Patent Description:
IETF rfc5880, authored by Katz, D. and dates June <NUM> describes Bidirectional Forwarding Detection (BFD). This document describes a protocol intended to detect faults in the bidirectional path between two forwarding engines, including interfaces, data link(s), and to the extent possible the forwarding engines themselves, with potentially very low latency. It operates independently of media, data protocols, and routing protocols. However this document does not teach an approach in which use of a BFD control packet includes a diagnostic code to cause a recipient network device to cause forwarding plane traffic to be diverted away from the network device which sent the BFD control packet.

Particular aspects of the invention are set out in the appended independent claims. Various optional embodiments of the invention are set out in the dependent claims.

According to some implementations, a method according to claim <NUM> is included.

According to some implementations, a first network device may include one or more memories and one or more processors to receive, from a second network device, a BFD control packet that includes an indication that the second network device is in a maintenance mode; process the BFD control packet to determine the indication that the second network device is in the maintenance mode; and perform, based on the indication that the second network device is in the maintenance mode, one or more actions associated with a link between the first network device and the second network device.

According to some implementations, a computer-readable medium may store one or more instructions. The one or more instructions, when executed by one or more processors of a first network device may cause the one or more processors to determine to transition to a maintenance mode; and transmit, to a second network device, a BFD control packet that includes an indication that the first network device is in the maintenance mode.

A network deployment may include a plurality of network devices that are communicatively connected via one or more links. The network devices may implement one or more networking and/or routing protocols over the links, such as border gate protocol (BGP), open shortest path first (OSPF), intermediate system to intermediate system (IS-IS) protocol, and/or the like.

In some cases, a network device may enter a maintenance mode so that maintenance (e.g., software and/or firmware updates, bug fixes, configuration updates, and/or the like) may be performed on the network device. However, some networking protocols, such as BGP and/or other exterior gateway protocols, may not provide a mechanism to divert forwarding plane traffic away from the network device while the network device is in the maintenance mode. As a result, these networking protocols may need to be deactivated and/or the links associated with the network device may need to be brought down in order to divert forwarding plane traffic away from the network device while the network device is in the maintenance mode. This may result in frequent routing table updates, forwarding information base updates, and/or other updates in the network deployment to remove the links while the network device is in the maintenance mode and to add the links back after the network device is transitioned back into an active mode. This may cause increased consumption of processing, memory, and/or network resources, may cause delays in forwarding plane traffic forwarding, may cause forwarding plane traffic to be dropped, and/or the like.

According to some implementations described herein, a network device may use a bidirectional forwarding detection (BFD) control packet to indicate to other network devices that the network device is in a maintenance mode. As claimed, the network device transmits a BFD control packet to another network device. The BFD control packet includes a diagnostic code field, which may be used to indicate a change in session diagnostic parameter of a BFD session of the network device. The network device configures the diagnostic code field to include a particular value such that the diagnostic code field indicates that the network device is in the maintenance mode.

The other network device may identify the particular value in the diagnostic code field and performs one or more actions associated with a link between the network device and the other network device to divert forwarding plane traffic away from the network device while the network device is in the maintenance mode, such as increasing an OSPF link cost of the link, increasing a route cost of one or more routes that includes the link, decreasing a BGP local preference of one or more routes that includes the link, and/or the like.

In this way, the network device uses the diagnostic code field in the BFD control packet to divert traffic away from the network device while the network device is in the maintenance mode and without deactivating other network protocols or bringing down the links associated with the network device. This decreases consumption of processing, memory, and/or network resources, decreases delays in forwarding plane traffic forwarding, decreases the likelihood of forwarding plane traffic being dropped, and/or the like as a result of the network device being in the maintenance mode.

<FIG> and <FIG> are diagrams of one or more example implementations <NUM> described herein. As shown in <FIG> and <FIG>, example implementation(s) <NUM> may include communication between a plurality of network devices, such as network device <NUM> and network device <NUM>. In some implementations, network device <NUM> and network device <NUM> may be included in a network deployment and may be communicatively connected by one or more links. In some implementations, example implementation(s) <NUM> may include a greater quantity of network devices.

As shown in <FIG>, and by reference number <NUM>, network device <NUM> may determine to transition to a maintenance mode. In some implementations, the maintenance mode may include an operational mode in which network device <NUM> does not forward forwarding plane traffic in the network deployment. The maintenance mode may further include an operational mode in which software and/or firmware updates may be performed on network device <NUM>, debugging and/or troubleshooting may be performed on network device <NUM>, control plane and/or forwarding plane configuration updates may be performed on network device <NUM>, and/or the like.

In some implementations, network device <NUM> may determine to transition to the maintenance mode based on receiving an instruction to transition to the maintenance mode. For example, the instruction may be provided as input to network device <NUM> by a user, may be provided via a link from another network device (e.g., network device <NUM> and/or another network device), and/or the like. In some implementations, network device <NUM> may determine to transition to the maintenance mode based on detecting an event, such as a fault associated with network device <NUM> (e.g., a control plane or forwarding plane fault, a processing system fault, and/or the like), a fault associated with a link associated with network device <NUM>, and/or the like.

As further shown in <FIG>, and by reference number <NUM>, network device <NUM> may generate and transmit a BFD control packet that indicates that network device <NUM> is in the maintenance mode. In some implementations, network device <NUM> may generate and transmit the BFD control packet based on determining to transition to the maintenance mode. In some implementations, network device <NUM> may transmit the BFD control packet to network device <NUM> and/or other network devices in the network deployment to which network device <NUM> is communicatively connected via a link.

In some implementations, the BFD control packet may be transmitted as part of a BFD session associated with network device <NUM> and network device <NUM>. In this case, network device <NUM> may transmit the BFD control packet based on a time interval for transmitting BFD control packets in the BFD session. Moreover, network device <NUM> may continue to transmit BFD control packets that indicate that network device <NUM> is in the maintenance mode while network device <NUM> continues to operate in the maintenance mode.

In some implementations, network device <NUM> may configure a diagnostic code field, included in the BFD control packet, to indicate that network device <NUM> is in the maintenance mode. For example, network device <NUM> may configure the diagnostic code field to include a particular value that indicates that network device <NUM> is in the maintenance mode. The particular value may function as an overload indicator (e.g., may indicate that overload is enabled on network device <NUM>). The overload indicator may be an indication that network device <NUM> cannot process additional forwarding plane traffic and that forwarding plane traffic should be redirected away from network device <NUM>. In some implementations, network device <NUM> may use a diagnostic code field reserved value for the particular value, in which case the particular value may be represented by one or more bits associated with the reserved value.

Network device <NUM> may receive the BFD control packet and may process the BFD control packet to identify the diagnostic code field in the BFD control packet, and to identify the particular value included in the diagnostic control field. Network device <NUM> may be configured to determine that the particular value is an indicator that network device <NUM> is in the maintenance mode.

As further shown in <FIG>, and by reference number <NUM>, network device <NUM> performs one or more actions based on the BFD control packet. In particular, network device <NUM> performs one or more actions to divert forwarding plane traffic away from the link between network device <NUM> and network device <NUM> based on determining that the BFD control packet indicates that network device <NUM> is in the maintenance mode.

In some implementations, the one or more actions may include setting an overload detected parameter, associated with the BFD session of the network device <NUM>, to a particular value. In this case, other networking protocols operating on network device <NUM> that are clients of the BFD session (e.g., IS-IS protocol, OSPF protocol, BGP, and/or the like) may identify the particular value and perform one or more actions.

For example, the OSPF protocol operating on network device <NUM> may increase an OSPF link cost of the link between network device <NUM> and network device <NUM> such that the increased OSPF link cost causes network device <NUM> to generate routes that do not include the link. In this case, network device <NUM> may transmit an indication of the increased OSPF link cost to other network devices in the network deployment such that the other network devices may generate routes that do not include the link.

As another example, network device <NUM> may increase a route cost of one or more routes that include the link between network device <NUM> and network device <NUM>, such that the increased route cost causes network device <NUM> to avoid routing forwarding plane traffic using the one or more routes (e.g., to route the forwarding plane traffic via alternate routes that do not include the one or more routes). In this case, network device <NUM> may transmit an indication of the increased route cost of the one or more routes to other network devices in the network deployment such that the other network devices route forwarding plane traffic via alternate routes.

As another example, a routing protocol operating on network device <NUM> may decrease a BGP local preference of one or more routes that include the link between network device <NUM> and network device <NUM> such that the decreased BGP local preference causes network device <NUM> to avoid routing forwarding plane traffic using the one or more routes (e.g., to route the forwarding plane traffic via alternate routes that do not include the one or more routes). In this case, network device <NUM> may transmit an indication of the decreased BGP local preference of the one or more routes to other network devices in the network deployment such that the other network devices route forwarding plane traffic via alternate routes.

In some implementations, network device <NUM> may subsequently transition out of the maintenance mode and into an active mode (e.g., a mode in which network device <NUM> forwards forwarding plane traffic in the network deployment). In this case, network device <NUM> may generate and transmit another BFD control packet to network device <NUM> and/or other network devices, where the other BFD control packet indicates that network device <NUM> is no longer in the maintenance mode. For example, network device <NUM> may generate the other BFD control packet such that a diagnostic code field, included in the BFD control packet, includes a particular value that indicates that network device <NUM> is no longer in the maintenance mode. In this case, the particular value may include a <NUM> value associated with a No Diagnostic indicator or another value that may indicate that network device <NUM> is no longer in the maintenance mode.

Network device <NUM> may receive the other BFD control packet, may identify the particular value in the diagnostic control field, and may determine that the particular value indicates that network device <NUM> is no longer in the maintenance mode. In this case, network device <NUM> may perform one or more actions to cause forwarding plane traffic to be routed via the link between network device <NUM> and network device <NUM>. For example, network device <NUM> may set the overload detected parameter, associated with the BFD session of the network device <NUM>, to a particular value that indicates that an overload associated with network device <NUM> is not detected. As another example, network device <NUM> may decrease the OSPF link cost of the link between network device <NUM> and network device <NUM>. As another example, network device <NUM> may decrease a route cost of the one or more routes that include the link between network device <NUM> and network device <NUM>. As another example, network device <NUM> may increase the BGP route preference of the one or more routes that include the link between network device <NUM> and network device <NUM>.

<FIG> illustrates an example BFD control packet format. The version field (Vers) may identify a version number of BFD associated with the BFD session of network device <NUM> and network device <NUM>. The diagnostic code field (Diag) may identify a reason for a change in session diagnostic parameter of the BFD session. This field may be used to indicate that a network device is in a maintenance mode (e.g., by including a particular value associated with a maintenance mode or overload associated with the network device). The state field (Sta) may indicate a current state of the BFD session. The poll field (P) may be used to request verification of connectivity on the link between network device <NUM> and network device <NUM>.

The final field (F) may be used to respond to a BFD control packet in which the poll field is set to request verification of connectivity. The control plane independent field (C) may indicate whether the BFD session is implemented in a forwarding plane and can continue to function through disruptions in the control plane. The authentication present field (A) may indicate whether the BFD session is to be authenticated. The demand mode field (D) may indicate whether the BFD session is to operate in demand mode, in which case BFD control packets may be exchanged based on requests for the BFD control packets. The multipoint (M) field may indicate whether any point-to-multipoint extensions are active for the BFD session.

The detection time multiplier field (Detect Mult) may identify a particular time value by which a time interval for exchanging BFD control packets is to be multiplied. The length field may identify a length of the BFD control packet in bytes. The my discriminator field may identify a unique nonzero discriminator value that may be used to demultiplex a plurality of BFD sessions. The your discriminator field may be used to reflect back a received value in a my discriminator field. The desired minimum transmit interval field (Desired Min Tx Interval) may identify a minimum time interval for transmitting BFD control packets for the BFD session.

The required minimum receive interval (Required Min RX Interval) field may identify a minimum time interval between received BFD Control packets that network device <NUM> or network device <NUM> is capable of supporting. The required minimum echo receive interval (Required Min Echo RX Interval) field may identify a minimum time interval between received BFD Echo packets that network device <NUM> or network device <NUM> is capable of supporting.

In this way, network device <NUM> transmits a BFD control packet to network device <NUM>, which includes a diagnostic code field that may be used to indicate a change in session diagnostic parameter of a BFD session of network device <NUM>. Network device <NUM> configures the diagnostic code field to include a particular value such that the diagnostic code field indicates that the network device is in the maintenance mode. Network device <NUM> may identify the particular value in the diagnostic code field and performs one or more actions associated with a link between network device <NUM> and network device <NUM> to divert forwarding plane traffic away from network device <NUM> while network device <NUM> is in the maintenance mode, without network device <NUM> having to deactivate other network protocols or bring down the link. This decreases consumption of processing, memory, and/or network resources, decreases delays in forwarding plane traffic forwarding, decrease the likelihood of forwarding plane traffic being dropped, and/or the like as a result of network device <NUM> being in the maintenance mode.

As indicated above, <FIG> and <FIG> are provided merely as one or more examples.

<FIG> is a diagram of an example environment <NUM> in which systems and/or methods described herein may be implemented. As shown in <FIG>, environment <NUM> may include one or more network devices <NUM>-<NUM> through <NUM>-n (n ≥ <NUM>) (hereinafter referred to collectively as "network devices <NUM>," and individually as "network device <NUM>") and a network <NUM>. Devices of environment <NUM> may interconnect via wired connections, wireless connections, or a combination of wired and wireless connections. In some implementations, network devices <NUM> may be linked and/or connected together to form a high-availability cluster. In some implementations, the high-availability cluster may include a plurality of nodes (e.g., two or more nodes) that are implemented by network devices <NUM>.

Network device <NUM> includes one or more devices capable of receiving, providing, storing, generating, and/or processing information. In some implementations, network device <NUM> may include a firewall, a router, a gateway, a switch, a bridge, a wireless access point, a base station (e.g., eNodeB, NodeB, gNodeB, and/or the like), and/or the like. In some implementations, network device <NUM> may be implemented as a physical device implemented within a housing, such as a chassis. In some implementations, network device <NUM> may be implemented as a virtual device implemented by one or more computer devices of a cloud computing environment or a data center.

In some implementations, a network device <NUM> may determine to transition to a maintenance mode, may generate a BFD control packet that includes a diagnostic code field that indicates that the network device <NUM> is in the maintenance mode, may transmit, to another network device <NUM>, the BFD control packet to permit the other network device <NUM> to perform an action based on the diagnostic code field that indicates that the network device <NUM> is in the maintenance mode, and/or the like. In some implementations, the other network device <NUM> may process the BFD control packet to determine the indication that the network device <NUM> is in the maintenance mode and may perform, based on the indication that the network device <NUM> is in the maintenance mode, one or more actions associated with the link.

Network <NUM> includes one or more wireless networks. For example, network <NUM> may include a cellular network (e.g., a long-term evolution (LTE) network, a code division multiple access (CDMA) network, a <NUM> network, a <NUM> network, a <NUM> network, another type of cellular network, and/or the like), a wireless local area network (WLAN) (e.g., a Wi-Fi network, an unlicensed spectrum wireless network, and/or the like), a wireless peer-to-peer (P2P) network (e.g., Wi-Fi direct, Bluetooth, and/or the like), and/or the like, and/or a combination of these or other types of networks.

<FIG> and <FIG> are diagrams of example components of one or more devices of <FIG>. <FIG> is a diagram of example components of a device <NUM>. In some implementations, device <NUM> may correspond to device <NUM>. In some implementations, device <NUM> may include one or more devices <NUM> and/or one or more components of device <NUM>. As shown in <FIG>, device <NUM> may include a bus <NUM>, a processor <NUM>, a memory <NUM>, a storage component <NUM>, an input component <NUM>, an output component <NUM>, and a communication interface <NUM>.

Bus <NUM> includes a component that permits communication among the components of device <NUM>. Processor <NUM> is implemented in hardware, firmware, or a combination of hardware and software. Processor <NUM> takes the form of a central processing unit (CPU), a graphics processing unit (GPU), an accelerated processing unit (APU), a microprocessor, a microcontroller, a digital signal processor (DSP), a field-programmable gate array (FPGA), an application-specific integrated circuit (ASIC), or another type of processing component. In some implementations, processor <NUM> includes one or more processors capable of being programmed to perform a function. Memory <NUM> includes a random access memory (RAM), a read only memory (ROM), and/or another type of dynamic or static storage device (e.g., a flash memory, a magnetic memory, and/or an optical memory) that stores information and/or instructions for use by processor <NUM>.

A computer readable medium may include non-transitory type media such as physical storage media including storage discs and solid state devices. A computer readable medium may also or alternatively include transient media such as carrier signals and transmission media. A computer-readable storage medium is defined herein as a non-transitory memory device. A memory device includes memory space within a single physical storage device or memory space spread across multiple physical storage devices.

Communication interface <NUM> includes a transceiver-like component (e.g., a transceiver and/or a separate receiver and transmitter) that enables device <NUM> to communicate with other devices, such as via a wired connection, a wireless connection, or a combination of wired and wireless connections. Communication interface <NUM> may permit device <NUM> to receive information from another device and/or provide information to another device. For example, communication interface <NUM> may include an Ethernet interface, an optical interface, a coaxial interface, an infrared interface, a radio frequency (RF) interface, a universal serial bus (USB) interface, a Wi-Fi interface, a cellular network interface, or the like.

Device <NUM> may perform one or more processes described herein. Device <NUM> may perform these processes based on processor <NUM> executing software instructions stored by a non-transitory, or transitory, computer-readable medium, such as memory <NUM> and/or storage component <NUM>. A computer-readable medium may be defined herein as a non-transitory, or transitory, memory device. A memory device includes memory space within a single physical storage device or memory space spread across multiple physical storage devices.

<FIG> is a diagram of example components of a device <NUM>. In some implementations, device <NUM> may correspond to device <NUM>. In some implementations, device <NUM> may include one or more devices <NUM> and/or one or more components of device <NUM>. As shown in <FIG>, device <NUM> may include one or more input components <NUM>-<NUM> through <NUM>-B (B ≥ <NUM>) (hereinafter referred to collectively as input components <NUM>, and individually as input component <NUM>), a switching component <NUM>, one or more output components <NUM>-<NUM> through <NUM>-C (C ≥ <NUM>) (hereinafter referred to collectively as output components <NUM>, and individually as output component <NUM>), and a controller <NUM>.

Input components <NUM> may be points of attachment for physical links and may be points of entry for incoming traffic, such as packets. In some implementations, input component <NUM> may send and/or receive packets.

In some implementations, switching component <NUM> may enable input components <NUM>, output components <NUM>, and/or controller <NUM> to communicate.

In some implementations, output component <NUM> may send packets and/or receive packets. In some implementations, input component <NUM> and output component <NUM> may be implemented by the same set of components (e.g., an input/output component may be a combination of input component <NUM> and output component <NUM>).

In some implementations, controller <NUM> may include a RAM, a ROM, and/or another type of dynamic or static storage device (e.g., a flash memory, a magnetic memory, an optical memory, and/or the like) that stores information and/or instructions for use by controller <NUM>.

Controller <NUM> may create routing tables based on the network topology information, create forwarding tables based on the routing tables, and forward the forwarding tables to input components <NUM> and/or output components <NUM>.

Controller <NUM> may perform one or more processes described herein. Controller <NUM> may perform these processes in response to executing software instructions stored by a computer-readable medium. A "computer-readable medium" as used herein is a non-transitory, or transitory, memory device. A memory device includes memory space within a single physical storage device or memory space spread across multiple physical storage devices.

<FIG> is a flow chart of an example process <NUM> for transmitting a BFD control packet to indicate maintenance mode operation. In some implementations, one or more process blocks of <FIG> may be performed by a first network device (e.g., network device <NUM>, device <NUM>, device <NUM>, and/or the like). In some implementations, one or more process blocks of <FIG> may be performed by another device or a group of devices separate from or including the first network device, such as another network device and/or the like.

As shown in <FIG>, process <NUM> may include determining to transition to a maintenance mode (block <NUM>). For example, the first network device (e.g., using processor <NUM>, memory <NUM>, storage component <NUM>, input component <NUM>, output component <NUM>, communication interface <NUM>, input component <NUM>, switching component <NUM>, output component <NUM>, controller <NUM>, and/or the like) may determine to transition to a maintenance mode, as described above.

As further shown in <FIG>, process <NUM> may include generating a BFD control packet that includes a diagnostic code field that indicates that the first network device is in the maintenance mode (block <NUM>). For example, the first network device (e.g., using processor <NUM>, memory <NUM>, storage component <NUM>, input component <NUM>, output component <NUM>, communication interface <NUM>, input component <NUM>, switching component <NUM>, output component <NUM>, controller <NUM>, and/or the like) may generate a BFD control packet that includes a diagnostic code field that indicates that the first network device is in the maintenance mode, as described above.

As further shown in <FIG>, process <NUM> may include transmitting, to a second network device, the BFD control packet to permit the second network device to perform an action based on the diagnostic code field that indicates that the first network device is in the maintenance mode (block <NUM>). For example, the first network device (e.g., using processor <NUM>, memory <NUM>, storage component <NUM>, input component <NUM>, output component <NUM>, communication interface <NUM>, input component <NUM>, switching component <NUM>, output component <NUM>, controller <NUM>, and/or the like) may transmit, to a second network device, the BFD control packet to permit the second network device to perform an action based on the diagnostic code field that indicates that the first network device is in the maintenance mode, as described above.

In a first implementation, the diagnostic code field includes a particular value, associated with an overload enabled indicator, indicating that the first network device is in the maintenance mode. In a second implementation, alone or in combination with the first implementation, process <NUM> includes determining to transition from the maintenance mode to an active mode; generating another BFD control packet that includes an indication that the first network device is in the active mode; and transmitting, to the second network device, the other BFD control packet to permit the second network device to perform an action based on the indication that the first network device is in the active mode. In a third implementation, alone or in combination with one or more of the first and second implementations, the indication that the first network device is in the active mode comprises a particular value in the diagnostic code field included in the other BFD control packet, wherein the particular value is associated with a no diagnostic indicator.

<FIG> is a flow chart of an example process <NUM> for receiving a BFD control packet to indicate maintenance mode operation. In some implementations, one or more process blocks of <FIG> may be performed by a first network device (e.g., network device <NUM>, device <NUM>, device <NUM>, and/or the like). In some implementations, one or more process blocks of <FIG> may be performed by another device or a group of devices separate from or including the first network device, such as another network device and/or the like.

As shown in <FIG>, process <NUM> may include receiving, from a second network device, a BFD control packet that includes an indication that the second network device is in a maintenance mode (block <NUM>). For example, the first network device (e.g., using processor <NUM>, memory <NUM>, storage component <NUM>, input component <NUM>, output component <NUM>, communication interface <NUM>, input component <NUM>, switching component <NUM>, output component <NUM>, controller <NUM>, and/or the like) may receive, from a second network device, a BFD control packet that includes an indication that the second network device is in a maintenance mode, as described above.

As further shown in <FIG>, process <NUM> may include processing the BFD control packet to determine the indication that the second network device is in the maintenance mode (block <NUM>). For example, the first network device (e.g., using processor <NUM>, memory <NUM>, storage component <NUM>, input component <NUM>, output component <NUM>, communication interface <NUM>, input component <NUM>, switching component <NUM>, output component <NUM>, controller <NUM>, and/or the like) may process the BFD control packet to determine the indication that the second network device is in the maintenance mode, as described above.

As further shown in <FIG>, process <NUM> may include performing, based on the indication that the second network device is in the maintenance mode, one or more actions associated with a link between the first network device and the second network device (block <NUM>). For example, the first network device (e.g., using processor <NUM>, memory <NUM>, storage component <NUM>, input component <NUM>, output component <NUM>, communication interface <NUM>, input component <NUM>, switching component <NUM>, output component <NUM>, controller <NUM>, and/or the like) may perform, based on the indication that the second network device is in the maintenance mode, one or more actions associated with a link between the first network device and the second network device, as described above.

In a first implementation, the indication that the second network device is in the maintenance mode comprises a particular value in a diagnostic code field included in the BFD control packet. In a second implementation, alone or in combination with the first implementation, the particular value is associated with an overload enabled indicator. In a third implementation, alone or in combination with one or more of the first and second implementations, process <NUM> includes setting an overload detected parameter, associated with a BFD session of the first network device, to a particular value. In a fourth implementation, alone or in combination with one or more of the first through third implementations, process <NUM> includes increasing an OSPF link cost of the link between the first network device and the second network device.

In a fifth implementation, alone or in combination with one or more of the first through fourth implementations, process <NUM> includes transmitting, to a third network device, an indication of the OSPF link cost based on increasing the OSPF link cost of the link. In a sixth implementation, alone or in combination with one or more of the first through fifth implementations, process <NUM> includes increasing a route cost of a route that includes the link between the first network device and the second network device. In a seventh implementation, alone or in combination with one or more of the first through sixth implementations, process <NUM> includes transmitting, to a third network device, an indication of the route cost based on increasing the route cost of the route.

In an eighth implementation, alone or in combination with one or more of the first through seventh implementations, process <NUM> includes decreasing a border gateway protocol (BGP) local preference of a route that includes the link between the first network device and the second network device. In a ninth implementation, alone or in combination with one or more of the first through eighth implementations, process <NUM> includes transmitting, to a third network device, an indication of the BGP local preference based on decreasing the BGP local preference of the route.

As further shown in <FIG>, process <NUM> may include transmitting, to a second network device, a BFD control packet that includes an indication that the first network device is in the maintenance mode (block <NUM>). For example, the first network device (e.g., using processor <NUM>, memory <NUM>, storage component <NUM>, input component <NUM>, output component <NUM>, communication interface <NUM>, input component <NUM>, switching component <NUM>, output component <NUM>, controller <NUM>, and/or the like) may transmit, to a second network device, a BFD control packet that includes an indication that the first network device is in the maintenance mode, as described above.

In a first implementation, the indication that the first network device is in the maintenance mode comprises a particular value in a diagnostic code field included in the BFD control packet. In a second implementation, alone or in combination with the first implementation, the particular value is associated with an overload enabled indicator. In a third implementation, alone or in combination with one or more of the first and second implementations, process <NUM> includes determining to transition from the maintenance mode to an active mode; and transmitting, to the second network device, another BFD control packet that includes an indication that the first network device is in the active mode.

In a fourth implementation, alone or in combination with one or more of the first through third implementations, the indication that the first network device is in the active mode comprises a particular value in a diagnostic code field included in the BFD control packet. In a fifth implementation, alone or in combination with one or more of the first through fourth implementations, the particular value is associated with a no diagnostic indicator.

As used herein, the term traffic or content may include a set of packets. A packet may refer to a communication structure for communicating information, such as a protocol data unit (PDU), a network packet, a datagram, a segment, a message, a block, a cell, a frame, a subframe, a slot, a symbol, a portion of any of the above, and/or another type of formatted or unformatted unit of data capable of being transmitted via a network.

No element, act, or instruction used herein should be construed as critical or essential unless explicitly described as such. Also, as used herein, the articles "a" and "an" are intended to include one or more items, and may be used interchangeably with "one or more. " Further, as used herein, the article "the" is intended to include one or more items referenced in connection with the article "the" and may be used interchangeably with "the one or more. " Furthermore, as used herein, the term "set" is intended to include one or more items (e.g., related items, unrelated items, a combination of related and unrelated items, etc.), and may be used interchangeably with "one or more. " Where only one item is intended, the phrase "only one" or similar language is used. Also, as used herein, the terms "has," "have," "having," or the like are intended to be open-ended terms. Further, the phrase "based on" is intended to mean "based, at least in part, on" unless explicitly stated otherwise. Also, as used herein, the term "or" is intended to be inclusive when used in a series and may be used interchangeably with "and/or," unless explicitly stated otherwise (e.g., if used in combination with "either" or "only one of').

Claim 1:
A method, comprising:
determining (<NUM>), by a first network device, to transition to a maintenance mode; and
generating (<NUM>), by the first network device, a bidirectional forwarding detection "BFD" control packet that includes a diagnostic code field that indicates that the first network device is in the maintenance mode; and
transmitting (<NUM>), by the first network device and to a second network device, the BFD control packet for permitting the second network device to perform (<NUM>) an action associated with a link between the first network device and the second network device based on the diagnostic code field that indicates that the first network device is in the maintenance mode, wherein the action causes forwarding plane traffic to be diverted away from the first network device.