Variable Length Coding for Source Routed Multicast Headers
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Solution Overview
Problem
Source routed forwarding solutions for multicast traffic are inefficient due to the fixed size header label approach, which limits the size of multicast trees and increases overhead, especially for large networks.
Innovation Solution
A centrally optimized variable length coding scheme is implemented, where a controller assigns unique variable-length codewords to represent links and nodes, allowing for a compact header representation that adapts based on the path and network topology, reducing the overhead and improving efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a fixed size header label approach (32 bits per label) is used for source routed multicast forwarding, then each link can be represented by a standardized header entry, but the header size increases linearly with the number of links traversed, limiting the size of multicast trees and increasing overhead
Solution Approach 1:
The patent applies dynamics by transitioning from a fixed-size header label approach to a variable-length codeword approach. Instead of using a constant 32 bits per label, the system uses codewords whose lengths vary based on the frequency of link occurrence in multicast trees. Frequently traversed links are assigned shorter codewords, while less frequent links receive longer codewords, making the header size dynamic rather than static.
Solution Approach 2:
The patent changes the parameter of header representation from fixed 32-bit labels to variable-length codewords. This parameter change allows the header to adapt its size based on the specific multicast tree being traversed. The controller optimizes codeword assignments based on traffic patterns, changing the length parameter of each link representation to minimize overall header size while maintaining the ability to represent any link in the network.
2Device complexity
If a fixed 32 bits per label stack entry is used, then the header format is simple and standardized, but this approach is not efficient for large multicast trees and limits the size of multicast trees that can be represented
Solution Approach 1:
The system makes the header format dynamic by using variable-length codewords instead of fixed 32-bit labels. This allows the header to adapt its structure based on the multicast tree size and topology. The controller dynamically assigns codeword lengths based on link frequency analysis, enabling efficient representation of both small and large multicast trees within the same framework.
Solution Approach 2:
The variable-length codeword system provides universality by being able to efficiently represent multicast trees of any size. Unlike fixed-size labels that become inefficient for large trees, the optimized codeword system adapts to different tree sizes and topologies, providing a universal solution that works efficiently for both small and large scale multicast deployments.
3Adaptability or versatility
If more links are traversed by each data packet, then the multicast tree coverage increases, but the header overhead increases proportionally, reducing forwarding efficiency
Solution Approach 1:
The patent changes the parameter of link representation from uniform fixed-size labels to variable-length codewords optimized based on traffic frequency. Links that are traversed more frequently are assigned shorter codewords, while less frequent links receive longer codewords. This parameter optimization reduces the average header size for packets traversing multiple links, improving forwarding efficiency while maintaining comprehensive multicast tree coverage.
Solution Approach 2:
The controller performs preliminary analysis of multicast traffic patterns and link frequency before assigning codewords. By pre-optimizing the codeword assignments based on expected traffic patterns, the system prepares the most efficient header format in advance, reducing the overhead for packets that will traverse multiple links without requiring real-time header optimization during packet forwarding.
Data Source
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AI summary
A system, controller and method having centrally optimized coding for a source routed forwarding based multicast network. The network comprises a plurality of nodes configured to transfer data packets to one another via a plurality of links. A controller is configured to control each of the nodes, and is configured to control forwarding of the data packets by establishing a header for each flow. The header defines a path for the flow of the data packets from a source to multiple destinations, wherein the length of the header is a function of the nodes and the branches in the path. The multicast path is represented as a header that consists of codewords representing interfaces, links and instructions. Some of the codewords are assigned different lengths in order to reduce the size of the header. Other codewords have a fixed size comprising a bit field.