Electrical computers and digital processing systems: multicomput – Computer network managing – Computer network monitoring
Reexamination Certificate
1998-02-05
2001-01-30
Rinehart, Mark H. (Department: 2756)
Electrical computers and digital processing systems: multicomput
Computer network managing
Computer network monitoring
C709S220000, C709S241000, C709S241000, C370S446000, C370S466000
Reexamination Certificate
active
06182135
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the field of network management, and more particularly to processes for determining whether two communicating network drivers are directly connected across a physical link.
2. Background of the Invention
In the management of data networks, it is often desirable to understand the topology of the network, including whether there are direct links between particular devices in the network, the nature of the network intermediate devices which interconnect links or end stations on the network, and the capabilities of individual end stations on particular links. Thus, network management stations often maintain a topology map for the network to assist an administrator in the management of the network. A variety of techniques has been developed for automatically discovering the topology of the network to further automate the management of networks. See for example U.S. Pat. No. 5,421,024 entitled DETECTION OF A RELATIVE LOCATION OF A NETWORK DEVICE USING A MULTICAST PACKET PROCESSED ONLY BY HUBS invented by Faulk, Jr., et al.; see also, U.S. Pat. No. 5,293,635 entitled DETECTION ON A NETWORK BY A MAPPING APPLICATION OF A RELATIVE LOCATION OF A FIRST DEVICE TO A SECOND DEVICE invented by Faulk, Jr., et al.; U.S. Pat. No. 5,048,009 entitled BROADCAST STATION LOCATOR FOR A LOCAL AREA NETWORK invented by Conrad; and U.S. Pat. No. 5,226,120 entitled APPARATUS AND METHOD FOR MONITORING THE STATUS OF A LOCAL AREA NETWORK invented by Brown, et al.
Networks include intermediate devices which interconnect end stations and manage data flow among end stations and ports. Often, these intermediate devices are transparent to drivers running in the end stations or ports they interconnect. Thus, it is often difficult to determine whether there are intermediate devices between two communicating end points. Furthermore, it is often desirable to optimize performance of communication between communicating end stations which have drivers that are capable of certain classes of functions. Thus, automatic negotiation techniques have developed by which end points in a network negotiate the communication technique to be utilized between the end points. In these settings, it is sometimes important to ensure that there are no intervening devices between the devices negotiating the processes to be executed, which might not be able to operate under the ultimately negotiated process.
Thus, it is desirable to provide a technique which is capable of automatically determining whether there is a direct link between communicating end points on a network. Such a technique would be useful in systems which allow for automatic negotiation of network capabilities between communicating end stations, and in networks including automatic topology mapping techniques.
SUMMARY OF THE DISCLOSURE
In one embodiment, the present invention provides a method of determining if two pieces of network equipment which are controlled by communicating drivers at layer two and above, are directly connected. The present invention provides a mechanism by which a pair of communicating network equipment drivers can determine if the equipment they control, such as a network adapter, a switch port other end point, are directly connected by a single network cable. The invention is applicable to network signaling protocols which include a link active signaling technique as part of the physical layer specification. Examples include but are not limited to 10BaseT Ethernet, and 100BaseTX Ethernet where the link beat indicator is utilized. The method is useful for example to drivers who wish to auto configure or to avoid misconfiguration of the equipment they drive.
According to a first aspect of the invention, a method for determining whether a network device has a direct connection to another network device includes determining whether the link is in a first state in which there is only one device coupled to the link without intervening devices which are members of a particular class of intelligent hubs including switches, routers and other network intermediate devices that operate at level two or higher, or in a second state in which there may be more than one device coupled to the link without intervening devices which are members of the particular class. If the link is in the first state, then a physical layer test involving the physical layer link active signaling mechanism is executed to ensure that the responding device is coupled to the same link without intervening devices that are not members of the particular class.
The step of determining whether the link is in a first state or in a second state includes transmitting a message having a multi-destination MAC address on the link to notify devices which receive the message to issue a response carrying a MAC address of the responding device.
The multi-destination address falls within a special class of addresses so that packets on the network which have the multi-destination address are blocked by network devices which are members of the particular class, such as switches or routers or other network interconnecting devices having drivers that operate at layer two or higher, so that the packet does not propagate beyond such devices. After transmitting the message with the multi-destination address, the initiating network device waits a period of time for a response to the message. If no response is received within the period, then the transmitting and waiting steps are retried until a response is received or a retry limit is reached. If more than one response is received in the period, then it is determined that there may be multiple devices coupled to the link, such as by repeaters, without intervening devices that are members of the particular class. Finally, if only one response is received in the period, then a physical layer test is executed to ensure that the responding device is coupled to the same link without intervening devices that are not members of the particular class.
The physical layer test includes according to one aspect of the invention first selecting for the initiating network device one of a first process of dropping the link active signaling or a second process of monitoring the link for loss of the link active signaling from the network device. If the first process is selected for the network device, then the initiating network device drops the link active signaling on the link. After dropping the link active signaling, the initiating device waits for a period of time for a reply message from the responding device that indicates that the responding device detected the loss of the link active signaling. If no reply message is received within the waiting period, then the dropping and waiting steps are retried until a response is received or a retry limit is reached. If the reply message is received in the period, then it is determined that the responding device is directly connected to the initiating network device.
If the second process is selected for the initiating network device, then the process of monitoring the link for loss of the link active signaling from the responding device is executed. If loss of the link active signal is detected, then it is determined that the responding device is directly connected. If loss of the link active signal is not detected, then it is determined that there may be an intervening device that is not a member of the particular class on the link.
Accordingly, the network equipment driver operating according to the present invention first determines if it can establish communication with another network driver attached to the network. This is accomplished for example by sending an “exchange information” packet to the multicast address. The particular multicast address will not propagate through switches or network equipment implementing the point-to-point detection mechanism of the present invention. If more than one response is received to the request, then this implicitly means that the network equipment is not directly attached to that driven by any of t
Binder James S.
Connery Glenn William
Pickering Robert
Ruane James
3Com Corporation
Prieto Beatriz
Rinehart Mark H.
Wilson Sonsini Goodrich & Rosati
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