IP Small Services

Echo uses UDP and TCP port 7 and is used as a debgging tool to send any datagrams received from a source, back to that source. The risk with this is that someone who has access to the network can overload devices via the Echo service amounting to a DoS attack.

RFC 862 describes the Echo service.

Discard is another debugging tool where data is sent to port 9 and the recipient simply throws it away. This data can either be a UDP packet or a TCP stream that is opened until closed by the sender.

RFC 863 describes the Discard service.

Chargen is short for Character Generator and is a service that generates random characters either in one UDP packet containing a random number (between 0 and 512) of characters, or a TCP session. The UDP Chargen server looks for a UDP packet on port 19 and responds with the random character packet.

With TCP Chargen, the server sends as a continuous stream of TCP packets once a connection is made, and until the session closes. The data is thrown away. Chargen is used to find the cause for dropped packets. It uses TCP/UDP port 19. An infiltrator can create a DoS attack by spoofing an IP address and causing two devices to send random traffic to each other.

RFC 864 describes the Chargen service.

The Daytime protocol is another testing tool and uses port 13 for both UDP and TCP versions. On receipt of a datagram to port 13, the server in the UDP version, sends the current date and time in ASCII format in a datagram. The TCP version, on receipt of a datagram to port 13, and once the connection is established, sends the date and time in ASCII format and closes the connection.

RFC 867 describes the Daytime service.

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