IP Security Protocol (IPSEC) (EXPERIMENTAL)
CONFIG_IPSEC
  This unit is experimental code.
  Pick 'y' for static linking, 'm' for module support or 'n' for none.
  This option adds support for network layer packet encryption and/or
  authentication with participating hosts.  The standards start with:
  RFCs 2411, 2407 and 2401.  Others are mentioned where they refer to
  specific features below.  There are more pending which can be found
  at:  ftp://ftp.ietf.org/internet-drafts/draft-ietf-ipsec-*.
  A description of each document can also be found at: 
  http://ietf.org/ids.by.wg/ipsec.html.
  Their charter can be found at: 
  http://www.ietf.org/html.charters/ipsec-charter.html
  Snapshots and releases of the current work can be found at: 
  http://www.freeswan.org/

IPSEC: IP-in-IP encapsulation
CONFIG_IPSEC_IPIP
  This option provides support for tunnel mode IPSEC.  It is recommended
  to enable this.

IPSEC: Authentication Header
CONFIG_IPSEC_AH
  This option provides support for the IPSEC Authentication Header
  (IP protocol 51) which provides packet layer sender and content
  authentication.  It is recommended to enable this.  RFC2402

HMAC-MD5 algorithm
CONFIG_IPSEC_AUTH_HMAC_MD5
  Provides support for authentication using the HMAC MD5
  algorithm with 96 bits of hash used as the authenticator.  RFC2403

HMAC-SHA1 algorithm
CONFIG_IPSEC_AUTH_HMAC_SHA1
  Provides support for Authentication Header using the HMAC SHA1
  algorithm with 96 bits of hash used as the authenticator.  RFC2404

IPSEC: Encapsulating Security Payload
CONFIG_IPSEC_ESP
  This option provides support for the IPSEC Encapsulation Security
  Payload (IP protocol 50) which provides packet layer content
  hiding.  It is recommended to enable this.  RFC2406

3DES algorithm
CONFIG_IPSEC_ENC_3DES
  Provides support for Encapsulation Security Payload protocol, using
  the triple DES encryption algorithm.  RFC2451

IPSEC Debugging Option
CONFIG_IPSEC_DEBUG
  Enables IPSEC kernel debugging.  It is further controlled by the
  user space utility 'klipsdebug'.