Multiplex communications – Data flow congestion prevention or control – Flow control of data transmission through a network
Reexamination Certificate
1999-07-19
2003-11-25
Marcelo, Melvin (Department: 2663)
Multiplex communications
Data flow congestion prevention or control
Flow control of data transmission through a network
C370S465000, C370S468000
Reexamination Certificate
active
06654346
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a communication system (“network”) and more particularly to a network of hierarchically situated nodes having forwarding modules that are programmed to assign a transmission priority of which to send packets of data between nodes and throughout the network depending on the hierarchical level of forwarding modules.
2. Description of the Related Art
A communication network is generally regarded as an interconnected set of subnetworks or subnets. The network can extend over localized subnets as an intranet, or can extend globally as an internet between one or more intranets. A communication network can therefore forward data within a localized network between termination devices extending to almost anywhere around the world. The termination devices include any data entry/retrieval system (e.g., telephone or computer), and a network includes a local and/or global interconnection of termination devices configured on one or more subnets.
The basic underpinnings of network operation is the various protocols used to communicate across the network. A popular foundation for those protocols is the Open System Interconnect (“OSI”) model. Using that model or a derivative thereof, protocols can be developed which work in concert with each other. A popular communication protocol includes the Transmission Control Protocol (“TCP”) and the Internet Protocol (“IP”). TCP/IP are used in networks that are known as packet-switched networks. The advent of asynchronous transfer mode (“ATM”) has brought about a divergence from packet-based standards to one using a cell-switched network. Packet-switched and cell-switched networks are in contrast with circuit-switched networks, such as the telephone system. As opposed to maintaining a fixed routing connection for the transmitted message, packet or cell switching evenly allocates or “switches” packet or cell portions of the message across dissimilar routes of the network. The term packet switching henceforth refers generically to switching message portions, regardless of whether that portion is a cell or packet.
In a packet-switched network, each packet of a particular message may be sent across different routes of the network at the same time and then reassembled at the proper termination device. In order to ensure the packets are properly received, certain layers of the OSI protocol stack will wrap the data before the data is sent across the network. For example, TCP can divide data into segments which are then placed into, for example, IP datagrams having a header which includes the IP address of the originating and receiving termination devices. It is not until the IP has been wrapped possibly several times will the TCP be forwarded across the network.
An important aspect of network management and administration is the need to control accesses to the network infrastructure. Accesses can be controlled for numerous reasons, some of which include security and prioritization. Security deals with restricting improper accesses, while prioritization deals with prioritizing an access to a shared resource.
There are various ways in which to secure a communication network, all of which deal with mechanisms which prevent unauthorized access to packets of data, such access is often referred to as “packet sniffing” and/or “packet spoofing”. Common security mechanisms include use of firewalls implemented in hardware and software (e.g., proxy servers, bastion hosts, filtering routers) and/or authentication systems implemented in solely in software (e.g., passwords and encryption code). Most firewalls use some form of screening subnet architecture that analyzes the incoming internet packet to determine if that packet should be placed on the internal, intranet structure. Analyzing the packet and, more specifically, the source and destination of that packet, typically adds a lag time or latency at the interface between the intranet and the internet Placing an encryption code also adds overhead to the packet and involves time-consumptive decryption at the receiving end of the network. Use of passwords appears less consumptive of transmission bandwidth. Passwords, however, can sometimes be readily broken either through a user's improper choice of password name or through a hacker sending thousands of user names and passwords until a successful combination is achieved.
It would be of benefit to secure a network without requiring the overhead of conventional firewalls. For example, eliminating routing tables within either an interior or exterior filtering router, eliminating a dedicated network of a bastion host, eliminating encryption bits and decryption, and eliminating user-specified passwords would prove beneficial if the same level (or possibly a higher level) of security could be maintained. An improved level of security which avoids conventional firewalls is preferably one based on an analysis of each packet as the packets are switched throughout the network. Analysis on each packet could desirably be performed without requiring a circuit-switched path or dedicated, private path such as those found in private lines and/or Virtual Private Lines (“VPLs”) attributable to a Virtual Private Network (“VPN”). VPNs and circuit-switched networks impose significant limitations on bandwidth utilization and network throughput and therefore should be avoided as a security solution.
Modern day networks are expected not only to be highly secure, but also to support numerous types of applications, some of which may require greater bandwidth than others. Other applications may require deterministic response time across the network. Network managers may be required to adapt the network, or at least portions of the network, so that it can guarantee a predetermined amount of bandwidth and/or propagation time for a requested Quality Of Service (“QOS”). The term “QOS” generally subsumes all the various terms used to describe “accesses” between a pair of termination devices. Access is therefore a term that can be quantified to include the speed and degree of security by which packets travel between termination devices and the fault tolerance measures which ensure the transmitted signal is clear and accurate.
The network manager may require, for example, fast, highly secure communication between termination devices residing on a local intranet, whereby the termination devices are sending both voice and video in a time-sensitive manner. There may be other intranets, however, that are not sending time-sensitive information, each of which may be connected to the intranet allocated to higher speed. The network manager may therefore need to give priority to packets sent (or received) to and from some, but not all, termination devices within the network. In other words, a need exists for allocating bandwidth through a shared resource such as a network link, switch or router, or arbitrating among competing devices that are requesting various types of accesses to the shared resource.
Conventional QOS, however, cannot provide an accurate determination of a delay (i.e., response time) between a request sent by a termination device and a response returned to that device. For instance, the transmission delay varies depending on whether the routing table portion of interest resides in the control processor cache or is within the system memory linked to the control processor by a system memory bus. Time needed to access the routing tables will therefore vary across the network leaving uncertainty as to when the requested packets will be returned to the requesting agent. Thus, conventional QOS solutions cannot guarantee response times even though a specific class of service has been designated. Instead, QOS is limited to determining availability and reliability of the transmission path not, e.g., worst case response time.
It would be of benefit to be able to specify a QOS and to designate classes of service for certain accesses within the network based on the time-sensitive nature by which the applications must operate.
Kapadia Viren H.
Mahalingaiah Rupaka
Conley & Rose, P.C.
Daffer Kevin L.
Dunti Corporation
Lee Andy
Marcelo Melvin
LandOfFree
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