Electrical computers and digital processing systems: multicomput – Miscellaneous
Reexamination Certificate
1999-05-20
2003-05-27
Maung, Zarni (Department: 2156)
Electrical computers and digital processing systems: multicomput
Miscellaneous
C709S223000, C709S224000, C370S357000, C370S360000
Reexamination Certificate
active
06571272
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to computer networks and, more particularly, to management of entities in a computer network having a multi-hop peer connection topology.
BACKGROUND OF THE INVENTION
Data communications in a computer network involves the exchange of data between two or more entities interconnected by communication links and subnetworks. These networks are typically software programs executing on hardware computer platforms which, depending on their roles within a network, may serve as host stations, end stations or intermediate stations. Examples of intermediate stations include routers, bridges and switches that interconnect communication links in subnetworks; an end station may be a computer located on one of the subnetworks. More generally, an end station connotes a source of or target for data that typically does not provide routing or other services to other computers on the network. A local area network (LAN) is an example of a subnetwork that provides relatively short-distance communication among the interconnected stations; in contrast, a wide area network (WAN) facilitates long-distance communication over links provided by public or private telecommunications facilities.
End stations typically communicate by exchanging discrete packets or frames of data according to predefined protocols. In this context, a protocol represents a set of rules defining how the stations interact with each other to transfer data. Such interaction is simple within a LAN, since these are typically “multicast” networks: when a source station transmits a frame over the LAN, it reaches all stations on that LAN. If the intended recipient of the frame is connected to another LAN, the frame is passed over a routing device to that other LAN. Collectively, these hardware and software components comprise a communications network and their interconnections are defined by an underlying architecture.
Most computer network architectures are 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 that data as it passed through each layer, and the layers communicate with each other by means of the predefined protocols. This design permits each layer to offer selected services to other layers using a standardized interface that shields the other layers from details of actual implementation of the services. The lower layers of these architectures are generally standardized and implemented in hardware and firmware, whereas the higher layers are usually implemented in the form of software. Examples of such communications architectures include the System Network Architecture (SNA) developed by International Business Machines (IBM) Corporation and the Internet Communications Architecture.
The Internet architecture is represented by four layers termed, in ascending interfacing order, the network interface, internetwork, transport and application layers. The primary internetwork layer protocol of the Internet architecture is the Internet Protocol (IP). IP is primarily a connectionless protocol that provides for internetworking routing, fragmentation and reassembly of exchanged packets-generally referred to as “datagrams” in an Internet environment-and which relies on transport protocols for end-to-end reliability. An example of such a transport protocol is the Transmission Control Protocol (TCP), which is implemented by the transport layer and provides connection-oriented services to the upper layer protocols of the Internet architecture. The term TCP/IP is commonly used to denote this architecture; the TCP/IP architecture is discussed in
Computer Networks,
3
rd edition
, by Andrew S. Tanenbaum, published by Prentice-Hall, PTR in 1996, all disclosures of which are incorporated herein by reference, particularly at pages 28-54.
SNA is a communications framework widely used to define network functions and establish standards for enabling different models of IBM computer to exchange and process data. SNA is essentially a design philosophy that separates network communications into several layers termed, in ascending order, the physical control, the data link control, the path control, the transmission control, the data flow control, the presentation services and the transaction services layers. Each of these layers represents a graduated level of fimction moving upward from physical connections to application software.
In the SNA architecture, the data link control layer is responsible for transmission of data from one end station to another. Bridges or devices in the data link control layer are used to connect two or more LANs so that end stations on either LAN are allowed to access resources on the LANs. Connection-oriented services at the data link layer generally involve three distinct phases: connection establishment, data transfer and connection termination. During connection establishment, a single path or connection, e.g., an IEEE 802.2 logical link control type 2 (LLC2) connection, is established between the source and destination stations. Once the connection has been established, data is transferred sequentially over the path and, when the LLC2 connection is no longer needed, the path is terminated. Reliable communication of the LLC2 is well known and described by Andrew Tanenbaum in his book
Computer Networks, Second Edition
, published in 1988, all disclosures of which are incorporated herein by reference, especially at pages 253-257.
FIG. 1
is a schematic block diagram of a conventional computer network
100
having a host computer coupled to a Token Ring (TR) network TR
1
and an end station coupled to TR
2
. The TR networks are of the type that support Source/Route Bridging (SRB) operations with respect to the contents of a routing information field (RIF) of a frame. The host computer is preferably a SNA host entity comprising a mainframe computer
110
coupled to a channel-attached router or front end processor (FEP), hereinafter referred to as the “host network connection”
112
; in addition, the end station is a “physical unit” (PU) SNA entity
114
. An SRB bridging device B
1
interconnects TR
1
and TR
2
such that the SRB network
100
effectively functions as a LAN.
The PU communicates with the host by exchanging TR frames over LLC2 connections or sessions through the SRB network. Each TR frame
120
includes a RIF
122
that contains source route information in the form of ring number/bridge number pair “hops” within a path between the stations. For example, the RIF
122
of TR frame
120
transmitted by the PU to host contains [0021.0010]. An LLC2 session is established between the stations using a special TR frame, called an explorer frame.
The explorer frame is used by a source (PU) to “discover” the path to a destination (host); thereafter, a Set Asynchronous Balanced Mode Extended (SABME) frame is sent from the PU to the host to establish a logical connection between the end stations, and the host responds to the SABME frame with an Unnumbered Acknowledgment (UA) frame. Once the UA frame is received by the PU, a connection is established between the source and destination, and these stations communicate by exchanging TR information (INFO) and acknowledgment frames until the logical link SNA session is completed.
For example, the PU transmits an INFO frame over TR
2
and through BR
1
and TR
1
to the host. Upon successfully receiving the INFO frame, the host responds by transmitting an LLC2 Receive/Ready (RR) acknowledgment frame over the SRB network to the PU. This INFO/RR exchange continues until the PU has successfully transmitted all of its data and the host has successfully received all of that data. Session completion is then initiated by a Disconnected Mode (DM) frame being transmitted from the PU to the host; the disconnection is thereafter acknowledged by the host responding with a UA frame. The LLC2 frames (p
Clouston Robert
Ferguson Darin
Talerico Anthony
Cesari and McKenna LLP
Cisco Technology Inc.
Hu Jinsong
Maung Zarni
LandOfFree
Method and apparatus for SNA/IP correlation with multiple... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for SNA/IP correlation with multiple..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for SNA/IP correlation with multiple... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3051845