Abstract: A network of switches having ports coupled to other switches or end hosts may be controlled by a controller. The controller may identify whether any switch ports have failed. In response to identifying that a port has failed at a first switch, the controller may modify link aggregation group mappings of the other switches to handle failover. The controller may modify the link aggregation group mapping of each other switch to include a first mapping that includes ports coupled to the first switch and a second mapping that does not include any ports coupled to the first switch. The controller may configure forwarding tables at the switches to forward network packets using the first or second mappings based on network topology information maintained by the controller.

Abstract: A controller implemented on computing equipment may be used to control switches in a network. End hosts may be coupled to the switches. The controller may generate a virtual network topology of virtual switches, virtual routers, and virtual system routers that are distributed over underlying switches in the network. The controller may form virtual switches from respective groups of end hosts, virtual routers from groups of virtual switches that include virtual interfaces that are coupled to virtual switches, and a virtual system router from groups of virtual routers that includes virtual system router interfaces that are coupled to the virtual routers. The controller may control the virtual network topology by generating respective flow table entries based on identified network policies for each of the virtual routers, virtual system routers, and virtual switches. The controller may control the virtual system routers to route packets between the virtual routers.

Abstract: A controller may fulfill hardware address requests that are sent by source end hosts in a network to discover hardware addresses of destination end hosts. The controller may use network topology information to determine how to process the hardware address requests. The controller may retrieve a requested hardware address from a database of end hosts. If the controller is able to retrieve the hardware address of a destination end host from the database of end hosts, the controller may provide the source end host with a reply packet that contains the requested hardware address. If the controller is unable to retrieve the requested hardware address, the controller may form request packets to discover the address of the second end host and/or to discover a packet forwarding path between the source end host and the destination end host.

Abstract: A controller may control client switches in a network including client and non-client switches. The controller may maintain a link discovery table including entries that identify links between client switches. The controller may classify the links as direct or broadcast links. To classify links of the link discovery cable, the controller may direct client switches to send broadcast and directed discovery packets from switch ports. Client switches that receive the discovery packets from other client switches may forward the discovery packets to the controller. The controller may use the discovery packets to classify the links of the link discovery table. The controller may classify ports as broadcast or regular ports based on the classified links. Non-client broadcast domains of the network topology may be identified from the broadcast ports using the broadcast and direct links of the link discovery table.

Abstract: A controller implemented on computing equipment may be used to control switches in a network. End hosts and service devices may be coupled to the switches in the network. The controller may generate a virtual network topology of virtual switches and virtual routers. The controller may control the virtual routers and/or virtual switches to perform service insertion. The controller may perform service insertion by controlling the virtual routers and/or virtual switches to redirect network traffic through one or more selected service devices. The controller may determine which network traffic is to be redirected to which service devices based on a service insertion policy that identifies network traffic and services to be performed on the network traffic.

Abstract: A controller may control client switches in a network including client and non-client switches. The controller may maintain a link discovery table including entries that identify links between client switches. The controller may classify the links as direct or broadcast links. To classify links of the link discovery table, the controller may direct client switches to send broadcast and directed discovery packets from switch ports. Client switches that receive the discovery packets from other client switches may forward the discovery packets to the controller. The controller may use the discovery packets to classify the links of the link discovery table. The controller may classify ports as broadcast or regular ports based on the classified links. Non-client broadcast domains of the network topology may be identified from the broadcast ports using the broadcast and direct links of the link discovery table.

Abstract: A controller may control client switches in a network including client and non-client switches. The controller may maintain a link discovery table including entries that identify links between client switches. The controller may classify the links as direct or broadcast links. To classify links of the link discovery table, the controller may direct client switches to send broadcast and directed discovery packets from switch ports. Client switches that receive the discovery packets from other client switches may forward the discovery packets to the controller. The controller may use the discovery packets to classify the links of the link discovery table. The controller may classify ports as broadcast or regular ports based on the classified links. Non-client broadcast domains of the network topology may be identified from the broadcast ports using the broadcast and direct links of the link discovery table.

Abstract: A controller implemented on computing equipment may be used to control switches in a network. End hosts may be coupled to the switches. The controller may generate a virtual network topology of virtual switches, virtual routers, and virtual system routers that are distributed over underlying switches in the network. The controller may form virtual switches from respective groups of end hosts, virtual routers from groups of virtual switches that include virtual interfaces that are coupled to virtual switches, and a virtual system router from groups of virtual routers that includes virtual system router interfaces that are coupled to the virtual routers. The controller may control the virtual network topology by generating respective flow table entries based on identified network policies for each of the virtual routers, virtual system routers, and virtual switches. The controller may control the virtual system routers to route packets between the virtual routers.

Abstract: A network of switches having ports coupled to other switches or end hosts may be controlled by a controller. The controller may identify whether any switch ports have failed. In response to identifying that a port has failed at a first switch, the controller may modify link aggregation group mappings of the other switches to handle failover. The controller may modify the link aggregation group mapping of each other switch to include a first mapping that includes ports coupled to the first switch and a second mapping that does not include any ports coupled to the first switch. The controller may configure forwarding tables at the switches to forward network packets using the first or second mappings based on network topology information maintained by the controller.

Abstract: A network may include network switches with network switch ports that may be coupled to end hosts. The network switches may be controlled by a controller such as a controller server. Virtual switches may be formed using the controller from groups of the network switch ports and the end hosts. Each virtual switch may include virtual interfaces associated with end hosts or network switches. Virtual links may be formed that define network connections between the virtual interfaces and end hosts or between two virtual interfaces. Virtual network policies such as selective packet forwarding, packet dropping, packet redirection, packet modification, or packet logging may be implemented at selected virtual interfaces to control traffic through the communications network. The controller may translate the virtual network policies into network switch forwarding paths that satisfy the virtual network policies.

Abstract: A controller implemented on computing equipment may be used to control switches in a network. End hosts and service devices may be coupled to the switches in the network. The controller may generate a virtual network topology of virtual switches and virtual routers. The controller may control the virtual routers and/or virtual switches to perform service insertion. The controller may perform service insertion by controlling the virtual routers and/or virtual switches to redirect network traffic through one or more selected service devices. The controller may determine which network traffic is to be redirected to which service devices based on a service insertion policy that identifies network traffic and services to be performed on the network traffic.

Abstract: A controller may help reduce network traffic that is associated with broadcasting of Dynamic Host Configuration Protocol (DHCP) packets by converting broadcast DHCP packets into unicast DHCP packets and forwarding the unicast DHCP packets to appropriate DHCP servers. The servers may be identified from a database of servers that is updated with DHCP server address information based on DHCP reply packets that are received by the controller from servers in the network. To convert DHCP request packets into unicast packets, the controller may modify address header fields of the packets such as Ethernet addresses and Internet Protocol (IP) addresses. The controller may forward the modified DHCP request packets to the server by providing packet forwarding rules such as flow table entries to the switches or by forwarding the modified DHCP request packets through the controller.

Abstract: Network packets may be transmitted from packet sources to packet destinations through a network of switches. The switches may have corresponding flow tables that control how the packets are forwarded through the switches. A controller server may generate network switch forwarding paths for the network packets by modifying the flow tables with entries based on attributes of the network packets and network topology information. The controller server may forward selected packets directly to packet destinations instead of generating the network switch forwarding paths. To determine which packets to directly forward, the controller server may calculate cost metrics associated with the network switch forwarding paths and associated with forwarding network packets directly to packet destinations.

Abstract: Network policies that control the flow of traffic through a network may be implemented using a controller server that controls a network of switches. Based on network packet attributes, the controller server may identify network policies that are associated with the network traffic. The controller server may identify dependencies between the network policies based on priorities that are associated with the network policies and overlap between the network policies. The controller server may provide the switches with packet forwarding rules based on the identified dependencies between the network policies, network switch attributes, and network switch capabilities. The packet forwarding rules may implement network policies for current network traffic and future network traffic.

Abstract: A controller may help reduce network traffic that is associated with broadcasting of Dynamic Host Configuration Protocol (DHCP) packets by converting broadcast DHCP packets into unicast DHCP packets and forwarding the unicast DHCP packets to appropriate DHCP servers. The servers may be identified from a database of servers that is updated with DHCP server address information based on DHCP reply packets that are received by the controller from servers in the network. To convert DHCP request packets into unicast packets, the controller may modify address header fields of the packets such as Ethernet addresses and Internet Protocol (IP) addresses. The controller may forward the modified DHCP request packets to the server by providing packet forwarding rules such as flow table entries to the switches or by forwarding the modified DHCP request packets through the controller.

Abstract: A network may include network switches with network switch ports that may be coupled to end hosts. The network switches may be controlled by a controller such as a controller server. Virtual switches may be formed using the controller from groups of the network switch ports and the end hosts. Each virtual switch may include virtual interfaces associated with end hosts or network switches. Virtual links may be formed that define network connections between the virtual interfaces and end hosts or between two virtual interfaces. Virtual network policies such as selective packet forwarding, packet dropping, packet redirection, packet modification, or packet logging may be implemented at selected virtual interfaces to control traffic through the communications network. The controller may translate the virtual network policies into network switch forwarding paths that satisfy the virtual network policies.