Field of Invention
The present invention relates to a method and device in a communications network for responding to a Fibre Channel over Ethernet solicitation. The method and device of the present invention generally relates to the field of world wide Storage networking.
Background of the Invention
Storage area networks (SANs) provide an increasingly important mechanism for making shared storage available to multiple hosts A SAN typically includes a number of storage devices, a plurality of hosts, and a number of switches arranged in a switching fabric that connects the storage devices and hosts. Most SANs rely on Fibre Channel protocol for communication within the fabric.
To this effect, Fibre Channel over Ethernet (FCoE) is a proposed mapping of Fibre Channel frames over selected full duplex IEEE 802.3 networks. This allows Fibre Channel to leverage 10 Gigabit Ethernet networks while preserving the Fibre Channel protocol. By retaining the native fibre channel constructs, FCoE allows a seamless integration with existing Fibre Channel networks and management software.
The primary application for FCoE is in the data centers used by enterprises requiring high availability and network storage. With FCoE, network (IP) and storage (SAN) data traffic can essentially be consolidated with a single switch. In today's data centers which use Ethernet for TCP/IP networks and Fibre Channel for storage area networks (SANs), with FCoE, Fibre Channel becomes another network protocol running on Ethernet, alongside traditional Internet Protocol (IP) traffic. This means FCoE runs alongside IP on Ethernet, unlike discs which runs

on top of IP using TCP. However, since classical Ethernet is loss, unlike Fibre Channel, to create a loss-less Ethernet required modifications to Ethernet which are being driven through the standards.
In a Fibre Channel network, a node port is directly attached to the Fibre Channel switch. So, the Fabric Login FC Frame (FLOGI) from the node port goes only to the switch.
07-303v0 FCoE specification (Cisco et. al) section 1.4.2 mentions that FLOGI is sent to a multicast address in which all the FCoE switches listen. The standard recommends the physical topology in which Enodes are directly connected to the FCF. In that case, only switch/FCF will receive the FLOGI. However, if an ENode is connected to the FCoE switch via an Ethernet LAN, then multiple FCoE switches on the LAN will receive the FLOGI frame. In that case, the standard mentions in passing that FCFs may co-ordinate amongst each other as to which FCF will reply.
07-343-vl FCoCEE Tutorial (Brocade) section 1.1 point 3 is consistent with the above. It hints that the FCF selection for a particular EPort could be policy driven or could be using some inter-switch Co-ordination mechanism.
07-572vl FCoE Discovery (Brocade, Cisco et. al) is the result of joint work and agreement among several member companies on a method for discovery of multiple FCFs (FCoE routers) in an Ethernet from a single FCoE NIC (07-665v0 FC-BB-5 meeting minutes). This document has been voted to be the basis for FCF discovery in FC-BB-5. 07-572vl differs from 07-303v0 and 07-343-vl in that it makes the discovery a two step process. The first step involves the Enode sending a multicast solicitation request. The second step involves sending the FLOGI only to a vendor specific subset of FCFs which have replied to the solicitation request.

Further it is indicated that the FCF can reply to the multicast solicitation with a jumbo unicast advertisement.
However, the agreed upon standard 07-5 72vl is silent about the inter-switch co¬ordination mechanism. A solicitation request is multicast by an end node to all end nodes. There is no disclosure in the protocol about the method to elect the most feasible FCOE forwarder (FCF) to respond to a multicast solicitation request in a Data Centre Ethernet. The choice of the right FCF to respond to a solicitation request affects the traffic traversing between the FCFs in the network. Hence an efficient method to ensure selection of the most optimal FCF to respond to a request in a network is of utmost importance and advantage.
This obviates a need for a method and device to elect the most feasible FCF to respond to a multicast solicitation request in a Data Center Ethernet LAN. The node should be elected such that it facilitates prevention of unnecessary traffic traversing through the network. Further, the cost associated with the paths nodes chosen to respond to the request should also be taken into account before election.
Objects and Summary of the Invention
The present invention has the objective to provide a method and device to determine the FCF to respond to a Fibre Channel over Ethernet solicitation.
It is also an objective of the instant invention to provide a method and system to determine the FCF to respond to a Fibre Channel over Ethernet solicitation using zoning configuration and Fabric Shortest Path First (FSPF) table.

It is still another objective of the instant invention to provide a method and system to determine the FCF to respond to a Fibre Channel over Ethernet solicitation using zoning configuration and weighed path costs.
To achieve the aforesaid and other objectives related to efficient networking, the instant invention provides a method to elect a node to respond to a multicast solicitation request from a source device in a communication network comprising the steps of:
- determining the zone of the source device;
- finding one or more nodes in the zone using zoning configuration;
- determining a total path parameter value for each node using predefined routing information; and
- electing the node with the least total path parameter value.
The instant invention further provides a device for electing a node to respond to a multicast solicitation request from a source in a communications network comprising:
- means for processing a solicitation request;
- means for storing zoning configuration and routing information coupled to means for processing the solicitation request; and
- means for electing a node with least total path parameter value for responding to the request using zoning configuration and routing information.
The instant invention further discloses a network comprising:
- a source for sending service requests; and
- a switch comprising:
■ means for storing zoning configuration and routing information;

■ means for determining total path parameter value for each node in the network; and
■ means for electing a node with least total path parameter value for responding to the request using zoning configuration and routing information.
The instant invention also provides a computer program product for determining the FCF to respond to a Fibre Channel over Ethernet solicitation, comprising one or more computer readable media configured to perform the method as disclosed herein below.
Brief Description of Drawings
The detailed description is described 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.
FIG. 1 illustrates exemplary network architecture for facilitating determination of the FCF to respond to respond to a Fibre Channel over Ethemet solicitation as disclosed by the present invention.
FIG. 2 illustrates the major phases of implementation of an exemplary method for determining the FCF to respond to a Fibre Channel over Ethemet solicitation as disclosed by the present invention.
FIG. 3 illustrates the election and confirmation phases of an exemplary method for determining the FCF to respond to respond to a Fibre Channel over Ethemet solicitation as disclosed by the present invention.

Detailed Description of Drawings
Method, device and network for determining the FCF to respond to a Fibre Channel over Ethernet solicitation are described. The device and method are not intended to be restricted to any particular form or arrangement, or any specific embodiment, or any specific use, disclosed herein, since the same may be modified in various particulars or relations without departing from the spirit or scope of the claimed invention herein above shown and described of which the device or method shown is intended only for illustration and disclosure of an operative embodiment and not to show all of the various forms or modifications in which this invention might be embodied or operated.
In a communication network such as a Data Center Ethernet LAN, an end node in FCOE (ENode) can send a multicast solicitation request as part of the FCOE Discovery protocol to identify the FCOE forwarder (FCF) to whom it can send the Fabric Login FC frame (FLOGI) solicitation. The method and device disclosed provide ways for electing the FCF which will respond to the solicitation, when there is more than one FCF in the LAN. The FCF election can be primarily based on zoning configuration of the network. The FCF which is the closest to the various members in the zone to which the Enode belongs to, can be elected. In order to determine the nearest FCF, i.e., the FCF having the shortest path, fibre channel fabric shortest path (FSPF) tables can be used. In another implementation, the likelihood of traffic to various targets could be configured. In such a case, the FSPF table can include weighed path cost indicating the potential traffic to each FCF in the network. The total weighed cost of all paths from a FCF to all other FCFs is determined. The FCF with the least total weighed path cost is elected to respond to the solicitation request. The disclosed method ensures that traffic from the ENode takes the shortest path. If all the nodes implement the disclosed method

of the present invention, unnecessary traffic traversing through the network creating congestion can be avoided to a great extent.
The elected FCF can send a multicast confirmation to all other FCFs in respect of its election for the specific request. In case of delay in receiving the confirmation from the elected FCF, a re-election can be held. Subsequently, the previously selected FCF can notify the other FCFs of cancellation of the election. Further historical information in respect of the FCF servicing each solicitation request from a particular host can be stored. This information can be used to expedite election by electing the previously selected FCF to service a particular host's request in case no topological changes have occurred. In case of any change in the network topology, the path costs are re-determined and stored by the FSPF tables. Accordingly the historical and other related information is updated to ensure that the traffic keeps flowing through an optimal path.
The techniques described herein may be used in many different operating environments and systems. An exemplary environment that is suitable for practicing various implementations is discussed in the following section with respect to the accompanying figures.
Exemplary Device and Network
Figure 1 illustrates an exemplary device to facilitate determination of the FCF to respond to a Fibre Channel over Ethernet solicitation as disclosed by the present invention using zoning configuration and FSPF table.
In an implementation, exemplary system 100 can include one or more processors 102, coupled to a zoning engine 104, storage area 106 and clocking means 110 over a communications network 108. Processor 102 can be a single processing
7

entity or a plurality of entities comprising multiple computing units. Zoning engine 104 can facilitate network management by enforcing one or more predetermined zoning rules within the network. Storage area 106 can include, for example, storage registers, secondary memory devices and other memory units for storing input and processed information. In an implementation, storage area 106 can include a plurality of information including topological information, zoning configuration information, routing information and other operational instructions.
An end node in a communication network 108 sends a multicast solicitation request for service to all nodes. On receipt of the solicitation request, processor 102 can process the request frame and extract the MAC address of the source node fi"om the solicitation request message fi-ame. Processor 102 can fiirther look up relevant topological information and zoning configuration stored in storage area 106 to determine the WWN and thus, the zone of the source node using mapping configuration information.
Once the zone of the source end node is determined, the associated costs for all nodes in the same zone can be accessed fi"om the FSPF table stored in the storage area 108. The associated costs in the FSPF table can be a weighed cost based on the potential traffic to a target device in the network 108. Processor 102 can fiirther determine total weighed cost for all paths running from each FCF to the other nodes in the zone. The FCF with the least total weighed cost can be elected to respond to the solicitation request.
Subsequent to election, elected FCF can send a multicast confirmation to the source end node and other FCFs within a predefined time period. Clocking means 110 can be used to determine the delay before a confirmation multicast is received by each FCF. In case, the confirmation is not received within the predefined time period, system 100 can initiate a re-election process as disclosed herein below in

the description of figures 2-4. Further, the election information can be stored in storage area 106 for future use to facilitate faster servicing of requests and preventing unnecessary network traffic. In case, there is a change in network configuration, zoning engine 104 can reconfigure the relevant information for one or more switches to ensure network flows through optimal channels. In such a case, relevant information can be updated in the storage area 106 to reflect the change of values on account of change in network configuration.
Fig. 2 illustrates exemplary network architecture 100 for facilitating determination of the FCF to respond to a Fibre Channel over Ethernet solicitation as disclosed by the present invention using zoning configuration and FSPF table. The FSPF table provides information regarding paths from a switch to all the other switches in the fabric. It further associates a cost with each link.
Hosts HI and H2 are FCoE hosts having FCoE HBAs on them. SI and S2 are FCoE gateway switches (FCFs). Targets Tl, T2, T3 and T4 are FC targets, and are coupled to the switches as illustrated in the figure. For discussion purposes, we assume that the zone configuration comprises of two zones: Zonel:Hl,Tl,T3 Zone 2: H2, T2, T4
When HI sends the muhicast solicitation request, FCFs SI and S2 can look up the zoning configuration. On determining that SI is closer to the various zone members in Zone 1 to which HI belongs, it is elected to respond to the solicitation request. Subsequently, HI sends the FLOGI only to SI.
When H2 sends the multicast solicitation request, FCFs SI and S2 can look up the zoning configuration and determine that S2 is closer to the various zone members

in Zone 2 to which H2 belongs. Hence S2 gets elected to respond to the solicitation request. As a result, H2 sends the FLOGI only to S2.
In a larger topology where the various targets need not be directly connected to the FCFs, the associated FSPF path cost to reach each zone member is used. The FCF with the least total path cost gets elected.
The administrator can configure a weight to each of the path cost based on the likelihood of traffic to the various targets. For example, 80% of the traffic from HI could be to T3 while only 20% of the traffic from HI could be to Tl. In such a scenario, the FCFs can use a weighted path cost to select the FCF which will respond to the solicitation. If case of a tie, the FCF with the lowest WWN wins the election.
In an implementation, the solicitation request can contain the MAC address of the host. The FCFs use configuration information such as a map to find out the WWN of the host, using the MAC address. Using the WWN, the switch can determine to which zone the host belongs to.
Subsequently, the elected FCF can send a multicast message to all the FCFs confirming the host for which it has been elected. The FCFs which have lost the election can wait for a predetermined amount of time for this message to be received. If the message is not received, they can elect a new FCF assuming the earlier selected FCF to be down or temporarily not available. In case of a race condition, when the first elected FCF is a bit slow in responding, a new FCF gets elected. The old FCF thus, loses the election and sends a forced LOGO to the host and announces to the FCFs that its previous win is cancelled. This announcement can happen by sending another multicast message to all FCFs.

Further, the FCFs can keep historical information of which initiators the various FCFs serviced. In case where the FSPF costs have not changed or when there is no change to zone configuration or when none of the targets have moved, the FCFs can just use the historical information to elect the FSPF, instead of re-determining the path cost.
Exemplary Method
Exemplary methods for determining the FCF to respond to respond to a Fibre Charmel over Ethernet solicitation are described with reference to Figs. 3 and 4. Processes 300 and 400 are illustrated as a collection of blocks in a logical flow graph, which represents a sequence of operations that can be implemented in hardware, software, or a combination thereof In the context of software, the blocks represent computer instructions that, when executed by one or more processors, perform the recited operations. The order in which the process is described is not intended to be construed as a limitation, and any number of the described blocks can be combined in any order to implement the process, or an ahemate process. Additionally, individual blocks may be deleted from the process without departing fi^om the spirit and scope of the subject matter described herein. For discussion purposes, the process 300 and 400 are described with reference to the implementations of Figures 1 and 2.
Fig. 3 illustrates an exemplary method 300 for determining the FCF to respond to respond to a Fibre Charmel over Ethernet solicitation as disclosed by the present invention. The major phases for election of an FCF include sending of multicast solicitation request, election of the FCF based on zoning configuration and FSPF tables and sending confirmation to the other FCFs. The following steps can be performed for implementing said exemplary method 300.

At block 302, an Enode in a data center Ethernet LAN, sends a multicast solicitation request to all the FCFs in the LAN as a part of the FCOE Discovery protocol. The solicitation request contains the MAC address of the host. Further, configuration information is used to determine the WWN of the Host using the MAC address received with the solicitation request.
At block 304, using the WWN, the switch can determine to which zone the host belongs to. The FCF election will be primarily based on zoning configuration. Once the zone is determined, an FCF is identified to whom the Fabric Login FC Frame (FLOGI) can be sent by the ENode. The FCF which is the closest to the various members in the zone to which the Enode belongs to, will be elected based on information in the FSPF tables. The FSPF tables provide information regarding the state of the links on all switches in the Fabric and hence can be used to determine the shortest path. Additionally, the likelihood of traffic to various targets could be configured; in which case, the FCFs can use a weighted path cost to select the FCF which will respond to the solicitation.
At block 306, the elected FCF sends a multicast message to all the FCFs confirming the host for which it has been elected. If the message is not received, they will elect a new FCF. The old FCF may then send a forced LOGO to the host and a multicast announcement to all the FCFs that its previous win is cancelled. Thus, the specific FCF to respond to the solicitation request is determined.
At block 308, the historical information in respect of which initiators were serviced by which FCFs can be stored for future use. Each time a solicitation request is received this historical information can be looked up along with information regarding any changes in the zoning configuration. In case the configuration information is unchanged, the previously elected FCF can be directly elected to respond to the request. This would speed up the communication

between the different nodes in the network and prevent unnecessary traffic flowing through the network.
At block 310, in case there is a change in the configuration of the network, the total path costs through each FCF in one or more zones in the network are recomputed. This information is used to update the FSPF tables, historical information stored in the FCFs and other relevant sources such that the on receipt of a solicitation request, the FCF with the most optimum cost is chosen to respond to the request.
Fig. 4 illustrates the election and confirmation phases of an exemplary method for determining the FCF to respond to respond to a Fibre Channel over Ethernet solicitation request.
At block 402, on receipt of a multicast solicitation request, the WWN of the Host is determined by using the MAC address present in the solicitation request. The WWN can be used to determine the zone to which the Host belongs. The Switching Fabric allows communications only between devices belonging to the same zone, preventing a device of one zone from seeing, or accessing a device of another zone. Hence, the switch can look up the zoning configuration information to determine the FCFs present within the same zone that can service the Host request.
At block 404, the FSPF tables are looked up to track of the state of the links on all switches in the Fabric. In a larger topology, the various targets need not be directly connected to the FCFs. In that case, the FCF uses the FSPF path cost that it takes for it to reach each zone member. Each link has an associated cost in the FSPF table.

At block 406, the total costs associated with all paths running from each FCF to the other nodes in the zone are determined. The total cost is determined by computing paths from a switch to all the other switches in the fabric, by adding the cost of all the links traversed by the path.
At block 408, the FCF with the shortest path gets elected. In most network topologies, the various targets need not be directly connected to the FCFs. In that case, the FCF uses the FSPF path cost that it takes for it to reach each zone member. The administrator could configure a weight to each of the path costs based on the likelihood of traffic to the various targets. In that case, the FCFs use a total weighted path cost to select the FCF which will respond to the solicitation. In case of a tie, the FCF with the lowest WWN wins the election.
At block 410, the elected FCF sends a multicast message to all the FCFs confirming the host for which it has been elected. The FCFs which have lost the election will wait for a predetermined amount of time for this message to be received.
At block 412, if the message is not received, they will elect a new FCF since the earlier selected FCF may be either down or is temporarily unavailable.
At block 414, in case of a race condition, re-election can occur. In case the first elected FCF is a bit slow in responding due to which a new FCF has got elected, the old FCF loses the election by sending a forced LOGO to the host and announcing to the FCFs that its previous win is cancelled. This announcement can happen by sending another multicast message to all FCFs.
The embodiments described above and illustrated in the figures are presented by way of example only and are not intended as a limitation upon the concepts and

principles of the present invention. As such, it will be appreciated by one having ordinary skill in the art that various changes in the elements and their configuration and arrangement are possible without departing from the spirit and scope of the present invention as set forth in the appended claims.
It will readily be appreciated by those skilled in the art that the present invention is not limited to the specific embodiments shown herein. Thus variations may be made within the scope and spirit of the accompanying claims without sacrificing the principal advantages of the invention.
We claim:
1. In a communications network, a method to elect a node to respond to a
multicast solicitation request from a source device comprising the steps of:
- determining the zone of the source device;
- finding one or more nodes in the zone using zoning configuration;
- determining a total path parameter value for each node using predefined routing information; and
- electing the node with the least total path parameter value.

2. The method as claimed in claim 1, wherein the step of determining the zone of the source device comprises the steps of determining the WWN of the source using MAC address and predefined configuration information.
3. The method as claimed in claim 1, wherein the communication network is a Data Centre Ethernet LAN.
4. The method as claimed in claim 1, wherein the routing information is stored in a FSPF table.

Principles of the present invention. As such it will be appreciated by one having ordinary skill in the art that various changes in the elements and their configuration and arrangement are possible without departing from the spirit and scope of the present invention as set forth in the appended claims
It will readily be appreciated by those skilled in the art that the present invention is not limited to the specific embodiments shown herein. Thus variations may be made within the scope and spirit of the accompanying claims without sacrificing the principal advantages of the invention.
We claim:
1. In a communications network, a method to elect a node to respond to a
multicast solicitation request from a source device comprising the steps of:
- determining the zone of the source device;
- finding one or more nodes in the zone using zoning configuration;
- determining a total path parameter value for each node using predefined routing information; and
- electing the node with the least total path parameter value.

2. The method as claimed in claim 1, wherein the step of determining the zone of the source device comprises the steps of determining the WWN of the source using MAC address and predefined configuration information.
3. The method as claimed in claim 1, wherein the communication network is a Data Centre Ethernet LAN.
4. The method as claimed in claim 1, wherein the routing information is stored in a FSPF table.

5. The method as claimed in claim 1, wherein the path parameter value includes distance from a predefined node, associated cost and weighed cost based on potential traffic to a node.
6. The method as claimed in claim 1, wherein the step of electing comprises the steps of:

- sending election confirmation multicast by elected node to source and other nodes;
- re-election of node in case of delay; and
- storing election information for the source for fixture use.

7. The method as claimed in claim 1, wherein the step of re-election comprises the step of sending a multicast notification of canceling the election by previously elected node to source and the other nodes.
8. A device for electing a node to respond to a multicast solicitation request from a source in a communications network comprising:

- means for processing a solicitation request;
- means for storing zoning configuration and routing information coupled to means for processing the solicitation request; and
- means for electing a node with least total path parameter value for responding to the request using zoning configuration and routing information.
9. The device as claimed in claim 8, wherein the means for processing
includes:
means to extract MAC address of the source device;
- means to determine WWN of the source device; and
- means for determining the zone of the host using the WWN.

10. The device as claimed in claim 8, wherein the means for electing
comprises:
- means to determine the total path parameter value for each node;
- clocking means to determine delay; and
- means for sending confirmation or cancellation of election notification
to one or more nodes in the network.
11. A network comprising:
- a source for sending service requests;
- a switch comprising:
■ means for storing zoning configuration and routing information;
■ means for determining total path parameter value for each node in
the network; and
■ means for electing a node with least total path parameter value for
responding to the request using zoning configuration and routing
information.
12. The network as claimed in claim 12, wherein the network is a Data Centre
Ethernet LAN.
13.A computer program product to elect a node to respond to a multicast solicitation request from a source device in a communications network, comprising one or more computer readable media configured to perform the method as claimed in any of the claims 1-7.