NETACAD MODULE 3

Question 1

What requirements must protocols account for to successfully deliver a message?

Answer 1

An identified sender and receiver
Common language and grammar
Speed and timing of delivery
Confirmation or acknowledgment requirements

Question 2

What is encoding?

Answer 2

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

Encoding between hosts must be in an appropriate format for the medium. Messages sent across the network are first converted into bits by the sending host. Each bit is encoded into a pattern of voltages on copper wires, infrared light in optical fibers, or microwaves for wireless systems. The destination host receives and decodes the signals to interpret the message.

Question 3

Explain message formatting and encapsulation

Answer 3

When a message is sent from source to destination, 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.
Similar to sending a letter, a message that is sent over a computer network follows specific format rules for it to be delivered and processed. As application data is passed down the protocol stack on its way to be transmitted across the network media, various protocol information is added at each level. This is known as the encapsulation process.

Internet Protocol (IP) is a protocol with a similar function to the envelope example. In the figure, the fields of the Internet Protocol version 6 (IPv6) packet identify the source of the packet and its destination. IP is responsible for sending a message from the message source to destination over one or more networks.

Question 4

How does message size affect the transmission of a message?

Answer 4

The size restrictions of frames require the source host to break a long message into individual pieces that meet both the minimum and maximum size requirements. The long message will be sent in separate frames, with each frame containing a piece of the original message. Each frame will also have its own addressing information. At the receiving host, the individual pieces of the message are reconstructed into the original message.

Question 5

What does message timing entail?

Answer 5

• Flow Control - This is the process of managing the rate of data transmission. Flow control defines how much information can be sent and the speed at which it can be delivered. For example, if one person speaks too quickly, it may be difficult for the receiver to hear and understand the message. In network communication, there are network protocols used by the source and destination devices to negotiate and manage the flow of information.
• Response Timeout - If a person asks a question and does not hear a response within an acceptable amount of time, the person assumes that no answer is coming and reacts accordingly. The person may repeat the question or instead, may go on with the conversation. Hosts on the network use network protocols that specify how long to wait for responses and what action to take if a response timeout occurs.
• Access method - This determines when someone can send a message. When a device wants to transmit on a wireless LAN, it is necessary for the WLAN network interface card (NIC) to determine whether the wireless medium is available.

Question 6

What are the three types of data communications?

Answer 6

Unicast - Information is being transmitted to a single end device.
Multicast - Information is being transmitted to a one or more end devices.
Broadcast - Information is being transmitted to all end devices.

Question 7

Describe the following functions of protocols: Addressing, Reliability, Flow Control, Sequencing, Error Detection, Application Interface

Answer 7

Addressing- This identifies the sender and the intended receiver of the message using a defined addressing scheme. Examples of protocols that provide addressing include Ethernet, IPv4, and IPv6.

Reliability- This function provides guaranteed delivery mechanisms in case messages are lost or corrupted in transit. TCP provides guaranteed delivery.

Flow control- This function ensures that data flows at an efficient rate between two communicating devices. TCP provides flow control services.

Sequencing- This function uniquely labels each transmitted segment of data. The receiving device uses the sequencing information to reassemble the information correctly. This is useful if the data segments are lost, delayed or received out-of-order. TCP provides sequencing services.

Error Detection- This function is used to determine if data became corrupted during transmission. Various protocols that provide error detection include Ethernet, IPv4, IPv6, and TCP.

Application Interface- This function contains information used for process-to-process communications between network applications. For example, when accessing a web page, HTTP or HTTPS protocols are used to communicate between the client and server web processes.

Question 8

Describe the following protocols: HTTP, TCP, IP and Ethernet

Answer 8

HyperText Transfer Protocol- Defines the content and formatting of the requsts and responses exachanged between a web server and web client

Transmission Control Protocol (TCP)- Responsible for guaranteeing the reliable delivery of information and managing flow control between the end devices

Internet Protocol (IP) - Responsible for delivering messages from the sender to the receiver. Used by routers to forward messages across multiple networks

Ethernet- Responsible for delivery of messages from one NIC to another NIC on the same Ethernet LAN

Question 9

BGP and OSPF are examples of which type of protocol?

Answer 9

Routing

Question 10

Give examples of service discovery protocols

Answer 10

DNS and DHCP

Question 11

What is a protocol suite and give a brief description

Answer 11

A protocol suite is a group of inter-related protocols necessary to perform a communication function.

One of the best ways to visualize how the protocols within a suite interact is to view the interaction as a stack. A protocol stack shows how the individual protocols within a suite are implemented. The protocols are viewed in terms of layers, with each higher-level service depending on the functionality defined by the protocols shown in the lower levels. The lower layers of the stack are concerned with moving data over the network and providing services to the upper layers, which are focused on the content of the message being sent.

Question 12

Which TCP/IP Protocols are in which layers?

Answer 12

Application- HTTP
Transport- TCP
Internet- IP
Network Access- There are no TCP/IP protocols in the network access layer. The most common network access layer LAN protocols are Ethernet and WLAN (wireless LAN) protocols

• Network access layer protocols are responsible for delivering the IP packet over the physical medium.

Question 13

Give a detailed list of TCP/IP protocols in each network layer

Answer 13

1. APPLICATION
   - Name System- DNS
   - Host Config- DHCPv4, DHCPv6, SLAAC
   - Email- SMTP, POP3(Post Office Protocol version 3. Enables clients to retrieve email from a mail server and download the email to the client’s local mail application.), IMAP(Internet Message Access Protocol. Enables clients to access email stored on a mail server as well as maintaining email on the server.)
   - File Transfer- FTP(Sets the rules that enable a user on one host to access and transfer files to and from another host over a network.), SFTP(SSH File Transfer Protocol. As an extension to Secure Shell (SSH) protocol, SFTP can be used to establish a secure file transfer session), TFTP(Trivial File Transfer Protocol. A simple, connectionless file transfer protocol with best-effort)
   - Web service- HTTP, HTTPS, REST(Representational State Transfer. A web service that uses application programming interfaces (APIs) and HTTP requests to create web applications

2.TRANSPORT
Connection oriented- TCP
Connectionless- UDP( User Datagram Protocol. Enables a process running on one host to send packets to a process running on another host.)

3. INTERNET
   - Internet Protocol- IPv4(Receives message segments from the transport layer, packages messages into packets, and addresses packets for end-to-end delivery over a network., IPv6, NAT(Network Address Translation. Translates IPv4 addresses from a private network into globally unique public IPv4 addresses.)
   - Messaging- ICMPv4( Internet Control Message Protocol for IPv4. Provides feedback from a destination host to a source host about errors in packet delivery), ICMPv6, ICMPv6 ND
   - Routing- OSPF(Open Shortest Path First. Link-state routing protocol that uses a hierarchical design based on areas. OSPF is an open standard interior routing protocol.), EIGRP( Enhanced Interior Gateway Routing Protocol. Uses a composite metric based on bandwidth, delay, load and reliability), BGP( Border Gateway Protocol. An open standard exterior gateway routing protocol used between Internet Service Providers (ISPs).)

4.NETWORK ACCESS
Address resolution- ARP(Address Resolution Protocol. Provides dynamic address mapping between an IPv4 address and a hardware address.)
Data link Protocols-Ethernet(Defines the rules for wiring and signaling standards of the network access layer.), WLAN( Wireless Local Area Network. Defines the rules for wireless signaling across the 2.4 GHz and 5 GHz radio frequencies.)

Question 14

What are the two important aspects of TCP/IP for vendors and manufacturers

Answer 14

Open Standard Protocol suite- Freely available to the public

Standards based Protocol suite- Has been endorsed by the networking industry and approved by a standards organization

Question 15

What are the advantages of the use of open standards?

Answer 15

Open standards encourage interoperability, competition, and innovation. They also guarantee that the product of no single company can monopolize the market or have an unfair advantage over its competition.

Question 16

Describe the 7 layers of the OSI Model

Answer 16

7 - Application- The application layer contains protocols used for process-to-process communications.
6 - Presentation- The presentation layer provides for common representation of the data transferred between application layer services.
5 - Session - The session layer provides services to the presentation layer to organize its dialogue and to manage data exchange.
4 - Transport-The transport layer defines services to segment, transfer, and reassemble the data for individual communications between the end devices.
3 - Network- The network layer provides services to exchange the individual pieces of data over the network between identified end devices.
2 - Data Link- The data link layer protocols describe methods for exchanging data frames between devices over a common media
1 - Physical- The physical layer protocols describe the 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 17

Describe the 4 layers of the TCP/IP Model

Answer 17

4 - Application- Represents data to the user, plus encoding and dialog control.
3 - Transport -Supports communication between various devices across diverse networks.
2 - Internet- Determines the best path through the network.
1 - Network Access- Controls the hardware devices and media that make up the network.

Question 18

What are the similarities between the OSI and TCP/IP models?

Answer 18

*See word for pic

Question 19

What are the benefits of segmenting messages?

Answer 19

Increases speed - Because a large data stream is segmented into packets, large amounts of data can be sent over the network without tying up a communications link. This allows many different conversations to be interleaved on the network called multiplexing.
Increases efficiency -If a single segment is fails to reach its destination due to a failure in the network or network congestion, only that segment needs to be retransmitted instead of resending the entire data stream.

Question 20

Describe sequencing

Answer 20

Multiple pieces of a message are labeled by the TCP for easy direction and reassembly

Question 21

What are the general terms for PDUs at different layers?

Answer 21

Application- Data
Transport- Segment
Network- Packet
Data link layer- Frame
Physical layer- Bits

Question 22

What are the different purposes for the addresses in the network and data link layer?

Answer 22

Network layer source and destination addresses - Responsible for delivering the IP packet from the original source to the final destination, which may be on the same network or a remote network.

Data link layer source and destination addresses - Responsible for delivering the data link frame from one network interface card (NIC) to another NIC on the same network.

Question 23

What are the 2 IP addresses found in the IP packet?

Answer 23

Source IP address - The IP address of the sending device, which is the original source of the packet.
Destination IP address - The IP address of the receiving device, which is the final destination of the packet.

Question 24

What are the two parts of an IP address?

Answer 24

Network portion (IPv4) or Prefix (IPv6) - The left-most part of the address that indicates the network in which the IP address is a member. All devices on the same network will have the same network portion of the address.

Host portion (IPv4) or Interface ID (IPv6) - The remaining part of the address that identifies a specific device on the network. This portion is unique for each device or interface on the network.

Question 25

What are the two MAC addresses physically embedded on the Ethernet NIC.

Answer 25

• Source MAC address - This is the data link address, or the Ethernet MAC address, of the device that sends the data link frame with the encapsulated IP packet.
• Destination MAC address - When the receiving device is on the same network as the sending device, this is the data link address of the receiving device.

Question 26

Why are protocols necessary in communication?

Answer 26

Network protocols are needed because it include mechanisms for devices to identify and make connections with each other, as well as formatting rules that specify how data is packaged into messages sent and received.

Question 27

What is the purpose of adhering to a protocol suite?

Answer 27

Protocol suites are comprised of different protocols that work together to provide a comprehensive network or communication. By maintaining a consistent protocol suite between various sites and devices ensures connectivity can be established. This allows equipment made by different manufacturers to communicate with any other device.

Question 28

How are the TCP/IP model and OSI model used to facilitate standardization in the communication process?

Answer 28

Associating the protocols that set the rules of data communications with the different layers of these models is useful in determining which devices and services are applied at specific points as data passes across LANs and WANs. Data that passes down the stack of the OSI model is segmented into pieces and encapsulated with addresses and other labels. The process is reversed as the pieces are de-encapsulated and passed up the destination protocol stack. The OSI model describes the processes of encoding, formatting, segmenting, and encapsulating data for transmission over the network.

Question 29

Why did RFCs become the process for establishing standards? What is the RFC process?

Answer 29

Request for Comments (RFC) is a formal document from the IETF created through multiple drafting and reviews by a committee. If RFCs submitted to become Internet standards are finalized, no further changes or reviews are allowed. Any changes to an RFC Internet standard can only be made through subsequent RFCs which supersede any previous standards. RFCs are necessary to eliminate standards duplication and allow collaboration and review from multiple parties and views.

Question 30

How does data encapsulation allow data to be transported across the network?

Answer 30

Data encapsulation communicates messages by dividing the data into smaller, more manageable pieces to send over the network. This division of the data stream into smaller pieces is called segmentation. Segmenting messages has two primary benefits Segmentation and Multiplexing

Question 31

How do local hosts access remote resources on a network?

Answer 31

To access remote resources on a network, a VPN (Virtual Private Network) can be created. VPNs provide data protection online similar to a firewall so even if information is intercepted the encryption used would make stolen data useless.