Choosing a Voice VoIP Gateway
Everyone who came across IP telephony had to come up with the choice of a VoIP gateway to connect an IP PBX to the telephone network, to an existing PBX, analog phone, and so on. When choosing a VoIP gateway, the question always arises - which gateway to choose and how do they differ from each other. Actually, I wanted to tell about this in this article - how one gateway differs from another and what you should pay attention to when choosing. Naturally, I cannot give the final recipe, which gateway is required to buy, since ultimately any choice consists of a number of factors: requirements, desires and prices. Here I want to describe the main features that are worth paying attention to, and already you will need to decide for yourself what is more important for you. So, let's begin:
Today, more and more companies are using IP telephony and unified communications. In turn, manufacturers also do not stand still and offer more and more IP telephony solutions. But we must not forget that the SIP, about which now does not speak, except that only the lazy is not one standard, but a set of recommendations, where RFC 3261 is only a small part. When a manufacturer writes that he supports call transfer or call hold, this does not mean that this service will work with your IP PBX. For example, your PBX supports the call transfer method of RFC 3892 (REFERED-BY), and the gateway supports the method of RFC 3515 (REFER). On the one hand, both options work according to the standard (more precisely, recommendations), but as a result they are not compatible with each other. Moreover, there is no one to complain here. In this regard, it is always required to check not a set of functionality that is available on a particular VoIP gateway, but a set of standards that supports the gateway. And so that equipment manufacturers would not say that everything is compatible and SIP is unified - in practice this is not the case, as each manufacturer strives to create its own unique service. And This leads to the fact that manufacturers create their own standards and these standards become only more and the problem of compatibility does not become easier. Because of this, when purchasing a VoIP gateway, it is better to clarify on the site of the station manufacturer, with which gateways your IP PBX works and what are the limitations. Separately, we can mention support for the H.323 protocol, which is still in use. I will not go deeper into H.323 compatibility in this article, since the protocol is no longer developed and not a single manufacturer develops it, but perhaps only supports it. There is also TDM compatibility. It would seem that TDM and analog telephony are standardized so that compatibility problems should not be, but in practice it turns out there are a lot of questions, starting with the support of pulse dialing (and stations that do not support tone dialing still exist in large numbers, not to mention already on the phone), the correct definition of tones in the line and ending with the various fields of ISDN. But it’s also not worthwhile to dwell on this topic, as practice shows, those people who have such problems take what they could get to work on tests and know about these problems themselves.
A VoIP gateway is an infrastructure device, and its peculiarity is a physical limitation in performance. If data networks are growing and more and more efficient equipment appears that supports 100 Mbps, 1000 Mbps, 1 Gbps and so on. That in telephony through one analog port one line is connected with one simultaneous connection, the E1 stream has 31 time slots and supports 30 or 31 simultaneous connections, depending on the type of signaling. This has not changed for many years and will never change. On the other hand, there is VoIP, where everything changes quickly and dynamically - a new IP-PBX appears, new services and standards appear, unified communications come and so on. If with network equipment, when new services appear, you usually do not have a question why you need more bandwidth on your IP channel and according to this you change routers / switches. That is why when changing IP-PBX or just updating IP-PBX you need to change the VoIP gateway is not clear. After all, you do not change the type of connection to the telephone network and the IP-PBX still supports SIP. But it turns out that the manufacturer of the VoIP gateway took your model out of production and created a new model and does not support the old one. And sometimes the life of the model can be 1-2 years, which is negligible for such a conservative world as telephony. I agree that the equipment is becoming obsolete, production technologies are changing, but for me the period of support for the VoIP gateway is a very important factor.
This is more of a requirement for analog gateways with FXS ports. One of the advantages of IP telephony is that the VoIP gateway can be placed as close as possible to the place where the phone is installed. But the closer the equipment is to the installation site, the higher are the installation requirements:
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Probably, each of us faced the problem that the quality of assembly or the quality of plastic from particularly cheap manufacturers leaves much to be desired. But if the build quality can simply lead to the fact that somewhere unscrew the screw or damage ports when pulling the cables (naturally random). That quality of plastic, which is so much loved to save, can turn out to be the worst. As I wrote earlier, the cooling is quite an important factor in the VoIP gateway and if the quality of the plastic is good or the steel case is used, only the device will break when the device burns out. But if the quality of the plastic leaves much to be desired, then besides the fact that it may smell during work, what it can do during a fan breakdown, I think it’s not worth it. And if we take into account the fact that the equipment is not located in the server room, but somewhere under someone else’s table, the consequences can be completely unpredictable.
Returning to the topic of the fact that the installation site of the equipment may be different, the requirements for the remote control and monitoring increase. And if manufacturers of small devices tend to support TR-069, to control the telecom operator. That for installation in the infrastructure of the enterprise always requires SNMP and even better the possibility of a console cable.
This is probably the factor that is very important, but to which everyone does not pay attention when choosing, but only during operation. When the gateway is tested, it usually passes in “sterile” conditions. When the gateway is put on the network, it turns out that the quality is not as we would like - there is an echo, extra noise, faxes do not go (although T38 is supported and faxes are checked). And the reason, as a rule, is not that the wrong codec is used or the telephone set is changed, the reason lies in the gateway itself and its DSP processor. Actually, how well that DSP processor and its code can convert the RTP stream that comes from the IP side, with all the problems of delays, jitter, losses into an analog or digital signal of a synchronous stream and the voice quality will depend on it. Also, a very important factor is the function of noise reduction, echo cancellation, control of the signal level, determination of pauses and other, purely voice, telephone functions. If earlier this functionality was assigned completely to the telephone exchange and all this was done in one place, now it is all done on the VoIP end devices. And the quality of voice in your VoIP network will strongly depend on the quality of the DSP. When choosing this parameter, it’s rather subjective, but in practice, users feel it very objectively.
As well as manufacturers of IP-PBX, manufacturers of VoIP gateways tend to provide additional services to their users. Here you can write for a long time about the services provided by one or another manufacturer, but I, naturally, will not do this. Let me just say that I advise you to pay attention to these services when choosing a gateway, since they can be very interesting for your infrastructure and will give it to you, something that no other vendor will give. Who knows, maybe this is exactly what will be the main advantage for you.
From the above, I would like to add that you should not consider the main criterion - the price and performance of the basic call, and pay more attention to the little things. They make a quality product really high quality. And then it turns out, like many operators, the cost of services falls more slowly than the quality of these same services.
1. Compatibility
Today, more and more companies are using IP telephony and unified communications. In turn, manufacturers also do not stand still and offer more and more IP telephony solutions. But we must not forget that the SIP, about which now does not speak, except that only the lazy is not one standard, but a set of recommendations, where RFC 3261 is only a small part. When a manufacturer writes that he supports call transfer or call hold, this does not mean that this service will work with your IP PBX. For example, your PBX supports the call transfer method of RFC 3892 (REFERED-BY), and the gateway supports the method of RFC 3515 (REFER). On the one hand, both options work according to the standard (more precisely, recommendations), but as a result they are not compatible with each other. Moreover, there is no one to complain here. In this regard, it is always required to check not a set of functionality that is available on a particular VoIP gateway, but a set of standards that supports the gateway. And so that equipment manufacturers would not say that everything is compatible and SIP is unified - in practice this is not the case, as each manufacturer strives to create its own unique service. And This leads to the fact that manufacturers create their own standards and these standards become only more and the problem of compatibility does not become easier. Because of this, when purchasing a VoIP gateway, it is better to clarify on the site of the station manufacturer, with which gateways your IP PBX works and what are the limitations. Separately, we can mention support for the H.323 protocol, which is still in use. I will not go deeper into H.323 compatibility in this article, since the protocol is no longer developed and not a single manufacturer develops it, but perhaps only supports it. There is also TDM compatibility. It would seem that TDM and analog telephony are standardized so that compatibility problems should not be, but in practice it turns out there are a lot of questions, starting with the support of pulse dialing (and stations that do not support tone dialing still exist in large numbers, not to mention already on the phone), the correct definition of tones in the line and ending with the various fields of ISDN. But it’s also not worthwhile to dwell on this topic, as practice shows, those people who have such problems take what they could get to work on tests and know about these problems themselves.
2. Duration of support
A VoIP gateway is an infrastructure device, and its peculiarity is a physical limitation in performance. If data networks are growing and more and more efficient equipment appears that supports 100 Mbps, 1000 Mbps, 1 Gbps and so on. That in telephony through one analog port one line is connected with one simultaneous connection, the E1 stream has 31 time slots and supports 30 or 31 simultaneous connections, depending on the type of signaling. This has not changed for many years and will never change. On the other hand, there is VoIP, where everything changes quickly and dynamically - a new IP-PBX appears, new services and standards appear, unified communications come and so on. If with network equipment, when new services appear, you usually do not have a question why you need more bandwidth on your IP channel and according to this you change routers / switches. That is why when changing IP-PBX or just updating IP-PBX you need to change the VoIP gateway is not clear. After all, you do not change the type of connection to the telephone network and the IP-PBX still supports SIP. But it turns out that the manufacturer of the VoIP gateway took your model out of production and created a new model and does not support the old one. And sometimes the life of the model can be 1-2 years, which is negligible for such a conservative world as telephony. I agree that the equipment is becoming obsolete, production technologies are changing, but for me the period of support for the VoIP gateway is a very important factor.
3. Installation requirements and type of cooling
This is more of a requirement for analog gateways with FXS ports. One of the advantages of IP telephony is that the VoIP gateway can be placed as close as possible to the place where the phone is installed. But the closer the equipment is to the installation site, the higher are the installation requirements:
- Passive cooling: probably, no one likes when his fan is noisy under his ear. But this is not the only problem. You will not check the fan operation every day, and support for remote monitoring of the fan on such models is usually not provided, and if the fan fails, the gateway itself will break down quickly enough. And it will not be a warranty case. It should be understood that the gateway with FXS ports requires electricity for each port, and from this technical solution for cooling, with increasing ports, it only becomes more difficult.
- Working environment: Naturally, the gateway in this case is not in the server room, and you cannot control the temperatures that are in the room. From here it is also important to look at those operating temperatures that the manufacturer indicates more closely.
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4. Build quality
Probably, each of us faced the problem that the quality of assembly or the quality of plastic from particularly cheap manufacturers leaves much to be desired. But if the build quality can simply lead to the fact that somewhere unscrew the screw or damage ports when pulling the cables (naturally random). That quality of plastic, which is so much loved to save, can turn out to be the worst. As I wrote earlier, the cooling is quite an important factor in the VoIP gateway and if the quality of the plastic is good or the steel case is used, only the device will break when the device burns out. But if the quality of the plastic leaves much to be desired, then besides the fact that it may smell during work, what it can do during a fan breakdown, I think it’s not worth it. And if we take into account the fact that the equipment is not located in the server room, but somewhere under someone else’s table, the consequences can be completely unpredictable.
5. Management and monitoring
Returning to the topic of the fact that the installation site of the equipment may be different, the requirements for the remote control and monitoring increase. And if manufacturers of small devices tend to support TR-069, to control the telecom operator. That for installation in the infrastructure of the enterprise always requires SNMP and even better the possibility of a console cable.
6. DSP
This is probably the factor that is very important, but to which everyone does not pay attention when choosing, but only during operation. When the gateway is tested, it usually passes in “sterile” conditions. When the gateway is put on the network, it turns out that the quality is not as we would like - there is an echo, extra noise, faxes do not go (although T38 is supported and faxes are checked). And the reason, as a rule, is not that the wrong codec is used or the telephone set is changed, the reason lies in the gateway itself and its DSP processor. Actually, how well that DSP processor and its code can convert the RTP stream that comes from the IP side, with all the problems of delays, jitter, losses into an analog or digital signal of a synchronous stream and the voice quality will depend on it. Also, a very important factor is the function of noise reduction, echo cancellation, control of the signal level, determination of pauses and other, purely voice, telephone functions. If earlier this functionality was assigned completely to the telephone exchange and all this was done in one place, now it is all done on the VoIP end devices. And the quality of voice in your VoIP network will strongly depend on the quality of the DSP. When choosing this parameter, it’s rather subjective, but in practice, users feel it very objectively.
7. Additional features
As well as manufacturers of IP-PBX, manufacturers of VoIP gateways tend to provide additional services to their users. Here you can write for a long time about the services provided by one or another manufacturer, but I, naturally, will not do this. Let me just say that I advise you to pay attention to these services when choosing a gateway, since they can be very interesting for your infrastructure and will give it to you, something that no other vendor will give. Who knows, maybe this is exactly what will be the main advantage for you.
From the above, I would like to add that you should not consider the main criterion - the price and performance of the basic call, and pay more attention to the little things. They make a quality product really high quality. And then it turns out, like many operators, the cost of services falls more slowly than the quality of these same services.
Source: https://habr.com/ru/post/190550/
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