Discard Protocol
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| Internet protocol suite |
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| Application layer |
| Transport layer |
| Internet layer |
| Link layer |
The Discard Protocol is a service in the Internet Protocol Suite defined in RFC 863. It is intended for testing, debugging, and measurement purposes.
A host may send data to a host that supports the Discard Protocol on either Transmission Control Protocol (TCP) or User Datagram Protocol (UDP) port number 9. The data sent to the server is simply discarded. No response is returned.
Inetd implementation
On most UNIX-like operating systems a discard server is built into the inetd (or xinetd) daemon. The discard service is usually not enabled by default. It may be enabled by adding the following lines to the file /etc/inetd.conf and reloading the configuration:
discard stream tcp nowait root internal discard dgram udp wait root internal
The Discard Protocol is the TCP/UDP equivalent of the Unix filesystem node /dev/null. Such a service is guaranteed to receive what is sent to it and can be used for debugging TCP and/or UDP code requiring a guaranteed reception of payload sent.
On various routers, this TCP or UDP port 9 for the Discard Protocol (or port 7 for Echo/ICMP) is also used by default as a proxy to relay Wake-on-LAN (WOL) from the Internet to hosts on the local network in order to wake up them remotely (these hosts must also have their network adapter configured to accept WOL datagrams).
See also
External links
- RFC 348, The Discard process
- RFC 863, The Discard protocol