Protocols and standards
CSID
Acronym: CSID
The CSID is the identification string a fax machine announces to its counterpart during negotiation, usually its own number.
It appears on the transmission report and in the printed header of each page. It is worth knowing that it is declarative: it is configured by the machine's owner, not assigned by the network. It therefore identifies a machine presenting itself as such — useful information, but not authentication, and it should not be presented as one.