Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1999-07-30
2003-10-07
Patet, Ajit (Department: 2664)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S403000
Reexamination Certificate
active
06631137
ABSTRACT:
FIELD OF THE INVENTION
The present invention deals with a method and system for improving high speed internetwork data transfers. More particularly, the invention is intended to interconnect Token ring/IP Hosts over Token ring Local Area Networks (LAN) and a Wide Area Network (WAN) by creating one way bridged path for host-to-host connections, using IP routing protocols to create the path, so that the LAN virtually enlarges till it encompasses the WAN with bridging getting everywhere.
BACKGROUND ART
Modern digital networks are made to operate over different transmission media and interconnect, upon request, a very large number of users and applications through fairly complex digital communication networks.
Accordingly, due to the variety of users' profiles and distributed applications, the corresponding traffic is becoming more and more bandwidth consuming, non-deterministic and requiring more connectivity. This has been the driver for the emergence of fast packet switching techniques in which data from multimedia origin are chopped into fixed length packets (e.g. in Asynchronous Transfer Mode (ATM) type of operation) or in variable length packets (e.g. in so called Frame Relay (FR) type of operation). These packets are then transferred upon request for communication purposes between data sources and targets via so-called high speed communication networks. One of the key requirements for high speed packet switching networks is to reduce the end to end delays.
Also, due to the incredible increase of traffic, several types of networks have been installed which need to be interconnected to optimize the possibilities of organizing traffic between a source host terminal and a target host terminal, both located anywhere. This is made possible by using so-called internetworking (also referred to as internet). An internet is a collection of heterogeneous networks using a set of networking protocols (TCP/IP, i.e Transmission Control Protocol/Internet Protocol) developed to allow cooperating computers to share resources across the network. TCP/IP products are made by vendors and a fairly large number of networks of all kinds use it. Accordingly, the considered IP switching technologies may incorporate new proprietary protocols, which complicates inter-networking operations.
TCP/IP is a set of data communication protocols that are referred to as the internet protocol (IP) suite. Because TCP and IP are the best known of the protocols, it has become common to use the term TCP/IP to refer to the whole family. TCP and IP are two of the protocols in this suite. Other protocols that are part of the internet suite are User Datagram Protocol (UDP), Internet Control Message Protocol (ICMP), Address Resolution Protocol (ARP), Real Time Protocol (RTP) and Reservation Protocol (RSvP).
An Internet is a collection of heterogeneous networks using TCP/IP. The administrative responsibilities for an internet (for example, to assign IP addresses and domain names) can be within a single group or distributed among multiple groups. Networks comprising an internetwork can use either the same or different technologies.(For more information on TCP/IP one may refer to the book “Internet working with TCP/IP” by Douglas Comer).
Host stations attached to LANs can send messages from any of them to any other. Communication within a single (LAN) network is referred to as intranetworking, and communications between stations that are attached to different LAN networks is called internetworking. Stations within a same network can communicate directly, while internetworking communications have to go across special internetworking devices called gateways and possibly referred to as routers as they route data from one network into another.
As shall be emphasized in the following description, the routers may, in some cases be replaced by so-called bridges. Both have specific characteristics as they operate at different layers of protocols of the network.
As networks have developed, various approaches have been used in the choice of communication characteristics such as communication medium, network topology, message formats, protocols for channel access etc . . . . Some of these approaches have been converted into standards. A model of these standards is known as the International Standards Organization (ISO) Open System Interconnection (OSI) model. This model specifies a hierarchy of protocol layers and defines the function of each layer in the considered network. Each layer in one station which might be a host computer or a Router/Bridge carries a conversation with the corresponding layer in another station with which communication is taking place, in accordance with the protocol defining the rules of this communication. In fact, information is transferred down from layer to layer in one host or router then through the channel medium and back up the successive layers in the other host or router/bridge (target). Accordingly, the higher the layer at which communication operations are performed, the longer and more cycle consuming the process.
IETF standardizes TCP/IP through RFCs (Requests For Comments).The three layers (out of seven) defined by the OSI Standards and to be considered here include the physical layer, the data link layer and the network layer. The physical layer is the lowest layer (i.e level 1) assigned to transmission of data bits over the communication channel. Design of the physical layer involves issues of electrical, mechanical or optical engineering, depending on the physical medium used to build the communication channel.
The layer next to the physical layer, is the data link layer (i.e. level 2). The main task of the data link layer is to transform the physical layer interfacing with the channel into a communication link that appears error-free to the next above layer, i.e. the network layer (level 3). The data link layer performs such operations as structuring data into packets or frames and attaching control information and numbers to the packets or frames to enable checking data validity and reinserting reconstructed packets at the right location into the data flow. There are two point-to-point types of connections i.e. connectionless and connection oriented connections.
Although the data link layer is primarily independent of the nature of the transmission medium, certain aspects of the data link layer functions are dependent on the transmission medium. This is why, in some network architectures, the data link layer is divided into two sublayers: a logical link control sublayer which performs all medium-independent functions of the data link layer, and Media Access Control (MAC) sublayer. The MAC sublayer determines which station should get access to the communication channel, when requests for access are in conflict. The functions of the MAC sublayer are more likely to be dependent on the transmission medium. Bridges may be designed to operate in the MAC sublayer.
As internetwork topologies become more and more complex, the number and significance of routers or bridges used to interconnect the network both increase. Consequently, the choice between these two devices for performing the interconnecting function may seriously impact the whole internetwork performance, e.g. in terms of transmission time delay.
The basic function of a bridge is to make large interconnected networks look like a single flat LAN. A bridge acts at the MAC layer and listens to all message traffic on all networks (e.g. LANs) to which it is connected, and forwards each message onto the networks other than the one from which the message was received. Bridges also maintain a database of station locations derived from the content of the messages being forwarded. After a bridge has been in operation for some time, it can associate practically every station with a particular link (i.e. path) connecting the bridge to a network (e.g. LAN) which contributes to speeding up the traffic.
There are two main types of bridges which are: Transparent Bridges (TB) and Source Route Bridges (SRB). There are also combinations of these (SRT
Lorrain Jean
Thubert Pascal
Cesari and McKenna LLP
Cisco Technology Inc.
Patet Ajit
Shah Chirag
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