Link training with multiple hops

A method for performing link training over a plurality of hops between host network devices, the method comprising:

• performing, by a first intermediate network device among one or more intermediate network devices, link training on a first network link, the first network link extending between the first intermediate network device and a first host network device, the performing of the link training on the first network link including synchronizing respective one or more first transmit clocks at the one or more intermediate network devices with a transmit clock of the first host network device;
• performing, by the first intermediate network device or by a second intermediate network device among the one or more intermediate network devices, link training on a second network link, the second network link extending between i) either the first intermediate network device or the second intermediate network device and ii) a second host network device, the performing of the link training on the second network link including synchronizing respective one or more second transmit clocks at the one or more intermediate network devices with a transmit clock of the second host network device;
• transmitting, by the one or more intermediate network devices, respective link training completion indications to the first host network device and the second host network device, including delaying one or more of the respective link training completion indications until both i) the respective one or more first transmit clocks are synchronized with the transmit clock of the first host network device and i) the respective one or more second transmit clocks are synchronized with the transmit clock of the second host network device.

An active cable assembly, comprising:

• a first intermediate network device having a first interface configured to couple with a first host network device via a first network link that extends between the first intermediate network device and the first host network device, the first intermediate network device including a first link training controller configured to perform link training on the first network link with the first host device;
• a second intermediate network device having a second interface configured to couple with a second host network device via a second network link that extends between the second intermediate network device and the second host network device, the second intermediate network device including a second link training controller configured to perform link training on the second network link;
• and
• a third network link between the first intermediate network device and second the intermediate network device;
• the first link training controller of the first intermediate network device being further configured to:
• perform link training on the third network link prior to i) the first link training controller performing link training on the first network link and i) the second link training controller performing link training on the second network link, and
• determine when link training of the first network link and the second network link has been completed,
• transmit a first link training completion indication to the first host network device, and
• delay transmission of the first link training completion indication until link training of both the first network link and the second network link has been completed;
• and
• the second link training controller of the second intermediate network device being further configured to:
• determine when link training of the first network link and the second network link has been completed,
• transmit a second link training completion indication to the second host network device;
• and
• delay transmission of the second link training completion indication until link training of both the first network link and the second network link has been completed.

An active cable assembly, comprising:

• one or more intermediate network devices, wherein a respective intermediate network device among the one or more intermediate network devices includes i) a first interface configured to couple with a first host network device directly or via one or more upstream intermediate network devices and i) a second interface configured to couple with a second host network device directly or via one or more downstream intermediate network devices;
• and
• one or more link training controllers implemented by the one or more intermediate network devices, the one or more link training controllers configured to:
• perform link training on a first network link, the first network link extending between a first intermediate network device and a first host network device,
• during link training on the first network link, synchronize respective one or more first transmit clocks at the one or more intermediate network devices with a transmit clock of the first host network device,
• perform link training on a second network link, the second network link extending between i) either the first intermediate network device or a second intermediate network device and ii) a second host network device,
• during link training on the second network link, synchronize respective one or more second transmit clocks at the one or more intermediate network devices with a transmit clock of the second host network device,
• determine when link training of the first network link and the second network link has been completed,
• transmit respective link training completion indications to the first host network device and to the second host network device, and
• delay one or more of the respective link training completion indications until both i) the respective one or more first transmit clocks are synchronized with the transmit clock of the first host network device and i) the respective one or more second transmit clocks are synchronized with the transmit clock of the second host network device.