rfc1609.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                                       G. Mansfield
Request for Comments: 1609                        AIC Systems Laboratory
Category: Experimental                                      T. Johannsen
                                                      Dresden University
                                                              M. Knopper
                                                    Merit Networks, Inc.
                                                              March 1994


                Charting Networks in the X.500 Directory

Status of this Memo

   This memo defines an Experimental Protocol for the Internet
   community.  This memo does not specify an Internet standard of any
   kind.  Discussion and suggestions for improvement are requested.
   Distribution of this memo is unlimited.

Abstract

   There is a need for a framework wherein the infrastructural and
   service related information about communication networks can be made
   accessible from all places and at all times in a reasonably efficient
   manner and with reasonable accuracy.  This document presents a model
   in which a communication network with all its related details and
   descriptions can be represented in the X.500 Directory. Schemas of
   objects and their attributes which may be used for this purpose are
   presented.  The model envisages physical objects and several logical
   abstractions of the physical objects.






















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RFC 1609        Charting Networks in the X.500 Directory      March 1994


Table of Contents

      1. Introduction                                       2
      2. Infrastructural information requirements           2
      3. The Nature of the Network Map - The X.500 Solution 4
      4. The hierarchical model of a network                5
      4.1 Network maps                                      5
      4.2 Representation in the X.500 Directory             6
      5. Position in The Directory Information Tree(DIT)    7
      6. Proposed Schemes                                   8
      6.1 Communication Object Classes                      9
      6.2 Physical elements                                10
      6.2.1 Network                                        10
      6.2.2 Node                                           11
      6.2.3 NetworkInterface                               12
      6.3 Logical Elements                                 12
      6.3.1 Network                                        13
      6.3.2 Node                                           13
      6.3.3 NetworkInterface                               13
      7. Security Considerations                           14
      8. Authors' Addresses                                14
      9. References                                        15

1. Introduction

   The rapid and widespread use of computer networking has highlighted
   the importance of holding and servicing information about the
   networking infrastructure itself.  The growing and active interest in
   network management, which has concentrated mainly in the areas of
   fault and performance management on a local scale, is severely
   constrained by the lack of any organized pool of information about
   the network infrastructure itself. Some attempts have been made, on a
   piecemeal basis, to provide a larger view of some particular aspect
   of the network (WHOIS, DNS, .. in the case of the Internet; [1],
   [2]).  But to date, little or no effort has been made in setting up
   the infrastructural framework, for such an information pool. In this
   work we explore the possibility of setting up a framework to hold and
   serve the infrastructural information of a network.

2. Infrastructural information requirements

   Network operation and management requires information about the
   structure of the network, the nodes, links and their properties.
   Further, with current networks extending literally beyond bounds, the
   scope of the information covers networks beyond the span of local
   domain of authority or administration.  When the Network was
   relatively small and simple the map was already known to the
   knowledgable network administrator.  Based on this knowledge the



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RFC 1609        Charting Networks in the X.500 Directory      March 1994


   course of the packets to different destinations would be charted. But
   presently the size of the Network is already beyond such usages. The
   current growth of the Network is near explosive. This is giving rise
   to the urgent necessity of having infrastructural and service related
   information made accessible from all places and at all times in a
   reasonably efficient manner and with reasonable accuracy. In the rest
   of this work a network is the media for transmitting information.
   Network elements are equipment with one or more network interfaces
   whereby it is possible to exchange information with the network.
   Network elements with multiple interfaces e.g.,
   gateways/routers/bridges/repeaters...  may be used to connect
   networks.  Network related information, referred to as 'network map'
   in the rest of this paper, should

   1. Show the interconnection between the various network
      elements. This will basically represent the Network as a graph
      where vertices represent objects like gateways/workstations/
      subnetworks and edges indicate the connections.

   2. Show properties and functions of the various network elements
      and the interconnections. Attributes of vertices will represent
      various properties of the objects e.g., speed, charge, protocol, OS,
      etc. Functions include services offered by a network element.

   3. Contain various name and address information of the networks
      and network elements

   4. Contain information about various administrative and management
      details related to the networks and network elements.

   5. Contain the policy related information, part of which may be
      private while the other part may be made public.

   Using this map the following services may be provided

   1. Configuration management:

      - Display the physical configuration of a network,
        i.e., nodes and their physical interconnections
      - Display the logical configuration of a network,
        i.e., nodes and their logical interconnections.

   2. Route management:

      - Find alternate routes by referring to the physical
        and logical configurations.
      - Generate routing tables considering local policy and
        policy of transit domains



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RFC 1609        Charting Networks in the X.500 Directory      March 1994


      - Check routing tables for routing loops,
        non-optimality, incorrect paths, etc.

   3. Fault management: In case of network failures
      alternatives may be found and used to bypass the
      problem node or link.

   4. Service management: Locate various services and
      servers in the Network.

   5. Optimization: The information available can be used
      to carry out various optimizations, for example cost,
      traffic, response-time, etc.

   6. Provide mappings between the various names and
      addresses of elements

   7. Depict administrative/autonomous domains.

   8. Network Administration and Management: References to
      people responsible for administering and technically
      maintaining a network will be useful.

   Examples of such usages are described in [3], [4].

3. The Nature of the Network Map - The X.500 solution

   Implementing and maintaining a detailed map of the network poses a
   serious problem.  The scope of the map is global and the network
   itself is expanding.  Some of the problems that are peculiar to the
   network map are listed below.

   o The Network configuration is quasi-static. Nodes,
     links and networks are being added,updated and deleted
     someplace or the other.

   o The Network is huge and geographically distributed.

   o The network spans several political and administrative
     areas. The related information is also controlled and
     maintained in a distributed fashion.

   In short, global network configuration information is unwieldy and
   growing continuously.  It is impossible to service such information
   in a centralized fashion. There is need for a distributed framework
   which allows users and applications to access information about
   users, services, networks, ... easily and globally.  The OSI X.500
   Directory services [5] provides a rich framework to support a



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RFC 1609        Charting Networks in the X.500 Directory      March 1994


   globally distributed information service system.  The X.500 Directory
   is intended to be a very large and highly distributed database. It is
   structured hierarchically with entries arranged in the form of a tree
   in which each object corresponds to a node or an entry. Information
   is stored about an object as a set of attributes.

4. The hierarchical model of a network

   For representing networks in the Directory we use the following
   hierarchical model.

   A network is the media for transmitting information with zero or more
   network elements each having at least one network interface on the
   media. The media may be any kind of a line (physical circuit/virtual
   circuit), or a collection of interconnected networks.

       <  The postscript version of this document  >
       <  has a figure here. However, the figure   >
       <is too complex to be drawn in simple ASCII.>

 Figure 1:  Simple and composite networks and their mapping to the DIT.

   The model allows hierarchy of subnetworks.  Network elements with
   multiple interfaces may act as external gateways to the attached
   network and to networks higher up in the hierarchy.  Thus, a gateway
   may be the external gateway of several networks which are either
   interconnected or have a hierarchical relationship.

   A network may be simple consisting of zero or more network elements
   or composite consisting of several sub-networks.  Examples of simple
   networks are ethernets, optical fiber/copper cables, free space, .. .

4.1 Network Maps

   Using the above model it is straight forward to draw the topological
   graph of the network where the vertices represent the components of
   the network and edges indicate the connections.  For visual
   representation the graph may be translated to a more "physical"
   illustration (figure 1).

   Just as there are several maps of the same geographical domain
   (political, natural...)  one can envisage several views of the same
   network and its components. A view (called "image" in the remainder)
   could pertain to a particular protocol suite (IP/OSI/...), an
   administrative domain or purpose.  Using images, several abstractions
   of the same object are possible.





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RFC 1609        Charting Networks in the X.500 Directory      March 1994


4.2 Representation in the X.500 Directory

   To represent the various images of networks and its components along
   with the real-image relationship among the various objects we
   introduce the following classes of objects:

   o Communication Object Class (CO): All objects defined
     furtheron in this document belong to this class.
     Common attributes for all communication objects are
     defined in section 6.

   o Physical Communication Object Class (PCO): A subclass
     of CO-class, this class defines common properties for
     all objects representing physical communication objects.

   o Image Communication Object Class (ICO): A subclass of
     CO-class, this class defines common properties for all
     objects representing images of communication objects.

   The above classes sort communication objects into physical or image
   object.  As is implied in the nomenclature a physical object will
   have several attributes describing it physical properties - location,
   weight, size, ....  etc.  An image object will have an Image-of
   attribute. The Image-of attribute will point to a physical object or
   to another image object.

   Using this schema it is possible to represent the case of several
   logical network systems (running different protocol stacks - IP, XNS,
   SNA, OSI, ...) which coexist on the same physical network.
   Information related to different types of networks, no matter what
   the underlying communication protocol is, will reside in the
   Directory in harmony.  Also, their interrelation will be represented
   and accessed in a fashion independent of the source/destination
   network, namely, using the OSI X.500 protocol.

   Schemes for physical networks and logical images of physical networks
   are defined in section 6.

   All objects are defined in section 6.












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RFC 1609        Charting Networks in the X.500 Directory      March 1994


                                              ...............
                                             :              :
                                             :   IP    OSI  :
                                             :  +-+    +-+  :
                                             :  |A|    |B|  :
                             NetWork  -----> :  +-+    +-+  :
                             /    \          :   |      |   :
                            /      \         : ============ :
                           /        \        :      |       :
                          /          \       :     +-+      :
                         /            \      :     |C|      :
                        /              \     :     +-+      :
                   OSI-image        IP-image :   IP + OSI   :
                       |                |    +..............+
                       V                V
                     ........       ........
                     :      :      :       :
                 IP  : OSI  :      :   IP  : OSI
                +-+  : +-+  :      :  +-+  : +-+
                |A|  : |B|  :      :  |A|  : |B|
                +-+  : +-+  :      :  +-+  : +-+
             ....|...:  |   :      :   |   :..|...
             : ============ :      : ============ :
             :      |       :      :      |       :
             :     +-+      :      :     +-+      :
             :     |C|      :      :     |C|      :
             :     +-+      :      :     +-+      :
             :   IP + OSI   :      :   IP + OSI   :
             +..............+      +..............+


      Figure 2: Several logical views of the same physical network

5. Position in the Directory Information Tree (DIT)

   Information about networks usually will be contained in the DIT as
   subordinate of the organization maintaining the network. The network
   model gets mapped into a tree structure for network elements.  There
   is one network object giving general descriptions of the network.
   Subordinates of this network object are node objects for each node
   element present in the network.  Node objects hold networkInterface
   objects as subordinates.  A network can be physically or logically
   subdivided into several (sub)networks.  In this case, a network entry
   will have network objects as subordinates which again build the same
   structure.  These entries may be kept as subordinates of
   organizationalUnit entries as well, with pointers from the "root"
   network.




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RFC 1609        Charting Networks in the X.500 Directory      March 1994


   This structure holds for physical and logical elements.  Physical
   elements are named network, node and networkInterface, and logical
   elements are named networkImage, nodeImage and networkInterfaceImage.

                          _root_
                         /      \
                        /        \
                       /          \
                  country          \
                     /              \
                    /            organization
                   /             /    |     \
                  /             /     |      \
                 /             /      |       \
                /             /       |        \
               /  organizationalUnit* |         \
              /   /             \ \   |          \
             /   /               \ \__|_________  \
            /   /                 \   |         \  \
           Person                 Network*<====>NetworkImage*
                                      |             |
                                      |             |
                                     Node      NodeImage
                                      |             |