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Identification Protocol (RFC1413)

IP.com Disclosure Number: IPCOM000002239D
Original Publication Date: 1993-Feb-01
Included in the Prior Art Database: 2019-Feb-10
Document File: 8 page(s) / 11K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

M. St. Johns: AUTHOR

Related Documents

10.17487/RFC1413: DOI


The Identification Protocol was formerly called the Authentication Server Protocol. It has been renamed to better reflect its function. [STANDARDS-TRACK]

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 21% of the total text.

Network Working Group M. St. Johns Request for Comments: 1413 US Department of Defense Obsoletes: 931 February 1993

Identification Protocol

Status of this Memo

This RFC specifies an IAB standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "IAB Official Protocol Standards" for the standardization state and status of this protocol. Distribution of this memo is unlimited.


The Identification Protocol (a.k.a., "ident", a.k.a., "the Ident Protocol") provides a means to determine the identity of a user of a particular TCP connection. Given a TCP port number pair, it returns a character string which identifies the owner of that connection on the server’s system.

The Identification Protocol was formerly called the Authentication Server Protocol. It has been renamed to better reflect its function. This document is a product of the TCP Client Identity Protocol Working Group of the Internet Engineering Task Force (IETF).


This is a connection based application on TCP. A server listens for TCP connections on TCP port 113 (decimal). Once a connection is established, the server reads a line of data which specifies the connection of interest. If it exists, the system dependent user identifier of the connection of interest is sent as the reply. The server may then either shut the connection down or it may continue to read/respond to multiple queries.

The server should close the connection down after a configurable amount of time with no queries - a 60-180 second idle timeout is recommended. The client may close the connection down at any time; however to allow for network delays the client should wait at least 30 seconds (or longer) after a query before abandoning the query and closing the connection.

St. Johns [Page 1]

RFC 1413 Identification Protocol February 1993


Queries are permitted only for fully specified connections. The query contains the local/foreign port pair -- the local/foreign address pair used to fully specify the connection is taken from the local and foreign address of query connection. This means a user on address A may only query the server on address B about connections between A and B.


The server accepts simple text query requests of the form:

<port-on-server> , <port-on-client>

where <port-on-server> is the TCP port (decimal) on the target (where the "ident" server is running) system, and <port-on-client> is the TCP port (decimal) on the source (client) system.

N.B - If a client on host A wants to ask a server on host B about a connection specified locally (on the client’s machine) as 23, 6191 (an inbound TELNET connection), the client must actually ask about 6191, 23 - which is how the connection would be specified on host B.

For example:

6191, 23

The response is of the form

<port-on-server> , <port-on-client> : <resp-type> : <add-info>

where <port-on-server>,<port-on-c...