Virtually-Concatenated Traffic Routing for Fast SONET Restoration

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Solution Overview

Problem

Conventional restoration techniques in SONET/SDH networks face challenges in achieving fast restoration of data traffic after route failure due to excessive bandwidth overhead and delays in the LCAS protocol, which limits their effectiveness in providing 50 millisecond fast restoration and makes them inefficient for use with virtually-concatenated data traffic.

Innovation Solution

The development of improved routing algorithms that determine routes for virtually-concatenated data traffic to minimize bandwidth impact and facilitate fast restoration by incorporating backup members with diverse routing, allowing for low-overhead, standards-compliant restoration techniques, which include configuring a virtually-concatenated group with primary and backup members and utilizing a modified LCAS protocol to quickly switch data traffic in case of route failure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of time

If conventional 1+1 primary-backup protection is used in SONET/SDH networks, then fast restoration (less than 50 milliseconds) is achieved, but bandwidth overhead increases to 100%

Engineering Contradiction:

Improverestoration timeVSAvoidbandwidth overhead

Core Design Contradiction:

Loss of timeVSQuantity of substance

Solution Approach 1:

Instead of providing full backup protection for all traffic (100% bandwidth overhead), the patent applies partial protection by selectively providing backup only when needed and sharing backup resources among multiple primary routes. This allows achieving fast restoration for critical traffic while reducing overall bandwidth overhead through shared backup capacity.

Inventive Principle:

Principle #16Partial or excessive action

Solution Approach 2:

The patent merges multiple backup routes into a shared backup infrastructure where a single backup route can serve multiple primary routes. This consolidation reduces the total backup bandwidth required from 100% (conventional 1+1 protection) to significantly less, while maintaining fast restoration capability through coordinated switching.

Inventive Principle:

Principle #5Merging (Combining)

2Adaptability or versatility

If LCAS protocol is used for virtual concatenation, then flexible bandwidth adjustment is enabled, but restoration delay increases to 64-128 milliseconds

Engineering Contradiction:

Improvebandwidth adjustment flexibilityVSAvoidrestoration delay

Core Design Contradiction:

Adaptability or versatilityVSLoss of time

Solution Approach 1:

The patent pre-configures multiple alternative routes and backup paths before failures occur, so that when a failure happens, the switching decision can be made immediately without waiting for LCAS protocol processing. The backup infrastructure is prepared in advance, allowing restoration to begin before LCAS refresh cycles complete.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces an intermediary switching mechanism that operates independently of or alongside the LCAS protocol. This intermediary enables fast restoration by directly switching traffic between primary and backup routes without being constrained by LCAS's refresh timing mechanism, thus achieving sub-50ms restoration while maintaining LCAS's bandwidth adjustment capabilities.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Device complexity

If Ethernet layer protection (rapid spanning tree) is used for EoS data traffic, then restoration is provided without SONET/SDH layer protection, but data traffic disruption increases to several seconds

Engineering Contradiction:

Improveprotection implementation simplicityVSAvoidrestoration time

Core Design Contradiction:

Device complexityVSLoss of time

Solution Approach 1:

The patent replaces the slow Ethernet layer switching mechanism (spanning tree) with a faster SONET/SDH layer switching mechanism. By operating at the synchronous transport level, the system achieves restoration times in the 50-millisecond range or less, compared to several seconds at the Ethernet layer, while maintaining the simplicity of protection configuration.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS7518990B2Route determination method and apparatus for virtually-concatenated data traffic

Publication Date: 2009.04.14 WSOU INVESTMENTS LLC

AI summary

Virtually-concatenated data traffic is routed in a network comprising at least first and second nodes. The first and second nodes may comprise a source-sink node pair, an ingress-egress node pair, or any other pair of network nodes. For a given traffic demand, a plurality of routes for routing the traffic demand through the network are determined. Each of the routes corresponds to a member of a virtually-concatenated group, such that different portions of the traffic demand are assigned to different members of the virtually-concatenated group.