CompTIA Network+ Cert (N10-007): Networks & Devices

Compare and contrast the characteristics of network topologies, types, and technologies

Wired topologies

• Logical vs. physical

• Star

• Ring

• Mesh

• Bus

• CAN

• SAN

This Lecture answers the question, "What's a Network?"

The dictionary defines the word network as “a group or system of interconnected people or things.” Similarly, in the computer world, the term network means two or more connected computers that can share resources such as data and applications, office machines, an Internet connection, or some combination of these.  They can also share a printer. 

Now that you're familiar with many different types of network topologies, you're ready for some tips on selecting the right one for your particular network. You also need to know about backbones and segments, which we'll cover in the very last part of this lecture.

Just as a topographical map is a type of map that shows the shape of the terrain, the physical topology of a network is also a type of map. It defines the specific characteristics of a network, such as where all the workstations and other devices are located and the precise arrangement of all the physical media such as cables.  On the other hand, the logical topologies we covered earlier delineate exactly how data moves through the network. Now, even though these two topologies are usually a lot alike, a particular network can actually have physical and logical topologies that are very different. Basically, what you want to remember is that a network's physical topology gives you the lay of the land and the logical topology shows how a digital signal or data navigates through that layout

Here is a list of the topologies you're most likely to run into these days:

• Bus

• Star

• Ring

• Mesh

• Point-to-point

• Point-to-multipoint

• Hybrid

The following CompTIA Network+ Exam Objectives are covered in this Module:

Explain devices, applications, protocols, and services at their appropriate OSI layers

• Layer 1 – Physical

• Layer 2 – Data link

• Layer 3 – Network

• Layer 4 – Transport

• Layer 5 – Session

• Layer 6 – Presentation

• Layer 7 – Application

In the very first networks, the computers involved could communicate only with other computers made by the same manufacturer. For example, companies ran either a complete DECnet solution or an IBM solution—not both together. In the late 1970s, the Open Systems Interconnection (OSI) reference model was created by the International Organization for Standardization (ISO) to break through this barrier.

The OSI model was meant to help vendors create interoperable network devices and software in the form of protocols, or standards, so that different vendors’ networks could become compatible and work together. Like world peace, it'll probably never happen completely, but it's still a great goal.

The OSI model is the primary architectural model for networks. It describes how data and network information are communicated from an application on one computer through the network media to an application on another computer. The OSI reference model breaks this approach into layers.

Let's explore this layered approach as well as how you can utilize its key concepts to troubleshoot internetworks.

In the Lecture we'll review one of the greatest functions of the OSI specifications is to assist in data transfer between disparate hosts regardless if they're Unix, Windows, or Mac based.

But keep in mind that the OSI model isn't a physical model; it's a conceptual and comprehensive yet fluid set of guidelines, which application developers utilize to create and implement applications that run on a network. It also provides a framework for creating and implementing networking standards, devices, and internetworking schemes. The OSI model has seven layers:

• Application (Layer 7)

• Presentation (Layer 6)

• Session (Layer 5)

• Transport (Layer 4)

• Network (Layer 3)

• Data Link (Layer 2)

• Physical (Layer 1)

Upon completion of this lesson, candidates should be able to:

• Describe the process of data encapsulation

• Describe how data modulation occurs

When a host transmits data across a network to another device, the data goes through encapsulation: It's wrapped with protocol information at each layer of the OSI model. Each layer communicates only with its peer layer on the receiving device.

To communicate and exchange information, each layer uses Protocol Data Units (PDUs). These hold the control information attached to the data at each layer of the model. They're usually attached to the header in front of the data field but can also be in the trailer, or end, of it.

At a transmitting device, the data-encapsulation method works like this:

1. User information is converted to data for transmission on the network.

2. Data is converted to segments, and a reliable connection is set up between the transmitting and receiving hosts.

3. Segments are converted to packets or datagrams, and a logical address is placed in the header so each packet can be routed through an internetwork. A packet carries a segment of data.

4. Packets or datagrams are converted to frames for transmission on the local network. Hardware (Ethernet) addresses are used to uniquely identify hosts on a local network segment. Frames carry packets.

5. Frames are converted to bits, and a digital encoding and clocking scheme is used

The following CompTIA Network+ Exam Objectives are covered in this Module:

1. Infrastructure

2. Given a scenario, deploy the appropriate cabling solution.

• Media types

  • Copper

  • UTP

  • STP

  • Coaxial

  • Fiber

  • Single-mode

  • Multimode

• Plenum vs. PVC

• Connector types

• Copper

  • RJ-45

  • RJ-11

  • BNC

  • DB-9

  • DB-25

  • F-type

• Fiber

  • LC

  • ST

  • SC

  • APC

  • UPC

  • MTRJ

• Transceivers

  • SFP

  • GBIC

  • SFP+

  • QSFP

• Characteristics of fiber transceivers

  • Bidirectional

  • Duplex

• Termination points

  • 66 block

  • 110 block

  • Patch panel

  • Fiber distribution panel

• Copper cable standards

  • Cat 3

  • Cat 5

  • Cat 5e

  • Cat 6

  • Cat 6A

  • Cat 7

  • RG-6

  • RG-59

• Copper termination standards

  • TIA/EIA 568a

  • TIA/EIA 568b

  • Crossover

  • Straight-through

Upon completion of this lesson, candidates should be able to:

• Compare the different types of physical media

• Describe what terminators are used on cables

A lot of us rely on wireless networking methods that work using technologies like radio frequency and infrared, but even wireless depends on a physical media backbone in place somewhere. And the majority of installed LANs today communicate via some kind of cabling, so let's take a look at the three types of popular cables used in modern networking designs:

• Coaxial

• Twisted-pair

• Fiber optic

Upon completion of this lesson, candidates should be able to:

• Describe the concept of Transmission Speed

• Describe distance and performance factors when it comes to network cables

The reason we use so many different types of cables in a network is that each type has its own set of properties that specifically make it the best to use for a particular area or purpose. Different types vary in transmission speeds, distance, duplex, noise immunity, and frequency, and I'll cover each of these next.

1. Transmission Speeds

Based on the type of cable or fiber you choose and the network that it's installed in, network administrators can control the speed of a network to meet the network's traffic demands. Admins usually permit, or would like to have, transmission speeds of up to 10 Gbps or higher on the core areas of their networks that connect various network segments. In the distribution and access areas, where users connect to switches, it's typically 100 Mbps per connection, but transmission speeds are creeping up because the traffic demand is getting higher.

2. Distance

Deciding factors used in choosing what cable type to use often come down to the topology of a network and the distance between its components. Some network technologies can run much farther than others without communication errors, but all network communication technologies are prone to attenuation—the degradation of a signal due to the medium itself and the distance signals have to travel. Some cable types suffer from attenuation more than others. For instance, any network using twisted-pair cable should have a maximum segment length of only 328 feet (100 meters).

3. Duplex

All communications are either half duplex or full duplex. The difference is whether the communicating devices can “talk” and “listen” at the same time.

During half-duplex communication, a device can either send communication or receive communication, but not both at the same time. Think walkie-talkie—when you press the button on the walkie-talkie, you turn the speaker off and you can't hear anything the other side is saying.

In full-duplex communication, both devices can send and receive communication at the same time. This means that the effective throughput is doubled and communication is much more efficient. Full duplex is typical in most of today's switched networks. I'll discuss both full and half duplex in more detail in module, “The Current Ethernet Specifications.”

4. Noise Immunity (Security, EMI)

Any time electrons are pushed through two wires next to each other, a magnetic current is created. And we can create a current in the wires. This is good because without magnetic flux, we wouldn't be using computers—the power that surges through them is a result of it. The bad news is that it also creates two communications issues.

First, because the wire is creating a current based on the 1s and 0s coursing through it, with the right tools in hand, people can read the message in the wire without cutting it or even removing the insulation. You've heard of this—it's called tapping the wire, and it's clearly a valid security concern. In ancient history, high-security installations like the Pentagon actually encased communication wires in lead shielding to prevent them from being tapped. STP wires make tapping a little harder, but not hard enough.

The best way to solve the magnetic-flux problem caused by electricity is to not use these wires at all. As I said, fiber-optic cables carry the signal as light on a glass or a really pure plastic strand, and light is not susceptible to magnetic flux, making fiber optics a whole lot harder to tap. It's still not impossible—you can do it at the equipment level, but you have to actually cut and then repair the cable to do that, which isn't likely to go unnoticed.

The second magnetic-flux issue comes from the outside in instead of from the inside out. Because wires can take on additional current if they're near any source of magnetism, you've got to be really careful where you run your cables. You can avoid EMI by keeping copper cables away from all powerful magnetic sources like electric motors, speakers, amplifiers, fluorescent light ballasts, and so on. Just keep them away from anything that can generate a magnetic field!

5. Frequency

Each cable type has a specified maximum frequency that gives you the transmission bandwidth it can handle. Cat 5e cable is tested to 100 MHz maximum frequency and can run 1 Gbps signals for relatively short distances. That's maxing it out, but it's still good for connecting desktop hosts at high speeds. On the other hand, Cat 6 is a 250 MHz cable that can handle 1 Gbps data flow all day long with ease. Cat 6 has a lot more twists and thicker cables, so it's best used when connecting floors of a building

Upon completion of this lesson, candidates should be able to:

• Describe the difference between T568A, T568B, and T1 cable configurations

• Identify straight-through, crossover, and rollover cable types and explain how they are employed

Ethernet cabling is an important thing to understand, especially if you're planning to work on any type of LAN. There are different types of wiring standards available:

• T568A

• T568B

• Straight-through

• Crossover

• Rolled/rollover

We will look into each one of these, and then I'll end this discussion with some examples for you.

Upon completion of this lesson, candidates should be able to:

• Compare MDF versus IDF and how they are employed

• Know what the demarc is and describe how it relates to the provider and to the consumer

MDF/IDF

The main distribution frame (MDF) is a wiring point that's generally used as a reference point for telephone lines. It's also considered the WAN termination point. It's installed in the building as part of the prewiring, and the internal lines are connected to it. After that, all that's left is to connect the external (telephone company) lines to the other side to complete the circuit. Often, another wire frame called an intermediate distribution frame (IDF) is located in an equipment or telecommunications room. It's connected to the MDF and is used to provide greater flexibility for the distribution of all the communications lines to the building. It's typically a sturdy metal rack designed to hold the bulk of cables coming from all over the building!

The following CompTIA Network+ Exam Objectives are covered in this Module:

1.1 Explain the purposes and uses of ports and protocols

• DHCP 67, 68

• DNS 53

1.2 Explain devices, applications, protocols, and services at their appropriate OSI layers

• Layer 1—Physical

• Layer 2—Data link

• Layer 3—Network

• Layer 4—Transport

• Layer 5—Session

• Layer 6—Presentation

• Layer 7—Application

1.3 Explain the concepts and characteristics of routing and switching

• Properties of network traffic

  • Broadcast domains

  • CSMA/CD

  • CSMA/CA

  • Collision domains

  • Broadcast

  • Multicast

  • Unicast

• Performance concepts

  • Traffic shaping

1.4 Given a scenario, configure the appropriate IP addressing components.

• IP reservations

1.8 Explain the functions of network services

• DNS service

  • Record types

    • A, AAA

    • TXT (SPF, DKIM)

    • SRV

    • MX

    • CNAME

    • NS

    • PTR

  • Internal vs. external DNS

  • Third-party/cloud-hosted DNS

  • Hierarchy

  • Forward vs. reverse zone

• DHCP service

  • MAC reservations

  • Pools

  • IP exclusions

  • Scope options

  • Lease time

  • TTL

  • DHCP relay/IP helper

  • IPAM

2.2 Given a scenario, determine the appropriate placement of networking devices on a network and install/configure them

• Hub

• Modems

• Wireless range extender

• VoIP endpoint

2.3 Explain the purposes and use cases for advanced networking devices

• Multilayer switch

• Load balancer

• IDS/IPS

• Proxy server

• VPN concentrator

• NGFW/Layer 7 Firewall

• VoIP PBX

• VoIP gateway

• Content filter

3.4 Given a scenario, use remote access methods.

• Modem

Upon completion of this lesson, candidates should be able to:

• Describe the difference between Layer 2 and Layer 3 devices

• Compare IPS and IDS and the methods in which you would use them

• Describe firewall appliance and how the variants are employed

• Describe different network interfaces

• Explain how DHCP works

By now, you should be fairly savvy regarding the various types of network media and connections, so it's time to learn about some of the devices they hook up to that are commonly found on today's networks.

First, I'll define the basic terms; then, later in this module, I'll show you how these devices actually work within a network. At that time, I'll give you more detailed descriptions of these devices and the terminology associated with them.

Because these devices connect network entities, they're known as connectivity devices. Here's a list of the devices and related concepts I'll be covering in this lesson:

• Network interface card (NIC)

• Hub

• Bridge

• Basic switch

• Basic router

• Basic firewall

• IDS/IPS/HIDS

• Access point

• Wireless Range extender

• Contention Methods

• Dynamic Host Configuration Protocol (DHCP) server

Upon completion of this lesson, candidates should be able to:

• Explain how to employ the different network devices and when to use them

• Describe proxy services

• Describe dedicated appliances for certain services

• Describe DNS servers and the top-level domains they cover

In addition to the network connectivity devices I've discussed with you, there are several devices that, while they may not be directly connected to a network, do actively participate in moving network data. Here's a list of them:

• Multilayer switch

• Load balancer

• DNS server

• Proxy server

• Encryption devices

• Content filter

• Analog modem

• Packet shaper

• VPN concentrator

• Media converter

• VoIP PBX

• VoIP endpoint

Upon completion of this lesson, candidates should be able to:

• Explain how to plan network segmentation and subnet

• Explain how to plan network requirements

• Describe Layer 2 and 1 devices

It's likely that at some point you'll have to break up one large network into a bunch of smaller ones because user response will have dwindled to a slow crawl as the network grew and grew. With all that growth, your LAN's traffic congestion will have reached epic proportions.