120

Port 120/tcp is registered with IANA as cfdptkt with the description "CFDPTKT," assignee and contact John Ioannidis, and a blank reference field — it is dual-registered on TCP and UDP (both rows carry identical fields). The service name traces to RFC 1235, "Coherent File Distribution Protocol" (CFDP), an Experimental specification by J. Ioannidis and G. Q. Maguire Jr. published in June 1991. CFDP was designed to speed up one-to-many file transfer over broadcast-capable LAN media — for example, simultaneously booting many diskless workstations or pushing a software update to every host at a site — by using a ticket-based handshake to avoid redundant per-host unicast transfers. Port 120 (cfdptkt) specifically was the recommended listening port for the minimal "ticket server" component of that protocol: a client first acquires a ticket, then the actual file distribution proceeds over broadcast. Two independent angles (the IANA registry and RFC 1235 read directly) agree on the name, description, and assignee, so those are treated as confirmed; RFC 1235 is a primary source for the port-to-protocol link even though IANA's own Reference column for this row is blank and no RFC is cited there. One disambiguation is worth carrying onto the page: this 1991 "CFDP" (Coherent File Distribution Protocol) is unrelated to the later, better-known "CCSDS File Delivery Protocol" (also abbreviated CFDP) used in aerospace and satellite systems such as NASA's Core Flight System — the acronym collision is coincidental and has no bearing on port 120. For an analyst, cfdptkt is a dormant, experimental early-1990s protocol: no current, actively maintained software was found implementing it on port 120, and no Shodan/Censys/threat-intel exposure data specific to this port surfaced, so real-world traffic on it is expected to be rare and worth treating as an anomaly rather than a known service. Both the "no modern implementation" and "no exposure data" findings are sourced nulls — absence of evidence in this pass, not a proof of absence.

IANA assignment

cfdptkt — "CFDPTKT"; reference (blank — no RFC cited in IANA registry); assignee/contact John Ioannidis; dual-registered 120/tcp + 120/udp [Confirmed] — IANA Service Name and Transport Protocol Port Number Registry (local cached CSV, tcp+udp rows) and iana.org registry

Range class

well-known (0–1023) [Confirmed]

Registration/modification dates

blank in the IANA registry for this entry — not fabricated [Confirmed] — service-names CSV (blank columns)

Related ports

other early experimental/file-distribution and small-service registrations of the era

Primary use

ticket-server port for CFDP, the Coherent File Distribution Protocol (RFC 1235, June 1991, Experimental) — broadcast/one-to-many LAN file distribution with a ticket handshake

Protocol origin

RFC 1235, "Coherent File Distribution Protocol," J. Ioannidis & G. Q. Maguire Jr., June 1991, Experimental status

Exposure / scanning

Unknown — no Shodan/Censys/threat-intel statistics specific to port 120 surfaced; consistent with (but not proof of) very low real-world exposure given the protocol's age [Unknown] (sourced null)

Disambiguation

the RFC 1235 "Coherent File Distribution Protocol" behind cfdptkt is NOT the CCSDS "File Delivery Protocol" (also abbreviated CFDP) used in NASA/aerospace systems; the acronym collision is coincidental [Confirmed] — github.com/nasa/CF, en.wikipedia.org/wiki/CFDP

Current implementations

Unknown — no current, actively maintained software found implementing cfdptkt on port 120; appears legacy/dormant [Unknown] (sourced null; no implementation surfaced in web search)

Corroboration

secondary port-lookup aggregators (portsmaster, speedguide) list 120/cfdptkt consistent with IANA, used only as corroboration [Likely] — portsmaster.net/port-120, speedguide.net

Analyst note

cfdptkt is a dormant 1991 experimental protocol with no evidence of modern deployment — an open/answering port 120 is statistically rare and worth investigating rather than assuming a live CFDP ticket server.

Port 120/udp is registered with IANA under the service name cfdptkt, assignee and contact John Ioannidis, and a blank reference field; it is dual-registered on both TCP and UDP with identical assignee and contact. The service name refers to the ticket-server component of the Coherent File Distribution Protocol (CFDP), described in RFC 1235 (J. Ioannidis and G. Q. Maguire Jr., June 1991, Experimental status). RFC 1235 designs CFDP as a way to distribute a file efficiently to many hosts on a broadcast network: a client first sends a Request-Ticket (REQTKT) datagram to the ticket server so that a bulk transfer can be coordinated before the file is delivered over a separate CFDP data channel. The cfdptkt name marks the port that ticket-server handshake was intended to use. In practice this is a legacy, experimental-era protocol from the early Internet; RFC 1235 was never advanced beyond Experimental and there is no sourced evidence of actively maintained, currently shipping software that implements CFDP ticket-server functionality on this port today. The IANA registry's Reference column for this entry is blank — no RFC is cited there — so although RFC 1235 is the well-documented historical protocol document, it is recorded here as background context rather than as the IANA reference. Both the TCP and UDP registry lines carry the identical description "CFDPTKT". For an analyst, an open UDP port 120 is a rarity with no confirmed modern legitimate use, and no dated exposure or scanning statistics for this specific port were located, so it warrants investigation rather than assumption of benign service.

IANA assignment

cfdptkt — description "CFDPTKT" (identical on both the TCP and UDP lines); reference (blank — no RFC cited in IANA registry); assignee and contact John Ioannidis; dual-registered 120/tcp + 120/udp [Confirmed] — IANA Service Name and Transport Protocol Port Number Registry (the IANA Service Name and Transport Protocol Port Number Registry, cached registry lines 309-310; https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.txt)

Range class

well-known / System Ports (0–1023) [Confirmed] — IANA port-range definitions

Related ports

120/tcp (same cfdptkt registration, identical assignee/contact)

Primary use

CFDP (Coherent File Distribution Protocol) ticket-server handshake; a client sends a Request-Ticket (REQTKT) datagram to UDP port 120 to coordinate a bulk file distribution over a separate data channel

Protocol status

RFC 1235, "Coherent File Distribution Protocol," June 1991, Experimental — never advanced beyond Experimental; NOT listed as the IANA Reference for this entry

Common software implementations

Unknown — no sourced evidence of actively maintained software implementing CFDP ticket-server on this port today; port-aggregator sites republish the IANA name without evidence of live usage

Exposure / scanning

Unknown — no dated, port-120-specific Shodan/Censys count or advisory located; general UDP-scan reconnaissance context is not a port-120-specific finding [Unknown]

Analyst note

A legacy/experimental service with no confirmed modern legitimate use; an open UDP 120 is statistically rare — investigate rather than assume benign, and do not attribute a specific exposure statistic (none verified).