Module 12: Application layer services

Question 1

describe the role of

Dynamic Host Configuration Protocol (DHCP)

Answer 1

Used to automatically configure devices with IP addressing and other necessary information to enable them to communicate over the internet.

Question 2

this Resolves internet names to IP addresses.

Answer 2

describe the role of

Domain Name System (DNS)

Question 3

Used for interactive file transfer between systems.

Answer 3

describe the role of

File Transfer Protocol (FTP)

Question 4

this is Used to provide remote access to servers and networking devices.

NOTE

typically the communication will be to the CLI of the device

Answer 4

describe the role of

Secure Shell (SSH)

Question 5

Used by web browsers to request web pages and web servers to transfers the files that make up web pages of the World Wide Web.

Answer 5

describe the role of

Hypertext Transfer Protocol (HTTP)

Question 6

1. client opens a connecion with an FTP server (source 2000, dest: 21)
2. FTP server acknowledges
3. FTP server tells the client to connect to port XXXX > 1024 for a data connection
4. the client connects to the FTP server for a data connection on the port it mentioned

Answer 6

describe in 4 steps an

File Transfer Protocol (FTP) passive connection

Question 7

operating systems come with FTP clients installed

on windows typing FTP will open the command line FTP client where commands can be issued

there are also GUI based FTP clients such as filezilla that allow an easy drag and drop feature for transferring files

Answer 7

what two ways can we issue FTP commands and transfer files using FTP

Question 8

describe the role of

Simple Mail Transfer Protocol (SMTP)

Answer 8

this Sends email messages and attachments from email clients to email servers and from email servers to other email servers.

Question 9

describe in 4 steps an

File Transfer Protocol (FTP) active connection

and its drawback

Answer 9

1. client opens a connecion with an FTP server (source 2000, dest: 21)
2. FTP server acknowledges
3. client tells the FTP server i will be listening on port XXXX for the data connection
4. FTP server opens the data connection (source: 20, dest XXXX)
   * the problem with this is since the FTP server is opening the data connection it may be blocked by a firewall since the connection was not initiated by the client

Question 10

Used to automatically configure devices with IP addressing and other necessary information to enable them to communicate over the internet.

Answer 10

describe the role of

Dynamic Host Configuration Protocol (DHCP)

Question 11

1. client opens a connecion with an FTP server (source 2000, dest: 21)
2. FTP server acknowledges
3. client tells the FTP server i will be listening on port XXXX for the data connection
4. FTP server opens the data connection (source: 20, dest XXXX)
   * the problem with this is since the FTP server is opening the data connection it may be blocked by a firewall since the connection was not initiated by the client

Answer 11

describe in 4 steps an

File Transfer Protocol (FTP) active connection

and its drawback

Question 12

this Sends email messages and attachments from email clients to email servers and from email servers to other email servers.

Answer 12

describe the role of

Simple Mail Transfer Protocol (SMTP)

Question 13

describe the role of

Domain Name System (DNS)

Answer 13

this Resolves internet names to IP addresses.

Question 14

describe the role of

Internet Message Access Protocol (IMAP)

Answer 14

Used by email clients to retrieve email and attachments from a remote email server.

NOTE

this protocol usually preserves the original email and attachments on the email server when any emails and attachments are retrieved

Question 15

describe the role of

Post Office Protocol (POP)

Answer 15

Used by email clients to retrieve email and attachments from a remote email server.

NOTE

this protocol usually deletes the original copy from the emai server when the client retreives the email and any attachments

Question 16

describe in 4 steps an

File Transfer Protocol (FTP) passive connection

Answer 16

1. client opens a connecion with an FTP server (source 2000, dest: 21)
2. FTP server acknowledges
3. FTP server tells the client to connect to port XXXX > 1024 for a data connection
4. the client connects to the FTP server for a data connection on the port it mentioned

Question 17

describe the role of

Secure Shell (SSH)

Answer 17

this is Used to provide remote access to servers and networking devices.

NOTE

typically the communication will be to the CLI of the device

Question 18

what two ways can we issue FTP commands and transfer files using FTP

Answer 18

operating systems come with FTP clients installed

on windows typing FTP will open the command line FTP client where commands can be issued

there are also GUI based FTP clients such as filezilla that allow an easy drag and drop feature for transferring files

Question 19

describe the role of

Hypertext Transfer Protocol (HTTP)

Answer 19

Used by web browsers to request web pages and web servers to transfers the files that make up web pages of the World Wide Web.

Question 20

Used by email clients to retrieve email and attachments from a remote email server.

NOTE

this protocol usually preserves the original email and attachments on the email server when any emails and attachments are retrieved

Answer 20

describe the role of

Internet Message Access Protocol (IMAP)

Question 21

Used by email clients to retrieve email and attachments from a remote email server.

NOTE

this protocol usually deletes the original copy from the emai server when the client retreives the email and any attachments

Answer 21

describe the role of

Post Office Protocol (POP)

Question 22

this is achieved using protocols such as SSH or telnet.

it allows you remote access to the CLI of a device such as a server or network device

in essence it will be as if you are directly plugged into the device and can execute any of the CLI commands

Answer 22

describe a

virtual terminal

Question 23

describe a

virtual terminal

Answer 23

this is achieved using protocols such as SSH or telnet.

it allows you remote access to the CLI of a device such as a server or network device

in essence it will be as if you are directly plugged into the device and can execute any of the CLI commands

Question 24

describe the role of

File Transfer Protocol (FTP)

Answer 24

Used for interactive file transfer between systems.