Network Working Group G. Mansfield

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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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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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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- 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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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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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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...............
: :
: 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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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
| |
| |
NetworkInterface NetworkInterfaceImage

Legends: * the object may recursively contain objects of
same class as children

Figure 3: Part of the Directory Information Tree,
showing relations of White Pages and network objects

6. Proposed Schemes

A physical network comprises of wires and machines. The physical map
of the network will show the interconnections of these nodes by these
circuits.

For each physical network element, one or more images may exist.
Similarly, an image may be attached to one or more physical objects.
The types of images can grow along with the requirements.
Relationship between elements (physical or logical) are expressed by
attributes or the position in the Directory tree.

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Problems that are addressed in the schema:

1. Avoiding data duplication
2. Preserving administrative boundaries/controls.
3. Simple representation (minimal number of pointers)
4. Security: Though no special emphasis has been placed
in this work we believe the X.500 access control policies
policies will provide a reasonable secure framework for security
and privacy.

Problems that are not addressed:

1. Caching policies, etc.: to be decided locally

6.1 Communication Object Classes

The object classes introduced in section 4 are defined as follows:

CommunicationObject OBJECT CLASS
SUBCLASS of top
MAY CONTAIN {
description :: CaseIgnoreStringSyntax,
/* can contain any information about the object,
however, wherever an appropriate attribute
exists, this should be used first to hold
information */
adminContact :: distinguishedNameSyntax,
/* points to the person which is responsible for
the administration of the instance this object
describes;
This refers to the instance only in the context
of the concrete object class */
technContact :: distinguishedNameSyntax,
/* points to the person which is responsible for
the technical maintenance of the instance this
object describes;
This refers to the instance only in the context
of the concrete object class;
Availability (e.g. hours of service) is not
covered by this attribute. */
}

PhysicalCommunicationObject OBJECT CLASS
SUBCLASS of CommunicationObject
MAY CONTAIN{
owner :: distinguishedNameSyntax,
/* refers to organization or person owning the
physical element;

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Note that more detailed information (like lease,
rental, etc.) can be covered in a specific image
(ownerImage) of this element */
localityName :: CaseIgnoreStringSyntax
/* where the object is located;
can be used freely to "spot" a network element,
e.g. state/city/street/building/floor/room/
desk/... */
ICO :: distinguishedNameSyntax
/* points to image object the physical object
is related to;
might have several values if physical object is
used for several applications at the same time */
}

ImageCommunicationObject OBJECT CLASS
SUBCLASS of CommunicationObject
MAY CONTAIN{
type :: caseIgnoreStringSyntax,
/* expresses the view this object refers to, e.g.
view of provider/user/IP/OSI/...;
Note that this information can be covered by
the object class in some cases
(e.g. ipNetworkImage gives the IP view) */
imageOf :: distinguishedNameSyntax,
/* points to physical/image object the image
is related to;
might have several values if view applies to
several physical objects at the same time */
}

6.2 Physical elements

The following objects describe network elements without saying
anything about their usage. All objects inherit properties of the
PhysicalCommunicationObject class.

6.2.1 Network

The network object supplies general descriptions which are common for
a set of nodes and circuits comprising one network. This includes
information about the type of circuits (medium, broadcast or point-
to- point, etc.) and properties (speed etc.).

network OBJECT CLASS
SUBCLASS of PhysicalCommunicationObject
MUST CONTAIN {
networkName :: caseIgnoreStringSyntax }

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MAY CONTAIN {
externalGateway :: distinguishedNameSyntax,
/* points to one or more nodes that connect
this network to neighbor networks;
whether a node actually is used as gateway
for one or the other protocol, is defined
in a related networkImageObject */
nwType :: caseIgnoreStringSyntax,
/* type of this network;
either "composite" (if consisting of subnetworks)
or type of a line:
bus, ring, star, mesh, point-to-point */
media :: caseIgnoreStringSyntax,
/* if network is not composite,
describes physical media:
copper, fiber optic, etc. */
speed :: numericStringSyntax,
/* nominal bandwidth, e.g. 64 kbps */
traffic :: numericStringSyntax
/* (average) use in percent of nominal bandwidth
[ this needs more specification later ] */
configurationDate :: uTCTimeSyntax,
/* date when network was configured in current
shape */
configurationHistory :: caseIgnoreStringSyntax
/* list of configuration changes, like:
added/removed nodes, lines */
}

6.2.2 Node

The node object describes any kind of device that is part of the
network, such as simple nodes, printer, bridges.

node OBJECT CLASS
SUBCLASS of PhysicalCommunicationObject
MUST CONTAIN{
nodeName :: caseIgnoreStringSyntax }
MAY CONTAIN {
machineType :: caseIgnoreStringSyntax,
/* e.g. main frame, work station, PC, printer;
might include manufacturer */
OS :: caseIgnoreStringSyntax,
/* e.g. VM, UNIX, DOS; might include release */
}

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6.2.3 NetworkInterface

Each node object will have one or more networkInterface objects as
subordinates. NetworkInterface objects provide information about
interfaces of the node and connectivity.

networkInterface OBJECT CLASS
SUBCLASS of PhysicalCommunicationObject
MUST CONTAIN {
networkInterfaceName :: caseIgnoreStringSyntax
/* It is suggested that the networkInterface
name is derived from the name of the logical
device this networkInterface represents for
the operating system, e.g. le0, COM1 */
}
MAY CONTAIN {
networkInterfaceAddress :: caseIgnoreStringSyntax,
/* this should contain a protocol-independent
interface address, e.g. Ethernet board number */
connectedNetwork :: distinguishedNameSyntax,
/* pointer to object of network which this networkInterface is
connected to */
}

6.3 Logical Elements

An abstract view of a physical element is called image in this
document. The word image gets appended to the object type, leading
to the new objects networkImage, nodeImage and networkInterfaceImage.
Images will either build Directory trees of themselves or be stored
as part of the physical network tree (see section 5).

Image objects inherit properties of the ImageCommunicationObject
class.

Each image object has specific attributes which vary depending on the
point of view (IP, OSI, ...). Also, the user and provider of an image
will view an object differently; further a user of an object may also
be providing the services of the same object to another user.

Therefore, in the following a complete and general list of attributes
cannot be given. We recommend to define subclasses of Image classes
for each logical view. These subclasses inherit all attributes
defined with the object classes below and add more specific
attributes. Examples for an IP-view are given in [1].

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6.3.1 Network

There may be several network images for one and the same physical
network: one for each protocol, application, etc.

networkImage OBJECT CLASS
SUBCLASS of ImageCommunicationObject
MAY CONTAIN {
externalGateway :: distinguishedNameSyntax,
/* points to one or more nodes that act
as gateway for the protocol application
this images refers to */
speed :: numericStringSyntax,
/* nominal bandwidth for the channel dedicated
to this protocol or application ,
e.g. 64 kbps */
traffic :: numericStringSyntax,
/* (average) use in percent of nominal bandwidth
[this needs more specification later ] */
charge :: numericStringSyntax
/* amount of money that has to be paid to
service provider for usage;
[it is felt that this needs further definition:
e.g. monetary unit / time unit, monetary unit /
data unit ] */
}

6.3.2 Node

Name and functionality within the network might vary for a node from
protocol to protocol considered. In particular, a node might act as
gateway for one protocol but not for the other. Routing policy is
stored in the case of policy gateways.

nodeImage OBJECT CLASS
SUBCLASS of ImageCommunicationObject
/* no attributes common for all nodeImages have been
defined yet */

6.3.3 NetworkInterface

As with physical nodes, nodeImages have networkInterfaces
(networkInterfaceImages) which describe connectivity to other network
elements. NetworkInterfaceImages are only given if the protocol is
establishing connections via this networkInterface.

networkInterfaceImage OBJECT CLASS
SUBCLASS of ImageCommunicationObject

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MAY CONTAIN {
networkInterfaceAddress :: caseIgnoreStringSyntax,
/* the networkInterface address in the image
context, e.g. IP number, NSAP */
connectedNetwork :: distinguishedNameSyntax
/* pointer to networkImageObject that describes
the network this networkInterface is attached
to in terms of the protocol or application the
image indicates */
}

7. Security Considerations

Security issues are not discussed in this memo.

8. Authors' Addresses

Glenn Mansfield
AIC Systems Laboratory
6-6-3 Minami Yoshinari
Aoba-ku, Sendai 989-32
Japan

Phone: +81 22 279-3310
EMail: [email protected]

Thomas Johannsen
Dresden University of Technology
Institute of
Communication Technology
D-01062 Dresden
Germany

Phone: +49 351 463-4621
EMail: [email protected]

Mark Knopper
Merit Network, Inc.
1071 Beal Avenue
Ann Arbor, MI 48109

EMail: [email protected]

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9. References

[1] Harrenstein, K., Stahl, M., and E. Feinler, "NICNAME/WHOIS", RFC
954, SRI, October 1985.

[2] Mockapetris, P., "Domain Names - Implementation and
Specification", STD 13, RFC 1035, USC/Information Sciences
Institute, November 1987.

[3] Johannsen, T., Mansfield, G., Kosters, M., and S. Sataluri,
"Representing IP information in the X.500 Directory", RFC 1609,
Dresden University, AIC Systems Laboratory, Network
Solutions,Inc., AT&T Bell Laboratories, March 1994.

[4] Johannsen, T., and G. Mansfield, "The Soft Pages Project", OSI-DS
WG document, OSI-DS-39, Dresden University, AIC Systems
Laboratory, February 1993.

[5] CCITT Blue Book, "Data Communication Networks: Directory",
Recommendations X.500-X.521, December 1988.

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