Protocols and Models

Question 1

Communication Rules

Answer 1

Necessary rules for successful communication.

Networks can vary in size and complexity. It is not enough to have a connection,
devices must agree on “how” to communicate.
There are three elements to any communication:
* There will be a source (sender).
* There will be a destination (receiver).
* There will be a channel (media) that provides for the path of communications to
occur.

Question 2

Communications Fundamentals

Answer 2

Networks can vary in size and complexity. It is not enough to have a connection,
devices must agree on “how” to communicate.
There are three elements to any communication:
* There will be a source (sender).
* There will be a destination (receiver).
* There will be a channel (media) that provides for the path of communications to
occur.

Question 3

Rule Establishment

Answer 3

• Individuals must use established rules or agreements to govern the conversation.
• The first message is difficult to read because it is not formatted properly. The second shows
  the message properly formatted

Protocols must account for the following requirements:
* An identified sender and receiver
* Common language and grammar
* Speed and timing of delivery
* Confirmation or acknowledgment requirements

Question 4

Data Encapsulation

Answer 4

Encapsulation is the process where protocols add their information to the data.

• At each stage of the process, a PDU has a
  different name to reflect its new functions.

                                   * There is no universal naming convention for 
                                    PDUs, in this course, the PDUs are named 
                                    according to the protocols of the TCP/IP 
                                    suite. 
  
                                   * PDUs passing down the stack are as 
                                    follows:
                                    1. Data (Data Stream)
                                    2. Segment
                                    3. Packet
                                    4. Frame
                                    5. Bits (Bit Stream)

• Encapsulation is a top down
  process.
• The level above does its
  process and then passes it
  down to the next level of the
  model. This process is
  repeated by each layer until
  it is sent out as a bit stream.
• Data is de-encapsulated as it moves up
  the stack.
• When a layer completes its process,
  that layer strips off its header and
  passes it up to the next level to be
  processed. This is repeated at each
  layer until it is a data stream that the
  application can process.
  1. Received as Bits (Bit Stream)
  2. Frame
  3. Packet
  4. Segment
  5. Data (Data Stream)

Question 5

Network Protocol Requirements

Answer 5

Common computer protocols must be in agreement and include the following
requirements:
* Message encoding
* Message formatting and encapsulation
* Message size
* Message timing
* Message delivery options

Question 6

Message Encoding

Answer 6

• Encoding is the process of converting information into another acceptable form for
  transmission.
• Decoding reverses this process to interpret the information.

Question 7

Message Formatting and Encapsulation

Answer 7

• 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.

Question 8

Message Size

Answer 8

Encoding between hosts must be in an appropriate format for the medium.
* Messages sent across the network are converted to bits
* The bits are encoded into a pattern of light, sound, or electrical impulses.
* The destination host must decode the signals to interpret the message.

Question 9

Message Timing

Answer 9

Message timing includes the following:
Flow Control – Manages the rate of data transmission and defines how much information
can be sent and the speed at which it can be delivered.
Response Timeout – Manages how long a device waits when it does not hear a reply from
the destination.
Access method - Determines when someone can send a message.
* There may be various rules governing issues like “collisions”. This is when more than one
device sends traffic at the same time and the messages become corrupt.
* Some protocols are proactive and attempt to prevent collisions; other protocols are
reactive and establish a recovery method after the collision occurs.

Question 10

Message Delivery Options

Answer 10

Message delivery may one of the following methods:
* Unicast – one to one communication
* Multicast – one to many, typically not all
* Broadcast – one to all

Note: Broadcasts are used in IPv4 networks, but are not an option for IPv6. Later we will also
see “Anycast” as an additional delivery option for IPv6.

Question 11

Managing Message Size

Answer 11

Converting messages into transmissible bits.

Question 12

Network protocols

Answer 12

Define a common set of rules.

Question 13

Network Protocol Functions

Answer 13

• Devices use agreed-upon protocols
  to communicate .
  • Protocols may have may have one
    or functions.

Question 14

Addressing

Answer 14

Identifies sender and receiver

Question 15

Reliability

Answer 15

Provides guaranteed delivery

Question 16

Flow Control

Answer 16

Ensures data flows at an efficient rate

Question 17

Sequencing

Answer 17

Uniquely labels each transmitted segment of data

Question 18

Error Detection

Answer 18

Determines if data became corrupted during transmission

Question 19

Application Interface

Answer 19

Process-to-process communications between network applications

Question 20

Protocol Interaction

Answer 20

• Networks require the use of several
  protocols.
  • Each protocol has its own function and format

Question 21

Hypertext Transfer

Answer 21

Governs the way a web server and a web client interact

Question 22

Protocol (HTTP)

Answer 22

Defines content and format

Question 23

Transmission Control

Answer 23

Manages the individual conversations

Question 24

Protocol (TCP)

Answer 24

Provides guaranteed delivery

Question 25

Internet Protocol (IP)

Answer 25

Delivers messages globally from the sender to the receiver

Question 26

Ethernet

Answer 26

• Delivers messages from one NIC to another NIC on the same Ethernet Local
• Area Network (LAN)