TM129 4-5

Question 1

4 Criteria to choose Network Media.

Answer 1

1) Distance of the Cable 2) Amount of Data and Speed 3) The Type of Environment(e.g. EMI Interferences) 4) cost of the media and installation

Question 1

Types of media to interconnect modern devices? (3)

Answer 1

We have the 1)Copper - Metal wires within cables -> Data is encoded into electrical pulses 2) Fiber-Optic - Glass or plastic fibers within cables -> Data is encoded into pulses of light 3) Wireless - Wireless Transmission -> Data is encoded via modulation of specific frequencies of electromagnetic waves.

Question 2

What are the 3 common network cables? What are some common uses of them?

Answer 2

1) UTP - Unshielded Twisted-Pair (For the home or the office, usually to connect end devices to internet LAN, easy to install, relatively cheap, made out of copper, the cables are grouped in pairs, twisted together to reduce interference. The pairs are colored and one wire is a solid color and the other is white.) 2) Coaxial Cable (mostly used for the TVs at home or from satellite companies. Through it can pass a lot of signals at the same time, like TV, phone and internet. It is an earlier type of cable. It is expensive, difficult to install, are constructed with a single rigid copper head, has a layer of insulation, braided shielding and a protective jacket. Provides a high ferquency transmission to carry high-frequency or broadband signals.) 3) Fiber-Optic (made out of glass or plastic, human hair size, very high speeds and long distances, uses light therefore no EMI interferences, usually for the internet or to connect buildings to each other, used in backbone networks, used by large data centers, also for telephone companies. used for medical imaging, treatment and mechanical engineering inspection)

Question 3

Types of interferences for twisted-pair cables?

Answer 3

1) EMI - Electromagnetic Interferences from the environment. 2) crosstalk - when the UTP cables go to long distances and a signal from one pair of cables transfers to another pair of cables and changes/disrupts the signal that is being received.

Question 4

What are the two types of twisted-pair cables? Where in the world do we use them? In which situations do we use them? Common UTP Categories?

Answer 4

We have the UTP(Unshielded Twisted-Pair) and the STP(Shielded Twisted-Pair). We use UTP mostly in North America and STP mostly in Europe. UTP is cheaper to make, easier to install but can easily be interfered from EMI interferences. We mostly use them at home or at the office. STP is more expensive, more difficult to install but has more protection from EMI interferences. We mostly use STP at factories. Common UTP Categories are: Cat 3 UTP, Cat 5 UTP and Cat 5e UTP

Question 5

What are the most common connectors for UTP cables?

Answer 5

RJ-45 used in most devices and the older RJ-11 used mostly for fax and analog phones.

Question 6

Did coax cables replace UTP or did UTP replace coax cables? Why?

Answer 6

UTP replaced coax cables even though coax cables can have improved data carrrying capabilities, because UTP cables are easier to install, cheaper to make and easier to troubleshoot.

Question 7

Explain the Coax Construction:

Answer 7

1) Termination: Coax is usually terminated with a BNC(is a crimped down connector and is considered a stronger connection) or F-series connector(is a screw-on connector).
2) Braid: a metallic braid made of aluminum or foil helps to shield EMI and RFI
3) Insulator: usually made of plastic, protects from EMI or RFI and provides streng to the cable, to be more pliable(eykamptos)
4) Conductor - single center conductor, most of the time made out of copper, though aluminum can be used as well.

Question 8

Explain the Fiber-Optic Construction:

Answer 8

1) Jacket - Usually a PVC(poly vinyl chloride) jacket that protects the fiber against abrasion, moisture and other contaminants. This outer jacket composition can vary depending on the cable usage.
2) Strengthening Material - Surrounds the buffer, prevents the fiber cable from being stretched when it is being pulled. The material used is often the same material to produce bulletproof vests.
3) Buffer- Used to help shield the core and cladding from damage.
4) Cladding - Made from slightlydifferent chemicals than those used to crate the core. It tends to act like a mirror by reflecting light back into the core of the fiber. This keeps the light in the core as it travels down the fiber.
5) Core - The core is actually the light transmission element at the center of the optical fiber. This core is typically silica or glass. Light pulses travel through the fiber core.

Question 9

What generates the pulses inside the fiber-optic cable?

Answer 9

Either lasers or Light Emiting Diodes(LEDs) generate the pulses.

Question 10

Which organisation is responsible for typical Ethernet installation?

Answer 10

For Typical Ethernet Installations we use the TIA/EIA organization.

Question 11

What are the two typical installations/wiring schemes of patters for Ethernet?

Answer 11

The two types of installations are 1) T568A and 2) T568B.

Question 12

What are the “unlike” and the “like” devices? What type of cable to use?

Answer 12

The “unlike” devices are devices that use different wires to receive and transmit data. We require “straight-through” cables for these devices.
The “like” devices use the same wire to receive and send data. We require a “crossover cable”, it helps with reversing the transmit and receive function so that the devices can exchange data.

Question 13

Which command do we use to test connectivity with the CLI? Which command to troubleshoot?

Answer 13

We use “ping” + IP address, to test connectivity with another device. And we use “tracert” + IP address to troubleshoot where exactly the signal is being lost.

Question 14

What are the three rules/ elements that all communication methods have in common?

Answer 14

1) Sender or host. 2) Receiver or Destination 3) Transmission Medium or Channel that provides pathway

Question 15

What are the communication protocols?

Answer 15

1)method 2)language 3) Confirmation

Question 16

What are the Network Protocol characteristics?

Answer 16

1. Message Format [When a message is sent, it must use a specific format or structure. Message formats depend on the type of message and the channel that is used to deliver the message.] 2.Message Size [The rules that govern the size of the pieces communicated across the network are very strict. They can also be different, depending on the channel used. When a long message is sent from one host to another over a network, it may be necessary to break the message into smaller pieces in order to ensure that the message can be delivered reliably.] 3.Timing [Many network communication functions are dependent on timing. Timing determines the speed at which the bits are transmitted across the network. It also affects when an individual host can send data and the total amount of data that can be sent in any one transmission.] 4. Encoding [Messages sent across the network are first converted into bits by the sending host. Each bit is encoded into a pattern of sounds, light waves, or electrical impulses depending on the network media over which the bits are transmitted. The destination host receives and decodes the signals in order to interpret the message.] 5. Encapsulation [
   Each message transmitted on a network must include a header that contains addressing information that identifies the source and destination hosts, otherwise it cannot be delivered. Encapsulation is the process of adding this information to the pieces of data that make up the message. In addition to addressing, there may be other information in the header that ensures that the message is delivered to the correct application on the destination host.] 6. Message Pattern [
   Some messages require an acknowledgment before the next message can be sent. This type of request/response pattern is a common aspect of many networking protocols. However, there are other types of messages that may be simply streamed across the network, without concern as to whether they reach their destination.]

Question 17

What is a (internet) standard? Give some examples

Answer 17

A standard is a set of rules or protocols that determine how something must be done.
Examples:
A) Ethernet /WLAN -> provides connectivity to internet
B) DHCP/ICMPv6 -> provides my IP info, what network we belong to, the address of the default gateway, IP address of the DNS Server.
C) DNS Server -> gets domain name and returns and IP
D) IP and TCP -> IP-Delivery of the packets, TCP -Reliability to show a web page.

Question 18

What happens when a new internet standard is proposed? From who are they managed from?

Answer 18

When a new standard is proposed then each stage of the development and approval process is recorded in a numbered Request for Comments (RFC) document so that the evolution of the standard is tracked. The RFC for internet standards are published and managed by the Internet Engineering Task Force (IETF).

Question 19

What are the 4 Network Protocols that we use when we, for example, download a page? Explain how they work.

Answer 19

[Ethernet, IP, TCP, HTTP]
Ethernet: connects NICs(Network Interface Cards) on the same network with eath other.
IP: (Internet Protocol)Governs communication from the sender to the receiver e.g. IP address, default gateaway etc.
TCP: (Transmission Control Protocol)makes sure that the information goes reliably to the destination and puts order to the packets that were sent.
HTTP: (Hypertext Transfer Protocol) Governs the exchange and transfer of the HTML files.

Question 20

What does a protocol stack show? Show an example

Answer 20

It shows the interaction between the different protocols on a device. e.g. for an internet connection:
[HTTP]
[TCP]
[IP]
[Ethernet]

Question 21

How do we build the TCP/IP Model (Protocol Stack) - The Internet Model?

Answer 21

[Application]
[Transport]
[Internet]
[Network Access]

Ethernet->IP->TCP->HTTP

Question 22

What are two basic types of models that we use to describe the functions that must occur in order for network communications to be successful?
What is the most known reference model? Describe it

Answer 22

Protocol models and Reference models.
The most known reference model is the OSI(Open Systems Interconnection) model.
[7 -Application] - contains protocols used for process-to-process communications.
[6 - Presentation] - provides for common presentation of the data transferrred between application layer services.
[5 - Session] - provices service to the presentation layer to organize its dialogue and to manage data exchange.
[4 - Transport] - defines services to segment, transfer and reassemble the data for individual communication between the end devices.
[3 - Network] - provides services to exchange the individual pieces of data over the network between identified end devices.
[2 - Data Link] - describes methods for exchanging data frames between devices over a common media.
[1 - Physical] - describes mechanical, electrical, functional and procedural means to activate, maintain, and de-activate physical connections for a bit transmission to and from a network device.

Question 23

What are the two MAIN layers of the OSI model? Why do we use them? Give some examples

Answer 23

Knowing at which layer to work on, helps us to better troubleshoot.

Upper Layer - Application(7), Presentation(6), Session(5) Examples: Network aware application, Email, Web Browsers and servers, File transfer, Name resolution

Lower Layer - Transport(4) [video and voice streaming mechanisms, firewall filtering lists], Network(3) - [IP addressing, Routing], Data Link (2) [ Network interface cards and drivers, Network switching, WAN connectivity], Physical(1) [Physical medium—copper twisted pair, fiber-optic cables, wireless transmitters—, hubs and repeaters.]

Question 24

Why do we need the TCP/IP model while we also have the OSI model? What are the key similarities?

Answer 24

The TCP/IP model and the OSI model have many similarities but visualise the interactions in a different way. The TCP/IP Model visualises the various protocols, while the OSI model visualises the discrete functions that must occur in each level.

The key similarities are:
1) OSI Layer 3, the network layer, maps directly to the TCP/IP internet layer.
2)OSI Layer 4, the transport layer, maps directly to the TCP/IP transport layer.
3) OSI Layer 5,6 and 7 map to the Application Layer of the TCP/IP model.
4) OSI Layer 2 and 1 map to the Network Access Layer of the TCP/IP layer.
5) Both the TCP/IP and OSI models are commondly used when referring to protocols at various layers.Because the OSI model separates the datalink layer from the physical layer, it is commonly used when referring to these lower layers.

Question 25

What do the ethernet protocols define? At which OSI Layer(s) is it?

Answer 25

Ethernet protocols define how data is formatted and how it is transmitted over the wired network. We use the 1st and 2nd layer of the OSI model.

Question 26

Which Institute maintains the networking standards, including Ethernet and wireless standards?

Answer 26

The Institute of Electrical and Electronic Engineer or IEEE(pronounced eye-triple-e). It has a lot of communities that approve and maintain standards for different usages.

Question 27

Which is the committee responsible for the Ethernet standards?

Answer 27

The 802.3 committee

Question 28

What does 802.3 100BASE-T represent? What are the two modern Ethernet standards?

Answer 28

802.3 100BASE-T represents the 100 Megabit Ethernet using twisted-pair cable standards. (100 is the speed in Mbps, BASE stands for baseband transmission, T stands for the type of cable, in this case, twisted-pair.)
The two modern Ethernet standards are: 2.5GBASE-T and 5GBASE-T

Question 29

How do we call the physical address of every Ethernet network interface? At which device can we find it?

Answer 29

The MAC(Media access control) is the physical address and we can find it on the NIC card.