TFTP
TFTP represents the Trivial File Transfer Protocol. Some applications do not need the full functionality of TCP, nor can they afford the complexity. TFTP supports an inexpensive structure that does not require complex interactions between the client and the server. TFTP confine operations to simple File Transfer and does not support authentications.
The benefit of using TFTP is that it enables bootstrapping code to use the similar underlying TCP/IP protocols that the operating framework uses once it starts execution. Thus it is the possibility for a device to bootstrap from a server on another physical network.
TFTP does not have a dependable stream transport service. It runs on the top of UDP of any other unreliable packet delivery system using timeout and retransmission to ensure that data arrives. The sending side transmits a file in fixed-size blocks and awaits each block's acknowledgement before sending the text.
Features of TFTP
The main features of TFTP are as follows−
TFTP is based on the client-server principle and uses well-known UDP port number 69 for the TFTP server.
TFTP is an unsecured protocol and does not support authentication.
TFTP incorporates an idle − RQ (stop and wait) error recovery mechanism.
Every TFTP data unit bears a sequence number.
Each data unit is separately acknowledged. After taking the acknowledgement, the next data unit is transmitted.
Error recovery is by retransmission after timeout. TFTP uses an adaptive timeout with an exponential back-off algorithm.
TFTP Message Formats
There are four types of TFTP Messages which are as follows −
Read Request −The client uses this command to get 0 copies of a file from the server
Read Request (1) | File Name | 0 | mode | 0 |
2 octets variable 1 octet variable 1 octet
Write Request − The client uses this command to write a file into the server
Read Request (1) | File Name | 0 | mode | 0 |
2 octets variable 1 octet variable 1 octet
Data − This TFTP message contains blocks of data.
Data (3) | Sequence Number | Data |
2 octets 2 octets up to 512 octets
Acknowledgement− The client and the server used this to acknowledge the received data units.
Ack (4) | Sequence Number |
2 octets 2 octets
In this figure, the first two octets indicate the type of message. Mode fields define the type of data (ASCII or Binary). The file name and mode fields are delimited using an all zero's octet.
Type 3 message contains the data blocks of the fixed size of 512 octets. The session is removed if a data message appears with a data octet less than 512 octets. The last data message can have a data block (with EOF) with less than 512 octets. Type 4 message is used for acknowledgement.
FTP
FTP definition
File Transfer Protocol (FTP) is a widely used network protocol for transferring files between computers over a TCP/IP-based network, such as the internet. FTP lets people and applications exchange and share data within their offices and across the Internet. FTP was one of the first technologies developed to solve this common need, and it remains—with several generations of enhancements—the second most popular protocol used today (after HTTP, or the "World Wide Web").
Applications of FTP
FTP finds application in many day-to-day business operations spanning business-to-business and peer-to-peer data transfer use cases:
Organizations use FTP to allow employees to share files across different locations and branch offices
Employees use FTP to securely share files with coworkers and external business partners
IT teams use FTP to transfer data back to disaster recovery (DR) sites
Webmaster teams use FTP to transfer webpages, web application files, and images to their webserver
How to file transfer happens with FTP
File Transfer Protocol works in a client-server model where an FTP server and FTP client perform the file transfer operation. An FTP server is configured in the network, and a specific file storage location (folder/system) is identified to become the shared storage, which will host the files you want to share. The end-users will access this file server via FTP to start copying the files to their local folder/system.
FTP requires a TCP/IP network to function, and it relies on the use of one or more FTP clients. The FTP client acts as the communication agent to interact with the server and download or upload files. In other words, the FTP client sends out connections to the FTP server. Upon listening to the request from the client to either upload or download a file, the FTP server performs the file transfer operation.
What are FTP clients used for?
FTP clients were just command-line interface (CLI) applications a few decades ago. They now come in easy-to-use, intuitive interfaces to facilitate and simplify file transfers. FTP clients are used for desktops, servers, and mobile devices, and they’re available as stand-alone apps, web clients, and simple extensions to web browsers. FTP Voyager® is a free Windows FTP client from SolarWinds® Serv-U® designed to provide a host of built-in functions to simplify file transfer.
Active vs. passive FTP server connections
The FTP server can support both active and passive connections with the FTP client. In an active FTP connection, the client opens a port and listens while the server actively connects to it. In a passive connection, the server opens a port and listens passively, which allows clients to connect to it.
Passive connections are more secure, and IT admins prefer them because data connections are made from the FTP client to the FTP server. This is a more reliable method, and it avoids inbound connections from the internet back into individual clients. In firewalled deployments, all connections are made from the internet to the server, not from the server back to the internet. Passive mode is also known as "firewall-friendly" mode. The more secure file transfer protocols (such as SFTP, FTPS) the FTP client supports, the more secure it becomes.
DHCP
Dynamic Host Configuration Protocol (DHCP) is a network management protocol for dynamic and centralized IP address allocation and management.
DHCP was first defined in October 1993 based on BOOTP. As defined in RFC 2131, DHCP operates based on the client-server model. A DHCP client applies to a DHCP server for network parameters, such as the IP address, subnet mask, default gateway address, and DNS server address. The DHCP server then replies with the configuration parameters to the client so the client can communicate with other IP networks.
Why Do We Need DHCP?
On an IP network, each device connected to the Internet must be assigned a unique IP address. DHCP helps network administrators to monitor and assign IP addresses in a centralized manner. It can automatically assign a new IP address to a computer when it is moved to another location. DHCP automates the process of allocating IP addresses, which reduces the time required for device configuration and deployment, as well as the possibility of configuration errors. In addition, a DHCP server can manage the configurations of multiple network segments. When the configuration of a network segment changes, an administrator only needs to update the corresponding configuration on the DHCP server.
DHCP offers the following advantages:
Reliable IP address configuration: The IP address configuration parameters must be exact. It is easy to make a mistake when dealing with inputs such as 192.168.XXX.XXX. Typographical errors are typically very difficult to troubleshoot and the use of a DHCP server minimizes such errors.
Reduced IP address conflicts: Each connected device must have an IP address. However, each IP address can be used only once. If an IP address conflict occurs between two devices, one or both of the devices cannot be connected. This can happen when IP addresses are allocated manually, particularly when there are a large number of endpoints that only connect periodically, such as mobile devices. The use of DHCP ensures that each IP address is used only once.
Automatic IP address management: In any network without DHCP, network administrators need to manually assign and withdraw IP addresses. Keeping track of which device has what IP address can be an exercise in futility as it is nearly impossible to understand when devices require access to the network and when they leave. DHCP allows this to be automated and centralized so network professionals can manage all locations from a single location.
Efficient change management: The use of DHCP makes it very simple to change addresses, scopes, or endpoints. For example, an organization may want to change its IP addressing scheme from one range to another. The DHCP server is configured with the new information and the information will be propagated to the new endpoints. Similarly, if a network device is upgraded and replaced, no network configuration is required. You can refer to what is DHCP.
HTTP
An application-layer protocol is used for communications between web servers and browsers or other programs. HTTP adopts the request-response model. A client sends a request to the server. The request consists of two parts: request header and MIME-like message. The request header contains the request method, uniform resource locator (URL), and protocol version. The MIME-like message contains request modifiers, client information, and possible body content. Upon receiving the request, the server responds with a status line. The status line includes the message's protocol version, success or error code, and a MIME-like message, which contains server information, entity meta-information, and possible entity-body content. For details about HTTP, see RFC2616. The protocol is used to carry requests from a browser to a Web server and to transport pages from Web servers back to the requesting browser. Although HTTP is almost universally used on the Web, it is not an especially secure protocol. Hypertext Transfer Protocol (HTTP) - a networking protocol for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web.
How HTTP works
Through the HTTP protocol, resources are exchanged between client devices and servers over the internet. Client devices send requests to servers for the resources needed to load a web page; the servers send responses back to the client to fulfill the requests. Requests and responses share sub-documents -- such as data on images, text, text layouts, etc. -- which are pieced together by a client web browser to display the full web page file.
In addition to the web page files it can serve, a web server contains an HTTP daemon, a program that waits for HTTP requests and handles them when they arrive. A web browser is an HTTP client that sends requests to servers. When the browser user enters file requests by either "opening" a web file by typing in a URL or clicking on a hypertext link, the browser builds an HTTP request and sends it to the Internet Protocol address (IP address) indicated by the URL. The HTTP daemon in the destination server receives the request and sends back the requested file or files associated with the request.
To expand on this example, a user wants to visit TechTarget.com. The user types in the web address and the computer sends a "GET" request to a server that hosts that address. That GET request is sent using HTTP and tells the TechTarget server that the user is looking for the HTML (Hypertext Markup Language) code used to structure and give the login page its look and feel. The text of that login page is included in the HTML response, but other parts of the page -- particularly its images and videos -- are requested by separate HTTP requests and responses. The more requests that are made -- for example, to call a page that has numerous images -- the longer it will take the server to respond to those requests and for the user's system to load the page.
When these request/response pairs are being sent, they use TCP/IP to reduce and transport information in small packets of binary sequences of ones and zeros. These packets are physically sent through electric wires, fiber optic cables, and wireless networks.
The requests and responses that servers and clients use to share data with each other consist of ASCII code. Requests state what information the client is seeking from the server; responses contain code that the client browser will translate into a web page.
