WO2020212998A1

WO2020212998A1 - Network address allocation in a virtual layer 2 domain spanning across multiple container clusters

Info

Publication number: WO2020212998A1
Application number: PCT/IN2019/050312
Authority: WO
Inventors: Vyshakh Krishnan C H; Faseela K
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2019-04-17
Filing date: 2019-04-17
Publication date: 2020-10-22

Abstract

A method by an address allocator in a first cluster of a container orchestration system for allocating network addresses to containers in the first cluster. The method includes determining that a first network address has been allocated by a remote address allocator in a second cluster of the container orchestration system to a first remote container in the second cluster, removing the first network address from a set of network addresses available for allocation to local containers in the first cluster, and responsive to receiving a request to allocate a network address to a first local container in the first cluster and after removing the first network address from the set of network addresses, allocating to the first local container a second network address from the set of network addresses available for allocation to local containers in the first cluster.

Description

NETWORK ADDRESS ALLOCATION IN A VIRTUAL LAYER 2 DOMAIN SPANNING ACROSS MULTIPLE CONTAINER CLUSTERS

TECHNICAL LIELD

[0001] Embodiments of the invention relate to the field of computer networks, and more specifically to allocating network addresses in a virtual Layer 2 (L2) domain spanning across multiple container clusters.

BACKGROUND ART

[0002] Containers provide a standard way to package an application’s code, configurations, and dependencies into a single object. Containers are isolated from each other and from the host on which they run. Containers typically have their own filesystems, cannot see the processes of other containers, and their computational resource usage can be bounded. Containers are easier to build than virtual machines (VMs) and since they are decoupled from the underlying infrastructure and from the host filesystem, they are portable across clouds and operating system (OS) distributions. Also, containers have the benefit of being small and fast.

[0003] A container cluster is a dynamic system that includes a collection of nodes on which containers can be deployed. Each node in the cluster can be a virtual machine or a physical machine. A container orchestrator may deploy containers, grouped together in pods, on the nodes in the cluster, and manage the interconnections and communication channels between pods. The use of containers is becoming popular in industry due to the many benefits they provide.

[0004] Network addresses such as Layer 2 (L2) addresses (e.g., Media Access Control (MAC) addresses) and Layer 3 addresses (e.g., Internet Protocol (IP) addresses) are typically allocated to containers in a cluster using either a centralized address allocation mode or a distributed address allocation mode. In the centralized address allocation mode, a centralized address allocator allocates network addresses to all of the containers in the cluster. The centralized address allocator is typically implemented by the master node of the cluster. When a new container is deployed in the cluster, a request is sent to the centralized address allocator to allocate a network address to the newly deployed container. In response, the centralized address allocator allocates an available network address to the container. [0005] A MAC address is a 48-bit value that typically includes 3 bytes of an organizationally unique identifier (OUI) and 3 bytes of random bits. The OUI uniquely identifies a vendor, manufacturer, or other organization. OUI is centrally registered and can be bought from the Institute of Electrical and Electronics Engineers (IEEE). In the centralized address allocation mode, since the centralized address allocator allocates MAC addresses to all of the containers in the cluster, even if the random bits end up being the same as the random bits of an already allocated MAC address, the centralized address allocator can recognize this and allocate a new/different MAC address.

[0006] The centralized address allocator may allocate IP addresses to containers in a cluster based on the subnet configured for the cluster. When the centralized address allocator receives a request to allocate an IP address to a container in a cluster, the centralized address allocator may choose an unallocated IP address from the subnet pool and allocate that IP address to the container. For example, if the subnet is 10.1.1.0/24, then the centralized address allocator may allocate IP addresses 10.1.1.1, 10.1.1.2, 10.1.1.3, 10.1.1.4, and so on to the containers in the cluster.

[0007] In the distributed address allocation mode, each node in the cluster is allocated a fixed set of network addresses and the address allocator of each respective node may only allocate the network addresses allocated to that node. Since the distributed address allocation mode has a static allocation scheme, most container orchestrators prefer to use the centralized address allocation mode.

[0008] In a multi-cluster environment, clusters may communicate with each other using a routing and reachability protocol such as Border Gateway Protocol (BGP). Each cluster may include a BGP speaker to facilitate communications with other clusters and external networks. The BGP speaker of a cluster may announce a container’s network address to other clusters and to external networks and learn external routes from other BGP speakers to enable cluster-to-cluster and cluster-to-external communications.

[0009] Extending Layer 2 (L2) domains across multiple networks has become a very common feature in cloud networking solutions. Border Gateway Protocol Ethernet Virtual Private Network (BGP EVPN) is commonly used to provide an L2 Ethernet interconnect between multiple sites/clusters. For example, a BGP speaker in a cluster may establish a Multiprotocol BGP (MP-BGP) session with a BGP speaker in another cluster and exchange Ethernet Virtual Private Network (EVPN) routes with that BGP speaker to extend the Local Area Network (LAN) across multiple sites/clusters. [0010] In the case of an L2 domain that spans across multiple clusters (forming a virtual L2 domain), the address allocators in the different clusters typically use the same OUI when generating MAC addresses. As such, there is a possibility that address allocators in different clusters will allocate the same MAC address to different containers (e.g., if they happen to choose the same random bits). Similarly, since the address allocators in different clusters typically allocate IP addresses to containers from the same subnet, there is a possibility that address allocators in different clusters will allocate the same IP address to different containers. In a single cluster environment, it is easy for the centralized address allocator to detect duplicate network address allocations and resolve duplicates. However, in a multi-cluster environment, it is difficult to detect and resolve such overlap.

[0011] Allocating the same network address (e.g., MAC address or IP address) to different containers may cause various problems in the network such as constant MAC address moves which may result in locking of MAC addresses (resulting in container unreachability), constant IP address moves resulting in locking of IP addresses (also resulting in container unreachability), packet loops, and unstable routing/switching information in the network.

[0012] One existing solution for avoiding such duplicate network address allocation in different clusters is to statically assign a pool of network addresses that can be allocated in each cluster. However, such static network address allocation scheme may under-allocate network addresses to a cluster that needs a large amount of network addresses and over allocate network addresses to a cluster that does not need a large amount of network addresses.

[0013] Another existing solution for avoiding duplicate network address allocation in different clusters is to have a centralized address allocator for all of the clusters. However, such centralized network address allocation scheme is typically slow as all of the address allocation requests from all of the clusters must be sent to the centralized address allocator and the responses sent back to the respective clusters. Also, such centralized network address allocation scheme has a single point of failure. If the centralized address allocator fails, then the clusters will starve for network addresses.

SUMMARY

[0014] A method is implemented by one or more network devices implementing an address allocator in a first cluster of a container orchestration system for allocating network addresses to containers in the first cluster. The method includes determining that a first network address has been allocated by a remote address allocator in a second cluster of the container orchestration system to a first remote container in the second cluster, removing the first network address from a set of network addresses available for allocation to local containers in the first cluster that are part of the same virtual Layer 2 (L2) domain as the first remote container in the second cluster, receiving a request to allocate a network address to a first local container in the first cluster, and in response to receiving the request and after removing the first network address from the set of network addresses, allocating to the first local container in the first cluster a second network address from the set of network addresses available for allocation to local containers in the first cluster.

[0015] A network device to implement an address allocator in a first cluster of a container orchestration system that is configured to allocate network addresses to containers in the first cluster. The network device includes a set of one or more processors and a non- transitory computer-readable storage medium to store instructions, which when executed by the set of one or more processors, causes the network device to determine that a first network address has been allocated by a remote address allocator in a second cluster of the container orchestration system to a first remote container in the second cluster, remove the first network address from a set of network addresses available for allocation to local containers in the first cluster that are part of the same virtual Layer 2 (L2) domain as the first remote container in the second cluster, receive a request to allocate a network address to a first local container in the first cluster, and in response to receiving the request and after removing the first network address from the set of network addresses, allocate to the first local container in the first cluster a second network address from the set of network addresses available for allocation to local containers in the first cluster.

[0016] A non-transitory computer-readable storage medium storing instructions (e.g., computer code), which when executed by one or more processors of a network device implementing an address allocator in a first cluster of a container orchestration system, causes the network device to perform operations for allocating network addresses to containers in the first cluster. The operations include determining that a first network address has been allocated by a remote address allocator in a second cluster of the container orchestration system to a first remote container in the second cluster, removing the first network address from a set of network addresses available for allocation to local containers in the first cluster that are part of the same virtual Layer 2 (L2) domain as the first remote container in the second cluster, receiving a request to allocate a network address to a first local container in the first cluster, and in response to receiving the request and after removing the first network address from the set of network addresses, allocating to the first local container in the first cluster a second network address from the set of network addresses available for allocation to local containers in the first cluster.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] 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:

[0018] Figure 1A is a block diagram of a container orchestration system in which network addresses can be allocated in a virtual L2 domain spanning across multiple clusters while avoiding duplicate network address allocation, according to some embodiments.

[0019] Figure IB is a block diagram of a cluster in which network addresses can be allocated, according to some embodiments.

[0020] Figure 2 is a flow diagram of a process for allocating network addresses in a virtual F2 domain that spans across multiple clusters while avoiding duplicate network address allocation, according to some embodiments.

[0021] Figure 3 is a flow diagram of a process for supporting address allocation in a virtual F2 domain that spans across multiple clusters while avoiding duplicate network address allocation, according to some embodiments.

[0022] Figure 4A illustrates connectivity between network devices (NDs) within an exemplary network, as well as three exemplary implementations of the NDs, according to some embodiments.

[0023] Figure 4B illustrates an exemplary way to implement a special-purpose network device according to some embodiments.

[0024] Figure 4C illustrates various exemplary ways in which virtual network elements (VNEs) may be coupled according to some embodiments.

[0025] Figure 4D 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.

[0026] Figure 4E 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. [0027] Figure 4F 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.

[0028] Figure 5 illustrates a general purpose control plane device with centralized control plane (CCP) software, according to some embodiments.

DETAILED DESCRIPTION

[0029] The following description describes methods and apparatus for allocating network addresses to containers in a virtual Layer 2 (L2) domain spanning across multiple container clusters. 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.

[0030] 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.

[0031] 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. [0032] 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.

[0033] 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, solid state drives, 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 (e.g., wherein a processor is a microprocessor, controller, microcontroller, central processing unit, digital signal processor, application specific integrated circuit, field programmable gate array, other electronic circuitry, a combination of one or more of the preceding) 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 non-volatile 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) (NI(s)) to establish network connections (to transmit and/or receive code and/or data using propagating signals) with other electronic devices. For example, the set of physical NIs (or the set of physical NI(s) in combination with the set of processors executing code) may perform any formatting, coding, or translating to allow the electronic device to send and receive data whether over a wired and/or a wireless connection. In some embodiments, a physical NI may comprise radio circuitry capable of receiving data from other electronic devices over a wireless connection and/or sending data out to other devices via a wireless connection. This radio circuitry may include transmitter(s), receiver(s), and/or transceiver(s) suitable for radiofrequency communication. The radio circuitry may convert digital data into a radio signal having the appropriate parameters (e.g., frequency, timing, channel, bandwidth, etc.). The radio signal may then be transmitted via antennas to the appropriate recipient(s). In some embodiments, the set of physical NI(s) may comprise network interface controller(s) (NICs), also known as a network interface card, network adapter, or local area network (LAN) adapter. The NIC(s) may facilitate in connecting the electronic device to other electronic devices allowing them to communicate via wire through plugging in a cable to a physical port connected to a NIC. One or more parts of an embodiment of the invention may be implemented using different combinations of software, firmware, and/or hardware.

[0034] 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).

[0035] As mentioned above, in the case of a Layer 2 (L2) domain that spans across multiple container clusters, address allocators in different clusters may end up allocating the same network address (e.g., Media Access Control (MAC) address and/or Internet Protocol (IP) address) to containers in different clusters, which may cause various problems in the network. A static network address allocation scheme may avoid duplicate network address allocation but this scheme typically over-allocates or under-allocates network addresses to clusters. A centralized address allocation scheme may also avoid duplicate network address allocation but this scheme is typically slow and has a single point of failure.

[0036] Embodiments described herein provide a network address allocation scheme that is able to avoid duplicate network address allocation in a virtual L2 domain that spans across multiple container clusters without the drawbacks of the existing solutions. According to some embodiments, an address allocator in a first cluster of a container orchestration system determines that a first network address has been allocated by a remote address allocator in a second cluster of the container orchestration system to a first remote container in the second cluster. The address allocator may determine that the first network address has been allocated based on receiving an indication from a local routing and reachability protocol speaker (e.g., a Border Gateway Protocol (BGP) speaker) in the first cluster that the first network address has been allocated. The local routing and reachability protocol speaker may have determined that the first network address was allocated based on receiving an advertisement message originated by a remote routing and reachability protocol speaker in the second cluster. In response to determining that the first network address has been allocated, the address allocator may remove the first network address from a set of network addresses available for allocation to local containers in the first cluster that are part of the same virtual Layer 2 (L2) domain as the first remote container in the second cluster. If the address allocator subsequently receives a request to allocate a network address to a first local container in the first cluster, the address allocator allocates to the first local container in the first cluster a second network address from the set of network addresses available for allocation to local containers in the first cluster. This set of network addresses does not include the first network address because the first network address was removed from the set. Various embodiments are further described herein below.

[0037] Figure 1A is a block diagram of a container orchestration system in which network addresses can be allocated in a virtual L2 domain spanning across multiple container clusters while avoiding duplicate network address allocation, according to some embodiments. As shown in the diagram, the container orchestration system (sometimes simply referred to herein as“system”) includes container cluster 108 communicatively coupled to container cluster 109 through network 107. The system provides an environment in which containerized applications can be automatically deployed, scaled, and managed. A container cluster (sometimes simply referred to herein as“cluster”), as used herein, is a collection of one or more nodes (e.g., which may be virtual machines and/or physical machines) managed by an entity on which containers can be deployed and run. Network 107 may be any suitable network that is able to provide connectivity between clusters 108 and 109. In one embodiment, network 107 is a Multiprotocol Label Switching (MPLS) network over which Border Gateway Protocol Ethernet Virtual Private Network (BGP EVPN) can be run.

[0038] As shown in the diagram, cluster 108 includes address allocator 121, routing and reachability protocol (RARP) speaker 131, node 103, router 111, and containers 101A-N. Address allocator 121 is communicatively coupled to node 103 and RARP speaker 131. Address allocator 121 may allocate network addresses (e.g., MAC addresses and/or IP addresses) to containers 101 in cluster 108. In one embodiment, address allocator 121 is a component of a container orchestrator (e.g., Kubernetes®). RARP speaker 131 may run a routing and reachability protocol to exchange routing and reachability information with other RARP speakers. In one embodiment, RARP speaker 131 is a BGP speaker that runs BGP EVPN and exchanges advertisement messages (e.g., BGP EVPN messages) with other BGP speakers to advertise routes in cluster 108 and to learn routes in other clusters. Node 103 is a worker machine that can run one or more containers. Node 103 can be a virtual machine or a physical machine. As shown in the diagram, node 103 runs container 101A. Each of the other containers 101B-N in cluster 108 may also run on a node in cluster 108 (e.g., on node 103 or another node in cluster 108 as determined by a container orchestrator). In one embodiment, one or more of the containers 101A-N are Docker® containers.

[0039] In a symmetrical manner, as shown in the diagram, cluster 109 includes address allocator 122, RARP speaker 132, node 104, router 112, and containers 102A-M. Address allocator 122 is communicatively coupled to node 104 and RARP speaker 132. Address allocator 122 may allocate network addresses to containers 102 in cluster 109. In one embodiment, address allocator 122 is a component of a container orchestrator (e.g., Kubernetes®). RARP speaker 132 may run a routing and reachability protocol to exchange routing and reachability information with other RARP speakers. In one embodiment, RARP speaker 132 is a BGP speaker that runs BGP EVPN and exchanges advertisement messages (e.g., BGP EVPN messages) with other BGP speakers to advertise routes in cluster 109 and to learn routes in other clusters. Node 104 is a worker machine that can run one or more containers. Node 104 can be a virtual machine or a physical machine. As shown in the diagram, node 104 runs container 102A. Each of the other containers 102B-N in cluster 109 may also run on a node in cluster 109 (e.g., on node 104 or another node in cluster 109 as determined by a container orchestrator). In one embodiment, one or more of the containers 102A-M are Docker® containers.

[0040] Cluster 108 and cluster 109 may be communicatively coupled through network 107 via router 111 and router 112. Router 111 and router 112 may communicate with each other using a routing and reachability protocol to exchange routing and reachability information. Thus, router 111 may transmit advertisement messages (e.g., BGP EVPN messages) to router 112 to advertise routes in cluster 108. Likewise, router 112 may transmit advertisement messages to router 111 to advertise routes in cluster 109. In one embodiment, router 111 and router 112 are BGP speakers running BGP EVPN that exchange BGP EVPN messages with each other over network 107. In such an embodiment as mentioned above, network 107 may be an MPLS network or other suitable underlay network over which BGP EVPN can be run.

[0041] Node 103 is communicatively coupled to router 111 via a virtual L2 tunnel (e.g., Virtual Extensible Local Area Network (VXLAN) tunnel) implemented over an underlay network. The underlay network can be implemented using any suitable Layer 3 (L3) protocol. Similarly, Node 104 is communicatively coupled to router 112 via a virtual L2 tunnel (e.g., which may also be a VXLAN tunnel) implemented over an underlay network. Again, the underlay network can be implemented using any suitable Layer 3 protocol. The virtual L2 tunnels and the interconnect between the clusters (e.g., established over network 107 using BGP EVPN) can be used to extend an L2 domain across clusters 108 and 109, thereby creating a virtual L2 domain 114. As shown in the diagram, in an exemplary scenario, container 101A in cluster 108 and container 102A in cluster 109 are within the same virtual L2 domain 114 (but are located in different clusters). Operations for allocating network addresses in a virtual L2 domain 114 spanning across multiple clusters while avoiding duplicate network address allocation will now be described with reference to Figs. 1A and IB.

[0042] At operation 1, address allocator 121 receives a request to allocate a MAC address and an IP address to container 101A. In response, at operation 2, address allocator 121 allocates an available MAC address and an available IP address to container 101A. Address allocator 121 may generate the MAC address to be allocated based on a combination of an OUI and random bits. Address allocator 121 may have selected the IP address to be allocated by selecting the next available IP address in the subnet.

[0043] RARP speaker 131 is aware of the network addresses allocated to the different containers 101 in cluster 108 (e.g., RARP speaker 131 may receive this information from address allocator 121). In one embodiment, at operation 3, RARP speaker 131 transmits an advertisement message to router 111 advertising the MAC address and the IP address allocated to container 101A. In some embodiments, RARP speaker 131 may transmit an advertisement directly to RARP speaker 132 (in cluster 109) without going through router 111. In this case, operations 4 and 5 may be skipped. In one embodiment, RARP speaker 131 is a BGP speaker and the advertisement message is a Border Gateway Protocol Ethernet Virtual Private Network Route Type 2 (BGP EVPN RT2) message. BGP EVPN RT2 messages can be used for advertising the MAC address and IP address of containers 101. In one embodiment, a BGP EVPN RT2 message may include the following fields: 1) Route distinguisher (8 octets); 2) Ethernet segment identifier (10 octets); 3) Ethernet tag identifier (ID) (4 octets); 4) MAC address length (1 octet); 5) MAC address (6 octets); 6) IP address length (1 octet); 7) IP address (0, 4, or 16 octets); 8) MPLS label- 1 (3 octets); and 9) MPLS label-2 (0 or 3 octets). RARP speaker 131 may advertise the MAC address and IP address allocated to container 101A by transmitting a BGP EVPN RT2 message that specifies the MAC address and the IP address allocated to container 101A in the MAC address field and IP address field of the BGP EVPN RT2 message, respectively.

[0044] At operation 4, responsive to receiving the advertisement message from RARP speaker 131, router 111 in turn transmits an advertisement message to router 112 (over network 107) advertising the MAC address and the IP address allocated to container 101A. This advertisement message may have similar format and content as the advertisement message transmitted in operation 3 (e.g., in an embodiment where router 111 is a BGP speaker this may be a BGP EVPN RT2 message).

[0045] At operation 5, responsive to receiving the advertisement message from router 111, router 112 in turn transmits an advertisement message to RARP speaker 132 advertising the MAC address and the IP address allocated to container 101A. This advertisement message may have similar format and content as the advertisement message transmitted in operations 3 and 4 (e.g., in an embodiment where router 112 is a BGP speaker this may be a BGP EVPN RT2 message). RARP speaker 132 is able to determine the MAC address and the IP address allocated to container 101A based on receiving the advertisement message.

[0046] At operation 6, responsive to determining the MAC address and the IP address allocated to container 101A, RARP speaker 132 informs address allocator 122 that the MAC address and the IP address allocated to container 101A are being used. In response, at operation 7, address allocator 122 marks the MAC address and the IP address allocated to container 101A as being used. For example, address allocator 122 may mark the MAC address and the IP address allocated to container 101A as being used by adding the MAC address and the IP address to a list of used/unavailable MAC addresses and a list of used/unavailable IP addresses, respectively, that are maintained by address allocator 122. In another example, address allocator 122 may mark the MAC address and the IP address allocated to container 101A as being used by removing the MAC address and the IP address from a list of unused/available MAC addresses and a list of unused/available IP addresses, respectively, that are maintained by address allocator 122. As will be further described with reference to Figure IB, this allows address allocator 122 to avoid allocating the MAC address and/or the IP address allocated to container 101A to containers 102 in cluster 109.

[0047] Now referring to Figure IB, at operation 8, address allocator 122 receives a request to allocate a MAC address and an IP address to container 102A. In response, address allocator 122 allocates an available MAC address and an available IP address to container 102A. It should be noted that the MAC address and the IP address allocated to container 101A (in cluster 108) are not available for allocation since they have been marked as being used/unavailable (e.g., at operation 7). Thus, address allocator 122 does not allocate the MAC address or the same IP address allocated to the container 101A in cluster 108, thereby avoiding duplicate network address allocation.

[0048] Even with the solution described above there can be a scenario where containers in different clusters are allocated the same network address because the address allocators in the respective clusters (e.g., address allocators 121 and 122) allocate the same network address to containers in their respective clusters at around the same time and before the address allocators are informed about that network address being allocated in a different cluster. As will be described in additional detail below, embodiments may provide a tie breaking mechanism to handle such scenarios.

[0049] If an address allocator in a different cluster (a remote cluster) allocated the same MAC address and/or the same IP address allocated to container 102A to a container around the same time that address allocator 122 allocated the MAC address and the IP address to container 102A, then at operation 10, router 112 may receive an advertisement message from a remote RARP speaker (e.g., router 111) advertising the same MAC address and/or the same IP address allocated to container 102A. In response, at operation 11, router 112 transmits an advertisement message to RARP speaker 132 advertising the same MAC address and/or the same IP address allocated to container 102A. In response, at operation 12, RARP speaker 132 informs address allocator 122 that the same MAC address and/or the same IP address allocated to container 102A is being used.

[0050] At operation 13, address allocator 122 checks whether the remote cluster that advertised the MAC address and/or the IP address allocated to container 102A has priority over cluster 109 (the local cluster) for purposes of network address allocation. At operation 14, if the remote cluster has priority over the local cluster 109, then address allocator 122 allocates a new MAC address and/or new IP address (depending on which of these overlaps with the remote cluster) to container 102A to avoid overlap. In one embodiment, address allocator 122 allocates a new MAC address to container 102A by restarting container 102A or otherwise restarting the network stack of container 102A. In one embodiment, address allocator 122 allocates a new IP address to container 102A using a Dynamic Host Control Protocol (DHCP) renewal mechanism. In an embodiment where the advertisement messages are BGP EVPN RT2 messages, the determination of which cluster has priority (at least for network address allocation purposes) is based on a comparison of BGP router identifiers of BGP speakers (e.g., which may be included in BGP OPEN messages and/or BGP UPDATE messages) in the clusters or other attribute/value that is unique across clusters. For example, a higher BGP router identifier may have priority over a lower BGP router identifier or vice versa. In another embodiment, the determination of which cluster has priority is based on a comparison of the Ethernet Segment Identifier included in BGP EVPN RT2 messages. Returning to operation 14, if the remote cluster does not have priority over the local cluster 109, then address allocator 122 keeps the MAC address and/or IP address allocated to container 102A (and the address allocator in the remote cluster would allocate a new MAC address and/or IP address since it will determine that it does not have priority).

[0051] For purposes of illustration only, the example shown in Figures 1A and IB and described above is a network address allocation scenario involving two different clusters over which a virtual L2 domain is extended. It should be understood that the network address allocation mechanism described herein can be similarly extended to scenarios involving more than two clusters.

[0052] The network address allocation mechanism described herein provides several advantages over existing network address allocation mechanisms. For example, one advantage is that it avoids duplicate network address allocation across clusters in a virtual L2 domain that spans across multiple clusters without statically allocating pools of network addresses to clusters (as done with a static network address allocation scheme which typically over-allocates or under-allocates network addresses to clusters) and without requiring a centralized address allocator (as done with a centralized network address allocation scheme, which is typically slow and has a single point of failure). Another advantage of the network address allocation mechanism described herein is that it makes use of existing advertisement messages (e.g., BGP EVPN RT2 messages) without introducing additional proprietary protocols or messages, which simplifies implementation and minimizes/reduces overhead. Many cluster deployments already use advertisement messages to advertise routing and reachability information (but do not use this information for network address allocation purposes). In these cases, the network address allocation mechanism described herein can be implemented without introducing any additional messages.

[0053] Figure 2 is a flow diagram of a process for allocating network addresses in a virtual L2 domain that spans across multiple clusters while avoiding duplicate network address allocation, according to some embodiments. In one embodiment, the process is implemented by an address allocator in a first cluster (which may be referred to as the local cluster) of a container orchestration system. The container orchestration system may include one or more other clusters including a second cluster (which may be referred to as remote clusters). 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 other than those discussed with reference to the other figures, and the embodiments discussed with reference to these other figures can perform operations different than those discussed with reference to the flow diagrams.

[0054] At block 210, the address allocator determines that a first network address has been allocated by a remote address allocator in a second cluster of the container orchestration system to a first remote container in the second cluster. The address allocator may have determined this based on receiving an indication from a local RARP speaker (e.g., BGP speaker) in the first cluster that the first network address has been allocated. The local RARP speaker in the first cluster may have in turn determined that the first network address has been allocated based on receiving an advertisement message (e.g., BGP EVPN RT2 message) originated by a remote RARP speaker in the second cluster. In one embodiment, the network address is a MAC address or an IP address.

[0055] In response, at block 220, the address allocator removes the first network address from a set of network addresses available for allocation to local containers in the first cluster that are part of the same virtual Layer 2 (L2) domain as the first remote container in the second cluster.

[0056] At block 230, the address allocator subsequently receives a request to allocate a network address to a first local container in the first cluster. In response to receiving the request at block 230 and after removing the first network address from the set of network addresses at block 220, at block 240, the address allocator allocates to the first local container in the first cluster a second network address from the set of network addresses available for allocation to local containers in the first cluster. The set of network addresses available for allocation to local containers in the first cluster does not include the first network address because the first network address was removed from the set of network addresses available for allocation to local containers in the first cluster (i.e., at block 220). In one embodiment, the allocation of the second network address to the first local container in the first cluster causes a local RARP speaker in the first cluster to transmit an advertisement message to a remote RARP speaker in the second cluster advertising the second network address. [0057] In one embodiment, at block 250, the address allocator may determine that a third network address has been allocated by the remote address allocator in the second cluster to a second remote container in the second cluster. In response, at decision block 260, the address allocator may determine whether the third network address is allocated to a local container in the first cluster. If not (i.e., there is no duplicate network address allocation), the process ends. However, if the address allocator determines that the third network address is allocated to a local container in the first cluster (i.e., there is duplicate network address allocation), then at decision block 270, the address allocator may determine whether the second cluster has priority over the first cluster for purposes of network address allocation (based on a tie-breaking mechanism). If not, the address allocator keeps the third network address allocated to that particular local container and the process ends. However, if the address allocator determines that the second cluster has priority over the first cluster for purposes of address allocation, then at block 280, the address allocator may allocate a new network address to that particular local container (i.e., the local container to which the third network address was previously allocated) in the first cluster. In one embodiment, the tie-breaking mechanism is based on a comparison of BGP router identifiers of BGP speakers in the first cluster and the second cluster (e.g., higher BGP router identifier has priority or vice versa). In another embodiment, the tie-breaking mechanism is based on a comparison of Ethernet Segment Identifiers included in the BGP EVPN RT2 messages (e.g., higher Ethernet Segment Identifier has priority or vice versa). In an embodiment where the network address is a MAC address, the address allocator may allocate a new network address to the particular local container in the first cluster by restarting the particular local container in the first cluster or otherwise restarting a network stack of the particular local container in the first cluster. In an embodiment where the network address is an IP address, the address allocator may allocate a new network address to the particular local container in the first cluster using a DHCP renewal mechanism.

[0058] Figure 3 is a flow diagram of a process for supporting network address allocation in a virtual L2 domain that spans across multiple clusters while avoiding duplicate network address allocation, according to some embodiments. In one embodiment, the process is implemented by a RARP speaker (e.g., BGP speaker) in a first cluster (which may be referred to as the local cluster) of a container orchestration system. The container orchestration system may include one or more other clusters including a second cluster (which may be referred to as remote clusters). [0059] At block 310, the BGP speaker receives, from a remote RARP speaker (e.g., a remote BGP speaker) in a second cluster of the container orchestration system, an advertisement message (e.g., BGP EVPN RT2 message) advertising a network address allocated to a remote container in the second cluster. In response, at block 320, the RARP speaker transmits an indication to an address allocator in the first cluster that the network address has been allocated to cause the address allocator to remove the network address from a set of network addresses available for allocation to local containers in the first cluster that are part of the same virtual Layer 2 (L2) domain as the remote container in the second cluster.

[0060] Figure 4A illustrates connectivity between network devices (NDs) within an exemplary network, as well as three exemplary implementations of the NDs, according to some embodiments. Figure 4A shows NDs 400A-H, and their connectivity by way of lines between 400A-400B, 400B-400C, 400C-400D, 400D-400E, 400E-400F, 400F-400G, and 400A-400G, as well as between 400H and each of 400A, 400C, 400D, and 400G. 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 400A, 400E, and 400F 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).

[0061] Two of the exemplary ND implementations in Figure 4A are: 1) a special-purpose network device 402 that uses custom application-specific integrated-circuits (ASICs) and a special-purpose operating system (OS); and 2) a general purpose network device 404 that uses common off-the-shelf (COTS) processors and a standard OS.

[0062] The special-purpose network device 402 includes networking hardware 410 comprising a set of one or more processor(s) 412, forwarding resource(s) 414 (which typically include one or more ASICs and/or network processors), and physical network interfaces (NIs) 416 (through which network connections are made, such as those shown by the connectivity between NDs 400A-H), as well as non-transitory machine readable storage media 418 having stored therein networking software 420. During operation, the networking software 420 may be executed by the networking hardware 410 to instantiate a set of one or more networking software instance(s) 422. Each of the networking software instance(s) 422, and that part of the networking hardware 410 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) 422), form a separate virtual network element 430A-R. Each of the virtual network element(s) (VNEs) 430A-R includes a control communication and configuration module 432A-R (sometimes referred to as a local control module or control communication module) and forwarding table(s) 434A-R, such that a given virtual network element (e.g., 430A) includes the control communication and configuration module (e.g., 432A), a set of one or more forwarding table(s) (e.g., 434A), and that portion of the networking hardware 410 that executes the virtual network element (e.g., 430A).

[0063] Software 420 can include code such as multi-cluster address allocation component 425, which when executed by networking hardware 410, causes the special-purpose network device 402 to perform operations of one or more embodiments described herein above as part networking software instances 422 (e.g., to perform the operations of a RARP speaker as described herein).

[0064] The special-purpose network device 402 is often physically and/or logically considered to include: 1) a ND control plane 424 (sometimes referred to as a control plane) comprising the processor(s) 412 that execute the control communication and configuration module(s) 432A-R; and 2) a ND forwarding plane 426 (sometimes referred to as a forwarding plane, a data plane, or a media plane) comprising the forwarding resource(s) 414 that utilize the forwarding table(s) 434A-R and the physical NIs 416. By way of example, where the ND is a router (or is implementing routing functionality), the ND control plane 424 (the processor(s) 412 executing the control communication and configuration module(s) 432A-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) 434A-R, and the ND forwarding plane 426 is responsible for receiving that data on the physical NIs 416 and forwarding that data out the appropriate ones of the physical NIs 416 based on the forwarding table(s) 434A- R.

[0065] Figure 4B illustrates an exemplary way to implement the special-purpose network device 402 according to some embodiments. Figure 4B shows a special-purpose network device including cards 438 (typically hot pluggable). While in some embodiments the cards 438 are of two types (one or more that operate as the ND forwarding plane 426 (sometimes called line cards), and one or more that operate to implement the ND control plane 424 (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 436 (e.g., a first full mesh coupling the line cards and a second full mesh coupling all of the cards).

[0066] Returning to Figure 4A, the general purpose network device 404 includes hardware 440 comprising a set of one or more processor(s) 442 (which are often COTS processors) and physical NIs 446, as well as non-transitory machine readable storage media 448 having stored therein software 450. During operation, the processor(s) 442 execute the software 450 to instantiate one or more sets of one or more applications 464A-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 454 represents the kernel of an operating system (or a shim executing on a base operating system) that allows for the creation of multiple instances 462A-R called software containers that may each be used to execute one (or more) of the sets of applications 464A-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 454 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 464A-R is run on top of a guest operating system within an instance 462A-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 sendees needed by the application. As a unikernel can be implemented to run directly on hardware 440, directly on a hypervisor (in which case the unikemel 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 454, unikernels running within software containers represented by instances 462A-R, or as a combination of unikemels and the above-described techniques (e.g., unikemels and virtual machines both run directly on a hypervisor, unikemels and sets of applications that are run in different software containers).

[0067] The instantiation of the one or more sets of one or more applications 464A-R, as well as virtualization if implemented, are collectively referred to as software instance(s) 452. Each set of applications 464A-R, corresponding virtualization construct (e.g., instance 462A-R) if implemented, and that part of the hardware 440 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) 460A-R.

[0068] The virtual network element(s) 460A-R perform similar functionality to the virtual network element(s) 430A-R - e.g., similar to the control communication and configuration module(s) 432A and forwarding table(s) 434A (this virtualization of the hardware 440 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 are illustrated with each instance 462A-R corresponding to one VNE 460A-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 462A-R to VNEs also apply to embodiments where such a finer level of granularity and/or unikemels are used.

[0069] In certain embodiments, the virtualization layer 454 includes a virtual switch that provides similar forwarding services as a physical Ethernet switch. Specifically, this virtual switch forwards traffic between instances 462A-R and the physical NI(s) 446, as well as optionally between the instances 462A-R; in addition, this virtual switch may enforce network isolation between the VNEs 460A-R that by policy are not permitted to communicate with each other (e.g., by honoring virtual local area networks (VLANs)). [0070] Software 450 can include code such as multi-cluster address allocation component 463, which when executed by processor(s) 442, cause the general purpose network device 404 to perform operations of one or more embodiments described herein above as part software instances 462A-R (e.g., to perform the operations of a RARP speaker as described herein).

[0071] The third exemplary ND implementation in Figure 4A is a hybrid network device 406, 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 402) could provide for para- virtualization to the networking hardware present in the hybrid network device 406.

[0072] 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) 430A- R, VNEs 460A-R, and those in the hybrid network device 406) receives data on the physical NIs (e.g., 416, 446) and forwards that data out the appropriate ones of the physical NIs (e.g., 416, 446). 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.

[0073] Figure 4C illustrates various exemplary ways in which VNEs may be coupled according to some embodiments. Figure 4C shows VNEs 470A.1-470A.P (and optionally VNEs 470A.Q-470A.R) implemented in ND 400A and VNE 470H.1 in ND 400H. In Figure 4C, VNEs 470A.1-P are separate from each other in the sense that they can receive packets from outside ND 400A and forward packets outside of ND 400A; VNE 470A.1 is coupled with VNE 470H.1, and thus they communicate packets between their respective NDs; VNE 470A.2-470A.3 may optionally forward packets between themselves without forwarding them outside of the ND 400A; and VNE 470A.P may optionally be the first in a chain of VNEs that includes VNE 470A.Q followed by VNE 470A.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 4C 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).

[0074] The NDs of Figure 4A, 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 4A may also host one or more such servers (e.g., in the case of the general purpose network device 404, one or more of the software instances 462A-R may operate as servers; the same would be true for the hybrid network device 406; in the case of the special-purpose network device 402, one or more such servers could also be run on a virtualization layer executed by the processor(s) 412); in which case the servers are said to be co-located with the VNEs of that ND.

[0075] A virtual network is a logical abstraction of a physical network (such as that in Figure 4A) 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).

[0076] 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).

[0077] 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).

[0078] Fig. 4D illustrates a network with a single network element on each of the NDs of Figure 4A, 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. Specifically, Figure 4D illustrates network elements (NEs) 470A-H with the same connectivity as the NDs 400A-H of Figure 4A. [0079] Figure 4D illustrates that the distributed approach 472 distributes responsibility for generating the reachability and forwarding information across the NEs 470A-H; in other words, the process of neighbor discovery and topology discovery is distributed.

[0080] For example, where the special-purpose network device 402 is used, the control communication and configuration module(s) 432A-R of the ND control plane 424 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 RSVP- 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 470A-H (e.g., the processor(s) 412 executing the control communication and configuration module(s) 432A-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 424. The ND control plane 424 programs the ND forwarding plane 426 with information (e.g., adjacency and route information) based on the routing structure(s). For example, the ND control plane 424 programs the adjacency and route information into one or more forwarding table(s) 434A-R (e.g., Forwarding Information Base (FIB), Label Forwarding Information Base (LFIB), and one or more adjacency structures) on the ND forwarding plane 426. 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 402, the same distributed approach 472 can be implemented on the general purpose network device 404 and the hybrid network device 406.

[0081] Figure 4D illustrates that a centralized approach 474 (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 474 has the responsibility for the generation of reachability and forwarding information in a centralized control plane 476 (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 476 has a south bound interface 482 with a data plane 480 (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 470A-H (sometimes referred to as switches, forwarding elements, data plane elements, or nodes). The centralized control plane 476 includes a network controller 478, which includes a centralized reachability and forwarding information module 479 that determines the reachability within the network and distributes the forwarding information to the NEs 470A- H of the data plane 480 over the south bound interface 482 (which may use the OpenFlow protocol). Thus, the network intelligence is centralized in the centralized control plane 476 executing on electronic devices that are typically separate from the NDs. In one embodiment, the network controller 478 may include a multi-cluster address allocation component 481 that when executed by the network controller 478, causes the network controller 478 to perform operations of one or more embodiments described herein above (e.g., to perform the operations of an address allocator as described herein)

[0082] For example, where the special-purpose network device 402 is used in the data plane 480, each of the control communication and configuration module(s) 432A-R of the ND control plane 424 typically include a control agent that provides the VNE side of the south bound interface 482. In this case, the ND control plane 424 (the processor(s) 412 executing the control communication and configuration module(s) 432A-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 476 to receive the forwarding information (and in some cases, the reachability information) from the centralized reachability and forwarding information module 479 (it should be understood that in some embodiments, the control communication and configuration module(s) 432A-R, in addition to communicating with the centralized control plane 476, 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 474, but may also be considered a hybrid approach).

[0083] While the above example uses the special-purpose network device 402, the same centralized approach 474 can be implemented with the general purpose network device 404 (e.g., each of the VNE 460A-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 476 to receive the forwarding information (and in some cases, the reachability information) from the centralized reachability and forwarding information module 479; it should be understood that in some embodiments, the VNEs 460A-R, in addition to communicating with the centralized control plane 476, 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 406. In fact, the use of SDN techniques can enhance the NFV techniques typically used in the general purpose network device 404 or hybrid network device 406 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.

[0084] Figure 4D also shows that the centralized control plane 476 has a north bound interface 484 to an application layer 486, in which resides application(s) 488. The centralized control plane 476 has the ability to form virtual networks 492 (sometimes referred to as a logical forwarding plane, network services, or overlay networks (with the NEs 470A-H of the data plane 480 being the underlay network)) for the application(s) 488. Thus, the centralized control plane 476 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).

[0085] While Figure 4D shows the distributed approach 472 separate from the centralized approach 474, the effort of network control may be distributed differently or the two combined in certain embodiments. For example: 1) embodiments may generally use the centralized approach (SDN) 474, 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 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 474, but may also be considered a hybrid approach.

[0086] While Figure 4D illustrates the simple case where each of the NDs 400A-H implements a single NE 470A-H, it should be understood that the network control approaches described with reference to Figure 4D also work for networks where one or more of the NDs 400A-H implement multiple VNEs (e.g., VNEs 430A-R, VNEs 460A-R, those in the hybrid network device 406). Alternatively or in addition, the network controller 478 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 478 may present the implementation of a VNE/NE in a single ND as multiple VNEs in the virtual networks 492 (all in the same one of the virtual network(s) 492, each in different ones of the virtual network(s) 492, or some combination). For example, the network controller 478 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 476 to present different VNEs in the virtual network(s) 492 (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).

[0087] On the other hand, Figures 4E and 4F respectively illustrate exemplary abstractions of NEs and VNEs that the network controller 478 may present as part of different ones of the virtual networks 492. Figure 4E illustrates the simple case of where each of the NDs 400A-H implements a single NE 470A-H (see Figure 4D), but the centralized control plane 476 has abstracted multiple of the NEs in different NDs (the NEs 470A-C and G-H) into (to represent) a single NE 4701 in one of the virtual network(s) 492 of Figure 4D, according to some embodiments. Figure 4E shows that in this virtual network, the NE 4701 is coupled to NE 470D and 470F, which are both still coupled to NE 470E.

[0088] Figure 4F illustrates a case where multiple VNEs (VNE 470A.1 and VNE 470H.1) are implemented on different NDs (ND 400A and ND 400H) and are coupled to each other, and where the centralized control plane 476 has abstracted these multiple VNEs such that they appear as a single VNE 470T within one of the virtual networks 492 of Figure 4D, according to some embodiments. Thus, the abstraction of a NE or VNE can span multiple NDs.

[0089] While some embodiments implement the centralized control plane 476 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).

[0090] Similar to the network device implementations, the electronic device(s) running the centralized control plane 476, and thus the network controller 478 including the centralized reachability and forwarding information module 479, 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 processor(s), a set or one or more physical NIs, and a non-transitory machine -readable storage medium having stored thereon the centralized control plane software. For instance, Figure 5 illustrates, a general purpose control plane device 504 including hardware 540 comprising a set of one or more processor(s) 542 (which are often COTS processors) and physical NIs 546, as well as non- transitory machine readable storage media 548 having stored therein centralized control plane (CCP) software 550 and a multi-cluster address allocation component 551.

[0091] In embodiments that use compute virtualization, the processor(s) 542 typically execute software to instantiate a virtualization layer 554 (e.g., in one 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 (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 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 an application is run on top of a guest operating system within an instance 562A-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 unikemel, 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 unikemel can run directly on hardware 540, directly on a hypervisor represented by virtualization layer 554 (in which case the unikemel is sometimes described as running within a LibOS virtual machine), or in a software container represented by one of instances 562A-R). Again, in embodiments where compute virtualization is used, during operation an instance of the CCP software 550 (illustrated as CCP instance 576A) is executed (e.g., within the instance 562A) on the virtualization layer 554. In embodiments where compute virtualization is not used, the CCP instance 576A is executed, as a unikemel or on top of a host operating system, on the“bare metal” general purpose control plane device 504. The instantiation of the CCP instance 576A, as well as the virtualization layer 554 and instances 562A-R if implemented, are collectively referred to as software instance(s) 552. [0092] In some embodiments, the CCP instance 576A includes a network controller instance 578. The network controller instance 578 includes a centralized reachability and forwarding information module instance 579 (which is a middleware layer providing the context of the network controller 478 to the operating system and communicating with the various NEs), and an CCP application layer 580 (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 580 within the centralized control plane 476 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.

[0093] The multi-cluster address allocation component 551 can be executed by hardware 540 to perform operations of one or more embodiments described herein above as part of software instances 1052 (e.g., to perform the operations of an address allocator as described herein).

[0094] The centralized control plane 476 transmits relevant messages to the data plane 480 based on CCP application layer 580 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 480 may receive different messages, and thus different forwarding information. The data plane 480 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.

[0095] 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). [0096] 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.

[0097] 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.

[0098] However, when an unknown packet (for example, a“missed packet” or a“match- miss” as used in OpenFlow parlance) arrives at the data plane 480, the packet (or a subset of the packet header and content) is typically forwarded to the centralized control plane 476. The centralized control plane 476 will then program forwarding table entries into the data plane 480 to accommodate packets belonging to the flow of the unknown packet. Once a specific forwarding table entry has been programmed into the data plane 480 by the centralized control plane 476, the next packet with matching credentials will match that forwarding table entry and take the set of actions associated with that matched entry.

[0099] 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.

[00100] Some portions of the preceding detailed descriptions have been presented in terms of algorithms and symbolic representations of transactions on data bits within a computer memory. These algorithmic descriptions and representations are the ways used by those skilled in the data processing arts to most effectively convey the substance of their work to others skilled in the art. An algorithm is here, and generally, conceived to be a self- consistent sequence of transactions leading to a desired result. The transactions are those requiring physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, or the like.

[00101] It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise as apparent from the above discussion, it is appreciated that throughout the description, discussions utilizing terms such as "processing" or "computing" or "calculating" or "determining" or "displaying" or the like, refer to the action and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical (electronic) quantities within the computer system's registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission or display devices.

[00102] The algorithms and displays presented herein are not inherently related to any particular computer or other apparatus. Various general-purpose systems may be used with programs in accordance with the teachings herein, or it may prove convenient to construct more specialized apparatus to perform the required method transactions. The required structure for a variety of these systems will appear from the description above. In addition, embodiments of the present invention are not described with reference to any particular programming language. It will be appreciated that a variety of programming languages may be used to implement the teachings of embodiments as described herein. [00103] An embodiment may be an article of manufacture in which a non-transitory machine-readable medium (such as microelectronic memory) has stored thereon instructions (e.g., computer code) which program one or more data processing components (generically referred to here as a“processor”) to perform the operations described above. In other embodiments, some of these operations might be performed by specific hardware components that contain hardwired logic (e.g., dedicated digital filter blocks and state machines). Those operations might alternatively be performed by any combination of programmed data processing components and fixed hardwired circuit components.

[00104] Throughout the description, embodiments of the present invention have been presented through flow diagrams. It will be appreciated that the order of transactions and transactions described in these flow diagrams are only intended for illustrative purposes and not intended as a limitation of the present invention. One having ordinary skill in the art would recognize that variations can be made to the flow diagrams without departing from the broader spirit and scope of the invention as set forth in the following claims.

[00105] In the foregoing specification, embodiments have been described with reference to specific exemplary embodiments thereof. It will be evident that various modifications may be made thereto without departing from the broader spirit and scope of the invention as set forth in the following claims. The specification and drawings are, accordingly, to be regarded in an illustrative sense rather than a restrictive sense.

Claims

CLAIMS:

1. A method implemented by one or more network devices implementing an address allocator in a first cluster of a container orchestration system for allocating network addresses to containers in the first cluster, the method comprising:

determining (210) that a first network address has been allocated by a remote address allocator in a second cluster of the container orchestration system to a first remote container in the second cluster;

removing (220) the first network address from a set of network addresses available for allocation to local containers in the first cluster that are part of the same virtual Layer 2 (L2) domain as the first remote container in the second cluster;

receiving (230) a request to allocate a network address to a first local container in the first cluster; and

in response to receiving the request and after removing the first network address from the set of network addresses, allocating (240) to the first local container in the first cluster a second network address from the set of network addresses available for allocation to local containers in the first cluster.

2. The method of claim 1, wherein the determining that the first network address has been allocated by the remote address allocator in the second cluster to the first remote container in the second cluster is based on receiving an indication from a local routing and reachability protocol (RARP) speaker in the first cluster that the first network address has been allocated, wherein the local RARP speaker in the first cluster determined that the first network address has been allocated based on receiving an advertisement message originated by a remote RARP speaker in the second cluster.

3. The method of claim 2, wherein the local RARP speaker in the first cluster is a Border Gateway Protocol (BGP) speaker, and wherein the advertisement message is a BGP Ethernet Virtual Private Network Route Type 2 (BGP EVPN RT2) message.

4. The method of claim 1, further comprising: determining (250) that a third network address has been allocated by the remote address allocator in the second cluster to a second remote container in the second cluster;

determining (270) whether the second cluster has priority over the first cluster for purposes of network address allocation based on performing a tie-breaking mechanism in response to a determination that the third network address is also allocated to a local container in the first cluster; and

allocating (280) a new network address to the local container in the first cluster to which the third network address was previously allocated, in response to a determination that the second cluster has priority over the first cluster for purposes of network address allocation.

5. The method of claim 4, wherein the tie -breaking mechanism is based on a comparison of Border Gateway Protocol (BGP) router identifiers of BGP speakers in the first cluster and the second cluster.

6. The method of claim 4, wherein the network address is a Media Access Control (MAC) address.

7. The method of claim 6, wherein the new network address is allocated to the local container in the first cluster to which the third network address was previously allocated by restarting the local container in the first cluster or restarting a network stack of the local container in the first cluster.

8. The method of claim 4, wherein the network address is an Internet Protocol (IP) address.

9. The method of claim 8, wherein the new network address is allocated to the local container in the first cluster to which the third network address was previously allocated using a Dynamic Host Control Protocol (DHCP) renewal mechanism.

10. The method of claim 4, further comprising: keeping the third network address allocated to the local container in the first cluster in response to a determination that the second cluster does not have priority over the first cluster for purposes of network address allocation.

11. The method of claim 1, wherein allocation of the second network address to the first local container in the first cluster causes a local routing and reachability protocol (RARP) speaker in the first cluster to transmit an advertisement message to a remote RARP speaker in the second cluster advertising the second network address.

12. A network device (504) to implement an address allocator in a first cluster of a container orchestration system that is configured to allocate network addresses to containers in the first cluster, the network device comprising:

a set of one or more processors (542); and

a non-transitory computer-readable storage medium (548) to store instructions (551), which when executed by the set of one or more processors, causes the network device to:

determine that a first network address has been allocated by a remote address allocator in a second cluster of the container orchestration system to a first remote container in the second cluster,

remove the first network address from a set of network addresses available for allocation to local containers in the first cluster that are part of the same virtual Layer 2 (L2) domain as the first remote container in the second cluster,

receive a request to allocate a network address to a first local container in the first cluster, and

in response to receiving the request and after removing the first network address from the set of network addresses, allocate to the first local container in the first cluster a second network address from the set of network addresses available for allocation to local containers in the first cluster.

13. The network device of claim 12, wherein determining that the first network address has been allocated by the remote address allocator in the second cluster to the first remote container in the second cluster is based on receiving an indication from a local routing and reachability protocol (RARP) speaker in the first cluster that the first network address has been allocated, wherein the local RARP speaker in the first cluster determined that the first network address has been allocated based on receiving an advertisement message originated by a remote RARP speaker in the second cluster.

14. The network device of claim 13, wherein the local RARP speaker in the first cluster is a Border Gateway Protocol (BGP) speaker, and wherein the advertisement message is a BGP Ethernet Virtual Private Network Route Type 2 (BGP EVPN RT2) message.

15. The network device of claim 12, wherein the instructions, when executed by the set of one or more processors, further causes the network device to:

determine that a third network address has been allocated by the remote address allocator in the second cluster to a second remote container in the second cluster,

determine whether the second cluster has priority over the first cluster for purposes of network address allocation based on performing a tie-breaking mechanism in response to a determination that the third network address is also allocated to a local container in the first cluster, and

allocate a new network address to the local container in the first cluster to which the third network address was previously allocated, in response to a determination that the second cluster has priority over the first cluster for purposes of network address allocation.

16. The network device of claim 15, wherein the tie-breaking mechanism is based on a comparison of Border Gateway Protocol (BGP) router identifiers of BGP speakers in the first cluster and the second cluster.

17. The network device of claim 15, wherein the instructions, when executed by the set of one or more processors, further causes the network device to:

keep the third network address allocated to the local container in the first cluster in response to a determination that the second cluster does not have priority over the first cluster for purposes of network address allocation.

18. A non-transitory computer-readable storage medium storing instructions, which when executed by one or more processors of a network device implementing an address allocator in a first cluster of a container orchestration system, causes the network device to perform operations for allocating network addresses to containers in the first cluster, the operations comprising:

19. The non-transitory computer-readable storage medium of claim 18, wherein the determining that the first network address has been allocated by the remote address allocator in the second cluster to the first remote container in the second cluster is based on receiving an indication from a local routing and reachability protocol (RARP) speaker in the first cluster that the first network address has been allocated, wherein the local RARP speaker in the first cluster determined that the first network address has been allocated based on receiving an advertisement message originated by a remote BGP speaker in the second cluster, wherein the local RARP speaker in the first cluster is a Border Gateway Protocol (BGP) speaker, and wherein the advertisement message is a BGP Ethernet Virtual Private Network Route Type 2 (BGP EVPN RT2) message.

20. The non-transitory computer-readable storage medium of claim 18, wherein the operations further comprise: determining (250) that a third network address has been allocated by the remote address allocator in the second cluster to a second remote container in the second cluster;