What are the  application layer protocols used for?

Protocols are used to exchange data between programs running on the source and destination host.

What are the 3 primary functions of the Presentation Layer?

(C C E)

• Coding
• Compression
• Encryption

1).   Coding and Conversion of Application layer data to ensure that data from the source device can be interpreted by the appropriate application on destination device.

2).   Compression of the data in a manner that can be decompressed by the destination device

3).   Encryption of the data for transmission and the decryption of data upon receipt by the destination.

What does the application layer provide?

1.  Provides the intereface between the application we use to communicate.

                        and

2. The underlying network over which your messages are transmitted.

What is the main function of the session

layer?

                (CHR)

1).  Creates and maintain dialogs between source and destination applications.

2).   Handle the exchange of information to initiate dialog, keep them active.

3).   Restart sessions that are disrupted or idle

What do the Application layer protocols of the TCP/IP protocol specify?

The format and control information necessary for many of the common internet communication.

What are the two forms of software programs of process that provide network access in the Application Layer?

1).  Application

2).  Services

- Network-Aware Application = application are the software programs used by people to communicate over the network.

- Application Layer Services = Uses protocols which defines the standards and data to format and redirect data.

           What do protocols provide?

Protocols provide the rules and formats that govern how data is treated.

 All three components may be used by a single executable program and may even use the same name.

For example, when discussing "Telnet" we could be referring to the application, the service, or the protocol.

What is the difference between an application and a service?

Applications are the software program used by people to communicate over the network.

Services are programs that interface with the network and prepare the data for transfer.

What do application layer protocols do?

The application layer protocols define the standards and data formats to be used.

What are the 6 things protocols do?

(PTSMHI)

1).   Define processes on either end of the communications

2).  Define the types of messages

3).  Define the syntax of messages

4).  Define the meaning of any informational field

5).  Define how messages are send and expected a response.

6).  Define interaction with the next lower layer.

What is the difference between a client and a server?

Client is the device requesting the information .

Server is the device responding to the request.

In general networking sense what is a server?

A server is any device that responds to requests from client applications is functioning as a server.

A server is usually a computer that contains information to be shared with many client systems.

Describe the 2 processes a daemon uses (listening and hears)?

Listening = for a request from a client, because they are programmed to respond whenever the server receives a request for the service provided by daemon.

Hears= a request from a client, it exhange appropriate messages with the client, as requested by its protocol and proceeds to send the requested data to the client in the proper format.

What is a peer-to-peer network?

Two or more computers are connected via a network.

                           and

Can share resources (Printer, Files) without having a dedicated server.

     Are peer-to-peer networks easy to secure?

Peer-to-Peer, is not easy to secure because peer-to-peer usually do not use centralized user accounts, permission, or monitors, it is difficult to enforce security and access policies in networks containing more than just a few computers.

What do port numbers identifies?

Port numbers identifies application layer protocols and services.

             What do the DNS protocol do?

DNS Protocol communications use a single format called a message.

                                  and

DNS defines a automatic service that matches resource names with the numeric network address.

   What does the nslookup utility allow you to do?

                   (MTV)

nslookup utility allows you to:

1).  Allows the user to manually query the name servers to resolve a given host name.

2).  used to troubleshoot name resolution issue.

3).  Verify the current status of the name server.

What does the command ipconfig/display DNS show?

The command ipconfig displays all the cached DNS entries on windows XP or 2000 computer system.

What happens if a DNS server does not have a name in its stored records?

DNS contacts other servers in order to resolve the name.

If the same request is made again where does the DNS server look?

The first server can return the address by using the value stored in its name cache.

When is a server declared to be an authoritative server?

If given server has resource records that corresponds to its level in the domain hierarchy.

Define the three parts of a url as listed on the page?

1).  http= (The protocol or scheme)

2).  www.cisco.com = (The server name)

3).  Web-server.htm ( The specific filename requested)

What type of request is sent to the server when retreiving a web page?

Browser will ask for the file web-server.htm

              What does the POST command do?

The POST command send messages that upload data to the web server. 

Post messages upload information to the server in plain text that can be accepted and read

         What does the the PUT command do?

PUT uploads resources on content to the web server.

What protocol is used for secure transmission across the web?

https protocol is used for accessing or posting web server.

What 2 Application layer protocols are used in sending and receiving email?

Simple  Mail Transfer Protocol (SMTP)

Post Office Protocol (POP)

What is another name for an email application?

Mail User Agent  (MUA)

Retrieves mail using POP

Client used to access and read mail

What are the two processess that email servers perform MTA and MDA?

1.  Mail Transfer Agent (MTA) = Process is used to forward email between servers using SMTP.

Recieves mail from client

2.  Mail Delivery Agent (MDA) = Mail is addressed to a user whose mail box is on the local server is passed to the MDA.

Resolves final delivery issues

Perform actual delivery to user mail box

What happens to emails in many companies once the email reaches the internal server?

Emails clients typically communicate with the email server using a proprietary protocol.

List and describe some of the commands used by the SMTP protocol.

              (HEMMD)

1. HELO = identifies the SMTP client process to the SMTP server process.

2. EHLO = is a newer version of HELO, which includes services.

3. Mail From= identifies the sender

4. Mail To = identifies the receipient

5. Data = identifies the body of the message

         What is File Transfer Protocol (FTP)?

- Used at the application layer

- Was developed to all file transfer between client and server. 

What are the 2 ports used and their purpose in FTP?

Port 20 & 21

Port 20 = Connection is for actual file transfer and is created everytime there is a file transfer.

Port 21 = Is used for control traffic, consistings of client commands and server replies.

What does Dynamic Host Confirmation Protocol (DHCP) do for a network?

DHCP service enables clients on the network to obtain IP addresses and other information from a DHCP Server.

Allows a host to obtain an IP address dynamically when it connects to the network.

What are the 4 types of messages sent and received in DHCP?

                      (DORA)

1).  DHCP Discover

2).  DHCP Offer

3).  DHCP Request

4).  DHCP Acknowledge

     What is SMB (Server Message Block)?

- Is client/server file sharing protocol.

- It is a request-response protocol

- Servers can make their resources available to clients on the network.

What are the 3 messages types of SMB(Server Message Block) messages?

1).  Start authenticate and terminate protocol

2).  Control file and printer access

3).  Allow an application to send or receive messages to or from another device

What does the Telnet application provide?

A standard method of emulating text-based terminal devices over the data network.

What protocol is recommended alternative to Telnet when security is a concern?

1).  Secure Shell (SSH) protocol offers an alternative and secure method for server access.

2).  Must always use (SSH) instead of VOIP.