[Docs] [txt|pdf] [Tracker] [Email] [Nits]

Versions: 00 01 02 03 04 05 06 07 08 09 10 11 RFC 5570

Network Working Group                                M. StJohns, Nominum
Internet-Draft                             R. Atkinson, Extreme Networks
                                           G. Thomas, US Dept of Defense
draft-stjohns-sipso-00.txt                              15 February 2007


                          Son of IPSO (SIPSO)
               A Simple IPv6 Sensitivity Labeling Option



Status of this Memo

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware have been
   or will be disclosed, and any of which he or she becomes aware will be
   disclosed, in accordance with Section 6 of BCP 79.

   Internet-Drafts are working documents of the Internet Engineering Task
   Force (IETF), its areas, and its working groups. Note that other groups may
   also distribute working documents as Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months and
   may be updated, replaced, or obsoleted by other documents at any time. It
   is inappropriate to use Internet-Drafts as reference material or to cite
   them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/1id-abstracts.html

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.


ABSTRACT


     This document describes an optional method for encoding explicit packet
   sensitivity labels on IPv6 packets.  It is intended for use only within
   multi-level secure (MLS) networking environments that are both trusted
   and trustworthy.


1.  INTRODUCTION


        The original IPv4 specification in RFC-791 includes an option for
   labeling the sensitivity of IP packets. That option was revised by RFC-1038
   and later by RFC-1108.

       One or another IP sensitivity label option has been in limited
   deployment for about two decades, most usually in governmental or military
   internal networks.  There are also some commercial sector deployments where
   corporate security policies require mandatory access controls be applied to
   sensitive data.  For example, some banks use MLS technology to compartment
   information known to their investment banking staff so that their trading
   staff is unaware of that information.  This document specifies the explicit
   packet labeling extensions for IPv6 packets.


1.1 History


        This document is a direct descendent of RFC-1038 and RFC-1108 and is
   a close cousin to the work done in the Commercial IP Security Option
   (CIPSO) Working Group of the Trusted Systems Interoperability Group (TSIG).
   [FIPS-188] The IP Security options defined by 1038 and 1108 were designed
   with one specific purpose in mind: to support the fielding of an IPv4
   packet encryption device called a BLACKER.  Because of this, the
   definitions and assumptions in those documents were necessarily focused
   on the US Department of Defense and the BLACKER device.  Today, packet
   sensitivity labeling is most commonly deployed within multi-level secure
   (MLS) environments, often composed of Compartmented Mode Workstations
   (CMWs) connected via a Local Area Network (LAN).  So the mechanism defined
   here is accordingly more general than RFC-1038 or RFC-1108 were.

            Also, the deployment of Compartmented Mode Workstations ran into
   operational constraints caused by the limited, and relatively small,
   space available for IPv4 options.  This caused one non-IETF specification
   for IPv4 packet labeling to have a large number of sub-options.  A very
   unfortunate side-effect of having sub-options within an IPv4 label option
   was that it became much more challenging to implement intermediate-system
   support for mandatory access controls (e.g. in a router or MLS guard
   system) and still be able to forward traffic at or near wire-speed.
   In the last decade, typical Ethernet link speeds have changed from 10 Mbps
   half-duplex to 1 Gbps full-duplex.  A 10 Gbps full- duplex Ethernet
   standard is widely available today.  The IEEE is actively developing a
   standard for 100 Gbps Ethernet as of this writing.  Forwarding at those
   speeds typically requires support from ASICs; supporting more complex
   packet formats usually require significantly more gates than simpler packet
   formats.  So the pressure to have a simple option format has only increased
   in the past decade.

        When IPv6 was initially being developed, it was anticipated that
   the availability of IP Security, in particular the Encapsulating Security
   Payload (ESP) and the IP Authentication Header (AH), would obviate the need
   for explicit packet sensitivity labels with IPv6. [RFC-1825] For MLS IPv6
   deployments where the use of AH or ESP is practical, use of AH and/or ESP
   is recommended.  However, some application architectures, most often
   those not designed for use with Compartmented Mode Workstations or other
   Multi-Level Secure (MLS) computers, multiplex transactions at different
   sensitivity levels and/or with different privileges over a single
   transport-layer communications session. In order to maintain data
   sensitivity labeling for such applications, in order to be able to
   implement routing and mandatory access control decisions in routers and
   guards on a per-IP-packet basis, and for other reasons, there is a need
   to have a mechanism for explicitly marking the sensitivity information
   for each IPv6 packet.


1.2.  Intent


        This document describes a generic way of marking IPv6 datagrams
   to reflect their particular sensitivity.  Provision is made for separating
   data based on domain of interpretation, relative sensitivity
   (i.e.  security levels), need-to-know or formal access programs
   (i.e. compartments or categories), and releasabilities.

           In particular, the authors believe that this mechanism is
   suitable for deployment in UN peace-keeping operations, in NATO operations,
   in all current US Government MLS environments, and for deployment
   in other similar commercial or governmental environments.


2.  DEFINITIONS


        This section defines several terms that are important to understanding
   and correctly implementing this specification.  Because of historical
   variations in terminology in different communities, several terms have
   defined synonyms.


2.1.  Domain of Interpretation


        A Domain of Interpretation (DOI) is a shorthand way of identifying
   the use of a particular marking, classification and handling system with
   respect to data, the computers and people who process it, and the networks
   that carry it.  The DOI policies, combined with a particular marking
   (which is defined to have meaning within that DOI) applied to a datum or
   collection of data, dictates which systems, and ultimately which persons
   may receive that data.  In other words a marking of "SECRET" by itself is
   not meaningful; you also have to know the document or data belongs to the
   US Department of Defense before you can decide on who is allowed to receive
   the data.

        An SIPSO DOI is an opaque identifier that is used as a pointer to a
   particular set of policies which define the security levels and categories
   present within the DOI, and by inference, to the "real world" equivalent
   markings (See "Sensitivity Label" below).  Registering or defining a set
   of real world security policies as an SIPSO DOI results in a standard way
   of marking IP data originating from end-systems "accredited" or "approved"
   to operate within that DOI and the constraints of those security policies.
   For example, if one did this for the US Department of Defense, you would
   list all the acceptable markings such as "Secret" and "Top Secret",
   and one would link the SIPSO DOI to the DOD 5200.28 and DOD 5200.1R
   documents which define how to mark and protect data with the US
   Department of Defense (DoD).[DoD 5200.28][DoD 5200.1-R]

        The scope of the DOI is dependent on the organization establishing
   it. For example, the US might establish a DOI with specific meanings
   which correspond to the normal way its marks classified documents and
   which would apply primarily to the DOD, but might also apply to other
   associated agencies.  A company or other organisation might establish
   a DOI which applies only to itself.

           Note well: A SIPSO Domain of Interpretation is different from,
   and disjoint from, an ISAKMP/IKE Domain of Interpretation.  It is
   important not to confuse the two terms.


2.2.  Sensitivity Level


        A security level represents a mandatory separation of data based
   on relative sensitivity.  Security levels ALWAYS have a specific ordering
   within a DOI.  Clearance to access a specific level of data also implies
   access to all levels whose sensitivity is less than that level.  For
   example, if the A, B and C are levels, and A is more sensitive than B
   which is in turn more sensitive than C (A > B > C), access to data
   at the B level implies access to C as well. As an example, common
   UK terms for a security level include "Unclassified", "Restricted",
   "Confidential", "Secret", and "Most Secret".

         Note well: A sensitivity level is only one component of a sensitivity
   label.  It is important not to confuse the two terms. The term "sensitivity
   level" has the same meaning as the term "security level".


2.3.  Compartment


        A compartment represents a mandatory segregation of data based
   on formal information categories or formal access programs for specific
   types of data.  For example, a small startup company creates "Finance"
   and "R&D" compartments to protect data critical to its success --
   only employees with a specific need to know (e.g. the accountants
   and controller for "Finance", specific engineers for "R&D") are given
   access to each compartment.  Each compartment is separate and distinct.
   Access to one compartment does not imply access to any other compartment.
   Data may be protected in multiple compartments (e.g. "Finance" data
   about a new "R&D" project), in which case access to ALL of those
   compartments is required to access the data. Employees only possessing
   clearance for a given sensitivity level (i.e. without having clearance
   for any specific compartments at that sensitivity level) do not have
   access to any data classified in any compartments (e.g. SECRET FINANCE
   dominates SECRET).

        The term "category" has the same meaning as "compartment".


2.4   Releasability


         A releasability represents a mandatory segregation of data based
   on a formal decision to release information to others. Historically,
   some MLS deployments handled releasability as if it were a compartment,
   but this is problematic, because the semantics of a compartment are
   different from the semantics of a releasability.

             For example, two companies (ACME and ACE) are engaging in a
   technical alliance.  ACME marks all information present within its
   enterprise that is to be shared as part of the alliance as REL ACE
   (e.g.COMPANY CONFIDENTIAL REL ACE).  However, unlike the category example
   above, COMPANY CONFIDENTIAL dominates COMPANY CONFIDENTIAL REL ACE.
   This means that ACE employees granted a COMPANY CONFIDENTIAL REL ACE
   clearance can only access releasable material, while ACME employees
   with a COMPANY CONFIDENTIAL clearance can access all information.
   If REL ACE were managed as a compartment, then users granted a
   COMPANY CONFIDENTIAL REL ACE clearance would have access to all of
   ACME's COMPANY CONFIDENTIAL material, which is undesirable.
   Releasabilities can be combined (e.g. COMPANY CONFIDENTIAL REL ACE/ABLE).
   In this case, users possessing a clearance of either COMPANY CONFIDENTIAL,
   COMPANY CONFIDENTIAL REL ACE, COMPANY CONFIDENTIAL REL ABLE,
   or COMPANY CONFIDENTIAL REL ACE/ABLE can access this information.


2.5.  Sensitivity Label


        A sensitivity label is a quadruple consisting of a DOI, a Sensitivity
   Level, a Compartment Set, and a Releasability Set.  The Compartment Set
   may be the empty set if and only if no compartments apply.  A Releasability
   Set may be the empty set if only if no releasabilities apply.  A DOI
   used within a end system may be implicit or explicit depending on its use.
   SIPSO Sensitivity Labels always have an explicit DOI. A SIPSO sensitivity
   label consists of a sensitivity label of a particular format (defined
   below) and ALWAYS contains an explicit DOI.

          A system which does not store a DOI as part of its internal
   sensitivity labels must be considered to have an implicit DOI --
   usually that of its primary Accrediting Authority; all objects
   on such a system inherit this implicit DOI.

           The term "security marking" has the same meaning as "sensitivity
   label".

2.5.1 Sensitivity Label Comparison

        Two Sensitivity Labels (A and B) can be compared. Indeed, the only
   real reason that sensitivity labels exist is so that they may be compared
   as part of an access control decision.  Comparison is critical to
   determining if a subject (a person, network, etc.) operating at one
   sensitivity label (A) should be allowed to access an object (file, packet,
   route, etc) classified at another sensitivity label (B).  The comparison
   of two labels (A and B) can return one (and only one) of the following
   results:

     1) A can dominate B (e.g. A=SECRET, B=UNCLASSIFIED); A can read B
     2) B can dominate A (e.g. A=UNCLASSIFIED, B=SECRET); A cannot access B
     3) A equals B (e.g. A=SECRET, B=UNCLASSIFIED); A can read/write B
     4) A is incomparable B (e.g. A=SECRET R&D, B=SECRET FINANCE);
        A cannot access B

        By definition, if A and B are members of different DOIs, the result
   of comparison is always incomparable.  It is possible to overcome this
   if A and/or B can be promoted such that the labels are interpretable
   within a single DOI.

2.5.2  Range

        A range is a pair of sensitivity labels which indicate variously
   a minimum and maximum acceptable sensitivity label for objects compared
   against it.  A range is usually expressed as <minimum> : <maximum> and
   always has the property that the minimum marking is less than or equal
   to the maximum marking (e.g. Not incomparable).  A range where <minimum>
   equals <maximum> may be expressed simply as <minimum>; in this case,
   the only acceptable marking is <minimum>.

2.6.  Import

        The act of receiving a datagram and translating the SIPSO markings
   into the appropriate internal (end-system specific) marking.


2.7.  Export

        The act of selecting an appropriate DOI for an outbound datagram,
   translating the internal (end-system specific) marking into an SIPSO
   marking based on that DOI, and sending the datagram.  The selection
   of the appropriate DOI may be based on many factors including,
   but not necessarily limited to:

           Destination Port
           Protocol
           End-system
           Subnetwork
           Network
           Sending Interface
           Upper Level Protocol Information
           System Implicit/Default DOI

           Regardless of the DOI selected, the sensitivity label of the
   outbound datagram must be consistent with the security policy monitor
   of the originating system and the interpretation used by all other
   devices which will receive this packet.

2.8.  End System

        An End System is a host or router from which a datagram originates
   or to which a datagram is ultimately delivered.  The IPv6 community
   often uses the term Node for what is here called an End System.

2.9.  Intermediate System

        An Intermediate System is a host or router which receives and
   transmits a particular datagram without being either the source or
   destination of that datagram. A firewall or security guard device that
   applies security policies and forwards packets that comply with the
   security policies is another example of an intermediate system.
   An intermediate system may handle ("forward") a datagram without
   necessarily importing or exporting the datagram to/from itself.
   (N.B.  Any given system can be both an end system and an intermediate
   system -- which role the system assumes at any given time depends
   on the address of the datagram you are considering and the address(es)
   associated with that system.)

2.10 System Security Policy

        A system security policy (SSP) consists of a sensitivity label
   and the organizational security policies associated with content
   marked with a given security policy.  The SSP acts as a bridge
   between how the organization's mandatory access control policy is
   stated and managed and how the network implements that policy.

3.  ARCHITECTURE

      This document describes a convention for marking an IPv6 datagram
   within a particular system security policy.  The markings are designed
   for use within a Mandatory Access Control (MAC) system.  A real world
   example is the security classification system in use within the US
   Government.  Some data held by the government is "classified",
   and is therefore restricted by law to those people who have the
   appropriate "clearances".  Commercial examples also exist.  For example,
   one global electrical equipment company has a formal security policy
   that defines 6 different sensitivity levels for its internal data,
   ranging from "Class 1" to "Class 6" information.  Some financial
   institutions use multiple compartments to restrict access to certain
   information (e.g. mergers & acquisitions) to those working directly
   on those projects and to deny access to other groups within the
   company (e.g. equity trading).  A SIPSO Sensitivity Label is the
   network instantiation of a particular information security policy,
   and its related markings, classifications, compartments, and
   releasabilities.

         Some years ago, the mandatory access control policy for
   US classified information was specified formally in mathematical notation.
   As it happens, many other organisations have the same basic mandatory
   access control policy for information with differing ("vertical")
   sensitivity levels.  This document builds upon the formal definitions
   of Bell-LaPadula.[BL73] There are two basic principles "no write down"
   and "no read up".  The first rule means that an entity having minimum
   sensitivity level X must not be able to write information that is marked
   with a sensitivity level below X.  The second rule means that an entity
   having maximum sensitivity level X must not be able to read information
   having a sensitivity level above X.  In a normal deployment, information
   downgrading ("write down") must not occur automatically and may only occur
   if a person with appropriate privilege manually verifies the information
   is permitted to be downgraded before the s/he manually re-labels
   ("downgrades") the information.  Subsequent to the original work
   in this area, this formal model was extended to also support
   ("horizontal") compartments of information.

            This document extends Bell-LaPadula to accommodate the notion
   of separate Domains of Interpretation (DOI).  Each DOI constitutes
   a single comparable domain of sensitivity labels as stated by Bell-LaPadula.
   Sensitivity labels from different domains cannot be directly compared
   using Bell-LaPadula semantics.

                 This document is focused on providing standards for encoding
   sensitivity labels in packets, as well as certain standards for how
   these markings are to be interpreted and enforced at the IP layer.  This
   document recognizes that there are several kinds of application processing
   that occur above the IP layer that significantly impact end-to-end system
   security policy enforcement, but are out of scope for this document.
   In particular, how the network labeling policy is enforced within processing
   in an end system is critical, but beyond the scope of a network (IP) layer
   sensitivity label encoding standard.  Other specifications exist which
   discuss such details. [TCSEC] [CMW] [ISO-15408] [CC] [DoD MLOS PP]

            This standard does not preclude a end-system capable of providing
   labeled packets across some range of sensitivity labels.  A Compartmented
   Mode Workstation is an example of such an end-system.[CMW] This is
   useful if the end-system is capable of and accredited to separate
   processing across some range of sensitivity labels.  Such an node
   would have a range associated with it within the network interface
   connecting the node to the network.  As an example, an end-system
   has the range SECRET:TOP SECRET associated with it in the
   intermediate-system to which the node is attached.  SECRET processing
   on the node is allowed to traverse the internet to other SECRET:SECRET
   segments of the network, ultimately to a SECRET:SECRET node.  Likewise,
   TOP SECRET processing on the node is allowed to traverse the internet
   through TOP SECRET:TOP SECRET segments, ultimately to a
   TOP SECRET:TOP SECRET node.  The node in this case can allow a user
   on this node to access SECRET and TOP SECRET resources, provided
   the user holds the appropriate clearances and has been correctly
   configured.

        With respect to an internet, each distinct sensitivity label
   represents a separate virtual internet which shares the same physical
   internet.  There are rules for moving information between the various
   virtual internets.  The model we use within this document is based
   on the Bell-LaPadula model, but is extended to cover the concept
   of differing Domains of Interpretation.  Those internet entities
   implementing this protocol must enforce this separation of data.

        The SIPSO provides for both horizontal ("compartment") and
   vertical ("sensitivity level") separation of information, as well as
   separation based on DOI.  The basic rule is that data must not be
   delivered to a user or system that is not approved to receive it.

   Note well: wherever we say "not approved", we also mean "not cleared",
   "not certified", and/or "not accredited" as applicable in one's
   operational community.

        This specification does not enable AUTOMATIC relabeling of
   information, within a DOI or to a different DOI.  That is, neither
   automatic "upgrading" nor automatic "downgrading" of information are
   enabled by this specification.  Local security policies may allow some
   limited downgrading, but this normally requires the intervention of some
   human entity and is usually done within a end-system with respect to the
   internal marking, rather than on a network or in a intermediate-system
   (e.g. router, guard).  Automatic downgrading is not suggested operational
   practice; further discussion of downgrading is outside the scope of this
   protocol specification.

           Implementers of this specification MUST NOT permit automatic
   upgrading or downgrading of information in their implementation's default
   configuration.  If an implementation supports automatic downgrading or
   upgrading of information, there MUST be a well-documented configuration
   knob to enable/disable that feature and that knob should only be accessible
   to users having appropriate privilege.

           This specification does not preclude a node that implements this
   specification from supporting multiple DOIs concurrently.  Indeed, use of
   multiple DOIs might be operationally useful in deployments having very
   large numbers of compartments.  For example, such a deployment might have
   one set of related compartments in one DOI and a different set of
   compartments in a different DOI.  While this might make some
   implementations more complex, it might also reduce the typical size
   of the IPv6 SIPSO option in data packets.

        Moving information between any two DOIs is permitted if and only if
   the owners of the DOIs:
        1) Agree to the exchange,
        2) Publish a table of equivalencies which maps the SIPSO
           values of one DOI into the other and make that table
           available within the scope of those two DOIs

        The owners of two DOIs may choose to permit the exchange on or
   between any of their systems, or may restrict exchange to a small subset
   of the systems they own/accredit.  One way agreements are permissible,
   as are agreements which are a subset of the full table of equivalences.
   Actual administration of inter-DOI agreements is outside the scope of this
   document.

        When data leaves an end system it is "exported" to the network,
   and marked with a particular DOI, sensitivity level, compartment set,
   and releasability set (collectively termed a sensitivity label).  This
   sensitivity label is derived from the internal marking (the end-system
   specific implementation of a sensitivity label), and the export DOI.
   The export DOI is selected based on any of: the destination end-system,
   the destination network, the current DOI for an upper level protocol
   (e.g. TCP), or the system default.  See the rules under "USAGE - Export"
   later in this document.

         When data arrives at an end system, it is "imported" from the
   network to the end-system.  The data from the datagram takes on an
   internal marking based on the sensitivity label contained in the datagram.
   This assumes the datagram is marked with a recognizable DOI, there is
   a corresponding internal marking equivalent to the SIPSO sensitivity label,
   and the datagram is "within range" for the receiving logical interface.

           An host or router has one or more physical interfaces.  Each
   physical interface is associated with a physical network segment used
   to connect the node, router, LAN, or WAN.  Each physical interface has
   one or more sensitivity label ranges associated with it.  Sensitivity
   Label ranges from multiple DOIs must be enumerated separately.  Multiple
   ranges from the same DOI are permissible.

           Each host or router also may have one or more logical interfaces.
   A given logical interface is associated with one and only one physical
   interface.  Each logical interface has one or more sensitivity label ranges
   associated with it.  Sensitivity label ranges from multiple DOIs must be
   enumerated separately.  Multiple ranges from the same DOI are permissible.
   Each range associated with a logical interface must fall within a range
   defined for the corresponding physical interface.

           In transit, a datagram is handled based on its SIPSO sensitivity
   label and is usually neither imported to or exported from the various
   intermediate systems it transits.  There also is the concept of "SIPSO
   Gateways" which import data from one DOI and export it to another DOI
   such that the effective sensitivity label is not changed, it is merely
   represented using a different DOI.  In other words, such devices might
   provide on-the-fly remarking of packets at the boundaries between
   complete systems of hosts within a single DOI.

4. DEFAULTS

           Each intermediate-system or end-system is responsible for
   properly interpreting and enforcing the mandatory access control policy.
   Practically, this means that each node must evaluate the label on the
   inbound packet, ensure that this sensitivity label is valid for the
   originating node, and at a minimum only route the packet to an interface
   and node where the sensitivity label of the packet falls within the
   assigned range of that node.  Packets arriving at an node with an invalid
   sensitivity label should be discarded.  A sensitivity label is valid
   if and only if the sensitivity label falls within the range assigned
   to the originating node.

           If a packet is received from an node which is not aware of SIPSO
   sensitivity labels (i.e. unaware to assign sensitivity labels itself)
   and the packet is destined for an node which is sensitivity label aware,
   the receiving node will insert a sensitivity label.  This sensitivity
   label will be equal to the maximum sensitivity label assigned to the
   originating node if that is known.  If the receiving node does not
   know which sensitivity label is assigned to the originating node,
   the maximum sensitivity label of the interface the packet was
   received upon will be inserted.

           If a packet is to be sent to an node which is defined to not
   be sensitivity label aware, from an node which is label aware, then the
   sensitivity label MAY be removed upon transmission if and only if local
   security policy permits this.  The originating node is still responsible
   for ensuring that the sensitivity label on the packet falls within the
   sensitivity label range associated with the receiving node.


5.  FORMAT

        This section describes the format of the SIPSO option for use
   with IPv6 datagrams.  SIPSO is an IPv6 hop-by-hop option to ensure
   that a security gateway or router could apply access controls to
   IPv6 packets based on the SIPSO label carried by the packet.  An IPv6
   datagram must not ever contain more than one SIPSO label.

           This option format is designed with intermediate systems in mind.
   It is now common for a MLS network deployment to contain an intermediate
   systems acting as a guard (sometimes several acting as guards).  Such
   a guard device needs to be able to very rapidly parse the sensitivity
   label in each packet, apply ingress interface MAC policy, forward the
   packet while aware of the packet's sensitivity label, and then apply
   egress interface MAC policy.  At least one prior IP sensitivity labels
   option used a syntax that was unduly complex.

5.1.  Option Format

   ------------------------------------------------------------
   | Option Type | Option Length | Cmpt Length | Rel Length   |
   +-------------+---------------+-------------+--------------+
   |             SIPSO Domain of Interpretation               |
   +-------------+---------------+-------------+--------------+
   |  Sens Level |    RESERVED   |    CRC-16  Checksum        |
   ------------------------------------------------------------
   |      Compartment Bitmap (Optional; variable length)      |
   +-------------+---------------+-------------+--------------+
   |      Releasability Bitmap (Optional; variable length)    |
   +-------------+---------------+-------------+--------------+

5.1.1.  OPTION TYPE field

      This field contains an unsigned 8-bit value.  Its value is (to be
   assigned by IANA).  In the event the IPv6 packet is fragmented by the
   sending system, this option must be copied on fragmentation.

      The SIPSO option is an IPv6 Hop-by-Hop Option.  Following the
   nomenclature of RFC-2460, Section 4.2, the Option Data field of this
   option must have 4n+2 alignment.  The Option Data MUST not change
   en-route. If the option is not recognised by an intermediate system
   examining the packet, the option should be ignored.  If the option
   is not recognised by an End System receiving the packet,
   then the packet should be dropped.



5.1.2.  OPTION LENGTH field

        This field contains an unsigned integer 1 octet in size.  It has
   minimum value is 6.  This field specifies the Length of the option data
   field of this option in octets.  The Option Type and Option Length fields
   are not included in the length calculation.

5.1.3   COMPARTMENT LENGTH field

           This field contains an unsigned 8-bit integer.  The field
   specifies the size of the COMPARTMENT BITMAP field in 64-bit words.
   The minimum value is zero, which is only when the information in
   this packet is not in any compartment.

5.1.4   RELEASABILITY LENGTH field

           This field contains an unsigned 8-bit integer.  The field specifies
   the size of the RELEASABILITY BITMAP field in 64-bit words.  The minimum
   value is zero, which is used only when the information in this packet has
   no associated releasabilities.

5.1.5 DOMAIN OF INTERPRETATION field

           This field contains an unsigned 32-bit integer.  IANA maintains
   a registry with assignments of the DOI values used in this field.
   The DOI identifies the rules under which this datagram must be handled
   and protected.

   NOTE WELL: The DOMAIN OF INTERPRETATION where all 4 octets contain zero is
   defined to be the NULL DOI. The NULL DOI has no compartments and has a
   single level whose value and SIPSO representation are each zero. The NULL
   DOI MUST NOT ever appear on the wire.  If a packet is received containing
   the NULL DOI, that packet MUST be dropped and the event SHOULD be logged
   as a security fault.

5.1.6.  SENSITIVITY LEVEL field

           This contains an unsigned 8-bit value.  This field contains an
   opaque octet whose value indicates the relative sensitivity of the data
   contained in this datagram in the context of the indicated DOI.  The
   values of this field MUST be ordered, with 00000000 being the lowest
   sensitivity level and 11111111 being the highest sensitivity level.

           However, in a typical deployment, not all 256 sensitivity levels
   will be in use.  So the set of valid Sensitivity Level values depends
   upon the SIPSO DOI in use. This sensitivity ordering rule is necessary
   so that intermediate systems (e.g. routers or MLS guards) will be able
   to apply MAC policy with minimal per-packet computation and minimal
   configuration.

5.1.7   RESERVED field

           This field is reserved.  It MUST be set to all zeros by the
   originating node.  Receiving systems MUST zero this field upon receipt
   in order to reduce the potential bandwidth of network-derived covert
   channels.




5.1.8.  CRC-16 Checksum

        This field contains an unsigned 16-bit integer containing the
   CRC-16 checksum calculated over the entire SIPSO option in this packet.
   The checksum algorithm is the 16 bit CRC defined by ITU.

5.1.9.  Compartment Bitmap

        This contains a variable number of 64-bit words.  Each bit
   represents one compartment within the DOI.  Each "1" bit within an octet
   in the "Compartment Bitmap" field represents a separate compartment
   under whose rules the data in this packet must be protected.  Hence,
   each "0" bit indicates that the compartment corresponding with that bit
   is not applicable to the data in this packet.  The assignment of identity
   to individual bits within a Compartment Bitmap for a given DOI is left
   to the owner of that DOI.

5.1.10.  Releasability Bitmap

        This contains a variable number of 64-bit words.  Each bit
   represents one releasability within the DOI.  Each "1" bit within
   an octet in the Releasability Bitmap" field indicates that the release
   of this packet's data is permitted to the Release Category corresponding
   to that particular bit.  Hence, each "0" bit indicates that the release
   of this packet's data is NOT permitted to the Release Category
   corresponding with that bit.  The semantics of the Releasability
   Bitmap are always interpreted in the context of the DOI specified
   in the same SIPSO option.  The specification leaves the assignment
   of identity to individual bits within a Releasability Bitmap
   for a given DOI to the owner of that DOI.

       By way of example, each bit in the Releasability Bitmap might
   correspond with a distinct foreign country ("foreign" being relative
   to the owner of the DOI in use).  In such a case, then if all bits
   in the Releasability Bitmap were set to 0, the packet's data
   would not be releasable to any other country than the one indicated
   by the Domain of Interpretation.

5.2.  Packet Word Alignment considerations

       The basic option is variable length, due to three variable length
   fields (Compartment Bitmap and Releasability Bitmap).

           Intermediate Systems and most End Systems perform best when
   processing fixed length, fixed location items.  So the IPv6 base
   specification levies certain requirements on IPv6 optional headers.
   So the compartment bitmap fields must have length in quanta of
   64-bit words (e.g. 0 bits, 64 bits, 128 bits)

6.  USAGE

           This section describes specific protocol processing steps
   required for systems that claim to implement or conform with this
   specification.

6.1.  Sensitivity label Comparisons

           This section describes how comparisons are made between two
   sensitivity labels.  Implementing this comparison correctly is critical
   to the MLS system providing the intended Mandatory Access Controls (MAC)
   to network traffic entering or leaving the system.

           A sensitivity label consists of a DOI, a sensitivity label,
   zero or more compartments, and zero or more releasabilities.  The
   following notation will be used:

     A.DOI         = the DOI portion of sensitivity label A
     A.LEV         = the sensitivity portion of sensitivity label A
     A.COMP        = the compartments portion of sensitivity label A
     A.REL         = the releasabilities portion of sensitivity label A
     A:IGNOR       = A, less the compartment bits represented in IGNOR

6.1.1.  "Within Range"

        A sensitivity label, "M" is "within range" for a particular range
   "A:B:IGNOR" if and only if:

        1.  The range is a valid range.  A given range A:B:IGNOR is
            valid if and only if B:IGNOR is greater than A:IGNOR.
            This implies that A and B are members of the same DOI.

       2.  The DOI for the sensitivity label matches the DOI for both
           the low and high end of the range and, (M.DOI = A.DOI = B.DOI)

        3.   The sensitivity label has a Security Level which is greater
             than or equal to the Security Level contained in the low-end
             sensitivity label from the range and which is less than or equal
             to the Security Level contained in the high-end sensitivity
             label from the range and, (A.LEV <= M.LEV <= B.LEV)

        4.   The sensitivity label has a Compartment set which is a superset
             (proper or otherwise) of the compartment set contained in the
             sensitivity label from the low-end range and which is a subset
             (proper or otherwise) of the compartment set contained in the
             high end sensitivity label from the range.

        5.  The sensitivity label M has a Releasability set which is a subset
             (proper or otherwise) of the releasability set contained in the
             low end sensitivity label from the range and which is a superset
             (proper or otherwise) of the releasability set contained in the
             high end marking from the range.

         ((A.COMP & ^IGNOR) <= (M.COMP & ^IGNOR) <= (B.COMP & ^IGNOR))
                                 &&
                       (A.REL >= M.REL >= B.REL)

6.1.2.  "Less Than" or "Below Range"

        A sensitivity label "M" is "less than" a sensitivity label "A"
   while considering a set of ignorable compartments IGNOR, if and only if:

        1.   Their DOI's are identical (M.DOI = A.DOI), and
        2.   M's Security Level is less than A's Security Level
             M.LEV < A.LEV
        3.   M.COMP is a subset (proper or otherwise) of A.COMP,
             excluding compartments specified in IGNOR.
        4.   M.REL is a superset (proper or otherwise) of A.REL.

   Thus, a marking M is less than or equal to a marking A iff:

      ((  (M.LEV <= A.LEV)
       && ((M.COMP & ^IGNOR) < (A.COMP & ^IGNOR)))
       && (M.REL >= A.REL))

   A sensitivity label, "M", is "below range" for a sensitivity label,
   "A:B:IGNOR", if M is less than A.

6.1.3.  "Greater Than" or "Above Range"

        A sensitivity label, "M" is "greater than" a sensitivity label "B"
   while considering a set of ignorable compartments IGNOR if and only if:

        1.   Their DOI's are identical (M.DOI = B.DOI), AND
        2.   M's level is greater than B's level while M's compartment
             set is a superset (proper or otherwise) of B's compartment
          set (M.LEV > B.LEV & (M.COMP & ^IGNOR) >= (A.COMP & ^IGNOR)),
             OR
        3.   M's level is greater than or equal to A's level while
             M's compartment set is a proper superset of A's
             compartment set

        4.   M.REL is a subset (proper or otherwise) of A.REL

       ( (M.LEV >= B.LEV) &&
         ((M.COMP & ^IGNOR) > (B.COMP & ^IGNOR)) ) &&
         (M.REL <= A.REL) )

   A sensitivity label, "M", is "above range" for a sensitivity label,
   "A:B:IGNOR", if M is greater than B.

6.1.4.  "Equal To"

        A sensitivity label "A" is "equal to" another sensitivity label "B"
   while considering a set of ignorable compartments IGNOR if and only if:

        1.  They have the exact same DOI, and
        2.  they have identical security levels, and
        3.  their compartment sets are identical, and
        4.  their Releasability sets are identical.

        ((A.DOI == B.DOI) && (A.LEV == B.LEV)
      && ((A.COMP & ^IGNOR) == (B.COMP & IGNOR))
      && ((A.REL == B.REL))
        )

6.1.5.  "Disjoint" or "Incomparable"

        A marking "A" is disjoint from another marking "B" while considering a
   set of ignorable compartments IGNOR either if:

        1.   Their DOI's differ (A.DOI <> B.DOI) OR,
        2.   They are neither less than, nor greater than nor
             equal to each other (^((A < B) | (A > B) | (A =
             B))) OR,
        3.   Their compartment sets are disjoint from each
             other OR,
        4.   The releasability sets are disjoint from each other

        (^(((A.COMP & ^IGNOR) <= (B.COMP & ^IGNOR))  |
           ((A.COMP & ^IGNOR) => (B.COMP & ^IGNOR))  ))

6.2.  End System Processing

        This section describes SIPSO-related processing for IPv6 packets
   imported or exported from an End System claiming to implement or
   conform with this specification.  Nothing in this document applies
   to an IPv6 End System that does not claim to implement or conform
   with this specification.

6.2.1  Export

        An end system which sends data to the network is said to "export"
   it to the network.  Before a datagram can leave an end system and be
   transmitted over a network the following must occur:

        1. Selection of the export DOI:

        a)     If the system implements or permits only one
               DOI, that DOI is the export DOI.
        b) elseIf the Upper Level Protocol selects a DOI, that
               DOI is the one used.  Note that a TCP connection
               must have the same DOI and marking for the life
               of the connection - the DOI is selected at
               connection initiation and may not change.

        c) elseIf there are tables defining a specific default
               DOI for the specific destination end-system address or
               for the network address, then that DOI is
               selected.
        d) elseIf there is a specific DOI associated with the
           sending logical interface (i.e. IP address),
               then that DOI is selected.
        e)     Else the default DOI for the system is selected.

   NB: In the event the end-system selects and uses a specific DOI and that
   DOI is not recognised by the originating end-system's first-hop router,
   the packet MUST be dropped by the first-hop router.  In such a case,
   the networking API should indicate the connection failure (e.g. with some
   appropriate error, such as ENOTREACH).  This represents either incorrect
   configuration of either the intermediate-system or the end-system -- xor
   correct operation for a node that is not permitted to send IPv6 packets
   through that intermediate-system.

        2.  Export Marking:
             Once the DOI is selected, the SIPSO marking and
        values are determined based on the internal marking and
        the DOI.  In the event the internal marking does not
        map to a valid SIPSO marking, an error should be
        returned to the upper level protocol and MAY be logged.
        No further attempt to send this datagram should be
        made.

        3.  Access Control:
             Once the datagram is marked and the sending logical
        interface is selected (by the routing code), the
        marking of the datagram is compared against the
        range(s) associated with that logical interface.  For
        the datagram to be sent, the interface must list the
        DOI of the datagram marking as one of the permissible
        DOI's and the datagram marking must be within range for
        the range associated with that DOI.  If the datagram
        fails this access test an error should be returned to
        the upper level protocol and MAY be logged.  No further
        attempt to send this datagram should be made.

6.2.2.  Import

        When a datagram arrives at an interface on an end system,
   the end system MUST:

        1.   Verify the SIPSO checksum if it occurs within the
             option.  Datagrams with invalid checksums MUST be
             silently dropped.  They SHOULD be logged.
        2.   Verify the SIPSO has a known and valid DOI.
             Datagrams with unrecognized or illegal DOIs MUST
             be silently dropped.  Such an event SHOULD be
             logged as a security fault.
        3.   Verify the DOI is a permitted one for the receiving
             interface.  Datagrams with prohibited or unknown DOIs
             MUST be silently dropped.  Such an event SHOULD
             be logged as a security fault.
        4.   Verify the marking within the SIPSO is within the
             permitted range for the receiving interface.  N.B.
             EACH permitted DOI on an interface has a separate
             table describing the permitted range for that DOI:

             A datagram which has a marking within the permitted
             range is accepted for further processing.

             A datagram which has a marking disjoint with the
             permitted range MUST be silently discarded.  This
             event SHOULD be logged as a security fault, with an
             indication that the packet was discarded because
             of a disjoint marking.

             A datagram which has a marking below the permitted
             range MUST be dropped.  This event SHOULD be logged.
             It MAY result in an appropriate ICMP error message sent
             at the maximum permitted sensitivity label for the interface
             for that DOI, depending on the security configuration.
             The choice of whether or not to send an ICMP message
             MUST be configurable and SHOULD default to OFF.  Standard
             non-MLS conditions about generating ICMP error messages
             (e.g. no error message about a received error message)
             continue to apply.

             A datagram with a marking above the permitted range
             MUST be discarded.  This event SHOULD be logged.  It
             MAY result in an appropriate ICMP error message sent
             at the maximum permitted marking for the interface
             for that DOI, depending on security configuration.
             The choice of whether or not to send an ICMP message
             MUST be configurable, and SHOULD default to OFF.
             Standard conditions about generating ICMP error messages
             (e.g. "generate no error message about an error message")
             continue to apply.

        5.   Once the datagram has been accepted, the import sensitivity
             label and DOI are used to associate the appropriate internal
             marking with the data contained in the datagram
             This information MUST be carried as part of the information
             returned to the upper level protocol.

6.3.  Intermediate System Rules

        This section describes SIPSO-related processing for IPv6 packets
   transiting an IPv6 intermediate-system that claims to implement and
   comply with this specification.  Nothing in this document applies
   to an IPv6 intermediate-system that does not claim to comply
   with this specification.

        The SIPSO packet format has been designed so that one can configure
   an intermediate system with the minimum sensitivity level, maximum
   sensitivity level, minimum compartment bitmap, maximum compartment
   bitmap, minimum releasability, and maximum releasability -- and then
   deploy that system without forcing it to know the detailed meaning
   of each sensitivity level, compartment bit, or releasability bit.
   Instead, once the minimum and maximum labels have been configured,
   the intermediate system can apply a simple algorithm to determine
   whether or not a packet is within range for a given interface.

6.3.1.  Input

        Intermediate Systems (ISs) have slightly different rules for
   processing marked datagrams than do end systems.  Primarily, ISs
   do not IMPORT or EXPORT transit datagrams, they just route them.
   Also, in most deployments intermediate systems are used to provide
   Mandatory Access Controls to packets traversing more than one
   subnetwork.

        The following checks MUST occur before any other processing.
   Upon receiving a SIPSO-labeled packet, an intermediate system must:

        1.   Determine whether or not this datagram is destined
             for (addressed to) this IS.  If so, the IS becomes
             an end-system for the purposes of receiving this datagram
             and the rules for IMPORTing described above are
             followed.
        2.   Verify the SIPSO checksum.  Datagrams with invalid checksums
             MUST be silently dropped.  The drop event SHOULD be logged
             as a network fault.
        3.   Verify the SIPSO has a known and valid DOI.
             Datagrams with unrecognized or illegal DOIs MUST
             be silently dropped.  They SHOULD be logged as a security fault.
        4.   Verify the DOI is a permitted one for the receiving interface
             Datagrams with prohibited DOIs MUST be silently dropped.
             Such drops SHOULD be logged as a security fault.
        5.   Verify the marking within the SIPSO is within the
             permitted range for the receiving interface.

             N.B.:  EACH permitted DOI on an interface has a separate
             table describing the permitted range for that DOI:

             A rejected datagram which has a marking below or disjoint
             with the permitted range MUST be silently dropped.
             Such an event SHOULD be logged as a security fault,
             including details about the fault.

             A rejected datagram with a marking above the permitted
             range MUST be dropped.  The drop event SHOULD be logged
             as a security fault.  It MAY result in an appropriate ICMP
             error message sent at the maximum permitted marking for
             the interface for that DOI, depending on the system's
             security configuration..  The choice of whether or not
             to send an ICMP message, if implemented, MUST be configurable,
             and SHOULD default to OFF.

             Standard Internet conditions about generating ICMP error
             messages (e.g. never generate an error message about a
             received error message) continue to apply.

        If and only if all the above conditions are met is the datagram
   accepted by the IPv6 intermediate-system for further processing and
   forwarding.

        At this point, the datagram is within the permitted range for the IS,
   and appropriate ICMP error messages may be generated by the IP module back
   to the originating end-system regarding the forwarding of the datagram.
   These ICMP messages MUST be sent with the exact same marking as the
   datagram causing the error.  Note that these generated messages must go
   through the same outbound checks as a forwarded datagram as described in
   the following paragraphs.

6.3.2.  Translation

        It is at this point that TRANSLATION of the SIPSO takes place
   if at all.  Please see the following section for a discussion
   of the appropriate processing.

6.3.3.  Output

        Once the forwarding code has selected the interface through
   which the datagram will be transmitted the following takes place:

             Verify the DOI is a permitted one for the sending
        interface and that the datagram is within the permitted
        range for the DOI and for the interface.

          Datagrams with prohibited DOIs or with out of range
        values MUST be dropped.  Drop events SHOULD be logged
        as a security fault.

          Datagrams with prohibited DOIs or out of range values MAY
        result in an appropriate ICMP error message, depending upon
        the security configuration of the system.  If an ICMP Error
        Message is sent, it must be sent with the same sensitivity
        Label as the rejected datagram  The choice of whether or not
        to send an ICMP message, if implemented, MUST be configurable,
        and SHOULD default to OFF.  Standard conditions about generating
        ICMP error messages (e.g. never send an error message about
        a received error message) apply.

6.4.  Translation

        A system which provides on-the-fly re-marking is said to "translate"
   from one DOI to another.  There are basically two ways a datagram can be
   relabeled; either the sensitivity label can be converted from an external
   (SIPSO) sensitivity label, to an internal sensitivity label and then back
   to a new external sensitivity label, or an external sensitivity label can
   be directly remapped into another external sensitivity label.

           The first of these methods is the functional equivalent of
   "importing" the datagram then "exporting" it and is covered in detail
   in the "Import" and "Export" sections above.  This section describes
   direct relabeling.  The choice of which method to use for relabeling
   is an implementation decision outside the scope of this document.

           A system which provides on-the-fly relabeling without importing
   or exporting is basically a special case of the Intermediate System rules
   listed above.  Translation or relabeling takes place AFTER all input checks
   take place, but before any output checks are done.

           Once a datagram has been accepted (passing all the appropriate
   checks described in section 5.3), it may be relabeled.  To determine the
   new sensitivity label, first determine the new DOI.  The selection of the
   new DOI may be based on any of DESTINATION END-SYSTEM, DESTINATION NETWORK,
   DESTINATION SUBNET, SENDING INTERFACE, or RECEIVING INTERFACE or
   combinations thereof.  Exact details on how the output DOI is selected are
   implementation dependent, with the caveat that it should be consistent and
   reversible.  If a datagram from end-system A to end-system B with DOI X
   maps into DOI Y, then a datagram from B to A with DOI Y should map into DOI
   X.

           Once the output DOI is selected, the output sensitivity label is
   determined based on (1) the input sensitivity label and input DOI and (2)
   the output DOI.  In the event the input sensitivity label does not map
   to a valid output sensitivity label for that DOI, the datagram MUST be
   silently dropped and the drop event SHOULD be logged as a security fault.

           Once the datagram is remarked, the output procedures under section
   5.3 "Intermediate Systems" are followed with the exception that any error
   that would cause a ICMP error message to be generated back to the
   originating end-system instead MUST drop the datagram.  Such a drop
   SHOULD be logged as a security fault.

7.  IMPLEMENTATION ISSUES AND HINTS

        The following are "hints" not "requirements".  Implementation
   experience could eventually turn some of them into implementation
   requirements.

7.1.  Intermediate Systems

           Performance is optimised if there is hardware support for applying
   the mandatory access controls based on this label option.

7.2.  End Systems

           It is possible to create two DoIs with different overlapping
   compartment ranges.  This can be used to reduce the size of the IPv6
   sensitivity label option in some deployments.

7.3.  Upper-Level Protocols

7.3.1.  TCP-related issues

        With respect to an internet, each distinct sensitivity label
   represents a separate virtual internet which shares the same physical
   internet.

        The above statement taken from section 3 has a non-obvious but
   critical corollary.  If there are separate virtual internets then it is
   possible for a system which exists in multiple virtual internets to have
   identical TCP connections, each one existing in a different virtual
   internet.

        TCP connections are normally identified by source and destination
   port, and source and destination address.  If a system marks datagrams
   (which it must do if it exists in multiple virtual internets - e.g. a
   "multi-level secure" system), then TCP connections are identified by source
   and destination port, source and destination address and SIPSO Security
   Marking.

7.3.2.  UDP-related Issues

        Datagrams addressed to a UDP port should be delivered to all listeners
   whose equivalent sensitivity label is greater than or equal to the security
   marking of the UDP datagram.

7.3.3.  SCTP-related Issues

           Although a node might be multi-homed, it is entirely possible that
   only one of those interfaces is reachable for a given sensitivity label
   value.  For example, one interface on a node might have a sensitivity label
   range of Secret:Top Secret while a different interface might have a
   sensitivity label range of Unclassified:Unclassified.

SECURITY CONSIDERATIONS

        This document describes a mechanism for adding explicit sensitivity
   labels to IPv6 datagrams.  The primary purpose of these labels is to
   facilitate application of Mandatory Access Controls (MAC) in end-systems
   or intermediate-systems that implement this specification.  As such, the
   implementation of this mechanism is very critical to overall security of
   the systems and networks where this mechanisms is deployed.  Use of
   high-assurance development techniques is appropriate for this
   specification.

        A concern is that since this label is used for mandatory access
   controls, some method of binding the sensitivity label option to the rest
   of the packet is needed.  Without such binding, malicious modification of
   the sensitivity label in a packet would go undetected.  So, implementations
   of this sensitivity label option MUST also implement support for the IP
   Authentication Header.  Implementations MUST permit the system
   administrator to configure whether AH is used or not.

        This mechanism is only intended for deployment in very limited
   circumstances where a set of systems and networks are in a well-protected
   operating environment and the threat of external or internal attack on this
   mechanism is considered acceptable to the accreditor of those systems and
   networks.  Accreditors of a given deployment should consider not only
   personnel clearances and physical security issues, but also electronic
   security (e.g.  TEMPEST), network security, and communications security
   (COMSEC) issues.

IANA CONSIDERATIONS

        IANA is requested to assign an IPv6 Hop-by-Hop option number to the
   SIPSO option described in this specification.  This option is immutable
   during transit.

   Also, IANA is requested to create a registry for SIPSO DOI values.
   The initial values for this registry, shown in dotted-quad format,
   are as follows:

      DOI Value                  Organisation or Use
      0.0.0.0                      Null DOI 2013 must not be used on the network
      0.0.0.1 to 0.255.255.255     For private use among consenting parties


        For the SIPSO DOI values registry, IANA is requested to issue a new
   DoI value to any organisation that requests it.  Assignment information
   should be made available on the IANA website.  A commercial organisation
   will normally only be assigned one or two DoI values.  A government or
   multi-national treaty organisation may be assigned a range of values
   if that is requested.  Different departments within a given government
   each may independently request a range of values.

ACKNOWLEDGEMENTS
   This document is directly derived from an Internet-Draft by the first
   author written circa 1992.  Packet format changes have been made since
   that draft, primarily to comply with IPv6 syntax rules.

INFORMATIVE REFERENCES

      [BL73]         Bell, D.E. & LaPadula, L.J., "Secure Computer Systems:
                     Mathematical Foundations and Model", Technical Report
                     M74-244, The MITRE Corporation, Bedford, MA, May 1973.

      [CMW]          US Defense Intelligence Agency, "Compartmented Mode
                     Workstation Evaluation Criteria", Technical Report
                     DDS-2600-6243-91, Washington, DC.

      [DOD 5200.1]   US Department of Defense, "DoD Information Security
                     Program", Directive 5200.1, 13 December 1996.

      [DOD 5200.1-R] US Department of Defense, "Information Security Program
                     Regulation", DoD 5200.1-R, 17 January 1997.

      [DoD 5200.28]  US Department of Defense, "Security Requirements
                     for Automated Information Systems," Directive 5200.28,
                     21 March 1988.

      [DoD MLOS PP]  US Department of Defense, "Protection Profile
                     for Multi-level Operating Systems in Environments
                     requiring Medium Robustness, Version 1.22, 23 May
                     2001

      [ISO-15408]    International Stanards Organisation, "Evaluation
                     Criteria for IT Security", ISO/IEC 15408, 2005.

      [CC]           "Common Criteria for Information Technology Security
                     Evaluation", Version 3.1, Revision 1, CCMB-2006-09-001,
                     September 2006.

      [TCSEC]        US Department of Defense, "Trusted Computer System
                     Evaluation Criteria", DoD 5200.28-STD, 26 December 1985.

      [DoD 8500.1]   US Department of Defense, "Information Assurance",
                     Directive 8500.1, 24 October 2002.

      [FIPS-188]     US National Institute of Standards & Technology,
                     "Standard Security Labels for Information Transfer",
                     Federal Information Processing Standard (FIPS) 188,
                     September 1994.

      [RFC-791]      J. Postel, Internet Protocol, RFC-791, September 1981.

      [RFC-1038]     M. StJohns, Draft Revised IP Security Option, RFC-1038,
                     January 1988.

      [RFC-1108]     S. Kent, US DoD Security Options for the Internet
                     Protocol, RFC-1108, November 1991.

      [RFC-1825]     R. Atkinson, Security Architecture for the Internet
                     Protocol, RFC-1825, August 1995.

      [IPSEC]       S. Kent, "Security Architecture for the Internet
                    Protocol", RFC-xxx, date TBD.

      [AH]          S. Kent, "IP Authentication header", RFC-yyyy, date TBD.

      [ESP]         S. Kent, "IP Encapsulating Security Payload", RFC-zzzz,
                    date TBD.

NORMATIVE REFERENCES

      [RFC-2460]     S. Deering & R. Hinden, Internet Protocol Version 6
                     Specification, RFC-2460, December 1998.

AUTHORS:

   M. StJohns
   Nominum
   2385 Bay Road
   Redwood City, CA
   USA 94063-3011
   mstjohns@nominum.com

   R. Atkinson
   Extreme Networks
   3585 Monroe Street
   Santa Clara, CA
   USA 95051
   rja@extremenetworks.com

   G. Thomas
   US Department of Defense
   Washington, DC
   USA

COPYRIGHT

   Copyright (C) The IETF Trust (2007).

   This document is subject to the rights, licenses and restrictions contained
   in BCP 78, and except as set forth therein, the authors retain all their
   rights.

   This document and the information contained herein are provided on an "AS
   IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS
   SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE
   INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
   INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES
   OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.


Html markup produced by rfcmarkup 1.107, available from http://tools.ietf.org/tools/rfcmarkup/