What happened to IPv1, IPv2, IPv3, and IPv5?

What Happened To IPv1, IPv2, IPv3, And IPv5?

Explore the history behind internet protocol development to understand what happened to ipv1 ipv2 ipv3 and ipv5 before modern network standards emerged.

What happened to IPv1, IPv2, IPv3, and IPv5?

When looking at networking terminology, most people notice an immediate gap in the version numbers. We jump straight from IPv4 to IPv6, skipping version five entirely, while versions one through three seem like ghosts of the history of ip address versions. But these missing numbers are not typos or lost secrets - they represent a messy, fascinating evolution of how computers learned to talk to each other.

Lets be honest: networking history sounds dry until you realize it was built through trial, error, and plenty of midnight debugging sessions. The early packet-switching experiments on ARPANET did not magically result in modern web connectivity overnight. Instead, engineers spent years breaking, rewriting, and redesigning protocols before landing on something stable.

The Experimental Era: Where Did IPv1, IPv2, and IPv3 Go?

Long before global fiber optics and cloud servers, researchers at ARPANET were trying to figure out how to pass data chunks reliably between disparate computers. Between 1973 and 1978, engineers played with different iterations of what was then a combined Transmission Control Protocol and Internet Protocol. In those primordial designs, packet routing and connection management were mashed together into a single, unwieldy bundle.

IPv1, IPv2, and IPv3 were simply step-by-step revisions of these experimental specifications, answering where are ipv1 ipv2 and ipv3 today. Each version introduced minor tweaks to headers and routing logic. For instance, IPv3 made a major conceptual leap by attempting to separate connection control from basic packet forwarding. Yet, none of these early versions ever saw commercial deployment or public release. They remained confined to research labs, used strictly for internal testing among a handful of universities and government agencies.

Why the Early Versions Never Went Public

The fundamental flaw of the first three versions was their lack of modularity. Because TCP and IP were tightly coupled, fixing a bug in error recovery often broke packet routing. Developers quickly realized that layering protocols - separating transport from network addressing - was the only way to scale the network. By 1981, this realization culminated in RFC 791, which formally introduced IPv4 and finally split the protocol stack cleanly.

That is why IPv1 through IPv3 disappeared. They were discarded drafts, left behind in research binders once a workable architecture was found. But what about the mysterious case of the missing fifth version?

The Mystery of IPv5: Did It Actually Exist?

A common misconception is that IPv5 was a failed predecessor to IPv4 that crashed and burned, which relates to why is there no ipv5 in modern routing. In reality, IPv5 as a traditional internet address protocol never existed. Instead, the number five was assigned to an entirely different networking experiment known as the Internet Stream Protocol, or ST for short.

Developed in the late 1970s and later revised in the 1990s as ST-II, this protocol was built for a radically different purpose. While IPv4 handled standard connectionless data traffic best-effort style, ST was designed to support real-time audio and video streaming with guaranteed Quality of Service. It operated at the same layer as IP and used the number 5 in the version field of its packet headers to distinguish itself from IPv4.

Why Engineers Skipped Version 5 for the Next Generation

When the networking community began designing a true successor to IPv4 in the early 1990s - a project originally called IPng (Internet Next Generation) - they faced a naming dilemma. Because the Internet Stream Protocol had already claimed version number 5 in packet headers, naming the new datagram protocol IPv5 would have caused catastrophic confusion across routing equipment.

To prevent routing mishaps and software bugs, architects decided to skip the number five entirely and name the next protocol IPv6, explaining why did the internet skip to ipv6. Even though ST never went mainstream for everyday internet users, its pioneering concepts directly influenced modern VoIP technology, video conferencing tools, and Quality of Service management.

What This Means for Modern Networking

Understanding why certain version numbers vanished reveals how resilient network architecture truly is. The jump from IPv4 straight to IPv6 is not a numbering error - it is a deliberate historical footprint. Every discarded experimental draft and specialized streaming protocol taught engineers vital lessons about address exhaustion, packet headers, and scalability.

So, while you will never configure an IPv2 address on your home router or troubleshoot an IPv5 packet drop, those ghostly versions laid the invisible groundwork for every byte of data streaming across your screen today.

Comparing Historical IP Versions and Protocols

IPv1, IPv2, and IPv3

- Confined strictly to research laboratories and university networks

- Late 1970s (ARPANET research phase)

- Experimental packet switching with combined TCP and IP functions

- Abandoned in favor of modular design; replaced by IPv4

IPv4 (The First Standard)

- Massive global deployment forming the backbone of the early internet

- 1981 to present day

- Standardized global datagram routing with 32-bit addresses

- Extremely successful, though currently facing address exhaustion

IPv5 (Internet Stream Protocol ⭐)

- Limited specialized networks (military and advanced research)

- Late 1970s through 1990s (ST and ST-II iterations)

- Real-time voice and video streaming with Quality of Service guarantees

- Never used as a general IP successor; number skipped to avoid header confusion

Network Archaeology in Chicago

Minh, a network engineer working at a technology firm in Chicago, spent a grueling weekend auditing legacy corporate routing equipment that had not been updated in over a decade. Strange packet headers kept throwing warnings on the monitoring dashboard, causing endless frustration.

First attempt: Minh assumed it was a standard IPv4 fragmentation bug and started rewriting the subnet masks. Result: Total network traffic dropped, locking out half the office printers and creating complete administrative chaos.

After digging through dusty vendor documentation and rare networking forums, he realized the legacy firmware was misinterpreting old packet version codes, mistaking specialized control frames for malformed data.

He patched the routing filters and isolated the offending legacy hardware. Response times normalized within 48 hours, proving that even obsolete protocol quirks can still haunt modern enterprise infrastructure if left unchecked.