Abstract: A network device organizes packets into various queues, in which the packets await processing. Queue management logic tracks how long certain packet(s), such as a designated marker packet, remain in a queue. Based thereon, the logic produces a measure of delay for the queue, referred to herein as the “queue delay.” Based on a comparison of the current queue delay to one or more thresholds, various associated delay-based actions may be performed, such as tagging and/or dropping packets departing from the queue, or preventing addition enqueues to the queue. In an embodiment, a queue may be expired based on the queue delay, and all packets dropped. In other embodiments, when a packet is dropped prior to enqueue into an assigned queue, copies of some or all of the packets already within the queue at the time the packet was dropped may be forwarded to a visibility component for analysis.

Abstract: Approaches, techniques, and mechanisms are disclosed for efficiently buffering data units within a network device. A traffic manager or other network device component receives Transport Data Units (“TDUs”), which are sub-portions of Protocol Data Units (“PDUs”). Rather than buffer an entire TDU together, the component divides the TDU into multiple Storage Data Units (“SDUs”) that can fit in SDU buffer entries within physical memory banks. A TDU-to-SDU Mapping (“TSM”) memory stores TSM lists that indicate which SDU entries store SDUs for a given TDU. Physical memory banks in which the SDUs are stored may be grouped together into logical SDU banks that are accessed together as if a single bank. The TSM memory may include a number of distinct TSM banks, with each logical SDU bank having a corresponding TSM bank. Techniques for maintaining inter-packet and intra-packet linking data compatible with such buffers are also disclosed.

Abstract: A network device implements a foldable ingress buffer for buffering data units as they are being received. The buffer is organized into a grid of memory banks, having different columns and rows. A Transport Data Unit (“TDU”) is stored interleaved across entries in multiple banks. As each portion of a TDU is received, the portion is written to a different bank of the buffer. In each column of the buffer, a full-sized TDU has portions in a number of rows equal to the number of folds in the buffer. The sum of the bank widths for each row thus needs be no larger than half the maximum TDU size, which further means that the number of columns in the grid of banks may be reduced by at least half compared to non-folded approaches, with little increase in the number of rows, if any, depending on blocking and reading requirements.

Abstract: Link data is stored in a distributed link descriptor memory (“DLDM”) including memory instances storing protocol data unit (“PDU”) link descriptors (“PLDs”) or cell link descriptors (“CLDs”). Responsive to receiving a request for buffering a current transfer data unit (“TDU”) in a current PDU, a current PLD is accessed in a first memory instance in the DLDM. It is determined whether any data field designated to store address information in connection with a TDU is currently unoccupied within the current PLD. If no data field designated to store address information in connection with a TDU is currently unoccupied within the current PLD, a current CLD is accessed in a second memory instance in the plurality of memory instances of the same DLDM. Current address information in connection with the current TDU is stored in an address data field within the current CLD.

Abstract: A scheduler in a network device serves ports with data units from a plurality of queues. The scheduler implements a scheduling algorithm that is normally constrained to releasing data to a port no more frequently than at a default maximum service rate. However, when data units smaller than a certain size are at the heads of one or more data unit queues assigned to a port, the scheduler may temporarily increase the maximum service rate of that port. The increased service rate permits fuller realization of a port's maximum bandwidth when handling smaller data units. In some embodiments, increasing the service rate involves dequeuing more than one small data unit at a time, with the extra data units temporarily stored in a port FIFO. The scheduler adds a pseudo-port to its scheduling sequence to schedule release of data from the port FIFO, with otherwise minimal impact on the scheduling logic.

Abstract: A network device organizes packets into various queues, in which the packets await processing. Queue management logic tracks how long certain packet(s), such as a designated marker packet, remain in a queue. Based thereon, the logic produces a measure of delay for the queue, referred to herein as the “queue delay.” Based on a comparison of the current queue delay to one or more thresholds, various associated delay-based actions may be performed, such as tagging and/or dropping packets departing from the queue, or preventing addition enqueues to the queue. In an embodiment, a queue may be expired based on the queue delay, and all packets dropped. In other embodiments, when a packet is dropped prior to enqueue into an assigned queue, copies of some or all of the packets already within the queue at the time the packet was dropped may be forwarded to a visibility component for analysis.

Abstract: When a measure of buffer space queued for garbage collection in a network device grows beyond a certain threshold, one or more actions are taken to decreasing an enqueue rate of certain classes of traffic, such as of multicast traffic, whose reception may have caused and/or be likely to exacerbate garbage-collection-related performance issues. When the amount of buffer space queued for garbage collection shrinks to an acceptable level, these one or more actions may be reversed. In an embodiment, to more optimally handle multi-destination traffic, queue admission control logic for high-priority multi-destination data units, such as mirrored traffic, may be performed for each destination of the data units prior to linking the data units to a replication queue. If a high-priority multi-destination data unit is admitted to any queue, the high-priority multi-destination data unit can no longer be dropped, and is linked to a replication queue for replication.

Abstract: Network chip utility is improved using multi-core architectures with auxiliary wiring between cores to permit cores to utilize components from otherwise inactive cores. The architectures permit, among other advantages, the re-purposing of functional components that reside in defective or otherwise non-functional cores. For instance, a four-core network chip with certain defects in three or even four cores could still, through operation of the techniques described herein, be utilized in a two or even three-core capacity. In an embodiment, the auxiliary wiring may be used to redirect data from a Serializer/Deserializer (“SerDes”) block of a first core to packet-switching logic on a second core, and vice-versa. In an embodiment, the auxiliary wiring may be utilized to circumvent defective components in the packet-switching logic itself. In an embodiment, a core may utilize buffer memories, forwarding tables, or other resources from other cores instead of or in addition to its own.

Abstract: Approaches, techniques, and mechanisms are disclosed for efficiently buffering data units within a network device. A traffic manager or other network device component receives Transport Data Units (“TDUs”), which are sub-portions of Protocol Data Units (“PDUs”). Rather than buffer an entire TDU together, the component divides the TDU into multiple Storage Data Units (“SDUs”) that can fit in SDU buffer entries within physical memory banks. A TDU-to-SDU Mapping (“TSM”) memory stores TSM lists that indicate which SDU entries store SDUs for a given TDU. Physical memory banks in which the SDUs are stored may be grouped together into logical SDU banks that are accessed together as if a single bank. The TSM memory may include a number of distinct TSM banks, with each logical SDU bank having a corresponding TSM bank. Techniques for maintaining inter-packet and intra-packet linking data compatible with such buffers are also disclosed.

Abstract: Multiple ports of a network device are muxed together to form a single packed ingress interface into a buffer. A multiplexor alternates between the ports in alternating input clock cycles. Extra logic and wiring to provide a separate writer for each port is avoided, since the packed interface and buffer writers operate at higher speeds and/or have more bandwidth than the ports, and are thus able to handle incoming data for all of the ports coupled to the packed ingress interface. A packed ingress interface may also or instead support receiving data for multiple data units (e.g. multiple packets) from a single port in a single clock cycle, thereby reducing the potential to waste bandwidth at the end of data units. The interface may send the ending segments of the first data unit to the buffer. However, the interface may hold back the starting segments of the second data unit in a cache.

Abstract: Approaches, techniques, and mechanisms are disclosed for reutilizing discarded link data in a buffer space for buffering data units in a network device. Rather than wasting resources on garbage collection of such link data when a data unit is dropped, the link data is used as a free list that indicates buffer entries in which new data may be stored. In an embodiment, operations of the buffer may further be enhanced by re-using the discarded link data as link data for a new data unit. The link data for a formerly buffered data unit may be assigned exclusively to a new data unit, which uses the discarded link data to determine where to store its constituent data. As a consequence, the discarded link data actually serves as valid link data for the new data unit, and new link data need not be generated for the new data unit.

Abstract: Approaches, techniques, and mechanisms are disclosed for efficiently buffering data units within a network device. A traffic manager or other network device component receives Transport Data Units (“TDUs”), which are sub-portions of Protocol Data Units (“PDUs”). Rather than buffer an entire TDU together, the component divides the TDU into multiple Storage Data Units (“SDUs”) that can fit in SDU buffer entries within physical memory banks. A TDU-to-SDU Mapping (“TSM”) memory stores TSM lists that indicate which SDU entries store SDUs for a given TDU. Physical memory banks in which the SDUs are stored may be grouped together into logical SDU banks that are accessed together as if a single bank. The TSM memory may include a number of distinct TSM banks, with each logical SDU bank having a corresponding TSM bank. Techniques for maintaining inter-packet and intra-packet linking data compatible with such buffers are also disclosed.

Abstract: When a measure of buffer space queued for garbage collection in a network device grows beyond a certain threshold, one or more actions are taken to decreasing an enqueue rate of certain classes of traffic, such as of multicast traffic, whose reception may have caused and/or be likely to exacerbate garbage-collection-related performance issues. When the amount of buffer space queued for garbage collection shrinks to an acceptable level, these one or more actions may be reversed. In an embodiment, to more optimally handle multi-destination traffic, queue admission control logic for high-priority multi-destination data units, such as mirrored traffic, may be performed for each destination of the data units prior to linking the data units to a replication queue. If a high-priority multi-destination data unit is admitted to any queue, the high-priority multi-destination data unit can no longer be dropped, and is linked to a replication queue for replication.

Abstract: A network device organizes packets into various queues, in which the packets await processing. Queue management logic tracks how long certain packet(s), such as a designated marker packet, remain in a queue. Based thereon, the logic produces a measure of delay for the queue, referred to herein as the “queue delay.” Based on a comparison of the current queue delay to one or more thresholds, various associated delay-based actions may be performed, such as tagging and/or dropping packets departing from the queue, or preventing addition enqueues to the queue. In an embodiment, a queue may be expired based on the queue delay, and all packets dropped. In other embodiments, when a packet is dropped prior to enqueue into an assigned queue, copies of some or all of the packets already within the queue at the time the packet was dropped may be forwarded to a visibility component for analysis.

Abstract: A network device organizes packets into various queues, in which the packets await processing. Queue management logic tracks how long certain packet(s), such as a designated marker packet, remain in a queue. Based thereon, the logic produces a measure of delay for the queue, referred to herein as the “queue delay.” Based on a comparison of the current queue delay to one or more thresholds, various associated delay-based actions may be performed, such as tagging and/or dropping packets departing from the queue, or preventing addition enqueues to the queue. In an embodiment, a queue may be expired based on the queue delay, and all packets dropped. In other embodiments, when a packet is dropped prior to enqueue into an assigned queue, copies of some or all of the packets already within the queue at the time the packet was dropped may be forwarded to a visibility component for analysis.

Abstract: Efficient garbage collection techniques for network packets and other units of data are described. Constituent portions of a data unit are stored in buffer entries spread out across multiple distinct banks. Linking data is generated and stored on a per-bank basis. The linking data defines, for each bank in which data for the data unit is stored, a chain of all entries in that bank that store data for the data unit. When the data unit is dropped or otherwise disposed of, a chain's head entry address may be placed in a garbage collection list for the corresponding bank. A garbage collector uses the linking data to gradually follow the chain of entries for the given bank, and frees each entry in the chain along the way. Optionally, certain addresses in the chain, including each chain's tail address, are immediately freed for the corresponding bank, without waiting to follow the chain.

Abstract: A network device organizes packets into various queues, in which the packets await processing. Queue management logic tracks how long certain packet(s), such as a designated marker packet, remain in a queue. Based thereon, the logic produces a measure of delay for the queue, referred to herein as the “queue delay.” Based on a comparison of the current queue delay to one or more thresholds, various associated delay-based actions may be performed, such as tagging and/or dropping packets departing from the queue, or preventing addition enqueues to the queue. In an embodiment, a queue may be expired based on the queue delay, and all packets dropped. In other embodiments, when a packet is dropped prior to enqueue into an assigned queue, copies of some or all of the packets already within the queue at the time the packet was dropped may be forwarded to a visibility component for analysis.

Abstract: A network device organizes packets into various queues, in which the packets await processing. Queue management logic tracks how long certain packet(s), such as a designated marker packet, remain in a queue. Based thereon, the logic produces a measure of delay for the queue, referred to herein as the “queue delay.” Based on a comparison of the current queue delay to one or more thresholds, various associated delay-based actions may be performed, such as tagging and/or dropping packets departing from the queue, or preventing addition enqueues to the queue. In an embodiment, a queue may be expired based on the queue delay, and all packets dropped. In other embodiments, when a packet is dropped prior to enqueue into an assigned queue, copies of some or all of the packets already within the queue at the time the packet was dropped may be forwarded to a visibility component for analysis.

Abstract: Techniques for more optimally balancing operations across a set of buffers, such as in buffering packets in a network device or in other contexts, are disclosed. The techniques make use of an ordered list of buffers from which the next available buffer is selected for each operation, as needed. The buffers are first prioritized based on the state(s) of the relevant buffers and/or other factors. The resulting ordered list is then processed using re-ordering logic. This re-ordering logic may, for example, randomly or pseudo-randomly trade the positions of various sets of buffers within the prioritized list. Among other effects, the re-ordering logic thus reduces buffer skew problems from delayed propagation of buffer state information and other issues. In an embodiment, the re-ordering logic is divided into multiple levels of processing, with each level separately passing through the list. Each level of processing may utilize differently configured re-ordering logic.