Port 1172 carries the DNA Protocol (DNAP)—short for Digital Network Architecture, the network protocol suite that Digital Equipment Corporation (DEC) created to connect its diverse computer systems.
What the DNA Protocol Does
DNA Protocol is the architectural model for DECnet, DEC's family of network implementations. It was designed to create a communications environment among heterogeneous computers—PDP-11s, VAX systems, and various other machines that all needed to talk to each other.12
This was genuinely difficult in the 1970s. Each computer company had its own vision of networking. IBM had SNA (Systems Network Architecture). DEC had DNA. Xerox had XNS. Before TCP/IP became the universal language of networks, these proprietary protocols competed to define how computers would communicate.
The History
DEC published its first DNA specification in the early 1970s, around the same time IBM announced SNA.2 The architecture evolved through several phases:
Phase I (1974) — Communication limited to two PDP-11s running RSX-11, or a small number of PDP-8s running RTS-8, over point-to-point links. Two computers. That was the beginning.1
Phase II (1975) — Support for networks of up to 32 nodes, with implementations expanded to include RSTS, TOPS-10, TOPS-20, and VAX/VMS. Different operating systems could finally talk to each other—if they were all from DEC.1
Phase IV — Networks grew to support up to 64,449 nodes (63 areas of 1,023 nodes each) with 16-bit addresses. Datalink capabilities expanded beyond DDCMP to include Ethernet.2
Phase V (1987) — Support for architecturally unlimited networks and a move toward Open Systems Interconnection (OSI) standards, integrating ISO standards for multi-vendor connectivity.2
While the DECnet protocols were designed entirely by Digital Equipment Corporation, DECnet Phase II and later versions were open standards with published specifications.1
Port 1172 Today
Port 1172 was officially registered with IANA for the DNA Protocol in 2004, long after DEC's networks had largely been replaced by TCP/IP.3 The port works with both TCP and UDP.
You'll rarely encounter DNA Protocol on modern networks. DEC was acquired by Compaq in 1998, which was then acquired by HP in 2002. The computer systems that spoke DNA are mostly retired. But the port assignment remains—a marker in the registry of a time when the question "how should computers talk to each other?" had many competing answers.
What Range This Port Belongs To
Port 1172 falls in the registered ports range (1024-49151). These ports are assigned by IANA for specific services that any user or process can use—not privileged like the well-known ports (0-1023), but not free-for-all like the dynamic ports (49152-65535).
Registered ports need IANA approval. Someone had to request port 1172 for DNA Protocol. Someone wrote the specification, submitted the application, got it approved. Even for a protocol that the world had mostly moved past.
How to Check What's Listening
On Linux or macOS:
On Windows:
If something is actually using port 1172 on your network in 2026, you've either found legacy DEC equipment that somehow survived, or something else has unofficially claimed the port.
Why This Port Matters
DNA Protocol represents the era before the Internet's victory was inevitable. In the 1970s and 1980s, there was genuine uncertainty about which network architecture would win. TCP/IP wasn't obviously the future—it was just one option among many.
DEC bet on DNA. IBM bet on SNA. Xerox bet on XNS. TCP/IP won because it was simple, open, and good enough—not because it was perfect.
Port 1172 is a fossil from that era. A reminder that the network we have today—where everything speaks TCP/IP and port numbers are universal—wasn't preordained. It's the result of a standards war that TCP/IP won so thoroughly that we've almost forgotten there was ever a fight.
Frequently Asked Questions About Port 1172
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