They say there are a thousand ways to skin a cat, although we've never tried and aren't precisely sure why someone would want to. Likewise, there many ways to transfer files around the Internet.
Once upon a time, File Transfer Protocol (FTP) was the only viable option. These days, files are moved around using a variety of technologies not specifically designed to do so e-mail, instant messaging, IRC, and even Web servers. Each of these technologies offer the advantage of familiarity with a single interface to people who use them every day for their intended purpose. But despite their convenience, each lacks a certain je ne sais quoi in terms of robustness. For example, e-mail servers often limit attachment sizes, and Web servers are cumbersome for batches and prone to corrupt large downloads.
A widening array of authentication sources further enhances security.
Amid the many file transfer options, however, the venerable FTP server continue to evolves, growing ever more robust.
By now, any FTP server worth its salt addresses an array of features designed to manage its use. This includes user authentication, file transfer policies (e.g., ratios, bandwidth throttles, and IP filters), and detailed activity logging. FTP servers continue to evolve, adding new features that address, in particular, the areas of security, virtualization, and automation.
Security has rapidly become a red-hot issue. For many years, FTP servers communicated with clients "in the clear," meaning login and password information were vulnerable to interception. Now, FTP servers, such as BulletProof FTP, SecureFTP, SurgeFTP, TitanFTP, and WS_FTP, support SSL/TLS and use the same type of encryption present on secure Web sites. With SSL/TLS, FTP servers can encrypt the control commands between FTP clients and the server, as well as the file data itself. With PGP support, such as in WS_FTP Pro, file data is further secured with public key encryption only the user who requested the file can decrypt it.
A widening array of authentication sources further enhances security. Both SurgeFTP and SecureFTP can consult external Active Directory or ODBC sources for user authentication. Several FTP servers, including SecureFTP, RaidenFTPD, and Titan FTP, support S/KEY, a one-time password system for maximum authentication security.
Virtualization support abstracts the FTP server above the local filesystem, enabling administrators to build a virtual filesystem that exists only within the FTP realm. Virtual folders, such as those supported in RaidenFTPD and CrushFTP, enable files to be grouped together regardless of their structure on the local filesystem. Consequently, the local folder structure does not need to change to meet the needs of the FTP server. Virtual permissions mean access privileges (e.g., read, write, and delete) can be provided to FTP users without changing "real" permissions on the local system. CrushFTP even supports the virtualization of other FTP servers, which means their contents can be served through CrushFTP, just like any local file.
Changes in network topography have pushed FTP servers to adapt, particularly due to the popularity of firewalls, routers, and Network Address Translation (NAT). Increasingly, machines that might host an FTP server have a private IP address protected behind a firewall.
Automation takes FTP servers beyond their roots as mere grab-and-go depositories. Event triggers in SecureFTP and CrushFTP and scriptable scheduling in WS_FTP enable FTP servers to initiate actions based on circumstance. For example, an event trigger can watch for a certain file to be uploaded and send an alert to an administrator. A scheduler can automate file delivery at regular intervals. IRC connectivity in CrushFTP and RaidenFTPD provides a control interface for interaction with chat group users, translating chat messages into FTP directives.
Taking a page from the popularity of peer-to-peer (P2P) networks, FTP servers are beginning to leverage the power of multipart file transfers. SecureFTP and WS_FTP, for example, can break a file into segments, transferring multiple segments simultaneously. This piggybacking dramatically decreases the total time needed to transfer very large files. Most modern P2P servers behave this way, and it's fair to expect more widespread adoption among the FTP crowd.
Changes in network topography have pushed FTP servers to adapt, particularly due to the popularity of firewalls, routers, and Network Address Translation (NAT). Increasingly, machines that might host an FTP server have a private IP address protected behind a firewall. In the past, working through this obstacle meant relying on specialized networking knowledge, but now FTP servers like BulletProof FTP, SurgeFTP, and WS_FTP Pro are aware of firewalls and make it easier to punch through them. Some servers, like RaidenFTPD, support the leading-edge UPnP NAT traversal technology, for "zero configuration" behind UPnP-enabled network routers.
With so many FTP server solutions available, pricing has shifted downward. Capable options are available free of charge (e.g., RaidenFTPD and War FTP), and many cluster below the $40 price point (e.g., Bulletproof FTP, CrushFTP, Titan FTP, and WS_FTP Pro). A notable exception, the $395 Secure FTP Server, features enterprise-grade multidimensional security. By and large, FTP servers are a land of plenty full-featured, continuing to evolve, and affordably priced.