MPLS Label Stacking for TDM Traffic Transport

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Solution Overview

Problem

Transporting real-time traffic over packet-switched networks, such as voice data, faces challenges in maintaining signal quality due to jitter, packet loss, and inefficient network utilization caused by excessive overhead from multiple protocols, which degrades the quality of service compared to circuit-switched lines.

Innovation Solution

The method involves encapsulating Time Division Multiplex (TDM) time slots in a data frame for packet-switched networks, using MPLS labels to ensure packets traverse the same route, reducing overhead by employing label-stacking and mapping tables to identify PCM systems, thereby maintaining quality similar to circuit-switched lines without increasing network capacity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If multiple protocols (RTP, UDP, IP, Ethernet) are used to transport real-time traffic, then routing and priority assignment functionality is enabled, but overhead increases by 20% or more degrading network utilization

Engineering Contradiction:

Improverouting and priority assignment capabilityVSAvoidnetwork capacity utilization

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The patent merges multiple protocol functionalities into a single MPLS label structure. The MPLS label combines routing information (label value for LSR lookup), QoS information (EXP bits for priority), and path identification (LSP designation) into one compact 4-byte header, replacing the cumulative overhead of RTP (16 bytes), UDP (8 bytes), IP (20 bytes), and Ethernet (14 bytes) protocols.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The MPLS label serves multiple functions simultaneously: it acts as a routing identifier for label-switched routers, a QoS marker with EXP bits for priority handling, a path identifier for label-switched paths, and a mechanism for traffic engineering. This multi-functionality eliminates the need for separate protocol layers.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Adaptability or versatility

If packets are routed through IP networks using traditional routing, then flexibility in path selection is achieved, but jitter and packet reordering occur due to different routes

Engineering Contradiction:

Improvepath selection flexibilityVSAvoidpacket delivery order and timing

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent segments the network into dedicated Label Switched Paths (LSPs) for different traffic types. Each LSP is a predetermined route established through MPLS signaling, ensuring that all packets for a given flow traverse the same path. This segmentation provides both reliability (consistent routing) and adaptability (different LSPs for different QoS requirements).

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The MPLS label is pre-configured with routing information before packet transmission. Label Switched Routers use this pre-established label-to-next-hop mapping to forward packets without real-time routing decisions, eliminating jitter and reordering while maintaining flexibility through pre-computed optimal paths.

Inventive Principle:

Principle #10Preliminary action

3Productivity

If TDM time slots are transported over packet-switched networks, then network consolidation and cost reduction are achieved, but signal quality degrades due to overhead and packet loss

Engineering Contradiction:

Improvenetwork capacity consolidationVSAvoidreal-time signal quality

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent changes the packaging parameters for TDM traffic by using fixed-size MPLS packets with predetermined label switching paths. This ensures consistent packetization intervals, predictable transmission timing, and minimized variable delay (jitter), maintaining real-time signal quality while enabling packet-switched network transport.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The MPLS label acts as an intermediary between TDM circuit-switched traffic and packet-switched network infrastructure. It provides a translation mechanism that preserves the deterministic characteristics of TDM while enabling transport over flexible packet networks, preventing packet loss and quality degradation.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS7864748B2Tunnelling TDM traffic over MPLS

Publication Date: 2011.01.04 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

The present invention provides a method for transporting TDM traffic through packet switched networks. The nodes of the packet switched network are MPLS adjusted, and the timeslots of a TDM connection are encapsulated in data frames in the transmitting circuit switched node, and added one or more MPLS label(s) by means of the MPLS label stacking concept to identify the fixed path through the packet switched network and to uniquely address the PCM system of the circuit switched receiving node. The present invention is particularly useful for transmission of real-time data traffic through IP network.