Tutorial: TCP/IP over MPLS

TCP/IP over MPLS Protocol Stack

Please click here to see the full tutorial on its web page, with the necessary diagram…

We’re getting ready to release another Online Course at the end of March: L2014 “MPLS and Carrier Packet Services.”

As a sneak preview, this newsletter’s free tutorial is part of Lesson 11 “TCP/IP over MPLS” from that course.

NOTE: You may find this tutorial a bit overwhelming, landing smack on your computer screen with no preparation, like a parachutist whose chute didn’t open landing in a cow field.

In the Online Course “MPLS and Carrier Packet Services”, there are TEN lessons building up to this one.

We’re actually going to be recommending at least two modules: “The OSI Layers and Protocol Stacks” and “IP Packet Networks, Addresses and Routers” as prerequisites… so that would be at least THIRTY-FIVE lessons building up to this one.

So… if you are already familiar with the OSI Layers and protocol stacks, and IP packets and LANs, you’ll find the following lesson easier to follow.

If you’re not already familiar with those pre-requisites, then you might want to watch some other free tutorials first:
Video Tutorial VT-3 “Packets, Frames, Addresses and Routing”, Video Tutorial VT-4 OSI Layers: The FedEx Analogy, and the “Datacom and Networking Fundamentals” section of our free online tutorials.

The tutorial is part of the text and one graphic from Lesson 11 “TCP/IP over MPLS”. The Online Course when released at the end of March will have extensive animations following along with a voiceover of the text. Enjoy!

Please click here to see the full tutorial on its web page, with the necessary diagram…

Tutorial: Network Address Translation (NAT)

In lessons leading up to this one, we cover private IP addresses, and why these are preferable to use on an in-building network.

However, if any of the users on the private network want to receive packets from the Internet, a public IP address is required.

The question we explore in this lesson is how to enable Internet communications for all users in-building without having to rent a public IP address for every user?

A solution is to use a Network Address Translator (NAT).

Watch the interactive Online Course Lesson or continue reading below.

Network Address Translation (NAT)

When a computer on the private side initiates communications with a server, it populates the source IP address field in the packet header with its private address and the destination IP address field with the public IP address of the server.

The packet is then transmitted in a MAC frame to the computer’s “default gateway”, which is the Customer Edge router. This device is performing the NAT function.

The NAT changes the source IP address from the private IP address of the sender to the public IP address of the NAT, i.e. the CE router, then transmits the packet in a frame on the public network (the Internet).

The Internet server of course uses the source address in the packet it receives as the destination address to answer back to the client. Therefore, it will send the response back addressed to the NAT.
When the NAT receives the packet, it changes the destination IP address on the packet received from the Internet to the private IP address of the appropriate computer, then transmits the packet in a MAC frame to the computer.

One question that arises is: how does the NAT know what computer on the private network a packet received from the Internet is intended for?

It turns out that the NAT uses the Layer 4 header to keep track of things. The Layer 4 header (TCP or UDP) begins with two octets that are called the “source port” then two octets for the “destination port”. These fields are used to indicate which application on a computer the message is being sent from and to.

The NAT selects an arbitrary “fake” port number to identify a computer on the private network, and records this port number against the private address in a table.

When a packet is transmitted to the Internet, the NAT records the actual source port number then changes the source port value to the “fake” port number.

When the reply from the server is received from the Internet, it has the “fake” port number in the destination port field of the Layer 4 header. The NAT uses this to look up the correct private IP address and correct port number and enter those values in the destination address and destination port number fields, thus relaying the incoming packet to the correct computer on the private network.

NAT provides a number of advantages:

1. A NAT allows multiple computers in-building to share a single Internet address and Internet connection.

2. A NAT provide a truly “always-on” connection to the Internet. Services like DSL and Cable modem described as “always on” are always connected at the Physical Layer. They do not provide “always on” at the Network Layer, since DHCP must be run every time the attached device restarts to get a public IP address.
When a NAT is inserted, it runs DHCP to get the public IP address; so if the NAT is not powered off, the site will always have a public IP address assigned, and thus a connection to the Internet always ready for immediate use.

3. A NAT shields machines from attacks from the Internet. Since a private IP address is not reachable from the Internet, there is no way for a machine on the Internet to initiate communications to a machine on the private network. The only device exposed to the Internet is the NAT. Normally, the NAT is not running on a computer running Windows, so attackers have a greatly diminished chance of finding an vulnerability to exploit compared to connecting a computer running Windows naked onto the Internet.

Devices that perform this function are available in industrial-strength versions from companies like Cisco. Hardware devices to do this are also available for about $20 from companies like Linksys for use on a DSL or cable modem connection. They often include both an Ethernet switch and an 802.11 wireless LAN access point for the private network side. Most ISPs now provide the CE router with NAT function integrated in a device that includes the DSL or Cable modem they supply.

Watch the interactive Online Course Lesson, part of the Certified Telecommunications Network Specialist CTNS Certification Courses.

New Online Course: IP Packet Networks, Addresses and Routers

Online Course L2213: IP Packet Networks, Addresses and Routers

In this course, we concentrate on the fundamentals of IP packet networks, routers and IP addresses.

Packet networks embody two main ideas: bandwidth on demand and packet switching.

First, we’ll recap channelized TDM and its limitations, then understand statistical TDM or bandwidth on demand.

Next, we’ll understand how routers implement the network with packet-switching, that is, relaying packets from one circuit to another, and how routers are a point of control for network security. We’ll introduce the term Customer Edge (CE).

Then we’ll cover the many aspects of IP addressing: IPv4 address classes, dotted decimal notation, static vs. dynamic addresses, DHCP, public vs. private addresses, Network Address Translation, IPv6 overview and finish with IPv6 address allocation and assignment.

1. Module Introduction   watch now (free)
2. Review: Channelized Time-Division Multiplexing (TDM)
3. Statistical Time-Division Multiplexing: Bandwidth-on-Demand
4. Private Network: Bandwidth on Demand + Routing
5. Routers
6. IPv4 Addresses
7. DHCP
8. Public and Private IPv4 Addresses
9. Network Address Translation   watch now (free)  new tutorial!
10. IPv6 Overview
11. IPv6 Address Allocations and Assignment

Overall objective
The objective of this course is to develop a solid understanding of IP. After taking this course, you will be up to speed on the fundamental principles of packet networks: bandwidth on demand, also known as overbooking or oversubscription, and packet forwarding. You will know the IP packet format and how IP addresses are allocated, assigned and displayed. You will know the difference between static and dynamic addresses, public and private addresses and how Network Address Translation works. An additional objective is to become familiar with the basics of IPv6.

Learning Objectives
Upon completion of this course, you will be able to explain:

  • The concept of statistical multiplexing, also known as oversubscription, overbooking and bandwidth on demand, why and how it can be implemented and its benefits.
  • What a private network is
  • What a router is and how it implements the network by connecting data links
  • How routers move packets between broadcast domains, including VLANs
  • How routers also act as a point of control for traffic, called packet filtering
  • The basic structure and contents of a routing table
  • The Customer Edge
  • IPv4 address blocks: Class A, Class B and Class C, and dotted-decimal notation
  • Static addresses and dynamic addresses, and how and why DHCP is used to assign both
  • Public addresses and private addresses, how, why and where each is used
  • Network Address Translation for interfacing domains where public addresses are used with those where private addresses are used
  • The improvements and changes between IPv4 and IPv6, and
  • The types of IPv6 addresses, how IPv6 addresses are allocated to ISPs then assigned to users, and how each residence gets 18 billion billion IPv6 addresses.

List of Lessons

Lesson 1. Course Introduction (this one).

Lesson 2. Review: Channelized Time-Division Multiplexing (TDM)
We’ll review the idea of channelized Time-Division Multiplexing, what channels are, and how they can be used to aggregate traffic onto a high-speed circuit. Then we’ll raise some questions: is that an efficient way to connect devices that produce traffic in bursts, which means devices that are normally doing nothing? And what about the problem of a single point of failure for all the aggregated traffic? Subsequent lessons explore the answers to those questions.

Lesson 3. Statistical TDM: Bandwidth-on-Demand.
In this lesson, we’ll understand how circuits that move bits constantly can be used efficiently when the user’s traffic profile is: “idle most of the time, interspersed with bursts of data every once in a while.” The answer is overbooking. This is also called statistical multiplexing and bandwidth-on-demand, and is a key part of a packet network: the internal circuits are heavily overbooked, to give users the highest speed at the lowest cost. It is necessary to know the users’ historical demand statistics – also called their traffic profile – to know how much to overbook, hence the term statistical multiplexing.

Lesson 4. Private Network: Bandwidth on Demand + Routing.
The purpose of this lesson is to expand the discussion of the previous lesson to include multiple circuits. The result is called a private network, and is the simplest framework for understanding routers, routing, network addresses and bandwidth-on-demand.

Lesson 5. Routers
In this lesson, we’ll take a closer look at a router, more precisely identifying the functions a router performs to implement a packet network, and understand how a router routes by examining the basic structure and content of a routing table. We’ll also understand how the router can act as a point of control, denying communications based on criteria including network address and port number, why this is implemented and its limitations. The term Customer Edge (CE) is defined in this lesson.

Lesson 6. IPv4 Addresses
Here, we’ll understand IPv4 addresses, address classes and the dotted-decimal notation used to represent them.

Lesson 7. DHCP
In this lesson, we’ll cover DHCP: the Dynamic Host Configuration Protocol, and understand the mechanism by which a machine is assigned an IP address. We’ll also understand how the “dynamic” host configuration protocol can be used to assign static addresses to machines and the advantages of this method.

Lesson 8. Public and Private IPv4 Addresses
The purpose of this lesson is to define the terms “public” and “private” IP address, review how IP addresses are assigned and the costs for those addresses, then cover the ranges of IPv4 addresses that are used as private addresses, and understand how and why they are used.

Lesson 9. Network Address Translation
In this lesson, we’ll explore how private IPv4 addresses used in-building and a public address required for Internet communications can be joined together with a software function called Network Address Translation.

Lesson 10. IPv6 Overview
Completing this course on IP, we’ll first review the next generation of IP: IPv6, understand the improvements compared to IPv4 and review the format of the IPv6 packet and its header.

Lesson 11. IPv6 Address Allocations and Assignment
Finally, we examine the structure of the 128-bit IPv6 address, review the different kinds of IP addresses, the organizations that allocate them, and the current plans for how addresses will be assigned to end users… and how every residence gets 18 billion billion IPv6 addresses.

802.11g Wireless LAN (WiFi) base station on my new Samsung Galaxy Android phone

Waiting for a flight at the airport. Time on my hands, I try out a feature included with the Android operating system on my new Samsung Galaxy: create an 802.11g Wireless LAN (WiFi) base station on the phone.

This WiFi network is automatically bridged inside the phone to the Internet connection provided by the cellular carrier.

Easy step-by-step instructions were included on the setup screen.

Fired up my laptop and found the WiFi network and connected no problem.

In fact, I sent a post to Google’s servers over the very link!

Ain’t technology wonderful.

Bonus: your car can now be a WiFi hotspot! You could even get a WiFi hotsopt logo sticker and put it on your back window, like Greyhound… On a long car trip with my family, all of whom have WiFi enabled iPhones, iPods, DSs etc. etc., I can tell them the WiFi password, and they can share my internet connection.

Double bonus: If the kids start squabbling, I can threaten to turn it off!

btw, I have 6 GB/month in my plan, so not so worried about usage-based pricing for the connection. Best check your billing plan before trying it.

EC

New! Try the free Teracom Telecom, Datacom and Networking Quiz

Assess your knowledge of telecommunications, data communications and networking fundamentals with this free online quiz!

The quiz is ten random multiple-choice questions from the Certified Telecommunications Analyst CTA certification exam. You’ll get an immediate reading of your telecom, datacom and networking IQ, and maybe even learn something useful during the answers review at the end.

Do it as many times as you like – different questions every time!
Challenge your colleagues!

Instructions

1. Follow the step-by-step instructions on this page to load the free knowledge evaluation quiz

2. Enter your answers for each of the ten multiple-choice questions.
At the end your score will be displayed and you’ll have a chance to review the answers.

3. No one expects you to know all this stuff… but… comparing your answers to the correct ones, you may well find that you need to improve your knowledge base. Our renowned telecom training for non-engineers is the ideal way to fill in the gaps, put in place a solid base of knowledge and a structure on which to build.

4. Register for one of our high-quality public seminars, hold a private on-site seminar, order our self-paced DVD-video series, take online course modules and/or get a Telecom 101 reference book.

5. Learn what the jargon and buzzwords really mean, and how it all fits together. Be more effective and less frustrated. Deal with telecom and networking equipment vendors and carriers. Speak intelligently at meetings. Converse with “techies”. Obtain a valuable reference book.

6. Gain serenity, a promotion, a revitalized career, new job, or even achieve world domination.*

*Individual results may vary

Wireless Telecommunications – new Online Course released

We’re pleased to announce the release of another online course: Wireless Telecommunications.

In this course, we cover wireless, concentrating mostly on mobile communications.

We’ll cover the principles of operation, jargon and buzzwords in the mobility business, the idea behind cellular radio systems, and explain the different spectrum-sharing technologies, including 1G analog FDMA, 2G TDMA/GSM vs. CDMA, 3G 1X vs. UMTS CDMA and 4G OFDMA.

We’ll conclude with a lesson on 802.11 wireless LANs (Wi-Fi) and a lesson on satellite communications.

Lessons in this module

1. Module Introduction – Wireless Communications
watch intro now (free)

2. Mobile Network Components, Jargon and Basic Operation

3. Cellular Principles and AMPS (1G)

4. 2G: Digital Radio – Voice Communications

5. Digital Cellular: Data Communications

6. Spectrum-Sharing Technologies: FDMA, TDMA, CDMA, OFDM

7. 3G Cellular: CDMA watch now (free)

8. 4G Mobile Cellular: LTE

9. 802.11 Wireless LANs – WiFi

10. Communication Satellites

Net Neutrality – Foolish, ignorant or disingenuous?

The popular press and news feeds have been full of stories about advocates of “net neutrality” testifying to congressional committees, lobbying the federal government and railing against the big ISPs over the past while.  Not much mention of arguments against net neutrality, though.  It’s hard to decide whether those arguing for net neutrality are foolish, ignorant or disingenuous.  
 
Let’s begin with some definitions. When someone demands “net neutrality”, they usually mean that the network must not discriminate between applications being carried in IP packets; that identical transmission characteristics (throughput, delay, number of errors, etc.) are to be provided for all packets regardless of what is being carried in them. They claim (correctly) that this is not the case at present, that the network service provider is “throttling” certain applications, “slowing down” or “shaping” traffic and that this, in their opinion, must stop. They sound the rallying cry “the net should be free”. 
 
What a load of hogwash.
But are these arguments foolish, ignorant or disingenuous?  Hard to decide: 

Continue reading “Net Neutrality – Foolish, ignorant or disingenuous?”

If you should know the answer to these questions about MPLS, but don't, this is the course for you:

Course 110 IP, VoIP and MPLS for the
Non-Engineering Professional
is the “next” course in our Core Training series, covering only newer technologies: virtually all aspects of IP networks and services.

Designed for non-engineers, this training course will give you the solid, vendor-independent foundation knowledge necessary to deal with IP telecom network projects and IP voice and data applications with confidence. 

If you want to know the answers to these questions, or you should know the answer to these questions, but don’t, this is the course for you: 
 
When an organization like AT&T or TELUS says it “has an MPLS network” and sells “MPLS services”,
– What exactly does that mean?
– Just what is an MPLS service anyway? What does it do? Who uses it? What for?
– Can you tell me two different ways MPLS service is different than Internet service?
– What benefit does that bring to the customer?
– Does it cost more? Better yet, is it costed the same way as Internet service?
– How do you connect to MPLS service?
– What is the technology and business environment for MPLS service going to in 2015?
 
I think you’ll agree that knowledge set is career-enhancing knowledge. We often tell people “if you want a guaranteed job, be an expert in MPLS”. Here’s a great place to start! 

And this is only one part of this intensive, three-day leadership and technology development course!
You will also learn the workings of SIP and softswitches; the nuts-and-bolts of packetized voice and its protocols; Layer 2, VLANs and 10 Mb/s – 40 Gb/s Ethernet services; IP routing; the ISP business and more.

In three days, you’ll get up to speed, demystify jargon and buzzwords, fill the gaps, understand the technologies, the underlying ideas and how it all fits together… knowledge you can’t get from trade magazines or salespeople. 

This investment will be repaid many times over, eliminating frustration at buzzword-filled meetings, increasing your efficiency, and helping ensure you make the right choices. IP, VoIP and MPLS is an essential knowledge set going forward in telecommunications. 

This professional training course will give you the solid, vendor-independent foundation necessary to deal with IP telecom network projects and IP voice and data applications with confidence. 

Get this career-enhancing knowledge today! more info

How ISPs connect to the Internet: peering vs. transit

This discussion is covered in Course 101, Chapter 16 “Understanding the Internet”,
and in more depth in Course 110, Chapter 16 “IP as a Business: Carrier Networks, Competition and Interconnect”

Originally, the only way to get on to the Internet was from a terminal connected to a computer at a university or research institute. The Internet was mostly circuits paid for by the taxpayers via the National Science Foundation. Today, commercial Internet access providers, called Internet Service Providers (ISPs) provide the capability for anyone to access and communicate over on the Internet. These ISPs are for the most part business units of facilities-based carriers, i.e. telephone companies and cable companies.

Such service providers have physical access circuits and circuit-terminating equipment on the customer side, plus routers, security and access control equipment to manage customer traffic. This is often organized with data centers in cities or regions, which are interconnected. This ensemble of interconnected routers controlled by an ISP is called an Autonomous System (AS).

The Internet is a vast, unregulated collection of interconnected Autonomous Systems. The connections between ASs are not specified by a central authority or world government, but are implemented on a case-by-case basis by the operators of an AS for business reasons. The Internet is not free. It is not a public utility. It is a business.

ISPs operating ASs will connect to competitors and content providers like Google to exchange traffic terminating on each other’s network (called peering), and will connect to larger organizations who will assure delivery of packets to other destinations (transit). The networks are physically connected at Internet Exchange (IX) centers such as Equinix Chicago at 350 E Cermak. These are buildings with equipment implementing network interconnection operated by a neutral third party. The ASs are responsible for paying for connectivity to the IX.

Course 101, page 16.09: Internet Service Providers

Internet Service Providers

Peering is settlement-free, i.e. no money is exchanged. Transit is a commercial service that costs money. Larger ISPs charge smaller ISPs for transit services. The largest networks are sometimes called Tier-1 service providers… but “Tier-1” is not an officially defined term. Some claim that it means a network “close to the center of the Internet” or a network that does not pay for transit. However, there is no “center” to the Internet, and virtually all networks employ a mix of peering and transit agreements to connect to other networks… and the nature of such connections is non-disclosed confidential business information. A “Tier-1 network” might best be thought of as one operated by a very big facilities-based carrier that has presence in most or all IXs and sells transit services to smaller networks and ISPs.

The ISPs build the access network and peering or transit connections to other networks, then charge the users for access. It’s a pyramid scheme. The end users end up paying for all.

In addition to access services, the ISP usually provides a Web server to host your website, a Domain Name Server, and an e-mail server.
Back in the Flintstones era when dial-up Internet access was first available, telcos were a bit slow to react, so for a while, companies like Netcom, MindSpring, Portal, Pipeline, iStar and others had their day in the sun. These organizations were resellers, leasing circuits from a carrier and reselling them to users under per-minute or per-month billing plans.

The carriers eventually began competing with resellers, who for the most part went out of business, selling their customers to the carriers. For example, Netcom is now part of Earthlink, which is majority owned by Sprint. AOL and MSN are the biggest remaining reseller-type ISPs. For the most part, it is business units of the companies that own the cables coming into your home: the LEC and the cable TV company that are the dominant ISPs today.

If you do choose to use a reseller-type ISP, particularly for a business or organization, questions regarding customer service, capacity and availability should be asked. Another is redundancy – do they have a single point of failure? Do they have multiple connections to different Tier-1 providers? What capacity are those connections?

This discussion is covered in Course 101, Chapter 16 “Understanding the Internet”,
and in more depth in Course 110, Chapter 16 “IP as a Business: Carrier Networks, Competition and Interconnect”

The Mature Competitive Environment: Regional Rings and MANs

Competition today means much more than the 1984 idea of LECs, competitive IXCs and switched access charges or subcontracted dedicated access lines. Competition today includes competitors providing various services to residences and business customers using a mix of switched access, subcontracted dedicated access, plus colocation and bypass on the “last mile”. Continue reading “The Mature Competitive Environment: Regional Rings and MANs”