Quiz 3 IT 105 CHAP 13

Question 1

What are parts of the communication model and what does it consist of?

Answer 1

Implemented as a hierarchical protocol stack

Each layer of the stack at the sender node contributes information that is used by the corresponding peer layer at the receiver node

Different protocols for the different aspects of communication

Separating tasks and including well defined interfaces between the tasks

Question 2

What are the 4 qualities the communication model has?

Answer 2

Adds flexibility

Simplifies design of protocols

Permits modification or substitution of protocols without affecting unrelated tasks

Permits a system to select only the protocols needed for a particular application

Question 3

What is TCP/IP? What is it based on? What does it encompass?

Answer 3

Transmission Control Protocol/Internet Protocol

Based on five protocol layers, although layers 1 and 2 are not actually specified in the standard. However, the TCP/IP model recognizes the existence of these layers as a necessity.

The TCP/IP protocol suite encompasses an integrated suite of numerous protocols that work together and guide all aspects of communication

Question 4

How many layers does the TCP/IP have?

Answer 4

5

Question 5

What is layer 1 called and what are it’s components?

Answer 5

Physical layer

Layer at which communication actually takes place consisting of a bare stream of bits

Primarily implemented in hardware by a network interface controller (NIC)

Physical access protocol includes
-Definition of the medium
-Signaling method, signal parameters, carrier -frequencies, lengths of pulses, synchronization and timing issues
-Method used to physically connect the computer to the medium

Question 6

What is layer 2’s first section called and what are it’s components?

Answer 6

Data Link Layer

Responsible for the reliable transmission and delivery of packets between two adjacent nodes

Packets at this layer are called frames

Often divided into two sublayers:

Software logical link control (LLC) sublayer
Hardware medium-access control (MAC) sublayer

Question 7

What are layer 2’s subsections called and what are its components ?

Answer 7

Software logical link control (LLC) sublayer
Error correction, flow control, retransmission, packet reconstruction and IP datagram/frame conversions

Numbers frames and reorders received frames to recreate the original message

Rarely used

Hardware medium-access control (MAC) sublayer
Defines procedures for accessing the channel and detecting errors

Responsible for services such as data encoding, collision handling, synchronization, and multiplexing

Question 8

What is an example of a data link layer implementation?

Answer 8

Layer 2

Question 9

What is the concept of switched ethernet?

Answer 9

The Ethernet switch keeps a table of which MAC addresses are accessible through each of its ports

Permits point-to-point connection of any pair of nodes

Multiple pairs can be connected simultaneously

Possible to connect nodes in full-duplex mode

Each pair of connections operates at the maximum bit rate of the network

Question 10

What is wireless ethernet: WIFI?

Answer 10

Infrastructure mode:
Based on shared access point

CSMA/CA – collision avoidance MAC protocol

Station waits until channel is clear plus a short random amount of time before transmitting

May use ‘request to send’ and ‘clear to send’ options to improve collision avoidance

Ad hoc mode:
Assumes direct connections between nodes

Based on partial mesh network topology

Rarely used

Question 11

What is layer 3 called and what are its components?
What does the IP protocol consist of?

Answer 11

Network Layer
Also called the internetworking layer or IP layer

IP protocol:

Responsible for routing packets from the source end node to the destination end node through intermediate nodes

Performed using datagram packet switching and logical IP addresses

Unreliable, best-effort delivery service

Size of datagram ranges from 20 to 65,536 bytes

Header size between 20 and 60 bytes

Question 12

What does layer 3’s network layer transmission consist of?

Answer 12

Communications within a local network:
No routing is required because nodes are directly addressable

Physical addresses for corresponding IP addresses are looked up in a table

IP appends a header with the physical address and passes the datagram to layer 2, the data link layer

Communications sent outside of the local network:

At each intermediate node, the network layer removes the current node address and determines the next node address

The new address is added to the packet and passed to layer 2, the data link layer

Question 13

What does the operation of IP consist of and what are the two major functions? What is the ARP?

Answer 13

Two major functions

Routes datagrams from node to node until they reach their destination node

Translates IP addresses to physical addresses before it passes the packets to the data link later for delivery

Address Resolution Protocol (ARP):
Implemented at the network layer

Translation of IP address to physical address at each intermediate node until destination is reached

A broadcast of the IP address is sent to every node on the network. The matching node responds with a physical address

Physical address (MAC address in the case of Ethernet) is sent in frame to the data link layer

At final destination, the packet is passed up to the transport layer for deployment to the application layer

Question 14

What is ICMP and what are it’s 4 qualities?

Answer 14

Internet Control Message Protocol

Auxiliary protocol that creates error messages for failures at the network layer

Error code is encapsulated in an IP datagram and sent to source

Typical messages: ‘Destination Host Unknown’, ‘Time to Live Exceeded’

Used for queries by network tools such as ping and traceroute

Question 15

What is layer 4 called and what are its components?
What is packetization?

Answer 15

Transport layer
Provides services that support reliable end-to-end communications

Generates the final address of the destination

Responsible for all end-to-end communication facilities

Establishes connection with the destination, provides flow control, data assurance, reordering of packets, error recovery, and connection termination

Packetization:
Breaking up of the message into packets of reasonable size, takes place at this level

Question 16

How doTCP/IP addressing and port addresses work?

Answer 16

Transport layer uses to identify the application that is to receive the message

16 bits in length

Example: Port 80 is commonly used for Web services

First 1024 numbers are called well-known ports because they are standard addresses specified for most common applications

User defined port numbers are also available to applications

For example, the following Web service uses the user-defined port of 8080:

Review well known port numbers slide 21

Question 17

What are TCP/IP addresses sockets defined by?

Answer 17

Defined by a combination of the IP address and port number

Identify which computer (IP address) and which application on that computer (port number)

Provide an interface between the application layer and the transport layer to initiate connections and send messages through the network

Allow for multiple simultaneous open connections

Originated with BSD UNIX

Question 18

What are the three different transport layer protocols and what do they stand for ?

Answer 18

TCP (Transmission Control Protocol)

UDP (User Datagram Protocol)

SCTP (Stream Control Transmission Protocol)

Question 19

What is TCP?

Answer 19

TCP (Transmission Control Protocol)

Connection-oriented, reliable delivery service

Control packets are used to create a full duplex logical connection through handshaking

Numbering of packets allows packets to be reassembled in order

Question 20

What is UDP?

Answer 20

UDP (User Datagram Protocol)

Unreliable, connectionless service

No acknowledgment of receipt by receiving node

Example: streaming video

Question 21

What is SCTP?

Answer 21

SCTP (Stream Control Transmission Protocol)

Similar to TCP but with improved fault tolerance and ability to transport multiple messages through the same connection

Question 22

What are the components of IPv4 addresses ? What are the 3 levels they are divided into? What are the masks?

Answer 22

Registered and allocated by ICANN

32 bits long divided into 4 octets

Assigned in blocks of contiguous addresses

-Number of addresses is a power of two
-Example: 208.80.152.2 (Wikipedia’s IP address)

Divided into three levels:
Network address
Subnetworks (subnets)
Hosts (nodes

Masks
Used to separate the different parts of the address

Question 23

What are two addresses to distribute IP addresses more efficiently?

Answer 23

Network Address Translation (NAT)

Dynamic Host Configuration Protocol (DHCP)

Question 24

What is NAT?

Answer 24

Network Address Translation (NAT)

Use of private network IP addresses behind a router

The router must readdress traffic passing between the Internet and the local network

Difficult with large networks

Question 25

What is DHCP?

Answer 25

Maintain a bank of available IP addresses and assign them dynamically to computers for use when the computers are attached to the network

Method often used by large organizations, DSL, and cable providers

DHCP client on computer or network device broadcasts a query to locate the DHCP server

DHCP server responds with a lease that includes an IP address, domain name of network, IP address of DNS server, subnet mask, IP address of gateway, and other configuration parameters

Question 26

What is IPv6?

Answer 26

Intended to eventually replace IPv4 to provide additional IP addresses

128-bit addresses arranged as eight groups of four-digit hexadecimal numbers separated by colons

Leading zeroes and zero values in one or more consecutive groups may be eliminated

Example: 2CAA:30::370:0:12AB is the same as
2CAA:0030:0000:0000:0000:0370:0000:12AB

Question 27

What are components of domain names and DNS services?

Answer 27

Domain Names:
Hierarchical system of network address identifiers used throughout the Internet and on local area networks, intranets and extranets

Created so users would not have to memorize IP addresses

Domain Name System (DNS):
Domain name resolution – translates domain names into IP addresses

Uses a massive distributed database containing a directory system of servers

Each entry contains a domain name and an associated IP address

Question 28

What are the two parts in Quality of Service? QoS

what is jitter?

Answer 28

1. Methods to reserve and prioritize channel capacity to favor packets that require special treatment

2.Service guarantees from contract carrier services that specify particular levels of throughput, delay and jitter

Jitter – variation in delay from packet to packet

Question 29

What is Differentiated service (DiffServ)?

Answer 29

8-bit (DS) field in IP header

Set by the application at the sender or by the first node

DiffServ capable nodes such as routers can then prioritize and route packets based on the packet class

Question 30

What are the 5 network security categories?

Answer 30

Intrusion:
Keeping network and system resources free from intruders

Confidentiality:
Keeping the content of data private

Authentication:
Verifying the identity of a source of data being received

Data integrity and non-repudiation:
Protecting the content of data communication against changes and verifying the source of the message

Assuring network availability and access control:
Keep network resources operational and restricting access to those permitted to use them

Question 31

What are the three network security measures and what do they consist of?

Answer 31

Network intrusions:
Packet sniffers read data in a packet as it passes through a network

Probing attacks to uncover IP address / port numbers that accept data packets

Physical and Logical Access Restriction:
Limit access to wiring and network equipment

Firewall

Private networks

Encryption:
Symmetric key cryptography

Same key is used for encryption and decryption

Public key-private key cryptography

Two different keys are used for encryption and decryption

Question 32

What is layer 5 called and what does it consist of?

Answer 32

Session Layer :

Establishes a dialogue between two cooperating applications or processes at the ends of the communication link

Responsible for
-Establishing the session between the applications
-Controlling the dialogue
-Terminating the session

Examples
Remote login
Print spooling to remote printer

Question 33

What is layer 6 called and what does it consist of?

Answer 33

OSI presentation layer

-Responsible for presenting data at the destination with the same meaning and appearance as it would have at the source

Provides common data conversions and transformations that allow systems with different standards to communicate

Includes services such as data compression and restoration, encryption and decryption, data reformatting, ASCII-Unicode conversion, etc.

Question 34

What are the 4 components of cellular tech?

Answer 34

Long Term Evolution (4G LTE) standard is being replaced with 5G technologies

Provides standard TCP/IP protocol services at application, transport, and network layers

Requires additional protocols between data link and network layers to address handoff and movement from cell to cell

May serve as Wi-Fi access points for computing devices