RFC 863 INTERNET STANDARD APPLICATIONS · DIAGNOSTICS

Discard Protocol

A small service that silently throws away whatever it receives, used for debugging and measurement.

RFC EDITOR

Postel, J., "Discard Protocol", STD 21, RFC 863, DOI 10.17487/RFC0863, May 1983, <https://www.rfc-editor.org/info/rfc863>.

BIBTEX

@misc{rfc863,
  series = {Request for Comments},
  number = 863,
  howpublished = {RFC 863},
  publisher = {RFC Editor},
  doi = {10.17487/RFC0863},
  url = {https://www.rfc-editor.org/info/rfc863},
  author = {J. Postel},
  title = {{Discard Protocol}},
  pagetotal = 1,
  year = 1983,
  month = may,
}

PUBLISHED: May 1983
AUTHORS: J. Postel
STREAM: Legacy
TCP PORT: 9
UDP PORT: 9
RESPONSE: None
DOI: 10.17487/RFC0863

RFC text

Original text · RFC Editor View on rfc-editor.org ↗

Network Working Group                                          J. Postel
Request for Comments: 863                                            ISI
                                                                May 1983



                            Discard Protocol




This RFC specifies a standard for the ARPA Internet community.  Hosts on
the ARPA Internet that choose to implement a Discard Protocol are
expected to adopt and implement this standard.

A useful debugging and measurement tool is a discard service.  A discard
service simply throws away any data it receives.

TCP Based Discard Service

   One discard service is defined as a connection based application on
   TCP.  A server listens for TCP connections on TCP port 9.  Once a
   connection is established any data received is thrown away.  No
   response is sent.  This continues until the calling user terminates
   the connection.

UDP Based Discard Service

   Another discard service is defined as a datagram based application on
   UDP.  A server listens for UDP datagrams on UDP port 9.  When a
   datagram is received, it is thrown away.  No response is sent.

ISO Plain Language

On this page

PROBLEMNetwork engineers need a very simple place to send data that will accept it and do nothing with it, for debugging and measuring.

MECHANISMA discard service throws away any data it receives and sends no response, listening on port 9 over either TCP or UDP.

STATUS TODAYHosts that choose to implement a Discard Protocol are expected to follow this standard, and implementing it is optional.

§1What a Discard Service Is

The RFC introduces the discard service as a useful debugging and measurement tool, and describes it in one line: it simply throws away any data it receives.

Hosts on the ARPA Internet that choose to implement a Discard Protocol are expected to adopt and implement this standard.

You send it data and it never sends anything back. That makes it handy for testing.

§2TCP and UDP Discard

The TCP-based discard service is a connection based application. A server listens for TCP connections on TCP port 9. Once a connection is established, any data received is thrown away and no response is sent. This continues until the calling user terminates the connection.

The UDP-based discard service is a datagram based application. A server listens for UDP datagrams on UDP port 9. When a datagram is received, it is thrown away and no response is sent.

Over a connection it keeps listening until you close it, and stays silent. For single messages it takes each one and drops it, also silently.

§3Standard Status

RFC 863 is an Internet Standard from May 1983. The text defines only the two port 9 behaviors described above, and offers no other detail.

It is a listener that never answers: whatever is sent to it simply disappears.