PLCA Collision Emulation for 10BASE-T1P PTP Timing
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Solution Overview
Problem
Conventional 10SPE networks face limitations in node count due to fundamental constants in physical level collision avoidance (PLCA), leading to variable delays that render precision time protocol (PTP) functionality unusable, especially when dealing with a large number of nodes or time-sensitive PTP packets.
Innovation Solution
Emulating collisions by asserting a collision signal when the transmit FIFO buffer is full or a PTP packet is detected, allowing the MAC to wait until a transmit opportunity, thereby preventing variable delays and enabling PTP packet transmission without FIFO buffering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PLCA is used in conventional 10SPE networks, then collision avoidance is achieved, but the number of nodes is limited due to fundamental constants
Solution Approach 1:
The patent emulates collision signals by asserting the collision signal line when the transmit FIFO buffer is full or when PTP packets are detected, creating a virtual copy of the collision mechanism that enables more nodes without physical changes to the PLCA protocol
Solution Approach 2:
The patent changes the behavior of the collision signal by making it responsive to buffer full conditions and PTP packet detection rather than only physical collisions, thereby modifying the system parameters to support more nodes while maintaining collision avoidance
2Reliability
If PLCA is used in conventional 10SPE networks, then collision avoidance is achieved, but variable delays occur that render PTP functionality unusable
Solution Approach 1:
The patent emulates collisions in advance by asserting the collision signal when the transmit FIFO buffer is full or when PTP packets are detected, preventing variable delays from occurring in the first place and ensuring deterministic timing for PTP packets
Solution Approach 2:
The patent introduces feedback mechanisms where the collision signal is asserted based on buffer full conditions and PTP packet detection, creating a closed-loop system that prevents variable delays by responding to current system state
3Quantity of substance
If the number of nodes is increased in 10SPE networks, then network capacity is improved, but collision detection becomes more difficult
Solution Approach 1:
The patent creates a virtual copy of the collision detection mechanism by emulating collisions through software control of the collision signal line, allowing accurate collision detection even in networks with a large number of nodes without physical modifications
Data Source
AI summary
Various embodiments relate to wired local area networks. A method may include detecting, at a node in a wired local area network, at least one event. A physical layer device of the network node is configured to implement a physical level collision avoidance (PLCA) sublayer. The at least one event may include at least one of an amount of data stored in a first-in-first-out (FIFO) buffer of the node being at least a threshold amount, and a received packet being a precision time protocol (PTP) packet incurring variable delay. The method may further include emulating a collision at the node in response to the at least one detected event.