Wednesday, February 10, 2016

CCNAv1 Chapter 4 Notes & Review (w/ Answers) - OSI Model and Layers

Chapter 4 Notes
CCNA 1

Physical Layer
  • Purpose
    • Provides a means for transmitting bits.
Media
  • Copper Cabling
    • Sign = electrical pulse
  • Fiber Optic Cable
    • Sign is light pulses
  • Wireless
    • Sign is Radio Transmission

Standards
  • ISO
    • International organization for standardization
      • Adopted RJ connection standard. (RJ-45, etc)
  • IEEE
    • Institute of Electrical and Electronics Engineers
      • IEEE 802.3 / IEEE 802.11 (Standards of Wifi/Ethernet)
  • TIA/EIA
    • Telecommunications Industry Association / Electronic Industry Association
      • TIA-568A / TIA-568B

  • These three entities determine how one end of the signal goes to the other.


Physical Layer (2)

Signaling
  • Light, electrical, or radio transmission that represents 0 or 1.

Transmi tted two ways…
  • Synchronous
    • Associated Clock Signal

  • Asynchronous
    • No association w/ clock signal.
    • Time spacing between characters is a set value.
    • Spacing is not standard.
    • Start <- Stop Indicator Flags

Encoding
  • Data bits are changed to a “code”
  • (Old) Manchester Encoding - High Volt -> Low Volt Transmission


Non return to zero encoding has two choices;
  • 0
    • Has 24 volts

  • 1
    • Has 10 volts

Two types of encoding:
  • Manchester
  • Non-Return to 0

Which of the two (above) is most used?
  • Non-Return to 0

Signalling is done in two ways, and they are:
  • Synchronous
    • Clock speed (bit time) associated.
  • Asynchronous

Which standards organizations are responsible for?
  • OSI Model = ISO
  • 5684 Standard = TIA/EIA
  • 802.3 = IEEE
  • RJ45 = ISO
  • 802.11 = IEEE

What are the three modulation types?
  • AM
    • Amplitude Modulation
    • Amplitude of waves
  • PcM
    • Pulse Code Modulation
    • Analog converted to digital
  • FM
    • Frequency Modulation
    • Uses carrier frequency

The measure of the amount of actual data transferred is:
  • Overhead = Goodput

The time required for data to travel from end to end is?
  • Latency

Types of ethernet cable usage:
PC -> Cn: Rollover
PC -> Sw: Straight Through
Sw -> Rt: Straight Through
Rt -> Rt: Crossover
802.3 = CSMA/CD
802.11 = CSMA/CA
Data Link Layer
  • Hides the media specific info from the upper layers.
  • Specify the data encapsulation type.
  • Adds a MAC address.

What does encoding do?
  • Converts data bits into a predefined code that both transmitter and receiver understand
  • Identify data bits versus control bits
  • Identify start and stop bits

You have 100 mb/s and overhead. That’s 17 mb/s. What’s the goodput?
  • 83 mb/s

Multimode Fiber
  • # / Connected Device
    • 2
  • Light Source
    • LED
  • Size
    • 50-62 Microns
  • Connectors
    • Common Patch Cords
      • SC-SC
      • ST-LC
      • LC-LC
      • SC-ST
Review Questions
1 - Multicast Message:
  • Sent to many from 1 -> 1 -> many.

2 - Broadcast Message:
  • Sent to all from 1 -> 1 -> all.

3 - What protocol segments messages and manages the segments?
  • TCP (Transport Control Protocol)

4 - There are four parts to the protocol stack for a web page. What are they?
  • Client -> HTTP, TCP, IP, & Ethernet

5 - What is meant by the perm proprietary protocols?
  • Protocol owned by a company that controls its operation and definition.

6 - What standard governs wireless connection?
  • IEEE 802.11 (g/n/ac/b)

7 - Why do we have open standard protocols?
  • Clients & Hosts w/ different OS exchanging data.

8 - What does Layer 3 do?
  • Network (IP/ICMP) encapsulated IP address.

9 - What does Layer 4 do?
  • Transport (TCP/UDP) Segments, transfers, and reassembles the data.

10 - What does Layer 5 do?
  • Session (provides services at the presentation layer)

11 - Why do we use the layered model for network communications?
  • Reduces complexity and enforces product compatibility.

12 - A PDU (Protocol Data Unit) is what?
  • Generic Term for Data at any Layer.

13 - What is the format of the data at the Data Link Layer?
  • Frame

14 - Describe the function of the ARP protocol.
  • Finds the MAC address from an IP address. (LAN) (Returns gateway IP if not local)

15 - What address is used at the Internet Layer?
  • IPs - TCP/IP

16 - Describe what the effect of an incorrect default gateway would be.
  • Can’t send messages to remote networks.


17 - What does the ISOC do?
  • Internet Society; Promotes open development and uses the internet.

18 - What does ISO do?
  • International Organization for Standards. Provided us with the OSI model, also developed international standards.

19 - What does the IANA do?
  • Internet Assigned Numbers Authority, oversees the allocation of IP addresses to ISPs.

Skipped 20, duplicate.

21 -  When a NIC decides whether to accept a frame, what address does it check?
  • Source destination IP & MAC. (It checks for it’s inbound frame MAC address)

22 - What data unit is sent from the transport layer?
  • Segment

23 - At what layer of the OSI model would you find the logical address?

  • Layer 3 Network

At what OSI layer is the PDU called a segment?
Layer 4

The PDU is called a frame at what layer?
Layer 2

At layer 3, what is the PDU called?
Packet

At what layer is the logical address added to the data?
Network

Which measurement should be greater, bandwidth or throughput?
Bandwidth

What type of fiber cable will be ticker?
Single mode

In the 902.1 family which common standards use both 2.4GHz & 5GHz?
N & AC

The two sublayers of the data link layers are?
Logical Link Control / Media Access Control

Which layer of the OSI model to the TCP/IP internet layer?
Transport

802.3 networking relies on which contention based system?
CSMA/CD

802.11 networking relies on which contention based system?
CSMA/CA

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