Direction-switchable transponders

#Social networking systems enable a very large number of users (e.g., a billion users or more) to share data worldwide. To support this data sharing, the social networking systems have multiple data centers that are distributed around the world. The multiple data centers enable the data to be distributed worldwide, e.g., to back up data or to store data near where the data will be consumed. Each of these data centers typically has a very large number of server computing devices. The server computing devices may be assigned various roles, e.g., compute, data storage, web site, etc.

#Data centers may be built and geographically located based on various requirements and constraints. Data centers in developed countries can be large, where power and land are available. In countries where power and land are less available or there is a regulation concern, data centers may be smaller. Because larger data centers are easier to manage and provide superior scalability, they are preferred and tend to be built in a handful of locations. On the other hand, for flexibility and nimbleness, small data centers are preferred and they are built in many places wherever there are users of the social networking system. As a result, the infrastructure for a social networking systems may have various sizes of data centers that are geographically dispersed.

#Content providers and, e.g., streaming video content providers, similarly build large data centers and can locate them near consumers of their content. They may also use services of content delivery networks to deliver content. These content delivery networks also have geographically dispersed data centers.

#FIG. 1 is a block diagram illustrating an environment in which a direction-switchable transponder may be employed, consistent with various embodiments.

#FIGS. 2A, 2B, 2C, and 2D are block diagrams illustrating aspects of high speed communications lines, consistent with various embodiments.

#FIG. 3 is a flow diagram illustrating processing of a reconfiguration signal, consistent with various embodiments.

#The disclosure is directed to a direction-switchable transponder. In optical communications networks, e.g., fiber optic networks, a transponder can convert or generate various wavelengths of light that is propagated along a fiber optic cable. Various light wavelengths can be used to transmit or receive data. In dense wavelength division multiplexing (DWDM), which is a physical optical layer protocol for exchanging data, multiple “channels” are used to transmit or receive data in parallel on a single fiber or on two fibers (“fiber pair”). Typically, most or all channels on a first fiber of a circuit are used to transmit data and most or all channels on a second fiber of the circuit are used to receive data. Each channel uses a different wavelength of light. Presently, up to 96 channels can co-exist on a single pair of fibers. The number of channels can vary across manufacturers of transponders or other optical networking equipment. Transponders are typically configured at installation time to transmit or receive data on channels in a particular direction (e.g., between a sender and a receiver), which effectively “clamps” bandwidth in a particular direction based on how many channels are configured to transmit data in that particular direction. When symmetric bandwidth needs are anticipated, an equal number of channels may be configured in each direction of a fiber optic cable: e.g., 48 channels in one direction and 48 channels in the opposite direction. When asymmetric bandwidth needs are anticipated, an unequal number of channels may be configured in each direction: e.g., 12 channels for receiving requests in one direction of a fiber optic cable 36 channels for transmitting responses in the opposite direction of the fiber optic cable, and 48 channels for transmitting responses on a different fiber optic cable or the same fiber optic cable. Thus, there may be a total of 12 channels for requests and 84 channels for responses.

#The direction-switchable (also referred to sometimes as direction-modifiable) transponder is capable of receiving a signal and dynamically and automatically reconfiguring channels in response to that signal. The signal can be received via a “back channel,” e.g., via Ethernet, I2C, or indeed any signaling mechanism. The signal can also be received via one of the DWDM channels, e.g., a channel reserved for signaling various communications equipment that are part of the data communications network. The signal can indicate a change in bandwidth needs. In various embodiments, the signal can indicate how many channels to assign to a particular direction, which channels to assign to a particular direction, or how much bandwidth is presently required or anticipated to be required in a particular direction.

#In response to receiving the signal, the direction-switchable transponder reconfigures its channels. If the received signal specifies the number of channels to assign to a particular direction, the direction-switchable transponder determines which channels need to be reconfigured and automatically reconfigures those channels. As an example, the direction-switchable transponder may attempt to reconfigure the fewest number of channels or channels that are presently under-utilized. In various embodiments, the direction-switchable transponder may communicate the reconfiguration to other direction-switchable transponders on the same circuit so that those transponders can appropriately reconfigure themselves to send or receive data.