In this lesson, we'll trace the flow of a file transfer over an MPLS network, seeing how TCP is used for error recovery, IP is used for addressing the destination, MAC addresses indicate the next device, and MPLS labels implement a virtual circuit for communications within the carrier IP network.
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Sixteen online courses covering telecom, datacom and networking for non‑engineers from A-Z, plus the prestigious TCO Certified Telecommunications Analyst certification.
Includes the six CTNS courses plus
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These are the words that are displayed and spoken during the lesson. Get these notes for the whole course in the Certification Study Guide, available in print or eBook. Many people tell us a printed companion book enhances their learning!
Tracing the flow of data through the TCP/IP/MPLS/MAC protocol stack and Carrier MPLS network:
Starting with the server on the right, which is downloading a file to the client on the left, the file transfer software takes a segment of the file and gives it to the TCP software on the server, which starts a timer, puts a sequence number, error check and source and destination application port number in a TCP header on the file segment, and passes this to the IP software on the server.
The IP software on the server creates an IP packet by adding the IP header, populating the source address with its IP address and the destination address with the IP address of the client on the left.
The IP packet is passed to the layer 2 LAN driver software on the server, which puts the packet in an LAN MAC frame, populating the source address with its MAC address and the destination as the MAC address of the right-hand Customer Edge router.
The frame is then signaled one bit at a time over the LAN cable connecting the server to the LAN switch, which directs the frame to the right-hand CE router.
Layer 2 software on that right-hand CE router receives the MAC frame from the sever via the switch, performs the error check, verifies that its MAC address is the destination, then extracts the IP packet and passes it to the IP routing software on the CE router.
The IP routing software on the CE router decides that the Provider Edge router is the next hop, puts the packet in a MAC frame, populates the destination MAC address with that of the PE, recalculates the error check and signals the frame one bit at a time over the circuit to the service provider's Provider Edge, which is the ingress to the carrier's MPLS network.
The Provider Edge is the ingress Label Edge Router. It receives the IP packet in a MAC frame over the fiber access circuit. This ingress device examines the destination IP address on the packet and along with other factors, decides what Forwarding Equivalence Class the packet belongs to, then implements its decision by pushing a label onto the packet.
It then does a table lookup in its Incoming Label Map to get the Next Hop Label Forwarding Entry, determines what LSR that items with this label are forwarded to, and transmits the labelled packet in a frame to that LSR on the appropriate circuit.
Each LSR in the middle of the network (not shown) receives a frame, extracts the packet then only looks at the label and performs a table lookup to determine where to forward the packet and possibly what relative priority it has.
Eventually, the labelled packet is delivered to the PE on the left, the network's egress Label Edge Router. This device pops the label off the packet and removes the MPLS header, then uses conventional IP routing to send the IP packet in an MAC frame over the access circuit to the CE router on the left.
The CE router on the left receives the IP packet in a MAC frame, passes it to its routing software, which must at this point determine which station on the LAN, which MAC address, has been assigned that IP address.
It first looks in its cache, which is a table relating IP addresses to MAC addresses. If it does not find an entry, it broadcasts an address resolution request to all stations on the LAN at the left, asking "who owns this IP address?"
The client responds with its MAC address. The premise router saves that information in the cache, then puts the packet in a MAC frame with the client's MAC address as the destination, then signals the frame one bit at a time to the left-hand LAN switch, which directs the frame to the client.
Layer 2 software on the client receives the frame over the LAN cable, extracts the IP packet and passes it to the IP software on the client.
Seeing that the destination IP address on the packet is its IP address, the client's IP software extracts the data out of the packet and passes it to the TCP software on the client.
The TCP software on the client performs the error check, and if it fails, discards the data. Meanwhile, the TCP timer on the server times out, so the TCP software on the server retransmits and the whole process is repeated.
If the second time, the protocol data unit received by the TCP software on the client passes the error check, it sends an acknowledgement to the server so the server stops retransmitting.
The TCP software on the client extracts the data from the TCP protocol data unit and parks it in a memory space for the application identified by the destination port number on the TCP header… the file transfer application, which picks up the data shortly after.
Meanwhile, the file transfer application on the server is sending the next segment of the file.
Advantages of MPLS
MPLS-based carrier bandwidth-on-demand services bring a significant improvement to the user compared to previous technologies: the user-network interface.
The Customer Edge equipment required to connect to a carrier's MPLS service is an IP router.
This IP router required to connect to an MPLS service is no different than any other IP router. In the simplest case, a $20 edge router from Linksys normally used for residential Internet could be used.
The user-network interface to an MPLS-based service is IP. It requires no special equipment or knowledge on the part of the customer, and the customer does not have to configure or keep track of virtual circuits, LSPs, labels or anything of the sort.
This is a large advantage in terms of both cost and barrier to entry for the customer.
The "M" in MPLS stands for "Multiprotocol".
In this lesson, we have constantly referred to packets and the forwarding of labelled packets. While this is the most common use of MPLS, forwarding of labelled frames is also possible.
Carrier Virtual Private LAN Service (VPLS) is a service moving LAN MAC frames using MPLS labels. With VPLS, the carrier appears like a giant, nationwide LAN switch to the customer, moving MAC frames between customer locations.
This can be implemented with Ethernet over MPLS (EoMPLS), where the customer's MAC frame has MPLS labels pasted on the front of the frame.
At this point, the labelled frame and a labelled packet can be treated the same way by LSRs in the MPLS network… encapsulated in a MAC frame for forwarding over a physical circuit.
Lesson 1 is the Introduction to the Course.
Lesson 2. Carrier Packet Network Basics The fundamental concepts of packet switching and bandwidth-on-demand or overbooking, the physical components involved in using a carrier packet network service including Customer Edge, types of access circuits, the Provider Edge and the network core – and why PE equipment is sometimes deployed at the customer premise. This lesson is completed with a roundup of the benefits of packet services over dedicated lines and circuit-switched connections.
Lesson 3. Service Level Agreements: Traffic Profile and Class of Service How performance is specified, measured, guaranteed and controlled on an overbooked bandwidth-on-demand network – the Service Level Agreement where the network guarantees specified transmission characteristics, sometimes called a Class of Service, on condition that the customer stays within a defined traffic profile … and what happens to out-of-profile traffic.
Lesson 4. Virtual Circuits The fundamentals of virtual circuits, an essential part of all packet communication networks. We'll cover the concepts of traffic classes, virtual circuits, virtual circuit IDs and the fundamental principles of operation that are common to all technologies, including MPLS, and how virtual circuits are a powerful traffic management tool.
Lesson 5* X.25: Data Packet Service from The Phone Company Beginning with this lesson, we'll run through the main virtual circuit technologies, starting with X.25. We won't spend any time on details of X.25, as it was replaced with Frame Relay then MPLS, but instead use it to introduce a graphical method of showing how packets travel between routers in frames over physical connections from user to network to user, plus concepts and jargon including connection-oriented vs. connectionless network service and reliable Class of Service vs. unreliable and pave the way for understanding current technologies Frame Relay and MPLS, and the improvements each brought to the table.
Lesson 6* Frame Relay How Frame Relay was an improvement, why it's called "Frame Relay" along with other jargon, and why IP and TCP are required in conjunction with Frame Relay service. We'll identify the equipment used for Frame Relay and the traffic profiles it supports.
Lesson 7* TCP/IP over Frame Relay In this lesson, we'll trace the flow of information from a server to a client across a Frame Relay service, identifying the protocol stacks on the terminals and edge equipment. This will allow understanding how Frame Relay network service from a carrier relates to TCP and IP used by a customer, and the requirements for connecting to a carrier's Frame Relay service.
Lesson 8. QoS Requirement for Voice Over IP Packet network services were originally designed for data communication. In this lesson, we'll understand how live voice is packetized, carried over a packet network, then reconstructed at the far end – and the transmission characteristics necessary for voice quality.
Lesson 9* ATM. ATM was supposed to be The Solution, allowing integration and convergence of all services on a packet network, as it was designed to guarantee the transmission characteristics necessary for voice and video in packets – but it became horribly complicated and expensive and is on the way out, so will simply provide an overview of ATM and its jargon.
Lesson 10. MPLS IP has emerged as the standard for packets that will be used to carry all traffic. However, since IP provides a connectionless network service, additional protocols are required to implement virtual circuits on IP networks to enable management and prioritization of traffic. The choice for virtual circuits over IP is Multi-Protocol Label Switching (MPLS). The concepts are the same as other virtual circuit technologies X.25, Frame Relay and ATM… but the jargon is changed. We'll begin by identifying MPLS components, jargon and basic principles of operation.
Lesson 11. TCP/IP over MPLS In this lesson, we'll revisit tracing the path of a file download from server to client, this time over an MPLS network. This will reveal a significant advantage of MPLS-based network services compared to Frame Relay in the user-network interface. We'll also discuss the "M" in MPLS, noting how MPLS can be used to carry frames for VPLS in addition to the usual IP packets.
Lesson 12. Differentiated Classes of Service using MPLS Here, we'll examine how classifying traffic and mapping classes onto virtual circuits can be a Quality of Service (QoS) mechanism to implement multiple Classes of Service on a packet network. This is sometimes referred to as differentiated services or Diff-Serv, i.e. providing a different Class of Service for each application: VoIP, IPTV, email, web surfing and others.
Lesson 13. Integration and Convergence using MPLS In this lesson, we'll see how virtual circuits and traffic classification can be used to combine all of the types of communications of a business or organization onto a single access circuit. This idea is sometimes called convergence, though service integration is a more accurate term. It results in a large cost savings compared to one access circuit for each type of communications.
Lesson 14. Managing Aggregates of Traffic with Label Stacking Here, we'll understand how MPLS labels can be stacked. In other words, virtual circuits carried over other virtual circuits, and how this is implemented to aggregate traffic for both routing and prioritization reasons – both on access circuits and in the network core.
Lesson 15. MPLS Services vs. Internet Service This lesson completes the course on carrier packet network services with a discussion of terminology used in sales and marketing of MPLS services, and how that translates to reality. We will use a quiz question-and-answer format to understand the difference between Internet service and what sales brochures often call "MPLS service"… and what exactly an "MPLS service" is.
*Feel free to skip the lessons on legacy technologies X.25, Frame Relay and ATM. They are optional and included for anyone who needs to know about these older technologies. These topics are not on the final exam.
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Like Teracom's famous core training Course 101 "Telecom, Datacom and Networking for Non-Engineers", our very popular core training DVD-Video packages and the Telecom 101 textbook, the Certified Telecommunications Network Specialist Certification Package begins with the Public Switched Telephone Network, then a course on Wireless Telecommunications, followed by four courses covering IP telecommunications and IP telecom networks.
If you are interested only in IP telecommunications, the CIPTS: Certified IP Telecom Network Specialist package may be appropriate, as it skips the traditional telephony and wireless and goes directly to the IP telecommunications courses.
If your goal is to build a full, rounded knowledge of telecommunications, then understanding the history, structure and operation of the telephone network built over the past 135 years or more is the starting point for everything else.
We begin with a history lesson, understanding how and why telephone networks and the companies that provide them are organized into local access and inter-city transmission, or as we will see, Local Exchange Carriers (LECs) and Inter-Exchange Carriers (IXCs).
Then we will establish a basic model for the PSTN and understand its main components: Customer Premise, Central Office, loop, trunk, outside plant, circuit switching, attenuation, loop length, remotes, and why knowledge of the characteristics of the loop remains essential knowledge even though we are moving to Voice over IP.
Next, we'll cover aspects of telephony and Plain Ordinary Telephone Service, including analog, the voiceband, twisted pair, supervision and signaling including DTMF. The course is completed with an overview of SS7, the control system for the telephone network in the US and Canada.
On completion of this course, you will be able to draw a model of the Public Switched Telephone Network, identify and explain its components and technologies including:
In many parts of the world, particularly outside Canada, the US and Western Europe, the physical telephone network is wireless, as deploying radio transceivers is far cheaper than embarking on a new project to pull copper wires and/or fiber to every residence.
Most of this course is devoted to mobile wireless telecommunications. 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:
The remaining four courses in the CTNS package are on the "IP" telecommunications network and its three main enabling technologies: Ethernet, IP and MPLS, and beginning with the OSI model and its layers to establish a framework.
If you'd prefer to take just these four "IP" courses, check out the Certified IP Telecom Network Specialist package.
This course establishes a framework for all of the subsequent discussions: the OSI 7-Layer Reference Model, which identifies and divides the functions to be performed into groups called layers.
This framework is required to sort out the many functions that need to be performed, and to be able to discuss separate issues separately.
First, we'll define the term "protocol" and compare that to a standard. Then we'll define "layer" and how a layered architecture operates, and provide an overview of the name, purpose and function of each of the seven layers in the OSI model.
Then, we'll go back through the story more slowly, with one lesson for each of the layers, examining in greater detail the functions that have to be performed and giving examples of protocols and how and where they are used to implement particular layers.
The result is a protocol stack, one protocol on top of another on top of another to fulfill all of the required functions. To make this more understandable, this course ends with the famous FedEx Analogy illustrating the concepts using company-to-company communications, and an analogy of Babushka dolls to illustrate how the protocol headers are nested at the bits level.
On completion of this course, you will be able to:
On completion of this course, you will be able to explain:
MPLS and Carrier Networks is a comprehensive, up-to-date course on the networks companies like AT&T build and operate, how they are implemented, the services they offer, and how customers connect to the network.
The IP packets and routing of the previous course is one part of the story. Performance guarantees, and methods for quality of service, traffic management, aggregation and integration is another big part of the story, particularly once we leave the lab and venture into the real world and the business of telecommunications services.
We'll begin by establishing a basic model for a customer obtaining service from a provider, defining Customer Edge, Provider Edge, access and core, and a Service Level Agreement: traffic profile vs. transmission characteristics.
Next, we'll understand virtual circuits, a powerful tool used for traffic management and how they are implemented with MPLS, explaining the equipment, jargon and principles of operation.
Without bogging down on details, we’ll cut through buzzwords and marketing to demystify:
Teracom is an Accredited Training Partner of the Telecommunications Certification Organization, authorized to administer exams for TCO certifications on the myTeracom Learning Management System and award TCO Certifications.
TCO Certification is proof of your knowledge of telecom, datacom and networking fundamentals, jargon, buzzwords, technologies and solutions.
It's backed up with a Certificate suitable for framing - plus a personalized Letter of Reference / Letter of Introduction detailing the knowledge your TCO Certification represents and inviting the recipient to contact Teracom for verification.
You may list Teracom Training Institute as a reference on your résumé if desired.
Each course has a course exam, consisting of ten multiple-choice questions chosen at random from a pool and shuffled in order. Passing the course exams proves your knowledge of these topics and results in your certification as a Certified Telecommunications Network Specialist.
Your Certificate and Letter of Reference / Letter of Introduction will be immediately available for download from your Dashboard in the myTeracom Learning Management System. You may also order a signed and sealed Certificate by airmail.
Choosing the "Unlimited Plan" at registration allows you to repeat courses and/or exams at no additional charge – which means guaranteed to pass if you're willing to learn.
Alternatively, if you like this discounted package of courses, but don't need the certification – or don't feel like writing exams – no problem! Take the Telecom, Datacom and Networking for Non-Engineers course package, which includes the same courses as the CTNS certification package, without the certification exams.
One benefit of TCO certification is differentiating yourself from the rest of the crowd when applying for a job or angling for a promotion.
The knowledge you gain taking Teracom's Online Courses, confirmed with TCO Certification, is foundational knowledge in telecommunications, IP, networking and wireless: fundamental concepts, mainstream technologies, jargon, buzzwords, and the underlying ideas - and how it all fits together.
This type of knowledge and preparation makes you an ideal candidate to hire or promote to a task, as you will be able to build on your knowledge base to quickly get up to speed and work on a particular project - then have the versatility to work on subsequent projects.
TCO Certification will help demonstrate you have this skill... a desirable thought to have in your potential manager's mind.
Take advantage of these courses for individual learning, a team, or for an entire organization.
The scalable myTeracom Learning Management System can register and manage all of your people through their courses, lessons and exams, and generate management reports showing progress and scores with the click of a button.
For larger organizations, the courses and exams can also be licensed and deployed on an organization's internal LMS.
Teracom certification packages are an extremely cost-effective way of implementing consistent, comprehensive telecommunications and networking technology fundamentals training, ensuring that both existing resources and new hires are up to the same speed, with a common vocabulary, framework and knowledge base.
The course exams provide concrete measurements of competency in key knowledge areas. Management can view the progress and results of all team members and export the results to Excel with the click of a button.
These reports identify skills deficiencies and strengths, and provide tangible proof of return on investment and team readiness for reports to upper management.