FR2878675A1 - METHOD FOR INTERCONNECTING TWO SUB-NETWORKS - Google Patents

Abstract

This method of interconnecting two sub-networks (A, B) to form a network (R), each sub-network (A) comprising one or more switches (xA) configured with a first value common to all the switches (xA) of said subnetwork (A) and representative of the maximum lifetime of a message within said subnetwork (A), comprises: - a step of determining, a so-called reconfiguration value, this value being an admissible value for the maximum lifetime of a message within said network (R); - a step of broadcasting said reconfiguration value to all the switches (xA, xB) of the network (R); and a step of reconfiguring each of the switches (xA, xB) with the reconfiguration value.

Description

2878675 1

  BACKGROUND OF THE INVENTION The present invention is in the field of the interconnection of two telecommunication subnetworks.

  In known manner, the interconnection of two subnets often requires a preliminary step of reconfiguration of certain subnet parameters which must be made compatible between them before the merger.

  The invention finds particular application in the interconnection of networks in accordance with the Fiber Channel standard FC-SW-2 defined by the ANSI / T11 organization. In the remainder of this document, this standard will simply be called Fiber Channel.

  Figures 1 to 3 which will now be described illustrate the disadvantages of the Fiber Channel standard for the interconnection of two subnets.

  FIG. 1 shows two Fiber Channel subnetworks (or islands) A and B. In the remainder of this document, note xA, respectively xB, the switches of the network A, respectively B. In the example of this FIG. the sub-networks A and B therefore each comprise three switches 1A to 3A, respectively 1B to 3B.

  Within each subnetwork, the switches are interconnected by Inter Switch Link (ISL) links defined by this standard.

  In a manner known to those skilled in the art, each switch xA, xB islands A and B has a memory M to store two counters R_A_TOV (Resource Allocation Time Out Value) and E_D_TOV (Error Detect Time Out Value), these counters representing different maximum lifetimes of a Fiber Channel frame within its island.

  In the remainder of this document, we will limit ourselves to the particular case of the life counter R_A_TOV ,, but the description is transposed in the same way for the other counter E_D_TOV.

  In the example of FIG. 1, these counters, named respectively R_A_TOV_A and R_A_TOV_B for the islands A and B, are different, respectively equal to 10 and to 15.

  With the new Storage Area Network (SAN) extension protocols such as Fiber Channel over IP (FCIP-RFC 3821-ftp: //ftp.rfceditor.org/in-notes/rfc3821.txt) defined by the organization IETF standardization, it is possible to widely interconnect two islands as briefly described above through an IP network.

  To establish this interconnection, a tunnel T is established between two switches 1A, 1B of islands A and B, these switches being configured as gateways PA, PB according to the architecture shown in FIG.

  When this interconnection is carried out, the two islands A, B merge and form a single network R. However, the tunnel T having the same characteristics as an ISL link, the aforementioned Fiber Channel standard requires that all switches xA , xB of network R share the same maximum lifetime counter RA TOV.

  In the example represented in FIG. 2, this condition is not fulfilled since the switches xA previously belonging to the island A had a counter R_A_TOV_A equal to 10, whereas those (xB) of the island B had a counter R_A_TOV_B equal to 15.

  Figure 3 shows the exchange of messages in the network R as defined by the conventional Fiber Channel protocol.

  When interconnecting the PA and PB gateways T, one of them, for example the PA gateway, sends to the other gateway, in this case the PB gateway, a message SW_ILS ELP (Switch Inter Link Services Exchange Link Parameter), this message comprising, in particular, the value 10 of the counter R_A_TOV_A of its island A. On receipt of this message SW_ILS ELP, the gateway PB, realizing that the value of the counter R _A TOV_A in the island A is different from the value of the counter R_A_TOV_B in the island B, rejects the interconnection, by sending a SW_ILS RJT message (Switch Inter Link Services Reject) accompanied by error code R_A TOV_MISMATCH.

  2878675 3 As a result, the automatic interconnection of two configured SANs with R_A_TOV counters of different lifetimes is not possible in the current state of the standard.

  The present invention aims to solve this disadvantage.

  For this purpose, the invention relates to a method for interconnecting two sub-networks to form a network, each sub-network comprising one or more switches configured with a first value common to all the switches of the sub-network and representative of the duration maximum life of a message within the subnet.

  This method comprises: a determination step, a so-called reconfiguration value, this value being a permissible value for the maximum lifetime of a message within the network; a step of broadcasting the reconfiguration value to all the switches of the network; and a step of reconfiguring each of the switches with the reconfiguration value.

  Thus, the interconnection method according to the invention makes it possible to automatically reconfigure all the switches of the network R, with a reconfiguration value shared by all of these switches.

  Preferably, when the network consists of two Fiber Channel standard islands interconnected by two edge switches connected to each other by a network link and in which the first value is a lifetime counter defined by the standard, the method comprises a step during which a first border switches sends, to the second, a message with the counter of its island.

  This message may notably consist of a SW_ILS type message (Switch Inter Link Service) defined by the FibreChannel standard.

  When the switches act as a gateway, this message can also be constituted by any FCIP frame, and in particular by a FCIP frame FSF (FCIP Special Frame) exchanged during the interconnection of these gateways.

  2878675 4 The reconfiguration value is then determined by the second edge switch from the counter of its island and at least one information contained in the message.

  The diffusion step is then initiated by the second edge switch by sending a reconfiguration message followed by a parameterization message for all the switches of the network, the parameterization message comprising the aforementioned reconfiguration value.

  Thus, returning to FIG. 2 previously described, on receiving the SW_ILS ELP message, the edge switch 1B determines a permissible reconfiguration value and broadcasts it to all the switches of the network. To do this, it sends a SW_ILS RCF (Switch Inter Lirik Services Reconfigure Fabric) message on all its Extended Port E_Port ports to which the switches are attached. As described later, this modification propagates in cascade within the network R. Preferably, when the edge switches are simple switches, the value of reconfiguration chosen is the largest of the first values, namely in this example the value 15.

  According to a preferred embodiment, when the edge switches are constituted by gateways interconnected by an IP type tunnel, this message is constituted by an FCIP frame.

  The reconfiguration value is chosen as being equal to: the duration of crossing of this tunnel by the message, if this duration is greater than the first two values; and - at the largest of the first values, if it is greater than this duration, this duration is obtained from a field of this FCIP frame. More precisely, it is calculated by the gateway receiving the frame from the information contained in the TIME STAMP field of the FCIP header of the IP packet and the instant of reception of this message.

  For more information on the structure of the FCIP header, one skilled in the art can refer to RFC 3643 available at ftp://ftp.rfc-editor.org/in-notes/rfc3643.txt.

  Correlatively, the invention relates to a switch that can be connected to a sub-network of a network, and comprising: storage means for storing a first value representative of the maximum lifetime of a message at a time; within this subnet; and - means for receiving a message; means for determining, from the first value and at least one information contained in the message, a so-called reconfiguration value, this value being an admissible value for the maximum lifetime of a message within the network; and - means for broadcasting the reconfiguration value to all the switches of the network; and - reconfiguration means able to substitute, in the storage means, said first value by the reconfiguration value.

  The invention also relates to a computer program that can be executed by a switch that can be connected to a sub-network of a network, this program comprising instructions for implementing: a step of receiving a message; ; a determination step, based on a first value representative of the maximum lifetime of a message within the sub-network, and on at least one information contained in the message, of a value called reconfiguration, this value being a permissible value for the maximum lifetime of a message within the network; and - a step of broadcasting the reconfiguration value to all the switches of the network; and a step of reconfiguration, substituting, in storage means of the switch implementing this program, the first value by the reconfiguration value.

  The invention also relates to a readable information medium by a switch, possibly totally or partially removable, in particular a CD-ROM or magnetic medium, such as a hard disk or a diskette, or a transmissible medium, such as an electrical or optical signal, this medium with instructions from a computer program as briefly mentioned above, when this program is loaded and executed by this switch.

  The particular advantages of the switch, the computer program and the information medium being identical to those of the interconnection method mentioned above, they will not be recalled here.

Brief description of the drawings

  Other aspects and advantages of the present invention will emerge more clearly on reading the description of particular embodiments which will follow, this description being given solely by way of nonlimiting example and with reference to the appended drawings in which: FIG. 1, already described, represents two sub-networks that can be interconnected according to an interconnection method according to the invention; FIG. 2, already described, represents a network constituted by the merger of the two subarrays of FIG. 1, at the moment of the merger; FIG. 3, already described, represents the rejection of the interconnection of the two sub-networks in accordance with the prior art; Figure 4 shows the main steps of a computer program according to the invention in a preferred embodiment; FIGS. 5A to 53 show, schematically, an interconnection method according to the invention in a first embodiment; and FIGS. 6A to 6G show an interconnection method 25 according to the invention in a second preferred embodiment.

  Detailed description of two embodiments

  We will now describe with reference to Figures 4 and 5A to 53 an interconnection method according to the invention in a first embodiment.

  In this embodiment, the switches 1A and 1B of the sub-networks A and B are interconnected by means of an identical ISL link to the ISL links interconnecting the switches xA, respectively xB, within the sub-network A, respectively B. As described previously with reference to FIG. 3, at the time of interconnection of these subnets, one of the two edge switches, for example the switch 1A, sends a message SW_ILS ELP to the other switch of the switch. border (namely the switch 1B), this message comprising the value of the counter Ft A TOV A shared by all the switches xA of the subnet A. This message is received during a step E10 of receiving a program of computer according to the invention, loaded and executed by the switch 1B.

  According to the invention, this reception step E10 is followed by a step E20 during which the switch 1B determines, if necessary, a reconfiguration value R_A TOV, which is admissible for the maximum lifetime of a message within the network R result of the merger of the two subnets A and B. In this first embodiment, the RA TOV reconfiguration value is chosen as the largest of the first 15 values R_A_TOV_A, R_A_TOV_B is 15.

  This determination step E20 is followed by an E25 test, the result of which is positive if the switches of the network have to be reconfigured, and negative if the opposite is true, that is to say, when the first values R_A_TOV_A, R A_TOV_B are equal. .

  When the result of this test E25 is negative, it is followed by the step E10 of waiting and receiving a message already described.

  Otherwise, this test E25 is followed by an optional step in which the switch 1B rejects the interconnection of the two subnets, by sending the other border switch, the SW_ILS RJT message already described.

  After sending the rejection message SW_ILS RJT (or at the output of the positive test E25 if the optional rejection step is not implemented), the edge switch 1B sends, during a step E30, a SW_ILS RCF reconfiguration message on all its E_Port extension ports, in particular to the other edge switch 1A.

  This reconfiguration message is received by the interconnected switches 1A and 2B to the E_Port extension ports of the edge switch 1B.

  For the sake of simplicity, the SW_ILS RCF reconfiguration message is simply noted as RCF in the figures.

  Referring now to FIG. 5B and in accordance with the protocol defined by the Fiber Channel standard, the switches 1A and 2B having received the SW_ILS RCF reconfiguration message, respond to this message by sending an acknowledgment SW_ILS ACC to the edge switch. 1B.

  This acknowledgment is received by the switch 1B during a step E40 of acknowledgment waiting.

  For simplicity also, the acknowledgment message SW_ILS ACC is noted ACC in the figures.

  In accordance with the Fiber Channel protocol, switches 1A and 2B cascade the SW_ILS RCF reconfiguration message to all their E_Port extension ports.

  Thus, the switch 1A transmits the reconfiguration message SW_ILS RCF to the switch 2A; and - the switch 2B transmits this message to the switch 3B.

  With reference to FIG. 5C, the switches 2A and 3B, upon reception of the reconfiguration message, send an acknowledgment message SW_ILS ACC respectively to the switch 1A and the switch 2B.

  On the other hand, the switch 2A propagates the reconfiguration message SW_ILS RCF to the switch 3A connected to its extension port E_Port.

  After the acknowledgment standby step E40, according to the invention, the switch 1B sends, during a step E50, to each of its extension ports IE_Port having received an acknowledgment message SW_ILS ACC in response to the reconfiguration message, a configuration message SW_IILS ELP comprising the reconfiguration value R_A_TOV determined during step E20, namely the value 15.

  With reference to FIG. 5D, the switches 1A and 2B receiving this parameterization message are reconfigured by substituting in their memory M the value of their counter by the reconfiguration value received in the parameterization message.

  Thus, with reference to FIG. 5D, the switch 1A has, after this step, a new lifetime counter equal to 15.

  In accordance with the Fiber Channel protocol, the switches 1A and 2B acknowledge, by sending an acknowledgment message SW_ILS ACC, the reception of the parameter message SW_ILS ELP.

  Similarly, the switch 3A acknowledges the reception of the message reconfiguration SW_ILS RCF by sending an acknowledgment message SW_ILS ACC to the switch 2A.

  Still referring to FIG. 5D, the switch 1A sends, on the extension ports E_Port having received an acknowledgment message SW_ILS ACC from the switch 2A, the reconfiguration message SW_ILS RCF.

  Referring to Figure 5E, switch 2A acknowledges receipt of this reconfiguration message by sending an acknowledgment message SW_ILS ACC to switch 1A.

  And switch 2A sends a SW_ILS RCF reconfiguration message to the E_Port extension port through which it has received the acknowledgment message from switch 3A.

  Referring now to FIG. 5F, the switch 3A sends an acknowledgment message SW_ILS ACC in response to the received reconfiguration message from the switch 2A.

  And the switch 1A sends, on the extension port E_Port by which it has received an acknowledgment message in response to the sending of its reconfiguration message SW_ILS F, CF, a setting message SW ILS ELP having the value RA TOV reconfiguration, namely the value 15, determined in step E20.

  With reference to FIG. 5G, the switch 2A, on receiving the parameter message SW_ILS ELP, modifies the value of its life counter in its merger M, and acknowledges the reception of this parameter message by the sending of an acknowledgment message SW_ILS ACC to switch 1A.

  On the other hand, the switch 2A sends a SW_ILS RCF reconfiguration message to the extension port E_Port by which it has received an acknowledgment message in response to the SW_ILS RCF reconfiguration message that it had sent to the switch 3A as previously described in FIG. reference to Figure 5E.

  Referring now to FIG. 5H, the switch 3A acknowledges receipt of this reconfiguration message by sending an acknowledgment message to the switch 2A.

  With reference to FIG. 5I, the switch sends, on its extension port E_Port by which it has received this acknowledgment message, a setting message SW_ILS ELP, this message comprising the value Ft A TOV 15 of reconfiguration.

  Referring finally to FIG. 53, the switch 3A, on receiving this message SW_ILS ELP reconfiguration, modifies, in its memory M, the value of the lifetime counter and acknowledges, by sending a message SW_ILS ACC, receiving the setting message.

  At the end of the reconfiguration of the switch 3A, all the switches of the network have the same value for the lifetime counter of the messages within this network.

  The interconnection method in this first embodiment is completed.

  We will now describe with reference to Figures 4, 6 and 6A to 6G, an interconnection method according to the invention in a second embodiment.

  The references shown in FIGS. 6A to 6G designate the same elements as those identical in FIGS. 5A to 53.

  In this second embodiment, the islands A and B are interconnected by means of gateways PA and PB synchronized and connected by a tunnel T through a network: [P.

  This tunnel T can in particular be a link of a local area network (LAN) or a public network (WAN).

  The tunnel T established between the two FCIP gateways PA and PB has the same characteristics as an ISL link. This implies that the crossing time of the IP network by a FCIP Fiber Channel frame encapsulated in an IP packet must be less than the lifetime value of the frame imposed by the lifetime counter R_A_TOV. Otherwise, all Fiber Channel frames would be discarded on arrival in the destination island.

  When interconnecting the PA and PB gateways, one of these, for example the PA gateway, sends a message in the form of an FCIP FSF (FCIP Special Frarne) frame, this frame being received. by the PB gateway located at the other end of the tunnel T. In accordance with the FCIP protocol, this FSF frame includes a field "rhyme stamp" containing the time of sending this frame by the gateway PA.

  On reception (step E10) of an FCIP frame, and in particular when receiving the FCIP frame FSF, the gateway 1B implements the determination step E20 according to the invention.

  In this second embodiment, the value R_A_TOV of reconfiguration is fixed, if necessary, during this determination step equal to: the duration DT of crossing of the IP link by the message if this duration is greater than the first two RATON / A values, RATON / 13; and at the largest of the first values R_A_TOV_A, R_A_TOV_B, if this is greater than the duration DT.

  If the first two values R_A_TOV_A, R_A TOV_B are equal to and less than the transit duration DT, the switches of the network do not need to be reconfigured.

  This duration DT is obtained by the PB gateway by making the difference between the time of reception of the FCIP frame and the value contained in the time stamp field TS_B of this frame.

  In the example described here, it will be assumed that this duration DT is equal to 30.

  At the end of this determination step E20, the PB gateway performs an E25 test whose result is positive if the switches of the network are to be reconfigured.

  When the result of the test E25 is positive, the PB gateway stores this reconfiguration value in its memory M, thus reconfiguring its life counter.

  Then, as shown in FIG. 6A, the PB gateway sends (step E30) SW_ILS RCF reconfiguration messages to all of its E_Port extension ports.

  Figures 6B to 6G are similar to Figures 5 previously described and will not be detailed here.

  In summary, each switch on the network performs the following operations: - transmission, step by step, of the TW_ISL RCF reconfiguration messages; - acknowledgment of the reconfiguration messages; sending (E40) a TW_ISL ELP parameter frame containing the value of R A_TOV DT on receipt of an acknowledgment message in response to the sending of a reconfiguration frame; reconfiguration of the lifetime counter on receipt of a parameter frame; and - acknowledgment of the parameterization messages.

  At the end of the interconnection method of this second embodiment (FIG. 6G), all the switches of the network memorize the same value DT of life counters.

  The description which has just been made with reference to FIGS. 4 and 6A to 6G presented the interconnection method according to the invention in the particular example of the reconfiguration of the R_A_TOV parameter of two Fiber Channel islands.

  Of course, the invention applies in the same way to the reconfiguration of other parameters of this standard prior to the interconnection of two subnets.

  In particular, the invention allows the reconfiguration of the parameter E_D TOV already mentioned.

  The invention can also be used to interconnect two subnets conforming to another standard than the Fiber Channel standard, since this standard makes it possible to propagate a reconfiguration parameter within the network.

Claims (1)

13 Claims   A method for interconnecting two subnetworks (A, B) to form a network (R), each subnet (A) having one or more switches () <A) configured with a first value (R_A_TOV_A) common to all the switches (xA) of said sub-network (A) and representative of the maximum lifetime of a message within said sub-network (A), this method being characterized in that it comprises: a determination step, a value (R_A_TOV) called reconfiguration value, this value being a permissible value for the maximum lifetime of a message within said network (R); a step of broadcasting said reconfiguration value (R A TOV) to all the switches (xA, xB) of said network (R); and a step of reconfiguring each of said switches (xA, xB) with said reconfiguration value (R_A_TOV).   An interconnection method according to claim 1, wherein said network is constituted by two Fiber Channel-compliant islands (A, B) interconnected by two edge switches (1A, 1B; PA, PB) interconnected by each other. a network link (ISL, IP) and wherein said first value is a lifetime counter (R_A_TOV_A, R_A_TOV_B) defined by said standard, said method comprising - a step in which, a first of said edge switches (1B , PB) sends, to the second (1A, PA) of said edge switches, a message (SW_ILS, FCIP) comprising said counter (R_A_TOV_B) of its island (B); said method being characterized in that: - said reconfiguration value (RA TOV) is determined by said second edge switch (1A, PA) from the counter (R_A_TOV_A) of its island (A) and at least one information (R_A_TOV_B, TS_B) contained in said message (SW_ILS, FCIP); and in that - said diffusion step is initiated by said second edge switch (1A, PA), by sending a reconfiguration message (SW_ILS) followed by a setting rnessage (SW_ILS) 2878675 14 intended for all said switches of the network, said parameterization message comprising said reconfiguration value (R_A_TOV).   3. Interconnection method according to claim 2, wherein said link is an ISI type link. defined by said standard, characterized in that said reconfiguration value (R_A TOV), chosen by said second edge switch (1A) is the largest of said first values (R_A_TOV_A, R_A_TOV_B).   4. Interconnection method according to claim 2, wherein said edge switches are gateways (PA, PB) synchronized with each other and connected by a tunnel (T) of IP type, characterized in that said reconfiguration value (R_A TOV), chosen by said second edge switch (PA) is equal to: the duration (DT) of crossing of said tunnel (T) by said message (FCIP), if this duration is greater than said first values (R_A_TOV_A, R_A_TOV_B) ; and - at the highest of the first values (RA TOV A, R_A_TOV_B), if this is greater than said duration (DT), - said duration (DT) being obtained from a field of this message (FCIP) .   5. Switch (xA) capable of being connected to a subnet (A) of a network (R), and comprising: - means (M) for storing a first value (R_A TOV_A) representative of the duration maximum life of a message within said subnet (A); and means (E_Port) for receiving a message (SW_ILS, FCIP); said switch (xA) being characterized in that it comprises: - determination means, from said first value (R_A_TOV_A) and at least one information (R_A_TOV_B, TS_B) contained in said message (SW_IILS, FCIP) , a value (R_A_TOV) said reconfiguration, this value being a permissible value for the maximum lifetime of a message within said network (R); and - means for broadcasting said reconfiguration value (R_A_TOV) to all the switches (xA, xB) of said network (R); and 2878675 15 - reconfiguration means able to substitute, in said storage means (M), said first value (R_A_TOV_A) by said value (R_A_TOV) of reconfiguration.   The switch according to claim 5, wherein said network (R) is in accordance with the Fiber Channel standard, said switch being connected to said subnet (A) by an ISL type link defined by said standard, said switch (xA) being characterized in that said determining means is adapted to set said reconfiguration value (R_A TOV) equal to the largest of the values selected from: said first value (R_A_TOV_A); and a second first value (R_A TOV_B), representative of the maximum lifetime of a message within another sub-network (B) of said network (R), and obtained from said message (SW_ILS).   The switch of claim 5, acting as a gateway (PA) in a Fiber Channel-compliant network (R), said gateway (PA) being synchronized and connected with a second gateway (PB) of said network (R) by a tunnel (T) of IP type, this gateway (PA) being characterized in that said determining means are adapted to fix said reconfiguration value (R_A TOV) equal to: - the duration (DT) of crossing of said tunnel (T ) by said message (FCIP), if this duration is greater than said first value (RA TOV A) and a second first value (R_A TOV_B), representative of the maximum lifetime of a message within another sub-network (B) of said network (R); and at the largest of the first values (R_A_TOV_A, R_A TOV_B), if this one is greater than said duration (DT), - said duration (DT) and said second first value (R_A_TOV_B) being obtained from said message ( FCIP).   8. Computer program, which can be executed by a switch (xA) that can be connected to a subnet (A) of a network (R), this program comprising instructions for implementing: 2878675 16 a step receiving a message (SW_ILS, FCIP); this program being characterized in that it further comprises instructions for implementing: a determination step, starting from a first value (R_A_TOV_A) representative of the maximum lifetime of a message within said subnetwork (A), and at least one information (R_A_TOV_B, TS_B) contained in said message (SW_ILS, FCIP), of a value (R_A TOV) called reconfiguration, this value being a permissible value for the maximum lifetime a message within said network (R); a step of broadcasting said reconfiguration value (R_A_TOV) to all the switches (xA, xB) of said network (R); and a step of reconfiguration, substituting, in storage means (M) of the switch (xA), said first value (R_A_TOV_A) by said reconfiguration value (R ATOV).   Computer program according to claim 8, wherein said network (R) is in accordance with the Fiber Channel standard, said switch being connected to said subnet (A) by an ISL type link defined by said standard, characterized in that that, during said determination step, said reconfiguration value (R_A_TOV) is fixed equal to: - the duration (DT) of crossing of said tunnel (T) by said message (FCIP), if this duration is greater than said first value (R_A_TOV_A) and a second first value (R_A_TOV_B), representative of the maximum lifetime of a message in another subnet (B) of said network (R); and at the largest of the first values (R_A_TOV_A, R_A_TOV_B), if it is greater than said duration (DT), - said duration (DT) and said second first value (R_A_TOV_B) being obtained from said message ( FCIP).   The computer program of claim 8 wherein said network (R) conforms to the Fiber Channel standard, said switch being a synchronized gateway (PA) and connected with a second gateway (PB) of said network (R) by a tunnel (T) of IP type, characterized in that, during said determining step, said reconfiguration value (R_A_TOV) equal to the duration (DT) of passing through said tunnel (T) by said message is fixed; (FCIP), this time being obtained from a field of this message (FCIP).   11. Information carrier readable by a switch (xA, xB), possibly totally or partially removable, in particular CD-ROM or magnetic medium, such as a hard disk or a diskette, or transmittable medium, such as an electrical or optical signal, characterized in that it comprises instructions of a computer program according to any one of claims 8 to 10, when this program is loaded and executed by this switch.