FastTrack Training. "Network Basics". "The Basics of Telephony." Part 1. Eddie Martin. December 2012
About a year ago, I noticed an interesting and fascinating series of lectures by Eddie Martin, which, thanks to its history and real-life examples, as well as its tremendous learning experience, is amazingly comprehensible and allows you to gain an understanding of quite complex technologies.
We continue the cycle of 27 articles based on his lectures:
')
01/02: “Understanding the OSI Model” Part 1 / Part 2
03: "Understanding the Cisco Architecture"
04/05: “The Basics of Switching or Switches” Part 1 / Part 2
06: "Switches from Cisco"
07: "Area of ​​use of network switches, the value of Cisco switches"
08/09: "Basics of a Wireless LAN" Part 1 / Part 2
10: "Products in the field of wireless LAN"
11: The Value of Cisco Wireless LANs
12: Routing Basics
13: "The structure of routers, routing platforms from Cisco"
14: The Value of Cisco Routers
15/16: “The Basics of Data Centers” Part 1 / Part 2
17: "Equipment for data centers"
18: "The Value of Cisco in Data Centers"
19/20/21: "The Basics of Telephony" Part 1 / Part 2 / Part 3
22: "Cisco Collaboration Software"
23: The Value of Collaboration Products from Cisco
24: "The Basics of Security"
25: "Cisco Security Software"
26: "The Value of Cisco Security Products"
27: "Understanding Cisco Architectural Games (Review)"
And here is the nineteenth of them.
Today we will talk about cooperation. This is a real religious war. And Cisco played a big role in this religious war, in fact, the company started it. Let's talk about how we have moved from IP telephony to unified communication, about cooperation in this area. This process consisted of many different parts and solutions.
As I said, in 1997, John Chambers was at the forefront of Cisco cooperation, and the whole story is connected with his name. So in 1997, John, speaking to a group of investors, said two things to them. The first is that long distance communication should be free.
Most people do not remember that at that time this type of communication was very expensive, about 80-90 cents per minute. You picked up the phone and said, “Hi, how are you? Watched football? Like children"? And for that you received huge bills, sometimes these bills contained errors in the account. People paid attention to this, they looked at their accounts and were horrified, so the cheaper communication was very important for people.
So, Chambers said that long-distance communication should be free of charge and that voice and data should become one. The idea of ​​combining voice and data was born as soon as John said it.
At that time there were no blogs or anything like that on the Internet, but I had telecommunication magazines at my home; this was the only type of electronic communication. I received these magazines because I was a “telephony guy” and thought about voice transmission issues. In essence, John also thought that there was no way to broadcast voice over the network, because the transfer of information would interfere with this, and there is no way to resolve this situation.
Most people used hubs, they did not see the advantages of switches, but John decided to develop a more efficient and more reasonable method of communication for all networks. He possessed the vision of a global company development strategy.
Cisco began to acquire companies that developed technologies centered around the main product, switches and routers, and then acquired a small company called Celsius.
Celsius was located in Dallas, Texas, and was involved in video creation. However, they could not broadcast video over the network using the H323 protocol. It was not as flexible as SIP, and customer devices did not support it. However, this protocol was a working business model for information transfer, and we decided to make it easier by “cutting out” video transmission. The result was a “thin client” that our phones could use. We called it IP-PBX, the corporate telephony system, where VoIP has become the main channel for voice transmission. The small boxed server did the same thing as the big PBX server.
When they saw this device at Nortel, they said that if they bought us, they would first of all put our technology somewhere on the far shelf, under the table or in the trash. However, it so happened that Cisco acquired the company, and Nortel needed our technology in 1998-99. By the way, they released the ugliest phones I've ever seen, I never put their SP12 devices on my desktop. I think they took their design from the 1940s. I met older phones that looked much nicer than these devices.
In general, we had a strategic vision of how we evolve. The first thing we did was to create data centers, since it was easier to draw on a clean “blackboard”, where we had no competition. Our competitors Siemens, Alcatel, Nortel, Avaya - they all invested heavily in traditional telephony, and I will never say anything bad about PBX technology, because it played its role longer than other technologies that I saw, and did it very OK.
However, the requirements have changed, we have changed them for new needs, and therefore IP telephony has "taken off". Did she have any exceptional features? Not. Was it significantly cheaper? Also no. People saw our devices and said that it was too expensive. Yes, we have gone through such times and will tell you why it was expensive then. But it met the requirements of the business. IP telephony meant mobility, it provided the use of business-required applications that appeared at that time, which the PBX could never provide.
So, let's talk about PBX technology. We have a voice network, that is, a phone connected to a box called PBX, which is connected to a PSTN box, and one to another PBX located in a branch office of the company, and it is connected to another phone. This is all the same network that locks onto the PSTN PSTN. There are many users and customers here, and this system is spread all over the world.
At that time we started to create a separate network. It consisted of a computer, a switch, a router, another router, a switch and another computer, it was called a WAN (Wide Area Network). You see, this is a completely different network.
At that time, I worked as a wired communication engineer at Blue Cross & Blue Shield and managed both types of networks. We had an advanced telephone system, thanks to the Avaya G3R PBX, and a good data transfer structure, but they existed independently. I had two different management systems, in two different organizations, which I called "bowling" and "golf." There was the same difference between telephony and computers as between a bowling ball and a golf ball. I am very good at bowling, I can score 140-150 points, while in golf I am simply terrible, it is extremely difficult for me to send the ball in the right direction. So I worked in two completely different organizations and dealt with two completely different areas. What do you think, which of these technologies better understood the needs of the business, corresponded to the needs of the business? Correct, telephone connection. Computers were needed only for data exchange, they performed a local function and had a narrow specialization. My IP specialists sat behind the doors around their switches and routers, and the rest of the staff knew only that they were sitting behind closed doors. And telephony experts were completely different, like one guy named Ronnie, very sociable, but he could not always joke with the client correctly, without rudeness, dirty jokes or political incorrectness. But he knew better about where “the business is going. He was more developed because he communicated with people who need voice communication, he listened to their wishes, why it was needed and why, he had a much bigger outlook than “IT people”. Our “telephone” guys were more busy with customers than IT guys. The second ones were constantly sitting near their servers, while telephone operators ran on customer orders, pulled cables, rearranged telephone sets, that is, they were on the move all the time. They were considered a more significant part of the business, as it was in reality.
I believe that everything that we have in the lower infrastructure, we stole from the top. Therefore, it was much easier for telephonists to delve into the wisdom of a computer network than for children from computer networks to delve into the wisdom of telephony. And in the past, I remember a lot of people who moved from telephony to the network and vice versa.
So, in the late 90s, early 2000s, we created a technology called VoIP - “voice over IP”.
How do we usually call? We are removing the phone ... second, I will now draw here a DIAL Plan dialer in front of the PBX. What does it do? Assigns all numbers to the first digit, which indicates the geographical identity of the telephone network. In Europe it is 0, and in the USA it is 9. What do you do if you want to order pizza by phone? You first dial the number 9. That's what the DIAL Plan is for, and now with this nine PBX you can make an outgoing call to the network. Next in the phone number there is a country code, these are 3 digits, then the area code and the last ones are followed by the actual digits of the phone number we are calling. The call goes to the PSTN, where there are routing tables that have all the phone numbers on Earth — the code of any country, city, etc. Then the call goes to another PBX and to the called phone. And for this process you are charged.
In the late 80s, users knew how expensive such telephone technology cost them. A minute of international calls cost more than $ 1.25.
And what are you paying for in the IP network? What are you paying WAN for? Only for bandwidth. Can I put a PSTN inside a WAN? Probably, I can, but for this you need a device that would combine both of these networks and turn them into one common network.
This device is a router! I place certain hardware and software in it so that the router can connect to the PBX. Thus, we go from one phone to another first, bypassing the PSTN.
Now we make a call like this: we pick up the phone, dial the number, it goes through PBX and DIAL, then it goes to the first router and through the WAN to the second, from there to another PBX and to the called phone. What does this router do? He says PBX "yes or no." Having received a signal from him, he answers whether he is currently able to receive a call or not. Therefore, we must limit the number of calls by applying the "early" version of QoS.
QoS encapsulates voice, turning it into VoATM (voice over ATM), VoFR (voice over Frame Relay), VoIP (voice over IP).
Cisco came up with special routers for this 3810, I really like them, they were created in the mid-90s, in 1995, specifically to provide this technology. I bought literally a ton of these small boxes, inside of which were all the necessary modules for voice over the network. How did they work? They needed to allocate a certain bandwidth, for example, for 2 calls. If the 3rd call came from the PBX, the router informed that it was already engaged in a conversation, and then the third call was made on the upper path - via the PSTN, of course, with payment for the conversation, but the call passed. It was a very convenient scheme.
Routers acted as input and output controllers. Before the router went the data, then he needed to give priority to voice data, then again the data. If the voice transmission was active, the router reduced the data flow and gave priority to voice transmission. The difference between voice and data transmission is that voice transmission has a limited time for the subscriber to receive it, ordinary data does not have such a strict limitation. The router played a key role here, helping to save money to users. This technology is called voice over IP. Due to this, the business process was directed around the public switched telephone network.
We began to compete in the telephony market with VoIP technology. I personally earned money by traveling between our branches and installing routers with VoIP support. When Cisco came up with IP telephony, she said she wanted to use voice as an application. And the greatest thing I could do was educate my clients, so I sold IP telephony very successfully. I did not say to them with a clever look: “now we will remove all this your junk and install this,” no, I spoke the same language with them. If they thought that IP telephony is a risky business, I explained to them that this technology has a future, we give them the telephony equipment of the next generation today and they do not need to immediately abandon the previous one. We are not going to force you to skip over technology, we are gradually improving your business.
I came to the telecom departments of companies, and the boss said to me: "who the hell are you?" I have never seen you before, probably, you are the guy who sold golf shirts to my employees and is now burnt out "? I answered him:" No, my name is Eddie, I am from Cisco and I am here to talk about the future of telephony As you know, the merging of two networks has already happened, and I want to know how you imagine the further development of this technology, what do you expect from it? I have no tail, no horns, I am not the devil tempting you, I just want to talk about cooperation. ”Then I told him:“ Let me show you what you want! ” oval him PBX, which has five functions.
The first is the Trunk card, which allows you to connect to the PSTN outside the building. It provides a digital (PRI) or analog connection to the external network we use. Next we have a Station-card to which digital and analog phones and modems are connected. The third component is the central processor CPU. If you have a decent-sized company, it will need two CPUs.
They are needed to supply and ensure the operation of the connected devices. Suppose you have a new employee, and you gave him a phone. You need to add to the list of devices the type of this phone, then supply it with a phone number, all the necessary functions, for example, the ability to respond to voice mail messages, DIAL Plan, routing table (before routers appeared, PBX contained routing tables).
They were especially critical when you use two providers, MCI and AT & T, to communicate with the PSTN. MCI provides cheap calls in the local network, and the second provides you with cheap calls over long distances. And you sent a call, depending on where it is, to the network of the desired telephony provider. This was called price routing.
The fourth component is shared resources, Shared resources. Here are two power sources and a dial tone card. She sends you a dial tone when you pick up the phone. First, your phone sends a signal to the CPU, it sends it down to the tone card, and it answers you with a beep that everything is in order. This is called the “supervisor beep” - if you picked up the phone and did not hear it, then your phone does not work. Then the DTMF receiver is located immediately - it receives the tone dialing in the form of beeps, which are returned to it from your phone, and tells the CPU which digits correspond to which number you are calling. This is how it works thanks to the cards that are inside the PBX.
The shared resources also include the Ring Tone card, which accepts a dial tone, meaning that the phone has received an incoming call. Why does your phone ring, what makes it do it? It turns out that we have another call generator, or Ring Voltage Generator. It gives a frequency of 20 Hz and a voltage of 90 V, which make the phone to which your call came to ring.
In order for this whole system to work, you need to lay wires, because all the electrical signals of this network are transmitted through the wires. These wires literally entangle everything around. It was funny, we loved to play a little mean trick when someone was messing around with connecting the phone to send a call. Bah! :) But it was funny when you were on the side of the sender, not the recipient. I did it so many times, but I received a discharge many times as well.
Finally, the fifth component, which binds together all 4 components, is called the TDM bus. It simultaneously processes many incoming and outgoing calls.
I will give this example. Imagine that we have a company with 400 employees and our own PBX. So the salesman comes to you and says: “Eddie, I want to sell you a PBX that supports 878 phones.” But I have only 400 people, but if I want to double the number of staff, I will need this station, and I buy it. How does he know that I can connect to this PBX 878 phones? The station provides a bandwidth of 64 kbps, it estimates how many kilobits all the cards occupy, how many subscribers can be connected to more than the channel provides (oversell degree), and receives a capacity of 878 subscribers. Great, but after buying a PBX, he says: “And now you still have to buy phones from us”! But I do not want to buy his phones, I have my own! Turns out I can't use them. Can we use Avaya phones on Nortel PBX equipment? No, It is Immpossible.
I once worked for American Airlines, a big company that belonged to the North American PBX user group. They were located in Florida, it was in winter, and in winter there is beautiful weather. They sent us a survey - not by email, but by regular mail, in an envelope. There was a request to name for 5 reasons why you like your telephone service provider and why you do not like it. Then they introduced everyone to the results of this survey. And the first place was taken by the dissatisfaction with the proprietary nature of the PBX, that it was impossible to connect phones of other manufacturers. I went to them and saw a Siemens phone there. It was a great phone, known both in Europe and in the USA. One of the most "reasonable" phones with which I had to meet. But I could not use it! Why? Because we did not use Siemens PBX, since it was only compatible with such phones. This situation was observed in the late 80s everywhere. And this led to the fact that if you do not reckon with users, they cease to reckon with you. And the company, which behaved in this way, for two years, dropped from first to third place.
In 2000, when Nortel's PBX appeared with digital phones, you also could not use phones from other manufacturers, because you were tied to your telephone network, to a telephony service provider.
So, we bought a PBX for 878 phones. , : «, Voice Messanger, , - ». 652 . , , . : «»! « » « ». ? , , - , .
Blue Cross & Blue Shield , , , . – , , . : «, , , , PBX»! , , : «, , , ». , , , : «, , , »!
, PBX. .
- 80-, 90- . 30 40 , 18-22% . Blue Cross & Blue Shield, PBX G3. , . , , , $1,25. , . ! . 1995 $433, - - $800, . Cisco , , .
1995 , 3- PBX Blue Cross & Blue Shield 978 . : «, , PBX! »! … , , .
. , , : «, … PBX 5.12. , »! : «, PBX». : «, , »! : « , »? : « , 5.12 6.14. , , »!
. – 5.1 5.4, 5.4 5.8, , 5.8 6.2. , … , , «» , 48 5 , . , . , , , : « - , , »!
, . , PBX , . .
, Cisco IP-. , PBX. , , . Cisco , , , .
Blue Cross & Blue Shield, Cisco, Carolina Power and Light. . PBX Rockwell ASD (application service devices) , . . , ? 70 ! , - .
Cisco, PSTN? , , PBX PSTN? Trunk , VG, Voice Gate « ». PBX, Station, «» , , PoE — « Ethernet».
, , , 23 PoE.
CPU c , – - CM (call manager).
– Rington .wav. IP- CM.
QoS, PBX – TDM. , , , – , «». , , «» . – ! , .
, .
, dial-up? . , dial-up? , – , . PBX , , .
Cisco , , Nortel, , . , .
H.323 SCCP — Skinny Client Control Protocol. .
, ? Cisco , . , . PBX? , . PBX $412. .
Cisco , , , , Cisco .
, . , , , IT- , , IP-. , : « ? , „“ ? ». , «». : «, , , , ».
«» , , PSTN, , , - , , . , , PBX, , , PBX, , .
Continued:
FastTrack Training. "Network Basics". « ». 2. . December 2012
Thank you for staying with us. Do you like our articles? Want to see more interesting materials? Support us by placing an order or recommending to friends, 30% discount for Habr users on a unique analogue of the entry-level servers that we invented for you: The Truth About VPS (KVM) E5-2650 v4 (6 Cores) 10GB DDR4 240GB SSD 1Gbps $ 20 or how to share the server? (Options are available with RAID1 and RAID10, up to 24 cores and up to 40GB DDR4).
Dell R730xd 2 times cheaper? Only we have 2 x Intel Dodeca-Core Xeon E5-2650v4 128GB DDR4 6x480GB SSD 1Gbps 100 TV from $ 249 in the Netherlands and the USA! Read about How to build an infrastructure building. class c using servers Dell R730xd E5-2650 v4 worth 9000 euros for a penny?
We continue the cycle of 27 articles based on his lectures:
')
01/02: “Understanding the OSI Model” Part 1 / Part 2
03: "Understanding the Cisco Architecture"
04/05: “The Basics of Switching or Switches” Part 1 / Part 2
06: "Switches from Cisco"
07: "Area of ​​use of network switches, the value of Cisco switches"
08/09: "Basics of a Wireless LAN" Part 1 / Part 2
10: "Products in the field of wireless LAN"
11: The Value of Cisco Wireless LANs
12: Routing Basics
13: "The structure of routers, routing platforms from Cisco"
14: The Value of Cisco Routers
15/16: “The Basics of Data Centers” Part 1 / Part 2
17: "Equipment for data centers"
18: "The Value of Cisco in Data Centers"
19/20/21: "The Basics of Telephony" Part 1 / Part 2 / Part 3
22: "Cisco Collaboration Software"
23: The Value of Collaboration Products from Cisco
24: "The Basics of Security"
25: "Cisco Security Software"
26: "The Value of Cisco Security Products"
27: "Understanding Cisco Architectural Games (Review)"
And here is the nineteenth of them.
FastTrack Training. "Network Basics". "The Basics of Telephony." Part 1. Eddie Martin. December 2012
Today we will talk about cooperation. This is a real religious war. And Cisco played a big role in this religious war, in fact, the company started it. Let's talk about how we have moved from IP telephony to unified communication, about cooperation in this area. This process consisted of many different parts and solutions.
As I said, in 1997, John Chambers was at the forefront of Cisco cooperation, and the whole story is connected with his name. So in 1997, John, speaking to a group of investors, said two things to them. The first is that long distance communication should be free.
Most people do not remember that at that time this type of communication was very expensive, about 80-90 cents per minute. You picked up the phone and said, “Hi, how are you? Watched football? Like children"? And for that you received huge bills, sometimes these bills contained errors in the account. People paid attention to this, they looked at their accounts and were horrified, so the cheaper communication was very important for people.
So, Chambers said that long-distance communication should be free of charge and that voice and data should become one. The idea of ​​combining voice and data was born as soon as John said it.
At that time there were no blogs or anything like that on the Internet, but I had telecommunication magazines at my home; this was the only type of electronic communication. I received these magazines because I was a “telephony guy” and thought about voice transmission issues. In essence, John also thought that there was no way to broadcast voice over the network, because the transfer of information would interfere with this, and there is no way to resolve this situation.
Most people used hubs, they did not see the advantages of switches, but John decided to develop a more efficient and more reasonable method of communication for all networks. He possessed the vision of a global company development strategy.
Cisco began to acquire companies that developed technologies centered around the main product, switches and routers, and then acquired a small company called Celsius.
Celsius was located in Dallas, Texas, and was involved in video creation. However, they could not broadcast video over the network using the H323 protocol. It was not as flexible as SIP, and customer devices did not support it. However, this protocol was a working business model for information transfer, and we decided to make it easier by “cutting out” video transmission. The result was a “thin client” that our phones could use. We called it IP-PBX, the corporate telephony system, where VoIP has become the main channel for voice transmission. The small boxed server did the same thing as the big PBX server.
When they saw this device at Nortel, they said that if they bought us, they would first of all put our technology somewhere on the far shelf, under the table or in the trash. However, it so happened that Cisco acquired the company, and Nortel needed our technology in 1998-99. By the way, they released the ugliest phones I've ever seen, I never put their SP12 devices on my desktop. I think they took their design from the 1940s. I met older phones that looked much nicer than these devices.
In general, we had a strategic vision of how we evolve. The first thing we did was to create data centers, since it was easier to draw on a clean “blackboard”, where we had no competition. Our competitors Siemens, Alcatel, Nortel, Avaya - they all invested heavily in traditional telephony, and I will never say anything bad about PBX technology, because it played its role longer than other technologies that I saw, and did it very OK.
However, the requirements have changed, we have changed them for new needs, and therefore IP telephony has "taken off". Did she have any exceptional features? Not. Was it significantly cheaper? Also no. People saw our devices and said that it was too expensive. Yes, we have gone through such times and will tell you why it was expensive then. But it met the requirements of the business. IP telephony meant mobility, it provided the use of business-required applications that appeared at that time, which the PBX could never provide.
So, let's talk about PBX technology. We have a voice network, that is, a phone connected to a box called PBX, which is connected to a PSTN box, and one to another PBX located in a branch office of the company, and it is connected to another phone. This is all the same network that locks onto the PSTN PSTN. There are many users and customers here, and this system is spread all over the world.
At that time we started to create a separate network. It consisted of a computer, a switch, a router, another router, a switch and another computer, it was called a WAN (Wide Area Network). You see, this is a completely different network.
At that time, I worked as a wired communication engineer at Blue Cross & Blue Shield and managed both types of networks. We had an advanced telephone system, thanks to the Avaya G3R PBX, and a good data transfer structure, but they existed independently. I had two different management systems, in two different organizations, which I called "bowling" and "golf." There was the same difference between telephony and computers as between a bowling ball and a golf ball. I am very good at bowling, I can score 140-150 points, while in golf I am simply terrible, it is extremely difficult for me to send the ball in the right direction. So I worked in two completely different organizations and dealt with two completely different areas. What do you think, which of these technologies better understood the needs of the business, corresponded to the needs of the business? Correct, telephone connection. Computers were needed only for data exchange, they performed a local function and had a narrow specialization. My IP specialists sat behind the doors around their switches and routers, and the rest of the staff knew only that they were sitting behind closed doors. And telephony experts were completely different, like one guy named Ronnie, very sociable, but he could not always joke with the client correctly, without rudeness, dirty jokes or political incorrectness. But he knew better about where “the business is going. He was more developed because he communicated with people who need voice communication, he listened to their wishes, why it was needed and why, he had a much bigger outlook than “IT people”. Our “telephone” guys were more busy with customers than IT guys. The second ones were constantly sitting near their servers, while telephone operators ran on customer orders, pulled cables, rearranged telephone sets, that is, they were on the move all the time. They were considered a more significant part of the business, as it was in reality.
I believe that everything that we have in the lower infrastructure, we stole from the top. Therefore, it was much easier for telephonists to delve into the wisdom of a computer network than for children from computer networks to delve into the wisdom of telephony. And in the past, I remember a lot of people who moved from telephony to the network and vice versa.
So, in the late 90s, early 2000s, we created a technology called VoIP - “voice over IP”.
How do we usually call? We are removing the phone ... second, I will now draw here a DIAL Plan dialer in front of the PBX. What does it do? Assigns all numbers to the first digit, which indicates the geographical identity of the telephone network. In Europe it is 0, and in the USA it is 9. What do you do if you want to order pizza by phone? You first dial the number 9. That's what the DIAL Plan is for, and now with this nine PBX you can make an outgoing call to the network. Next in the phone number there is a country code, these are 3 digits, then the area code and the last ones are followed by the actual digits of the phone number we are calling. The call goes to the PSTN, where there are routing tables that have all the phone numbers on Earth — the code of any country, city, etc. Then the call goes to another PBX and to the called phone. And for this process you are charged.
In the late 80s, users knew how expensive such telephone technology cost them. A minute of international calls cost more than $ 1.25.
And what are you paying for in the IP network? What are you paying WAN for? Only for bandwidth. Can I put a PSTN inside a WAN? Probably, I can, but for this you need a device that would combine both of these networks and turn them into one common network.
This device is a router! I place certain hardware and software in it so that the router can connect to the PBX. Thus, we go from one phone to another first, bypassing the PSTN.
Now we make a call like this: we pick up the phone, dial the number, it goes through PBX and DIAL, then it goes to the first router and through the WAN to the second, from there to another PBX and to the called phone. What does this router do? He says PBX "yes or no." Having received a signal from him, he answers whether he is currently able to receive a call or not. Therefore, we must limit the number of calls by applying the "early" version of QoS.
QoS encapsulates voice, turning it into VoATM (voice over ATM), VoFR (voice over Frame Relay), VoIP (voice over IP).
Cisco came up with special routers for this 3810, I really like them, they were created in the mid-90s, in 1995, specifically to provide this technology. I bought literally a ton of these small boxes, inside of which were all the necessary modules for voice over the network. How did they work? They needed to allocate a certain bandwidth, for example, for 2 calls. If the 3rd call came from the PBX, the router informed that it was already engaged in a conversation, and then the third call was made on the upper path - via the PSTN, of course, with payment for the conversation, but the call passed. It was a very convenient scheme.
Routers acted as input and output controllers. Before the router went the data, then he needed to give priority to voice data, then again the data. If the voice transmission was active, the router reduced the data flow and gave priority to voice transmission. The difference between voice and data transmission is that voice transmission has a limited time for the subscriber to receive it, ordinary data does not have such a strict limitation. The router played a key role here, helping to save money to users. This technology is called voice over IP. Due to this, the business process was directed around the public switched telephone network.
We began to compete in the telephony market with VoIP technology. I personally earned money by traveling between our branches and installing routers with VoIP support. When Cisco came up with IP telephony, she said she wanted to use voice as an application. And the greatest thing I could do was educate my clients, so I sold IP telephony very successfully. I did not say to them with a clever look: “now we will remove all this your junk and install this,” no, I spoke the same language with them. If they thought that IP telephony is a risky business, I explained to them that this technology has a future, we give them the telephony equipment of the next generation today and they do not need to immediately abandon the previous one. We are not going to force you to skip over technology, we are gradually improving your business.
I came to the telecom departments of companies, and the boss said to me: "who the hell are you?" I have never seen you before, probably, you are the guy who sold golf shirts to my employees and is now burnt out "? I answered him:" No, my name is Eddie, I am from Cisco and I am here to talk about the future of telephony As you know, the merging of two networks has already happened, and I want to know how you imagine the further development of this technology, what do you expect from it? I have no tail, no horns, I am not the devil tempting you, I just want to talk about cooperation. ”Then I told him:“ Let me show you what you want! ” oval him PBX, which has five functions.
The first is the Trunk card, which allows you to connect to the PSTN outside the building. It provides a digital (PRI) or analog connection to the external network we use. Next we have a Station-card to which digital and analog phones and modems are connected. The third component is the central processor CPU. If you have a decent-sized company, it will need two CPUs.
They are needed to supply and ensure the operation of the connected devices. Suppose you have a new employee, and you gave him a phone. You need to add to the list of devices the type of this phone, then supply it with a phone number, all the necessary functions, for example, the ability to respond to voice mail messages, DIAL Plan, routing table (before routers appeared, PBX contained routing tables).
They were especially critical when you use two providers, MCI and AT & T, to communicate with the PSTN. MCI provides cheap calls in the local network, and the second provides you with cheap calls over long distances. And you sent a call, depending on where it is, to the network of the desired telephony provider. This was called price routing.
The fourth component is shared resources, Shared resources. Here are two power sources and a dial tone card. She sends you a dial tone when you pick up the phone. First, your phone sends a signal to the CPU, it sends it down to the tone card, and it answers you with a beep that everything is in order. This is called the “supervisor beep” - if you picked up the phone and did not hear it, then your phone does not work. Then the DTMF receiver is located immediately - it receives the tone dialing in the form of beeps, which are returned to it from your phone, and tells the CPU which digits correspond to which number you are calling. This is how it works thanks to the cards that are inside the PBX.
The shared resources also include the Ring Tone card, which accepts a dial tone, meaning that the phone has received an incoming call. Why does your phone ring, what makes it do it? It turns out that we have another call generator, or Ring Voltage Generator. It gives a frequency of 20 Hz and a voltage of 90 V, which make the phone to which your call came to ring.
In order for this whole system to work, you need to lay wires, because all the electrical signals of this network are transmitted through the wires. These wires literally entangle everything around. It was funny, we loved to play a little mean trick when someone was messing around with connecting the phone to send a call. Bah! :) But it was funny when you were on the side of the sender, not the recipient. I did it so many times, but I received a discharge many times as well.
Finally, the fifth component, which binds together all 4 components, is called the TDM bus. It simultaneously processes many incoming and outgoing calls.
I will give this example. Imagine that we have a company with 400 employees and our own PBX. So the salesman comes to you and says: “Eddie, I want to sell you a PBX that supports 878 phones.” But I have only 400 people, but if I want to double the number of staff, I will need this station, and I buy it. How does he know that I can connect to this PBX 878 phones? The station provides a bandwidth of 64 kbps, it estimates how many kilobits all the cards occupy, how many subscribers can be connected to more than the channel provides (oversell degree), and receives a capacity of 878 subscribers. Great, but after buying a PBX, he says: “And now you still have to buy phones from us”! But I do not want to buy his phones, I have my own! Turns out I can't use them. Can we use Avaya phones on Nortel PBX equipment? No, It is Immpossible.
I once worked for American Airlines, a big company that belonged to the North American PBX user group. They were located in Florida, it was in winter, and in winter there is beautiful weather. They sent us a survey - not by email, but by regular mail, in an envelope. There was a request to name for 5 reasons why you like your telephone service provider and why you do not like it. Then they introduced everyone to the results of this survey. And the first place was taken by the dissatisfaction with the proprietary nature of the PBX, that it was impossible to connect phones of other manufacturers. I went to them and saw a Siemens phone there. It was a great phone, known both in Europe and in the USA. One of the most "reasonable" phones with which I had to meet. But I could not use it! Why? Because we did not use Siemens PBX, since it was only compatible with such phones. This situation was observed in the late 80s everywhere. And this led to the fact that if you do not reckon with users, they cease to reckon with you. And the company, which behaved in this way, for two years, dropped from first to third place.
In 2000, when Nortel's PBX appeared with digital phones, you also could not use phones from other manufacturers, because you were tied to your telephone network, to a telephony service provider.
So, we bought a PBX for 878 phones. , : «, Voice Messanger, , - ». 652 . , , . : «»! « » « ». ? , , - , .
Blue Cross & Blue Shield , , , . – , , . : «, , , , PBX»! , , : «, , , ». , , , : «, , , »!
, PBX. .
- 80-, 90- . 30 40 , 18-22% . Blue Cross & Blue Shield, PBX G3. , . , , , $1,25. , . ! . 1995 $433, - - $800, . Cisco , , .
1995 , 3- PBX Blue Cross & Blue Shield 978 . : «, , PBX! »! … , , .
. , , : «, … PBX 5.12. , »! : «, PBX». : «, , »! : « , »? : « , 5.12 6.14. , , »!
. – 5.1 5.4, 5.4 5.8, , 5.8 6.2. , … , , «» , 48 5 , . , . , , , : « - , , »!
, . , PBX , . .
, Cisco IP-. , PBX. , , . Cisco , , , .
Blue Cross & Blue Shield, Cisco, Carolina Power and Light. . PBX Rockwell ASD (application service devices) , . . , ? 70 ! , - .
Cisco, PSTN? , , PBX PSTN? Trunk , VG, Voice Gate « ». PBX, Station, «» , , PoE — « Ethernet».
, , , 23 PoE.
CPU c , – - CM (call manager).
– Rington .wav. IP- CM.
QoS, PBX – TDM. , , , – , «». , , «» . – ! , .
, .
, dial-up? . , dial-up? , – , . PBX , , .
Cisco , , Nortel, , . , .
H.323 SCCP — Skinny Client Control Protocol. .
, ? Cisco , . , . PBX? , . PBX $412. .
Cisco , , , , Cisco .
, . , , , IT- , , IP-. , : « ? , „“ ? ». , «». : «, , , , ».
«» , , PSTN, , , - , , . , , PBX, , , PBX, , .
Continued:
FastTrack Training. "Network Basics". « ». 2. . December 2012
Thank you for staying with us. Do you like our articles? Want to see more interesting materials? Support us by placing an order or recommending to friends, 30% discount for Habr users on a unique analogue of the entry-level servers that we invented for you: The Truth About VPS (KVM) E5-2650 v4 (6 Cores) 10GB DDR4 240GB SSD 1Gbps $ 20 or how to share the server? (Options are available with RAID1 and RAID10, up to 24 cores and up to 40GB DDR4).
Dell R730xd 2 times cheaper? Only we have 2 x Intel Dodeca-Core Xeon E5-2650v4 128GB DDR4 6x480GB SSD 1Gbps 100 TV from $ 249 in the Netherlands and the USA! Read about How to build an infrastructure building. class c using servers Dell R730xd E5-2650 v4 worth 9000 euros for a penny?
Source: https://habr.com/ru/post/351220/
All Articles