WO2018002688A1

WO2018002688A1 - Head drop scheduler

Info

Publication number: WO2018002688A1
Application number: PCT/IB2016/053836
Authority: WO
Inventors: Daniel Christian Biederman; Ravi Tangirala; Srivathsa DHRUVANARAYAN
Original assignee: Telefonaktiebolaget LM Ericsson AB
Current assignee: Telefonaktiebolaget LM Ericsson AB
Priority date: 2016-06-27
Filing date: 2016-06-27
Publication date: 2018-01-04
Anticipated expiration: 2018-12-27

Abstract

A method and system to select a queue from which to discard a first data packet where there are insufficient storage resources in a queue data storage. The queue data storage includes a set of queues for at least one port of a network device. The method includes determining a guaranteed bandwidth for each queue in the set of queues for the at least one port, determining a depth for each queue of the set of queues and whether the depth is above a threshold minimum depth value, receiving at least a portion of a second data packet, and determining there is insufficient space in the queue data storage to store the received portion of the second data packet. A queue is selected from the set of queues to discard the first data packet where the selected queue is a lowest priority queue that meets or if no queue exceeds the threshold minimum depth value, selecting a lowest priority queue from queues that do not exceed the threshold minimum depth value, and the first data packet is discarded from the selected queue.

Description

HEAD DROP SCHEDULER

TECHNICAL FIELD

[0001] Embodiments of the invention relate to the field of queue management; and more specifically, to the process of selecting an item to drop from a set of queues when the set of queues are full or exceed a threshold storage.

BACKGROUND

[0002] Various devices utilize a set of queues or similar storage structures to hold data to be processed in a given order. Many queues are managed such that the data stored in the queues is processed in a first in and first out (FIFO) method where the data is handled in the order it is received. Queues can be managed with other methods where the data stored in a queue is handled with varying sequences such as last in first out (LIFO) where the most recently added data is processed first. The queues are often considered to have a 'head' and a 'tail.' The head of the queue is generally a pointer to the next data item to be processed from the queue.

Similarly, a tail is generally a pointer to the last data item that was placed into the queue to be processed.

[0003] Queues have a wide applicability and use in the field of computer devices. One common area where queues are utilized are in network devices to handle the processing of inbound and outbound data packets. Queues often serve to manage the order in which data is processed, in particular where there is more data to be processed then a processor can handle at a given moment. In this case the queue is used to manage the order in which the data is processed as the processor resources become free. In the network device context, data packets to be processed may be received by the network device faster than they can be processed by the network device processor or similarly the network device processor may queue up data packets to be transmitted on an outbound port where the port or the transmission medium is not able to immediately transfer the data packet.

[0004] Queues however have a finite size, if the data throughput exceeds the processing speed of a network processor or port, for example, then the data being added to a set of queues will eventually exceed the space available in the queues. In such a case a decision must be made by a scheduler or similar queue manager to determine what data will be 'dropped' or lost due to the lack of space in the queue. This may occur when the queues are full or above any threshold storage level. Various processes for selecting data to be dropped have been devised dependent on the application and priorities associated with the data being processed. In some simple scenarios newly received data is dropped or the oldest data in the queue is dropped. In cases such as in many network devices, where there is a set of queues a selection process must select which of the queues to drop data from and into which newly received data is to be placed.

Selection of one out of a set of queues can be by simple round robin selection or similar mechanisms. Many algorithms exist for the scheduling and management of data in queues, which are typically optimized for a given type of data, device and task.

SUMMARY

[0005] In one embodiment, a method is implemented by a network device. The method selects a queue from which to discard a first data packet where there are insufficient storage resources in a queue data storage. The queue data storage includes a set of queues for at least one port of the network device. The method determines a guaranteed bandwidth for each queue in the set of queues for the at least one port, and determines a depth for each queue of the set of queues and whether the depth is above a threshold minimum depth value. The method receives at least a portion of a second data packet, determines there is insufficient space in the queue data storage to store the received portion of the second data packet, and selects a queue from the set of queues to discard the first data packet where the selected queue is a lowest priority queue that meets or if no queue exceeds the threshold minimum depth value, selecting a lowest priority queue from queues that do not exceed the threshold minimum depth value. The first data packet is then discarded from the selected queue.

[0006] In another embodiment, a network device executes the method for selecting a queue from which to discard a first data packet where there are insufficient storage resources in a queue data storage. The queue data storage includes a set of queues for at least one port of the network device. The network device includes a non-transitory computer-readable medium having stored therein a buffer manager, and a processor coupled to the non-transitory computer- readable medium. The processor executes the buffer manager. The buffer manager determines a guaranteed bandwidth for each queue in the set of queues for the at least one port, determines a depth for each queue of the set of queues and whether the depth is above a threshold minimum depth value, receives at least a portion of a second data packet, determines there is insufficient space in the queue data storage to store the received portion of the second data packet, selects a queue from the set of queues to discard the first data packet where the selected queue is a lowest priority queue that meets or if no queue exceeds the threshold minimum depth value, selecting a lowest priority queue from queues that do not exceed the threshold minimum depth value, and discards the first data packet from the selected queue. [0007] In a further embodiment, a computing device implements a plurality of virtual machines for implementing network function virtualization (NFV), wherein a virtual machine from the plurality of virtual machines is configured to execute the method for selecting a queue from which to discard a first data packet where there are insufficient storage resources in a queue data storage. The queue data storage includes a set of queues for at least one port of the computing device. The computing device includes a non-transitory computer-readable medium (548) having stored therein a buffer manager, and a processor coupled to the non- transitory computer-readable medium. The processor executes a virtual machine from the plurality of virtual machines. The virtual machine executes the buffer manager. The buffer manager determines a guaranteed bandwidth for each queue in the set of queues for the at least one port, determines a depth for each queue of the set of queues and whether the depth is above a threshold minimum depth value, receives at least a portion of a second data packet, determines there is insufficient space in the queue data storage to store the received portion of the second data packet, selects a queue from the set of queues to discard the first data packet where the selected queue is a lowest priority queue that meets or if no queue exceeds the threshold minimum depth value, selecting a lowest priority queue from queues that do not exceed the threshold minimum depth value, and discards the first data packet from the selected queue.

[0008] In another embodiment, a control plane device implements at least one centralized control plane for a software defined networking (SDN) network. The centralized control plane executes a method for selecting a queue from which to discard a first data packet where there are insufficient storage resources in a queue data storage. The queue data storage includes a set of queues for at least one port of the control plane device. The control plane device includes a non- transitory computer-readable medium having stored therein a buffer manager, and a processor coupled to the non-transitory computer-readable medium. The processor executes the buffer manager. The buffer manager determines a guaranteed bandwidth for each queue in the set of queues for the at least one port, determines a depth for each queue of the set of queues and whether the depth is above a threshold minimum depth value, receives at least a portion of a second data packet, determines there is insufficient space in the queue data storage to store the received portion of the second data packet, selects a queue from the set of queues to discard the first data packet where the selected queue is a lowest priority queue that meets or if no queue exceeds the threshold minimum depth value, selecting a lowest priority queue from queues that do not exceed the threshold minimum depth value, and discards the first data packet from the selected queue. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The invention may best be understood by referring to the following description and accompanying drawings that are used to illustrate embodiments of the invention. In the drawings:

[0010] Figure 1 is a diagram of one embodiment of a network device including a set of queues and a buffer manager for those queues.

[0011] Figure 2 is a diagram of one embodiment of the buffer manager.

[0012] Figure 3 is a flowchart of one embodiment of the process of the buffer manager for queue prioritization.

[0013] Figure 4 is a flowchart of one embodiment of the process for queue selection.

[0014] Figure 5A illustrates connectivity between network devices (NDs) within an exemplary network, as well as three exemplary implementations of the NDs, according to some

embodiments of the invention.

[0015] Figure 5B illustrates an exemplary way to implement a special-purpose network device according to some embodiments of the invention.

[0016] Figure 5C illustrates various exemplary ways in which virtual network elements (VNEs) may be coupled according to some embodiments of the invention.

[0017] Figure 5D illustrates a network with a single network element (NE) on each of the NDs, and within this straight forward approach contrasts a traditional distributed approach (commonly used by traditional routers) with a centralized approach for maintaining reachability and forwarding information (also called network control), according to some embodiments of the invention.

[0018] Figure 5E illustrates the simple case of where each of the NDs implements a single NE, but a centralized control plane has abstracted multiple of the NEs in different NDs into (to represent) a single NE in one of the virtual network(s), according to some embodiments of the invention.

[0019] Figure 5F illustrates a case where multiple VNEs are implemented on different NDs and are coupled to each other, and where a centralized control plane has abstracted these multiple VNEs such that they appear as a single VNE within one of the virtual networks, according to some embodiments of the invention.

[0020] Figure 6 illustrates a general purpose control plane device with centralized control plane (CCP) software 650), according to some embodiments of the invention. DETAILED DESCRIPTION

[0021] The following description describes methods and apparatus for a buffer manager that uses the current state of each queue's depth, priority, and guaranteed bandwidth commitments to determine the optimal queue for dropping a data packet and avoid problems including priority leaks. The embodiments provide a method for packet drop arbitration in a data processing system having a memory and at least one network port that may be serviced by or sub-divided into at least two queues. The method determines an input queue from the plurality of input queues for which a packet should be dropped. The method determines a priority for each queue, and the guaranteed bandwidth status for each queue. Then it is determined whether each queue's depth was above a given threshold. A determination is further made of the queue with the lowest priority, that does not exceed the guaranteed bandwidth and meets the given threshold depth, from which a packet is dropped.

[0022] In the following description, numerous specific details such as logic implementations, opcodes, means to specify operands, resource partitioning/sharing/duplication implementations, types and interrelationships of system components, and logic partitioning/integration choices are set forth in order to provide a more thorough understanding of the present invention. It will be appreciated, however, by one skilled in the art that the invention may be practiced without such specific details. In other instances, control structures, gate level circuits and full software instruction sequences have not been shown in detail in order not to obscure the invention. Those of ordinary skill in the art, with the included descriptions, will be able to implement appropriate functionality without undue experimentation.

[0023] References in the specification to "one embodiment," "an embodiment," "an example embodiment," etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

[0024] Bracketed text and blocks with dashed borders (e.g., large dashes, small dashes, dot- dash, and dots) may be used herein to illustrate optional operations that add additional features to embodiments of the invention. However, such notation should not be taken to mean that these are the only options or optional operations, and/or that blocks with solid borders are not optional in certain embodiments of the invention. [0025] In the following description and claims, the terms "coupled" and "connected," along with their derivatives, may be used. It should be understood that these terms are not intended as synonyms for each other. "Coupled" is used to indicate that two or more elements, which may or may not be in direct physical or electrical contact with each other, co-operate or interact with each other. "Connected" is used to indicate the establishment of communication between two or more elements that are coupled with each other.

[0026] An electronic device stores and transmits (internally and/or with other electronic devices over a network) code (which is composed of software instructions and which is sometimes referred to as computer program code or a computer program) and/or data using machine-readable media (also called computer-readable media), such as machine-readable storage media (e.g., magnetic disks, optical disks, read only memory (ROM), flash memory devices, phase change memory) and machine-readable transmission media (also called a carrier) (e.g., electrical, optical, radio, acoustical or other form of propagated signals - such as carrier waves, infrared signals). Thus, an electronic device (e.g., a computer) includes hardware and software, such as a set of one or more processors coupled to one or more machine-readable storage media to store code for execution on the set of processors and/or to store data. For instance, an electronic device may include non-volatile memory containing the code since the non- volatile memory can persist code/data even when the electronic device is turned off (when power is removed), and while the electronic device is turned on that part of the code that is to be executed by the processor(s) of that electronic device is typically copied from the slower nonvolatile memory into volatile memory (e.g., dynamic random access memory (DRAM), static random access memory (SRAM)) of that electronic device. Typical electronic devices also include a set or one or more physical network interface(s) to establish network connections (to transmit and/or receive code and/or data using propagating signals) with other electronic devices. One or more parts of an embodiment of the invention may be implemented using different combinations of software, firmware, and/or hardware.

[0027] A network device (ND) is an electronic device that communicatively interconnects other electronic devices on the network (e.g., other network devices, end-user devices). Some network devices are "multiple services network devices" that provide support for multiple networking functions (e.g., routing, bridging, switching, Layer 2 aggregation, session border control, Quality of Service, and/or subscriber management), and/or provide support for multiple application services (e.g., data, voice, and video).

[0028] Figure 1 is a diagram of one embodiment of a network device in which a buffer manager may be implemented. In one embodiment, the embodiments of the process may be implemented by a network device 101 such as a router or similar network device. The network device 101 can have any structure that enables it to receive data traffic and forward it toward its destination. The network device 101 can include a network processor 103 or set of network processors that execute the functions of the network device 101. A 'set,' as used herein, is any positive whole number of items including one item. The network device 101 or network element can execute any combination of network functions and functionality via a network processor 103 or other components of the network device 101. The network functions can be implemented as modules in any combination of software, including firmware, and hardware within the network device 101.

[0029] In one embodiment, the network device 101 can include a set of line cards 117 that process and forward the incoming data traffic toward the respective destination nodes by identifying the destination and forwarding the data traffic to the appropriate line card 117 having an egress port that leads to or toward the destination via a next hop. These line cards 117 can also implement the routing information base (RIB) or forwarding information base (FIB) 105B, or a relevant subset thereof. The line cards 117 can also implement the buffer manager 151 that manages a set of queues holding data packets to be processed by the LI processors 113 or L2/L3 processor forwarding tables 115 as described further herein below. The line cards 117 are in communication with one another via a switch fabric 111 and communicate with other nodes over attached networks 121 using Ethernet, fiber optic or similar communication links and media.

[0030] In other embodiments, the processes can be implemented by a split-architecture node using software defined networking (SDN), where the control plane is remote from the data/forwarding plane. In this case, the buffer manager 151 processes can be carried out at any combination of the data plane nodes 101 and the central controller. In further embodiments, the processes can be implemented via network function virtualization (NFV) with some aspects of the processes for buffer management implemented at computing devices or network devices remote from the network device 101. The SDN and NFV architecture embodiments are provided as further example implementations herein below that are described with relation to Figures 5 and 6.

[0031] In the embodiment of Figure 1, the buffer manager 151 includes a set of queues that store data packets that are incoming or outbound data packets associated with the respective inbound or outbound ports attached to the line cards 117. The inbound or outbound data packets can be stored by the queues as they await processing by the line card 117 or transmission via the outbound ports. Where the queues are full or exceed a threshold level data packets may be selected to be dropped as set forth herein below. [0032] As described herein, operations performed by the network device may refer to specific configurations of hardware such as application specific integrated circuits (ASICs) configured to perform certain operations or having a predetermined functionality, or software instructions stored in memory embodied in a non-transitory computer readable storage medium. Thus, the techniques shown in the figures can be implemented using code and data stored and executed on one or more electronic devices (e.g., an end station, a network element). Such electronic devices store and communicate (internally and/or with other electronic devices over a network) code and data using computer -readable media, such as non-transitory computer -readable storage media (e.g., magnetic disks; optical disks; random access memory; read only memory; flash memory devices; phase-change memory) and transitory computer -readable communication media (e.g., electrical, optical, acoustical or other form of propagated signals - such as carrier waves, infrared signals, digital signals). In addition, such electronic devices typically include a set of one or more processors coupled to one or more other components, such as one or more storage devices (non-transitory machine-readable storage media), user input/output devices (e.g., a keyboard, a touchscreen, and/or a display), and network connections. The coupling of the set of processors and other components is typically through one or more busses and bridges (also termed as bus controllers). Thus, the storage device of a given electronic device typically stores code and/or data for execution on the set of one or more processors of that electronic device. One or more parts of an embodiment of the invention may be implemented using different combinations of software, firmware, and/or hardware.

[0033] Figure 2 is a diagram of one embodiment of a buffer manager within a network device. The buffer manager 200 can service or be tied to any number of input (or output ports). For sake of clarity the example is given where incoming data packets are queued by the buffer manager 200 before forwarding out of a line card toward the switch fabric 111. One skilled in the art would understand that the process implemented by the buffer manager 200 can be implemented to manage a set of queues for data packets destined for egress ports of the network device, or similar alternative circumstances where a set of queues may be utilized to manage the processing and forwarding of data packets.

[0034] In the example, the buffer manager 200 manages a queue data storage structure 203 that includes a set of buffers 1-N 209 A -209B. Each buffer 209 A - 209B includes a set of queues 211A-D. Thus for each input port 201 and buffer 209A - 209B there are at least two queues. In some embodiments, each queue 211A-D is associated with a rate limiter 213 that tracks the status of whether the queue has currently exceeded its individual threshold in data packet storage. This status can be expressed using any mechanism. In some example mechanisms, the status of the queue may be classified as red or green; red, yellow or green; full or not full; or similar categorization of the current level of occupancy for the queues 211A-D. The queues 211A-D may also be associated with a token bucket 215 or similar mechanism that is utilized to determine the order in which the queues are to be processed relative to one another.

[0035] The input datapath scheduler 221 utilizes the rate limiter data and token buckets of the queues 211A-D to select a next data packet from the queues 211A-D to process or where queue occupancy exceeds a threshold value, the input datapath scheduler can play a role in

implementing the queue selection process for determining which queue to drop a data packet from. The process can select a data packet at either the head end or tail end of a selected queue 211A-D dependent on the configuration or priorities of the process. Data packets selected for processing are forwarded in the example embodiment via an output port 205 to the switch fabric 111 of the network device. The organization of the buffer manager 200 is provided by way of example and not limitation; one skilled in the art would understand that the process described with relation to this example buffer manager and queue organization can be employed in any configuration or architecture where a set of queues, including at least two for a given port are present.

[0036] Where a network device 101 executes a process to select a packet to process there are varying options for the selection of the data packet referred to as winner scheduling where the process identifies which queues are prioritized and processed above other queues. Prior art processes include round robin selection, deficit weighted round robin and similar processes that can be used individually and in combination. Where there are packets of varying priorities, associated with guaranteed data flow bandwidth or similar characterizations this can be taken into account when selecting a winner.

[0037] Packet drop selection is implemented to do the opposite of winner scheduling where a packet is selected not to be processed, but to be dropped. This can be a head drop process in some embodiments. However, such packet drop algorithms can result in priority leaks, and hence packets that should not be dropped, may be dropped. A priority leak refers to the packet drop process causing lower priority packets to be processed where higher priority packets are dropped. This may be especially problematic when queues have a given required bandwidth restriction to meet. For example, in the cases where a low priority queue has a green or similar status indicating that it is below its storage threshold, or empty, and hence higher priority queues may be selected for drop if they are red or a similar status indicating high level of occupancy. Thus, low priority queues would steal bandwidth from the higher priority queues, causing the priority leak.

[0038] Thus the prior art algorithms suffer from priority leaks that cause low priority queues to steal the bandwidth of high priority queues. These leaks are non-obvious, unless the process is tested. In the prior art, generally, data packets that do not fit into the input buffers or queues are tail dropped. Tail dropped packets are the last packet(s) that cannot fit into the buffer. Tail-dropped packets could be high priority data packets or data packets from queues that have not met their guaranteed bandwidth. Thus, such tail dropping processes do not respect priority or bandwidth guarantees. The herein described embodiments overcome these deficiencies of the prior art. Head dropping packets allows the packet to be classified, such that priority, guaranteed bandwidth and other queue related characteristics can help determine the appropriate data packet from the appropriate queue to drop.

[0039] The embodiments require queues to have a certain threshold. Queues above that threshold would be dropped first. Such a process may be expressed in pseudocode and may look like this, where RR is round robin:

Amongst the inputs of the lowest priority (based on color and priority level) scheduler: If ( any inputs with depth > threshold ) {

RR amongst inputs

}

Else {

RR amongst all the inputs

}

This process can be further modified:

If ( any inputs with depth > threshold ) {

RR amongst the lowest priority inputs

}

Else {

RR amongst all the inputs

}

[0040] The second process allows queues to build up like a bell curve, where high priority packets are dequeued (i.e., they pass through the input data path), low priority packets are dropped, and the middle priority packets build up above the threshold, allowing for more time in the buffer, where they can be dequeued or dropped. This is the goal for the management of the queues. The embodiments can encompass any process that employs a round robin between the ports of equal priority and status. A minimum depth can be incorporated into the process where every queue or port has a minimum depth requirement. The minimum depth could be a minimum of a single packet.

[0041] The embodiments also encompass another important concept of guaranteed bandwidth. In many of the test cases/use cases, most, if not all ports, have a guaranteed bandwidth. If the low priority queues are empty, it is hard for the guaranteed bandwidth to be met quickly. Hence having one or more packets in the queue helps that queue meet its minimum bandwidth quickly. This guaranteed bandwidth concept also leads to priority leaks, if the low priority queue is empty, or it stays green (i.e., below its threshold) longer until it can send a packet to meets its bandwidth. If the queue has a bandwidth a little above its guaranteed bandwidth, the memory leak problem could be more pronounced. Having one or more packets available, removes the memory leak problem due to the ability to quickly drop a packet.

[0042] As mentioned above, prior art processes had priority leaks where high priority queues are passed, and few data packets are contained in the buffer. Likewise, low priority queues are dropped and few data packets are contained in the buffer, and hence most of the packets are in a middle priority queue. Only 1 packet could be in the second lowest priority queue and second highest priority queue, and the remaining packets could be in the middle priority queue. Hence the highest and lowest priority queues could be empty. If at that instance in time, a packet needs to be dropped, it would be dropped from the second highest priority queue, if it is the only red (i.e., above its threshold) queue. Hence a priority leak would exist. Note that even if the second highest priority queue was green, and the dropped packet was round-robin-ed between the queues that are green (e.g., including the second lowest priority queue and the middle priority queue), there is a 33% chance that the second highest priority packet would be dropped. Note that in this example the medium priority queue has the threshold maximum- 1 packets, as once the buffer contents go over the threshold maximum number of packets, a packet needs to be dropped.

[0043] The embodiments described herein overcome these priority leaks and problems with the prior art by providing a method and system where the input datapath scheduler 221 of a buffer manager 200 uses the current state of each of the queues depth, priority and guaranteed bandwidth to determine the optimal queue from which to drop a packet while avoiding priority leaks where the occupancy of the buffer is over a maximum threshold or where the buffer and its constituent queues are full. The embodiments provide an advantage over the prior art in reducing priority leaks due to dropping packets, causing lower priority data packets to be dropped instead of randomly dropping packets (e.g., as in tail drops). The embodiments drop packets from queues that have met their guaranteed bandwidth before dropping packets from queues that have not met their guaranteed bandwidths.

[0044] The operations in the flow diagrams will be described with reference to the exemplary embodiments of the other figures. However, it should be understood that the operations of the flow diagrams can be performed by embodiments of the invention other than those discussed with reference to the other figures, and the embodiments of the invention discussed with reference to these other figures can perform operations different than those discussed with reference to the flow diagrams.

[0045] Figure 3 is a diagram of one embodiment of the process for the buffer manager. The process is implemented by each buffer manager in a network device or similar manager of queues in a computing device. In some embodiments, the process in implemented by an input datapath scheduler or similar component of the buffer manager. The process begins by assessing the guaranteed bandwidth for each queue of the set of queues for at least one port (Bock 301). The port can be an input port where the data packets are being received to be processed by a line card or network device. The process continues by determining a depth for each queue of the set of queues and whether the depth is above a threshold minimum depth value (Block 303).

[0046] With this information ascertained, which may be done periodically or as there is any change in the occupancy of the buffer or the set of queues, a new data packet or a portion of a data packet may be received to be enqueued (Block 305). A check is made whether there is sufficient space in the queue data storage to enable the received data packet or portion of the data packet to be enqueued (Block 307). The check may be a total capacity or may be a check on whether a maximum occupancy threshold has been exceeded, which can have any value relative to the storage capacity of the queue data storage (Block 307). If there is sufficient data storage, then the process enqueues the data packet or the received portion of the data packet in one of the set of queues (not illustrated).

[0047] However, where there is not sufficient space in the queue data storage, the process for selecting a packet to be dropped to make room for the received data packet or the received portion of the data packet is engaged (Block 309). This process is described in greater detail with an example implementation in Figure 4. The process selects a queue from the set of queues to discard a data packet where the selected queue is a lowest priority queue that meets or if no queue exceeds the threshold minimum depth value, selecting a lowest priority queue from queues that do not exceed the threshold minimum depth value (Block 311). Where there are multiple queues that meet these criteria, then the process may use any tie-breaking or selection mechanism such as a round robin or similar selection mechanism. In some embodiments, if no queues meet these criteria then an alternate mechanism may be utilized to select a queue for dropping a data packet (Block 313). Such alternate mechanisms can reduce the criteria such as selecting a lowest priority queue, a queue that meets the threshold minimum depth value, a queue that does not exceed the guaranteed bandwidth or any combination or subset of these criteria below the full criteria. In further alternative embodiments, selection mechanisms such as round robin, weighted round robin or similar selection mechanisms may be utilized. Once the queue has been selected then the data packet can be dropped (Block 315). The data packet may be dropped from the head of the queue. In other embodiments, the data packet may be dropped from any location within the selected queue including the tail of the queue.

[0048] Figure 4 is a flowchart of one embodiment of the process for queue selection. The process for selecting a queue from which to drop a packet after the queue state and

characteristics are determined can be carried out in response to the receipt of a data packet or a portion of a data packet that is to be enqueued, but where there is insufficient storage in the queue data storage (Block 401). A check is first made whether there are any queues in the set of queues of the buffer in the queue data storage that are over the threshold minimum depth value (Block 403). If there are not any queues over the threshold minimum depth value, then a check is made whether any queue in the set of queues exceeds a guaranteed bandwidth (Block 407). If no queue exceeds the guaranteed bandwidth, then a queue is selected that is within the guaranteed bandwidth (Block 411). If there is a queue that exceeds the guaranteed bandwidth, then the process selects the lowest priority queue that exceeds the guaranteed bandwidth

(Block 409).

[0049] Where the process did find queues over the threshold minimum depth value

(Block 403), then the process determines whether any queue is over its respective guaranteed bandwidth (Block 405). If there is at least one queue over its guaranteed bandwidth, then the process selects the lowest priority queue that exceeds its guaranteed bandwidth (Block 415). However, if there were no queues that are over their respective guaranteed bandwidths, then the process selects the lowest priority queue that is within its guaranteed bandwidth (Block 413). In each case, once the queue has been selected then the process drops a data packet from the selected queue (Block 417). The examples have been given with the enqueueing and dropping of single packets, however, in other embodiments, the process may enqueue and drop packets or portions of packets in a set of any size or composition.

[0050] Alternate Architectural Implementations

[0051] Figure 5A illustrates connectivity between network devices (NDs) within an exemplary network, as well as three exemplary implementations of the NDs, according to some

embodiments of the invention. Figure 5A shows NDs 500A-H, and their connectivity by way of lines between 500A-500B, 500B-500C, 500C-500D, 500D-500E, 500E-500F, 500F-500G, and 500A-500G, as well as between 500H and each of 500A, 500C, 500D, and 500G. These NDs are physical devices, and the connectivity between these NDs can be wireless or wired (often referred to as a link). An additional line extending from NDs 500A, 500E, and 500F illustrates that these NDs act as ingress and egress points for the network (and thus, these NDs are sometimes referred to as edge NDs; while the other NDs may be called core NDs). [0052] Two of the exemplary ND implementations in Figure 5 A are: 1) a special-purpose network device 502 that uses custom application-specific integrated-circuits (ASICs) and a special-purpose operating system (OS); and 2) a general purpose network device 504 that uses common off-the-shelf (COTS) processors and a standard OS.

[0053] The special-purpose network device 502 includes networking hardware 510 comprising compute resource(s) 512 (which typically include a set of one or more processors), forwarding resource(s) 514 (which typically include one or more ASICs and/or network processors), and physical network interfaces (NIs) 516 (sometimes called physical ports), as well as non- transitory machine readable storage media 518 having stored therein networking software 520. A physical NI is hardware in a ND through which a network connection (e.g., wirelessly through a wireless network interface controller (WNIC) or through plugging in a cable to a physical port connected to a network interface controller (NIC)) is made, such as those shown by the connectivity between NDs 500A-H. During operation, the networking software 520 may be executed by the networking hardware 510 to instantiate a set of one or more networking software instance(s) 522. Networking software 520 can include a buffer manager 564A-R that implements the functions described herein above with regard to queue selections and data packet discarding. Each of the networking software instance(s) 522, and that part of the networking hardware 510 that executes that network software instance (be it hardware dedicated to that networking software instance and/or time slices of hardware temporally shared by that networking software instance with others of the networking software instance(s) 522), form a separate virtual network element 530A-R. Each of the virtual network element(s)

(VNEs) 530A-R includes a control communication and configuration module 532A-R

(sometimes referred to as a local control module or control communication module) and forwarding table(s) 534A-R, such that a given virtual network element (e.g., 530A) includes the control communication and configuration module (e.g., 532A), a set of one or more forwarding table(s) (e.g., 534A), and that portion of the networking hardware 510 that executes the virtual network element (e.g., 530A).

[0054] The special-purpose network device 502 is often physically and/or logically considered to include: 1) a ND control plane 524 (sometimes referred to as a control plane) comprising the compute resource(s) 512 that execute the control communication and configuration

module(s) 532A-R; and 2) a ND forwarding plane 526 (sometimes referred to as a forwarding plane, a data plane, or a media plane) comprising the forwarding resource(s) 514 that utilize the forwarding table(s) 534A-R and the physical NIs 516. By way of example, where the ND is a router (or is implementing routing functionality), the ND control plane 524 (the compute resource(s) 512 executing the control communication and configuration module(s) 532A-R) is typically responsible for participating in controlling how data (e.g., packets) is to be routed (e.g., the next hop for the data and the outgoing physical NI for that data) and storing that routing information in the forwarding table(s) 534A-R, and the ND forwarding plane 526 is responsible for receiving that data on the physical NIs 516 and forwarding that data out the appropriate ones of the physical NIs 516 based on the forwarding table(s) 534A-R.

[0055] Figure 5B illustrates an exemplary way to implement the special-purpose network device 502 according to some embodiments of the invention. Figure 5B shows a special- purpose network device including cards 538 (typically hot pluggable). While in some embodiments the cards 538 are of two types (one or more that operate as the ND forwarding plane 526 (sometimes called line cards), and one or more that operate to implement the ND control plane 524 (sometimes called control cards)), alternative embodiments may combine functionality onto a single card and/or include additional card types (e.g., one additional type of card is called a service card, resource card, or multi-application card). A service card can provide specialized processing (e.g., Layer 4 to Layer 7 services (e.g., firewall, Internet Protocol Security (IPsec), Secure Sockets Layer (SSL) / Transport Layer Security (TLS), Intrusion Detection System (IDS), peer-to-peer (P2P), Voice over IP (VoIP) Session Border Controller, Mobile Wireless Gateways (Gateway General Packet Radio Service (GPRS) Support Node (GGSN), Evolved Packet Core (EPC) Gateway)). By way of example, a service card may be used to terminate IPsec tunnels and execute the attendant authentication and encryption algorithms. These cards are coupled together through one or more interconnect mechanisms illustrated as backplane 536 (e.g., a first full mesh coupling the line cards and a second full mesh coupling all of the cards).

[0056] Returning to Figure 5A, the general purpose network device 504 includes hardware 540 comprising a set of one or more processor(s) 542 (which are often COTS processors) and network interface controller(s) 544 (NICs; also known as network interface cards) (which include physical NIs 546), as well as non-transitory machine readable storage media 548 having stored therein software 550. During operation, the processor(s) 542 execute the software 550 to instantiate one or more sets of one or more applications, including buffer manager 564A-R. While one embodiment does not implement virtualization, alternative embodiments may use different forms of virtualization. For example, in one such alternative embodiment the virtualization layer 554 represents the kernel of an operating system (or a shim executing on a base operating system) that allows for the creation of multiple instances 562A-R called software containers that may each be used to execute one (or more) of the sets of applications such as buffer manager 564A-R; where the multiple software containers (also called virtualization engines, virtual private servers, or jails) are user spaces (typically a virtual memory space) that are separate from each other and separate from the kernel space in which the operating system is run; and where the set of applications running in a given user space, unless explicitly allowed, cannot access the memory of the other processes. In another such alternative embodiment the virtualization layer 554 represents a hypervisor (sometimes referred to as a virtual machine monitor (VMM)) or a hypervisor executing on top of a host operating system, and each of the sets of applications, such as buffer manager 564A-R, is run on top of a guest operating system within an instance 562A-R called a virtual machine (which may in some cases be considered a tightly isolated form of software container) that is run on top of the hypervisor - the guest operating system and application may not know they are running on a virtual machine as opposed to running on a "bare metal" host electronic device, or through para- virtualization the operating system and/or application may be aware of the presence of virtualization for optimization purposes. In yet other alternative embodiments, one, some or all of the

applications are implemented as unikernel(s), which can be generated by compiling directly with an application only a limited set of libraries (e.g., from a library operating system (LibOS) including drivers/libraries of OS services) that provide the particular OS services needed by the application. As a unikernel can be implemented to run directly on hardware 540, directly on a hypervisor (in which case the unikernel is sometimes described as running within a LibOS virtual machine), or in a software container, embodiments can be implemented fully with unikernels running directly on a hypervisor represented by virtualization layer 554, unikernels running within software containers represented by instances 562A-R, or as a combination of unikernels and the above-described techniques (e.g., unikernels and virtual machines both run directly on a hypervisor, unikernels and sets of applications that are run in different software containers).

[0057] The instantiation of the one or more sets of one or more applications such as buffer manager 564A-R, as well as virtualization if implemented, are collectively referred to as software instance(s) 552. Each set of applications including buffer manager 564A-R, corresponding virtualization construct (e.g., instance 562A-R) if implemented, and that part of the hardware 540 that executes them (be it hardware dedicated to that execution and/or time slices of hardware temporally shared), forms a separate virtual network element(s) 560A-R.

[0058] The virtual network element(s) 560A-R perform similar functionality to the virtual network element(s) 530A-R - e.g., similar to the control communication and configuration module(s) 532A and forwarding table(s) 534A (this virtualization of the hardware 540 is sometimes referred to as network function virtualization (NFV)). Thus, NFV may be used to consolidate many network equipment types onto industry standard high volume server hardware, physical switches, and physical storage, which could be located in Data centers, NDs, and customer premise equipment (CPE). While embodiments of the invention are illustrated with each instance 562A-R corresponding to one VNE 560A-R, alternative embodiments may implement this correspondence at a finer level granularity (e.g., line card virtual machines virtualize line cards, control card virtual machine virtualize control cards, etc.); it should be understood that the techniques described herein with reference to a correspondence of instances 562A-R to VNEs also apply to embodiments where such a finer level of granularity and/or unikernels are used.

[0059] In certain embodiments, the virtualization layer 554 includes a virtual switch that provides similar forwarding services as a physical Ethernet switch. Specifically, this virtual switch forwards traffic between instances 562A-R and the NIC(s) 544, as well as optionally between the instances 562A-R; in addition, this virtual switch may enforce network isolation between the VNEs 560A-R that by policy are not permitted to communicate with each other (e.g., by honoring virtual local area networks (VLANs)).

[0060] The third exemplary ND implementation in Figure 5A is a hybrid network device 506, which includes both custom ASICs/special-purpose OS and COTS processors/standard OS in a single ND or a single card within an ND. In certain embodiments of such a hybrid network device, a platform VM (i.e., a VM that that implements the functionality of the special-purpose network device 502) could provide for para- virtualization to the networking hardware present in the hybrid network device 506.

[0061] Regardless of the above exemplary implementations of an ND, when a single one of multiple VNEs implemented by an ND is being considered (e.g., only one of the VNEs is part of a given virtual network) or where only a single VNE is currently being implemented by an ND, the shortened term network element (NE) is sometimes used to refer to that VNE. Also in all of the above exemplary implementations, each of the VNEs (e.g., VNE(s) 530A-R, VNEs 560A-R, and those in the hybrid network device 506) receives data on the physical NIs (e.g., 516, 546) and forwards that data out the appropriate ones of the physical NIs (e.g., 516, 546). For example, a VNE implementing IP router functionality forwards IP packets on the basis of some of the IP header information in the IP packet; where IP header information includes source IP address, destination IP address, source port, destination port (where "source port" and

"destination port" refer herein to protocol ports, as opposed to physical ports of a ND), transport protocol (e.g., user datagram protocol (UDP), Transmission Control Protocol (TCP), and differentiated services code point (DSCP) values.

[0062] Figure 5C illustrates various exemplary ways in which VNEs may be coupled according to some embodiments of the invention. Figure 5C shows VNEs 570A.1-570A.P (and optionally VNEs 570A.Q-570A.R) implemented in ND 500A and VNE 570H.1 in ND 500H. In Figure 5C, VNEs 570A.1-P are separate from each other in the sense that they can receive packets from outside ND 500A and forward packets outside of ND 500A; VNE 570A.1 is coupled with VNE 570H.1, and thus they communicate packets between their respective NDs; VNE 570A.2-570A.3 may optionally forward packets between themselves without forwarding them outside of the ND 500A; and VNE 570A.P may optionally be the first in a chain of VNEs that includes VNE 570A.Q followed by VNE 570A.R (this is sometimes referred to as dynamic service chaining, where each of the VNEs in the series of VNEs provides a different service - e.g., one or more layer 4-7 network services). While Figure 5C illustrates various exemplary relationships between the VNEs, alternative embodiments may support other relationships (e.g., more/fewer VNEs, more/fewer dynamic service chains, multiple different dynamic service chains with some common VNEs and some different VNEs).

[0063] The NDs of Figure 5A, for example, may form part of the Internet or a private network; and other electronic devices (not shown; such as end user devices including workstations, laptops, netbooks, tablets, palm tops, mobile phones, smartphones, phablets, multimedia phones, Voice Over Internet Protocol (VOIP) phones, terminals, portable media players, GPS units, wearable devices, gaming systems, set-top boxes, Internet enabled household appliances) may be coupled to the network (directly or through other networks such as access networks) to communicate over the network (e.g., the Internet or virtual private networks (VPNs) overlaid on (e.g., tunneled through) the Internet) with each other (directly or through servers) and/or access content and/or services. Such content and/or services are typically provided by one or more servers (not shown) belonging to a service/content provider or one or more end user devices (not shown) participating in a peer-to-peer (P2P) service, and may include, for example, public webpages (e.g., free content, store fronts, search services), private webpages (e.g.,

username/password accessed webpages providing email services), and/or corporate networks over VPNs. For instance, end user devices may be coupled (e.g., through customer premise equipment coupled to an access network (wired or wirelessly)) to edge NDs, which are coupled (e.g., through one or more core NDs) to other edge NDs, which are coupled to electronic devices acting as servers. However, through compute and storage virtualization, one or more of the electronic devices operating as the NDs in Figure 5A may also host one or more such servers (e.g., in the case of the general purpose network device 504, one or more of the software instances 562A-R may operate as servers; the same would be true for the hybrid network device 506; in the case of the special-purpose network device 502, one or more such servers could also be run on a virtualization layer executed by the compute resource(s) 512); in which case the servers are said to be co-located with the VNEs of that ND. [0064] A virtual network is a logical abstraction of a physical network (such as that in Figure 5A) that provides network services (e.g., L2 and/or L3 services). A virtual network can be implemented as an overlay network (sometimes referred to as a network virtualization overlay) that provides network services (e.g., layer 2 (L2, data link layer) and/or layer 3 (L3, network layer) services) over an underlay network (e.g., an L3 network, such as an Internet Protocol (IP) network that uses tunnels (e.g., generic routing encapsulation (GRE), layer 2 tunneling protocol (L2TP), IPSec) to create the overlay network).

[0065] A network virtualization edge (NVE) sits at the edge of the underlay network and participates in implementing the network virtualization; the network-facing side of the NVE uses the underlay network to tunnel frames to and from other NVEs; the outward-facing side of the NVE sends and receives data to and from systems outside the network. A virtual network instance (VNI) is a specific instance of a virtual network on a NVE (e.g., a NE/VNE on an ND, a part of a NE/VNE on a ND where that NE/VNE is divided into multiple VNEs through emulation); one or more VNIs can be instantiated on an NVE (e.g., as different VNEs on an ND). A virtual access point (VAP) is a logical connection point on the NVE for connecting external systems to a virtual network; a VAP can be physical or virtual ports identified through logical interface identifiers (e.g., a VLAN ID).

[0066] Examples of network services include: 1) an Ethernet LAN emulation service (an Ethernet-based multipoint service similar to an Internet Engineering Task Force (IETF) Multiprotocol Label Switching (MPLS) or Ethernet VPN (EVPN) service) in which external systems are interconnected across the network by a LAN environment over the underlay network (e.g., an NVE provides separate L2 VNIs (virtual switching instances) for different such virtual networks, and L3 (e.g., IP/MPLS) tunneling encapsulation across the underlay network); and 2) a virtualized IP forwarding service (similar to IETF IP VPN (e.g., Border Gateway Protocol (BGP)/MPLS IP VPN) from a service definition perspective) in which external systems are interconnected across the network by an L3 environment over the underlay network (e.g., an NVE provides separate L3 VNIs (forwarding and routing instances) for different such virtual networks, and L3 (e.g., IP/MPLS) tunneling encapsulation across the underlay network)). Network services may also include quality of service capabilities (e.g., traffic classification marking, traffic conditioning and scheduling), security capabilities (e.g., filters to protect customer premises from network - originated attacks, to avoid malformed route announcements), and management capabilities (e.g., full detection and processing).

[0067] Fig. 5D illustrates a network with a single network element on each of the NDs of Figure 5A, and within this straight forward approach contrasts a traditional distributed approach (commonly used by traditional routers) with a centralized approach for maintaining reachability and forwarding information (also called network control), according to some embodiments of the invention. Specifically, Figure 5D illustrates network elements (NEs) 570A-H with the same connectivity as the NDs 500A-H of Figure 5A.

[0068] Figure 5D illustrates that the distributed approach 572 distributes responsibility for generating the reachability and forwarding information across the NEs 570A-H; in other words, the process of neighbor discovery and topology discovery is distributed.

[0069] For example, where the special-purpose network device 502 is used, the control communication and configuration module(s) 532A-R of the ND control plane 524 typically include a reachability and forwarding information module to implement one or more routing protocols (e.g., an exterior gateway protocol such as Border Gateway Protocol (BGP), Interior Gateway Protocol(s) (IGP) (e.g., Open Shortest Path First (OSPF), Intermediate System to Intermediate System (IS-IS), Routing Information Protocol (RIP), Label Distribution Protocol (LDP), Resource Reservation Protocol (RSVP) (including RS VP-Traffic Engineering (TE): Extensions to RSVP for LSP Tunnels and Generalized Multi-Protocol Label Switching

(GMPLS) Signaling RSVP-TE)) that communicate with other NEs to exchange routes, and then selects those routes based on one or more routing metrics. Thus, the NEs 570A-H (e.g., the compute resource(s) 512 executing the control communication and configuration

module(s) 532A-R) perform their responsibility for participating in controlling how data (e.g., packets) is to be routed (e.g., the next hop for the data and the outgoing physical NI for that data) by distributively determining the reachability within the network and calculating their respective forwarding information. Routes and adjacencies are stored in one or more routing structures (e.g., Routing Information Base (RIB), Label Information Base (LIB), one or more adjacency structures) on the ND control plane 524. The ND control plane 524 programs the ND forwarding plane 526 with information (e.g., adjacency and route information) based on the routing structure(s). For example, the ND control plane 524 programs the adjacency and route information into one or more forwarding table(s) 534A-R (e.g., Forwarding Information Base (FIB), Label Forwarding Information Base (LFIB), and one or more adjacency structures) on the ND forwarding plane 526. For layer 2 forwarding, the ND can store one or more bridging tables that are used to forward data based on the layer 2 information in that data. While the above example uses the special-purpose network device 502, the same distributed approach 572 can be implemented on the general purpose network device 504 and the hybrid network device 506.

[0070] Figure 5D illustrates that a centralized approach 574 (also known as software defined networking (SDN)) that decouples the system that makes decisions about where traffic is sent from the underlying systems that forwards traffic to the selected destination. The illustrated centralized approach 574 has the responsibility for the generation of reachability and forwarding information in a centralized control plane 576 (sometimes referred to as a SDN control module, controller, network controller, OpenFlow controller, SDN controller, control plane node, network virtualization authority, or management control entity), and thus the process of neighbor discovery and topology discovery is centralized. The centralized control plane 576 has a south bound interface 582 with a data plane 580 (sometime referred to the infrastructure layer, network forwarding plane, or forwarding plane (which should not be confused with a ND forwarding plane)) that includes the NEs 570A-H (sometimes referred to as switches, forwarding elements, data plane elements, or nodes). The centralized control plane 576 includes a network controller 578, which includes a centralized reachability and forwarding information module 579 that determines the reachability within the network and distributes the forwarding information to the NEs 570A-H of the data plane 580 over the south bound interface 582 (which may use the OpenFlow protocol). Thus, the network intelligence is centralized in the centralized control plane 576 executing on electronic devices that are typically separate from the NDs.

[0071] For example, where the special-purpose network device 502 is used in the data plane 580, each of the control communication and configuration module(s) 532A-R of the ND control plane 524 typically include a control agent that provides the VNE side of the south bound interface 582. In this case, the ND control plane 524 (the compute resource(s) 512 executing the control communication and configuration module(s) 532A-R) performs its responsibility for participating in controlling how data (e.g., packets) is to be routed (e.g., the next hop for the data and the outgoing physical NI for that data) through the control agent communicating with the centralized control plane 576 to receive the forwarding information (and in some cases, the reachability information) from the centralized reachability and forwarding information module 579 (it should be understood that in some embodiments of the invention, the control communication and configuration module(s) 532A-R, in addition to communicating with the centralized control plane 576, may also play some role in determining reachability and/or calculating forwarding information - albeit less so than in the case of a distributed approach; such embodiments are generally considered to fall under the centralized approach 574, but may also be considered a hybrid approach).

[0072] While the above example uses the special-purpose network device 502, the same centralized approach 574 can be implemented with the general purpose network device 504 (e.g., each of the VNE 560A-R performs its responsibility for controlling how data (e.g., packets) is to be routed (e.g., the next hop for the data and the outgoing physical NI for that data) by communicating with the centralized control plane 576 to receive the forwarding information (and in some cases, the reachability information) from the centralized reachability and forwarding information module 579; it should be understood that in some embodiments of the invention, the VNEs 560A-R, in addition to communicating with the centralized control plane 576, may also play some role in determining reachability and/or calculating forwarding information - albeit less so than in the case of a distributed approach) and the hybrid network device 506. In fact, the use of SDN techniques can enhance the NFV techniques typically used in the general purpose network device 504 or hybrid network device 506 implementations as NFV is able to support SDN by providing an infrastructure upon which the SDN software can be run, and NFV and SDN both aim to make use of commodity server hardware and physical switches.

[0073] Figure 5D also shows that the centralized control plane 576 has a north bound interface 584 to an application layer 586, in which resides application(s) 588. The centralized control plane 576 has the ability to form virtual networks 592 (sometimes referred to as a logical forwarding plane, network services, or overlay networks (with the NEs 570A-H of the data plane 580 being the underlay network)) for the application(s) 588. Thus, the centralized control plane 576 maintains a global view of all NDs and configured NEs/VNEs, and it maps the virtual networks to the underlying NDs efficiently (including maintaining these mappings as the physical network changes either through hardware (ND, link, or ND component) failure, addition, or removal). Applications 588 can include the buffer manager 581 that implements the functions and processes for queue selections and data packet discarding set forth herein above. In further embodiments, the buffer manager is implemented in the centralized control plane 576.

[0074] While Figure 5D shows the distributed approach 572 separate from the centralized approach 574, the effort of network control may be distributed differently or the two combined in certain embodiments of the invention. For example: 1) embodiments may generally use the centralized approach (SDN) 574, but have certain functions delegated to the NEs (e.g., the distributed approach may be used to implement one or more of fault monitoring, performance monitoring, protection switching, and primitives for neighbor and/or topology discovery); or 2) embodiments of the invention may perform neighbor discovery and topology discovery via both the centralized control plane and the distributed protocols, and the results compared to raise exceptions where they do not agree. Such embodiments are generally considered to fall under the centralized approach 574, but may also be considered a hybrid approach.

[0075] While Figure 5D illustrates the simple case where each of the NDs 500A-H implements a single NE 570A-H, it should be understood that the network control approaches described with reference to Figure 5D also work for networks where one or more of the NDs 500 A-H implement multiple VNEs (e.g., VNEs 530A-R, VNEs 560A-R, those in the hybrid network device 506). Alternatively or in addition, the network controller 578 may also emulate the implementation of multiple VNEs in a single ND. Specifically, instead of (or in addition to) implementing multiple VNEs in a single ND, the network controller 578 may present the implementation of a VNE/NE in a single ND as multiple VNEs in the virtual networks 592 (all in the same one of the virtual network(s) 592, each in different ones of the virtual

network(s) 592, or some combination). For example, the network controller 578 may cause an ND to implement a single VNE (a NE) in the underlay network, and then logically divide up the resources of that NE within the centralized control plane 576 to present different VNEs in the virtual network(s) 592 (where these different VNEs in the overlay networks are sharing the resources of the single VNE/NE implementation on the ND in the underlay network).

[0076] On the other hand, Figures 5E and 5F respectively illustrate exemplary abstractions of NEs and VNEs that the network controller 578 may present as part of different ones of the virtual networks 592. Figure 5E illustrates the simple case of where each of the NDs 500A-H implements a single NE 570A-H (see Figure 5D), but the centralized control plane 576 has abstracted multiple of the NEs in different NDs (the NEs 570A-C and G-H) into (to represent) a single NE 5701 in one of the virtual network(s) 592 of Figure 5D, according to some embodiments of the invention. Figure 5E shows that in this virtual network, the NE 5701 is coupled to NE 570D and 570F, which are both still coupled to NE 570E.

[0077] Figure 5F illustrates a case where multiple VNEs (VNE 570A.1 and VNE 570H.1) are implemented on different NDs (ND 500A and ND 500H) and are coupled to each other, and where the centralized control plane 576 has abstracted these multiple VNEs such that they appear as a single VNE 570T within one of the virtual networks 592 of Figure 5D, according to some embodiments of the invention. Thus, the abstraction of a NE or VNE can span multiple NDs.

[0078] While some embodiments of the invention implement the centralized control plane 576 as a single entity (e.g., a single instance of software running on a single electronic device), alternative embodiments may spread the functionality across multiple entities for redundancy and/or scalability purposes (e.g., multiple instances of software running on different electronic devices).

[0079] Similar to the network device implementations, the electronic device(s) running the centralized control plane 576, and thus the network controller 578 including the centralized reachability and forwarding information module 579, may be implemented a variety of ways (e.g., a special purpose device, a general-purpose (e.g., COTS) device, or hybrid device). These electronic device(s) would similarly include compute resource(s), a set or one or more physical NICs, and a non-transitory machine-readable storage medium having stored thereon the centralized control plane software. For instance, Figure 6 illustrates, a general purpose control plane device 604 including hardware 640 comprising a set of one or more processor(s) 642 (which are often COTS processors) and network interface controller(s) 644 (NICs; also known as network interface cards) (which include physical NIs 646), as well as non-transitory machine readable storage media 648 having stored therein centralized control plane (CCP) software 650.

[0080] In embodiments that use compute virtualization, the processor(s) 642 typically execute software to instantiate a virtualization layer 654 (e.g., in one embodiment the virtualization layer 654 represents the kernel of an operating system (or a shim executing on a base operating system) that allows for the creation of multiple instances 662A-R called software containers (representing separate user spaces and also called virtualization engines, virtual private servers, or jails) that may each be used to execute a set of one or more applications; in another embodiment the virtualization layer 654 represents a hypervisor (sometimes referred to as a virtual machine monitor (VMM)) or a hypervisor executing on top of a host operating system, and an application is run on top of a guest operating system within an instance 662A-R called a virtual machine (which in some cases may be considered a tightly isolated form of software container) that is run by the hypervisor ; in another embodiment, an application is implemented as a unikernel, which can be generated by compiling directly with an application only a limited set of libraries (e.g., from a library operating system (LibOS) including drivers/libraries of OS services) that provide the particular OS services needed by the application, and the unikernel can run directly on hardware 640, directly on a hypervisor represented by virtualization layer 654 (in which case the unikernel is sometimes described as running within a LibOS virtual machine), or in a software container represented by one of instances 662A-R). Again, in embodiments where compute virtualization is used, during operation an instance of the CCP software 650 (illustrated as CCP instance 676A) is executed (e.g., within the instance 662A) on the virtualization layer 654. In embodiments where compute virtualization is not used, the CCP instance 676A is executed, as a unikernel or on top of a host operating system, on the "bare metal" general purpose control plane device 604. The instantiation of the CCP instance 676A, as well as the virtualization layer 654 and instances 662A-R if implemented, are collectively referred to as software instance(s) 652.

[0081] In some embodiments, the CCP instance 676A includes a network controller instance 678. The network controller instance 678 includes a centralized reachability and forwarding information module instance 679 (which is a middleware layer providing the context of the network controller 578 to the operating system and communicating with the various NEs), and an CCP application layer 680 (sometimes referred to as an application layer) over the middleware layer (providing the intelligence required for various network operations such as protocols, network situational awareness, and user - interfaces). At a more abstract level, this CCP application layer 680 within the centralized control plane 576 works with virtual network view(s) (logical view(s) of the network) and the middleware layer provides the conversion from the virtual networks to the physical view. Application layer 680 can include the buffer manager 681 that implements the functions and processes for queue selections and data packet discarding set forth herein above. In further embodiments, the buffer manager is implemented in the centralized control plane 676.

[0082] The centralized control plane 576 transmits relevant messages to the data plane 580 based on CCP application layer 680 calculations and middleware layer mapping for each flow. A flow may be defined as a set of packets whose headers match a given pattern of bits; in this sense, traditional IP forwarding is also flow-based forwarding where the flows are defined by the destination IP address for example; however, in other implementations, the given pattern of bits used for a flow definition may include more fields (e.g., 10 or more) in the packet headers. Different NDs/NEs/VNEs of the data plane 580 may receive different messages, and thus different forwarding information. The data plane 580 processes these messages and programs the appropriate flow information and corresponding actions in the forwarding tables (sometime referred to as flow tables) of the appropriate NE/VNEs, and then the NEs/VNEs map incoming packets to flows represented in the forwarding tables and forward packets based on the matches in the forwarding tables.

[0083] Standards such as OpenFlow define the protocols used for the messages, as well as a model for processing the packets. The model for processing packets includes header parsing, packet classification, and making forwarding decisions. Header parsing describes how to interpret a packet based upon a well-known set of protocols. Some protocol fields are used to build a match structure (or key) that will be used in packet classification (e.g., a first key field could be a source media access control (MAC) address, and a second key field could be a destination MAC address).

[0084] Packet classification involves executing a lookup in memory to classify the packet by determining which entry (also referred to as a forwarding table entry or flow entry) in the forwarding tables best matches the packet based upon the match structure, or key, of the forwarding table entries. It is possible that many flows represented in the forwarding table entries can correspond/match to a packet; in this case the system is typically configured to determine one forwarding table entry from the many according to a defined scheme (e.g., selecting a first forwarding table entry that is matched). Forwarding table entries include both a specific set of match criteria (a set of values or wildcards, or an indication of what portions of a packet should be compared to a particular value/values/wildcards, as defined by the matching capabilities - for specific fields in the packet header, or for some other packet content), and a set of one or more actions for the data plane to take on receiving a matching packet. For example, an action may be to push a header onto the packet, for the packet using a particular port, flood the packet, or simply drop the packet. Thus, a forwarding table entry for IPv4/IPv6 packets with a particular transmission control protocol (TCP) destination port could contain an action specifying that these packets should be dropped.

[0085] Making forwarding decisions and performing actions occurs, based upon the forwarding table entry identified during packet classification, by executing the set of actions identified in the matched forwarding table entry on the packet.

[0086] However, when an unknown packet (for example, a "missed packet" or a "match-miss" as used in OpenFlow parlance) arrives at the data plane 580, the packet (or a subset of the packet header and content) is typically forwarded to the centralized control plane 576. The centralized control plane 576 will then program forwarding table entries into the data plane 580 to accommodate packets belonging to the flow of the unknown packet. Once a specific forwarding table entry has been programmed into the data plane 580 by the centralized control plane 576, the next packet with matching credentials will match that forwarding table entry and take the set of actions associated with that matched entry.

[0087] A network interface (NI) may be physical or virtual; and in the context of IP, an interface address is an IP address assigned to a NI, be it a physical NI or virtual NI. A virtual NI may be associated with a physical NI, with another virtual interface, or stand on its own (e.g., a loopback interface, a point-to-point protocol interface). A NI (physical or virtual) may be numbered (a NI with an IP address) or unnumbered (a NI without an IP address). A loopback interface (and its loopback address) is a specific type of virtual NI (and IP address) of a

NE/VNE (physical or virtual) often used for management purposes; where such an IP address is referred to as the nodal loopback address. The IP address(es) assigned to the NI(s) of a ND are referred to as IP addresses of that ND; at a more granular level, the IP address(es) assigned to NI(s) assigned to a NE/VNE implemented on a ND can be referred to as IP addresses of that NE/VNE.

[0088] While the invention has been described in terms of several embodiments, those skilled in the art will recognize that the invention is not limited to the embodiments described, can be practiced with modification and alteration within the spirit and scope of the appended claims. The description is thus to be regarded as illustrative instead of limiting.

Claims

CLAIMS What is claimed is:

1. A method implemented by a network device, the method for selecting a queue from

which to discard a first data packet where there are insufficient storage resources in a queue data storage, the queue data storage including a set of queues for at least one port of the network device, the method comprising:

determining (301) a guaranteed bandwidth for each queue in the set of queues for the at least one port;

determining (303) a depth for each queue of the set of queues and whether the depth is above a threshold minimum depth value;

receiving (305) at least a portion of a second data packet;

determining (307) there is insufficient space in the queue data storage to store the received portion of the second data packet;

selecting (311) a queue from the set of queues to discard the first data packet where the selected queue is a lowest priority queue that meets or if no queue exceeds the threshold minimum depth value, selecting a lowest priority queue from queues that do not exceed the threshold minimum depth value; and

discarding (315) the first data packet from the selected queue.

2. The method of claim 1, further comprising:

selecting (415) a lowest priority queue that exceeds guaranteed bandwidth where there is at least one queue in the set of queues that exceeds guaranteed bandwidth and at least one queue is over the threshold minimum depth value.

3. The method of claim 1, further comprising:

selecting (413) a lowest priority queue that does not exceed guaranteed

bandwidth where there is no queue in the set of queues that exceeds guaranteed bandwidth and at least one queue is over the threshold minimum depth value.

4. The method of claim 1, further comprising:

selecting (411) a lowest priority queue that does not exceed guaranteed bandwidth where there is no queue in the set of queues that exceeds guaranteed bandwidth and no queue is over the threshold minimum depth value.

5. The method of claim 1, further comprising:

selecting (409) a lowest priority queue that does exceed guaranteed bandwidth where there is at least one queue in the set of queues that exceeds guaranteed bandwidth and no queue is over the threshold minimum depth value.

6. A network device to execute a method for selecting a queue from which to discard a first data packet where there are insufficient storage resources in a queue data storage, the queue data storage including a set of queues for at least one port of the network device, the network device comprising:

a non-transitory computer-readable medium (518) having stored therein a buffer manager; and

a processor (512) coupled to the non-transitory computer-readable medium, the processor to execute the buffer manager, the buffer manager (564) to determine a guaranteed bandwidth for each queue in the set of queues for the at least one port, to determine a depth for each queue of the set of queues and whether the depth is above a threshold minimum depth value, to receive at least a portion of a second data packet, to determine there is insufficient space in the queue data storage to store the received portion of the second data packet, to select a queue from the set of queues to discard the first data packet where the selected queue is a lowest priority queue that meets or if no queue exceeds the threshold minimum depth value, selecting a lowest priority queue from queues that do not exceed the threshold minimum depth value, and to discard the first data packet from the selected queue.

7. The network device of claim 6, wherein the buffer manager selects a lowest priority queue that exceeds guaranteed bandwidth where there is at least one queue in the set of queues that exceeds guaranteed bandwidth and at least one queue is over the threshold minimum depth value.

8. The network device of claim 6, wherein the buffer manager selects a lowest priority queue that does not exceed guaranteed bandwidth where there is no queue in the set of queues that exceeds guaranteed bandwidth and at least one queue is over the threshold minimum depth value.

9. The network device of claim 6, wherein the buffer manager selects a lowest priority queue that does not exceed guaranteed bandwidth where there is no queue in the set of queues that exceeds guaranteed bandwidth and no queue is over the threshold minimum depth value.

10. The network device of claim 6, wherein the buffer manager selects a lowest priority queue that does exceed guaranteed bandwidth where there is at least one queue in the set of queues that exceeds guaranteed bandwidth and no queue is over the threshold minimum depth value.

11. A computing device implementing a plurality of virtual machines for implementing network function virtualization (NFV), wherein a virtual machine from the plurality of virtual machines is configured to execute a method for selecting a queue from which to discard a first data packet where there are insufficient storage resources in a queue data storage, the queue data storage including a set of queues for at least one port of the computing device, the computing device comprising:

a non-transitory computer-readable medium (548) having stored therein a buffer manager; and

a processor (542) coupled to the non-transitory computer-readable medium, the processor to execute a virtual machine from the plurality of virtual machines, the virtual machine to execute the buffer manager, the buffer manager (564) to determine a guaranteed bandwidth for each queue in the set of queues for the at least one port, to determine a depth for each queue of the set of queues and whether the depth is above a threshold minimum depth value, to receive at least a portion of a second data packet, to determine there is insufficient space in the queue data storage to store the received portion of the second data packet, to select a queue from the set of queues to discard the first data packet where the selected queue is a lowest priority queue that meets or if no queue exceeds the threshold minimum depth value, selecting a lowest priority queue from queues that do not exceed the threshold minimum depth value, and to discard the first data packet from the selected queue.

12. The computing device of claim 11, wherein the buffer manager selects a lowest priority queue that exceeds guaranteed bandwidth where there is at least one queue in the set of queues that exceeds guaranteed bandwidth and at least one queue is over the threshold minimum depth value.

13. The computing device of claim 11, wherein the buffer manager selects a lowest priority queue that does not exceed guaranteed bandwidth where there is no queue in the set of queues that exceeds guaranteed bandwidth and at least one queue is over the threshold minimum depth value.

14. The computing device of claim 11, wherein the buffer manager selects a lowest priority queue that does not exceed guaranteed bandwidth where there is no queue in the set of queues that exceeds guaranteed bandwidth and no queue is over the threshold minimum depth value.

15. The computing device of claim 11, wherein the buffer manager selects a lowest priority queue that does exceed guaranteed bandwidth where there is at least one queue in the set of queues that exceeds guaranteed bandwidth and no queue is over the threshold minimum depth value.

16. A control plane device configured to implement at least one centralized control plane for a software defined networking (SDN) network, the centralized control plane configured to execute a method for selecting a queue from which to discard a first data packet where there are insufficient storage resources in a queue data storage, the queue data storage including a set of queues for at least one port of the control plane device, the control plane device comprising:

a non-transitory computer-readable medium (648) having stored therein a buffer manager; and a processor (642) coupled to the non-transitory computer-readable medium, the processor to execute the buffer manager, the buffer manager (681) to determine a guaranteed bandwidth for each queue in the set of queues for the at least one port, to determine a depth for each queue of the set of queues and whether the depth is above a threshold minimum depth value, to receive at least a portion of a second data packet, to determine there is insufficient space in the queue data storage to store the received portion of the second data packet, to select a queue from the set of queues to discard the first data packet where the selected queue is a lowest priority queue that meets or if no queue exceeds the threshold minimum depth value, selecting a lowest priority queue from queues that do not exceed the threshold minimum depth value, and to discard the first data packet from the selected queue.

17. The control plane device of claim 16, wherein the buffer manager selects a lowest

priority queue that exceeds guaranteed bandwidth where there is at least one queue in the set of queues that exceeds guaranteed bandwidth and at least one queue is over the threshold minimum depth value.

18. The control plane device of claim 16, wherein the buffer manager selects a lowest

priority queue that does not exceed guaranteed bandwidth where there is no queue in the set of queues that exceeds guaranteed bandwidth and at least one queue is over the threshold minimum depth value.

19. The control plane device of claim 16, wherein the buffer manager selects a lowest

priority queue that does not exceed guaranteed bandwidth where there is no queue in the set of queues that exceeds guaranteed bandwidth and no queue is over the threshold minimum depth value.

20. The control plane device of claim 16, wherein the buffer manager selects a lowest

priority queue that does exceed guaranteed bandwidth where there is at least one queue in the set of queues that exceeds guaranteed bandwidth and no queue is over the threshold minimum depth value.