Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1998-11-09
2002-07-23
Hsu, Alpus H. (Department: 2662)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S467000, C709S220000, C709S227000, C709S231000
Reexamination Certificate
active
06424653
ABSTRACT:
This invention relates generally to communications over computer networks, and more specifically to communications between components of computerized test systems over a network.
Computers and computerized devices are frequently used in networked configurations. Networks allow multiple users, each with a separate computer, to share information and hardware resources such as mass storage systems, printers, and fax machines.
Typical office environments are set up with computers connected to local area networks (LAN's), which allow relatively small numbers of computers or computerized devices in limited areas to exchange information. Generally, computers connected to a LAN belong to users within one work group.
Many companies have offices in different buildings or multiple work groups in the same building. These companies generally use wide area networks (WAN's) to network their computers. Such WAN's are often implemented by linking together multiple LAN's.
Several elements define a network. One element is the physical medium, which is the actual connection that allows information to pass from one computer to another. The physical medium is often one or more cables. However, the physical medium could also be a radio or infrared link or any other connection that allows a stream of bits to be communicated between computerized devices.
In addition to a physical medium, every network requires one or more protocols. Generally, a protocol is a set of rules that all computers and computerized devices on a network use to interpret packets of information that pass through the network. For example, a protocol might specify when it is appropriate for a particular computer to send a packet of information. The protocol might also specify the format of a packet of information. For example, it might include a way of identifying the end of a packet and a way of identifying which computer in the network is intended to receive the packet. At a higher level, the protocol might also specify a way of identifying which packets of information are logically grouped into one transmission.
LAN's typically have a physical medium in which all computers and computerized devices on the LAN are interconnected. A protocol corresponding to this physical medium is typically a “broadcast” protocol, which means that each packet is sent to every computer. Such a network is therefore commonly called a broadcast network. Each packet that is sent through a broadcast network typically contains information allowing each computer or computerized device on the network to recognize whether the packet is intended for that device. Ethernet and token ring are two examples of widely used broadcast protocols.
WAN's typically have a physical medium that provides a direct connection between each pair of computers or computerized devices that must communicate. A protocol corresponding to this physical medium is typically a “point-to-point” protocol. Such a network is therefore commonly called a point-to-point network. Public switched telephone networks (PSTN) and X.25 networks are two examples of WAN's that use point-to-point protocols.
Because the number of cables required to connect each pair of computers in a point-to-point network is often prohibitive, multiple computers in a point-to-point network are usually connected to a central computer. This central computer may be in a LAN. In that case, a device called a “terminal server” is typically used to connect the multiple computers in the point-to-point network to the central computer in the LAN.
A terminal server typically has multiple I/O ports and a computerized switch, which may be used to connect each port to the LAN. Similarly, multiple computers or computerized devices in the point-to-point network can be connected to the ports of the terminal server. Because terminal servers can be used to link LAN's with point-to-point networks, they are often referred to as a “gateways.”
In order to send information from a computer in a LAN to a computer in a point-to-point network, the LAN and the point-to-point network must generally be linked by a gateway. Further, the gateway must generally be capable of establishing a point-to-point connection with the computer in the point-to-point network. For example, a computer in the LAN may send a packet over the LAN to the gateway. Part of the packet indicates which computer in the point-to-point network is to receive the information contained in the packet, while the rest of the packet contains the information. If the gateway has the capability of establishing a point-to-point connection, then the gateway might first translate the packet from the broadcast protocol used by the LAN to the point-to-point protocol used by the point-to-point network, establish the point-to-point connection, and then send the translated packet to the indicated computer in the point-to-point network.
Data sent from a computer in a point-to-point network to a computer in a LAN generally goes through a reverse process. For example, the computer sends a packet using the point-to-point protocol to the gateway. The packet must include sufficient information to allow the gateway to create a packet that can be broadcast over the LAN to the intended computer. The gateway then broadcasts the packet using the required protocol over the LAN.
We have recognized that this type of network architecture may be used in telecommunication test networks. In that case, multiple computers and computerized devices in a point-to-point network may be connected to a central computer in a LAN through telephone lines and a gateway. In particular, the point-to-point network may be a PSTN; the computerized devices in the point-to-point network may be remote measurement units (MU); and, the central computer in the LAN may be a test system controller (TSC). Further, each I/O port in the gateway and each remote measurement unit may be connectable to the PSTN through modems.
However, we have also recognized some shortcomings in such test network architectures. First, in order for the telecommunication test network to work properly, there must be some way of initiating point-to-point connections between the test system controller and the remote measurement units. But, gateways like the terminal servers described above often do not have this capability. Further, because these gateways are typically legacy systems, they are not easily upgraded to provide such capabilities.
Even if the gateway in the telecommunication test network were capable of establishing point-to-point connections with the remote measurement units, it might do so in a non-standard manner. For example, computers and computerized devices on a computer network generally operate using standard protocols. The broadcast protocol and the point-to-point protocol mentioned above are two examples of standard protocols, which are typically based upon the Open Systems Interconnection (OSI) model. This is a widely accepted framework of standards for communicating between different computers made by different manufacturers. Test system controllers and remote measurement units that operate using standard protocols can therefore easily communicate with other devices on the LAN and the PSTN, respectively, so long as the other devices are also made to use standard protocols.
Further, one way for the test system controller to communicate with the remote measurement units is to have the gateway linking the LAN and the PSTN make translations between broadcast and point-to-point protocols.
However, there are currently no accepted standards for making such protocol translations. This is a problem in telecommunication test networks because different telephone companies typically use different network equipment. This means that gateways linking LAN's and WAN's of different telephone companies may use different custom software for making such protocol translations or otherwise establishing communications between components on the LAN's and WAN's. Consequently, the test system controllers and r
Anast Philip A.
Arsikere Amarnath R.
Bologna Joseph P.
Hsu Alpus H.
Qureshi Afsar M.
Teradyne Legal Dept.
Teradyne, Inc.
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