Electrical computers and digital processing systems: multicomput – Computer-to-computer data addressing
Reexamination Certificate
1999-07-28
2003-04-01
Maung, Zarni (Department: 2154)
Electrical computers and digital processing systems: multicomput
Computer-to-computer data addressing
C709S227000, C709S248000
Reexamination Certificate
active
06542935
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a system for obtaining computer addresses.
A computer network is a geographically distributed collection of communication links and sub-networks interconnected by intermediate stations, such as routers, for transporting data between end stations coupled to the network. A local area network (LAN) may be an example of such a sub-network consisting of a transmission medium, such as coaxial cable or twisted pair, that provides relatively short distance communication among the interconnected stations. Communication links, on the other hand, may take the form of wide area networks (WANs), such as public or private telecommunications facilities, and dial-up lines of a switched telephone network that connect stations to the network via modems. The stations typically communicate by exchanging discrete packets or frames of data according to predefined protocols. In this context, a protocol consists of a set of rules defining how the stations interact with each other.
Most networks are typically organized as a series of hardware and software levels or “layers” within each station. These layers interact to format data for transfer between, e.g., a source station and a destination station communicating over the network. Specifically, predetermined services are performed on the data as it passes through each layer and the layers communicate with each other by predefined protocols. This layered design permits each layer to offer selected services to its higher layers for the details of actual implementation of the services.
Modern communication architectures are organized as such layered designs. Whereas the lower layers of these architectures are generally standardized and, typically implemented in hardware and firmware, the higher layers are generally implemented in the form of software running in the stations attached to the network. Examples of such communications architectures include Novell Inc.'s NetWare architecture, Apple Computer Inc.'s AppleTalk architecture, and the Internet communications architecture.
The Internet architecture is represented by four layers which are termed, in ascending interfacing order, a network interface, an internetwork, a transport, and application layers. These layers are arranged to form a protocol stack in each communicating station of the network.
FIG. 1
illustrates a schematic block diagram of existing Internet protocol stacks
125
and
127
used to transmit data between a source station
110
and a destination station
150
, respectively, of a LAN environment
100
. As can be seen, the stacks
125
and
175
are physically connected through a communications channel
180
at the network interface layers
120
and
160
. For each of description, the protocol stack
125
will be described.
In general, the lower layers of the communications stack provide inter-networking services and the upper layers, which are the user of these services, collectively provide common network application services. The transport layer
114
serves as the boundary between the network-specific elements and the application-specific elements. The transport layer's fundamental service is to move a user's data from its source to its destination over a communication path using the internetwork subsystem. To do this effectively, the transport service operates end-to-end whether the path is over a single sub-network or across multiple interconnected sub-networks.
The application layer
112
provide services suitable for the different types of applications using the network, such as, terminal connections, electronic mail, the Simple Mail Transfer Protocol, and the File Transfer Protocol. The lower network interface layer
120
of the Internet architecture accepts industry standards, such as IEEE standard
802
, which defines a flexible network architecture oriented to the implementation of LANs.
Specifically, the IEEE approach addresses LAN protocols that occupy physical and data link sub-layers of layer
120
. The physical layer
126
is concerned with the actual transmission of signals across the communication channel and provides which is usually referred to as the “wire” between two nodes and a network. In this context, the physical layer defines the types of cabling, plugs, and connectors used in connection with the channel.
The data link sub-layer, on the other hand, is responsible for transmission of data from one station to another. In the IEEE 802 architecture, the data link layer is divided into two sub-layers. Logical Link Control (LLC
122
) and Media Access Control (MAC
124
). The LLC sublayer
122
manages communications between devices over a single link of a network to allow overlying internetwork layer access to the services of the LAN without regard to the actual network implementation. More specifically, the LLC layer provides for environments that need connectionless or connection-oriented services at the data link layer.
The MAC sub-layer
124
is primarily concerned with controlling access to the transmission medium in an orderly manner and, to that end, defines rules or procedures by which the stations must abide in order to share the medium. In order for multiple stations to share the same medium and still uniquely identify each other, the MAC sublayer defines a hardware or data link address called the MAC address. This MAC address is unique for each station interfacing to a LAN. The MAC layer further provides framing functions including the addition of head and trailer information needed to identify the boundaries of frames to synchronize communication between source and destination stations.
The functions provided at these lowest sub-levels are generally standard and most LAN implementations are in accord with one of three IEEE LAN standards. IEEE 802.3 carrier sense multiple access with collision detection (CSMA/CD), IEEE 802.4 token bus, or IEEE 802.5 token ring. For example, Ethernet is a LAN architecture that uses CSMA/CD for media access control.
The primary network layer protocol of the Internet architecture is the Internet protocol (IP) contained within the internetwork layer
116
. IP is primarily a connectionless network protocol that provides internetwork routing, fragmentation, and reassembly of datagrams and that relies on transport protocols for end-to-end reliability. An example of such a transport protocol is the Transmission Control Protocol (TCP) contained within the transport layer
114
. Notably, TCP provides connection-oriented services to the upper layer protocols of the Internet architecture. Although the two protocols TCP and IP are but two of the building blocks required for the complete Internet communications architecture, the term TCP/IP is commonly used to refer to this architecture.
Connection oriented services generally involve three distinct phases: connection establishment, data transfer, and connection termination. During connection establishment, a single path is found between the source and destination stations. Once the connection has been established, data is transferred sequentially over that established path and, when the connection is no longer needed, the path is terminated. As described more fully herein, the transport layer
114
and the internetwork layer
116
are substantially involved in providing predefined sets of services to aid in connecting the source station to the destination station when establishing application-to-application communication sessions.
Data transmission over the LAN
100
therefore consists of generating data in, e.g., sending process
104
executing on the source station
110
, passing that data to the application layer
112
and down through the layers of the protocol stack
125
, where the data are sequentially formatted as a frame for delivery onto the channel
180
as bits. Those frame bits are then transmitted over an established connection of channel
180
to the protocol stack
175
of the destination station
150
where they have passed up that stack to a receiving process
174
. Data flow is sc
Chernoff Vilhauer McClung & Stenzel LLP
Lin Wen-Tai
Maung Zarni
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