Electrical computers and digital processing systems: multicomput – Network computer configuring
Reexamination Certificate
1999-04-30
2002-04-23
Lim, Krisna (Department: 2758)
Electrical computers and digital processing systems: multicomput
Network computer configuring
C709S224000, C709S228000, C370S254000, C370S401000
Reexamination Certificate
active
06377987
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to the management of network systems, and more specifically to determining a physical topology of network devices in a network.
BACKGROUND OF THE INVENTION
A computer network generally includes a number of devices, including switches, routers and hubs, connected so as to allow communication among the devices. The devices within a network are often categorized into two classes: end stations such as workstations, desktop PCs, printers, servers, hosts, fax machines, and devices that primarily supply or consume information; and network devices such as gateways, switches and routers that primarily forward information between the other devices.
Network devices ordinarily operate on a continuous basis. Each device has one or more circuit boards, a microprocessor and a memory, and runs a control program. In general, networks often include several different types of data switching and routing devices. These network devices may have different physical characteristics. New devices, with characteristics that are presently unknown, are constantly being developed. In addition, the characteristics of many network devices may change over time. For example, characteristics of the network devices change when subsystems like boards, network interface modules, and other parts are added or removed from a device.
Many networks are managed, supervised and maintained by a network administrator or network manager. To properly maintain a network, the network administrator needs to have up-to-date information available about the devices in the network and how the devices are interconnected. The OSI network reference model is useful in classifying network management information. Information about what devices are in the network is generally called Layer
3
information, and information about how the devices are physically connected within the network is called Layer
2
information. In combination, this information may be used to by the network administrator to understand the physical topology of the network. The topology is a mapping that indicates the type of devices that are currently included in the network and how the interfaces of these devices are physically linked.
In addition, as an enterprise grows, a network administrator may be required to add new devices to a network or to upgrade devices in the network. To determine how and where to add or upgrade a particular device, the administrator needs to have a clear understanding of the topology of the network.
Different types of network management systems, such as OpenView, commercially available from Hewlett Packard Company of Palo Alto, Calif., may be used to identify the devices that are contained in a particular network in a limited way. In the past, constructing a network topology using automatic methods or means has been awkward or produces incomplete or inaccurate information.
For example,
FIG. 1
illustrates an example of the type of graphical display of a network topology that may be produced on a computer display using a network management software program such as OpenView. In this example, graphical view
100
includes a graphical display of devices contained in three (3) separate networks
102
,
104
,
106
, based only on Layer
3
information that has been acquired from the networks. Thus, based on the graphical view
100
, the network administrator can identify which devices are connected to which networks.
However, a drawback with this type of network management system is that it shows logical connections of network devices, but not physical connection information. It logically identifies to which network a particular device is linked, based on Layer
3
information, but it does not indicate how individual devices are physically linked together, based on Layer
2
information. Thus, an administrator cannot determine the actual interface links or physical connectivity of each of the devices. This information may be critical in determining how the network can be expanded or upgraded, or in troubleshooting.
Although
FIG. 1
illustrates a simple network environment, large enterprises may have thousands of network devices. In a large enterprise network, the foregoing problems become acute.
To address these problems, certain proprietary discovery protocols have been developed to help identify how the interfaces of each device is physically linked within a network, based on Layer
2
information. For example, the Cisco Discovery Protocol (“CDP”), which is used in products that are commercially available from Cisco Systems, Inc., is a low-level communication protocol that can help identify how devices are linked in a network. When a device supporting CDP sends a message to another device, the message includes a packet that contains its IP address and an interface descriptor. The interface descriptor represents the logical name of the port from which the message was sent. If the receiving device also supports CDP, the information is recorded at the receiving device and in certain cases may be used to determine how two devices are physically connected.
FIG. 2A
illustrates a network
200
that includes devices
202
and
204
, each supporting CDP. As illustrated, device
202
includes IP address
206
, a CDP record
210
and ports
214
,
216
. Respectively associated with port
214
and port
216
are logical names
224
,
228
. Device
204
includes IP address
208
, a CDP record
212
and ports
218
,
220
,
222
. Respectively associated with ports
218
,
220
,
222
are logical names
232
,
236
,
240
.
When a message is sent from device
202
to device
204
, device
202
includes a packet of information that contains both its IP address
206
and the logical name of the port that is used to send the message. Upon receiving the message information, device
204
records, in CDP record
212
, which port received the message and the IP address and logical name in the information packet. In this case, these values include port “FA0:3” and IP address “172.20.142.147”. Thus, by querying device
204
for the information in CDP record
212
, a network management system can conclude that port
220
is physically connected to a logical port “FA0:3” of a device having IP address “172.20.142.147”. In addition, by querying the device associated with IP address “172.20.142.147”, the management system can conclude that device
202
is configured such that logical name
224
is associated with port
214
and thus port
214
of device
202
is physically linked to port
220
of device
204
.
However, a drawback with this approach is that certain devices may not support the discovery protocol. For example, a network may include low-end devices or non-Cisco devices that do not support CDP (“non-CDP devices”). When a device does not support CDP and receives CDP information, generally it forwards the CDP information on to the next device. Thus, a network management system that relies on CDP for determining physical links of a managed network cannot identify physical links to non-CDP devices.
FIG. 2B
illustrates a network
220
that includes devices
202
,
204
,
250
. Device
250
includes IP address
268
and ports
264
,
266
that are respectively associated with logical names
254
,
258
. Assume that device
250
does not support CDP. When a message is sent from device
202
to device
204
, device
202
sends a packet of information that contains both its IP address
206
and the logical name
224
of port
214
that is used to send the message. Upon receiving the packet, instead of recording the CDP information and generating a packet based on the port that is used to communicate with device
204
, device
250
forwards the packet to device
204
. In response to receiving that packet, device
204
stores information in CDP record
212
that indicates that port
220
is physically connected to a logical port “FA0:3” of a device having IP address “172.20.142.147”. If the network management system queries device
204
, it will incorrectly determine that port
220
of device
204
is p
Cisco Technology Inc.
Hickman Palermo & Truong & Becker LLP
Holmes Craig G.
Lim Krisna
Palermo Christopher J.
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