The present invention relates to digital computer network technology. More specifically, it relates to methods and apparatus for restoring traffic within an access network.
Broadband access technologies such as cable, fiber optic, and wireless have made rapid progress in recent years. Recently there has been a convergence of voice and data networks which is due in part to United States deregulation of the telecommunications industry. In order to stay competitive, companies offering broadband access technologies need to support voice, video, and other high-bandwidth applications over their local access networks. For networks that use a shared access medium to communicate between subscribers and the service provider (e.g., cable networks, wireless networks, etc.), providing reliable high-quality voice/video communication over such networks is not an easy task.
One type of broadband access technology relates to cable modem networks. A cable modem network or “cable plant” employs cable modems, which are an improvement of conventional PC data modems and provide high speed connectivity. Cable modems are therefore instrumental in transforming the cable system into a full service provider of video, voice and data telecommunications services.
A head end complex and cable modem typically communicate. This communication may be one-way or two-way between the cable modem and head end complex. In one way communication, the cable modem merely receives data from the head end complex, but cannot transmit data to the head end complex. For example, the cable modem cannot request particular types of data from the head end complex. In two-way communication, the cable modem can transmit data (e.g., data requests) to the head end complex.
There are circumstances that may interfere with the communication between a cable Head End and a cable modem. As one example, there may be a hardware failure of the cable Head End. As another example, there may be a software failure within the cable Head End. As yet another example, there may be a power outage that causes communication between the cable Head End and the cable modem to be disrupted.
In order to ensure that communication between a cable Head End and a cable modem has not been interrupted, a handshake is typically exchanged between the cable Head End and the cable modem. More particularly, this handshake is typically initiated by the cable Head End. Thus, when the cable modem does not receive a communication from the cable Head End within a period of time, the cable modem declares a time out.
When a time out occurs, the cable modem initiates a new connection with the cable Head End. Unfortunately, this new connection takes time to establish. For instance, it may take up to 24 seconds to rebuild a connection between a cable modem and its cable Head End.
In the event that a cable Head End fails, it would be undesirable to abruptly disconnect the modem from the cable Head End to re-initiate a connection. This is particularly undesirable when real-time traffic such as voice or video data is being transmitted. Even if the connection were merely delayed, such a substantial delay during a real-time transmission such as a phone call is unacceptable.
In view of the above, it would be desirable to prevent a time out of a cable modem when a cable Head End fails. Moreover, it would be desirable if the effects of a time out could be minimized.