Error detection/correction and fault detection/recovery – Pulse or data error handling – Transmission facility testing
Reexamination Certificate
1999-01-29
2002-08-13
Maung, Zarni (Department: 2154)
Error detection/correction and fault detection/recovery
Pulse or data error handling
Transmission facility testing
C714S714000, C714S715000, C709S223000, C709S224000, C370S213000, C370S465000
Reexamination Certificate
active
06434716
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not Applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable
REFERENCE TO A “MICROFICHE APPENDIX”
Not Applicable
BACKGROUND OF THE INVENTION
1. Technical Field
The field of the present invention is network testing devices and method of using same. More particularly, the present invention relates to a Link tester for assisting in establishing a link between devices on a network.
2. Background Art
Computer networks are generally used to interconnect computing devices, thereby allowing the sharing of resources and information. The use of networks has escalated as computer and networking technology advances. One of the most popular methods of establishing a network is to interconnect computing devices and resources using a Local Area Network (LAN). To assist the interconnection of computing devices, standards have evolved for interoperability. One of the most popular standards for establishing interoperability on a local area network is the Ethernet Standard. The Ethernet Standard has advanced over the years from operating at speeds of a few megabits per second to currently operating at 100 megabits per second, with higher speed standards expected in the near future. Ethernet is so widely accepted that standards organizations such as the Institute of Electrical and Electronic Engineers (IEEE) have codified United States and international standards around Ethernet. For example, the IEEE organization has established IEEE 802.3u as the most widely recognized and accepted standard in the design and installation of 100 megabit Ethernet.
Compliance by manufacturers to the Ethernet standards is voluntary and many of the new features specified in the standard have been defined only as optional requirements. Thereby devices complying with standards may still have varying capabilities. The IEEE 802.3u standard maintains equipment interoperability even with variation in LAN product capabilities by including a Physical Layer signaling scheme.
Signaling is used as a handshake between two connected pieces of LAN equipment (Link Partners) and is accomplished by exchanging a burst of pulses called Fast Link Pulses (FLPS) that form a Link Code Word. The Link Code Word describes the capabilities and fault status of the transmitting equipment which is compared to the capabilities of the receiving equipment. A Link is then established based on the highest common mode of operation. The process of establishing a Link by exchanging Link Code Words is called Auto-negotiation and must be completed prior to any data being transmitted.
The Link Code Word consists of 16 encoded data bits that provide detailed information about the transmitted equipment. The first word transmitted is the base Link Code Word which identifies the type of message being sent, the capabilities of the Link Partner, equipment fault status, received Link Code Word acknowledgment and support for additional Link Code Word information called Next Page. Once the Link Partners have exchanged the base Link Code Word, the capabilities are compared and a Link is established based on the highest common mode of operation. The following is the operating mode priority from highest to lowest:
1. 100baseTX Full Duplex
2. 100base T4
3. 100base TX Half Duplex
4. 10baseT Full Duplex
5. 10baseT Half Duplex
Additional information may be exchanged between Link Partners that support the Next Page function. Next Page information is typically vendor specific for the equipment.
A significant amount of 10 megabit Ethernet and Fast Ethernet equipment was installed in the field prior to the time when the IEEE 802.3u standard was finalized. Some of this equipment does not support the FLP scheme of handshaking but instead establishes a Link by continuously transmitting an “idle” data packet using the Fast Ethernet MLT-3 waveform. This form of Link Signaling is called Parallel Detection. When a Link Partner that supports Auto-negotiation receives a Parallel Detection signal, it will disable its FLP bursts and transmit the same Parallel Detection waveform to setup the Link. Equipment that does not support Auto-negotiation must be configured to exactly match the mode of operation as the Link Partner or else no Link can be established and the equipment will report that there is no connection to the network.
Standard ethernet (10baseT) uses a signaling scheme based on a single pulse called a Normal Link Pulse (NLP). The NLP is transmitted continuously by the Link Partners every 8 to 24 milliseconds, except during data transmission, to maintain the Link. Recently, 10baseT equipment that use the FLP method of establishing a Link have been introduced. These new products support Autonegotiation by exchanging Link Code Words and can automatically select half duplex or full duplex modes based on the highest common mode of operation.
Many types of LAN equipment allow the user to set the speed (10 Mbs or 100 Mbs) and duplex mode (half of full) of an individual port or device. The IEEE 802.3u standard does not specify what type of Link Signaling should be used when a port or device is commanded to a specific operating mode. Testing of various equipment has shown that the Parallel Detection waveform or the NLP are commonly used to establish Links when the equipment is configured to a commanded operating mode. The Parallel Detection waveform and NLP are specific regarding the speed of the Link but are ambiguous as to which duplex mode has been selected.
Link problems can occur when one Link Partner is configured to full duplex operation and the other Partner is set for Auto-negotiation and the Parallel Detection or NLP Link signals are used. The Auto-negotiating Link Partner will correctly set the Link speed but will assume a half duplex mode based on the ambiguous signal type. The Link will perform poorly or will be disabled due to high error rates and excessive collisions. Links that use Parallel Detection/NLP signaling should use one of the following configurations (both Link Partners have same speed capability):
1. Both Link Partners in Auto-negotiation Mode.
2. Both Link Partners in Full Duplex Mode.
3. One Link Partner in Half Duplex Mode and one Link Partner in Auto-negotiation Mode.
4. Both Link Partners in Half Duplex Mode.
Fast Ethernet is a powerful standard gaining widespread acceptance. However, with the rapid advancements in technologies and progressing standards, a need exists for compatibility with existing devices. This is primarily driven by business economics where companies will not generally incorporate new technologies that fail to be backwardly compatibility with the installed base of existing computer devices and network infrastructure. Backard comparability thereby allows for a slow phase-in of the new technology. Consequently, as companies, governments, and other users begin to incorporate new technologies, such as the IEEE 802.3u standard, the network environment will have equipment with varying capabilities. For example, the network may have a department where users have new computers capable of supporting the new 100 megabit Ethernet standards. However, the internal infrastructure of the network may still only support the older 10 megabit standard. Indeed, as sections of the network are updated with newer technologies, it is likely that a single network may simultaneously be required to support several versions of the Ethernet Standard.
Complicating matters further, a user may in some circumstances manually set the operating mode for particular network devices. For example, a new personal computer may have a Network Interface Card (NIC) capable of supporting the 100 megabit Ethernet Standard. However, a user may, by accident or through ignorance, configure the 100 megabit per second card to operate at a maximum of 10 megabits per second. Indeed, under the IEEE 802.3u standard devices may be manually configured to operate at one of several operational modes. Therefore, although a device may have a maximum operational mode of 100 megabits per second, for various reasons, the dev
Johnson Darrell J.
McCosh John C.
El-Hady Nabil
Maung Zarni
Psiber Data Systems Inc.
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