Seamless wifi roaming using capsman v2 in Mikrotik. Seamless Wi-Fi What is wifi roaming

Nowadays, various wireless devices are gaining popularity, for which high-speed access to the network is possible only via WiFi. These are Ipad / Iphone, and other mobile gadgets. When you want to organize WiFi access on an area of ​​30 sq. m., then installing an ordinary Dlink for 1200 rubles will solve all your problems, but if you have an area> 500 sq. m. and this is only one floor, this solution will not work. If you use ordinary access points or routers, then each router will have its own network name (unique SSID), or the routers will need to be spread far away so that the coverage areas do not overlap, and this will lead to the appearance of areas with very poor reception quality, or, generally, absent signal. About six months ago, I faced the same problem, the solution was found quickly enough - UniFi.

Example of Installing WiFi UniFi in a car wash with multiple buildings.

UniFi Provides Wireless Coverage to Arcadia California School District.

UniFi Provides Wireless Access to Upscale Hotels in Peru.

UniFi WiFi hotspots capabilities:

One network for all WiFi points.

Attractive design.

Easy to install, PoE.

Shows the coverage area and the location of the access points on the administrator display.

Centralized wireless network management.

Guest networks, without access to local network.

Creation of temporary passwords for guest users.

Automatic software updates on access points.

High scalability: up to 100 or more points.

Multiple wireless networks with differentiated access rights.

Separation of traffic of network users by VLAN.

Quick intranet roaming when switching between access points.

Tracking user traffic, identifying sources of increased network load.

Large coverage area.

The ability to generate one-time temporary passwords (relevant for public places: hotels, cafes, etc.)

Connecting points in repeater mode.

An overview of the features of the UniFi Controller is here.

Implementation of WiFi from Ubiquity in Peru hotels here (translation).

Hardware controller for Ubiquiti UniFi. UniFi Cloud Key.

How it looks in practice:

A software controller is installed on one of the computers in the network, on which all the settings of the wireless network are made.

All settings of points and network parameters are subsequently made through this controller. Below are a couple of screenshots of settings and appearance.

This is a building plan showing the locations of the points.

Setting up a guest network without access to corporate resources.

Monitoring of active clients.

Access point monitoring.

View from above.

The installation and configuration process is extremely simple:

1. Arrange the points and connect them to the local network, UniFi supports PoE so that only an ethernet socket is needed to connect them.

2. Install the software controller on any computer on the network, configure WiFi parameters networks, initialize the points, after initialization on the point, the settings from the controller will be applied, and the point will be ready for operation. Even when the controller is turned off, the settings on the points are saved.

In the corporate environment, WiFi is playing an increasingly prominent role and is playing an increasingly important role. You can connect a smartphone or tablet to WiFi, but, more importantly, a corporate phone, a mobile data collection terminal or an online cashier for accepting payments and printing receipts. It's good if the WiFi coverage area your business needs is small, and you can get by with an ordinary inexpensive access point, but what if wireless do you need to cover thousands of square meters on multiple floors? There are certainly options.

At first, it is possible to spawn multiple WiFi networks on multiple autonomous access points. The bad option is that such an economy is difficult and inconvenient to manage, when moving through the territory of the enterprise, some mobile devices you will have to switch between these networks manually, and, most importantly, all this will have to be explained to users who do not always understand IT well, and are simply unable to absorb these wisdom. There is only one plus for such a solution: it is cheap.

Secondly, can broadcast one WiFi network using the same type of autonomous access points with support for WDS technology. The main disadvantage of such a solution is that the overwhelming, absolute and unconditional majority of more or less affordable (up to 300 USD) access points of popular vendors operate ugly in WDS mode. Broadcasting can be lost and restored, connectivity between primary and dependent access points will be disrupted, and mobile devices will lose connection and, with it, their functional characteristics. So it's best to leave this option for real samurai.

Ideologically and technologically correct option is the use of a controller and dependent access points. This option is called "seamless WiFi". Its essence is that there can be many access points, and one centralized controller device is engaged in managing them and their broadcasting. Controller:

• monitors the status of subordinate access points, the load on them;
• adjusts signal strength and bandwidth depending on the number of clients and the nature of their work;
• independently restores areas unattended due to equipment failures by increasing the coverage area from nearby access points;
• provides web authentication and dynamic accounts to implement the so-called. " guest access"(for some controllers there are options like printers to generate and print temporary user credentials);
• provides fast roaming, with which you can freely roam, for example, with a WiFi phone between the coverage areas of different access points, without interrupting the conversation and without observing any interruptions in connection. At the same time, the controller in a timely manner "sets" on your device a signal from the closest access point.

Modern controllers allow connecting access points via WiFi in repeater mode (the so-called Mesh technology) without a cable connection to the network, and also provide integration with adjacent IT systems (for example, Active Directory, geolocation services, etc.).

What to build seamless Wi-Fi on

Our solution catalog has already carefully selected and described options for household, corporate and industry WiFi solutions:. And if you go "to the top", then the most good options Seamless Wi-Fi on the market is represented by the following vendors:

2. In the middle-end segment, another American manufacturer reigns. Relatively inexpensive, Cambium is also reliable and powerful.

Like Ruckus Unleashed, Cambium can also operate in network management mode without a controller. Cambium calls this ecosystem autoPilot and supports up to 32 access points on the network and up to 1000 wireless clients. Functionally, it is almost not inferior to the version with a controller, moreover, it does not require any investment, in addition to purchasing the access points themselves, there is no need to buy licenses, service contracts and their updates.

Need faster, higher, stronger? Please! Free cloud the cnMaestro controller already supports up to 4000 access points and up to 25000 wireless clients. The software can be installed completely free of charge on your own server, if beliefs do not allow using cloud solutions. Cambium's functionality is also all right: here you have centralized ecosystem management, geolocation services, analytics, airtime analysis, integration with related systems ... in general, everything that your heart desires.

The disadvantage of Cambium can be considered a relatively poor line of access points:. Although everything you need is present in it: there are access points with sector antennas, with support for 802.11ac Wave 2, MU-MIMO 4x4: 4, outdoor and indoor. In general, a complete gentleman's set is at your service!

3. In the budget segment, the competition is much higher, but we distinguish TP-LINK from other daring Chinese. This is the main and most interesting competitor to Ubiquiti (which will be discussed below), although such a comparison in 2019 for TP-LINK is not at all flattering.

First, let's take a look at the TP-LINK label itself: there are actually two of them. There is TP-LINK, which makes cheap home routers and plastic switches, and there is TP-LINK, which makes Enterprise line products - WiFi systems, Smart series switches, accessories for them. These are, in fact, 2 different companies, since there are no intersection points between these two directions neither in R&D, nor in production lines. And, for the sake of objectivity, Enterprise TP-LINK is significantly higher in quality than its younger brother, which specializes in products for SOHO.

Now to WiFi. TP-LINK has an Auranet CAP line- v currently in some oblivion (but this is temporary). The ceiling of the solution is 500 access points, 10,000 wireless clients. Controllers - hardware only, for 50 or 500 access points. Access points - in a rather old, "clumsy" design, but with support for honest seamless roaming in accordance with 802.11k / v standards, Beamforming, Band Steering, Airtime Fairness - in general, the set is completely complete. High Density on TP-LINK, of course, cannot be provided, but we have already served events for 200-300 users in one hall, and this did not cause complaints from customers.

TP-LINK's second ecosystem is called Omada, it introduces the EAP series access points. The controller - Omada Controller - is available in hardware (with a limit of 50 access points in the 1st network), but there is also a software version that can be installed on a server under Windows control or Linux. EAPs look modern and, of course, can do everything a self-respecting access point needs to be able to do in 2019.

4. Our next patient is Ubiquiti UniFi series. This is when you want nice and cheap. Moreover, it will be "beautiful" with Ubiquiti all the time, tk. they have everything subordinate to design: from packaging to design of management interfaces. And the design is truly one of the best in the industry. In general, Ubiquiti products are characterized by an extremely low price with sufficient high quality product as a whole.

The main disadvantage of Ubiquiti is that it still does not support truly seamless WiFi roaming in accordance with the IEEE standards, offering a proprietary implementation instead. Which works, well, let's say so-so. Therefore, if you need to organize flawless roaming of WiFi clients with voice or video applications, then Ubiquiti, sadly, is no longer for you. The same goes for High Density - this is not about Ubiquiti. In general, in the radio part, Ubiquiti is far from ideal, but thanks to a powerful component base, a very wide range of equipment and a correct marketing policy, they are still one of the most popular manufacturers of WiFi solutions. In Russia, Ubiquiti reveals 2 more significant shortcomings: the lack of official service and representation. The first means that the guarantee on the territory of the Russian Federation works a little better than nothing, and the second means that you will not have either technical support or certificates for equipment (which closes his way to state enterprises and to telecom operators).

Ubiquiti's advantage lies in their UniFi ecosystem, which now includes not only WiFi equipment, but also switches, routers, video surveillance, telephony, and more recently even some components of a smart home. Moreover, the management of all this economy is available through very beautiful and convenient applications (including mobile ones) that integrate with the Ubiquiti "cloud", i.e. You can "steer" the UniFi ecosystem from anywhere in the world, and this is without any dances with port forwarding, static IP addresses and other leapfrog. All in all, it's really convenient.

5. Mikrotik, Edimax, Wisnetworks, TG-NET, etc. We add the 5th item on this list only because the number 5 is prettier than 4. Or he has a better reputation. Objectively, the vendors listed here do not yet even reach the level of Ubiquiti (they may not be worse, but by the totality of factors of their perception by the market they are still not so significant), but they still occupy some niche on the market and enjoy some popularity.

We brag about it: we have extensive experience in deploying large Wi-Fi networks, we managed to "touch" live the most diverse solutions of the majority of specialized vendors, and we know their strengths and pitfalls. We are ready to apply our experience to the design and installation of wireless networks in your enterprise. - save your time and money!

We understand roaming technologies (Handover, Band steering, IEEE 802.11k, r, v) and conduct a couple of visual experiments that demonstrate their work in practice.

Introduction

Wireless group networks IEEE standards 802.11 is evolving extremely rapidly today, with new technologies, new approaches and implementations emerging. However, as the number of standards grows, it becomes more and more difficult to understand them. Today we will try to describe several of the most common technologies that are referred to as roaming (the procedure for reconnecting to a wireless network), and also see how seamless roaming works in practice.

Handover or "client migration"

By connecting to a wireless network, the client device (be it a smartphone with Wi-Fi, a tablet, laptop or PC equipped with a wireless card) will support wireless connection if the signal parameters remain at an acceptable level. However, when the client device moves, the signal from the access point with which the connection was initially established may weaken, which sooner or later will lead to a complete impossibility of data transmission. Having lost connection with the access point, the client equipment will select a new access point (of course, if it is within reach) and connect to it. This process is called handover. Formally, a handover is a migration procedure between access points initiated and performed by the client itself (hand over - "transfer, give, give up"). In this case, the SSIDs of the old and new points do not even have to match. Moreover, the client can fall into a completely different IP subnet.

To minimize the time spent on reconnecting a subscriber to media services, it is necessary to make changes both to the backbone wired infrastructure (make sure that the client's external and internal IP addresses do not change) and to the handover procedure described below.

Handover between APs:

1. Determine the list of potential candidates (access points) for switching.
2. Set the CAC-status (Call Admission Control - control of the availability of calls, that is, in fact, the degree of congestion of the device) of the new access point.
3. Determine the moment to switch.
4. Switch to new access point:

In IEEE 802.11 wireless networks, all handover decisions are made by the client side.

Source: frankandernest.com

Band steering

Band steering technology allows a wireless network infrastructure to transfer a client from one frequency band to another, usually a forced client switch from the 2.4 GHz band to the 5 GHz band. Although band steering is not directly related to roaming, we decided to mention it here anyway, as it is related to client device switching and is supported by all of our dual-band APs.

When can it be necessary to switch a client to a different frequency range? For example, such a need may be associated with the transfer of a client from an overloaded 2.4 GHz band to a more free and high-speed 5 GHz band. But there are other reasons as well.

It should be noted that on this moment there is no standard that strictly regulates the operation of the described technology, so each manufacturer implements it in its own way. However, the general idea remains roughly the same: access points do not advertise the SSID in the 2.4 GHz band to a client performing an active scan, if the activity of this client at a 5 GHz frequency has been noticed for some time. That is, access points, in fact, can simply keep silent about the availability of support for the 2.4 GHz band, if it was possible to establish the availability of client support for the 5 GHz frequency.

There are several modes of band steering operation:

1. Force connection. In this mode, the client, in principle, is not informed about the availability of support for the 2.4 GHz band, of course, if the client has support for the 5 GHz frequency.
2. Preferred connection. The client is forced to connect in the 5 GHz band only if the RSSI (Received Signal Strength Indicator) is above a certain threshold, otherwise the client is allowed to connect to the 2.4 GHz band.
3. Load balancing. Some clients that support both frequency bands connect to the 2.4 GHz network, and some to the 5 GHz network. This mode will not overload the 5 GHz band if all wireless clients support both frequency bands.

Of course, customers with support for only one frequency band will be able to connect to it without any problems.

In the diagram below, we tried to graphically depict the essence of the band steering technology.

Technologies and standards

Let's now return to the very process of switching between access points. In a typical situation, the client will maintain the existing association with the access point for as long as possible (as long as possible). Exactly as long as the signal level allows it to be done. As soon as a situation arises that the client can no longer maintain the old association, the switch procedure described earlier will start. However, handover does not happen instantly; it usually takes more than 100 ms to complete it, which is already a noticeable amount. There are several standards for radio resource management working group IEEE 802.11 aims to improve wireless reconnection times: k, r and v. In our Auranet line, 802.11k support is implemented on the CAP1200 access point, and in the Omada line on the EAP225 and EAP225-Outdoor access points, the 802.11k and 802.11v protocols are implemented.

802.11k

This standard allows a wireless network to tell client devices a list of neighboring access points and channel numbers on which they operate. The generated list of neighboring points makes it possible to speed up the search for candidates for switching. If the signal of the current access point weakens (for example, the client is removed), the device will look for neighboring access points from this list.

802.11r

Version r of the standard defines the FT - Fast Transition (Fast Basic Service Set Transition) function to speed up the client authentication procedure. FT can be used when switching a wireless client from one access point to another within the same network. Both authentication methods can be supported: PSK (Preshared Key) and IEEE 802.1X. Acceleration is carried out by storing encryption keys at all access points, that is, the client does not need to go through the full authentication procedure when roaming with the involvement of a remote server.

802.11v

This standard (Wireless Network Management) allows wireless clients to exchange service data to improve the overall performance of the wireless network. One of the most used options is BTM (BSS Transition Management).
Typically, a wireless client measures its connection to an access point to make a roaming decision. This means that the client has no information about what is happening with the access point itself: the number of connected clients, device boot, scheduled reboots, etc. Using BTM, the access point can send a request to the client to switch to another point with better working conditions , even with a slightly worse signal. Thus, the 802.11v standard is not directly aimed at speeding up the client switching process. wireless device however, when combined with 802.11k and 802.11r, it provides faster program performance and better Wi-Fi experience.

IEEE 802.11k in detail

The standard extends the capabilities of Radio Resource Management (RRM) and allows 11k-enabled wireless clients to query the network for a list of potential peer-to-peer access points. The access point informs clients of 802.11k support through a special flag in the Beacon. The request is sent in the form of a management frame called an action frame. The access point also responds with an action frame containing a list of neighboring points and their wireless channel numbers. The list itself is not stored on the controller, but is generated automatically upon request. It is also worth noting that this list depends on the location of the client and does not contain all possible access points of the wireless network, but only neighboring ones. That is, two wireless clients located in different locations will receive different lists of neighboring devices.

With such a list, the client device does not need to scan (active or passive) all wireless channels in the 2.4 and 5 GHz bands, which can reduce the use of wireless channels, that is, free up additional bandwidth. Thus, 802.11k allows you to reduce the time spent by the client for switching, as well as improve the process of choosing an access point for connection. Plus, eliminating the need for additional scans helps extend the battery life of the wireless client. It is worth noting that access points operating in two bands can inform the client about points from an adjacent frequency band.

We decided to visually demonstrate the operation of IEEE 802.11k in our wireless equipment, for which we used an AC50 controller and CAP1200 access points. One of the popular messengers with support for voice calls, running on a smartphone, was used as a traffic source Apple iPhone 8+, known to support 802.11k. The voice traffic profile is shown below.

As you can see from the diagram, the used codec generates one voice packet every 10 ms. The noticeable spikes and dips in the graph are due to the slight variation in latency (jitter) always present in Wi-Fi based wireless networks. We configured traffic mirroring to which both access points participating in the experiment are connected to. Frames from one access point got into one network card of the traffic collection system, frames from the second - into the second. In the received dumps, only voice traffic was sampled. Switching delay can be considered the time interval from the moment of traffic loss through one network interface until it appears on the second interface. Of course, the measurement accuracy cannot exceed 10 ms, which is due to the structure of the traffic itself.

So, without enabling support for the 802.11k standard, switching the wireless client took an average of 120 ms, while activating 802.11k allowed this delay to be reduced to 100 ms. Of course, we understand that although the switching latency was reduced by 20%, it still remains high. Further reduction in latency will be possible by using the 11k, 11r and 11v standards together, as is already implemented in the home series of wireless equipment.

However, 802.11k has another up its sleeve: timing to switch. This opportunity is not so obvious, so we would like to mention it separately, demonstrating its work in real conditions. Typically, the wireless client waits until the last, maintaining the existing association with the access point. And only when the characteristics wireless channel become very bad, the procedure for switching to a new access point starts. With the help of 802.11k, you can help the client with the switch, that is, offer to make it earlier, without waiting for significant signal degradation (of course, we are talking about a mobile client). Our next experiment is devoted to the moment of switching.

Qualitative experiment

Let's move from the sterile laboratory to the real customer's site. In the room, two 10 dBm (10 mW) APs were installed, a wireless controller and the necessary supporting wired infrastructure. The layout of the premises and the locations of the access points are presented below.

The wireless client moved around the room making a video call. First, we turned off support for the 802.11k standard in the controller and set the places where the switch took place. As you can see from the picture below, this happened at a considerable distance from the "old" access point, near the "new" one; in these places the signal became very weak, and the speed was barely enough to transmit video content. There were noticeable lags in voice and video when switching.

Then we turned on 802.11k support and repeated the experiment. The switchover now took place earlier, in places where the signal from the "old" access point was still strong enough. There were no lags in the voice or video. The switching location has now moved approximately halfway between the access points.

In this experiment, we did not set ourselves the goal of elucidating any numerical characteristics of switching, but only qualitatively demonstrating the essence of the observed differences.

Conclusion

All described standards and technologies are designed to improve the client's experience of using wireless networks, make it more comfortable to work, reduce the influence of annoying factors, and increase the overall performance of the wireless infrastructure. We hope that we were able to demonstrate clearly the benefits that users will receive after implementing these options in wireless networks.

Is it possible to live in an office without roaming in 2018? In our opinion, this is quite possible. But, having tried once to move between offices and floors without losing the connection, without having to re-establish a voice or video call, without being forced to repeat what was said or ask again, it will no longer be realistic to refuse.

P.S. but this is how you can make seamlessness not in the office, but at home, which will be discussed in more detail in another article.

When it is necessary to cover large areas with a WiFi signal, to improve the performance, reliability and speed of the WiFi network, seamless roaming technology can help us with this. Seamless WiFi is a technology of transition from the coverage area of ​​one point WiFi access to the coverage area of ​​another WiFi hotspot, without significant data loss. Think of it as a handover of a client device from one access point to another. Thus, you can create seamless WiFi coverage over large areas: apartments, restaurants, hotels, warehouses, airports, country houses, stadiums, cities.

The main features when creating seamless WiFi are:

• Calculation of the capacity (power) of the network depending on the expected number of network users.
• Planning WiFi coverage based on capacity and resiliency.
• Inspection of the air for the presence of interference, multiple reflections, obstacles and other reasons affecting the propagation of the radio signal.
• Planning a frequency plan for better noise immunity and network performance.
• Determination of installation sites for active equipment, taking into account all factors.

List of possible requirements for equipment when organizing seamless WiFi:

1. Outdoor WiFi hotspot capability... It is necessary when covering outdoor areas, as well as when using in rooms with a climate different from room climate (warehouses, freezers, saunas, swimming pools, etc.)
2. Availability of models with different radiation patterns(sector, omnidirectional), for the possibility of creating complex schemes WiFi coverage.
3. Availability of transmitter power control, for the possibility of creating networks with high capacity.
4. Easy to mount and secure access points... PoE power capability, which eliminates the need for additional power lines to power devices. Compatible with a variety of client devices.
5. Centralized management of all access points... Possibility of managing and billing traffic of subscriber devices. Ease of network scalability.

All these characteristics are met by equipment from MikroTik and UBIQUITI, which can provide you with high-quality seamless WiFi in different conditions: from your apartment to your city.