WO2006056719A1

WO2006056719A1 - Method of interconnecting two subnetworks

Info

Publication number: WO2006056719A1
Application number: PCT/FR2005/050981
Authority: WO
Inventors: Manuel Moreira; Nouredine Bouadma; Guy Martayan
Original assignee: France Telecom
Priority date: 2004-11-26
Filing date: 2005-11-23
Publication date: 2006-06-01
Also published as: FR2878675A1

Abstract

The invention relates to a method of interconnecting two subnetworks (A, B) in order to form a network (R), whereby each subnetwork (A) comprises one or more switches (xA) which are configured with a first value that is common to all of the switches (xA) of said subnetwork (A) and that is representative of the maximum lifetime of a message within the subnetwork (A). The inventive method comprises the following steps, namely: a step consisting in determining a value, known as a reconfiguration value, which is a value that is allowed for the maximum lifetime of a message within the network (R); a step consisting in diffusing said reconfiguration value to all of the switches (xA, xB) in the network (R); and a step consisting in reconfiguring each of the switches (xA, xB) with the reconfiguration value.

Description

Title of the invention

Method for interconnecting two subnetworks

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 parameters of the subnets that 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 represents two Fiber Channel A and B subnetworks (or islands). In the remainder of this document, we note xA, respectively xB, the switches of network A, respectively B.

In the example of this FIG. 1, the sub-networks A and B each therefore comprise three switches IA to 3A, respectively IB 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, it will be limited to the particular case of the lifetime counter R_A_TOV, but the description is transposed to the same 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.rfc-editor.org/in-notes/rfc3821.txt) defined by the IETF standardization organization, 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 IA, IB 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 R_A_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 tunnel T PA gateways and

PB, one of them, for example the PA gateway, sends to the other gateway, in this case the PB gateway, a SWJLS ELP (Switch Inter Link Services Exchange Link Parameter) message, this message including, inter alia, the value of the counter R_A_TOV_A of its island A. Upon receipt of this message SWJLS 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 15 R_A_TOV_B in the island B, rejects the interconnection, by sending a SWJLS RJT message (Switch Inter Link Services Reject) accompanied by the error code R_AJTOV_MISMATCH. As a result, the automatic interconnection of two SANs Islands configured with R_A_TOV counters of different lifetimes is impossible in the current state of the standard.

Object and summary of the invention

The present invention aims to solve this disadvantage. For this purpose, the invention relates to a method for interconnecting two subnetworks to form a network, each subnetwork comprising one or more switches configured with a first value common to all the switches of the subnetwork and representative of the maximum lifetime of a message within the subnet.

This process comprises;

a determination step of 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.

This method can in particular be implemented in a switch or in a gateway for interconnecting two subnetworks.

In practice, the method according to the invention is implemented in each of the switches of the two sub-networks, and the interconnection can be achieved by choosing any switch in each sub-network. For the sake of clarity, we will call thereafter, "edge switch", the switch chosen in each sub-network to achieve the interconnection. The interconnection method according to the invention thus makes it possible to automatically reconfigure all the switches of the network R, with a reconfiguration value shared by all of these switches.

The invention applies in particular to the interconnection of two sub-networks conforming to the Fiber Channel standard, called "islands" in this context. Preferentially, when the network consists of two Fiber Channel standard islands interconnected by two so-called "edge" switches connected to one another 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 so-called "edge" switches sends, to the second, a message with the counter of its island.

This message may in particular be constituted by a SWJLS type message (Switch Inter Link Service) defined by the FibreChannel standard.

When the switches act as 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. The reconfiguration value is then determined by the second so-called "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 so-called "edge" switch by sending a reconfiguration message followed by a parameterization message intended for all the switches of the network, the parameterizing message comprising the reconfiguration value. supra.

Thus, returning to FIG. 2 previously described, upon receipt of the SVVJLS ELP message, the so-called "edge" switch IB determines a permissible reconfiguration value and broadcasts it to all the switches in the network. To do this, it sends a SWJLS RCF (Switch Inter Link Services Reconfigure Fabric) message to all its Extended Port E_Port extension ports to which the switches are attached. As described later, this modification propagates in cascade within the network R, in other words, step by step.

Preferably, when the so-called "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 one particular embodiment, when the so-called "de border 'are constituted by footbridges interconnected by a tunnel. The reconfiguration value is chosen to be 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 highest of the first values, if this is greater than this duration,

In a particular embodiment, the tunnel is of IP type and the message is constituted by a FCIP frame. The crossing time of the tunnel is then 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 field ΗME STAMP 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, the skilled person can refer to the document RFC 3643 available at ftp: //ftp.rfc-editor.orq/in-notes/rfc3643,txt.

The invention also relates to a switch and a gateway capable of being connected to a sub-network of a network, and comprising:

means for storing a first value representative of the maximum lifetime of a message within this sub-network; and

means for receiving a message;

means for determining, from the first value and at least one piece of 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;

means for broadcasting the reconfiguration value to all the switches of the network; and

- Reconfiguration means adapted 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 or a gateway that can be connected to a subnetwork 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 reconfiguration, substituting, in storage means of the switch implementing this program, the first value by the reconfiguration value.

The invention also relates to an information carrier readable by a switch or by a gateway, 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 signal or optical, this medium including instructions of a computer program as mentioned briefly above, when this program is loaded and executed by this switch or by this gateway.

The particular advantages of the switch, the gateway, the computer program and the information carrier 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 drawings. appended in which: - Figure 1, already described, represents two sub-networks 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; FIG. 4 represents the main steps of a computer program according to the invention in a preferred embodiment;

FIGS. 5A to 5J show, schematically, an interconnection method according to the invention in a first embodiment; and

FIGS. 6A to 6G show an interconnection method according to the invention in a second preferred embodiment.

DETAILED DESCRIPTION OF THE TWO EMBODIMENTS We will now describe with reference to FIGS. 4 and 5A to 5J an interconnection method according to the invention in a first embodiment.

In this embodiment, the switches IA and IB 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 above with reference to FIG. 3, at the time of the interconnection of these sub-networks, one of the two so-called "edge" switches, for example the switch IA, sends a message SWJLS ELP to the other switch. said "edge" (ie the switch IB), this message having the value of the counter 10 R_A_TOV_A shared by all switches xA subnet A.

This message is received during a step ElO of receiving a computer program according to the invention, loaded and executed by the switch IB.

In accordance with the invention, this receiving step ElO is followed by a step E20 during which the switch IB 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 reconfiguration value R_A_TOV is chosen as the largest of the first values R_A_TOV_A, R_A_TOV_B is 15.

This determination step E20 is followed by an E25 test whose result is positive if the switches of the network must be reconfigured, and negative in the opposite case, 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 E0 waiting and receiving a message already described. Otherwise, this test E25 is followed by an optional step during which the switch IB rejects the interconnection of the two sub-networks, by sending the other switch called "edge", the message SW_ILS RJT already described.

After the sending of the SWJLS RJT rejection message (or at the output of the positive E25 test if the optional rejection step is not implemented), the so-called "edge" switch IB sends, during a step E30, an SW_ILS RCF reconfiguration message on all its EJ ³ OIt extension ports, in particular to the other so-called "edge" switch IA. This reconfiguration message is received by the switches

IA and 2B interconnected to the E_Port extension ports of the so-called "edge" switch IB.

For simplicity, the SWJLS 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 IA and 2B having received the SWJLS RCF reconfiguration message, respond to this message by sending a SWJLS ACC acknowledgment to the so-called " border »IB. This acknowledgment is received by the switch IB during a step E40 of acknowledgment waiting.

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

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

Thus, the switch IA transmits the SWJLS RCF reconfiguration message to the switch 2A; and

the switch 2B transmits this message to the switch 3B. With reference to FIG. SC, switches 2A and 3B, upon reception of the reconfiguration message, send a message acknowledging SW_ILS ACC respectively to the switch IA and switch 2B.

In addition, the switch 2A propagates the SWJLS RCF reconfiguration message to the switch 3A connected to its extension port E_Port.

After the acknowledgment standby step E40, in accordance with the invention, the switch IB sends, during a step E50, to each of its E_Port extension ports that have received an acknowledgment message SWJLS ACC. response to the reconfiguration message, a parameterization message SWJLS ELP having the reconfiguration value R_A_TOV determined during the step E20, namely the value 15.

With reference to FIG. 5D, the switches IA 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 IA has, after this step, a new lifetime counter equal to 15.

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

Similarly, the switch 3A acknowledges the receipt of the SWJLS RCF reconfiguration message by sending an acknowledgment message SWJLS ACC to the switch 2A. Still referring to FIG. 5D, the switch IA sends, on the E_Port extension ports having received a SWJLS ACC acknowledgment message from the switch 2A, the reconfiguration message SWJLS RCF.

Referring to Figure 5E, switch 2A acknowledges this reconfiguration message by sending an acknowledgment message SWJLS ACC to switch IA.

And switch 2A sends a SWJLS 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, switch 3A sends an acknowledgment message SW_ILS ACC in response to the received reconfiguration message from switch 2A.

And the switch IA 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 RCF, a parameter message

SWJLS ELP having the value R_Â_TOV reconfiguration, namely the value 15, determined in step E20.

With reference to FIG. 5G, the switch 2A, upon receipt of the SVVJLS ELP parameter message, modifies the value of its life counter in its memory M, and acknowledges the reception of this parameterization message by the sending of an acknowledgment message

SWJLS ACC to the IA switch.

On the other hand, the switch 2A sends a SWJLS RCF reconfiguration message on the extension port EJ ³ OIt through which it has received an acknowledgment message in response to the SWJLS RCF reconfiguration message that it has sent to the switch 3A as described. previously with 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. 51, the switch sends, on its extension port E_Port by which it has received this acknowledgment message, a parameterization message SWJLS ELP, this message comprising the value R_A_TOV 15 of reconfiguration.

Finally referring to FIG. 5J, the switch 3A, on receiving this reconfiguration message SWJLS ELP, modifies, in its memory M, the value of the lifetime counter and acknowledges, by sending a message SWJLS 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.

In this second embodiment, the islands A and B are interconnected by means of PA and PB bridges synchronized and connected by a tunnel T through an IP network. These gateways implement the computer program according to the invention. This tunnel T can notably be a link of a local 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 frame FSF (FCIP Special Frame), this frame being received by the gateway PB located at the other end of tunnel T.

In accordance with the FCIP protocol, this FSF frame includes a "Time Stamp" field containing the instant of sending this frame by the PA gateway.

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

In this second embodiment, if necessary, during this determination step, the R_A_TOV reconfiguration value equal to:

the duration DT of traversal of the IP link by the message if this duration is greater than the first two values R_A_TOV_A, R_A_TOV_B; and at the largest of the first values R_A_JOV_A,

R_A_TOV_B, if it is greater than the duration DT. If the first two values R_A_JOV_A, R_A_TOV_B are equal to and greater than the transit time 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 on 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 network switch performs the following operations:

- transmission, step by step, TWJSL RCF reconfiguration messages;

- acknowledgment of the reconfiguration messages; sending (E40) a TWJSL 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, a method for 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 (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), said method being characterized in that it comprises:

- A determination step, a value (R_A_TOV) called reconfiguration, 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).

2. Interconnection method according to claim 1, wherein said network is constituted by two islands (A, B) conforming to the Fiber Channel standard interconnected by two so-called "edge" switches (IA, IB, PA, PB) connected to each other. between them by 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 during which, a first of said so-called "edge" switches (IB, PB) sends, to the second (IA, PA) said so-called "edge" switches, a message (SWJLS, FCIP) comprising said counter (R_A_TOV_B) of its island (B); said method being characterized in that:

said reconfiguration value (R_A_TOV) is determined by said second so-called "edge" switch (IA, PA) from the counter (R_A_TOV_A) of its island (A) and at least one piece of information (R_A_TOV_B, TS_B) contained in said message (SWJLS, FCIP); and in that

said broadcasting step is initiated by said second so-called "edge" switch (IA, PA), by sending a reconfiguration message (SWJLS) followed by a setting message (SWJLS) 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 ISL type link defined by said standard, characterized in that said reconfiguration value (KAJOV), chosen by said second so-called "edge" switch (IA ) is the largest of said first values (R_AJΓOV_A, RJLTOVJ3).

4. Interconnection method according to claim 2, wherein said so-called "edge" switches are gateways (PA, PB) synchronized with each other and connected by a tunnel (T), characterized in that said reconfiguration value (R_A_TOV ), chosen by said second so-called "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 largest of the first values (R_A_TOV_A, R_A_TOV_B), if it is greater than said duration (DT), - said duration (DT) being obtained from a field of this message (FCIP).

5. Interconnection method according to claim 4, characterized in that said tunnel is IP type.

6. Switch (xA) capable of being connected to a sub-network (A) of a network (R), and comprising:

means (M) for storing a first value (R_A_TOV_A) representative of the maximum lifetime of a message within said sub-network (A); and

means (EJPort) for receiving a message (SWJLS, FCIP); said switch (xA) being characterized in that it comprises:

determination means, from said first value (R_A_TOV_A) and from at least one piece of information (R_Â_TOV_B, TS_B) contained in said message (SWJLS, FCIP), of a value (RJLTOV) said reconfiguration, this value being a permissible value for the maximum lifetime of a message within said network (R);

means for broadcasting said reconfiguration value (R_A_TOV) to all the switches (xA, xB) of said network (R); and - 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.

7. Switch according to claim 6, wherein said network (R) consists of two islands (A, B) conforming to the standard Fiber

Channel, said switch being connected to a first of said islands (A) by an ISL type link defined by said standard, and wherein said first value is a lifetime counter (R_A_TOV_A, R_A_TOV_B) 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 said second island (B), and obtained from said message (SWJLS).

8. Gateway (PA) capable of being connected to a sub-network (A) of a network (R), and comprising:

means (E_Port) for receiving a message (SWJLS, FCIP); said gateway (PA) being characterized in that it comprises:

means for determining, from said first value (R_Δ_TOV_A) and at least one piece of information (R_A_TOV_B, TS_B) contained in said message (SWJLS, FCIP), a value (R_Â_TOV) called a reconfiguration value, this value being a permissible value for the maximum lifetime of a message within said network (R);

means for broadcasting said reconfiguration value (R_A_TOV) to all the switches (xA, xB) of said network (R); and - Reconfiguration means able to substitute, in said storage means (M), said first value (R_A_TOV_A) by said value (R_Â_TOV) of reconflguration.

9. Gateway (PA) according to claim 8, wherein said network (R) consists of two islands (A, B) conforming to the Fiber Channel standard, said gateway (PA) being connected to a first of said islands (A). by an ISL type link defined by said standard, and wherein said first value is a lifetime counter (R_A_TOV_A, R_A_TOV_B) defined by said standard, said gateway (PA) being synchronized with a second gateway (PB) of said network (R) by a tunnel (T), 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 the 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 within said second island (B), 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).

10. Gateway (PA) according to claim 9, characterized in that said tunnel is IP type.

11. A computer program that can be executed by a switch (xA) or by a gateway (PA) that can be connected to a subnet (A) of a network (R), which program includes instructions for enforce :

a step of receiving a message (SWJLS, FCIP); this program being characterized in that it further comprises instructions for implementing: a determination step, based on a first value;

(R_A_TOV_A) representative of the maximum lifetime of a message within said sub-network (A), and at least one piece of information (R_A_TOV_B, TS_B) contained in said message (SWJLS, FCIP), of a value (R_A_TOV) called a 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_T0V) to all the switches (xA, xB) of said network (R); and

- A reconfiguration step, substituting, in the storage means (M) of the switch (xA), said first value (R_A_TOV_A) by said value (RJLTOV) of reconfiguration.

The computer program of claim 11, wherein said network (R) conforms to the Fiber Channel standard, said gateway (PA) being connected to said subnetwork (A) by an ISL type link defined by said standard , and wherein said first value is a lifetime counter (R_A_TOV_A, R_A_TOV_B) defined by said standard, characterized in that, during said determining step, said reconfiguration value (R_A_TOV) equal to;

the duration (DT) of crossing 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 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 it is greater than said duration (DT),

The computer program of claim 11, 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 the IP type, characterized in that, during said determining step, said value (RJLTOV) of reconfiguration equal to the duration (DT) of traversing said tunnel (T) by said message (FCIP), this duration being obtained from a field of this message (FCIP).

14. Information carrier readable by a switch (xA, xB) or by a gateway (PA, PB), possibly totally or partially removable, in particular CD-ROM or magnetic medium, such as a hard disk or a diskette, or transmissible medium , such an electrical or optical signal, characterized in that it comprises instructions of a computer program according to any one of claims li to 13, when this program is loaded and executed by this switch or by this gateway.

15. A network characterized in that it comprises at least one equipment selected from a switch (xA, xB) according to claim 6 or 7, and a gateway (PA, PB) according to any one of claims 8 to 10.