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File Transfer Protocol Explained: Everything You Need to Know

The File Transfer Protocol: Paving the Way for Networked File Sharing

Few computing advancements have had as profound an impact as the ability to easily share files between networked devices. The genesis of this capability can be traced back to a pioneering protocol established in 1971 – the File Transfer Protocol, commonly abbreviated as FTP. This article will explore the origins of FTP, how it works on a technical level, the protocol‘s evolution and historical significance, and its current status in the Internet ecosystem.

Inventing FTP: Early Networked File Transfers

Long before cloud storage and wireless networking became mainstream, early Internet pioneers were working on ways for remote computers to intercommunicate. File transfers were one of the first applications envisioned for these networks. However, the existing communication protocols at the time such as NCP (Network Control Protocol) were not suited for robust file sharing.

This gap motivated Abhay Bhushan, an MIT student and researcher on the early ARPANET project, to create a new protocol tailored to bulk data transfers. His initial FTP specification was published on 16 April 1971 as RFC 114 – one of the earliest official RFC (Request for Comments) Internet protocol standards. This seminal specification established the framework for transferring files between networked computers using a client-server architecture.

The Problem FTP Solved: Reliable Bulk Transfer

What specific problem was FTP addressing though? Early networks ran at very low speeds – ARPANET started at 50 kbps in 1969. So transmitting large datasets efficiently was an immense challenge before FTP came along.

Additionally, the connections themselves were unreliable. Lines got disconnected frequently, so that interrupted bulk transfers had to start again from scratch. FTP introduced important mechanisms like restart markers that allowed partial transfers to resume from where they left off. The built-in error checking provided reliability as well.

Overall, FTP fulfilled a vital need at the dawn of networking – it enabled users to reliably exchange files at datasets much larger than what existing ad hoc methods allowed at the time.

FTP Protocol Basics: How Clients And Servers Communicate

At its core, FTP establishes a client-server architecture for file transfers much like the web browsers and servers of today. But how exactly does the FTP client talk to an FTP server?

There are two main components for communication in FTP:

  1. Control connection: This connection, over port 21, allows the client to send commands to the server like listing directories, changing permissions etc. The server sends back responses and status codes on the control channel.

  2. Data connection: The actual file transfer occurs over the data connection between client and server. This can occur in ‘Active‘ mode where the server initiates the data connection to the client, or in ‘Passive‘ mode where the client establishes the data link to avoid firewall issues.

This separation of control flow and actual data transfer allowed FTP to manage transfers more efficiently and reliably compared to more primitive alternatives when it was introduced.

FTP in the 70s and 80s: More Capabilities and Wider Adoption

The initial FTP spec was quite bare-bones – it allowed transfers between compatible systems but had no directory handling or permissions management. As networked computing matured over the 70s, so did the capabilities of FTP.

The original author, Bhushan himself published an updated RFC 765 specification in June 1980. This introduced many crucial features for usability – server directory listings, edit and rename commands etc. But the truly canonical FTP specification came in October 1985 with RFC 959, which remains the standard even today. Authored by J. Postel and J. Reynolds, RFC 959 defined the rich functionalities that the modern FTP user would be familiar with.

By the mid-80s, FTP usage was accelerating within universities and research communities with access to ARPANET or similar networks, supplementing existing physical transfer methods. But it was still a command-line tool for expert users – no graphical interfaces existed. The advent of TCP/IP protocols led to wider adoption of FTP over the following decade as networks became more commercial.

In February 1994, RFC 1579 extended FTP to work better across firewalls by introducing passive mode transfers. This triggered widespread public adoption of FTP clients to access files on early commercial Internet servers. Users now had a handy way to download files from public FTP sites, mirroring popular websites of a later era.

The Dawn of FTP Clients and Evolution to GUI Interfaces

As FTP usage grew within organizations and enthusiasts groups in the early 90s, the first FTP client tools started emerging – ego, tnftp, FTP Explorer etc. However, they were still text-based relying on typed commands. That changed when the first graphical FTP clients arrived in the mid-90s – Fetch for Mac being an iconic early example.

Microsoft Windows 95 in 1995 was a landmark that made GUI tools ubiquitous. Suddenly, FTP morphed into easy drag-and-drop file transfers within the familiar graphical environment users were now accustomed to. Internet Explorer 1.0 integrated a basic FTP client capped FTP URL support, further easing access for novices.

By the late 90s, FTP utilization boomed with purpose-built tools like WS_FTP, CuteFTP and Filezilla offering advanced TransferManagement. The protocol had well and truly gone mainstream by this point.

The Historical Significance of FTP as an Early Internet Protocol

It‘s easy to take simple conveniences like downloading files from a webpage for granted in today‘s always-on connected world. But we owe much of that experience to the early innovators that realized the potential of inter-networking computers and built the scaffolding to make this possible. FTP was one of the first and most important such scaffolding elements.

Consider this – the modern Internet relies extensively on HTTP for accessing web resources. HTTP itself descended from FTP as a simpler, browser-friendly protocol built on the same paradigms. Many other later computing developments used concepts codified first by FTP as well:

  • Transfer reliability using checkpoint/restart
  • Access controls and user permissions
  • Automated transfers in the background
  • Documenting protocols through RFCs

Without FTP pioneering these mechanisms, our Internet experience would likely be much more limited and fragmented. FTP showed what was possible by allowing easy file access across a network, setting expectations for later protocols to enable more complex interactions between remote systems.

The Protocol Threat Model Catches Up: Securing FTP

In its original incarnation, FTP transmitted information without encryption trusting all parties in the network. But as cybercrime emerged over the 90s and 2000s, that trust was broken. FTP servers got routinely hacked to steal data in transit making it an insecure protocol.

The first major upgrade was SSH File Transfer Protocol (SFTP) which added SSH encryption between client and server for secure transfers. Building further in the 2000s, FTP-SSL (later updated to FTPS in RFC 4217) bolted SSL/TLS encryption onto the original FTP architecture providing communication security.

While FTPS and SFTP addressed wiretapping threats, they still had weaknesses like plain text passwords. Newer secure file access protocols later took security further – SCP for shell logins, WebDAV building on HTTP etc. So FTP became relegated as a legacy protocol, recommended only for harmless public data.

The Waning of FTP in The Modern Web Era

FTP may have birthed modern file transfer capabilities, but its unsecure foundations and dated architecture are showing age today. Its successor HTTP surpassed FTP‘s adoption long back powering the entire World Wide Web since the 90s.

Within browsers, native FTP support is already gone from Chrome and Edge, with Firefox planning to remove it entirely as well. On websites, FTP gave way to HTTPS downloads securing end-to-end traffic by the 2010s. Meanwhile, cloud storage services like Dropbox that sync seamlessly across devices dominate personal file access rather than old-school mounted drives.

Does this mean FTP is completely dead as some headlines portend? Not entirely – it still occupies specific but shrinking niches:

  • Hosting public download areas for open source projects, ISO images etc.
  • Some wary server admins prefer the FTP model within internal networks
  • exchanging very large datasets that are too cumbersome for web UIs

But for mainstream usage, FTP has largely been relegated as a legacy protocol at this point. As networks got faster and attack vectors multiplied, its trusting architecture proved inadequate forcing migration to more sophisticated successors.

The Outlook for FTP – A Legacy Protocol Winding Down

FTP introduced several revolutionary concepts that network computing relies on today – reliable file transfers, access controls and automated background transfers being some core examples. Our modern experience of accessing remote resources across high-speed networks traces its roots to FTP‘s innovations.

However, the threat landscape has evolved drastically since its inception. FTP‘s trusting architecture has proven increasingly vulnerable to attackers compromising privacy and security. Thus, the protocol finds itself slowly phased out from mainstream platforms and usage in favor of encrypted successors like HTTPS and SFTP.

Still, FTP hangs on where its simplicity and speed suit low-risk use cases like hosting public downloads. But even there, web apps and cloud services are taking over. As networks get faster still, FTP feels even more dated requiring user effort compared to slick modern alternatives.

While complete extinction is unlikely yet, FTP‘s glory days are clearly long gone as a historical relic in all but edge cases. We owe much to this groundbreaking protocol that pioneered file networking concepts in a pre-Internet era. But computing ultimately leaves even revolutionary technologies behind when their fundamental assumptions are invalidated by progress. FTP‘s waning illustrates well how the tech landscape constantly reinvents itself, discarding the old to make way for the new.