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85 Cards in this Set

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What are the three common elements of network communication methods?
Message, Destination, and Channel
Define: Channel?
A channel consists of the media that carries a signal over a network.
Currently, how are messages efficiently communicated over a network?
By process of segmentation
Define: Segmentation
The process in which messages are broken into smaller pieces (segments) that can be transported across a medium.
What are the two primary benefits of segmentation?
Multiplexing and decreased network congestion.
Define: Multiplexing
Multiplexing allows interleaving of segments so users can share the bandwidth.
What is the downside of using segmentation and multiplexing?
Time consuming
What are the components of a Network?
Devices, Media, Services, and Processes.
Define: End Device
Equipment that is either the source or the destination of a message on a network.
Define: Host
An end device that can both send and receive messages.
Define: Client
An end device that requests information and services
What is the role of an end device?
To be the source, or the destination of a message on a network.
Define: Host Address
A unique identifier used by hosts to deliver messages to other hosts on a network.
Define: Physical Address
A Data Link Layer address. For example, a MAC address.
Define: Intermediary Device
A device which connects individual hosts to a network and can connect multiple individual networks to form an internetwork. Also manages network data flow.
Define: Network Access Devices
Connects end users to their network. Examples are hubs and switches. Intermediary.
Define: Internetwork Devices
Conencts one network to one or more other networks. A router is a main example. Intermediary.
Define: Communication Servers
Routes services such as IPTV and wireless broadband. Intermediary.
Define: Modems
Connects users to servers and networks through telephone or cable. Intermediary.
Define: Security Devices
Secures the network with devices such as firewalls. Intermediary.
What six functions to the processes running on intermediary devices perform?

Hint: R.M.N.D.C.P.
1. Regenerate and retransmit data signals.

2. Maintain information about what pathways exist through the network and internetwork.

3. Notify other devices of error and communication failures.

4. Direct data along alternate pathways when there is a link failure.

5. Classify and direct messages according to QoS priorities.

6. Permit or deny the flow of data, based on security settings.
What are the three main types of media used in a network today?
Copper, Fiber-Optic, Wireless
Define: Encoding
Refers to the way data is converted into patters of electrical, light, or electromagnetic energy, dependent of which type of media is being used.
What type of encoding does Copper use?
Electrical pulses
What type of encoding does Fiber-Optic use?
Light pulses
What type of encoding does Wireless use?
Electromagnetic waves
When choosing network media, what four factors must administrators consider?

Hint: D.E.B.C.
1. The distance the media can carry the signal

2. The environment in which the media will operate

3. The bandwidth requirements for users

4. The cost of installation, and compatible devices
What are the three basic differences between different networks types?
1. The size of the area covered

2. The number of users connected

3. The number and types of services available.
Define : Local-Area Network (LAN)
A network under the control of a common administration.
Define : Wide-Area Network
A network of geographically separated LANs. There are usually no end users on WANs.
Define: Telecommunications Service Provider (TSP)
Provides WAN services for companies.
Define: Internetwork
A collection of two or more LANs connected by WANs. The most popular Internetwork is the Internet. Also known as a "data network" or simply "network."
Define: Intranet
A private network, closed to public access.
Define: Internet Service Providers (ISP)
Provide end users with internet access. May also provide TSP services.
Define: Protocol
A rule that defines what tasks a service or device will perform.
Define: Protocol Suite
A group of protocols that work together to ensure successful host-to-host communication.
What processes do Network Protocols describe?
1. The format or structure of the message

2. The method by which networking devices share information about pathways with other networks

3. How and when error and system messages are passed between devices

4. The setup and termination of data transfer sessions
Individual protocols in a protocol suite may be vendor-specific and proprietary.

In this context, define "Proprietary"
One company or vendor controls the definition of the protocol and how it functions.
Define : Hypertext Transfer Protocol (HTTP)
An Application Protocol which defines the content and formatting of the requests and responses exchanged between the web client and web server.
Define: Transmission Control Protocol (TCP)
A Transport Protocol which manages the individual conversations between web servers and their clients. TCP segments messages and controls segment size and data flow between web servers and their clients.
Define: Internet Protocol (IP)
A Network Layer protocol which is responsible for taking the formatted segments from TCP, encapsulating them into packets, assigning the appropriate addresses, and selecting the best path to the destination host.
Define: Network Access Protocols:
Network access protocols describe two primary functions, data link management and the physical transmission of data on the media. Data-link management protocols take the packets from IP and format them to be transmitted over the media. The standards and protocols for the physical media govern how the signals are sent over the media and how they are interpreted by the receiving clients. Transceivers on the network interface cards implement the appropriate standards for the media that is being used.
Explain "Technology Independent Protocols"
Because protocols specify ONLY network functionality, and NOT the underlining technology, different types of technologies can utilize the same protocol.
Define: Layered Model
A layered model depicts the operation of the protocols occurring within each layer, as well as the interaction with the layers above and below it.
What are the four benefits of using a Layered Model to describe network protocols and operations?

Hint : A.F.P.P
1. Assists in protocol design, because protocols that operate at a specific layer have defined information that they act upon and a defined interface to the layers above and below.

2. Fosters competition because products from different vendors can work together.

3. Prevents technology or capability changes in one layer from affecting other layers above and below.

4. Provides a common language to describe networking functions and capabilities.
What are the two basic types of networking models?
Protocol Models and Reference Models
Define : Protocol Model
A model which describes the functions that occur at each layer
Define: Reference Model
Provides a common reference for maintaining consistency within all types of network protocols and services. The OSI is an example of a reference model.
Which model is formerly known as the "Internet Model?"
The TCP/IP model.
Define: Open Standard
Not proprietary
True or False

The TCP/IP model is not an open standard.
False
In the TCP/IP model, what are the seven steps for a complete communication process?

Hint : C.S.G.T.R.D.P.
1. Creation of data at the Application layer of the originating source end device

2. Segmentation and encapsulation of data as it passes down the protocol stack in the source end device

3. Generation of the data onto the media at the Network Access layer of the stack

4. Transportation of the data through the internetwork, which consists of media and any intermediary devices

5. Reception of the data at the Network Access layer of the destination end device

6. Decapsulation and reassembly of the data as it passes up the stack in the destination device

7. Passing this data to the destination application at the Application layer of the destination end device
Define: Encapsulation
The process of inputing data in a particular protocol header.
Define : Protocol Data Unit (PDU)
A term used to describe data packets as they move from one protocol layer to another.
List the order of PDUs, from top to bottom, as it travels down the protocol stack.
Data, Segment, Packet, Frame, Bits
Which PDU is associated with the Application Layer?
Data
Which PDU is associated with the Transport layer?
Segment
Which PDU is associated with the Internetwork Layer?
Packet
Which PDU is associated with the Network Access Layer?
Frame
Which PDU is associated with the Physical Layer?
Bits
Explain the process of sending and receiving data packets across a protocol stack.
1. The Application layer protocol begins the process by delivering data to the Transport layer.

2. There the application data is broken into TCP segments. Each TCP segment is given a label, called a header, containing information about which process running on the destination computer should receive the message. It also contains the information to enable the destination process to reassemble the data back to its original format.

3. The Transport layer encapsulates the data within the segment and sends it to the Internet layer, where the IP protocol is implemented. Here the entire TCP segment is encapsulated within an IP packet, which adds another label, called the IP header. The IP header contains source and destination host IP addresses, as well as information necessary to deliver the packet to its corresponding destination process.

4. Next, the IP packet is sent to the Network Access layer Ethernet protocol where it is encapsulated within a frame header and trailer. Each frame header contains a source and destination physical address. The physical address uniquely identifies the devices on the local network. The trailer contains error checking information.

5. Finally the bits are encoded onto the Ethernet media by the server NIC.

6. This process is reversed at the receiving host. The data is decapsulated as it moves up the stack toward the end user application.
True of False

The OSI model is a reference model.
True
From top to bottom, what are the seven layers of the OSI Model?
Application, Presentation, Session, Transport, Network, Data Link, Physical.
Define: Application Layer
Performs services for the applications used by end users.
Define: OSI Presentation Layer
Provides data format information to the application layer.

For example, the presentation layer informs the application layer whether there is encryption, or whether it is a .jpg picture.
Define: OSI Session Layer
Manages sessions between users.

For example, the session layer synchronize multiple web sessions of voice and video data in a web conference.
Define: OSI Transport Layer
Defines data segments and numbers them at the source, transfers the data, and reassembles the data at the destination.

Other functions include acknowledgement, error recovery, and sequencing.

TCP and UDP are associated with this layer.
Define: OSI Network Layer
Creates and addresses packets for end-to-end delivery to other devices across a network.
Define: OSI Data Link Layer
Creates and addresses frames for host-to-host delivery on the local LANs and between WAN devices.
Define: OSI Physical Layer
Defines media specifications, and transmits binary data over media between devices.
What are the key parallels between the OSI and TCP/IP models?
The Transport and Network Layers.
Which identifiers do the Upper Layers use?
Encoded Application Data
Which identifiers does the Transport Layer use?
Destination and Source Port number
Which identifiers does the Network Layer use?
Destination and Source Logical Network Address
Which identifiers does the Data Link Layer use?
Destination and Source Physical Address.
Which identifiers does the Physical Layer use?
Timing and synchronization bits.
During the process of encapsulation, address identifiers are added to the data as it travels down the protocol stack on the source host.

Explain the multiple layers of addressing which ensure its delivery.
The first identifier, the host physical address, is contained in the header of the Layer 2 PDU, called a frame. Layer 2 is concerned with the delivery of messages on a single local network. The Layer 2 address is unique on the local network and represents the address of the end device on the physical media. In a LAN using Ethernet, this address is called the Media Access Control (MAC) address.

When two end devices communicate on the local Ethernet network, the frames that are exchanged between them contain the destination and source MAC addresses.

Once a frame is successfully received by the destination host, the Layer 2 address information is removed as the data is decapsulated and moved up the protocol stack to Layer 3.
At the boundary of each local network, which intermediary device, decapsulates the frame to read the destination host address contained in the header of the packet, the Layer 3 PDU.
The Router
Explain the process of how the layer 3 protocol moves data from one local network to another local network within an internetwork.
In the TCP/IP protocol suite, every IP host address contains information about the network where the host is located.

At the boundary of each local network, an intermediary network device, usually a router, decapsulates the frame to read the destination host address contained in the header of the packet, the Layer 3 PDU.

Routers use the network identifier portion of this address to determine which path to use to reach the destination host.

Once the path is determined, the router encapsulates the packet in a new frame and sends it on its way toward the destination end device.

When the frame reaches its final destination, the frame and packet headers are removed and the data moved up to Layer 4.
Explain the process of how layer 4 directs data to the proper conversation.
Each application or service is represented at Layer 4 by a port number. A unique dialogue between devices is identified with a pair of Layer 4 source and destination port numbers that are representative of the two communicating applications.

When the data is received at the host, the port number is examined to determine which application or process is the correct destination for the data.
Describe the structure of a network, including the devices and media that are necessary for successful communications.
Data networks are systems of end devices, intermediary devices, and the media connecting the devices, which provide the platform for the human network.
Explain the function of protocols in network communications.
Devices, and the services that operate on them, can interconnect in a global and user-transparent way because they comply with rules and protocols.
Explain the advantages of using a layered model to describe network functionality.
The use of layered models as abstractions means that the operations of network systems can be analyzed and developed to cater the needs of future communication services.
Describe the role of each layer in two recognized network models: The TCP/IP model and the OSI model.
The most widely-used networking models are OSI and TCP/IP. Associating the protocols that set the rules of data communications with the different layers is useful in determining which devices and services are applied at specific points as data passes across LANs and WANs.

Applying models allows various individuals, companies, and trade associations to analyze current networks and plan the networks of the future.
Describe the importance of addressing and naming schemes in network communications.
As it passes down the stack, data is segmented into pieces and encapsulated with addresses and other labels. The process is reversed as the pieces are decapsulated and passed up the destination protocol stack.

Without proper addressing and naming schemes, conversation between network devices would be impossible.