Ingress Line Card Path Selection in Packet Switch Fabrics
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Solution Overview
Problem
In SONET/SDH networks, existing technologies face challenges in efficiently selecting protected data paths within packet switch fabrics, which are unaware of the services they carry, leading to inefficient bandwidth usage and slow switch-over times.
Innovation Solution
The solution involves sharing line and path information between ingress line cards to enable protection selection through a packet switch fabric, using quality words to compare and determine the best path for data transmission, allowing flexible relationships between line cards and reducing bandwidth requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If egress protection selection is used to provide flexible protection associations, then adaptability is improved, but device complexity increases due to requiring extra fabric capacity to support switching of at least two paths to an egress line card
Solution Approach 1:
The patent performs path selection at the ingress line card before traffic enters the switch fabric. The ingress line card compares quality words from multiple source line cards and selects the best path in advance, eliminating the need for the fabric to support simultaneous switching of working and protection paths. This preliminary action reduces fabric capacity requirements while maintaining flexible protection associations.
2Adaptability or versatility
If central fabric selection is used to provide versatile protection, then adaptability is improved, but speed deteriorates because the fabric must be built with protocol awareness and the ability to detect and react to protection switches quickly
Solution Approach 1:
The patent extracts the path selection function from the central switch fabric and relocates it to the ingress line card. The ingress line card independently compares quality words and makes selection decisions without requiring the fabric to have protocol awareness or rapid detection capabilities. This separation improves switch-over speed while maintaining versatile protection.
3Device complexity
If ingress selection is used with fixed physical relationship between line cards, then device complexity is reduced, but adaptability deteriorates due to reliance on fixed physical relationships
Solution Approach 1:
The patent implements a universal quality word comparison mechanism at the ingress line card that works regardless of the physical relationship between line cards. The ingress line card can receive quality words from any source line card and select the best path based on quality metrics rather than fixed physical relationships. This provides flexible protection associations while keeping device complexity low.
Data Source
AI summary
Embodiments including methods, systems, and apparatuses for distributing, processing, and reacting to path information distributed via a service-agnostic packet fabric for the purpose of enabling path selection are disclosed. By configuring two ingress line cards to send path quality words to each other via the switch fabric, compare the path quality words, and determine whether to transmit traffic to an egress line card via the switch fabric based on the comparison of the path quality words, the embodiments enable a central switch fabric to be unaware of the paths that it carries, and enable both ingress and egress bandwidth of the switch fabric to be sized according to the facilities for which it is terminating. The switch fabric does not need to support working and protection paths simultaneously in some embodiments, allowing it to be scaled appropriately to termination facilities.