to the network.

ESSID The Extended Service Set ID (ESSID) is the name of the network you want to access. It is used to identify different wireless networks.

BSSID The BSSID is a 48bit identity used to identify a particular BSS (Basic Service Set) within an area. In Infrastructure BSS networks, the BSSID is the MAC (Medium Access Control) address of the AP (Access Point) and in Independent BSS or ad hoc networks, the BSSID is generated randomly.

If you need to replace the SSID (Service Set Identifier) of your wireless network, you can do so by accessing your router's settings.

Basic Service Set Identifier or BSSID in short is the AP’s physical or MAC address, which is 48-bit long hexadecimal numbers. Just like your computer’s MAC address.

As a wireless user, you don’t see BSSID but it’s included in wireless packages/frames.

Most of the time, there are different BSSIDs on an access point for each WLAN configured on a radio.

By convention, an access point’s Mac address is used as a BSS identifier (BSSID).

So if you know the MAC address, you know what the BSSID is—and, since all packets contain the originator’s BSSID, you can trace a packet.

This works fine for an access point that has a radio and WLAN configured.

If you have an access point with 2 radios and 32 WLANs configured on each, you would have 64 BSSIDs plus the base BSSID of the access point.

Individual access points are assigned to unique 64 MAC address blocks to accommodate multiple BSSIDs.

Since multiple WLANs can coexist in single airspace, each WLAN needs a unique name.

This is the so-called Service Set Identifier (SSID) of your network, which is also referred to as “Network Name.”

As a user, you only care about the SSID.

APs broadcast their SSID by default in their service area.

They use a unique character string used to identify an AP.

You can name it by any natural language like English, Spanish, or Chinese.

Your device can see the SSIDs for all available networks; so when you click on a wireless icon, it will bring up the SSIDs that the device recognizes, so you can then connect.

The SSID keeps packets within the correct WLAN, even when overlapping WLANs are present.

However, there are typically multiple access points on each WLAN, so there must be a way to identify those access points and their associated clients.

One Service Set can be extended by adding more APs.

This is called the Extended Service Set or ESS.

Every AP broadcasts the same SSID to its users.

Last but not least, is the ESSID or Extended Service Set Identifier.

There’s formally no such thing as an “ESSID” in 802.11 standards.

Thus, you can just use the same SSID for ESSID-shared networks.

В этой статье (сокращенный перевод [1]) объясняется смысл трех терминов Wi-Fi: SSID, BSSID, ESSID.

Service set identification (SSID) это имя, которое понятно и читаемо для пользователей basic service set (BSS).

SSID может занимать от 0 до 32 байт, точки доступа публикуют это имя, представляя себя публичными и распознаваемыми.

Basic service set identification (BSSID) это MAC-адрес беспроводного сетевого адаптера точки доступа.

ESS (extended service set, расширенный набор служб) относится к basic service sets (BSS) или беспроводным сетям, у которых такие же SSID.

Здесь мы используем режим роуминга ESSID; это работает так, что когда у нас есть две беспроводные точки доступа (WAP) в двух разных местах (например, на разных этажах организации, или даже на разных домах города), и когда станция перемещается между ними, ваше соединение устанавливается без необходимости переключения между точками доступа.

Другими словами, все эти беспроводные точки доступа в ESS, которые имеют одинаковые имена (ESSID) и станция Wi-Fi (клиент WLAN, например ноутбук или смартфон) будет подключаться к той точке доступа, от которой приходит более сильный сигнал, и клиент WLAN при этом ничего не заметит.

ESSID and BSSID are just their IDs respectively.

My understanding is that ESSID is the name of the access point, which can be changed.

On the other hand, BSSID is a numeric ID of the access point (something like the MAC address of the router).

For instance, on my college campus we have many different access points with the same name, but BSSIDs are different for each router.

You can list networks with their respective ESSID and BSSID with nmcli dev wifi.

Or for cleaner output you can do nmcli -f SSID,BSSID dev wifi.

Also with iwlist, for example: sudo iwlist wlp2s0 scan.

Types of Service Sets: BSS (Basic Service Set) ESS (Extended Service Set).

ESSs consist of one or more infrastructure-BBSs (the usual mode).

They are associated with multiple access points.

All the APs' beacons will broadcast the same SSID but different BSSIDs.

It involves roaming.

The user gets connected to the AP that has maximum strength.

Usually, nearby BSSs broadcast on different channels/frequencies.

SSID: Network name (friendly, text, even with non-ISO basic Latin characters, up to 64 characters).

Could be hidden (no broadcast).

Sometimes "wrongly" called ESSID since it might group a set of APs under one name, but there is formally no such thing as an ESSID in the 802.11 standards.

BSSID: MAC address of the access point, it uniquely identifies each one.

You can use these commands to get a lot of information of nearby networks: nmcli -f NAME,SSID,SSID-HEX,BSSID,MODE,CHAN,FREQ,RATE,SIGNAL,BARS,SECURITY,WPA-FLAGS,RSN-FLAGS,DEVICE,ACTIVE,IN-USE,DBUS-PATH device wifi.

Or just nmcli device wifi or iwlist wlp2s0 scanning.

But since commands from net-tools and wireless-tools packages seem to be deprecated in Linux you could try to get familiar with the modern iw from iproute2 package: iw dev wlp2s0 scan dump.