abbrev. name value END end of SDES list 0 CNAME canonical name 1 NAME user name 2 EMAIL user's electronic mail address 3 PHONE user's phone number 4 LOC geographic user location 5 TOOL name of application or tool 6 NOTE notice about the source 7 PRIV private extensions 8
Other constants are assigned by IANA. Experimenters are encouraged to register the numbers they need for experiments, and then unregister those which prove to be unneeded.