Multiplex communications – Data flow congestion prevention or control – Flow control of data transmission through a network
Reexamination Certificate
1999-03-22
2004-09-28
Duong, Frank (Department: 2666)
Multiplex communications
Data flow congestion prevention or control
Flow control of data transmission through a network
C370S413000
Reexamination Certificate
active
06798743
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates generally to methods and apparatus for transmitting digital data in a packet-switched computer network. More specifically, the present invention relates to a packet prioritization processing technique for routing traffic in a packet-switched computer network.
2. Routers and Network Protocol
A computer network is a geographically distributed collection of interconnected communication links for transporting data between nodes, such as computers. By definition, a network is a group of computers and associated devices that are connected by communications facilities or links. Network connections can be of a permanent nature, such as via cables, or can be of a temporary nature, such as connections made through telephone or other communication links. A plurality of computer networks may be further interconnected by intermediate nodes, or routers, to extend the effective “size” of the networks, smaller portions of which may be maintained as autonomous domains of nodes. A router is computer system that stores and forwards data packets from one local area network (LAN) or wide area network (WAN) to another. Routers see the network as network addresses and all the possible
10
paths between them. They read the network address in a transmitted message and can make a decision on how to send it based on the most expedient route (traffic load, line costs, speed, bad lines, etc.). Routers typically communicate by exchanging discrete “packets” of data according to predefined protocols. In this context, a protocol comprises a set of rules defining how the nodes interact with each other.
Networks vary in size, from a local area network (LAN) consisting of a few computers and related devices, to a wide area network (WAN) which interconnects computers and LANS that are geographically dispersed. An internetwork, in turn, is the joining of multiple computer networks, both similar and dissimilar, by means of gateways or routers that facilitate data transfer and conversion from various networks. A well known abbreviation for internetwork is internet. As currently understood, the capitalized term Internet refers to the collection of networks and gateways that uses a Transmission Control Protocol/Internet Protocol (TCP/IP). The Internet has recently seen explosive growth by virtue of its ability to link computers located throughout the world.
FIG. 1
shows a diagram of an IP network, which is an example of one type of flow-based network in which the technique of the present invention may be implemented. A flow can be a hard-state virtual circuit in an ATM network, a soft-state flow in an IP network (e.g., a MPLS tunnel), or a stateless connection as a TCP/IP connection in today's Internet. As shown in
FIG. 1
, the IP network
2
includes the Internet (or a WAN)
4
over which a Node
16
(e.g. a computer) can communicate with a separate node
6
via a plurality of intermediate nodes (e.g. R
1
, R
3
, R
4
). Node
6
may be, for example, a server which is part of Local Area Network (LAN)
7
, connected to the Internet via routers R
1
and R
3
. Router R
3
(
10
) may, in turn, connect one or more other routers (e.g., router R
2
) with the Internet.
A LAN is a communication network that serves users within a confined geographical area. It is made up of servers, workstations, a network operating system and a communications link. Servers are high-speed machines that hold programs and data shared by all network users. The workstations, or clients, are the user' personal computers, which perform stand-alone processing and access the network servers as required The controlling software in a LAN is the network operating system, such as, for example, NetWare, UNIX, and/or Appletalk, which resides in the server. Message transfer is managed by a transport protocol such as, for example, IPX, SPX, SNA and/or TCP/IP. The physical transmission of data is performed by the access method (Ethernet, Token Ring, etc.) which is implemented in the network adapters that plug into the machines. The actual communications path is the cable (twisted pair, coax, optical fiber) that interconnects each network adapter.
In order to reduce design complexity, most networks are organized as a series of hardware and software levels or “layers” within each node. These layers interact to format data for transfer between, e.g., a source node and a destination node 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 means of the predefined protocols. This layered design permits each layer to offer selected services to other layers using a standardized interface that shields those layers from the details of actual implementation of the services. The layered protocols, commonly referred to as protocol stacks, are described in greater detail with reference to FIG.
2
.
FIG. 2
illustrates the relationship of subnetworks and gateways to layered protocols. Assume that the user application
202
A in host A sends an application protocol data unit (PDU) to an application layer protocol
202
B in host B, such as, for example, a file transfer system. The file transfer software performs a variety of functions and sends file records to the user data. In many systems, the operations at host B are known as server operations and the operations at host A are know as client operations.
As indicated by the downward arrows in the protocol stack at host A, this unit is passed to the transport layer protocol
204
A, which performs a variety of operations and adds a header to the PDU passed to it. At this point, the unit of data is often referred to as a segment. The PDU from the upper layers is considered to be data to the transport layer.
Next, the transport layer passes the segment to the network layer
206
A, also called the IP layer, which again performs specific services and appends a header. This unit (now called a datagram in internet terms) is passed down to the lower layers. Here, the data link layer adds its header as well as a trailer, and the data unit (now called a frame) is launched into subnetwork
210
by the physical layer
208
A. Of course, if host B sends data to host A, the process is reversed and the direction of the arrows is changed.
Internet protocols are typically unaware of what goes on inside the network. The network manager is free to manipulate and manage the PDU in any manner necessary. In some instances, however, the internet PDU (data and headers) remains unchanged as it is transmitted through the subnet. In
FIG. 2
, it emerges at the gateway where it is processed through the lower layers
214
and passed to the IP (network) layer
212
. Here, routing decisions are made based on the destination address provided by the host computer.
After these routing decisions have been made, the PDU is passed to the communications link connected to the appropriate subnetwork (comprising the lower layers). The PDU is re-encapsulated into the data link layer frame and passed to the next subnetwork
216
, where it finally arrives at the destination host.
The destination (host B) receives the traffic through its lower layers and reverses the process that transpired at host A; it de-encapsulates the headers by stripping them off in the appropriate layer. The header is used by the layer to determine the actions it is to perform; the header therefore governs the layer's operations.
The PDU created by the file transfer application in the application service layer is passed to the file transfer application residing at host B. If lost A and B are large mainframe computers, this application is likely an exact duplicate of the software at the transmitting host. The application might, however, perform a variety of functions, depending on the header it receives. It is conceivable that the data could be passed to another end-user application at host B, but in many instances the user at host A merely wants to obtain the services of a server pro
Agasaveeran Saravanan
Berl Steven
Ma Qingming
Shi Zhanhe
Beyer Weaver & Thomas LLP.
Duong Frank
Wolf, Esq. Dean E.
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