Electrical computers and digital processing systems: multicomput – Computer network managing – Computer network monitoring
Reexamination Certificate
1998-11-23
2002-06-25
Maung, Zarni (Department: 2154)
Electrical computers and digital processing systems: multicomput
Computer network managing
Computer network monitoring
C709S223000, C709S230000, C709S238000, C709S242000, C370S230000, C370S235000, C370S252000, C370S355000, C370S356000
Reexamination Certificate
active
06412000
ABSTRACT:
COPYRIGHT NOTICE
A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever.
Further, this application makes reference to the following commonly owned U.S. Patent Application, which are incorporated by reference herein in their entirety for all purposes:
U.S. Pat. No. 5,802,106, in the name of Robert L. Packer, entitled “Method for Rapid Data Rate Detection in a Packet Communication Environment Without Data Rate Supervision,” relates to a technique for automatically determining the data rate of a TCP connection;
U.S. patent application Ser. No. 08/977,376, now U.S. Pat. No. 6,046,980, in the name of Robert L. Packer, entitled “Method for Managing Flow Bandwidth Utilization at Network, Transport and Application Layers in Store and Forward Network,” relates to a technique for automatically allocating bandwidth based upon data rates of TCP connections according to a hierarchical classification paradigm; and.
U.S. patent application Ser. No. 08/742,994, now U.S. Pat. No. 6,038,216 in the name of Robert L. Packer, entitled “Method for Explicit Data Rate Control in a Packet Communication Environment Without a Data Rate Supervision,” relates to a technique for automatically scheduling TCP packets for transmission.
BACKGROUND OF THE INVENTION
This invention relates to digital packet telecommunications, and particularly to management of network bandwidth based on information ascertainable from multiple layers of OSI network model. It is particularly useful in conjunction with bandwidth allocation mechanisms employing traffic classification in a digitally-switched packet telecommunications environment, as well as in monitoriing, security and routing.
The ubiquitous TCP/IP protocol suite, which implements the world-wide data communication network environment called the Internet and is also used in private networks (Intranets), intentionally omits explicit supervisory function over the rate of data transport over the various media which comprise the network. While there are certain perceived advantages, this characteristic has the consequence of juxtaposing very high-speed packet flows and very low-speed packet flows in potential conflict for network resources, which results in inefficiencies. Certain pathological loading conditions can result in instability, overloading and data transfer stoppage. Therefore, it is desirable to provide some mechanism to optimize efficiency of data transfer while minimizing the risk of data loss. Early indication of the rate of data flow which can or must be supported is imperative. In fact, data flow rate capacity information is a key factor for use in resource allocation decisions. For example, if a particular path is inadequate to accommodate a high rate of data flow, an alternative route can be sought out.
Internet/Intranet technology is based largely on the TCP/IP protocol suite, where IP, or Internet Protocol, is the network layer protocol and TCP, or Transmission Control Protocol, is the transport layer protocol. At the network level, IP provides a “datagram”delivery service. By contrast, TCP builds a transport level service over the datagram service to provide guaranteed, sequential delivery of a byte stream between two IP hosts.
TCP flow control mechanisms operate exclusively at the end stations to limit the rate at which TCP endpoints emit data. However, TCP lacks explicit data rate control. The basic flow control mechanism is a sliding window, superimposed on a range of bytes beyond the last explicitly-acknowledged byte. Its sliding operation limits the amount of unacknowledged transmissible data that a TCP endpoint can emit.
Another flow control mechanism is a congestion window, which is a refinement of the sliding window scheme, which employs conservative expansion to fully utilize all of the allowable window. A component of this mechanism is sometimes referred to as “slow start”.
The sliding window flow control mechanism works in conjunction with the Retransmit Timeout Mechanism (RTO), which is a timeout to prompt a retransmission of unacknowledged data. The timeout length is based on a running average of the Round Trip Time (RTT) for acknowledgment receipt, i.e. if an acknowledgment is not received within (typically) the smoothed RTT+4*mean deviation, then packet loss is inferred and the data pending acknowledgment is retransmitted.
Data rate flow control mechanisms which are operative end-to-end without explicit data rate control draw a strong inference of congestion from packet loss (inferred, typically, by RTO). TCP end systems, for example, will “back-off”, i.e., inhibit transmission in increasing multiples of the base RTT average as a reaction to consecutive packet loss.
Bandwidth Management in TCP/IP Networks
Conventional bandwidth management in TCP/IP networks is accomplished by a combination of TCP end systems and routers which queue packets and discard packets when certain congestion thresholds are exceeded. The discarded, and therefore unacknowledged, packet serves as a feedback mechanism to the TCP transmitter. (TCP end systems are clients or servers running the TCP transport protocol, typically as part of their operating system.) The term “bandwidth management” is often used to refer to link level bandwidth management, e.g. multiple line support for Point to Point Protocol (PPP). Link level bandwidth management is essentially the process of keeping track of all traffic and deciding whether an additional dial line or ISDN channel should be opened or an extraneous one closed. The field of this invention is concerned with network level bandwidth management, i.e. policies to assign available bandwidth from a single logical link to network flows.
In a copending U.S. patent application Ser. No. 08/742,994, now U.S. Pat. No. 6,038,216, in the name of Robert L. Packer, entitled “Method for Explicit Data Rate Control in a Packet Communication Environment Without Data Rate Supervision,” a technique for automatically scheduling TCP packets for transmission is disclosed. Furthermore, in U.S. Pat. No. 5,802,106, in the name of Robert L. Packer, entitled “Method for Rapid Data Rate Detection in a Packet Communication Environment Without Data Rate Supervision,” a technique for automatically determining the data rate of a TCP connection is disclosed. Finally, in a copending U.S. Pat. application Ser. No. 08/977,376, now abandoned, in the name of Robert L. Packer, entitled “Method for Managing Flow Bandwidth Utilization at Network, Transport and Application Layers in Store and Forward Network,” a technique for automatically allocating bandwidth based upon data rates of TCP connections according to a hierarchical classification paradigm is disclosed.
Automated tools assist the network manager in configuring and managing the network equipped with the rate control techniques described in these copending applications. In a related copending application, a tool is described which enables a network manager to automatically produce policies for traffic being automatically detected in a network. It is described in a copending U.S. patent application Ser. No. 09/198,051, still pending, in the name of Guy Riddle, entitled “Method for Automatically Determining a Traffic Policy in a Packet Communications Network”, based on U.S. Provisional Patent Application Ser. No. 60/066,864. The subject of the present invention is also a tool designed to assist the network manager.
While these efforts teach methods for solving problems associated with scheduling transmissions, automatically determining data flow rate on a TCP connection, allocating bandwidth based upon a classification of network traffic and automatically determining a policy, respectively, there is no teaching in the prior art of methods for automatically classifying packet traffic based upon info
Packer Robert L.
Riddle Guy
Allen Kenneth R.
Barot Bharat
Maung Zarni
Packeteer, Inc.
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