4.1 Access-Request

4.1. Access-Request

Description

  Access-Request packets are sent to a RADIUS server, and convey
  information used to determine whether a user is allowed access to
  a specific NAS, and any special services requested for that user.
  An implementation wishing to authenticate a user MUST transmit a
  RADIUS packet with the Code field set to 1 (Access-Request).

  Upon receipt of an Access-Request from a valid client, an
  appropriate reply MUST be transmitted.

  An Access-Request SHOULD contain a User-Name attribute.  It MUST
  contain either a NAS-IP-Address attribute or a NAS-Identifier
  attribute (or both).

  An Access-Request MUST contain either a User-Password or a CHAP-
  Password or a State.  An Access-Request MUST NOT contain both a
  User-Password and a CHAP-Password.  If future extensions allow
  other kinds of authentication information to be conveyed, the
  attribute for that can be used in an Access-Request instead of
  User-Password or CHAP-Password.

  An Access-Request SHOULD contain a NAS-Port or NAS-Port-Type
  attribute or both unless the type of access being requested does
  not involve a port or the NAS does not distinguish among its
  ports.

  An Access-Request MAY contain additional attributes as a hint to
  the server, but the server is not required to honor the hint.

  When a User-Password is present, it is hidden using a method based
  on the RSA Message Digest Algorithm MD5 [3].

A summary of the Access-Request packet format is shown below. The fields are transmitted from left to right.

0                   1                   2                   3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1

Code

  1 for Access-Request.

Identifier

  The Identifier field MUST be changed whenever the content of the
  Attributes field changes, and whenever a valid reply has been
  received for a previous request.  For retransmissions, the
  Identifier MUST remain unchanged.

Request Authenticator

  The Request Authenticator value MUST be changed each time a new
  Identifier is used.

Attributes

  The Attribute field is variable in length, and contains the list
  of Attributes that are required for the type of service, as well
  as any desired optional Attributes.