NETWORK PROTOCOLS

 

NETWORK PROTOCOLS

Network protocols are the rules and conventions for communication between network devices. It include the guidelines that regulate the characteristics of network such as access method, types of cabling, speed of data transfer and physical topologies.

Protocols for computer networking all generally use packet switching techniques to send and receive messages in the form of packets.

Network protocols is the 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.

Network protocols contain the set of higher level protocols and low level protocols.

Higher level protocols in the IP family interact more closely with applications like Web browsers

For higher level protocols it include

User defined protocols (UDP)

Hypertext Transfer Protocol HTTP

Transmission control protocols (TCP)

File transfer protocols FTP

Simple Mail Transfer Protocol (SMTP)

Lower level protocols interact with network adapters and other computer hardware.

TRANSMISSION CONTROL PROTOCOL/INTERNET PROTOCOL (TCP/IP)

Transmission Control Protocol it provides a communication service at an intermediate level between an application program and the Internet Protocol.

TCP/IP uses the client/server model of communication in which a computer user (a client) requests and is provided a service (such as sending a Web page) by another computer (a server) in the network.

TCP/IP it composed of four layers

1)   Network Access layer this provides an interface with the physical network and error control for data delivered on the physical network.

It also formats the data for the transmission medium and addresses data for the subnet based on physical hardware addresses

2)   Internet layer this provides logical, hardware-independent addressing so that data can pass among subnets with different physical architectures.

Provides routing to reduce traffic and support delivery across the internetwork.

3)   Transport layer this provides flow-control, error-control, and acknowledgment services for the internetwork. Serves as an interface for network applications.

4)   Application layer this provides applications for network troubleshooting, file transfer, remote control, and Internet activities.  Also supports the network application programming interfaces (APIs) that enable programs written for a particular operating environment to access the network.

How TCP/IP works

 TCP/IP protocol system work together to send and receive data across the network.

This will include the following activities

It describe the layers of the TCP/IP protocol system and the purpose of each layer and explain how the OSI layers relate to TCP/IP

Explain TCP/IP protocol headers and how data is enclosed with header information at each layer of the protocol stack

Name the data package at each layer of the TCP/IP stack and discuss the TCP, UDP, and IP protocols and how they work together to provide TCP/IP functionality

FUNCTIONS OF TCP/IP

• Dividing messages into manageable chunks of data that will pass efficiently through the transmission medium.
• Interfacing with the network adapter hardware.
• Addressing: The sending computer must be capable of targeting data to a receiving computer. The receiving computer must be capable of recognizing a message that it is supposed to receive.
• Routing data to the subnet of the destination computer, even if the source subnet and the destination subnet are dissimilar physical networks.
• Performing error control, flow control, and acknowledgment: For reliable communication, the sending and receiving computers must be able to identify and correct faulty transmissions and control the flow of data.
• Accepting data from an application and passing it to the network.
• Receiving data from the network and passing it to an application.

UDP-User Datagram Protocol

User datagram protocol is a communications protocol that offers a limited amount of service when messages are exchanged between computers in a network that uses the Internet Protocol (IP)

UDP provides two services port numberss and checksum

Port number to help distinguish different user requests and optionally,

Checksum is a capability to verify that the data arrived intact

Transmission Control Protocol, UDP uses the Internet Protocol to actually get a data unit called a datagram from one computer to another.

UDP does not provide the service of dividing a message into packets (datagrams) and reassembling it at the other end. Specifically

 UDP doesn't provide sequencing of the packets that the data arrives in such as an application program that uses UDP must be able to make sure that the entire message has arrived and is in the right order.

UDP provides a minimal, unreliable, best-effort, message-passing transport to applications and upper-layer protocols.

The UDP header consists of four fields each of 2 bytes in length:

1)   Source Port (UDP) packets from a client use this as a service access point to indicate the session on the local client that originated the packet.

2)   Destination Port (UDP) packets from a client use this as a service access point (SAP) to indicate the service required from the remote server.

3)   UDP length (The number of bytes comprising the combined UDP header information and payload data)

UDP Checksum is verifying that the end to end data has not been corrupted by routers or bridges in the network or by the processing in an end system.

Hyper Text Transfer Protocol HTTP

Hypertext transfer protocol is the protocol that is responsible for transfer of text in a client server. The function of HTTP is a request response in client server computing in a web browser.
It can run an application on a computer hosting a web site
Mechanism that HTTP perform
The client submits an HTTP request message to the server. The server provides resources such as HTML files and other content or performs other functions on behalf of the client, returns a response message to the client. The response contains completion status information about the request and may also contain requested content in its message body.

HTTP Status Codes

Errors on the Internet can be quite frustrating — especially if you do not know the difference between a 404 error and a 502 error. These error messages, also called HTTP status codes are response codes given by Web servers and help identify the cause of the problem.
For example, "404 File Not Found" is a common HTTP status code. It means the Web server cannot find the file you requested. The file -- the webpage or other document you try to load in your Web browser --  has either been moved or deleted, or you entered the wrong URL or document name.

GET

Requests using GET should only retrieve data from server

HEAD

This is useful for retrieving meta-information written in response headers, without having to transport the entire content.

POST

Requests that the server accept the entity enclosed in the request as a new subordinate of the web resource identified by the URI

PUT

Requests that put the information into URI

DELETE

Deletes the specified resource.

TRACE

Echoes back the received request so that a client can see what (if any) changes or additions have been made by intermediate servers.

OPTIONS

This can be used to check the functionality of a web server by requesting '*' instead of a specific resource.

CONNECT

Converts the request connection to a transparent TCP/IP tunnel, usually to facilitate SSL-encrypted communication (HTTPS) through an unencrypted HTTP proxy

PATCH

Applies partial modifications to resources.

                             FILE TRANSFER PROTOCOL (FTP)
File transfer protocol is the protocol that are used for exchanging files over the Internet
FTP is most commonly used to download a file from a server using the Internet or to upload a file to a server (e.g., uploading a Web page file to a server).

Data transfer can be done in any of three modes

• Stream mode: Data is sent as a continuous stream, relieving FTP from doing any processing.
• Block mode: FTP breaks the data into several blocks (block header, byte count, and data field) and then passes it on to TCP.^]
• Compressed mode: Data is compressed using a single algorithm run-length encoding 

How to Upload File in FTP

1.   Open the FTP website in your browser.

2.   Click Page, and then click Open FTP site in Windows Explorer.

 If you use a different web browser, follow the instructions that came with your browser.  If you are prompted for an administrator password or confirmation, type the password or provide confirmation.

3.   In Windows Explorer, press ALT, click File, and then click Login as.

4.   Type the user name and password, and then click Log On.

After you sign in, you can copy files to the FTP website by copying and pasting.