rfc1667.txt

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   In some cases, the M&S exercises will involve the transmission of
   classified data over the network. For example, messages may contain
   sensitive data regarding warfare tactics and weapons systems
   characteristics, or an exercise itself may be a rehearsal of an
   imminent military operation. This means the data communications used
   for these exercises must meet security constraints defined by the
   National Security Agency (NSA).  Some such requirements can be met in
   current systems by use of end-to-end packet encryption (E3) systems.
   E3 systems provide adequate protection from disclosure and tampering,
   while allowing multiple security partitions to use the same network
   simultaneously.

   Currently the M&S community is using the experimental Internet Stream
   protocol version 2 (ST2) to provide resource reservation and
   multicast.  There is much interest in converting to IPv4 multicast as
   it becomes available across the COTS base, but this cannot happen
   until IPv4 has a resource reservation capability.  The RSVP work
   ongoing in the IETF is being watched in expectation that it will
   provide such a capability.  Also some tests have been made of IPv4
   multicast without resource reservation; results have been positive,
   now larger tests are required to confirm the expected scalability of
   IPv4 multicast.  But issues remain: for security reasons, some M&S
   exercises will require sender-initiated joining of members to



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RFC 1667     Modeling and Simulation Requirements for IPng   August 1994


   multicast groups. In addition, it is not clear that IPv4 multicast
   will be able to make use of link-layer multicast available in ATM
   systems, which the M&S community expects to use to achieve the
   performance necessary for large exercises.

3.  M&S Requirements for IPng

   The identified network-layer service requirements for M&S
   applications are set forth below in three major categories: real-time
   response, multicast capability, and resource reservation capability.
   All of these capabilities are considered to be absolute requirements
   for supporting DIS as currently understood by the M&S community,
   except those specifically identified as highly desirable.  By
   desirable we mean that the capabilities are not essential, but they
   will enable more direct or cost-effective networking solutions.

   It is recognized that some of the capabilities described below may be
   provided not from IPng but from companion protocols, e.g. RSVP and
   IGMP.  The M&S requirement is for a compatible suite of protocols
   that are available in commercial products.

   a.  Real-time Response

      DIS will continue to have requirements to communicate real-time
      data, therefore the extent to which IPng lends itself to
      implementing real-time networks will be a measure of its utility
      for M&S networking.  The system-level specifications for the DIS
      real-time environment are stated in Section 2 above.

   b.  Multicasting

      M&S requires a multicasting capability and a capability for
      managing multicast group membership.  These multicasting
      capabilities must meet the following requirements:

      - Scalable to hundreds of sites and, potentially, to tens of
        thousands of simulation platforms.

      - It is highly desirable that the network-layer multicasting
        protocol be able to use the multicasting capabilities of
        link-level technologies, such as broadcast LANs, Frame Relay,
        and ATM.

      - The group management mechanics must have the characteristics
        that thousands of multicast groups consisting of tens of
        thousands of members each can be supported on a given network
        and that a host should be able to belong to hundreds of multicast
        groups simultaneously.



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RFC 1667     Modeling and Simulation Requirements for IPng   August 1994


      - Multicast group members must be able to be added to or removed
        from groups dynamically, in less than one second, at rates of
        hundreds of membership changes per second.  It is not possible
        to predict what special cases may develop, thus this requirement
        is for all members of all groups.

      - The network layer must support options for both sender- and
        receiver-initiated joining of multicast groups.

   c.  Resource Reservation

      The M&S community requires performance guarantees in supporting
      networks. This implies that IPng must be compatible with a
      capability to reserve bandwidth and other necessary allocations in
      a multicast environment, in order to guarantee network capacity
      from simulator-to-simulator across a shared network for the
      duration of the user's interaction with the network. Such a
      resource reservation capability is essential to optimizing the use
      of limited network resources, increasing reliability, and
      decreasing delay and delay variance of priority traffic,
      especially in cases in which network resources are heavily used.
      The resource reservations should be accomplished in such a way
      that traffic without performance guarantees will be re-routed,
      dropped, or blocked before reserved bandwidth traffic is affected.

      In addition, it would be highly desirable for the resource
      reservation capability to provide mechanisms for:

      - Invoking additional network resources (on-demand capacity)
        when needed.

      - The network to feed back its loading status to the applications
        to enable graceful degradation of performance.

4.  References

   [1] Cohen, D., "DSI Requirements", December 13, 1993.

   [2] Final Draft Communication Architecture for Distributed
       Interactive Simulation (CADIS), Institute for Simulation and
       Training, Orlando, Florida, June 28, 1993.

   [3] Miller, D., "Distributed Interactive Simulation Networking
       Issues", briefing presented to the ST/IP Peer Review Panel, MIT
       Lincoln Laboratory, December 15, 1993.

   [4] Pate, L., Curtis, K., and K. Shah, "Communication Service
       Requirements for the M&S Community", September 1992.



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RFC 1667     Modeling and Simulation Requirements for IPng   August 1994


   [5] Pullen, M., "Multicast Network Architecture for DIS, briefing
       presented to the Networks Infrastructure Task Force", George
       Mason University, C3I Center/Computer Science, November 10, 1993,
       revised November 11, 1993.

5.  Authors' Addresses

       Susan Symington
       MITRE Corporation
       7525 Colshire Drive
       McLean, VA 22101-3481

       Phone: [phone]
       EMail: [e-mail]


       David Wood
       MITRE Corporation
       7525 Colshire Drive
       McLean, VA 22101-3481

       Phone: [phone]
       EMail: [e-mail]


       J. Mark Pullen
       Computer Science
       George Mason University
       Fairfax, VA 22030

       Phone: [phone]
       EMail: [e-mail]



















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