JP4136753B2 - Loop suppression method in LAN - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a loop suppression method in a LAN, and more particularly to a loop suppression method in a LAN that can easily and reliably suppress a loop in a wide-area LAN and prevent a service provider from deteriorating.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a wide area LAN such as a wide area Ethernet (registered trademark) network is constructed according to the IEEE802.1QtagVLAN method or a QinQtagVLAN (virtual LAN) method using the same. These methods transfer frames with almost the same structure as normal LAN frames (hereinafter referred to as MAC frames), and a VLAN identifier (tag) is added to the MAC frame to identify the logical LAN. By doing so, a wide area LAN capable of accommodating a large number of logical networks is realized.
[0003]
FIG. 9 shows a frame configuration in the IEEE802.1Qtag VLAN method. This frame includes a destination MAC address, a source MAC address, a VLAN identifier (tag), and data, and the VLAN identifier (tag) is an identifier for identifying a logical LAN, and realizes a wide area LAN. It is given to. This frame configuration includes SFD, TPID, CFI, FCS (frame check sequence) which is a bit string for enabling detection of transmission errors on the receiving side, and the like.
[0004]
FIG. 10 is an explanatory diagram of the MAC frame transmission operation from the subscriber terminal. For simplification, only the destination MAC address field, source MAC address field, and data field of the MAC frame are shown here. Usually, a subscriber terminal is assigned a terminal-specific address at the time of manufacture. At the time of transmission, the address is set in the source MAC address field, and the address of the partner subscriber terminal is set in the destination MAC address field. Sent to the LAN switch.
[0005]
The LAN switch creates a MAC address learning table by registering the combination of the source MAC address B in the MAC frame received from the subscriber terminal and the port (2) that received the LAN frame.
[0006]
In FIG. 10, the pair of the destination MAC address A and the port (1) has already been registered, and further, the pair of the source MAC address B and the port (2) is registered by learning in the reception of the current MAC frame. Indicates the state. The MAC address learning table is referred to in order to determine the transfer destination in the subsequent transfer of the MAC frame.
[0007]
The LAN switch refers to the destination MAC address A in the MAC frame and the contents registered in the MAC address learning table, and sends the MAC frame from the port (1).
[0008]
It is also considered to increase the availability of a wide-area LAN by constructing a LAN switch in a redundant configuration and constructing a network having a plurality of routes.
[0009]
[Problems to be solved by the invention]
However, when a telecommunications carrier constructs a wide-area LAN using the IEEE802.1QtagVLAN method or the QinQtagVLAN method using the IEEE802.1QtagVLAN method, and further makes the LAN switch redundant in order to improve reliability, there are the following problems.
[0010]
The types of destination MAC addresses include a broadcast address destined for all subscriber terminals, a multicast address destined for a certain group of subscriber terminals, and a unicast address destined for one subscriber terminal. Of the unicast addresses, those not registered in the MAC address learning table in the LAN switch are particularly referred to as unknown unicast. LAN frames with unicast addresses whose destination MAC address is not unknown unicast are forwarded to the ports registered in the MAC address learning table, but other broadcast, multicast, and unknown unicast frames are usually received ports. Forward to all ports except.
[0011]
If the LAN switch is simply configured in a redundant configuration, frames input to the network, especially broadcast frames, continue to circulate in the network and multiply depending on the network connection status. As a result, the communication band in the network is wasted, and finally a communication incapable state is generated, which causes a so-called loop phenomenon.
[0012]
In order to prevent this phenomenon from occurring, a technology is used to physically eliminate a logical configuration while taking a redundant configuration. The most common of this technique is STP (spanning tree protocol). However, in STP, when a redundant protocol that suppresses loops is operating normally, the occurrence of loops can be suppressed, and alternative routes can be established when a failure occurs. If a problem occurs in the processing of the redundant protocol due to a mistake in operation of the LAN switch, the logical configuration may be incorrect and a loop may occur. The loop not only squeezes normal communication traffic, but also rewrites the contents of the MAC address learning table in the LAN switch to the wrong contents, so the influence on communication is extremely large.
[0013]
The object of the present invention is considered in view of the above points, and even when there is a problem in the processing of the redundant protocol, it is possible to easily and reliably suppress a loop in the LAN, and to prevent a decrease in service by a communication carrier. It is an object of the present invention to provide a loop suppression method in a LAN capable of performing the above.
[0014]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention provides a loop in a LAN comprising a subscriber accommodation switch that accommodates a subscriber terminal and a core network having a core switch that controls frame transfer between the plurality of subscriber accommodation switches. In the deterrence method, the subscriber accommodation switch forms a new frame by adding its own address as a transfer source address to a frame transmitted from a subscriber terminal accommodated by itself, and directs the frame to the core network. The subscriber accommodation switch and the core switch determine whether the frame received via the core network is the same as the frame transferred by itself. The source address added to the received frame and the frame transferred by itself The first feature is that, when the determination is made based on the transfer source address and it is determined that they are the same, the frame is not transferred.
[0015]
The second feature of the present invention is that the address of the subscriber accommodation switch can be arbitrarily set.
[0016]
The third feature of the present invention is that the address of the subscriber accommodation switch is set to be different for each subscriber accommodation switch.
[0017]
Furthermore, the present invention has a fourth feature in that the address of the subscriber accommodation switch is set to an address having regularity in geographical or logical configuration.
[0018]
According to the first feature, the loop can be reliably suppressed based on the address of the subscriber accommodation switch, and since the address of the subscriber accommodation switch is smaller than the MAC address of the LAN terminal, it has been transferred. It becomes easy to determine and process whether or not the LAN frame forms a loop.
[0019]
Further, according to the second feature, it is possible to easily determine whether or not the transferred LAN frame forms a loop based on an arbitrarily set address of the subscriber accommodation switch.
[0020]
Further, according to the third feature, loop suppression can be achieved for each subscriber accommodation switch, and according to the fourth feature, loop suppression can be achieved for each region or for each PE switch.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings. The present invention configures a new frame (hereinafter referred to as a MACinMAC frame) by adding its own address as a transfer source address to a MAC frame sent from a subscriber terminal accommodated in the subscriber accommodation switch. This MACinMAC frame is transferred to the core network, and the subscriber accommodation switch and the core switch use the transfer source address as to whether the MACinMAC frame received via the core network is the same as the MACinMAC frame transferred by itself. Based on the determination result, transfer of the MACinMAC frame is controlled.
[0022]
FIG. 1 is a block diagram showing an example of a wide area LAN to which the present invention is applied. The LAN of this example is a subscriber accommodation switch (hereinafter referred to as a PE switch) that accommodates subscriber terminals (PE is a provider). And a core network 3 having a core switch 4 that controls transfer of MACinMAC frames between the PE switches 1 and 2.
[0023]
A wide-area LAN generally has more PE switches and core switches, but here, for simplicity of explanation, the PE switch 1 housing the source subscriber terminal A and the destination subscriber Only the core switch 4 that controls the transfer of the MACinMAC frame between the PE switch 2 that accommodates the terminal B and the PE switches 1 and 2 is shown, and there is only one core switch 4 between the PE switches 1 and 2.
[0024]
The MAC addresses of the subscriber terminals A and B are α and β, respectively, and a and b are set as the MAC addresses of the PE switches 1 and 2 (hereinafter referred to as MACinMAC addresses), respectively. To do. The MACinMAC address can be arbitrarily set by the communication carrier.
[0025]
First, the configuration of the MACinMAC frame generated in the PE switch and its transfer will be described. When the MAC frame transmitted from the subscriber terminal A (MAC address: α) is transferred to the subscriber terminal B (MAC address: β) via the core network 3, the MAC frame transmitted from the subscriber terminal A is PE. Received by switch 1. This MAC frame includes a source MAC address (SA1: α), a destination MAC address (DA1: β), and data (DATA: Hello). The MAC frame usually includes a VLAN identifier for identifying a logical LAN, but is not shown.
[0026]
PE switch 1 receives the MAC frame of its own MACinMAC address (SA2: a), the MACinMAC address of PE switch 2 that accommodates subscriber terminal B (DA2: b), and core network 3 logically privately. An identifier L2VPN (tag: Company X) for dividing into a network VPN (virtual private network) is added to form a MACinMAC frame, which is transmitted from the output port. The output port is determined with reference to the MAC address learning table in the PE switch 1, and details thereof will be described later.
[0027]
The core switch 4 receives the MACinMAC frame, determines the output port with reference to the MAC address learning table and the MACinMAC address (DA2: b) in the MACinMAC frame, and sends the received MACinMAC frame from the output port. . This MACinMAC frame is received by the PE switch 2.
[0028]
PE switch 2 extracts (decapsulates) the MAC frame from the received MACinMAC frame, determines its output port by referring to its own MAC address learning table and the MAC address (DA1: β) in the MAC frame, and outputs it Send MAC frame from port. The subscriber terminal b receives the MAC frame transmitted from the PE switch 2.
[0029]
FIG. 2 is a diagram showing an operation outline when the destination MAC address is not registered in the MAC address learning table in the PE switches 1 and 2 and the transfer destination MACinMAC address is not registered in the MAC address learning table in the core switch 4. It is. It is assumed that a PE switch 5 is further connected to the core switch 4.
[0030]
In FIG. 2, the MAC frame (DA1: β, SA1: α, DATA: Hello) transmitted from the subscriber terminal A is received by the PE switch 1 at the port (1). The PE switch 1 learns the received MAC frame and creates a MAC address learning table.
[0031]
The MAC address learning table in the PE switch registers the key area for registering the source address (MAC), the physical port (IF) where the frame arrived, and the address (transfer) of the PE switch that transferred the frame. And a destination area. In this example, MAC: α and IF: (1) are registered in the MAC address learning table of the L2VPN associated with the physical port where the MAC frame arrived. Since the MAC frame is not transferred through the PE switch, it is not registered in “transfer”.
[0032]
In this MAC address learning table, an area for registering an identifier “VLAN-ID” for identifying a logical LAN can be provided. In this case, if the frame transmitted from the subscriber terminal A does not have a frame configuration conforming to IEEE802.1Q, the default VLAN-ID is registered in the VLAN-ID.
[0033]
Next, the PE switch 1 checks whether or not the destination MAC address (DA1: β) of the received MAC frame is in the MAC address learning table of the L2VPN to which the MAC frame belongs. When a VLAN-ID is registered, it is checked whether a destination MAC address and VLAN-ID pair exists in the MAC address learning table.
[0034]
If the destination MAC address is not in the MAC address learning table (not registered by learning), PE switch 1 converts the MAC port into all MACinMAC frames for which the L2VPN to which it belongs (excluding the input port) is set. Forward the frame. MACinMAC framing is the MAC frame transmitted from the subscriber terminal, the PE switch address (DA2) containing the destination subscriber terminal, the MAC address of the PE switch itself (SA2), and if necessary, This means that an identifier L2VPN (VPN-ID) for logically dividing into a virtual private network is added to form a new frame.
[0035]
In this example, DA2: Multicast (meaning multicast), SA2: a, VPN-ID: 100, DA1: β, SA1: α, DATA: Hello are configured as MACinMAC frames.
[0036]
In PE switch 1, if there is a port belonging to the same L2VPN in the downlink side port other than the physical port where the frame arrived, the frame is not converted into a MACinMAC frame in all the downlink side ports. When there is a port belonging to the same L2VPN on the uplink side, the MACinMAC frame is transferred to all the ports belonging to it. In that case, in MACinMAC framing, set “Multicast” in DA2, set “MACinMAC address” of the frame in SA2, and set L2VPN to which the physical port where the frame arrived belongs in VPN-ID .
[0037]
Also, a “TTL (time to live)” field can be provided, and a preset value can be set here. This value is decremented by 1 for each transfer at the PE switch and the core switch, and a frame whose value is 0 is discarded and used to stop the transfer.
[0038]
Note that PE switch 1 also sets “Multicast” to DA2 even if the type of destination MAC address DA1 is a broadcast address or multicast address, and all ports to which the associated L2VPN is set (excluding the input ports) ) For MACinMAC frames.
[0039]
The core switch 4 in the core network 3 receives the MACinMAC frame sent from the PE switch 1 and creates a MAC address learning table from the transfer source MACinMAC address (SA2). The MAC address learning table in the core switch 4 includes a key area for registering the address of the transfer source PE switch (transfer MAC) and a destination area for registering the physical port (IF) where the frame arrived. Have.
[0040]
In this example, forwarding MAC: a and IF: (1) are registered in the MAC address learning table of L2VPN related to the physical port where the frame arrived. In this MAC address learning table, an area for registering an identifier L2VPN (VPN-ID) for logically dividing into a virtual private network can be provided.
[0041]
Further, the core switch 4 transfers the MACinMAC frame to all the ports (excluding the input port) to which the L2VPN belonging to the frame is set according to DA2: Multicast in the frame.
[0042]
Similar operations are performed in the PE switches 2 and 5, and MAC: α, IF: (1), and transfer: a are registered in the MAC address learning table in the PE switches 2 and 5.
[0043]
The PE switches 2 and 5 extract the MAC frame (DA1: β, DA2: α, DATA: Hello) from the received MACinMAC frame, and send it out by multicast. The subscriber terminal B whose MAC address is β receives this MAC frame.
[0044]
FIG. 3 is a diagram showing an operation outline when the destination MAC address is registered in the MAC address learning table of the PE switches 1 and 2 and the transfer destination MACinMAC address is registered in the MAC address learning table of the core switch 4. is there. Here, it is assumed that the MAC address learning table having the contents described with reference to FIG. 2 has already been created and the MAC frame transmitted from the subscriber terminal B is transmitted to the subscriber terminal A.
[0045]
In FIG. 3, the MAC frame (DA1: α, SA1: β, DATA: Hello) transmitted from the subscriber terminal B is received by the PE switch 2 via the port (2). The PE switch 2 learns the received MAC frame and creates a MAC address learning table. In this example, MAC: β and IF: (2) are registered in the MAC address learning table of L2VPN related to the physical port where the frame arrived.
[0046]
Next, the PE switch 2 checks whether or not the destination MAC address (DA1: α) of the received MAC frame is in the MAC address learning table of the L2VPN to which the MAC frame belongs. In this case, since the destination MAC address (DA1: α) is in the MAC address learning table, the MACinMAC frame is transferred to the physical port (1) corresponding to DA1: α. The MACinMAC frame includes DA2: a, SA2: c, VPN-ID: 100, DA1: α, SA1: β, and DATA: Hello.
[0047]
The core switch 4 receives the MACinMAC frame sent from the PE switch 2 and creates a MAC address learning table from the transfer source MACinMAC address (SA2). In the case of this example, forwarding MAC: c, IF: (3) is registered in the MAC address learning table of L2VPN related to the physical port where the frame arrived. The core switch 4 checks whether or not the transfer destination MACinMAC address (DA2: a) of the received MACinMAC frame is in the MAC address learning table of the L2VPN to which the core switch 4 belongs. In this case, since the transfer destination MACinMAC address (DA2: a) is in the MAC address learning table, the MACinMAC frame is transferred to the physical port (1) corresponding to DA2: a and is not transferred to the physical port (2).
[0048]
A similar operation is performed in the PE switch 1, and MAC: β, IF: (2), and transfer: c are registered in the MAC address learning table in the PE switch 1.
[0049]
The PE switch 1 extracts a MAC frame (DA1: α, SA1: β, DATA: Hello) from the received MACinMAC frame, and transmits it from the port (1). The subscriber terminal A whose MAC address is α receives this MAC frame.
[0050]
As described above, the MAC frame and the MACinMAC frame are transferred according to the contents registered in the MAC address learning table. However, when the MAC address type is broadcast in particular, as described above, the frame Since it is sent to a physical port (excluding an input port), it may continue to circulate in the core network 3 and a so-called loop phenomenon may occur. This phenomenon not only wastes the communication bandwidth in the core network 3 and causes an incommunicable state, but also writes unnecessary contents in the MAC address learning table and must be suppressed. .
[0051]
Next, the loop suppression function provided in the PE switch and the core switch will be described. FIG. 4 is an explanatory diagram of an example of loop suppression in units of regions and PE switches. Set the PE switch MACinMAC address in region 1-1-1 to A: A: A: *: *: *, and the PEin MAC address in region 1-1-2 is A: A: B: *: *: Set to *. Note that * indicates that the PE switches in the same region are different from each other but are optional.
[0052]
The PE switch in region 1-1, which integrates region 1-1-1 and region 1-1-2, can be expressed by the address A: A: *: *: *: *. Similarly, by setting the PE switch MACinMAC address of region 1-2 PE switch to A: B: *: *: *: *, region 1-1 and region 1-2 are merged. The switch can be expressed by the address A: *: *: *: *: *. FIG. 4 also shows a PE switch in which a MACinMAC address of B: B: B: 1: 1: 1: 1 is set.
[0053]
Here, if the filter F1 is prepared for the PE switch or the core switch at the location A1, and the MACinMAC frame that is once sent out of the area 1-1-1 and then flows backward is discarded here, a loop based on the backward flow is generated. Deterred. At this time, whether or not the MACinMAC frame has flowed back can be easily determined by whether or not the MACinMAC address has A: A: A: *: *: *, and if the filter F1 is an address filter for it, Good. Similarly, if the filter F2 is prepared for the PE switch or core switch at the location A2, and the MACinMAC frame that has been once sent out of the area 1-1 and then backflowed is discarded here, the loop based on the backflow is suppressed. Is done. At this time, whether or not the MACinMAC frame has flowed back can be easily determined by whether or not the MACinMAC address has A: A: *: *: *: *.
[0054]
If a filter F3 is prepared for the PE switch or core switch at the location A3, and the MACinMAC frame once sent from the PE switch and flowing backward is discarded here, a loop based on the backward flow is suppressed. At this time, whether or not the MACinMAC frame has flowed back can be easily determined by whether or not the MACinMAC address has B: B: B: 1: 1: 1. This makes it possible to suppress loops in units of PE switches.
[0055]
In this way, by setting addresses having regularity in geographical or logical configuration and combining address filters, reverse flow of MACinMAC frames, that is, loops, can be suppressed for each region or each PE switch. The MACinMAC address can be arbitrarily set by the carrier (provider), and it is possible to set a geographically or logically regular address in the carrier. Therefore, it is easy to configure an address filter for suppressing loops.
[0056]
The processing in the PE switch and the core switch described above is summarized as shown in FIGS. FIG. 5 is a flowchart showing processing (Ingress operation) when the PE switch receives a MAC frame from the subscriber terminal side (downlink port).
[0057]
When the PE switch receives a MAC frame from the subscriber terminal (S501), the PE switch learns the received MAC frame and creates a MAC address learning table (source MAC address (SA1), VPN-ID, input port) ( S502).
[0058]
Next, it is checked whether or not the destination MAC address (DA1) is multicast or broadcast (S503). If it is multicast or broadcast, the process proceeds to S504, and if not, the process proceeds to S505. In S504, multicast is set in the transfer destination MACinMAC address (DA2), and the address held by the own apparatus is set in the transfer source MACinMAC address.
[0059]
Next, the MACinMAC frame is transferred (flooding) to all ports other than the port that received the MAC frame among the VPN ports to which it belongs (S506). When there is a port for a subscriber other than the port that received the MAC frame, the received MAC frame is transferred to the port as it is.
[0060]
In S505, the MAC address learning table is searched with the destination MAC address (DA1) and VPN-ID. It is checked whether or not it has been searched (S507). If it is searched, the process proceeds to S508, and if it is not searched, the process proceeds to S504. In S508, it is checked whether the port corresponding to the destination MAC address (DA1) is a downlink port or a core network port. If the port is a downlink port, the received MAC frame is directly transferred to the port (S509). If it is a core network port, set the forwarding MACinMAC address (DA2) to the address obtained by the search, set the forwarding MACinMAC address (SA2) to the address associated with the input port of the device, and set the MACinMAC After generating the frame (S510), the MACinMAC frame is transferred to the port (S511).
[0061]
FIG. 6 is a flowchart showing processing (Egress operation) when the PE switch receives a MACinMAC frame from the core network side (core network port).
[0062]
When the PE switch receives the MACinMAC frame (S601), the PE switch compares the transfer source MACinMAC address (SA2) with the address held by itself (S602). If the comparison result is coincident, the received MACinMAC frame is discarded as a frame that has returned after forming a loop (S603). This is the loop suppression function at the PE switch.
[0063]
If the comparison result does not match, the received MACinMAC frame is learned and a MAC address learning table (source MAC address (SA1), VPN-ID, source MACinMAC address (SA2), input port) is created. (S604).
[0064]
Next, it is checked whether or not the transfer destination MACinMAC address (DA2) is the address of the own apparatus, multicast or broadcast (S605). The process proceeds to S607. In S607, the received MACinMAC frame is discarded or flooded to the core network.
[0065]
In S606, it is checked whether or not the transmission destination MAC address (DA1) is multicast or broadcast. If it is multicast or broadcast, the process proceeds to S610, and if not, the process proceeds to S608. In S610, the MACinMAC frame is flooded to all ports other than the port that received the MACinMAC frame among the VPN ports to which it belongs. The MACinMAC frame is transferred as it is to the core network port other than the port that received the MACinMAC frame, and the MACinMAC frame is decapsulated and transferred to the port for the subscriber.
[0066]
In S608, the MAC address learning table is searched with the destination MAC address (DA1) and VPN-ID. It is checked whether or not this has been searched (S609). If not searched, the process proceeds to S610, and if searched, the process proceeds to S611. In S611, it is checked whether the port corresponding to the destination MAC address (DA1) is a downlink port or a core network port. If the port is a downlink port, the received MACinMAC frame is decapsulated and transferred to the port ( If it is a core network port (S612), the received MACinMAC frame is transferred to the port as it is (S613).
[0067]
FIG. 7 is a flowchart showing processing in the core switch. When the core switch receives the MACinMAC frame (S701), the core switch compares the transfer source MACinMAC address (SA2) with the contents of the preset loop suppression filter (S702). If the comparison result is coincident, the received MACinMAC frame is discarded as a frame that has returned after forming a loop (S703). This is the loop suppression function at the core switch.
[0068]
If the comparison results do not match, the received MACinMAC frame is learned to create a MAC address learning table (transfer source MACinMAC address (SA2), VPN-ID, input port) (S704).
[0069]
Next, it is checked whether or not the transfer destination MACinMAC address (DA2) is multicast or broadcast (S705). If it is multicast or broadcast, the process proceeds to S708, and if not, the process proceeds to S706.
[0070]
In S708, the MACinMAC frame is flooded to all ports other than the port that received the MACinMAC frame among the VPN ports to which it belongs. In S706, the MAC address learning table is searched with the transfer destination MACinMAC address (DA2) and VPN-ID. It is checked whether or not it has been searched (S707). If not searched, the process proceeds to S708, and if searched, the process proceeds to S709. In S709, the received MACinMAC frame is directly transferred to the port corresponding to the transfer destination MACinMAC address (DA2).
[0071]
FIG. 8 is a diagram illustrating a specific configuration example of the MACinMAC frame. The MACinMAC frame has a configuration in which a transfer destination MACinMAC address, a transfer source MACinMAC address, an L2VPN identifier, a MACinMAC frame identifier, and a MACinMAC TTL are added to the outside of a normal MAC frame.
[0072]
FIG. 8 shows a MAC frame (a-1) according to IEEE 8-2.1Q and a MAC frame (a-2) according to Ethernet (registered trademark) II, 802.3. These MAC frames are mounted on the payload, and a 1-byte MACinMAC TTL and 1-byte “reservation” are added to generate an intermediate MACinMAC frame (b). Note that the MAC frame is mounted on the payload excluding the preamble, SFD, and FCS. The TTL is set to a preset value (maximum 255). This value is decremented by 1 for each transfer at the PE switch and the core switch, and a frame whose value is 0 is discarded without being transferred.
[0073]
In addition, this intermediate MACinMAC frame (b) is installed in the payload, preamble, SFD, intra-network transfer destination MAC address (transfer destination MACinMAC address), intra-network transfer source MAC address (transfer source MACinMAC address), TPID , TCI, MACinMAC TPID, and FCS are added to generate a MACinMAC frame (c-1) encapsulated in IEEE802.1Q.
[0074]
In addition, an intermediate MACinMAC frame is installed on the payload, and it is encapsulated in an UntagEthernet (registered trademark) frame with a preamble, SFD, destination MAC address for intra-network transfer, source MAC address for intra-network transfer, TYPE, and FCS. A MACinMAC frame (c-2) can also be generated.
[0075]
Here, TPID and TYPE are used to determine the encapsulated MACinMAC frame, and are set to 0xE0E0, for example. The TPID is set to 0X8100, for example, when IEEE802.1Q is used, but may be set to 0x9100, for example, when a MACinMAC frame is transferred by a VMAN (virtual metropolitan area network) switch or the like.
[0076]
Although the embodiments have been described above, the present invention does not need to have a function of determining and controlling whether or not to transfer a frame to all of the PE switch and the core switch. It is only necessary that the PE switch and the core switch at the location have the function of determination and control. In addition, the STP technique can be used in combination with the present invention and is not excluded.
[0077]
【The invention's effect】
As described above, according to the present invention, a loop can be reliably suppressed based on the address of the PE switch. At this time, the operator can arbitrarily set the PE switch address, and Since the number is smaller than the MAC address of the subscriber terminal, it is easy to determine and process whether or not the transferred MACinMAC frame forms a loop.
[0078]
In addition, by setting the address of the PE switch to an address having regularity in terms of geographical or logical configuration, it is possible to effectively suppress the loop for each region or each PE switch.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an example of a LAN to which the present invention is applied.
FIG. 2 is a schematic explanatory diagram of an operation example in the present invention.
FIG. 3 is a schematic explanatory diagram of another operation example in the present invention.
FIG. 4 is an explanatory diagram of an example of loop suppression in units of regions and PE switches.
FIG. 5 is a flowchart illustrating an example of a MAC frame reception process in a PE switch.
FIG. 6 is a flowchart showing an example of MACinMAC frame reception processing in a PE switch.
FIG. 7 is a flowchart illustrating an example of processing in a core switch.
FIG. 8 is a diagram illustrating a specific configuration example of a frame configured according to the present invention.
FIG. 9 is a diagram showing a frame configuration in the IEEE802.1Qtag VLAN method.
FIG. 10 is an explanatory diagram of a MAC frame transmission operation from a subscriber terminal.
[Explanation of symbols]
1, 2, 5, PEsw ... (subscriber accommodation) switch, 3 ... core network, 4, SW ... core switch, A, B ... subscriber terminals, F1, F2, F3 ...・ Loop suppression filter

Claims (4)

In a loop suppression method in a LAN comprising a subscriber accommodation switch that accommodates subscriber terminals and a core network having a core switch that controls frame transfer between a plurality of subscriber accommodation switches,
The subscriber accommodation switch configures a new frame by adding its own address as a transfer source address to a frame transmitted from a subscriber terminal accommodated by itself, and forwards the frame toward the core network,
The subscriber accommodation switch and the core switch determine whether the frame received via the core network is the same as the frame transferred by the subscriber switch and the transfer source address added to the received frame. A loop suppression method in a LAN, which is determined based on a transfer source address of a transferred frame and does not transfer the frame when it is determined that they are the same. 2. The LAN loop suppression method according to claim 1, wherein an address of the subscriber accommodation switch can be arbitrarily set. 3. The LAN loop suppression method according to claim 1, wherein an address of the subscriber accommodation switch is set to be different for each subscriber accommodation switch. 4. The LAN loop suppression method according to claim 1, wherein the address of the subscriber accommodation switch is set to an address having regularity in geographical or logical configuration.

Images