Network link bypass device

Details Network link bypass device Network link bypass device

1999-04-08

2002-06-25

Vu, Viet D. (Department: 2154)

Electrical computers and digital processing systems: multicomput

Network-to-computer interfacing

C709S238000, C709S241000

Reexamination Certificate

active

06412016

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a device for bypassing a computer system interconnecting two network links when this computer system fails.
DISCUSSION OF THE RELATED ART
It is often desirable to insert, between two systems interconnected through a network link, a transparent control system for various possible purposes. The control system may be used for restricting access, for event logging, for ciphering and deciphering.
FIG. 1
schematically shows an arrangement providing this functionality. A system A normally communicates with a system B over a network link, such as an Ethernet link. A control system C is inserted in the network link between systems A and B. In other words, system A is coupled to a network interface card
10
of system C through a network link ethA, while system B is coupled to a second network interface card
11
of system C through a network link ethB.
System C, usually a work station, is supposed to be transparent for systems A and B as regards the network frames exchanged between them. For this purpose, system C executes software which copies the frames between links ethA and ethB. In fact, it mainly operates as a hub. In some case, however, the software may analyze the frames or even perform operations thereon.
Of course, system C is subject to failure. In case of failure, it is desirable to maintain the link between system A and system B. For this purpose, it is known to use bypass devices which are capable of detecting a hardware failure, for example by achieving CRC checks on the frames, in order to switch the network links to bypass links.
However, such devices are not able to detect a software failure, such as an abnormal program termination or a system hang. Indeed, in this case, the frames do not have errors, they are simply not copied from one link to the other.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a bypass device capable of achieving its function in case of a software failure of a control system.
This object and others are achieved by executing on the transparent system a software which provides a predetermined control signal on a control line. The control line is polled by the bypass device. The bypass device will bypass the transparent system when the control signal is not present on the control line.
According to a preferred embodiment of the invention, the control signal is in the form of periodic pulses and a bypassing is caused when a pulse is not received on the control line within a predetermined period of time.
The bypass device includes a switch having a first position selecting a main path between first and second network links, including the transparent system, and a second position selecting a bypass path between the first and second network links. A control circuit selects the first position of the switch when the control signal is received on the control line, and selects the second position of the switch when the control signal is not received on the control line.
The foregoing and other objects, features, aspects and advantages of the invention will become apparent from the following detailed description of embodiments, given by way of illustration and not of limitation with reference to the accompanying drawings.


REFERENCES:
patent: 4594724 (1986-06-01), Hogan
patent: 5317198 (1994-05-01), Husbands
patent: 5677838 (1997-10-01), Itou et al.
patent: 6038044 (2000-03-01), Fee et al.
patent: 6038618 (2000-03-01), Beer et al.
patent: 6122753 (2000-09-01), Masuo et al.
patent: 0 397 196 (1990-11-01), None
Patent Abstracts of Japan, Publication No. 10051479, Publication Date: Feb. 20, 1998.

Affiliated with

Also associated with

Rating

Network link bypass device does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Network link bypass device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Network link bypass device will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2900244