Multiplex communications – Network configuration determination
Reexamination Certificate
1999-09-17
2001-07-17
Hsu, Alpus H. (Department: 2662)
Multiplex communications
Network configuration determination
C370S351000, C370S389000, C709S220000, C709S238000
Reexamination Certificate
active
06262976
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to interconnectivity of computing machinery and in particular to moving information among a plurality of networked computers.
BACKGROUND OF THE INVENTION
Modularized/layered solutions or “protocols” are known which permit computer systems to communicate, regardless of connection method or vendor-specific hardware implementation, or to permit different networks to communicate or be “internetworked.” Known systems provide for connectivity in and among networks of computerized equipment, and address the problems associated with interconnectivity. Layering in known systems divides the task of interconnection and communication into pieces (layers), wherein each layer solves a piece of the problem or provides a particular function and is interfaced to adjacent layers. Each of the layers is responsible for providing a service to ensure that the communication is properly effected. Examples of some services provided by the various layers are error detection, error recovery, and routing among many communication paths. All the layers in conjunction present the overall communication protocol. It is generally well accepted in the art of internetworking that modularizing in layers with well defined functional interfaces, divides and effectively reduces the complexity of the connectivity problem and leads to a more flexible and extensible solution.
A model for describing the layers in a network has been posited by the International Standards Organization (ISO). The ISO open systems interconnection (OSI) model is a seven-layer model, illustrated in FIG.
1
. The OSI model provides a standard for describing a network and facilitating computer communications. The OSI model defines the layers and units of information that pass along a network. As illustrated, data from an application or process running on a first host (HOST A) moves down the model network layers to a Physical layer. The Physical layer defines the physical connection which transmits raw bits across a communication channel to another host (HOST B) and up corresponding layers to a process running thereon. OSI, while defining a model or framework in which standards and protocols can be developed at each layer, allows for a flexible approach for implementation of the model. OSI and other layered computer network communications standards are well known and described in detail in the Handbook of Computer-Communication Standards by William Stallings, which is incorporated herein by reference.
Layered protocols and interfaces therebetween have been defined, which provide specifications for communication between a process or program being executed on one computer's operating system and another process running on another computer. Transmission Control Protocol/Internetwork Protocol (TCP/IP) are two protocols that are part of a protocol suite or family of protocols layered and designed to connect computer systems that use different operating systems and network technologies. TCP/IP, which provides a common set of protocols for invocation on dissimilar interconnected systems, is illustrated and mapped in
FIG. 1
a
to analogous layers of the OSI model. TCP/IP is described in detail in ITERNETWORKING WITH TCP/IP, VOLUME I, by Douglas E. Comer, published by Prentice-Hall Inc., 1995, and/or TCP/IP ILLUSTRATED, VOLUME I, by W. Richard Stevens, published by Addison-Wesley, 1994, which are incorporated herein by reference.
TCP/IP is a four layer protocol suite which facilitates the interconnection of two or more computer systems on the same or different networks. In certain networks, such as the Internet, TCP/IP is a requirement for interoperability. The four layers comprise two independent protocols: TCP which can be used to access applications on other systems within a single network; and IP which permits identification of source and destination addresses for communication between systems on different networks.
As illustrated in
FIG. 2
, application or process data communicated via TCP/IP is “packetized” as it passes down layers through the protocol suite. The original process data first has an information block called a TCP Header prefatorily appended thereto in a TCP layer, to form a TCP packet. The TCP Header contains information to assure that the data travels from point to point reliably without picking up errors or getting lost. An IP layer repacketizes the TCP packet into an IP packet, by adding an IP Header which contains information needed to get the packet to a destination node. The IP packet is further packetized, such as in ANSI/IEEE 802 local area network protocol, with an additional Logical Link Control (LLC) address header and a control header at an LLC layer, to form an LLC Protocol Data Unit (LLCPDU). The LLCPDU is “framed” for transmission by addition of a Media Access Control Header and Trailer, to form a MAC Frame for communication between two TCP/IP facilities.
A considerable amount of “baggage” in the form of headers and trailer information is added to data which is transmitted between facilities using a layered protocol suite, such as TCP/IP and other layered protocols known in the art. Many additional bits are added at the various layers and must be processed for ultimate transmission across a communication channel at the physical layer. At its destination, the transmitted frame must be unpacketized according to embedded instructions and passed upward through the protocol layers to its receiving application or process. In addition to the substantial increase in the amount of information that must be transmitted as a result of packetization in layered protocols, there is a significant amount of processing overhead associated with packetizing data for network and inter-network transmission. Disadvantageously, substantial computing resources and physical transmission media capacity, representing real costs, must be involved in the generation and application of header and trailer information associated with putting data and all its protocol suite baggage through the communication channel.
Historically, early networks were constituted by a plurality of computers daisy chained in a limited physical space by a common physical medium or wire, e.g. Ethernet. The primary concern with Ethernet resulted from the simultaneous transmissions on the common wire, which resulted in “collisions” and limited the amount of information that could be transmitted over the medium. When collisions occur, all packets involved in the collision are lost and must be re-transmitted. Thus Ethernet interfaces within a Local Area Network (LAN) were designed to include collision avoidance mechanisms. In this manner, traffic on the network was detected in order to await a safe opportunity for transmission. Accordingly, the amount of information that could be successfully transmitted over the LAN in a given amount of time, referred to as “bandwidth,” was increased.
As LANs grew, hardware components were required and developed (e.g. repeaters), to convey the data signals intelligibly along the extended path. Repeaters merely passively amplified signals passing from one network cable segment to the next. While repeaters increased the physical distances over which network data could be transmitted, they did not contribute to any increase in network bandwidth.
Hardware “bridges” effectively replaced repeaters for extending the size and scope of networks. Bridges addressed optimization of connectivity and, to an extent, enhanced network bandwidth. In contrast to repeaters, bridges effectively isolated network segments by actually re-creating a packet of signals as it is forwarded in a single network. Bridges are comprised of input and output ports, and maintain tables which map physical addresses to particular ports of the bridge. The tables are based on Data Link Layer (OSI Model level
2
) information in each data packet header. The bridge maps an incoming packet for forwarding to a bridge output port based on the packet's destination address. Bridges, like Ethernet interfaces, employ collision av
Brown Rudnick Freed & Gesmer
Hsu Alpus H.
Lowry David D.
Michaelis Brian L.
Ordered Networks, Inc.
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