Robust link synchronization in ethernet networks
A first network interface device receives a first synchronization signal transmitted by a second network interface device via a communication link. The first synchronization signal is for synchronizing the first network interface device and the second network interface device via the communication link. In response to detecting the first synchronization signal from the second network interface device, the first network interface device starts a timer that is configured to expire after transmission of the first synchronization signal by the second network interface device has ended. In response to the timer expiring, the first network interface device transmits a synchronization response signal to the second network interface device.
1 . A method for synchronizing a first network interface device and a second network interface device via a wired communication link, the method comprising:
receiving, at the first network interface device, a first synchronization signal transmitted by the second network interface device via the wired communication link, the first synchronization signal to facilitate the first network device to discover the second network device and for synchronizing the first network interface device and the second network interface device via the wired communication link;
in response to detecting the first synchronization signal from the second network interface device, starting a timer of the first network interface device, the timer being configured to expire after transmission of the first synchronization signal by the second network interface device has ended; and
in response to the timer expiring, transmitting, by the first network interface device, a synchronization response signal to the second network interface device via the wired communication link to facilitate the second network device to discover the first network device, wherein transmitting the synchronization response signal in response to the timer expiring is to mitigate the second network device failing to detect the synchronization response signal due to transmission of the synchronization response signal overlapping in time with transmission of the first synchronization signal.
2 . The method of claim 1 , wherein:
a maximum duration of the first synchronization signal is defined by a communication protocol; and
the timer is configured to measure a time duration that is less than the maximum duration of the first synchronization signal.
3 . The method of claim 2 , wherein the timer is configured to take into account a delay between when reception of the first synchronization signal by the first network interface device begins and when the first network interface detects the first synchronization signal.
4 . The method of claim 2 , wherein the timer is configured to measure a time duration between 73% and 90% of the maximum duration of the first synchronization signal defined by the communication protocol.
5 . The method of claim 4 , wherein the timer is configured to measure a time duration between 75% and 85% of the maximum duration of the first synchronization signal defined by the communication protocol.
6 . The method of claim 5 , wherein the timer is configured to measure a time duration between 75% and 80% of the maximum duration of the first synchronization signal defined by the communication protocol.
7 . The method of claim 2 , wherein:
the communication protocol defines the maximum duration of the first synchronization signal as 1.3 μs; and
the timer is configured to measure a time duration of approximately 1 μs.
8 . The method of claim 1 , further comprising:
after transmitting the synchronization response signal, receiving at the first network device a second synchronization signal from the second network interface device; and
after receiving the second synchronization signal, transmitting, by the first network interface device, a plurality of additional synchronization response signals to the second network interface device until a minimum number of synchronization response signals are transmitted by the first network interface device to the second network interface device.
9 . The method of claim 8 , further comprising:
initializing a send synchronization signal counter at the first network interface device; and
incrementing the send synchronization signal counter for each transmission of a respective synchronization response signals to the second network interface device;
wherein transmitting the plurality of additional synchronization response signals comprises transmitting additional synchronization response signals until the send synchronization signal counter reaches a fixed predetermined number corresponding to the minimum number of synchronization response signals.
10 . The method of claim 8 , wherein transmitting synchronization response signals includes pausing transmission after respective ones of synchronization response signals, among the synchronization response signals, for a duration of a pause time.
11 . A communication device, comprising:
a first network interface device configured to communicatively couple with a second network interface device via a wired communication link, the first network interface device comprising a physical layer (PHY) processor, implemented at least partially on one or more integrated circuit (IC) chips, the PHY processor including a timer implemented on the one or more IC chips, the one or more IC chips being configured to:
receive a first synchronization signal transmitted by the second network interface device via the wired communication link, the first synchronization signal to facilitate the first network interface device to discover the second network interface device and for synchronizing the first network interface device and the second network interface device via the wired communication link,
in response to detecting the first synchronization signal from the second network interface device, start the timer of the first network interface device, the timer being configured to expire after transmission of the first synchronization signal by the second network interface device has ended, and
in response to the timer expiring, control the first network interface device to transmit a synchronization response signal to the second network interface device via the wired communication link to facilitate the second network interface device to discover the first network interface device, wherein transmitting the synchronization response signal in response to the timer expiring is to mitigate the second network interface device failing to detect the synchronization response signal due to transmission of the synchronization response signal overlapping in time with transmission of the first synchronization signal.
12 . The communication device of claim 11 , wherein:
a maximum duration of the first synchronization signal is defined by a communication protocol; and
the timer is configured to measure a time duration that is less than the maximum duration of the first synchronization signal.
13 . The communication device of claim 12 , wherein the timer is configured to take into account a delay between when reception of the first synchronization signal by the first network interface device begins and when the first network interface detects the first synchronization signal.
14 . The communication device of claim 12 , wherein the timer is configured to measure a time duration between 73% and 90% of the maximum duration of the first synchronization signal defined by the communication protocol.
15 . The communication device of claim 14 , wherein the timer is configured to measure a time duration between 75% and 85% of the maximum duration of the first synchronization signal defined by the communication protocol.
16 . The communication device of claim 15 , wherein the timer is configured to measure a time duration between 75% and 80% of the maximum duration of the first synchronization signal defined by the communication protocol.
17 . The communication device of claim 12 , wherein:
the communication protocol defines the maximum duration of the first synchronization signal as 1.3 μs; and
the timer is configured to measure a time duration of approximately 1 μs.
18 . The communication device of claim 11 , wherein the one or more IC chips are further configured to:
after the first network interface device transmits the synchronization response signal, receive a second synchronization signal from the second network interface device; and
after receiving the second synchronization signal, control the first network interface device to transmit a plurality of additional synchronization response signals to the second network interface device until a minimum number of synchronization response signals are transmitted by the first network interface device to the second network interface device.
19 . The communication device of claim 18 , wherein:
the PHY processor further includes a send synchronization signal counter implemented on the one or more IC chips; and
the one or more IC chips are further configured to:
initialize the send synchronization signal counter,
increment the send synchronization signal counter for each transmission of a respective synchronization response signals to the second network interface device, and
transmit the additional synchronization response signals until the send synchronization signal counter reaches a fixed predetermined number corresponding to the minimum number of synchronization response signals.
20 . The communication device of claim 18 , wherein the one or more IC chips are further configured to:
pause transmission by the first network interface device after transmission of respective ones of synchronization response signals, among the synchronization response signals, for a duration of a pause time.