CCNA Test Prep Course – Lesson One Lesson One by lzg15357

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									                                                                       CCNA Test Prep Course – Lesson One
                                                                  Tim Davidson, MBA, CCSP, INFOSEC, MCSE, CNE
                                                                                         tim@timothydavidson.com
                                                                                       http://www.timdavidson.com



Lesson One – Introduction & OSI Model

o   Roster and Introductions

o   Why we are here
      o Scope of class
                  definition of the word “network” as it applies to this course
                      • refer to handout on “categorizing networks”
                      • two or more computers connected by media form a network
                      • used to share resources such as printers, disk space, and applications
                      • "sneakernet"

                   CCNA
                     • syllabus, schedule and curriculum

o   Terminology
       o Media
       o EMI
       o Client/server – types of servers
       o Peer-to-peer networking
       o LAN, WAN, MAN, SAN
       o NOS
       o NICs
       o VPN – using the public Internet to communicate privately


o   The OSI networking model, 1984 by ISO
       o Pre-OSI we had the TCP/IP protocols, IBM’s Systems Network Architecture (SNA), and Digital
           Equipment’s DECNET proprietary model
       o refer to handout on “AppleTalk Reference Model”
       o refer to handout on “TCP/IP Reference Model”
       o refer to handout on “OSI Reference Model”
       o ISO recognized a need for an “open system” standard
       o The OSI model is not compulsory, but a reference model for vendors
       o Why OSI? Simplification!
       o Why OSI? Specialization!
       o Why OSI? Modularity, thus upgradeability!
       o Why OSI? Interoperability!
       o Why OSI? Standardization!




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                                                                         CCNA Test Prep Course – Lesson One
                                                                   Tim Davidson, MBA, CCSP, INFOSEC, MCSE, CNE
                                                                                          tim@timothydavidson.com
                                                                                        http://www.timdavidson.com



o   The Seven Layers of the OSI networking model
       o Peer networking

o   The Application layer
       o handles the interface between the network and the user
       o refer to handout on “Protocols and the OSI Model”
       o e.g., Telnet
       o e.g., FTP
       o e.g., Instant Message software (AIM, MSN, ICQ, Yahoo)
       o e.g., IRC (mIRC)
       o e.g., America Online (the client software)
       o e.g., Microsoft Windows File Shares
       o e.g., Microsoft Internet Explorer (a web browser)
       o e.g., Network games of Doom, Quake, Unreal (first-person 3D shooter video games)

o   The Presentation layer
       o ensures that data sent from one device is readable by the peer device
       o provides the following coding and conversion schemes:
       o data representation: standard formats for image, sound, and video
       o e.g., converts .WAV to .MP3
       o e.g., converts Sun .RAS raster graphics to .JPG.
       o e.g., converts Macintosh .PICT files to .JPG
       o QuickTime, MPEG (motion picture experts group), GIF (graphics interchange format), TIFF
           (tagged image file format), JPEG (joint photographic experts group)
       o characters
       o e.g., converts ASCII to IBM EBCDIC (see handout)
       o compression
       o encryption

o   The Session layer
       o establishes, manages, and terminates sessions
       o a “session” happens when a peer requests a service from a remote device (e.g., RPC)
       o sessions are coordinated by protocols
       o e.g., ASP (AppleTalk Session Protocol)
       o e.g., SCP (Session Control Protocol, by DECnet)
       o examples of services that need a session: ftp, telnet and http
       o controls data exchange
       o data synchronization
       o failure recovery
       o communication setup and teardown

o   Note that a web-browser performs Session, Presentation and Application layer functions all within its single
    application. Also, most NICs perform both Physical and Data Link layer functions.
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                                                                         CCNA Test Prep Course – Lesson One
                                                                   Tim Davidson, MBA, CCSP, INFOSEC, MCSE, CNE
                                                                                          tim@timothydavidson.com
                                                                                        http://www.timdavidson.com



o   The Transport layer
       o segments the data for transport into MTU size
       o error-free host-to-host “transmission” and in the proper sequence
       o detects transmission errors
       o retransmits if necessary
       o handles flow control
                    so that the transmitting device does not send more data than the receiving device can
                    process
       o multiplexing enables data from several applications to be transmitted simultaneously
                    virtual circuits are established, maintained, and terminated
       o provides messaging service for the Session layer
       o data transmission can be connection-oriented or connectionless
                    connection-oriented transmission requires that packets be acknowledged as received
                    connectionless transmission does not require acknowledgments
       o two transport protocols: TCP and UDP
       o TCP = “transmission” control protocol = ACK = connection-oriented
       o UDP = user “datagram” protocol = connectionless
                    fast, but unreliable (like the U.S. mail); other connection-less protocols include IP, ICMP,
                    DNS, TFTP and SNMP
       o refer to handout, “why use UDP”

o   The Network layer
       o logical addressing of data “packets,” such as IP, IPX, and Appletalk
       o routing
       o connectivity to remote networks
       o best path
       o e.g., Internet Protocol
       o e.g., Internet Control Message Protocol (ICMP or "ping")
       o e.g., Internet Gateway Management Protocol (IGMP)
       o e.g., IPX/SPX

o   The Data Link layer
       o LLC sublayer
                   defines how data is packaged for the network: 802.2, 802.3, 802.5 frames, etc.
                   provides error-checking via CRC
                   links the Physical layer with the higher layers




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                                                                       CCNA Test Prep Course – Lesson One
                                                                  Tim Davidson, MBA, CCSP, INFOSEC, MCSE, CNE
                                                                                         tim@timothydavidson.com
                                                                                       http://www.timdavidson.com



       o   MAC sublayer
                 defines the media access method (pulses, light emissions, waves, etc.)
                 provides a unique address for the device (MAC address)
                 12-digit hexadecimal (1 through F)
                 1st six digits is for the NIC manufacturers
                 last six digits is the unique number assigned to the device (see
                 http://standards.ieee.org/regauth/oui/index.shtml)
                 on and Ethernet or CSMA/CD network data “frames” are broadcast onto the wire and
                 channeled up every protocol stack it can find
                 networks are segmented into broadcast domains

o   The Physical layer
       o physical transmission of data across the network (mechanical, electrical, procedural)
       o cables and connectors
       o signal transmission
       o NICs – convert binary into a pulse (of electricity, light, etc.)
       o hubs, repeaters, transceivers, connectors, and wall jacks

o   Five-step data encapsulation process.
        o Data conversion (upper layers)
        o “Segmentation” header with MTUs
        o “Packet” header with logical address
        o “Frame” header with source & destination MAC addresses
        o Bit transmission, from bits to pulses

o   References
       o See OSI Reference Model at http://www.timdavidson.com.
       o See Tim’s notes on today’s topics at http://www.timdavidson.com.




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                                                                           CCNA Test Prep Course – Lesson One
                                                                    Tim Davidson, MBA, CCSP, INFOSEC, MCSE, CNE
                                                                                           tim@timothydavidson.com
                                                                                         http://www.timdavidson.com



Lesson One Labs

Lab 1.1

Relate the following networking descriptions to their correct OSI layer.


Bits                                    Frames                                   Cable

Where communications begin              Encoding                                 Best path selection

End-to-end transmission                 NIC software functions                   MAC address

CSMA/CD                                 Synchronization                          Formatting

Compression                             Voltage                                  ACK

Logical address                         Services to applications                 Hubs

Signals                                 Internetwork travel                      ASCII

Request for network services            SQL                                      Encryption

Duplex                                  Data segmentation                        MTU

CRC                                     Connectionless service

LLC                                     Datagram




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                                                                         CCNA Test Prep Course – Lesson One
                                                                    Tim Davidson, MBA, CCSP, INFOSEC, MCSE, CNE
                                                                                           tim@timothydavidson.com
                                                                                         http://www.timdavidson.com



Lab 1.2

Match the descriptions below to their correct step numbers of the data encapsulation process.

• Conversion to standard data format
• Encoding
• Frame
• Datagram
• Maximum transmission units
• Logical address
• Bit transmission
• Upper layers
• IP header
• Trailer
• Segments
• Packet creation
• Pulses
• Physical address



  Step #                 Event                                       Descriptions

     1              data conversion


     2        segmentation header added


                  packet creation with
     3
                    network header

                frame header and trailer
     4
                    for network link


     5               bit transmission




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                                                                         CCNA Test Prep Course – Lesson One
                                                                    Tim Davidson, MBA, CCSP, INFOSEC, MCSE, CNE
                                                                                           tim@timothydavidson.com
                                                                                         http://www.timdavidson.com



Lab 1.3

    1. Run the command ipconfig /all at the DOS prompt, and answer the following questions:

             a. What type of NIC is in the computer?

             b. What is the MAC (adapter) address?

             c. Which part of the MAC address is the OUI?

             d. Which part of the MAC address is the serial number?

             e. What is the IP address?

             f.   What is the subnet mask?

             g. What is the default gateway?

    2. Open a Web browser and go to http://standards.ieee.org/regauth/oui.

             a. In the OUI Search for “Cisco.”

             b. What is one of the six-digit OUI codes for Cisco?

             c. Search for “3COM.”

             d. What is one of the six-digit OUI codes for 3COM?

Lab 1.4

Match the terms in the left column to their correct Transport method, either connection or connectionless:

                                                                    Transport Method
                   Description                                (connection or connectionless)
ACK

Unreliable

U.S.P.S. mail is an example

Reliable

Datagram

Return receipt for mail is an example

Session



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                                                                         CCNA Test Prep Course – Lesson One
                                                                    Tim Davidson, MBA, CCSP, INFOSEC, MCSE, CNE
                                                                                           tim@timothydavidson.com
                                                                                         http://www.timdavidson.com



Chapter 1 Solutions
Review Questions
1. Which of the following best describes the Presentation layer?
     a. Establishes, maintains, and manages sessions between applications
     b. Translates, encrypts, or prepares data from the Application layer for network transmission
     c. Handles routing information for data packets
     d. Provides the electrical and mechanical transmission of data
     e. Handles link control and uses the MAC address on the network interface card (NIC)
2. Which of the following best describes the Network layer?
     a. Handles routing information for data packets
     b. Provides the electrical and mechanical transmission of data
     c. Handles link control and uses the MAC address on the NIC
     d. Establishes, maintains, and manages sessions between applications
     e. Translates, encrypts, or prepares data from the Application layer for network transmission
3. Which of the following best describes the Session layer?
     a. Translates, encrypts, or prepares data from the Application layer for network transmission
     b. Handles routing information for data packets
     c. Provides the electrical and mechanical transmission of data
     d. Handles link control and uses the MAC address on the NIC
     e. Establishes, maintains, and manages sessions between applications
4. Which of the following best describes the Transport layer?
     a. Provides the electrical and mechanical transmission of data
     b. Handles link control and uses the MAC address on the NIC
     c. Establishes, maintains, and manages sessions between applications
     d. Segments and reassembles data and provides either connection-oriented or connectionless
        communications
     e. Translates, encrypts, or prepares data from the Application layer for network transmission
5. Which of the following best describes the Data Link layer?
     a. Provides the electrical and mechanical transmission of data
     b. Handles link control and uses the MAC address on the NIC
     c. Establishes, maintains, and manages sessions between applications
     d. Translates, encrypts, or prepares data from the Application layer for network transmission
     e. Handles routing information for data packets
6. Which of the following best describes the Physical layer?
     a. Establishes, maintains, and manages sessions between applications
     b. Translates, encrypts, or prepares data from the Application layer for network transmission
     c. Provides the electrical and mechanical transmission of data
     d. Handles link control and uses the MAC address on the NIC
     e. Provides network services to the user
7. Which of the following best describes the Application layer?
     a. Establishes, maintains, and manages sessions between applications
     b. Translates, encrypts, or prepares data for network transmission
     c. Provides network services to the user
     d. Handles routing information for data packets
     e. Provides the electrical and mechanical transmission of data




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                                                                          CCNA Test Prep Course – Lesson One
                                                                     Tim Davidson, MBA, CCSP, INFOSEC, MCSE, CNE
                                                                                            tim@timothydavidson.com
                                                                                          http://www.timdavidson.com



8. Which of the following accurately describe the Media Access Control (MAC) address? (Choose all that apply.)
     a. It is a physical number set during the manufacturing process.
     b. This address is a layer in a network segment.
     c. MAC addresses contain 12 hexadecimal numbers.
     d. Computers use this address to uniquely identify themselves on the network.
     e. An IP address is one example of this type of address.
9. Which of the following accurately describe the network address? (Choose all that apply.)
     a. It is a physical number set during the manufacturing process.
     b. This address is used when routing communications between different network segments.
     c. The Data Link layer uses this address.
     d. This address is set at layer 3 of the OSI model.
     e. An example of this type of address is an IP address.
10. Connection-oriented services are also known as __________ services.
     a. reliable
     b. unreliable
     c. datagram
11. Connectionless services are also called __________ services.
     a. reliable
     b. acknowledgment
     c. unreliable
12. Which of the following services receive an acknowledgment from the destination? (Choose all that apply.)
     a. Datagram
     b. Reliable
     c. Connection-oriented
     d. Connectionless
     e. Unreliable
13. Place the following steps of data encapsulation in their correct descending order:
     a. Frame headers and trailers added
     b. Segment header added
     c. Bit transmission
     d. Packet creation and network header
     e. Data conversion
     The correct order is e, b, d, a, c.
14. Which of the following correctly defines a WAN?
     a. A network contained within a single geographic location and usually connected by a privately
        maintained medium
     b. A network spread over multiple geographic areas and usually connected by publicly and privately
        maintained media
     c. A network spread over a single metropolitan area
15. Which of the following best describes a LAN?
     a. A network that is contained in a single geographic area such as a building or floor in a building
     b. A countywide network that spans multiple geographic locations
     c. A large network that is connected by both publicly and privately maintained cabling spread over multiple
        geographic regions




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                                                                            CCNA Test Prep Course – Lesson One
                                                                      Tim Davidson, MBA, CCSP, INFOSEC, MCSE, CNE
                                                                                             tim@timothydavidson.com
                                                                                           http://www.timdavidson.com



16. Which of the following reasons for providing a layered OSI architecture are correct? (Choose all that apply.)
     a. To provide design modularity, which allows upgrades to a specific layer to remain separate from the
        other layers
     b. To simplify the networking model by dividing it into 14 layers and 12 sublayers
     c. To discourage interoperability between disparate networking models
     d. To enable programmers to specialize in a particular layer
     e. To allow for standardized interfaces from networking vendors
17. On a network, computers must use a common ___________ in order for communication to occur.
     a. protocol
     b. operating system
     c. manufacturer
     d. hardware platform
18. Before networks, what did people use to transfer files?
     a. Sneakernet
     b. Protocols
     c. Interface cards
     d. Ethernet
19. A protocol is to a computer as a(n) ___________ is to a person.
     a. identity
     b. personality
     c. language
     d. personal philosophy
20. Which of the following are network hardware? (Choose all that apply.)
     a. NIC
     b. NOS
     c. LLC
     d. Network media
     e. Connectors
21. Which of the following are network software? (Choose all that apply.)
     a. Components that map to the Application layer of the OSI model
     b. NIC
     c. NOS
     d. Media connectors
22. All networking vendors follow the OSI model and design seven-layer architectures. True or False?
23. Communications on a network originate at the _____________.
     a. destination
     b. breaker
     c. peak
     d. source
24. Transmitted signals are bound for a _____________ computer.
     a. destination
     b. breaker
     c. peak
     d. source




                                                       10
                                                                          CCNA Test Prep Course – Lesson One
                                                                     Tim Davidson, MBA, CCSP, INFOSEC, MCSE, CNE
                                                                                            tim@timothydavidson.com
                                                                                          http://www.timdavidson.com



25. Information transmitted on a network is called a(n) _____________.
      a. package
      b. expresser
      c. data destination
      d. data packet
      e. E-pack
26. Which of the following are layers of the OSI model? (Choose all that apply.)
     a. OSI
     b. Physical
     c. IEEE
     d. Data Link
27. Which layer of the OSI model is responsible for media access and packaging data into frames?
     a. Network layer
     b. Physical layer
     c. Data Link layer
     d. Transport layer
28. At which layer of the OSI model will encryption and compression occur?
     a. Presentation layer
     b. Session layer
     c. Application layer
     d. Network layer
29. Which of the following lists the layers of the OSI model from layer 7 to layer 1?
     a. Application, Session, Transport, Network, Presentation, Data Link, Physical
     b. Physical, Data Link, Network, Transport, Session, Presentation, Application
     c. Application, Presentation, Session, Transport, Network, Data Link, Physical
     d. Presentation, Application, Session, Network, Transport, Data Link, Physical
30. The __________ layer is responsible for finding the best path to route packets within an internetwork.
     a. Transport
     b. Network
     c. Session
     d. Data Link




                                                       11
                                                                           CCNA Test Prep Course – Lesson One
                                                                     Tim Davidson, MBA, CCSP, INFOSEC, MCSE, CNE
                                                                                            tim@timothydavidson.com
                                                                                          http://www.timdavidson.com




Case Projects
Case Project 1
Moe may not realize that without using the OSI reference model as a discussion tool, he probably could not
have learned enough about protocols to pass the Network+ exam. Learning about network operation without this
frame of reference would be nearly impossible. Also, this knowledge often helps in troubleshooting the network.
If something goes wrong on the network, understanding the layer at which the nonfunctioning element is
associated can help you solve the problem.
Case Project 2
Although data encapsulation is often described in terms of the application, transport, network, data link, and
physical layers, it can actually occur at all layers. Encapsulation is the process of wrapping the header
information from the higher layer with the header of the next-lower layer. The five steps of data encapsulation
are:
i) data conversion at the upper layers (5,6,7)
ii) segmentation at layer 4
iii) packet creation at layer 3
iv) frame encapsulates packet at layer 2
v) bit transmission at layer 1
Case Project 3
The data link layer controls access to the physical media, however, it is not part of the physical layer. This is
especially confusing since the MAC address is also known as the hardware or physical address. The MAC
address is called the hardware or physical address because it is burned onto the NIC and cannot be changed.
The only way to change the MAC address of a device is to change the NIC card in the device. The MAC
address is more specifically operating at the MAC sublayer of the data link layer. There is also the logical link
control (LLC) sublayer in the data link layer. The LLC is concerned with the linking function between the lower
layers and upper layer protocols.
Case Project 4
From 1 to 7: "Please do not throw sausage pizza away."
From 7 to 1: "All people seem to need data processing."
Physical: encoding, bit transmission, signal
Data Link: frame, MAC address, access method
Network: packet, routing, best path
Transport: segmentation, connection-oriented vs. connectionless, error-free delivery
Session: synchronization, half-duplex/full duplex, communications setup and teardown
Presentation: formatting, compression, encryption
Application: user/application services, communications origination, FTP/Telnet
Case Project 5
Students could draw two OSI models side by side. An arrow could come down from the top of the first model
(source) to the physical layer and then back up the second model (destination) to the application layer. In some
way it could be illustrated that the data "grows" as it is encapsulated with information with each successive layer
as it goes down the first stack. Then, the headers are stripped off one by one as the data travels up the second
(destination) stack until it reaches the user on top of the second model.




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