Multiplex communications – Communication techniques for information carried in plural... – Combining or distributing information via time channels
Reexamination Certificate
2000-03-07
2004-02-24
Vanderpuye, Kenneth (Department: 2661)
Multiplex communications
Communication techniques for information carried in plural...
Combining or distributing information via time channels
C370S519000, C370S508000
Reexamination Certificate
active
06697382
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to networking and switching systems; and more particularly, the invention relates to distributing and synchronizing a representation of time between components of a packet switching system.
BACKGROUND OF THE INVENTION
The communications industry is rapidly changing to adjust to emerging technologies and ever increasing customer demand. This customer demand for new applications and increased performance of existing applications is driving communications network and system providers to employ networks and systems having greater speed and capacity (i.e., greater bandwidth). In trying to achieve these goals, a common approach taken by many communications providers is to use packet switching technology. Packet technology typically allows a plurality of information types to be transmitted over the same transmission lines and using the same packet switching systems and devices.
As used herein, the term “packet” refers to generically addressable packets of all types, including, but not limited to, fixed length cells and variable length packets. Moreover, these packets may contain one or more types of information, including, but not limited to, voice, data, video, and audio information. Furthermore, the term “system” is used generically herein to describe any number of components, packet switches, networks, computer and/or communication devices or mechanisms, or combinations thereof Packet switching systems can comprise many different components, with many of these components having their own independent clocks and independent counters representing a current value of time. In certain systems, it is important that the time counters of these components be synchronized; that is, each of the time counters reflect substantially the same time (within some small tolerance). Prior approaches to synchronize the clocks of the various components rely a common reset line or broadcast bus. However, such approaches are not applicable to systems which do not have a common reset line or broadcast bus. Desired are improved methods and systems for synchronizing a representation of time between components of a packet switching system.
SUMMARY OF THE INVENTION
Systems, apparatus and methods are disclosed for synchronizing a representation of a global time among components of a packet switching system. In one embodiment, the method for synchronizing a first time counter of a first component of a packet switching system with a second time counter of a second component of the packet switching system, where the first and second components are interconnected by one or more links, includes determining a message delay between the first and second components. The second component sends a time synchronization message to the first component. The time synchronization message including a time value of the second time counter. The first component receives the time synchronization message and updates its time counter based on the time value of the second time counter received in the time synchronization message and the determined message delay.
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David L. Mills, “Simple Network Time Protocol (SNTP) Version 4 for IPv4, IPv6 and OSI,” RFC 2030, Oct. 1996, 20 pages.
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Cisco Technology Inc.
The Law Office of Kirk D. Williams
Vanderpuye Kenneth
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