Chapter 10: Application Layer

What are the 3 primary functions of the presentation layer (OSI)?

1. Formating or presenting data at the source device into a compatible form for receipt by the destination device 2. Compressing data in a way that can be decompressed by the destination device 3. Encrypting data for transmission and decrypting data upon receipt.

What are the 3 common messafe types used by HTTP for communication?

1. GET - a client requests for data 2. POST - uploads data files to the web server such as form data 3. PUT - uploads resources or content to the web server such as an image.

What are the upper 3 layers of the OSI Model, that define the functions of the single TCP/IP application layer?

Application, Presentation, Session

What is an application?

Applications are computer programs with which the user interacts and which initiate the data transfer process at the users request.

In what layer do client server processes occur? Describe this process.

Client & Sever processes are considered to be in the application layer. The client begins the exchange by requesting data from the server, which responds by sending one or more streams of data to the client. Application layer protocls describe the format of teh requests and responses between clients and servers. In addition to the actual data transfer, this exchange may also require user authentication and the identification of a data file to be transferred. *Note*: In the client-server model, the device requesting the information is called a client and the device responding to the request is called a server.

What is the function of the OSI session layer?

Creates and maintains dialogs between source and destination applications. It handles the exchange of information to initiate dialogs, keep them active, and to re-start sessions that are disrupted or idle for a long period of time.

What is the difference between HTTP & HTTPS

HTTPS uses authentication and encryption to secure data as it travels between the client and server. HTTPS uses the same client request-server response process as HTTP, but the data stream is encrypted witrh Secure Socket Layer (SSL) before being transported across the network.

Name some commonly known application layer protocols

Hypertext Transfer Protocol (HTTP), File Transfer Protocol (FTP), Trivial File Transfer Protocol (TFTP), Internet Message Access Protocol (IMAP), & Domain NAme System (DNS) protocol.

Describe the P2P networking model

In a P2P network, two or more computers are connected via a network and can share resources (such as printers and files) without having a dedicated server. Every connected end device (known as a peer) can function as both a server and a client. One computer might assume the role of server for one transaction while simultaneously serving as a client for another. The roles of client and server are set on a per request basis.

________________________ provide a structure of agreed-upon rules and processes that ensure services running on one particular device can send and receive data from a range of different network devices.

Protocols

What does SSL stand for in relation to HTTPS?

Secure Socket Layer

What is the DNS protocol?

The Domain NAme Service protocol defines an automated service that matches resource names with the required numeric network address . It includes the format for queries, responses, and data. The DNS protocol communications uses a single format called a message. This message format is used for all types of client queries and server responses, error messages, and the transfer of resources record information between servers.

What is the purpose of the application layer?

The application layer is closest to the end user. It is the layer that provides the interface between the applications used to communicate and the underlying network over which messages are transmitted. Application layer protocols are used to exchange data between programs running on source and destination hosts.

what does the *nslookup* command display?

The default DNS server configured for your host is displayed. The name of a host or domain can be entered at the *nslookup* prompt. The *nslookup* utility has many options available for extensive testing and verification of the DNS process.

What does URL stand for?

Uniform Resource Identifier

The application layer is responsible for directly accessing the underlying processes that manage and deliver communication to the _________________ network. This layer serves as the source and destination of communications across data networks. The application layer applications, services, and protocols enable users to ___________________ with the data network in a way that is meaningful and effective.

human interact