Multiplex communications – Channel assignment techniques – Details of circuit or interface for connecting user to the...
Reexamination Certificate
2000-09-28
2004-09-21
Nguyen, Brian (Department: 2661)
Multiplex communications
Channel assignment techniques
Details of circuit or interface for connecting user to the...
C370S419000, C370S503000, C713S300000
Reexamination Certificate
active
06795450
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the field of computer network point to point data communications, and more particularly to communications links that normally use constant idle bit streams between packet transmissions.
2. Background
a. Communications Networks
There are many different types of networks, network systems, and network devices for sharing files and resources or for otherwise enabling communication between two or more computers, PCs (personal computers), workstations, telephones, etc. The term “network device”, “network node” or “network component” generally refers to a computer linked to a network via a network interface card (NIC), or refers to other devices or apparatus that perform specialized functions in the network, such as repeaters, bridges, switches, routers, brouters, to name a few examples. Networks may be categorized based on various features and functions. For example, the range of a network refers to the distance over which nodes are distributed, such as local-area networks (LANs) within an office or floor of a building, wide-area networks (WANs) spanning across a college campus, or a city or a state, and global-area networks (GANs) spanning across national boundaries.
In designing a network, there are a large number of possible network configurations (such as ring, tree, star, hybrid combinations of these, etc.) and communication protocols (such as analog or digital and isochronous or non-isochronous) from which to choose. For example, a star-topology network has data sources and sinks coupled to nodes and the nodes are coupled to a central hub in a star topology. Each node (which may have one or more data sources and sinks coupled thereto) assembles the data received from the one or more data sources coupled to it into the designated frame template and transmits it to the hub.
Many networks operate in accordance with the OSI (Open Systems Interconnection) Reference Model, which is a seven-layer model developed by the ISO (International Standardization Organization). The OSI Reference Model describes how to interconnect any combination of network devices in terms of seven functional layers organized in a hierarchy, and specifies the functions that must be available at each layer. From highest level of the hierarchy to lowest level of the hierarchy, the OSI Reference Model includes the Application layer, the Presentation Layer, the Session Layer, the Transport Layer, the Network Layer, the Data-Link Layer and the Physical Layer.
Network architectures (such as Ethernet, ARCnet, Token Ring, and FDDI) encompass the Data-Link and Physical Layers and represent the most common protocols used. The Data Link layer is responsible for constructing and transmitting data packets as well as receiving and deconstructing data packets, both sequences based upon the network architecture being employed. The Data-Link layer provides services for the various protocols at the Network Layer and uses the Physical Layer to transmit and receive the data packets. In a Local Area Network Carrier Sense Multiple Access with Collision Detection (LAN CSMA/CD) implementation according to the Institute of Electrical and Electronics Engineers, Inc. (IEEE) Standard 802.3 or 802.3u-1995 (IEEE Standards) (See IEEE 802.3 Standard for Carrier Sense Multiple Access with Collision Detect (CSMA/CD) Access method and Physical Layer Specifications, 1998 Edition), the Data-Link Layer is divided into two sub-layers, the Logical-Link Control (LLC) sub-layer at the top and the Media-Access Control (MAC) sub-layer at the bottom. The LLC sub-layer provides an interface for the Network Layer protocols while the MAC sub-layer provides access to a particular physical encoding and transport scheme of the Physical Layer. The MAC sub-layer is typically executed by a MAC device that operates at one of several standard clock frequencies. Similarly, the Physical Layer is typically executed by a Physical Layer Device (PHY) that is responsible for transmitting and receiving digital code from a communications media or line, and converting the digital signals into higher intelligence signals for the device MAC.
Several structures and protocols are known for implementing the Data Link (e.g. a MAC) and Physical Layers (e.g. a PHY). Ethernet using coaxial, twisted pair or fiber-optic cables operates at 10 megabits per second (Mbps) (e.g. 10BASE-T, 10BASE-F) while fast Ethernet operates at 100 Mbps (e.g. 100BASE-T, 100BASE-FX). ARCnet (Attached Resource Computer Network) is a relatively inexpensive network structure using coaxial, twisted pair or fiber-optic cables operating at 2.5 or 20 Mbps. Token Ring topologies use special IBM cable or fiber-optic cable and operate between 1 and 16 Mbps. Fast Token Ring operates at 100 Mbps. A new standard is being developed called ATM (Asynchronous Transfer Mode), which operates at speeds of 25.6 or 155 Mbps, although newer versions may operate at even higher data rates. Of course, various other network structures are known and available.
Over the years, many networks have been designed to operate in 10BASE-T protocol. However, as faster and more sophisticated communication became possible through improvements in equipment and technology, it has become desirable to provide multi-service protocols which can support both older protocols, such as 10BASE-T, as well as additional communication protocols such as those listed above. This is so that it is not necessary to replace the entire network and related components with new equipment when upgrading to the newer protocol.
During network communications, the Physical Layer (e.g. a PHY) receives data packets from the Data-Link Layer (e.g. a MAC) above it and converts the contents of these packets into a series of electrical signals that represent 0 and 1 values in a digital transmission. These signals are sent across a transmission medium to a partner Physical Layer at the receiving end of the network link. At the destination, the partner Physical Layer (e.g. a PHY) converts the electrical signals into a series of bit values, which are grouped into packets and passed up to the Data-Link Layer (e.g. a MAC) of the destination device by the Physical Layer (e.g. a PHY) of the destination partner network device.
b. Prior LAN Systems
FIG. 1
is a block diagram of a typical prior LAN system
100
showing key functional components. It illustrates one of the most common IEEE 802.3 Ethernet communications links, which requires two PHY layer devices (e.g. a network interface card (NIC)
112
and a Switch device
114
) in order to communicate. The Switch device comprises a switch
120
connected to media access controllers (MACs)
116
, which are in turn connected to switch physical layer devices (Switch PHYs)
118
, which are connected to a wired link
122
. Similarly, the NIC
112
comprises a media access controller (MACs)
116
connected to a NIC physical layer device (NIC PHYs)
124
, which is also connected to the wired link
122
.
The switch device media access controllers (MACs)
116
provide data media to the switch device physical layer devices (Switch PHYs)
118
, which in turn transmit and receive data from the wired link
122
. Similarly, the NIC
112
media access controller (MACs)
116
providing data media to the NIC physical layer device (NIC PHYs)
124
, which in turn transmits and receives data from the wired link
122
. Thus, by using a communications language, mode, or protocol that the other “partner” understands, the switch and NIC are able to “talk” to each other over the “link”.
The wired link
122
, or media connecting two PHYs normally consists of two twisted-pair cables, with one pair utilized for receiving data and the other for transmitting data. However, various other appropriate wired link
122
media may be used to connect PHYs, such as coax cable, fiber optic cable, satellite links, cell links, radio waves, etc.
c. Physical Layer Devices (PHYs)
FIG. 2
is a block diagram of a typical prior physical layer device (PHY)
200
showing key functional components. The same
Andersson Ralph
Mills Andrew
Nguyen Brian
TDK Semiconductor Corporation
The Hecker Law Group, PLC
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