Distributed CAC Module for Optical Packet-Switched Metro WDM Slotted-Ring Networks
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Solution Overview
Problem
Existing metro networks, particularly SONET/SDH ring networks, are inefficient in handling variable bit rate (VBR) data services due to wasted network resources and long connection establishment times, lacking flexibility in bandwidth allocation for isochronous traffic, which affects quality of service (QoS) guarantees.
Innovation Solution
A medium access control (MAC) device and method for optical packet-switched metro WDM slotted-ring networks featuring a distributed call admission control (CAC) module that uses a mean-rate-reservation method to flexibly allocate reserved bandwidth for isochronous traffic, along with a remaining quota allocation module that determines unreserved traffic transmission based on probabilistic quota and credits, ensuring fair bandwidth allocation and QoS.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a centralized CAC mechanism is used to establish connections with reserved bandwidth, then QoS guarantees for isochronous traffic are improved, but connection establishment time increases and network flexibility decreases
Solution Approach 1:
The patent segments the CAC mechanism from centralized to distributed, placing CAC functionality at each node independently. This allows parallel connection establishment across multiple nodes simultaneously, reducing overall connection establishment time while maintaining QoS guarantees through local bandwidth assessment and reservation.
Solution Approach 2:
The patent implements preliminary bandwidth reservation through token-like signals that are broadcast in advance. The CAC module pre-assesses available bandwidth and reserves it before actual data transmission begins, enabling faster connection establishment without compromising QoS guarantees for isochronous traffic.
2Reliability
If fixed bandwidth allocation is used for source-destination pairs, then QoS guarantees are improved, but network adaptability and flexibility deteriorate
Solution Approach 1:
The patent transforms fixed bandwidth allocation into dynamic allocation through the distributed CAC mechanism. Each node's CAC module continuously monitors available bandwidth and dynamically adjusts reservations based on current network conditions, traffic demands, and slot availability, maintaining QoS guarantees while adapting to changing network states.
Solution Approach 2:
The patent changes the bandwidth allocation parameter from fixed to variable by implementing mean-rate-reservation methods. The system adjusts reservation rates dynamically based on traffic characteristics, allowing flexible adaptation to different service requirements while maintaining QoS guarantees through probabilistic bandwidth allocation.
3Reliability
If reserved bandwidth is allocated for each source-destination pair, then service quality is improved, but network resource utilization efficiency decreases
Solution Approach 1:
The patent makes bandwidth reservations universal by allowing the same bandwidth resources to serve multiple source-destination pairs through statistical multiplexing. The distributed CAC mechanism enables shared bandwidth allocation where resources are reserved probabilistically for different traffic flows based on their mean rates, improving overall resource utilization while maintaining service quality through QoS guarantees.
Solution Approach 2:
The patent changes bandwidth allocation from dedicated fixed amounts to probabilistic mean-rate reservations. This allows network resources to be efficiently shared across multiple connections while maintaining service quality through statistical multiplexing and dynamic adjustment of reservation parameters based on actual traffic patterns.
4Reliability
If bandwidth is marked whenever high priority data cannot be sent, then QoS for high priority traffic is improved, but bandwidth for low priority traffic is compressed
Solution Approach 1:
The patent implements a feedback mechanism where the distributed CAC module continuously monitors bandwidth usage and connection establishment success rates. Based on this feedback, the system dynamically adjusts bandwidth reservations and slot allocations to balance QoS guarantees for high priority traffic with adequate resource availability for low priority traffic, preventing excessive bandwidth compression.
Data Source
AI summary
A medium access control (MAC) device and method for optical packet-switched metro wavelength division multiplexing (WDM) slotted-ring networks are used for providing quality of service (QoS) guarantees for isochronous traffic. The device includes a MAC processor and a distributed call admission control (CAC) module. The CAC module in each node of an optical packet-switched network is designed in a distributed manner, and flexibly allocates a reserved bandwidth to an isochronous traffic by a mean-rate-reservation method, controls a quota of the isochronous traffic below a quota ratio rH, resolves output contention by recording node locations forming a connection, and establishes a connection for each isochronous traffic. The MAC processor establishes a connection in the reserved bandwidth for each isochronous traffic between the nodes according to control information carried in a control channel, controls uploading, unloading, and erasing of a plurality of data channels, and updates corresponding contents in the control information.