Teracom Training Institute
Best of breed: telecommunications training and certification ‑ since 1992

In this issue:


Instructor-Led Training Schedule for 2024

Live, instructor-led training, where you can ask questions and interact, is the best you can get.
Being in a class, with an expert instructor, ensures that you will stay focused, away from distractions, and learn.  Includes detailed course workbooks and bonus TCO Certification.

February 12-16 Course 111 BOOT CAMP Live Online
Course 101 Broadband, Telecom, Datacom and Networking for Non‑Engineers
plus Course 130 Voice over IP, SIP, Security, 5G and IoT

March 5-7 Course 133 Atlanta
Course 133 Fundamentals of VoIP and IP Telecom Networks (3 days)

April 2-4 Course 133 Live Online
Course 133 Fundamentals of VoIP and IP Telecom Networks (3 days)

April 8-12 Course 111 BOOT CAMP Washington DC
Course 101 Broadband, Telecom, Datacom and Networking for Non‑Engineers 
plus Course 130 Voice over IP, SIP, Security, 5G and IoT

May 6-10 Course 111 BOOT CAMP Live Online
Course 101 Broadband, Telecom, Datacom and Networking for Non‑Engineers 
plus Course 130 Voice over IP, SIP, Security, 5G and IoT

June 10-14 Course 111 BOOT CAMP Santa Clara CA
Course 101 Broadband, Telecom, Datacom and Networking for Non‑Engineers 
plus Course 130 Voice over IP, SIP, Security, 5G and IoT


Here's some copy-and-paste training request text for you!


Telecom 101 Textbook Softcover 50% Off

Telecom 101 textbook Telecom 101 - High-Quality Reference Book and Study Guide Covering All Major Telecommunications Topics... in Plain English.

Packed with information, authoritative, up to date, covering all major topics - and written in plain English - Telecom 101 is an invaluable textbook and day-to-day reference on telecom.

Totally up to date, the new Sixth Edition of Telecom 101 is the materials from Teracom's famous Course 101 Broadband, Telecom, Datacom and Networking for Non-Engineers augmented with additional topics.

Printed in color in a user-friendly 7 x 10" softcover, Telecom 101 brings you in one volume consistency, completeness and unbeatable value. Rated 4.6/5 on Amazon!

Save 50% for a limited time! Order here and use coupon 1357.



Free Printed Study Guide with CTNS

Telecom 101 textbook TCO Certified Telecommunications Network Specialist courses deliver a solid foundation of knowledge in broadband, telecom, datacom and networking: the fundamentals, technologies, jargon and buzzwords, standard practices and most importantly, the underlying ideas, and how it all fits together… plus TCO Certification to prove it!

Printed in color, the CTNS Study Guide contains all of the text and the main graphic from each lesson in the CTNS courses. The physical book enhances your learning and retention while taking the online CTNS courses. It is also a great resource as a day-to-day reference handbook and glossary. $109 value with the free shipping!

Get the softcover free with free shipping for a limited time!
Register for CTNS and apply coupon 1355 at checkout



Course 133 Fundamentals of VoIP & IP Telecom Networks

Telecom 101 textbook Fundamentals of VoIP & IP Telecom Networks is a three-day vendor-independent training course specifically designed for non‑engineering professionals covering Voice over IP and the IP telecom network it runs on, beginning with a solid base of fundamentals.

Based on Teracom's proven BOOT CAMP, this course will fill in the gaps and get you up to speed on all of the concepts and technologies involved in Voice over IP, SIP, SIP trunking, VoIP phone systems and IP telecom networks.

Eliminate buzzword frustration, and gain the knowledge to be confident: structured, complete knowledge you can't get on the job, reading articles or talking to vendors.

You will get career-enhancing knowledge that lasts a lifetime, and training that will be repaid many times over in increased accuracy and productivity.

The course is organized into three parts:

Part 1: Fundamentals
1. Introduction to Broadband Converged IP Telecommunications
2. Telecom Fundamentals
3. Network Fundamentals
4. The Internet, Cloud Computing, Data Centers and SD-WANs
5. Digital Voice

Part 2: VoIP and SIP
6. VoIP Systems, Components, Standards, Jargon and Buzzwords
7. VoIP for Individuals
8. VoIP for Organizations
9. Packetized Voice and Sound Quality
10. SIP and Call Managers / Softswitches
11. SIP Trunking & Carrier Connections

Part 3: Networking
12. The OSI Layers and Protocol Stacks
13. Ethernet, LANs and VLANs
14. IP Networks, Routers and Addresses
15. MPLS and Carrier Networks

Get this career-enhancing and frustration-busting training today!



Free Telecom 101 Softcover Textbook with Course 133

Register for Course 133 and apply coupon 1356 at checkout, and you'll receive the 550-page Telecom 101 textbook in addition to your Course 133 workbook.  $179 value, free!


Free Knowledge-Testing Quiz: Network Fundamentals

Based on popular demand, Teracom's instructor-led telecom training seminars now include in-class quizzes, fostering class participation and interaction and providing knowledge verification and reinforcement.  The instructor displays the questions and the class votes on the answers.

Test your knowledge!  This newsletter, try the Network Fundamentals quiz.

We wish you well... but you may find that you are in serious need of our Instructor-Led Training or Self-Paced Online Training and TCO Certification packages, joining thousands of satisfied customers who've invested in themselves, upping their knowledge game to be more confident and effective.


Tutorial: Carrier-Grade NAT
You might not get a Public IPv4 address from your ISP...

Source: This is a new lesson added to Day 3 of BOOT CAMP, and part of new 3-day Course 133 Fundamentals of VoIP & IP Telecom Networks.
- - -

Carrier-grade NAT, also known as large-scale NAT, is a solution allowing Internet Service Providers to continue providing IPv4 addresses to end users in the face of IPv4 address exhaustion.

A better name would be ISP NAT, as it is implemented only by Internet Service Providers internal to their piece of the Internet.

In the very beginning, there was no NAT and no LAN switch at the customer premise, just one PC that connected directly to the ISP. The PC would be assigned one public IP address.

To allow multiple devices at the customer premise to share the connection to the ISP, a NAT is implemented on the Customer Edge device, with a DHCP server assigning addresses to devices at the customer premise from the ranges of IP addresses specified in RFC 1918, colloquially referred to as Private IP addresses, a DHCP client getting one Public IP address from the ISP, and the NAT function translating between the public and private IP addresses as illustrated below.


This was the standard practice for the first couple of decades of the century, and is still implemented for many users, particularly those with DSL, cable and fiber access to the ISP.

With the subsequent explosion of devices to be connected, particularly cell phones and Starlink terminals, and the continued growth of non-mobile Internet connections, more and more IP addresses are required by ISPs to assign to customers.

The number of available Public IPv4 addresses is fast dwindling, and there are not enough to keep up with the demand going forward.

In addition, IPv4 addresses are not free; the ISP must rent them from a Regional Internet Registry on an annual basis.

The long-term solution is to move to IP version 6, which has 128-bit addresses (compared to IPv4's 32-bit addresses), yielding enough addresses to meet foreseeable needs.

However, many ISPs and their users are not ready to switch to IPv6, and so still require an IPv4 address.

The medium-term solution is double NAT, as illustrated.

carrier grade nat

In this architecture, each site or POP of an ISP, that is, the building that houses an ISP's DHCP server that serves a city or a district of a city, is assigned a Public IP address, and the DHCP server at the site assigns IP addresses to customers from a block of addresses defined in RFC 6598 called Shared IP addresses.

This dramatically reduces the number of public IPv4 addresses required, since it is the ISP DHCP servers that are assigned public addresses and not the end users.

Like Private IP addresses, Shared IP addresses are not valid on the Internet, as many, many devices will end up being assigned the same Shared IP address.

This new block of Shared IP addresses was defined to avoid confusion with Private IP addresses used inside the customer premise.

This double-NAT strategy reduces the number of public IP addresses required, which not only extends the life of IPv4, but also saves ISPs money.

Newer ISPs, like Starlink and cellular providers have implemented this, and others will follow as they run out of IPv4 addresses.

The downside of this architecture is that it is not compatible with communications to devices on the Private IP address side of the customer NAT, for example surveillance cameras.

With single NAT, this can be done with port forwarding, where a rule is implemented in the customer equipment to forward TCP or UDP data units addressed to a particular port to a device with a particular Private address.

This allows communication from the Internet to the device on the Private IP side by sending packets to the Public IP address of the customer's NAT and the relevant port number.

With Carrier-grade or double NAT as illustrated, the customer's NAT does not have a Public IP address so it is not possible to address the customer's NAT from the Internet.

A work-around solution is to implement a VPN to the customer's NAT if it has this capability, or a computer on the Private IP side of the customer's NAT if it doesn't, and relay the packets from there.


- - -

Your colleagues may be interested... would you please forward this to them?

Many thanks,
Eric Coll, Course Director
Teracom Training Institute


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