WO2016122934A1

WO2016122934A1 - Multi-chassis link aggregation (lag) switches

Info

Publication number: WO2016122934A1
Application number: PCT/US2016/013991
Authority: WO
Inventors: Venkatavaradhan Devarajan; Chivukula Koundinya; V N S Ramaprasad ALLU
Original assignee: Hewlett Packard Development Co LP
Current assignee: Hewlett Packard Development Co LP
Priority date: 2015-01-30
Filing date: 2016-01-20
Publication date: 2016-08-04
Anticipated expiration: 2017-07-30

Abstract

Example implementations relate to selecting an active switch in a multi-chassis link aggregation (LAG) environment. For example, a switch to receive state parameters from at least one peer switch through an inter-switch link (ISL) is described. The switch is also to determine failure of the ISL based on control plane and forwarding plane traffic, and keep-alive messages received from the at least one peer switch. The switch is further to compare the state parameters received from the at least one peer switch with state parameters of the switch; and elect an active switch from amongst the at least one peer switch and the switch based on the comparison.

Description

MULTI-CHASSIS LINK AGGREGATION (LAG) SWITCHES

BACKGROUND

[0001 ] In a general networking topology of communication networks, an access switch is connected to another switch through a physical link. Different network devices are connected to the access switch for the purpose of communication and transfer of data. For redundancy and effective bandwidth utilization, more than one physical links between the access switches may be aggregated so as to appear as a single link to the access switch. This is generally referred to as 'link aggregation'. Link aggregation, by utilizing multiple physical links in parallel, allows increase in the physical link speed beyond the limits of a single physical link and also allows increase in fault tolerance for higher availability of network components.

BRIEF DESCRIPTION OF DRAWINGS

[0002] The detailed description is provided with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to reference like features and components.

[0003] Fig. 1 illustrates an example multi-chassis Link-Aggregation (LAG) environment, implementing multiple distribution layer switches, according to an example implementation of the present subject matter;

[0004] Fig. 2(a) illustrates elements of a distribution layer switch, according to an example implementation of the present subject matter;

[0005] Fig. 2(b) illustrates various other elements of the distribution layer switch, according to another example implementation of the present subject matter; [0006] Fig.3 is a flowchart representative of an example method of selecting an active distribution layer switch;

[0007] Fig. 4 is a flowchart representative of another example method of selecting an active distribution layer switch; and

[0008] Fig.5 illustrates an example multi-chassis LAG environment, implementing a non-transitory computer-readable medium for selecting an active distribution layer switching a multi-chassis LAG environment.

DETAILED DESCRIPTION

[0009] Communication networks are often segregated into three layers, i.e., a core layer, a distribution layer, and an access layer. The core layer provides high-speed communication capability to network devices of distribution layer and access layer. In such communication networks, client devices and computing systems are provided with the communication capability by the access layer. The distribution layer acts as an interface between the core layer and the access layer and manages routing, filtering, and quality of service (QoS) policies of the communication network. For the sake of explanation, the switches providing communication capabilities at the distribution layer have been referred to as distribution layer switches and the switches providing communication capabilities at the access layer have been referred to as access switches.

[0010] In the multi-chassis link aggregation (LAG) environments, a single access switch is aggregated to a pair of distribution layer switches for resiliency and higher bandwidth. The distribution layer switch pair uses a dedicated point- point physical link referred to here as the 'Inter-Switch Link (ISL)' for exchanging control plane traffic. The ISL helps the distribution layer switch pair to maintain states regarding their multi-chassis link aggregations and also allows passage of data plane traffic between the distribution layer switch pair from time to time. In some implementations, the access switch may also be aggregated to more than two distribution layer switches. In such situations, all the multiple distribution layer switches may be connected through dedicated ISL. [0011] In situations of ISL failure, since control plane traffic between the distribution layer switches cannot be established, one distribution layer switch from amongst the distribution layer switch pair is to be selected as an active distribution layer switch such that the access switch can directly communicate data to the active distribution layer switch. However, such selection of the active switch causes connectivity outages in situations when an appropriate distribution layer switch, such as the one acting as a gateway, is not selected as the active distribution layer switch.

[0012] According to example implementations of the present subject matter, systems and methods for selecting an active switch in a multi-chassis LAG environment are described. The described systems and methods may allow selection of an active switch from amongst a pair of switches. For example, the present subject matter may allow selection of an active distribution layer switch from amongst a distribution layer switch pair providing aggregated link to an access switch in a multi-chassis LAG environment. In another implementation, the present subject matter may allow selection of the active switch from amongst multiple distribution layer switches providing aggregated link to the access switch in the multi-chassis LAG environment.

[0013] The described systems and methods may be implemented in various switches implementing link aggregation techniques in the communication network. Although, the description herein is with reference to switches implemented in a multi-chassis LAG environment, the methods and described techniques may be implemented in other type of switches implementing different link aggregation techniques, albeit with a few variations. Various implementations of the present subject matter have been described below by referring to several examples.

[0014] For the sake of explanation, the distribution layer switches providing link aggregation have been referred to as a first switch and a second switch, hereinafter. Further, the distribution layer switches have also been commonly referred to as pair of distribution layer switches and individually referred to as peer switch, in reference to another distribution layer switch, hereinafter.

[0015] In operation, an access switch may be aggregated to a pair of distribution layer switches for the purpose of link aggregation. In one example implementation of the present subject matter, the pair of distribution layer switches may be connected to each other through an ISL link for the purpose of communicating control plane traffic and data plane traffic. Further, in addition to the ISL, the distribution layer switch pair may also include a dedicated 'keep- alive' physical link for use in situations of ISL failure. The distribution layer switches may exchange keep-alive messages through the 'keep-alive' physical link to allow each distribution layer switch to ascertain that the peer switch is alive and the failure of communication is due to ISL failure, and not due to failure of the peer switch as a whole.

[0016] In an example implementation of the present subject matter, each distribution layer switch may exchange state parameters corresponding to its control plane and forwarding plane states through the ISL. That is, the state parameters may indicate state of each distribution layer switch with respect to their control plane and forwarding plane.

[0017] In an implementation, failure of the ISL between the peer switches may be identified. The identification of failure of the ISL may be based on determination of outage of control plane traffic and data plane traffic between the peer switches while the keep-alive messages are still being communicated through the 'keep-alive' physical link. Upon identification of the failure of the ISL, the state parameters of first switch may be compared to the state parameters of the second switch.

[0018] Based on the comparison of the state parameters, one switch from amongst the distribution layer switch pair may be identified as the active LAG switch, referred to as the active switch, hereinafter. The active switch may allow communication with the access switch. Therefore, based on the comparison of the state parameters, one switch from amongst the pair of distribution layer switches may be identified as the active switch. In an example implementation of the present subject matter, the described method of selection of a active switch may be implemented by each distribution layer switch where based on the comparison of the state parameters corresponding to peer switches, an active switch may be identified.

[0019] The selection of the active switch based on comparison of the state parameters may minimize traffic outages during ISL failure. Further, the utilization of the ISL for exchange of the state parameters does not necessitate use of any additional or different control plane protocol. Furthermore, by the exchange of state parameters between the peer switches on an ongoing basis, any dynamic changes in the state of the distribution layer switches can be accounted for, while selecting the active switch.

[0020] The above systems and methods are further described with reference to Fig. 1 to Fig. 5. It should be noted that the description and figures merely illustrate the principles of the present subject matter along with examples described herein and, should not be construed as a limitation to the present subject matter. It is thus understood that various arrangements may be devised that, although not explicitly described or shown herein, embody the principles of the present subject matter. Moreover, all statements herein reciting principles, aspects, and embodiments of the present subject matter, as well as specific examples thereof, are intended to encompass equivalents thereof.

[0021] Fig. 1 schematically illustrates a computing network 100, implementing a multi-chassis LAG environment, according to an example implementation of the present subject matter. The computing network 100 may either be a public distributed environment or may be a private closed computing environment. According to an implementation of the present subject matter, the computing network 100 may implement a plurality of distribution layer switches, such as distribution layer switch 102-1 and distribution layer switch 102-2. For ease of explanation, the distribution layer switch 102-1 and the distribution layer switch 102-2 have been individually referred to as switch 102, and commonly referred to as pair of distribution layer switches 102, hereinafter. The multi- chassis LAG environment may also include different access switches, such as access switch 104-1 , and access switch 104-2. For the sake of explanation, the access switch 104-1 and the access switch 104-2 have been individually referred to as access switch 104, and commonly referred to as access switches 104, hereinafter. Each switch 102 may provide connectivity between one or more access switches 104 and a communication network 106.

[0022] Each of the access switches 104 may be aggregated to a pair of distribution layer switches, such as the pair of distribution layer switches 102 in the multi-chassis LAG environment. The physical links between the access switch 104-1 and the pair of distribution layer switches 102 may be aggregated and represented as 108-1 . Similarly, the physical links between the access switch 104-2 and the pair of distribution layer switches 102 may also be aggregated and represented as108-2. Although, for the sake of explanation, the forgoing explanation has been made considering that the access switches 104 are aggregated to a pair of distribution layer switches, it would be appreciated that the access switches 104 may be aggregated to more than two distribution layer switches as well.

[0023] The switch 102 may be implemented as, but not limited to, a distribution layer switching unit, a switch-router, or any device capable of switching data packets at distribution layer and provide connectivity between the communication network 106 and the access switches 104. Further, the access switches 104 may include any network devices, such as routers, switching units, computing devices, and the like.

[0024] Further, although merely the pair of distribution layer switches 102 and a couple of access switches 104-1 and 104-2 have been depicted in the multi-chassis LAG environment, it would be understood that the multi-chassis LAG environment may implement several other distribution layer switches and access switches.

[0025] The communication network 106 may be a wireless network, a wired network, or a combination thereof. The communication network 106 maybe a core network that may provide paths for the exchange of information between different sub-networks. The communication network 106 may either be a dedicated network or a shared network, which represents an association of the different types of networks that use a variety of protocols, for example, Hypertext Transfer Protocol (HTTP), Transmission Control Protocol/Internet Protocol (TCP/IP), etc., to communicate with each other.

[0026] The communication network 106 may also include individual networks, such as, but are not limited to, Global System for Communication (GSM) network, Universal Telecommunications System (UMTS) network, Long Term Evolution (LTE) network, Personal Communications Service (PCS) network, Time Division Multiple Access (TDMA) network, Code Division Multiple Access (CDMA) network, Next Generation Network (NGN), Public Switched Telephone Network (PSTN), and Integrated Services Digital Network (ISDN). Depending on the implementation, the communication network 106 may include various network entities, such as base stations, gateways and routers; however, such details have been omitted to maintain the brevity of the description.

[0027] In one example implementation, the pair of distribution layer switches 102 may be connected through a dedicated point-to-point Inter-Switch Link (ISL) 1 10, for exchanging control plane traffic and data plane traffic with each other, from time to time. The ISL 1 10 may therefore allow each switch 102 to maintain states regarding their multi-chassis link aggregations. In said implementation, the pair of distribution layer switches 102 may also include a 'keep-alive' physical link (not shown) to exchange keep-alive messages.

[0028] In operation, each switch 102 may exchange state parameters with their peer switch 102 from time to time. It would be understood that in the pair of distribution layer switches 102, the distribution layer switch 102-2 would be considered as the peer switch 102 for the distribution layer switch 102-1 and the distribution layer switch 102-1 would be considered as the peer switch 102 for the distribution layer switch 102-2. [0029] In an example implementation, situations of failure of the ISL1 10 may be identified. Based on the identification, analysis module 1 12 of the switch 102 may compare the state parameters and may analyze the result to select an active switch from amongst the pair of distribution layer switches 102. Such example functionalities and example modules have been further described in more detail in reference to Fig. 2(a).

[0030] Fig. 2(a) schematically illustrates components of the switch 102, according to an example implementation of the present subject matter. In one implementation of the present subject matter, the switch 102 may include processor(s) 202. In an example, an analysis module 1 12 and a communication module 212 are coupled to the processor(s) 202.

[0031] In accordance with one example implementation of the present subject matter, the communication module 212 may receive state parameters from at least one peer switch through an ISL that provides a communication link between the switch 102 and at least one peer switch of the multi-chassis link aggregation environment. As mentioned previously, the state parameters are indicative of control plane and forwarding plane states of the switch and the at least one peer switch.

[0032] The communication module 212 may also determine failure of the ISL based on control plane and forwarding plane traffic, and keep-alive messages received from the at least one peer switch. In case the communication module 212 determines an ISL failure to have occurred, it may invoke the analysis module 1 12. In an example, the analysis module 1 12 may compare the state parameters received from the at least one peer switch with state parameters of the switch and elects an active switch from amongst the at least one peer switch and the switch based on the comparison.

[0033] The operation of the switch 102 to elect the active switch is explained in details in reference to Fig. 2b.

[0034] Referring to Fig. 2b, in one example implementation the switch 102 comprises interface(s) 204, memory 206, modules 208, and data 210 coupled to the processor(s) 202. The processor(s) 202 may be implemented as microprocessor(s), microcomputer(s), microcontroller(s), digital signal processor(s), central processing unit(s), state machine(s), logic circuit(s), and/or any device(s) that manipulate signals based on operational instructions. Among other capabilities, the processor may fetch and execute computer-readable instructions stored in a memory. The functions of the various 'processor(s)' may be provided through the use of dedicated hardware as well as hardware capable of executing machine readable instructions.

[0035] The interface(s) 204 may include a variety of machine readable instructions-based interfaces and hardware interfaces that allow the switch 102 to interact with different entities, such as peer switches, access switches 104 and the communication network 106. Further, the interface(s) 204 may enable the components of the switch 102 to communicate with other components, such as the processors(s) 202 with the modules 208 and data 210.

[0036] The memory 206 may include any computer-readable medium including, for example, volatile memory (e.g., RAM), and/or non-volatile memory (e.g., EPROM, flash memory, Memristor, etc.). The memory 206 maybe communicatively coupled to the processor 202 and different components of switch 102.

[0037] In one example implementation of the present subject matter, the modules 208 of the switch 102 may include different module(s). The modules 208 may include other module(s) 214 in addition to the analysis module 1 12 and the communication module 212. The modules 208 may be communicatively coupled to the processor(s) 202 of the switch 102. The module(s), amongst other things, include routines, services, programs, objects, components, data structures, and the like, which perform particular tasks or implement particular abstract data types. The modules 208 may further include sub modules that supplement applications on the switch 102, for example, services of the firmware. The other modules 214 may support different functions of the switch 102 and may provide different functionalities for the purpose of functioning of the switch 102. [0038] The data 210 serves, amongst other things, as a repository for storing data that may be fetched, processed, received, or generated by the module(s) of the switch 102. The data 210 may include state parameter data 216 and other data 218. Although the data 210 is shown internal to the switch 102, it may be understood that the data 1 14 may reside in an external repository (not shown), which may be communicatively coupled to the switch 102. The switch 102 may communicate with the external repository through the interface(s) 204 to obtain information from the data 210.

[0039] In an example implementation of the present subject matter, the communication module 212 of the switch 102 may communicate state parameters with the peer switch 102 from time to time through the ISL 1 10. The communication of the state parameters may be based on ISL control plane protocol used to exchange control plane and data plane traffic between the switches, through the ISL 1 10.

[0040] The state parameters may indicate state of the switch 102 with respect to its control plane and forwarding plane. For example, the state parameters may provide information about the Virtual Router Redundancy Protocol (VRRP) master interfaces available with the switch 102. Similarly, the state parameters may also provide information about the active IPv4 and IPv6 routes transiting the switch 102.

[0041] In an implementation, apart from the number of VRRP master interfaces available with the switch 102 and the number of active Internet IPv4 and IPv6 routes transiting the switch 102, the state parameters may also indicate about the networks directly associated with the switch 102, total bandwidth capacity of LAG physical links associated with switch 102, and spanning-tree role (root versus non root) across instances associated with the switch 102. Therefore, the state parameters may indicate the state of the switch 102 from time to time.

[0042] In one example implementation, the communication module 212 may share the state parameters with the peer switch 102 after every predetermined time period. For example, the state parameters may be exchanged after every 10 milliseconds (ms) with the peer switch102. In another example, the exchange of state parameters may be based on exchange of control plane and data plane traffic between the pair of switches 102. That is, when control plane information or data plane information is exchanged between the peer switch 102, the communication module 212 may communicate updated state parameters with the peer switch 102.

[0043] As described, the communication module 212 may communicate the state parameters through the ISL 1 10 based on the ISL control plane protocol. In an example implementation, an ISL control plane protocol packet may be extended to carry additional information of the state parameters. Table 1 , depicts the inclusion of state parameters into the control plane protocol packet where state parameters are type-length-value (TLV) based and may lend itself well for extensions.

Octets

TLV_type= VRRP Master Information 1

lnformation_Length = 2 1

Number of VRRP Master Interfaces 2

TLV_type = Routes Transit Information 1

lnformation_Length = 8 1

Number of IPV4 active transit routes 4

Number of IPV6 active transit routes 4

TLV_type = Directly connected networks Information 1

lnformation_Length = 16 1

Number of directly connected IPV4 non-redundant

Networks 4

Number of directly connected IPV6 non-redundant

Networks 4

Number of directly connected IPV4 redundant

Networks 4

Number of directly connected IPV6 redundant

Networks 4

TLV_type = Bandwidth Information 1

lnformation_Length = 4 1

Total Bandwidth capacity of all LAG physical

interfaces 4

TLV_type = Spanning tree role information 1

lnformation_Length = 4 1 Number of root instances 2

Number of non-root instances 2

TLV_type = Priority Information 1

lnformation_Length = 4 1

User configured priority 4

TLV_type = Terminator 1

Terminator length = 0 1

Table 1

[0044] Based on the above depicted Table 1 , it would be understood that the state parameter information may be included in the format of ISL protocol message structure and communicated through the ISL 1 10. Although the communication of the state parameters has been defined to be based on the ISL control plane protocol, it would be understood that for the purpose of communicating the state parameters, the communication module 212 may utilize any other available technique and suitable protocol.

[0045] As explained previously, the peer switch may also share the state parameters associated with it from time to time. Accordingly, in one example implementation of the present subject matter, the communication module 212 may also receive communication parameters associated with peer switch.

[0046] The state parameters received from the peer switch may be stored in the state parameter data 216. Since the updated state parameters are received after every predetermined time period, the communication module 212 may store the updated state parameters in the state parameters data.

[0047] In one example implementation of the present subject matter, the communication module 212 may also identify failure of the ISL 1 10. The communication module 212 may monitor traffic being exchanged with the peer switch though the ISL 1 10, and in situations of failure of the traffic exchange, failure of the ISL 1 10 may be determined based on exchanged keep-alive messages. That is, if the keep-alive messages are being exchanged with the peer switch, and the exchange of traffic through the ISL 1 10 has failed, the communication module 212 may identify the ISL 1 10 to have failed. [0048] It would be understood that a successful exchange of keep-alive messages between the switch 102 and the peer switch may indicate that the peer switch is up and communicating data with its peer switches. Therefore, in situations where the traffic exchange between the switch 102 and the peer switch has failed, the ISL 1 10 would be identified to have failed.

[0049] The analysis module 1 12, in situations of ISL 1 10 failure, may compare the state parameters corresponding to the switch 102 and the peer switch, to elect an active switch from among the switch 102 and the peer switch. In one example implementation, the comparison of the state parameters may be a parameter-by-parameter comparison where one of the switch may be elected as active switch by sequential comparison of state parameters, while other parameters are not compared. In such situations, if the state of both the switches is comparable with respect to the first state parameter, the state of the switches with respect to the second state parameter may then be compared, and so on.

[0050] For example, in a parameter-by-parameter comparison, the analysis module 1 12 may consider the number of VRRP master interfaces as the first state parameter for comparison. Accordingly, the number of VRRP master interfaces available with the switch 102 and the peer switch may be compared. Based on the comparison, any switch, from amongst the switch 102 and the peer switch, with more number of VRRP master interfaces may be elected as the active switch. In said example, if both the switch 102 and the peer switch are identified to include same number of VRRP master interfaces, a second state parameter may be compared.

[0051] In an example, the analysis module 1 12 may consider the number of IPv4/IPv6 networks directly associated to be the second state parameter for comparison. Any switch with more number of IPv4/IPv6 networks directly associated with them may be elected as the active switch. Further, the analysis module 1 12 may also consider the number of active Internet IPv4/IPv6 routes transiting each switch to be considered as the third state parameter for comparison. Similarly, the analysis module 1 12 may also consider other state parameters, one after another and elect an active switch.

[0052] In another example, analysis module 1 12 may consider all the state parameters of the switch 102 and compare them with the state parameters of the peer switch. In said example of the present subject matter, the analysis module 1 12 may compare the state parameters based on weighted comparison. In weighted comparison, the analysis module 1 12 may compare all the state parameters and based on pre-assigned weights, compute a weighted score for each switch upon comparison. Thereafter, based on the computed weighted score, an active switch may be elected from amongst the switch 102 and the peer switch.

[0053] Therefore, based on different techniques of comparison, the analysis module 1 12 may compare the state parameters corresponding to the switch 102 and the peer switch, to elect an active switch.

[0054] In an example implementation of the present subject matter, a user configured role priority may also be defined based on which an election of the active switch may be performed. In such a scenario, a user, such as a network administrator of the multi-chassis LAG may configure a priority role corresponding to a particular switch and the analysis module 1 12 may elect the active switch based on the defined user configured role priority.

[0055] For instance, the user may define the user configured role priority for the switch 102. In such a scenario, upon detection of ISL failure, the analysis module 1 12 may elect the switch 102 as the active switch between the switch 102 and the peer switch.

[0056] The analysis module 1 12, in one implementation, may consider the user configured role priority as an overriding parameter such that the user configured role priority may supersede the comparison result of the state parameters and the active switch may be elected based on the user configured role priority. [0057] In another implementation, the analysis module 1 12 may consider the user configured role priority as one of the state parameters and may utilize it during comparison of the state parameters. For example, in a parameter-by- parameter comparison, user configured role priority may be considered as one of the state parameter and may be compared at a suitable position. For instance, after comparison of number of VRRP master interfaces, the user configured role priority may be compared as the second state parameter. The order of comparison for the user configured role priority in the parameter-by- parameter comparison may vary and may be preconfigured in different implementations.

[0058] Similarly, in the weighted comparison technique, the user configured role priority may also be assigned a weightage. Based on the weightage assigned to the state parameters and the user configured role priority, the analysis module 1 12 may generate the weighted score, and may accordingly elect the active switch.

[0059] Therefore, the analysis module 1 12, based on the comparison of the state parameters, may elect an active switch between the switch 102 and the peer switch.

[0060] Fig. 3 and 4 illustrate method 300 and 400 for selecting an active switch in a multi-chassis LAG environment. The order in which the methods 300 and 400 are described is not intended to be construed as a limitation, and any number of the described method blocks may be combined in any order to implement the methods 300 and 400, or any other alternative methods. Furthermore, the methods 300 and 400 may be implemented by processor(s) or computing system(s) through any suitable hardware, non-transitory machine readable instructions, or combination thereof.

[0061] It may be understood that steps of the methods 300 and 400 may be performed by programmed computing systems. The steps of the methods 300 and 400 may be executed based on instructions stored in a non-transitory computer readable medium, as will be readily understood. The non-transitory computer readable medium may include, for example, digital memories, magnetic storage media, such as one or more magnetic disks and magnetic tapes, hard drives, or optically readable digital data storage media.

[0062] Further, although the methods 300 and 400 may be implemented in a variety of switching units and routers of a multi-chassis LAG environment; in an embodiment described in Fig. 3 and 4, the methods 300 and 400 are explained in context of the afore mentioned switch 102, for ease of explanation. Although, for the sake of explanation, the forgoing explanation has been made considering that the access switches 104 are aggregated to a pair of switches 102, it would be appreciated that the access switches 104 may be aggregated to more than two distribution layer switches as well.

[0063] Referring to Fig. 3, in an implementation of the present subject matter, at block 302, an inter-switch link (ISL) failure may be identified. The ISL may provide a communication link between a first switch and a second switch of the multi-chassis LAG environment.

[0064] At block 304, the state parameters corresponding to first switch and the second switch are compared. The state parameters are indicative of control plane and forwarding plane states of the first switch and the second switch. In one implementation, the state parameters may be exchanged between the first switch and the second switch after every predetermined time period.

[0065] At block 306, an active switch from amongst the first switch and the second switch may be determined based on the comparison of the state parameters. In one example implementation, the comparison may be based on one of a parameter-by-parameter comparison, or a weighted comparison.

[0066] Referring to Fig. 4, in an implementation of the present subject matter, at block 402, state parameters are received from a peer switch through an ISL. The ISL may provide a communication link between the switch and at least one peer switch. In one example implementation, a multi-chassis LAG may include multiple switches aggregating physical links of an access switch. Among the multiple switches, each of the comprising switches may be associated with state parameters that may indicate the forwarding plane and control plane state of the switch.

[0067] At block 404, failure of the ISL link between the at least one of switches may be determined. In one implementation, the determination may be based on control plane traffic and forwarding plane traffic being exchanged with the at least one peer switch, and keep-alive messages exchanged with the at least one peer switch. In one implementation, in situations when forwarding plane and control plane traffic failure occurs and the keep-alive messages are being well received from the at least one peer switch, the failure of the ISL may be determined.

[0068] At block 406, the state parameters received from the at least one peer switch are compared with state parameters of the switch. In one example implementation, the state parameters may be indicative of control plane and forwarding plane states of the switch and the peer switch.

[0069] At block 408, an active switch may be elected from amongst the at least one peer switch and the switch based on the comparing. The active switch may allow communication with the access switch while the other switch closes its communication ports during the ISL failure to avoid dual active instances.

[0070] Fig. 5 illustrates a multi-chassis LAG environment 500 implementing a non-transitory computer-readable medium 502, according to an implementation of the present subject matter. In one implementation, the non- transitory computer readable medium 502 may be utilized by switching units and routers, such as the switch 102 (not shown). The switch 102 may be implemented in a multi-chassis LAG environment or a LAG environment. In one implementation, the multi-chassis LAG environment 500 includes a processing resource 504 communicatively coupled to the non-transitory computer readable medium 502 through a communication link 506 connecting to a network 508.

[0071] For example, the processing resource 504 may be implemented in a switch, such as the switch 102 described earlier. The computer readable medium 502 may be, for example, an internal memory device or an external memory device. In one implementation, the communication link 506 may be a direct communication link, such as any memory read/write interface. In another implementation, the communication link 506 may be an indirect communication link, such as a network interface. In such a case, the processing resource 504 may access the computer readable medium 502 through the network 508. The network 508 may be a single network or a combination of multiple networks and may use a variety of different communication protocols.

[0072] In one implementation, the computer readable medium 502 includes a set of computer readable instructions, including the communication module 212, and the analysis module 1 12. The set of computer readable instructions may be accessed by the processing resource 504 through the communication link 506 and subsequently executed to process data communicated with other switches, such as a peer switch.

[0073] In an example implementation, the switch 102 may communicate with other peer switches and exchange state parameters from time to time. The switch 102 may detect failure of an ISL between the switch and the peer switch. In such situations, the analysis module 1 12 of computer readable medium 502 may compare state parameters to elect an active switch between the switch 102 and the peer switch for communication between the network 508 and the access switches.

[0074] Therefore, based on the comparison of the state parameters, one switch from amongst the pair of switches may be identified as the active switch. The selection of the active switch based on comparison of the state parameters may minimize traffic outages during ISL failure. Further, the utilization of the ISL for exchange of the state parameters does not necessitate use of any additional or different control plane protocol. Furthermore, by the exchange of state parameters between the peer switches on an ongoing basis, any dynamic changes in the state of the distribution layer switches can be accounted for while selecting the active switch. [0075] Although implementations of present subject matter have been described in language specific to structural features and/or methods, it is to be understood that the present subject matter is not limited to the specific features or methods described. Rather, the specific features and methods are disclosed and explained in the context of a few implementations for the present subject matter.

Claims

What is claimed is:

1 . A method for selecting an active switch in a multi-chassis link aggregation (LAG) environment, the method comprising:

identifying an inter-switch link (ISL) failure, wherein the ISL provides a communication link between a first switch and a second switch of the multi-chassis LAG environment;

comparing state parameters corresponding to the first switch and the second switch, wherein the state parameters are indicative of control plane and forwarding plane states of the first switch and the second switch; and

determining an active switch from amongst the first switch and the second switch based on the comparison of the state parameters.

2. The method as claimed in claim 1 , wherein the state parameters corresponding to each switch include at least one of number of Virtual Router Redundancy Protocol (VRRP) master interfaces available, number of active Internet Protocol version 4 (IPv4) and Internet Protocol version 6 (IPv6) routes transiting, number of I Pv4 and IPv6 networks directly associated, and total bandwidth capacity of LAG physical links.

3. The method as claimed in claim 1 further comprising exchanging the state parameters among the first switch and the second switch through the ISL based on an ISL control plane protocol.

4. The method as claimed in claim 3, wherein the exchanging comprising communicating the state parameters in a type-length-value (TLV) form among the first switch and the second switch.

5. The method as claimed in claim 1 , wherein the determining is further based on a user configured role priority, wherein the user configured role priority supersedes the state parameters, and wherein the user configured role priority is indicative of user preferences of active switch selection.

6. The method as claimed in claim 1 , wherein the comparing is based on one of a parameter-by-parameter comparison and a weighted comparison.

7. A switch of a multi-chassis link aggregation (LAG) environment, the switch comprising:

a processor;

a communication module coupled to the processor to:

receive state parameters from at least one peer switch through an inter-switch link (ISL), wherein the ISL provides a communication link between the switch and at least one peer switch of the multi-chassis link aggregation environment; and

determine failure of the ISL based on control plane and forwarding plane traffic, and keep-alive messages received from the at least one peer switch; and

an analysis module coupled to the processor to:

compare the state parameters received from the at least one peer switch with state parameters of the switch, wherein the state parameters are indicative of control plane and forwarding plane states of the switch and the at least one peer switch; and

elect an active switch from amongst the at least one peer switch and the switch based on the comparison.

8. The switch as claimed in claim 7, wherein the communication module is further to communicate the election of the active switch to the at least one peer switch.

9. The switch as claimed in claim 8, wherein the state parameters corresponding to each switch include at least one of number of VRRP master interfaces, number of active Internet Protocol version 4 (IPv4) and Internet Protocol version 6 (IPv6) routes transiting, number of IPv4 and IPv6 networks directly associated, total bandwidth capacity of LAG physical links and spanning tree status.

10. The switch as claimed in claim 7, wherein the communication module is to receive the state parameters through the ISL based on an ISL control plane protocol.

1 1 . The switch as claimed in claim 7, wherein the state parameters are received in a type-length-value (TLV) form, from the peer switch.

12. The switch as claimed in claim 7, wherein the analysis module is to further elect the active switch based on a user configured role priority, wherein the user configured role priority supersedes the state parameters, and wherein the user configured role priority is indicative of user preferences of active switch election.

13. The switch as claimed in claim 7, wherein the analysis module is to compare based on one of a parameter-by-parameter comparison and a weighted comparison.

14. A non-transitory computer-readable medium comprising instructions, when executed, cause a processor resource to:

identify an inter-switch link (ISL) failure, wherein the ISL provides a communication link between a first switch and a second switch of the multi-chassis LAG environment; compare state parameters corresponding to the first switch and the second switch, wherein the state parameters are indicative of control plane and forwarding plane states of the first switch and the second switch; and

determine an active switch from amongst the first switch and the second switch based on the comparison of the state parameters.

15. The non-transitory computer-readable medium as claimed in claim 14, wherein the instructions, when executed, further cause the processor to communicate the determination of the active switch to the first switch and the second switch.