Monitoring of connection between network devices in a packet-based communication system

A method of controlling the rate of transmission of data between a first network station and a second network station connected by way of a transmission link, wherein both the first and second stations are capable of receiving and transmitting data in the form of data packets, at any one of a defined plurality of standard data rates, said data rates comprising at least a higher data rate and a lower data rate, and wherein said first station includes an auto-negotiation state machine for determining whether data is to be transmitted between the stations at the said higher rate or the said lower rate, said auto-negotiation state machine executing an auto-negotiation sequence in accordance with IEEE standard 802.3, clause 28, and including an auto-negotiation expansion register for the indication of a ‘page received’ bit in accordance with said standard, said method comprising:

• monitoring occurrences of said ‘page received’ bit in said auto-negotiation expansion register to count repetitions of said auto-negotiation sequence;
• and
• causing the data rate for said link to be established at the lower rate if the count of repetitions of said auto-negotiation sequence exceeds a threshold.