Hi!
My name is Anton Datsenko and I am responsible for the development of corporate solutions and services in the Beeline Business division. Today I will tell you how we use redundancy technologies and a balancer in MultiSIM, for which clients such a product is more important than it seems at first glance, and a little about networks in general.
I will make a reservation right away that in the post we will talk about B2B clients. Because for an ordinary subscriber, a communication reservation is a smartphone with two SIM cards.
But seriously, the approaches here are a bit similar. It is worth talking about the importance of redundant communication channel approximately in the same plane as about the important data backup. You donβt have a backup - this is basically bad (but temporarily). If you have a backup, that's already much better. And if you not only make backups, but also check just in case how well everything is restored from them, itβs already very good.
A stable network for most enterprises, including even small and medium-sized businesses, is, without jokes, a guarantee of normal operation. Because a lot is tied to the network - the performance of online stores, and work with databases in offline stores, and the operation of online cash registers and pinpads. In general, if there is no network, you will not be able to pay for the goods normally, they will not be able to knock out a check at the online checkout, and so on and so forth.
What is a balancer and why is it needed
A balancer (also known as a traffic aggregator) is an analogue of a router, in which there are from 2 to 4 SIM cards (depending on the model the customer needs). With the help of partners, we install equipment for corporate clients and set up a connection. This can be either a direct connection through a balancer over LTE networks, or through a device with redundancy. There is also an option with a VPN tunnel, but I will talk about it separately in the next post.
There are two SIM cards
So. Each load balancer combines the channel bandwidths supplied from SIM cards and works with the aggregation server. The server is located in our network, at the junction of our network and the partner's network, and we receive a working channel. Visually, this is a router, most often Mikrotik (yes, yes), on which custom firmware is installed, we took OpenWrt as a basis and rewrote it quite seriously.
And here already 4
More than 10 years ago, media companies in the United States thought about the need for such devices. Television there is developed more seriously than in our country, and special attention is paid to live broadcasts and direct broadcasts from the scene. The quality of the picture and sound is important, this is also a component of a competitive advantage, so there are a number of companies that have special technology patents in terms of how to correctly break a high-quality video frame into fragments, shove it all into a cellular network, on the side of the studio from these fragments again to collect an excellent picture, and not a flock of jackals, and show it to the viewer. And all this, which is important, with a minimum delay in time.
So they use special devices that have a set of all kinds of SIM cards on board at once, allowing you to drive a high-quality video stream from the scene to the studios.
In our country, the television market itself is built a little differently, therefore, this decision did not take root, because it turned out to be both expensive and not the most popular.
But for business, balancers for 2-4 SIM cards turned out to be just the way.
Who benefits
It's good if you have excellent network administrators in your company, and everything is great with the provider. But there are times when redundancy saves the usual work order.
Most of the clients who actively use our product are companies that have difficulties with a wired communication channel. There are many reasons for this - it may be a monopoly provider in a business center, it may be the location of the store not in a building in which there is a wired channel, but in a small extension to it, in which this channel is no longer there. Let's say a small covered market within walking distance of residential buildings. And pulling a line from the main FOCL to such an extension is either difficult or unprofitable.
And then there are clients with mobile offices or seasonal businesses, including event organizers. Our balancer (read - a router with SIM cards and special software) is a small box that you can quickly take with you, plug it in on the spot, and everything will work. Let's say there is an insurance company that needs to deploy its offices in new places a lot and often. Until such a new customer service office is fully connected to the network with all the documents, a week may pass. If you use a MultiSIM balancer, it will be enough to throw it into the office with the very first delivery of furniture and paper for printers, after which they will simply turn it on and immediately get a working network with secure access to corporate resources.
As soon as the office is connected to a full-fledged wired network, the balancer can simply be removed and postponed until the next such event, or left as a spare in case of a network failure.
Banks. The vast majority of ATMs are connected to the network via mobile communications; inside such an ATM there is a whistle with a SIM card, which provides communication. This is usually enough with a margin, because the exchange of processing data in terms of traffic is actually a penny, and no one will download torrents from ATMs. If only for the sake of interest. In addition, connecting an ATM via a mobile network makes it a little more mobile: within a shopping center, for example, it can be quickly moved from place to place, focusing only on the presence of a nearby socket, and not on an Internet cable.
While there are pros, there will be cons. The main one is that there is only one SIM card in the whistle. Therefore, if this particular operator has problems, then the ATM temporarily fails and cannot contact the bank. Banks do not like this, firstly, because of the loss of money (every hour of ATM downtime is a non-illusory loss of funds), and secondly, such downtime does not have a very good effect on customer loyalty. You came to the shopping center to the ATM urgently to withdraw money, and he is stupid.
You and I now understand that with a high probability this could be a problem with the network, but for the end person who expects crisp cash in a minute, the bank itself will always be the source of the problem. Since the ATM of a particular bank does not work = a stupid bank, that's all they have. The balancer, in which case, will switch the network to the second SIM card. The situation when two different operators simultaneously lay down in the city at once occurs much less frequently than temporary breakdowns with one.
Plus, do not forget about the creation of situational centers and operational headquarters for emergency services and government agencies. It is critical for them to deploy a secure network in order to be able to fully work with all their internal databases from anywhere, be it a field or a swamp. Now the process of deploying such a network looks like this:
- emergency services arrive at the scene and unload;
- install USB whistles with SIM cards of operators;
- looking for a fixed point of presence of operators (for this they have contacts of all operators for such a case);
- forward the channel (either just to the Internet, or immediately to their network);
- impose their special equipment on top of all this;
- deploy the network.
It seems that there are not many points. But the process can take a couple of days. With the balancer, everything fits in 5 minutes. I took it out, turned it on, and that's it. You donβt need to think about the balance (for our part, we ourselves keep our finger on the pulse, regardless of which SIM cards of which operators the client uses), plus you can not keep the device in greenhouse conditions, but generally throw it on the roof of a mobile trailer, where it catches better - IP67 protection allows this to be done.
Reservation Features
Devices that provide redundancy, in general, work on a similar principle as the balancer, but with a couple of features. Firstly, there are always only two sims. Secondly, they work in turn, that is, only one is always active, there is no gluing of channels.
Installation from the client side looks just as simple - a router is installed into which a special Python script is loaded, and it works in LTE modem mode, if necessary, switching from the first SIM to the second (the script does this automatically depending on the operation of certain triggers ). An additional bonus here is not only the work as an LTE modem outright, but also work via cable. That is, if you have access via a cable network, you can plug a cable into the router and work on it. If something goes wrong with the cable connection, the LTE channel will turn on. It turns out such a reservation of the cable signal if desired.
Here we did everything ourselves, without involving partners or third-party contractors.
The key characteristic of redundant operation is VPN only. Yes, we are building the entire network through a VPN tunnel. All SIM cards installed in such devices are in a single VPN network, so if you remove it from the device and insert it into a familiar smartphone for testing, it will not work. The backup device through the VPN network lays a tunnel to our gateway, where the clients go. In principle, there is no difference for the end client, except for the size of the final unfragmented packet.
At the same time, we keep the same IP and the corresponding settings for a specific client. Works via cable, switches to SIM cards, decided to move the device somewhere - the IP will be the same.
There are two more useful features for corporate clients.
First, Wi-Fi. The device works as a limited network router, a kind of point between the operator and the client, while it can also work as a familiar client router according to a predetermined set of rules. Nothing prevents you from throwing Wi-Fi on top of it so that a corporate client can distribute fast Wi-Fi to its employees. I note that in this scenario we are talking about a corporate work network, and not public Wi-Fi with SMS authorization, as in a cafe and so on.
Secondly, there is a built-in SIP-gateway. The router has a small PBX that can work with our cloud PBX and allow the client to connect analog phones directly to the router. At the end of this year, we plan to deploy a full-fledged service, multisim reservation + Wi-Fi + cloud PBX, while all this is in the test. There is an idea to provide such a service in the format of two entities - either directly from our OATS, or from the PBX that the client already has.
Let's say the client has his own IP VPN network without Internet access and his own PBX on Asterisk, he gives us his settings, and we set everything up so that the client receives a router that has two subscriber lines at once, Wi-Fi and IP VPN access.
How to connect
Here on these pages.
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In the meantime, we are conducting active load testing. I will post the results separately as well. If you have any questions about the operation of our MultiSIM - ask in the comments, I will answer.
Source: habr.com