The first thing we need to know is VoIP Servers or called them IP PBX. VoIP(Voice over Internet Protocol) servers are the primary servers that route the calls through VoIP devices or phones.
A standard phone system has a PBX within the office building and from this, all the telephones, call boxes, auto attendants go through this PBX. So this PBX is for phone systems, but when we are talking about VoIP( voice over IP), we are not talking about phones, but we speak of data devices that transmit the real-time audio communication.
VoIP servers or sometimes called IP PBX's is, of course, they use TCP/IP Ethernet network. So basically Ethernet is used by all the PBX phones.
So now instead of having a PBX phone with their world, now we have a phone system that resides on the same network as everything else like routers, switches, TCP/IP, computers, etc.
When we are talking about VoIP world, then we need to know about clients systems.
Why are we calling it Voice Over IP Server?
Because the Server is any Computer or machine that provides services to other devices or computers on the network, that's why we are calling IP PBX as Voice Over IP server.
So How it works?
VoIP server or IP PBX connects with the switch then switch connects with router then router will connect to the internet. Now all the telephones or clients on the system will then connect to the switch & that's how they connect to this VoIP server or IP PBX.
There are 3 Types of PBX available in the market.
The Traditional PBX is one that doesn't have any IP capabilities. These traditional PBX's are low-end systems with limited feature sets. Traditional PBX systems are entirely based on digital or analog handsets for end users.
An IP PBX is a system that is entirely based on Voice over IP. It does not support any analog devices natively, and all endpoints are Ip-based network devices.
Modern PBXs have the capabilities to function both as a traditional PBX with analog parameters and as an IP PBX through the purchase of expansion modules. These Hybrid PBX offers the most flexibility for an organization because they can connect many types of devices as a business transition to IP telephony.
How do you call in or how do you call out from a VoIP server or IP PBX?
The first way, if you are completely doing voice over IP, you can have something called voice over IP trunk from a provider. This is not an average provider like Verizon etc., but these are a different kind of providers that provide you with IP trunk lines, so your organization doesn't need standard telephone lines anymore. Your organization employees get all of their calls straight through the internet.
Now On the Voice over IP server or IP PBX, you can have connections that can connect you to standard phone lines from the external world. So Phone company sends their phone lines to your organization and that phone lines connects or plugged in your Voice Over IP server or IP PBX. Now if somebody makes the call, then it goes through your network then to your Voice over IP server, or IP PBX then goes out to the average trunk line.
In this Model, Your Voice over IP or IP PBX replaces the standard PBX. Typical PBX used to route all the telephone communications.
Now we are doing everything over IP and Ethernet network, so there is no need to install Voice Over IP or IP PBX in your organization, But you can be hosted voice over IP Server outside world. Just like Email server on the internet same like that. You can rent this from a company like on the sip.
These companies like On Sip, they will host your Voice Over IP Server or IP PBX. So all the Ip Phones and computers in the organization they connect to the switch, the switch connects to the router, and then they all log into this Hosted Voice Over IP Server or IP PBX. This hosting Voice Over Ip saves a lot of money.
These Voice Over IP server can be manufactured by companies like Lucent, Nortel, Mitel, Avaya, AT&T, etc. and those are proprietary of voice over IP servers or IP PBX's. Now some new companies out such as SIP X, Asterisk, Switchvox these are free open source Voice over IP servers.
What are VoIP Clients
Now when we were talking about devices or clients, there are two terms.
- Hard Phones
- Soft Phones
So what is the difference between Hard Phones and Soft Phones?
A Hard Phone is a telephone which provides telephone service in real time audio communication service. So a Voice Over IP telephone, it looks like a phone. A Hard Phone is a computer device that looks like a phone because when you try to configure this hard phones, you do this from a web interface.
For Example Polycom hard phones, to set those phones, we need to enter the IP address of that phone in the web browser and configure there.
A SoftPhone is a piece of software that you install on a computer to provide real-time audio communications Voice Over IP.
These devices either Hard Phones or SoftPhones connects to the account within the VoIP Server or IP PBX. In the VoIP server or IP PBX, we need to setup the user accounts.
For Example:- For Ext 107 USername is XXX and Passwd is XXYY and rest of the configuration. ( Extention, username and password are the most important configurations. Because when we go to the Voice Over IP client like iPod, Ipad, iPhone, etc. over there, you put this device is Extention 107 with username - XXXX and password - XXYY.
Now when that device comes on the network, it connects the Voice Over IP Server and tell the username and password to VoIP server and ask for Ext 107. Now Voice Over IP server confirms the username and password with that extension. If it matches, it gives that Extention to that particular device.
If somebody calls in from the outside world and they Dial Ext 107, then they will route to that device.
Voice Over IP Gateways
Gateways are used to connect different varieties of communication networks. So gateways are doing is converting Voice Over IP communications into ordinary telephone calls.
So if someone from the organization wants to call from there IP device outside to the normal telephone device then, the call goes to VoIP Server then it routed to a Gateway and then that gateway sends call out to the normal telephone lines because gateways has rj11 telephone connector on them where normal telephone lines plugged into these gateways.
Gateways are what connects these different type of infrastructure.
Till now we wrote or talk about the Voice Over IP servers or IP PBX's, we talk about VoIP Clients, we talked about gateways, these are the major components of the network that's what an organization need to buy to set up the environment. Now we need to discuss how these devices communicate with each other when someone makes a phone call to another person then how this communication was done.
Voice Over IP communications uses some protocols like TCP/IP; Apple uses Bonjour or net Bui, etc. Consider these protocols as a network language.
The standard protocol that we suggest to try is SIP( Session Initiation Protocol). Like Cisco SIP Phones, Polycom SIP Phones, Asterisk SIP Phones, Linksys SIP Phones. SIP is a protocol that lots of vendors have implemented. SIP resides on top of TCP/IP; this is an application of layer networking communication so that this SIP can ride on TCP/IP, UDP, and other protocols. SIP is a networking protocol, but it resides about TCP/IP.
It is how the voice traffic is encoded and encapsulated so when someone is talking over the phone, that communications have to get into little packets and sent down the network. A codec is what determines how this happens so if someone wants high-quality communication voice over IP traffic and have a lot of bandwidth then use a codec that uses a lot of bandwidth and gets high definition audio communication.
Now suppose the company has a bad network and low bandwidth then use lesser grade codec where communication sound is not as good as last time, but it will use less bandwidth. So Codec determines the quality of the sound conversations and how much bandwidth is used when someone in the company talks to somebody over this Voice Over IP network.
Network Latency and QOS( Quality of Service)
Quality of Service
Quality of service permits you to prioritize network traffic. Because now companies using their network not only for computer communications but also for a telephone for voice over IP communications. Companies have to be more careful that computer machines don't use all the company network bandwidth if they do then the company have no bandwidth left for telephone systems.
In Networking Equipment there are Switches and Routers. In Switches & Routers, you can prioritize network based on that company wants Voice Over IP traffic gets more importance than normal computer communications. Then Switches & Routers always makes sure that Companies Voice Over Ip Traffic gets High Bandwidth.
It's most important when an organization has Hosted Voice Over IP Server Environment. When your Voice Over IP Server is on the internet then all the computer and telephony devices etc. can connect to that Voice Over IP server through internet. The company needs to make sure that organizations internet network latency is not too high.
What is Mean by 'Network Latency'?
It means the time it takes when a bit is set from one place to the next when somebody starts talking and says 'Hi!'. How long it takes to those bits to go from that voice over IP Server all the way in your organization. A normal telephone call has a latency of 45milliseconds, and that is considered average Call Quality. In Voice Over IP world, they have 45 to 75 to 100-millisecond delay and still have nice or Okay communication with people on the other side.
If it is more than 100-Milliseconds, it will give a lot of trouble.