rfc1070.txt

著名的RFC文档,其中有一些文档是已经翻译成中文的的.

Network Working Group                                          R. Hagens
Request for Comments:  1070                    U of Wiscsonsin - Madison
                                                                 N. Hall
                                               U of Wiscsonsin - Madison
                                                                 M. Rose
                                                    The Wollongong Group
                                                           February 1989


                Use of the Internet as a Subnetwork for
              Experimentation with the OSI Network Layer


Status of this Memo

   This RFC proposes a scenario for experimentation with the
   International Organization for Standardization (ISO) Open Systems
   Interconnection (OSI) network layer protocols over the Internet and
   requests discussion and suggestions for improvements to this
   scenario.  This RFC also proposes the creation of an experimental OSI
   internet.  To participate in the experimental OSI internet, a system
   must abide by the agreements set forth in this RFC.  Distribution of
   this memo is unlimited.

WARNING

   The methods proposed in this RFC are suitable ONLY for experimental
   use on a limited scale.  These methods are not suitable for use in an
   operational environment.

Introduction

   Since the International Organization for Standardization (ISO) Open
   Systems Interconnection (OSI) network layer protocols are in their
   infancy, both interest in their development and concern for their
   potential impact on internetworking are widespread.  This interest
   has grown substantially with the introduction of the US Government
   OSI Profile (GOSIP), which mandates, for the US Government, the use
   of OSI products in the near future.  The OSI network layer protocols
   have not yet received significant experimentation and testing.  The
   status of the protocols in the OSI network layer varies from ISO
   International Standard to "contribution" (not yet a Draft Proposal).
   We believe that thorough testing of the protocols and implementations
   of the protocols should take place concurrently with the progression
   of the protocols to ISO standards.  For this reason, the creation of
   an environment for experimentation with these protocols is timely.

   Thorough testing of network and transport layer protocols for



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RFC 1070                  Experimental OSI Net             February 1989


   internetworking requires a large, varied, and complex environment.
   While an implementor of the OSI protocols may of course test an
   implementation locally, few implementors have the resources to create
   a sufficiently large dynamic topology in which to test the protocols
   and implementations well.

   One way to create such an environment is to implement the OSI network
   layer protocols in the existing routers in an existing internetwork.
   This solution is likely to be disruptive due to the immature state of
   the OSI network layer protocols and implementations, coupled with the
   fact that a large set of routers would have to implement the OSI
   network layer in order to do realistic testing.

   This memo suggests a scenario that will make it easy for implementors
   to test with other implementors, exploiting the existing connectivity
   of the Internet without disturbing existing gateways.

   The method suggested is to treat the Internet as a subnetwork,
   hereinafter called the "IP subnet."  We do this by encapsulating OSI
   connectionless network layer protocol (ISO 8473) packets in IP
   datagrams, where IP refers to the Internet network layer protocol,
   RFC 791.  This encapsulation occurs only with packets travelling over
   the IP subnet to sites not reachable over a local area network.  The
   intent is for implementations to use OSI network layer protocols
   directly over links locally, and to use the IP subnet as a link only
   when necessary to reach a site that is separated from the source by
   an IP gateway.  While it is true that almost any system at a
   participating site may be reachable with IP, it is expected that
   experimenters will configure their systems so that a subset of their
   systems will consider themselves to be directly connected to the IP
   subnet for the purpose of testing the OSI network layer protocols or
   their implementations.  The proposed scheme permits systems to change
   their topological relationship to the IP subnet at any time, also to
   change their behavior as an end system (ES), intermediate system
   (IS), or both at any time.  This flexibility is necessary to test the
   dynamic adaptive properties of the routing exchange protocols.

   A variant of this scheme is proposed for implementors who do not have
   direct access to the IP layer in their systems.  This variation uses
   the User Datagram Protocol over IP (UDP/IP) as the subnetwork.

   In this memo we will call the experiment based on the IP subnet EON,
   an acronym for "Experimental OSI-based Network".  We will call the
   experiment based on the UDP/IP subnet EON-UDP.

   It is assumed that the reader is familiar with the OSI connectionless
   network layer and, in particular, with the following documents:




Hagens, Hall, & Rose                                            [Page 2]

RFC 1070                  Experimental OSI Net             February 1989


   RFC 768

      User Datagram Protocol.

   RFC 791

      Internet Protocol.

   ISO 8473

      Protocol for Providing the Connectionless mode Network Service.

   ISO DP 9542

      End System to Intermediate System Routing Exchange Protocol for
      Use in Conjunction with the Protocol for the Provision of the
      Connectionless-mode Network Service (ISO 8473).

   ISO TC 97/SC 6/N xxxx

      Intermediate System to Intermediate System Intra-Domain Routing
      Exchange Protocol.

   PD TR 97/SC 6/N 9575

      OSI Routing Framework.


Definitions

   EON

      An acronym for Experimental OSI Network, a name for the proposed
      experimental OSI-based internetwork that uses the IP over the
      Internet as a subnetwork.

   EON-UDP

      A name for the proposed experimental OSI-based internetwork that
      uses the UDP/IP over the Internet as a subnetwork.

   ES

      End system as defined by OSI: an OSI network layer entity that
      provides the OSI network layer service to a transport layer.






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RFC 1070                  Experimental OSI Net             February 1989


   IANA

      The Internet Assigned Numbers Authority.  Contact Joyce K.
      Reynolds ([e-mail]).

   IS

      An OSI network layer entity that provides the routing and
      forwarding functions of the OSI connectionless network layer.

   OSI CLNL

      OSI connectionless network layer.

   NSDU

      Network Service Data Unit.

   PDU

      Protocol Data Unit, or packet.

   NPDU

      Network Protocol Data Unit.

   ISO-gram

      An NPDU for any protocol in the OSI CLNL, including ISO 8473
      (CLNP), ISO DP 9542 (ES-IS), and ISO TC 97/SC 6/N xxxx (IS-IS).

   Participating system

      An ES or IS that is running a subset of the OSI CLNL protocols and
      is reachable through the application of these protocols and the
      agreements set forth in this memo.

   Core system

      An ES or IS that considers itself directly connected to the IP
      subnet for the purpose of participating in EON.

   NSAP-address

      Network Service Access Point address, or an address at which the
      OSI network services are available to a transport entity.





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RFC 1070                  Experimental OSI Net             February 1989


   SNPA-address

      SubNetwork Point of Attachment address, or an address at which the
      subnetwork service is available to the network entity.


Issues to be Addressed by this Memo

   In order to make the experimental OSI internet work, participating
   experimenters must agree upon:

   -    how ISO-grams will be encapsulated in IP or UDP packets,

   -    the format of NSAP-addresses to be used,

   -    how NSAP-addresses will be mapped to SNPA-addresses on
        the IP subnet,

   -    how multicasting, which is assumed by some OSI CLNL
        protocols, will be satisfied, and

   -    how topology information and host names will be
        disseminated.

   This memo contains proposals for each of these issues.

Design Considerations

   The goals of this memo are:

   -    to facilitate the testing of the OSI network layer
        protocols among different implementions,

   -    to do this as soon as possible, exploiting existing
        connectivity,

   -    to do this without requiring any changes to existing IP
        gateways,

   -    to create a logical topology that can be changed
        easily, for the purpose of testing the dynamic adaptive
        properties of the protocols, and

   -    to minimize the administrative requirements of this
        experimental internetwork.

   The following are not goals of this memo:




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RFC 1070                  Experimental OSI Net             February 1989


   -    to permit the use of arbitrary ISO-style
        NSAP-addresses,

   -    to require that participants have working
        implementations of all of the OSI routing protocols
        before they can participate in any capacity,

   -    to permit or encourage the use of existing IP routing
        methods and algorithms for the routing of ISO-grams
        among participating ESs and ISs,

   -    to create a production-like environment accommodating a
        very large number of systems (ESs, ISs or both), and

   -    to provide or to encourage IP-to-CLNP gatewaying.

Encapsulating ISO-grams in IP datagrams

   The entire OSI network layer PDU, whether it be an ISO 8473 PDU, an
   ISO DP 9542 PDU, or an IS-IS PDU, will be placed in the data portion
   of an IP datagrams at the source.  The ISO 8473 entity may fragment
   an NSDU into several NPDUs, in which case each NPDU will be
   encapsulated in an IP datagram.  The intent is for the OSI CLNL to
   fragment rather than to have IP fragment, for the purpose of testing
   the OSI CLNL.  Of course, there is no guarantee that fragmentation
   will not occur within the IP subnet, so reassembly must be supported
   at the IP level in the destination participating system.

   SNPA-addresses (Internet addresses) will be algorithmically derived
   from the NSAP-addresses as described below.  The "protocol" field of
   the IP datagram will take the value 80 (decimal), which has been
   assigned for this purpose.