Optical communications – Multiplex – Hybrid
Reexamination Certificate
2000-03-23
2004-01-13
Chan, Jason (Department: 2633)
Optical communications
Multiplex
Hybrid
C398S068000, C398S071000, C398S098000, C398S099000
Reexamination Certificate
active
06678474
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a lightwave network data communications system, and more particularly to a communications system for connecting a subscriber-side network and a lightwave network in the form of performing multidimensional data communications via a large-scale basic network (which is hereinafter referred to as a lightwave network) utilizing a wavelength division multiplexing (WDM) technology.
2. Description of the Related Art
With a development and a spread of the Internet, a big problem to networking companies and communications common carriers in the Internet, is a rise in IP traffics. The traffics in the network are in the process of being unified in an IP platform, and in the meantime a fresh basic network topology suited to the IP traffics is now put into discussion. The IP traffics are on the verge of exceeding voice traffics, and a controversial point is that both of data and voices from respective homes and offices will be handled via IP lines in next one decade, wherein accounting might be based not on the time but on a data quantity.
Further, big corporations will shift long-distance lines to the IP network from the public switched telephone network (PSTN) in the year of 2000 or thereabouts, and it is predicted that the majority of network communications common carriers operating the core networks might purchase IP providers.
Thus, it is a high time to review how the telephone switched network mainly based on the existing voice traffics is located, and, with this opportunity, the communications carriers in the conventional fields move toward dealing with the IP traffics on the full scale, wherein it might be an urgent task to integrate the existing networks with the Internet.
Further, in the field of the network using the optical technologies, there is a jump advancement of structuring the network equipment adopting the WDM technology with concentration upon the markets in the North America, and it is said that the WDM will become dominant in the future optical communications.
The WDM is the technology for scheming an expansion of a transmission path capacity by multiplexing wavelengths of a plurality of carrier waves, and a quantity of the information transmitted via the optical fibers can be increased by leaps.
A transmission wavelength band of the optical fiber is sufficiently broad, however, the conventional time division multiplexing technology is incapable of fully using that wavelength band.
For example, even if 500 Gbit/sec is actualized on the TDMl channel, an occupying band thereof is 500 to 600 GHz (approximately 5 nm as a wavelength band) at the maximum. There is such a symptom that a further increase in the capacity by the TDM comes to a deadlock very soon, and the rapid progress which has been made so far can not be anticipated unless there appears a technical breakthrough.
An advantage of utilizing the WDM technology is that together with the larger increase in the capacity owing to the multiplexing, the transfer can be speeded up by a transparent transmission of a relay node, and a processing load upon the relay node can be relieved.
Further, according to a technology reported in “One Method of Actualizing Connectionless over ATM,” Ogawa, Masuda, et al., the Electronic Information Communications Association Technical Study Report SSE97-36, 1997, for attaining the speed-up and the further increase in the capacity in ATM connectionless intra-network routing, in an ATM connectionless network constructed of an edge router incorporating a gateway function to a core network and an intra-network core router, the edge router conceived to be smaller in scale than the intra-network core router aggregates protocol processes, and the intra-network core router does not execute software-based protocol processes but actualize all of these processes by hardware. Even the prior art described above, however, does not disclose at all a method by which the lightwave network accommodates the existing subscriber network, and the high-speed transfer is implemented.
According to the WDM, however, wavelength resources are limited, and hence it is not a realistic solution that a usage (Local Significant: VPI/VCI, etc. in ATM) such as allocating a wavelength to an end-to-end connection. Then, the standard organization OIF Optical Internetworking Forum) for the WDM-based transmission system of the IP data reviews the existing SDH layers, and there is a concept of a system (IP over WDM) for transferring the IP data directly on the WDM-based transmission path. This system is neither yet controversial nor comes to standardization thereof.
Further, in an all-optical network which is desired to be actualized in the future, the lightwave frames are only optically processed and routed, including a switching operation. A core technology needed for this routing is not the framing of the lightwave frame but related to a switching speed of the optical switch and actualization of a burst-receivable high-speed PLL (Phase Locked Loop).
What is particularly hard to actualize is the latter burst-receivable PLL, and, though desired to attain a drastic progress of the present technology, it may be adequate to use the switching technology involving an electrical process in the present technical situation.
Normally, a packet switch based on the electric process, however, effects switching on a minimum 64-bytes IP packet basis. Therefore in the case of the packet switch having an accommodated interface showing an interface speed on the order of, e.g., 2.4 Gbps, a switch scheduling judgement must be made within a time given such as 64 bytes×8 bits×1/2.4 Gbps=210 nsec. Hence, there exist drawbacks of being unable to follow up with a large-scale switch having a tera-level capacity in the future and of deficiency in terms of compatibility with the high-speed large-capacity network.
Moreover, Japanese Patent Application Laid-Open No. Hei 7-99483 discloses a technology relative to an optical communications system including a network controller for controlling in concentration allocation of time slots to a plurality of nodes in the communications between the plurality of nodes for transmitting and receiving the data by use of the time slots, wherein optical transmission channels for the respective wavelengths are each divided into a plurality of channels in the wavelength division multiplexing optical network. This technology is an invention contrived to obviate a problem in which the traffic is restricted by some nodes for transmitting a large quantity of data, and other nodes are incapable of ensuring a free time slot common to other transmitting destination nodes.
In the technology disclosed in the Publication described above, it is not a realistic solution that an allocation of the time slots is managed in concentration with respect to the individual IP flows occurred by several millions for one second, and an application to the high-speed large capacity has a drawback.
SUMMARY OF THE INVENTION
It is an object of the present invention, which was contrived under such circumstances, to provide a lightwave network communications system capable of simplifying a routing operation within a lightwave network in such a form as to perform multiplexing data communications through a large-scale basic network (hereinafter referred to as a lightwave network) utilizing particularly a wavelength division multiplexing (WDM) technology, matching an existing subscriber-side network with the lightwave network by aggregating IP flows and framing batchwise a plurality of packets each having a length less than a fixed length, and actualizing an efficient mutual connections therebetween without being restricted by a packet switching processing speed at present.
To accomplish the above object, the lightwave network data communications system according to the present invention includes a unit for introducing, with a light adaptation layer matched with a transfer within the lightwave network being defined, this lightwave adaptatio
Masuda Michio
Nishihara Motoo
Yamada Kenshin
Chan Jason
NEC Corporation
Tran Dzung
Young & Thompson
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