Category Archives: tutorial

Tutorial: 5G Wireless

One place 5G base stations will be deployed is on streetlights

Now that 4G cellular mobile is settled, talk is now turning to 5G.

The first thing to know about 5G is that there are currently no standards, no detailed agreement on what exactly it will be. But we have a number of general indicators to guide the discussion:

1. 5G will employ radio frequencies well above what is currently used for cellular.
The current frequency bands for 3G/4G cellular top out at about 2.6 GHz. Proposals for frequency bands for 5G include “millimeter wave” bands, that is, wavelengths varying between 1 and 10 mm, which correspond to frequencies between about 30 and 300 GHz. No doubt, in the future, there will be unified 5G systems with variations operating in all frequency bands; but the current emphasis is on new technology in the millimeter wave bands.

2. 5G will provide very high bit rates.
With carrier frequencies at 30 GHz and above, very wide frequency bands around those center frequencies can be employed, allowing the radio frequency modems to achieve high numbers of bits per second. In addition, Multiple-Input, Multiple-Output (MIMO) designs can implement massive parallel communications, radically increasing the capacity available to a user. Initial designs and trials have measured 5 Gb/s (5,000 Mb/s). No doubt, this will be pushed beyond 10 Gb/s.

3. Initially, 5G will not be a replacement for 4G.
At millimeter wave frequencies, in-building penetration and refraction around obstacles is poor, and the atmosphere attenuates (diminishes) the signal to the point that line-of-sight between the antennas is necessary, and useful transmission range is measured in the hundreds of meters (yards). This means that the first deployments of 5G will be in environments where base stations can be closely spaced.

One application for all this bandwidth is traffic control: going beyond today’s standalone self-driving vehicles to vehicles communicating with each other and with traffic control systems, with base stations deployed on street lights as suggested by the picture.

We’ll be covering 5G on the last day of BOOT CAMP.

more info

Tutorial: SIP Trunking

One of the newest service offerings from carriers is SIP Trunking.

Like many, many other pieces of jargon in the business, many people would like to understand just what exactly it is.

SIP is an acronym for Session Initiation Protocol. This is a standards-based method of setting up Voice over IP telephone calls.

A key thing to know about Voice over IP phone calls is that once the call is set up and two people are talking, their telephones exchange IP packets with digitized speech in them directly.

One person’s telephone creates an IP packet and puts the IP address of the other person’s telephone in the destination address field. This packet is forwarded by routers directly to the other person’s phone.

To be able to do this, it is necessary to know what the other person’s IP address is!

This is the main function performed by SIP: it is an assistant to enable a caller to find out the IP address of the called party’s telephone, so they can send packets with digitized speech to that person’s phone.

Trunking is a term that has been generally used in the telecom business in the past to mean communication between telephone switches. Trunks connect CO switches, toll centers and other switches in the PSTN.

PBX trunks connect an organization’s private switch to a CO switch.

SIP Trunking is a term invented by the marketing department to mean to mean “native communication of SIP call setup messages and Voice over IP traffic between an organization’s locations, with a Service Level Agreement and transmission characteristics sufficient to guarantee the sound quality.”  And a gateway service thrown in.

Native means carrying the IP packets without converting them to an old-fashioned telephone call. The IP packets in question are at first carrying SIP call setup messages, then once the call is set up, the IP packets each contain typically 20 ms of digitized speech.

SIP Trunking replaces the previous architecture of PBX trunks.

It would be more accurate to refer to this new service as “SIP and Voice over IP Trunking” – but “SIP Trunking” rolls off the tongue better…

To learn more, attend BOOT CAMP March 27-31, or just the last two days of BOOT CAMP, which are Course 130 Understanding Voice over IP March 30-31.

New video!

New video posted!  This is part of the introductory lesson of CTNS Course 2206 Wireless Telecommunications.

The length of the shadow behind an object is proportional to the frequency of the energy.

Click to watch on YouTube

For more information:

Course page:

CTNS Certification page:

Wireless Telecommunications is a comprehensive course on wireless, mobile telecommunications plus wireless LANs and satellites.

We begin with basic concepts and terminology including base stations and transceivers, mobile switches and backhaul, handoffs, cellular radio concepts and digital radio concepts.

Then, we cover spectrum-sharing technologies and their variations in chronological order: GSM/TDMA vs. CDMA for second generation, 1X vs. UMTS CDMA for third generation along with their data-optimized 1XEV-DO and HSPA, how Steve Jobs ended the standards wars with the iPhone and explaining the OFDM spectrum-sharing method of LTE for 4G.

This course is completed with a lesson on WiFi, or more precisely, 802.11 wireless LANs, and a lesson on satellite communications.

You’ll gain a solid understanding of the key principles of wireless and mobile networks:
• Coverage, capacity and mobility
• Why cellular radio systems are used
• Mobile network components and operation
• Registration and handoffs
• Digital radio
• “Data” over cellular: Internet access
• Cellular technologies: FDMA, TDMA, CDMA, OFDM
• Generations: 1G, 2G, 3G, 4G
• Systems: GSM, UMTS, 1X, HSPA, LTE
• WiFi, 802.11 wireless LANs
• Satellite communications

Tutorial: How do IP packets and MAC Frames go together?

It is important to understand how packets and frames are related, and in particular, IP packets vs. Ethernet or MAC frames.

Simple network example. Routers move packets from one circuit to another.

Packets are for networks. A packet is a block of user data, such as a piece of an e-mail message, with a network address on the front. The network address is the final destination. The standard for network addresses is IP.

Network equipment like routers receive an IP packet on an incoming circuit, examine the indicated destination IP address, use it to make a route decision, then implement the decision by forwarding the packet to the next router, on a different circuit.

A frame is a lower-level idea. Frames are used to communicate between stations on the same circuit. The circuit may have multiple stations physically connected onto it, like a wireless LAN, a few stations connected by a LAN switch, or only two stations like a point-to-point LAN cable. Each station has a Media Access Control (MAC) address, sometimes called a hardware address, link address or Layer 2 address.

A frame has framing to mark the beginning and end, sender and receiver MAC addresses to indicate the stations on the circuit, control information, a payload and an error detection mechanism.

The frame is transmitted on the circuit, and all stations on the circuit receive it. If an error is detected at a receiving station, the frame is discarded and might have to be retransmitted somehow.

If no errors are detected, the receiver compares the destination MAC address on the received frame to its own MAC address, and if they are the same, processes the frame, extracting the data payload and passing it to higher level software on the receiver.

If the MAC addresses are not the same, the receiver ignores it and waits for the next one.

The end result is that the payload in the frame is communicated to the correct station on the same circuit, with no errors.

Packet with its IP address vs. frame and its MAC address

The main purpose of packets is to append an IP address to your data. The IP address is used by network equipment to make route decisions: to relay the packet from one circuit to a different circuit. This is accomplished by receiving the packet then transmitting it to a different machine, usually the next router in the chain.

To actually transmit a packet to another router, the packet is inserted as the payload in a frame, then the frame is broadcast on the circuit that connects to the next router.

Notice that there are two addresses: the IP network address and the MAC address.

The IP address on the packet is the final destination, and so does not change. The MAC address on the frame indicates the destination on the current circuit, and so is changed as the data is forwarded from one circuit to another.


This and related topics are covered in:

CTNS Certification Package

CIPTS Certification Package

Instructor-Led Course 101
Telecom, Datacom and Networking for Non-Engineering Professionals

DVD-Video V3 Fundamentals of Datacom and Networking

Telecom 101 Textbook

Tutorial: Packetized Voice

This is Section 2.9.1 of the new Telecom 101, 4th edition
print and ebook available January 2016



Brought to you by BOOT CAMP
January 25-29 2016 – Silicon Valley


– – –

This diagram provides a very high-level block diagram view of the processes involved in communicating speech in IP packets from one person to another:

Voice in IP Packets
Voice in IP Packets End-to-End

Starting on the left, commands from the speaker’s brain cause combinations of lungs, diaphragm, vocal cords, tongue, jaw and lips to form sounds.

A microphone is positioned in front of the mouth and acts as a transducer, creating a fluctuating voltage which is an analog or representation of the sound pressure waves coming out of the speaker’s throat.

This is fed into a codec, which digitizes the voltage analog by taking samples of it 8,000 times per second and coding the value of sample into binary 1s and 0s. Typically, the value of each sample is represented with a byte, meaning 64 kb/s to be transmitted.

Approximately 20 ms worth of coded speech is taken as a segment and placed or encapsulated in an IP packet.

The IP packet begins with a header, which is control information, the most interesting part being the IP address of the source telephone and IP address of the destination telephone.

IP packets are moved from the source to the destination over a sequence of links.

The links are connected with routers, which relay the packets from one link to the next.

Lower level functions such as framing and link addressing are usually performed following the IEEE Ethernet and MAC standards.

At the lowest level, the links are physcially implemented with Category 6 LAN cables, DSL modems, Cable modems, fiber optics and radio systems.

At the destination, the bits are extracted from the IP packet and fed into a codec, which re-creates the analog voltage.

This voltage drives a speaker, which re-creates the sound pressure waves, which travel down the ear canal to the inner ear, causing hairs on the cochlea to vibrate, triggering neural impulses to the brain, making the listener think they are hearing something.

– – –

It’s important to note that the voice packets are communicated directly from one telephone to the other over the IP network.
The packets do not pass through a CO telephone switch, for example.

– – –

For a full explanation of all of the technologies mentioned in this tutorial, register for BOOT CAMP in Sunny Silicon Valley in January!


is Core Training Course 101 Telecom, Datacom and Networking for Non-Engineering Professionals
and VoIP Course 130 Understanding Voice over IP
in one week at a discounted price.

Get this career-enhancing boost.  Check it out!

Development #4: A Worldwide Standard for Mobile Wireless

A closer look at the fourth item in our list of eight major recent developments and trends in telecom.

Telecommunications technology is constantly changing and improving – seemingly faster and faster every year – and at Teracom, we keep our training courses up to date to reflect these changes. In a previous post, we identified eight major developments and trends in telecommunications incorporated in our training.

In this post, we take a closer look at the fourth development:
a worldwide standard for mobile wireless has finally been achieved with 4G LTE.

Mobility means it is possible to start communicating with a particular radio base station, then when moving physically away, be handed off to another base station down the road to continue communications uninterrupted. In a non-mobile system (like WiFi), communication ceases if you move too far away.

The first generation (1G) of mobile radio was characterized by analog FM on frequency channels. Numerous incompatible systems were deployed: AMPS in North America, TACS in the UK, NMT in Finland and others.

The second generation (2G) was digital, which means modems communicating 1s and 0s between the handset and base station. Again, several incompatible systems were deployed, and two warring factions emerged, which could be called the “GSM/TDMA faction”, and the “CDMA faction”.

By far, the most popular 2G system was GSM, a European technology where a number of users time-share a single radio channel. Another system was IS-136, called “TDMA” in North America, deployed by the company currently known as AT&T Wireless in the US and Rogers in Canada.

A less popular 2G system employed CDMA, using technology patented by American company Qualcomm, and deployed by Verizon, Sprint and Canadian telephone companies.

These 2G systems were totally incompatible. A basic phone from a carrier could not work on another carrier unless they both used exactly the same system.

To try to avoid a repeat of the incompatibility for the third generation, the International Telecommunications Union (ITU) struck a standards committee in year 2000 called IMT-2000, its mission to define a world standard for 3G.

They failed. IMT-2000 instead published a 3G “standard” with five incompatible variations. The two serious variations were both CDMA – but differed on the width of the radio bands, the control infrastructure and synchronization method among other things.

The GSM/TDMA faction favored the deployment of CDMA in a 5 MHz wide band. This was called IMT-DS, Direct Spread, Wideband CDMA and Universal Mobile Telephone Service (UMTS). Its data-optimized version was called HSPA.

The CDMA faction favored a strategy that was a basically a software upgrade from 2G, employing existing 1.25 MHz radio carriers. This is called IMT-MC, CDMA multi-carrier, CDMA2000 and 1X. Its data-optimized version was called 1XEV-DO.

Again, these 3G systems were completely incompatible. A basic UMTS phone could not work on a 1X network.

Market forces finally pushed the two camps together.

The fact that there were far more users in the GSM/TDMA faction meant that their phones were less expensive, had better features and appeared on the market first. This put the carriers in the CDMA/1X faction at a disadvantage. This trend was continuing into 3G, where UMTS phones would have the same advantage over 1X phones.

Then, Steve Jobs invented the world’s most popular consumer electronic product, the iPhone – but only permitted carriers in the GSM/TDMA/UMTS faction to have it. This severely tilted the playing field.

In the face of this, the CDMA/1X faction threw in the towel, and decided to go with the GSM/TDMA/UMTS faction’s proposal for the fourth generation (4G), called LTE, to level the playing field.

And once this was agreed, Steve Jobs allowed the iPhone on all networks. One of the legacies of Steve Jobs will not just be the iPhone, but ending the standards wars by pushing the industry to agree on LTE as a single worldwide standard for mobile communications as of the fourth generation, using the leverage of his iPhone.

I hope you’ve found this article useful!

If you like, you can watch a video segment of our instructor explaining why LTE became a worldwide standard on youTube

Additional explanation of cellular concepts, TDMA, CDMA and LTE is available in:
Teracom online tutorials
Course 101: Telecom, Datacom and Networking
for Non-Engineering Professionals

Textbook T4210
Telecom, Datacom and Networking
for Non-Engineer

Online Course 2206 Wireless Telecommunications
(part of the CTNS certification coursework)
Online Course 2232 Mobile Communications
(part of the CWA certification coursework), and
DVD Course V6 “Wireless”

Tutorial: Bluetooth

This tutorial on Bluetooth is Lesson 2: Bluetooth, from Course 2233 “Fixed Wireless”.  Watch the lesson by clicking the picture below.
You can also watch the video on YouTube.
The text is from the Course book / CWA certification study guide.


Young man illustrating Bluetooth channel as frequency-hopping pattern using a pogo stick. Click the image to watch the full lesson. The text that follows is from the course book.
Young man illustrating Bluetooth channel as frequency-hopping pattern using a pogo stick.
Click the image to watch the full lesson. The text that follows is from the course book.

Bluetooth is a set of standards for short-range digital radio communication published by a consortium of companies called the Special Interest Group. It was originally developed as a wireless link to replace cables connecting computers and communications equipment.

Bluetooth connections are called piconets and Personal Area Networks since (in theory) up to eight devices can communicate on a channel within a range of 1 to 100 meters depending on the power.

In reality, Bluetooth is mostly used point-to-point with ten meters range.

The first data rate for Bluetooth was 0.7 Mb/s, followed by an enhancement to “3” Mb/s (2.1 Mb/s in practice). A High Speed variation employs collocated Wi-Fi for short high-bitrate transmissions at 24 Mb/s. The Smart or Low Energy variation allows coin-sized batteries on devices like heart-rate monitors.

Bluetooth applications
Bluetooth applications

Applications include wireless keyboard, mouse and modem connections… though today, 2 Mb/s Bluetooth is likely slower than the modem.

Bluetooth is used to replace wires connecting a phone to an earpiece, or to an automobile sound system for hands-free phone calls while driving. In this case, both two-way audio and two-way control messages are transmitted.

Bluetooth is also used to stream music from a smartphone to a receiver connected to an amplifier and speakers in an automobile or in a living room.

In the future, wireless collection of readings from devices like heart-rate monitors will be widespread.

Each of these types of applications corresponds to a Bluetooth profile, which is a specified set of capabilities and protocols the devices must support.

Bluetooth implements frequency-hopping, where the devices communicate at one of 79 carriers spaced at 1 MHz in the 2.4 GHz unlicensed band for 625 microseconds (µs), then hop to a different carrier for 625 µs, then to another, in a repeating pattern known to both devices. A particular hop sequence is called a channel, and is identified by an access code.

This is called Frequency-Hopping Spread Spectrum (FHSS), since hopping between 79 carriers spreads energy across spectrum 79 times wider than one carrier. It has the advantage of reduced sensitivity to noise or fading at any particular carrier.

If different pairs of devices are using different hop sequences, they can communicate at the same time in the same place without interfering. There are security advantages if the hop sequence can not be determined by a third party.

The initiator of communications is called the master. It determines the frequency hopping pattern, when the pattern begins, when a packet begins and when a bit begins. The packet and bit timing is based on the master’s clock, which ticks every 312.5 microseconds. Two ticks make a slot. A slot corresponds to a hop. The master transmits and the slave listens in even-numbered slots; vice-versa in odd-numbered slots.

To establish the channel, the master derives a channel access code from its Bluetooth address, and indicates the code to the slave at the beginning of every packet. Both master and slave use this to determine the actual frequency-hopping sequence.

Data is organized into Bluetooth packets for transmission. Packets can be 1, 3 or 5 slots long. A bit rate of 2 Mb/s would mean Bluetooth packets are about 150, 450 or 750 bytes long.

Discovering other devices means sending requests in packets on pre-defined channels called inquiry scan channels. Making a device discoverable means it listens on the inquiry channels, and responds to inquiries with information like its Bluetooth address, name and capabilities. This results in a list of Bluetooth devices displayed on the discovering device, such as a smartphone.

Connecting to a device means paging the device on its paging channel, a channel with access code derived from the target’s Bluetooth address. Devices listen on their paging channel, and respond to pages to establish a session. Once the session setup protocol is completed on the paging channel, the devices begin communicating on the channel defined by the master.

The frequency hopping pattern can be adapted to skip carriers where the signal to noise ratio is permanently low, to improve overall performance.

I hope you’ve enjoyed this tutorial!

This discussion is covered in the following Teracom training courses:
• DVD-Video Course V6: Understanding Wireless

• Online Course 2233 Fixed Wireless

How to implement a WiFi range extender for $20

A volunteer project to set up WiFi in a 150-year-old building with stone walls that I did recently required repeaters, also known as range extenders.

I ended up writing detailed instructions to get a popular WiFi access point / router on Amazon working as a repeater… and thought you might find this useful to extend WiFi coverage in your home or small office.


Even if you don’t need to extend your WiFi coverage, understanding the configuration, including the IP addresses, DHCP, subnets and all the other items covered in this tutorial is career-enhancing knowledge.

The IP addressing story including DHCP is covered in
Online Course 2213 “IP Networks, Routers and Addresses”
(part of the CTNS Certification Package), as well as

Instructor-Led Course 101, the Telecom, Datacom and Networking for Non-Engineers textbook, and DVD-Video Course V4 Understanding Networking 1.

The requirement was to provide WiFi coverage in a 150-year old building with thick stone walls. The Internet connection (DSL) was in the basement, and coverage was required to the fourth floor.

We initially looked at pulling a cable to the fourth floor, but the stone walls made wireless a no-brainer.

The WiFi signal produced by the ISP’s Customer Edge device, which contains the DSL modem, a router, switch and WiFi Access Point, did not reach very far.

So WiFi repeaters, sometimes called Range extenders would be required. This had to be implemented with encryption of data over the air for information security.

Special-purpose range extenders can cost $300 each. After a bit of research, I bought these $20 units on Amazon.

They support “300 Mb/s” 802.11n, and most importantly, implement the Wireless Distribution Service (WDS) with WPA2 airlink encryption, which is needed for the repeater function with security.

Here is the product link on Amazon.   I don’t get a commission.

The instructions weren’t very complete, so I looked at the product’s Q&A section on Amazon and found instructions.
But those instructions turned out to be not quite right. And being an Engineer, I couldn’t help but proposing correct instructions…

These instructions assume you are connecting the WiFi access point / router pictured, TP-LINK model TL-WR841N, to any WiFi with a working Internet connection.


[example] = example values used during my setup.
Yours might be a bit different.
SOURCE-AP = the access point / router generating the wireless signal you want to repeat. This is often supplied by your ISP.
REPEATER-AP = the access point / router repeating the wireless signal, the one that we are setting up.
SOURCE-NET = the SSID (network name) of the wireless signal you want to repeat.
REPEATER-NET = the SSID (network name) of the repeated wireless signal.
GUI = Graphical User Interface.
This is the access point / router’s control panel.

Before starting, gather the following information:
– The LAN/wireless side IP address of the SOURCE-AP GUI. []
– The username and password for the SOURCE-AP GUI.
[admin, admin]
– The subnet the SOURCE-AP is using on the LAN/wireless side. [192.168.3.x]
– The encryption type and password [WPA-2 PERSONAL, xxxx]
– The channel the wireless signal to be repeated is on. [3]

If you don’t know the channel, you can find out during the setup below. However, it is preferable to log in to the SOURCE-AP GUI and set the channel to 3 instead of “auto” so it does not change, and uses an unpopular channel likely to have less interference.

To determine the LAN/wireless IP address and subnet of the SOURCE-AP, look at the IP address and default gateway of a device directly connected to the SOURCE-AP. (Open the Network connections folder, click change adapter settings, and view status and then details in Windows). The value in the default gateway field is the IP address of the SOURCE-AP GUI. The part of the address common to the default gateway and the device is the subnet ID.

Do this setup and get it working somewhere comfortable near the SOURCE-AP. Once it’s working, you can place the repeater anywhere near an electrical outlet.

Here we go:

1. Plug the power into the REPEATER-AP. If any settings have already been changed on the device, press and hold the reset button on the back for ten seconds until all lights are illuminated to indicate reset happening. Reset is not necessary if the unit is fresh out of the box.

2. Plug a PC into a LAN port on the REPEATER-AP with the supplied LAN patch cable. I used my laptop. Make sure the LAN adapter is set to get an IP address automatically. (Open the Network connections folder, click change adapter settings, and view properties in Windows). Make sure the LAN adapter is the only one enabled. Disable the wireless adapter.

3. Open a browser and go to . This gets you to the GUI of REPEATER-AP, initially The default username, password is admin, admin. Don’t do the quick setup.

4. Click “Wireless” on the left column menu.
On the Wireless Settings page that appears:
a. Under the dropdown list for “Channel”, select the channel the wireless signal to be repeated is on. [3] If you don’t know, skip this step and the unit will force you to select the correct one after the “Survey” step below.
b. Click the “Enable WDS bridging” checkbox.
c. Click “Survey”. A list of SSIDs appears. Click “connect” on the one that is SOURCE-NET. [GROUND] All of the fields are automatically populated except for the password.
d. Enter the password and click Save. Wait ten seconds for the processing to finish.
e. At the top of the page beside Wireless Network Name, enter a name for REPEATER-NET [R1] and click Save.

5. Click “Wireless Security” on the left column menu. Select Personal WPA2-PSK, AES encryption and enter a password for REPEATER-NET.

6. Click “DHCP” on the left column menu. Click the DHCP disable radio button. Click Save. Ignore the reboot warning.

7. Click “Network” on the left column menu.

8. Click LAN. Change the IP address to one in the SOURCE-AP subnet that is not being used by any other device and click Save []. A reboot warning will appear. Click OK and let the unit reboot.

9. The address in the browser will magically change to the IP address you entered in the previous step. This is the new IP address for the GUI on REPEATER-AP. You will be prompted to log in again. The status screen will appear. Under Network, click the WAN MAC menu item on the left.

You should also now have Internet through REPEATER-AP!
Open in a new tab in your browser to verify.
Wireless devices can now connect to REPEATER-NET.
Wired devices can connect to REPEATER- AP.
Both get Internet access through SOURCE-AP.
Ain’t life grand?

10. To avoid problems with dynamic addresses and timeouts, make the IP address of REPEATER-AP static.
Open a new tab in your browser. Enter the address of the SOURCE-AP GUI [] and log in. Find the screen that lets you assign static IP addresses. The SOURCE-AP could be any brand of device; it is often supplied by your ISP. The function might be called “DHCP reservations” or “IP address reservation”. Make a new entry, with the WAN MAC address displayed in the REPEATER-AP GUI and the REPEATER-AP IP address you entered in Step 8.

I actually set up a chain of four of these units to provide wireless coverage from the basement to the fourth floor of a 150-year-old building with stone walls.  And it worked!

Good luck!

P.S. Don’t forget to go back in to REPEATER-AP and change the password. The menu item is hiding under System Tools on the left.

Notice required by the legal department: This information is provided as general background information only. Design and implementation of a communication system requires professional advice to identify and resolve issues specific to that particular system, including but not limited to performance, availability and security issues. Additionally, while we have strived to be as accurate as possible, we make no representation or warranty that the information provided is 100% accurate. This information is not to be relied upon as professional advice, nor is it to be used as the basis of a design. Users of this information agree to hold the author and Teracom Training Institute Ltd. harmless from any liability or damages. Acceptance and use of this information shall constitute indication of your agreement to these conditions.

Development #3: MPLS has replaced ATM

A closer look at the third item in our list of eight major recent developments and trends in telecom

Telecommunications technology is constantly changing and improving – seemingly faster and faster every year – and at Teracom, we keep our training courses up to date to reflect these changes.  In a previous post, we identified eight major developments and trends in telecommunications incorporated in our training.

In this post, we take a closer look at the third development:
MPLS has replaced ATM for traffic management, achieving  another long-held goal in the telecommunications business, called convergence or service integration.

A long-held goal in the telecommunications business has been to transport and deliver all types of communications on the same network and access circuit, and in an ideal world, with a single bill to the customer. This idea is sometimes called convergence, though service integration is a more accurate term.

It results in a large cost savings compared to different networks, access circuits and bills for each type of communications.
In days past, this was not the case.

A residence would have at least two entry cables: twisted pair for telephone and coax for television, and separate bills for each.

The situation was even worse and more expensive in the case of a medium or large organization.

At each location, a typical organization would have the requirement to communicate
• Telephone calls to/from the PSTN,
• Telephone calls to/from other locations of the organization,
• Data to/from other locations of the organization, and
• Data, video and possibly voice to/from the Internet.

In days past, the organization might have had four physical access circuits and services – along with four bills:
• ISDN PRI over T1 to a LEC for telephone calls to/from the PSTN,
• Tie lines or a voice VPN with a custom dialing plan from an IXC for telephone calls to/from other locations of the organization,
• Dedicated T1s from an IXC for data to/from other locations of the organization, and
• DSL, Cable or T1 access from an ISP for data, video and possibly voice to/from the Internet.

Not only did this mean four services and four access technologies and four bills for the customer, it also meant the carrier had to implement and support four network technologies… a very expensive situation.

MPLS for Service Integration

The solution to integrate all of this onto one access circuit and one network is twofold:
At the source,
• Format all types of traffic the same way, and
• Paste an identifier on the front of each piece of traffic, indicating what it is and where it goes.

Then all traffic can be carried interspersed on the same access circuit and in the same network, which results in a huge cost savings for both the customer and the carrier.

The identifier on the traffic is used to both route the traffic to the correct destination, and manage the traffic in the network, performing functions like load balancing, prioritization and restoration.

Starting in the 1980s, telephone companies and equipment manufacturers attempted to implement this with a technology called Asynchronous Transfer Mode (ATM). Literally billions of dollars were spent developing and deploying ATM from 1980 to 2000… but it failed and died, becoming too complex and too expensive, and not used for voice at the big telephone companies.

Multiprotocol Label Switching (MPLS) combined with IP has succeeded where ATM failed and is now universally implemented.

Of course, there is a lot of jargon to learn and many components to the “MPLS” story.

Here is a VERY brief explanation:
• All traffic is formatted into IP packets by the equipment that generates it, for example, a telephone or computer.
• Traffic is categorized into classes. A class of traffic goes from the same place to the same place and experiences the same transmission characteristics like delay and lost packets.
• A packet is identified as belonging to a particular class by pasting a number called a label on the front of the IP packet.
• The device that does the classification and labeling of packets is the ingress device, called a Label Edge Router in MPLS. It is normally Provider Equipment (PE), meaning owned and furnished by the service provider, located at the customer premise.
• Network equipment, called Label Switching Routers in MPLS, use the label number to route and in some cases prioritize the packet.
• Labels can be stacked, meaning one label pasted in front of another. This allows the network to manage similar kinds of traffic as a single entity in network control systems.

Returning to our example illustrated above, the four circuits illustrated at the top of the diagram can be replaced with one access circuit with three traffic classes (three labels). The physical access circuit could be 10 Mb/s to 10 Gb/s Optical Ethernet.

The three traffic classes / labels would be:
• A traffic class for telephone calls. This might be called a “SIP trunking service” by the marketing department. This class will carry VoIP phone calls to the carrier for communication to other locations of the organization, or for conversion to traditional telephony for phone calls to the public telephone network.
• A traffic class for data. This might be called a “VPN service” by the marketing department. This class carries file transfers, client-server database communications and the like securely to other locations of the organization.
• A traffic class for Internet traffic. This class carries anything in IP packets to the Internet.

All of this traffic is IP packets interspersed over the single access circuit.

At the other end of the access circuit, the carrier uses the label to route the traffic onward and possibly prioritize it to assure the appropriate service level.

The result is all of the organization’s traffic carried over a single access circuit, using a single technology.

This is one of the Holy Grails of the telecommunications business, called convergence or service integration, having significant advantages in cost and flexibility.

This is a concise description of a story that has many different facets.

In Teracom training, this discussion comes AFTER many other lessons explaining all of the underlying concepts, related technologies like PRI and SIP trunking and their jargon.

If you would like the whole story, it is currently included in the following training:

Course 101: Telecom, Datacom and Networking
for Non-Engineering Professionals

Certified Telecommunications Network Specialist (CTNS)
Online telecommunications certification courses

Telecom, Datacom and Networking for Non-Engineers textbook

and DVD-Video Courses V3 and V4.