JP3456891B2 - Router device and frame transfer method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a router device capable of connecting communication networks such as Ethernet and transferring frames, and a frame transfer method.

[0002]

2. Description of the Related Art Router devices are different LANs (Local Area N
Etwork) to connect between
From one LAN to the other LAN.
In the datagram, in addition to the communication information to be transferred, the source and final destination network layer addresses (for example, IP address in IP (Internet Protocol)) are described. The output network interface of the datagram and the transfer destination node (router device or host) are determined using the datagram.

In a conventional router device, a data link layer (eg MAC (Media Access Control)) is used rather than a LAN.
When a data link layer frame (MAC frame) defined in (layer) is received, the frame is subjected to data link layer processing and then converted into a packet (datagram) handled in the network layer. Then, based on the network layer address of the final destination described in this datagram, the output interface of this datagram and the network layer address of the next-stage node to be transferred are determined, and this datagram is passed to the corresponding output interface. . In the output interface, after determining the data link layer address from the network layer address of the next-stage node,
Builds a data link layer frame and outputs it to the LAN.

In the router device which transfers the communication information (data link frame) according to the above procedure, after converting the received data link layer frame into a packet of the network layer, the packet such as the final destination address and the source address is converted. , The node to which the packet should be sent next (the next-stage router or destination host), and the output interface are determined based on the routing table held by the router, and the data link layer frame is converted again. The operation of outputting to the next stage node is performed.

At this time, due to an excessive amount of processing in the router, such as conversion of the received data link layer frame into a network layer packet, retrieval of a routing table, conversion of the packet into a data link frame, the conventional router receives the data. The processing time required to transfer the data link layer frame and the processing load inside the router are large.

[0006]

In order to reduce the load of the above router processing, there is a method of determining the transfer destination of the frame at the data link layer level without referring to the information at the network layer level described in the packet. It has been proposed (this transfer method may be referred to as cut-through hereinafter).

One is intermediate header information (for example, LLC (Logical
Link Control) header) and a virtual identifier assigned in correspondence with the final destination information and the source information are added to enable switching at the data link layer frame level.

That is, the router device that receives the frame checks the LLC header to perform normal network layer datagram processing for the frame and then transfers the frame, or cuts through the data link layer frame as it is. Decide whether to transfer. If cut-through transfer is to be performed, data link layer switching transfer is performed based on the virtual identifier added to the intermediate header information.

However, in this method, a few bytes of information is newly added to the header information, so that the length of the portion of the frame in which the upper datagram can be inserted becomes short. This means that the maximum packet length that can be used when switching in the data link layer frame is different from the maximum packet length that can be used in normal datagram transfer.
Then, when a datagram is sent from a source host that does not support the above method, it is necessary to readjust the packet length at the first router. Further, even in a node supporting the above method, it is necessary to perform processing such as changing the packet length at the network layer when switching from normal transfer to data link layer switching transfer.

On the other hand, a method of giving a virtual identifier necessary for data link layer switching by using a local address field defined by a data link layer address used in LAN is also conceivable.

That is, a dedicated virtual identifier is assigned to each packet flow for which cut-through transfer is desired, and this virtual identifier is entered in the destination MAC address field or source MAC address field of the frame. Then, the router device that receives the frame in which any one of the MAC addresses is local performs the data link layer switching transfer based on the virtual identifier described in the MAC address field.

When the virtual identifier is used in the destination MAC address field, it is necessary to store a new MAC address so that each receiving node (router or host) can receive the local destination MAC address. become. So if you want to do data link layer switching for each of a number of packet flows,
Each node must store multiple virtual identifiers as the MAC address it should receive.

In this case, when there is an Ethernet switch between the nodes such as Ethernet, the Ethernet switch can relay the frame in which the local destination MAC address is written to an appropriate node. Must store multiple MAC addresses.

When the virtual identifier is used in the source MAC address described in the field, a large number of source MAC addresses that the bridge device with a learning function forming the LAN does not need to store are learned. This will consume a lot of MAC address storage area in the bridge device.

The present invention aims to improve the transfer efficiency of the router device by utilizing the switching at the data link layer frame level, and at the same time, it is necessary to readjust or change the packet length in the node or the bridge, the Ethernet switch or the like. The purpose is to give a virtual identifier that can be used for data link layer switching so that it is not necessary to store many MAC addresses.

[0016]

A router device according to the present invention uses a region which is a frame to be transferred at a data link layer level and which is defined as a region for writing upper layer protocol identification information, Receiving means for receiving a frame in which information for identifying the packet flow to which the frame belongs in the data link layer is entered, an identifier capable of identifying the packet flow, and the next stage to which the frame belonging to this packet flow should be transferred. Storage means for storing the correspondence relation with the address information of the node, and the correspondence relation stored in the storage means by using the information written in at least the area of the frame received from the preceding node by the reception means as an identifier. By referring to the address information of the next-stage node obtained without performing network layer processing, Imparting to, characterized in that by comprising a transfer means of the data link layer level transfer.

Here, the receiving means includes means for receiving another frame to be transferred at a network layer level from a node belonging to a certain logical network, and the router device assembles the other frame into a packet, The packet may be subjected to a network layer process, framed again, and transferred to a node belonging to another logical network at a network layer level.

Further, information indicating whether or not the address information written in the address area of the frame received by the receiving means includes information dedicated to the transfer at the data link layer level (of the frame). For example, by detecting from multiple bits at a predetermined position in the address area,
It may further comprise means for passing the frame to the data link layer level transfer means or the network layer level transfer means based on the detection result.

The storage means not only identifies the flow to which the packet belongs, and the information for specifying the next-stage node written in the destination address area, but also allows the next-stage node to identify this flow. The correspondence relationship with a new identifier that enables In this case, the transfer means at the data link layer level writes the information based on this new identifier in the area defined as the area for writing the upper layer protocol identification information of the frame. The information entered in the destination address area of the frame can be the address including the node identifier assigned to the node in the next stage exclusively for the data link layer level transfer. An address fixedly assigned to the next-stage node for transfer at the network layer level is entered, and information based on a part of the new identifier is entered in the transmission source address area (this router device dedicated to transfer at the data link layer level). Alternatively, the address including the node identifier assigned to the next node) can be entered.

On the other hand, the storage means can identify not only the identifier for identifying the flow to which the packet belongs and the information for specifying the next-stage node written in the destination address area, but also the upper layer protocol of this packet. Corresponding relations with different protocol identification information may be stored. In this case, the transfer means at the data link layer level writes this protocol identification information in the area defined as the area for writing the upper layer protocol identification information of the frame. In the destination address area, an address fixedly assigned to the next-stage node for transfer at the network layer level can be entered.

Further, the present invention (which uses the destination address area) uses a region which is a frame to be transferred at the data link layer level and which is defined as a region for writing the upper layer protocol identification information. , A receiving means for receiving a frame in which information for identifying the packet flow to which the frame belongs is identified in the data link layer, an identifier capable of identifying the packet flow, and a frame to which the frame belongs to Storage means for storing the correspondence relationship with the address information of the node of the stage, and the correspondence relationship stored in the storage means with the information written in at least the area of the frame received from the node of the preceding stage by the receiving means as an identifier By referring to, the address information of the node at the next stage obtained without performing the network layer processing can be obtained. Characterized by comprising a transfer means of the data link layer level transfer the frame to impart a destination address region of at least the frame.

In this case, the means for storing the address including the node identifier assigned to the router device exclusively for the data link layer level transfer, and the receiving means for storing the stored address in the destination address area. It may further comprise means for controlling the receiving frame to be received.

Further, the data link switch for routing the frame by using the destination address as a key can perform the frame routing by using the address including the node identifier assigned to the router device exclusively for the data link layer level transfer as a key. A means for transmitting a frame in which the dedicated address is added to the transmission source address area may be provided.

Further, the present invention (using the source address area) uses the area which is to be transferred at the data link layer level and which is defined as an area for writing the upper layer protocol identification information. Then, a receiving unit that receives a frame in which information for identifying the packet flow to which the frame belongs is identified in the data link layer, an identifier that can identify the packet flow, and the frame that belongs to this packet flow should be transferred. It is defined as a storage unit that stores the correspondence relationship with the address information of the node of the next stage, and a source address region of the frame received from the node of the previous stage by the receiving unit and a region for writing the upper layer protocol identification information. Refer to the correspondence stored in the storage means using the information entered in the area as an identifier. In addition, the data link layer level transfer means for transferring the frame by assigning the address information of the next-stage node obtained without performing the network layer processing to the destination address area of the frame is provided. And

In the identifier at this time, the portion corresponding to the source address area can include a node identifier assigned to the router device or the preceding node exclusively for data link layer level transfer. .

Here, in the storage means, not only the identifier capable of identifying the flow to which the packet belongs and the address of the node at the next stage, but also the node at the next stage identifies this packet flow in the data link layer. A new identifier (which can include the node identifier assigned to the next node or the router device dedicated to the data link layer level transfer) is stored, and the data link layer level transfer means is stored. It is also possible to write this new identifier in the area defined as the source address area of the frame and the area for writing the upper layer protocol identification information.

The invention related to each device of the present invention is also understood as a method related invention. For example, in the frame transfer method according to the present invention, an identifier that can identify the flow to which a packet received from a certain logical network belongs in the data link layer and another identifier to which the data link layer frame of the packet belonging to this flow should be transferred. If the correspondence with the address information of the next node belonging to the logical network is stored and the information written in the address area of the received frame indicates that the frame should be transferred at the data link layer level. For example, by referring to the stored correspondence relationship using the information entered in the area defined as at least the upper layer protocol identification information of the frame as an identifier, without performing the network layer processing. It is characterized in that the obtained address information of the next-stage node is added to the frame and transferred. .
Furthermore, if the frame is not to be transferred at the data link layer level, the frame is assembled into a packet,
The packet may be subjected to network layer processing, framed again, and transferred to another logical network.

The present invention can also be understood as an invention relating to a storage medium storing a program for causing a computer to execute each step of each device or method of the apparatus described here.

According to the present invention, since the virtual identifier usable for data link layer switching can be carried by using the address area and the area for upper layer protocol identification information, the maximum packet length is readjusted and changed. Eliminates the need for Further, in the node or bridge, the Ethernet switch, etc., among the virtual identifiers required for the data link layer switching, it is sufficient to store the information described in the address area, so that the MAC address that needs to be stored can be reduced. .

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of a MAC address format and a data link layer frame (hereinafter abbreviated as MAC frame) format. Address format 101 (Fig. 1 (a)) is a standard MAC address format defined by the IEEE 802 committee, which is 1-bit group identifier (I / G bit), 23-bits vendor identifier, 24-bits.
It is classified into the node identifier of. The first bit of the vendor identifier of 23 bits is called the U / L bit especially in the case of Ethernet, and is set to 0 in the case of global use.

Address format 111 (Fig. 1 (b))
Is a MAC address format newly used for operating the present embodiment based on the address format 101. As the vendor identifier 112, a value understood in advance in the entire network is entered as a value dedicated to cut-through. The MAC received by this vendor identifier 112
It becomes possible for each node to judge whether the frame should be subjected to cut-through transfer or normal datagram transfer.

The node identifier 113 is for identifying the node in each network when performing cut-through transfer, and even if a value is assigned so that it is unique in all LANs (entire network), You may assign a unique value within each LAN. From the point of use, it is sufficient for each LAN like the latter to be unique. That is, each node has
Both the normal node identifier and the node identifier for cut-through will be assigned. One LAN
When all network interfaces in the same vendor (identifier), the cut-through node identifier may have the same value as the normal node identifier.

MAC frame format (Fig. 1 (c))
Shows the frame format used in 802.3 as an example of the MAC frame format defined by the IEEE802 committee. MAC frame 121 is the destination MA
After the C address, the source MAC address, and the 2-octet frame length field, the LLC header identifies the upper layer protocol shown below. For example, in the case of IP datagram, a total of 8 octets encapsulation called LLC / SNAP is used.

MAC frame format (Fig. 1 (d))
Is a DIX format MAC frame defined as Ethernet Version 2 on Ethernet.
IP and others use the MAC frame format shown in Fig. 1 (d) as the default. MAC frame 122 is the destination
After the MAC address and the source MAC address, the upper layer protocol is identified by the 2-octet Type field.

In the case of Ethernet, MAC frame 121 and
In the MAC frame 122, the maximum datagram length (hereinafter referred to as MTU size) that can be used by the upper protocol is different,
1492 bytes for C-frame 121, MAC frame 122
In case of, it becomes 1500 bytes.

MAC frame format 131 (FIG. 1 (e)
) Is a newly defined M for operating the present embodiment.
It is an example of an AC frame format. The MAC frame format used in this embodiment has a destination MAC address 132 and a source MAC address 133, followed by a Flow identifier 13
This is a format in which 4 is inserted, and there are cases where a destination MAC address side conforms to address format 111 and cases where a source MAC address side conforms to address format 111. Here, the destination MAC address or source MAC according to the address format 111
The combination of the address and the Flow identifier 134 will be called a cut-through identifier. The cut-through identifier is an example of a virtual identifier required for data link layer switching.

The Flow identifier is used in combination with the upstream or downstream cut-through node identifier so that the upstream node and the downstream node can uniquely identify the packet flow for which cut-through transfer is desired in the data link layer. is there. In other words, the node that received the frame can know which packet flow the frame belongs to in the data link layer by looking at the Flow identifier included in the frame and the node identifier for cut-through if necessary. The frame can be transferred without analyzing the flow to which the packet belongs by the processing.

Note that general flow identification information used to identify a packet flow at the network layer is unique throughout the network, whereas Fl
The ow identifier is sufficient if the upstream node and the downstream node sharing it can identify the packet flow using it.

Therefore, prior to actually transmitting the frame by cut-through, the cut-through identifier including the Flow identifier and the identification information at the network layer level of the packet flow represented by this are provided between the upstream node and the downstream node. Exchange messages that associate The value of the cut-through identifier may be determined by the upstream node and notified to the downstream node, may be determined by the downstream node and may be notified to the upstream node, or may be determined by the downstream node in response to the request from the upstream node and upstream. You may reply to the node.

The cut-through identifier is set so that the packet flow desired to be cut-through transferred can be uniquely identified at least in each network. When one cut-through node identifier is assigned to one node, it is possible to form a cut-through transfer virtual path used exclusively for each packet flow by the number of Flow identifiers with that node. . The packet flow can be defined by, for example, one of the final destination address, the final destination port, the source address, the source port of the network layer, or any combination thereof.

Regarding the length of the Flow identifier, it is operationally preferable that it has a fixed length in the entire network. A preferable value for the Flow identifier length is the MTU size when transferring a normal datagram and the MTU size in the present embodiment.
MT for datagram transfer using MAC frame
In order to make it possible to make the U size the same for any encapsulation, the encapsulation length used in the Ethernet DIX format MAC frame is 2 octets.

When the Flow identifier length is 2 octets, the number of usable cut-through identifiers is 65536 for each MAC address (cut-through node identifier) newly introduced in this embodiment. That is, by storing (learning) one cut-through MAC address in the Ethernet switch or bridge device with learning function, 65536
It becomes possible to perform data link layer switching for each packet flow of the book.

In consideration of the increase in the number of hosts and routers on the Internet at present, there is a possibility that 65536 cut-through identifiers will be insufficient, but in contrast to this, it is used to identify routers and hosts. This can be dealt with by assigning a plurality of cut-through node identifiers to one device. Even in that case, the amount of MAC addresses to be stored (learned) is the number of assigned cut-through node identifiers.

FIG. 2 shows an example of the configuration of a router device for high-speed transfer using the MAC frame format according to this embodiment. This router device has one or more network connection interfaces 211 to 21N and is connected to the networks 221 to 22N, respectively. The networks 221 to 22N are networks standardized by the IEEE802 committee, and Ethernet (802.3) and Token Ring (802.5) can be considered.

The datagram processing unit 201 performs network layer processing on the packet assembled from the frames received by each of the network interfaces 211 to 21N. That is, it has a mechanism for determining the router or host and the network connection interface to which the packet is to be transmitted next, from the destination information of the datagram such as IP. It should be noted that the router device may be configured by omitting the packet forwarding function of the datagram processing unit.

The cut-through processing unit 202 performs the protocol processing necessary for performing cut-through (data link layer switching) using the MAC frame format according to this embodiment. That is, Fl between adjacent nodes
By exchanging messages including ow identifier and network layer level packet flow identification information, etc., a common recognition is obtained as to which cut-through identifier is used for cut-through transfer for a specific packet flow. Based on this, the next-stage information table 261 described later is set. If necessary, the cut-through MAC address is also stored. The protocol here is FANP (Flow Attribute Notification Proto
A label distribution protocol such as col) or TDP (Tag Distribution Protocol) can be used.

Each network interface 211-21N
The configuration will be described using the network interface 211 as an example. The network interface 211 is
MAC control unit 231, MAC determination unit 241, flow processing unit 251,
And the next-stage information table 261.

The MAC frame control unit 231 performs MAC frame transmission / reception processing, and the normal operation is the MAC of its own device.
Receives MAC frames and broadcast MAC frames addressed to an address. However, in order to receive the MAC frame etc. destined to the group address,
Depending on the settings, other MAC frames can be received.

The MAC judgment unit 241 judges whether or not the MAC frame has the MAC address format newly introduced in the present embodiment, and if it is (cut-through transfer should be performed), it is received. The MAC frame is sent to the flow processing unit 251, and if not (normal network layer transfer is performed), the received MAC frame is sent to the datagram processing unit 201.

In the flow processing unit 251, the cut-through
By searching the next-stage information table 261 based on the MAC address information (only the cut-through node identifier is sufficient) and the Flow identifier existing in the MAC frame, the network connection interface or the next stage to which the frame should be sent next Information such as a cut-through identifier is obtained, the header information of the MAC frame is rewritten if necessary, and the MAC frame is transferred directly (without the datagram processing unit 201) to the obtained network connection interface.

FIG. 3 shows a datagram processing procedure of the router device when a cut-through MAC address is entered in the destination MAC address area. As an example, the network interface 211 to the network interface
Describe the datagram transfer to 21N.

The network interface 211 receives a MAC frame from the network 221. At this time, the MAC control unit 231 executes the MAC frame processing (destination MAC address check, CRC check, etc.) and receives it.
If the destination MAC address of the MAC frame is stored as what should be received by this router, the MAC judgment unit
Send a frame to 241 (S301). That is, the destination MAC address is the normal MAC address of the local device, or the MAC address assigned to the local device for cut-through (cut-through vendor identifier + cut-through node identifier assigned to the local device). If so, the frame is passed to the MAC judgment unit 241. If not, the received frame is discarded (S302).

Prior to this, the cut-through processing unit 202
Assigned to the device for cut-through by
The address is stored in the MAC control unit 231. Also,
If there is an Ethernet switch between the adjacent node and the cut-through processing unit 202 of this router, when the cut-through MAC address is assigned to itself, the cut-through MAC address is sent to the source. The frame entered as the MAC address is sent to the adjacent node. By receiving this frame, the Ethernet switch on the way will receive the MAC for its cut-through.
It stores which output interface a frame whose address is the destination MAC address should be forwarded to.

Further, each node can store the cut-through MAC address of the adjacent node by receiving the frame. Alternatively, a procedure for exchanging the cut-through MAC address between adjacent nodes may be separately defined by an inquiry / response type procedure or a one-way notification procedure.

Upon receiving the frame, the MAC judgment unit 241 checks the vendor identifier of the destination MAC address (S30
3) In the case of the cut-through vendor identifier, the MAC frame is sent to the flow processing unit 251 to perform the cut-through transfer (S305), and otherwise, the datagram processing unit 201 performs the normal network layer transfer. The MAC frame is sent to (S304).

In the flow processing unit 251, the next stage information table
261 to obtain the output network interface to be sent next and the cut-through identifier to be added next from the Flow identifier entered in the MAC frame (S30
Five). Here, although the next-stage information table 261 is searched by the Flow identifier, the cut-through identifier may be searched. In particular, when assigning a plurality of cut-through node identifiers to one node, it is preferable to search by the cut-through identifier.

If the flow processing unit 251 searches the next-stage information table 261 and there is no corresponding entry, the MAC frame is discarded (S306). Therefore, the sending node is notified by the adjacent node that the adjacent node has set the next-stage information table based on the message exchange including the Flow identifier and the packet flow identification information at the network layer level. Then, the packet belonging to the packet flow is transmitted in the form of the MAC frame (131) including the cut-through identifier.
Until the notification, the packet belonging to the packet flow is sent in the form of a normal MAC frame (121 or 122) so that the adjacent node can perform the transfer by the normal datagram processing.

Although the message exchange for the cut-through process is completed between the preceding node and the router, the same message exchange is not completed between the router and the next node (or MA to be forwarded to the next node if no messages have been exchanged)
In order to avoid the C frame being discarded in S306, for example, there are the following three methods.

First, when the message exchange with the preceding node is completed, an entry is created in the next-stage information table with the Flow identifier (or cut-through identifier) as a key, and the output interface column is blank. (Or information indicating the datagram processing section is written in advance), and only the upper layer protocol identification information such as the LLC header is written in the next-stage cut-through identifier field.
If the entry is in this state when the next-stage information table is searched, the MAC frame is passed to the datagram processing unit 201 (the upper layer protocol identification information is used at this time).

Second, when the message exchange with the preceding node is completed, an entry is created in the next-stage information table with the Flow identifier (or cut-through identifier) as a key, and the Flow is processed by the datagram process. The output interface to be sent next and the destination MAC address of the next node are obtained from the final destination network layer address of the packet flow specified by the identifier, and the obtained information and the required LLC header, protocol identifier, etc. This is a method of writing in the column of column cut-through identifier. By doing this, the MAC frame for which the corresponding entry exists in the next-stage information table will proceed to the steps after S307, and even if the message exchange with the next-stage node is not completed, this router device will not Layer switching transfer will be possible.

A third method is to write all the data to the next-stage information table after message exchange is completed in both the previous stage and the next stage, and to pass the frame to the datagram processing unit 201 even if there is no entry. is there. When this method is adopted, for example, the cut-through node identifier 113
An address format that uses, for example, two octets in it for upper layer protocol identification information is newly adopted. Then, when the cut-through MAC frame is received and sent to the datagram processing unit 201, the protocol identification information described at the predetermined position in the cut-through node identifier may be used. Good.

Alternatively, in order to prevent the frame itself including the cut-through vendor identifier from being sent in a state in which the setting for cut-through transfer has been completed up to the intermediate node, the node that is the source of the frame is , After the end-to-end is notified that the message exchange and the next-stage information table setting are completed, the packets belonging to the packet flow are converted to the MAC frame for cut-through and then transmitted (until then). Is converted to a normal frame and sent out).

After the next-stage information is acquired, the flow processing unit
At 251, the destination MAC address of the received frame and the Flow
The identifier is replaced with the acquired next-stage cut-through identifier (S307) and is sent to the acquired output network interface 21N (S308).

Here, the destination MAC address and the Flow identifier are replaced by each interface independently.
This is because the MAC address and Flow identifier can be managed. If the destination MAC address (cut-through MAC address) and the Flow identifier are unique in all networks, the values are the same and there is no need to replace them.

The output network interface 21N may transfer the sent MAC frame as it is.
With the above processing, the datagram can be transferred by the data link layer switching without performing the processing in the datagram processing unit 201.

Here, FIG. 5 shows an example of the configuration of the next-stage information table for acquiring the information element from the cut-through identifier to the next-stage router device or host. The entry of the cut-through identifier 501 may not be necessary depending on the search method, but the cut-through identifier serves as a search key. As described above, the Flow identifier may be used as the search key instead of the cut-through identifier. Output I /
F 502 indicates the network interface to be sent next. The next-stage cut-through identifier 503 is used when the header information of the MAC frame needs to be replaced in order to send the received MAC frame including the cut-through MAC address and the Flow identifier to the next router device or destination host. This is a required information element.

At this time, the MA newly introduced in this embodiment
In the case of a table entry for the next-stage router that does not support C frame (MAC frame for cut-through) or the final destination host, the next-stage cut-through identifier 50
It is preferable to set MAC address and encapsulation information (LLC header, etc.) used for normal datagram transfer to 3. In other words, MAC for cut-through
For nodes that do not support frames, the preceding node sends a normal MAC frame using the normal MAC address and LLC header set in the next-stage information table. As a result, even if the next-stage router or host does not support the MAC frame format of this embodiment, cut-through is possible in this router device. Moreover, if the method of sending this normal MAC frame to the node that needs to send the received frame to the upper layer processing is adopted, the cut-through MAC frame does not include the upper layer protocol identification information. However, the node can operate without problems.

When the address format that uses, for example, 2 octets in the cut-through node identifier 113 for the upper layer protocol identification information is adopted, it is necessary to send the received frame to the upper layer processing (and this). Even if a MAC frame for cut-through is sent to a node, the node can operate without any problem.

FIG. 4 shows a datagram processing procedure of the router device when the cut-through MAC address is written in the source MAC address area. As an example, the datagram transfer from the network interface 211 to the network interface 21N will be described.

The network interface 211 receives a MAC frame from the network 221. At this time, the MAC control unit 231 executes MAC frame processing (destination MAC address check, CRC check, etc.)
If the address is the MAC address of this router device, MAC
The frame is sent to the judgment unit 241 (S401). I.e. normal
Both the MAC frame and the MAC frame for cut-through are sent to the MAC determination unit 241.

When a bridge device with a learning function is present in the network, the bridge device is a normal MAC device.
Assuming that the frame and the MAC frame for cut-through are not distinguished, the MAC address and the output interface are also used for the frame sent by each node in which the cut-through MAC address assigned to the local device is entered as the source MAC address. Will remember (learn) the relationship.

In this case, the source node uses the source MAC address area for cut-through assigned to itself.
I decided to send the frame with the MAC address entered,
Each node is for cut-through of adjacent node as described above
Since the MAC address can be known, for cut-through assigned to the next node in the source MAC address area
You can also enter the MAC address and send the frame.

Upon receiving the frame, the MAC judgment unit 241 checks the vendor identifier of the source MAC address (S
402), if it is a cut-through vendor identifier, it sends a MAC frame to the flow processing unit 251 to perform cut-through transfer (S404), and if not, the datagram processing unit 201 to perform normal network layer transfer. Sends the MAC frame to (S403).

In the flow processing unit 251, the next stage information table
261, the output network interface to be sent next, the cut-through identifier to be added next, and the destination MAC address are obtained from the cut-through identifier entered in the MAC frame (S404). Destination required here
The MAC address is the normal MAC address of the next node. In the case of the method of sending the frame by entering the cut-through MAC address assigned to the next node in the sending source MAC address area, use the cut-through identifier instead of the cut-through identifier.
It is also possible to search the next-stage information table 261 using the Flow identifier.

If the flow processing unit 251 searches the next-stage information table 261 and there is no corresponding entry, the MAC frame is discarded (S405). The method of preventing undesired discard is the same as the case of writing the cut-through MAC address in the destination MAC address area described above.

After the next stage information is acquired, the flow processing unit
In 251 the source MAC address of the received frame and Fl
The ow identifier is replaced with the acquired next-stage cut-through identifier, the destination MAC address is also rewritten (S406), and the result is sent to the acquired output network interface 21N (S40).
7).

The source MAC address and the Flow identifier are replaced here so that the source MAC address and the Flow identifier can be managed independently by each interface. Therefore, the source MAC address (the MAC address for cut-through is used). ) And Flow identifier are unique in all networks, they have the same value, so there is no need to replace them. However, even in that case, the destination MAC address (normal MAC address) is replaced.

The sending network interface 21N may transfer the sent MAC frame as it is.
With the above processing, the datagram can be transferred by the data link layer switching without performing the processing in the datagram processing unit 201.

Here, FIG. 6 shows an example of the configuration of the next-stage information table for acquiring the information element from the cut-through identifier to the next router device or host. The entry of the cut-through identifier 601 may not be necessary depending on the search method, but the cut-through identifier serves as a search key. As described above, the Flow identifier may be used as the search key instead of the cut-through identifier. Output I /
F 602 indicates the next network interface to be sent. The next-stage cut-through identifier 604 is used when the header information of the MAC frame needs to be replaced in order to send the received MAC frame containing the cut-through MAC address and the Flow identifier to the next router device or destination host. This is a required information element. Next MA
The C address 603 indicates the normal MAC address of the router device or host to be sent next, and is the source MAC address.
This is used when the MAC address format newly introduced in this embodiment is used for the address.

The method for coping with the case where the router or host in the next stage does not support the MAC frame format in this embodiment or when the frame received by the node needs to be processed by the upper layer is described above. destination
This is the same as entering the cut-through MAC address in the MAC address area.

In the above-mentioned example, each node determines whether the received MAC frame should be subjected to cut-through transfer or normal datagram transfer according to the cut-through vendor identifier. The U / L bit may be used instead of the through vendor identifier. That is, if the U / L bit is 1 (local address), the one that should be cut-through transferred, 0
If it is (universal address), it is determined that the normal datagram should be transferred. in this case,
The vendor identifier and the node identifier can also be used together to identify the node in each network.

In the procedure described above, all the interfaces (networks) are described as Ethernets that send and receive MAC frames. However, in FIG. 2, the network on the input side or the output side is AT
The present invention can be applied even to virtual connection type networks such as M and frame relay. For example, in the case of ATM network, the cut-through identifier is written in the VPI / VCI field of the cell header.

For example, when a MAC frame is received from the input side interface and the output side interface is ATM, the value of VPI / VCI is entered in the column of the next stage cut-through identifier in FIGS. 5 and 6. It This allows the router to assign a predetermined VPI / VCI value to the output ATM interface simply by referring to the cut-through identifier of the received MAC frame header without referring to the header information such as the destination address of the packet. Packets can be made into cells and transferred. Here, the frame to which the MAC header representing the next-stage router is added may be made into cells, and the received MAC
The packet with the header removed may be converted into cells (adding an encapsulation header if necessary). The present invention is not limited to the above-described embodiments, but can be implemented with various modifications within the technical scope thereof.

[0084]

As described in detail above, according to the present invention,
A virtual identifier that can be used for switching at the data link layer frame level is provided so that there is no need to readjust or change the packet length or to store many data link layer addresses in a node or bridge, an Ethernet switch, etc. It becomes possible to give.

[Brief description of drawings]

FIG. 1 is a diagram showing a normal MAC frame format and a MAC frame format used in this embodiment.

FIG. 2 is a diagram showing a configuration example of a router that processes a MAC frame used in this embodiment.

FIG. 3 is a flowchart showing an operation example of a router when the MAC address format of this embodiment is used for a destination MAC address.

FIG. 4 shows the MAC of the present embodiment as the source MAC address
6 is a flowchart showing an operation example of a router when an address format is used.

FIG. 5 is a diagram showing a table configuration example in the case where the MAC address format of this embodiment is used for a destination MAC address.

FIG. 6 shows the MAC of this embodiment as the source MAC address.
The figure which shows the example of a table structure when using an address format.

[Explanation of symbols]

201 ... Datagram processing unit 202 ... Cut-through processing unit 211-21N ... Network interface 221 to 22N ... Network (LAN) 231 ... MAC processing unit 241 ... MAC determination unit 251 ... Flow processing unit 261 ... Next-stage information table

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-9-172457 (JP, A) JP-A-11-261641 (JP, A) JP-A-10-136016 (JP, A) JP-A-10- 164119 (JP, A) JP-A-8-125692 (JP, A) Yasuhiro Katsube, Kenichi Nagami, Shigeo Matsuzawa, Cell Switch Router Basic Concept and Migration Scenario, IEICE Technical Report, Japan, Electronic Information IEICE, March 15, 1996, IN 95-145, p173-178 (58) Fields investigated (Int.Cl. ⁷ , DB name) H04L 12/46 H04L 12/56 H04L 12/66

Claims (15)

(57) [Claims] 1. A frame to be transferred at a data link layer level, wherein a packet flow to which the frame belongs is identified at a data link layer by using an area defined as an area for recording upper layer protocol identification information. Storing the correspondence between the receiving means for receiving the frame in which the information for carrying out is written, the identifier capable of identifying the packet flow, and the address information of the node at the next stage to which the frame belonging to this packet flow should be transferred. By referring to the storage means and the correspondence relationship stored in the storage means with the information entered in at least the area of the frame received from the preceding node by the receiving means as an identifier, without performing network layer processing. At the data link layer level, the address information of the next node obtained is added to the frame and transferred. Router device characterized in that comprising a feeding means. 2. The receiving means includes means for receiving another frame to be transferred at a network layer level from a node belonging to a certain logical network, and the router device assembles the other frame into a packet, 2. The router device according to claim 1, further comprising a network layer level transfer means for performing a network layer process on the packet, re-framing the packet, and transferring the frame to a node belonging to another logical network. 3. Detecting information from the frame indicating whether or not the address information written in the address area of the frame received by the receiving means includes information assigned exclusively for transfer at the data link layer level. 3. The router device according to claim 2, further comprising means for passing the frame to the data link layer level transfer means or the network layer level transfer means based on the detection result. 4. The storage means stores, as the address information or in addition to the address information, a new identifier that enables the node at the next stage to identify the packet flow at a data link layer. The transfer means writes information based on the new identifier in an area defined as an area for writing upper layer protocol identification information of the frame. 1. The router device according to 1. 5. The storage means stores, as a part of the new identifier, a node identifier assigned to the node at the next stage exclusively for the transfer at the data link layer level, and the transfer means. The router device according to claim 4, wherein the node identifier is written in a destination address area or a transmission source address area of the frame. 6. The storage means stores, as a part of the new identifier, a node identifier assigned to the router device exclusively for transfer at the data link layer level, and the transfer means comprises: 5. The router device according to claim 4, wherein the node identifier is written in the source address area of the frame. 7. The storage means further includes means for storing, as the address information or in addition to the address information, a correspondence relationship with protocol identification information capable of identifying an upper layer protocol of the packet flow, 2. The router device according to claim 1, wherein the transfer means further includes means for writing the protocol identification information in an area defined as an area for writing the upper layer protocol identification information of the frame. 8. The storage means stores, as the address information, an address fixedly assigned to the node at the next stage for transfer at the network layer level. 4. The router device according to 4 or 7. 9. A frame to be transferred at the data link layer level, wherein a packet flow to which the frame belongs is identified at the data link layer by using an area defined as an area for recording upper layer protocol identification information. Storing the correspondence between the receiving means for receiving the frame in which the information for carrying out is written, the identifier capable of identifying the packet flow, and the address information of the node at the next stage to which the frame belonging to this packet flow should be transferred. By performing the network layer processing by referring to the storage means and the correspondence relationship stored in the storage means with the information written in at least the area of the frame received from the preceding node by the reception means as an identifier. The address information of the next-stage node obtained in step 1 is added to at least the destination address area of the frame. Router device characterized by comprising a transfer means of the data link layer level to transfer the frame Te. 10. A means for storing an address including a node identifier assigned to the router device exclusively for the data link layer level transfer, and the receiving means for writing the stored address in a destination address area. 10. The router device according to claim 9, further comprising: a unit that controls to receive the frame. 11. A data link switch which is present between the node at the preceding stage and which routes a frame using a destination address as a key, uses a node identifier assigned to the router device exclusively for the transfer at the data link layer level. 11. The device according to claim 10, further comprising means for transmitting a frame, to which the dedicated address is added to the transmission source address area, toward the preceding node so that the frame can be routed using the address including the key. Router equipment. 12. A frame to be transferred at a data link layer level, wherein a packet flow to which the frame belongs is identified at a data link layer by using an area defined as an area for recording upper layer protocol identification information. Storing the correspondence between the receiving means for receiving the frame in which the information for carrying out is written, the identifier capable of identifying the packet flow, and the address information of the node at the next stage to which the frame belonging to this packet flow should be transferred. Storage means, and information stored in a transmission source address area of the frame received from the preceding node by the reception means and an area defined as an area for writing the upper layer protocol identification information in the storage means as an identifier By referring to the stored correspondence, the next stage obtained without performing the network layer processing The node address information, the router device characterized by by applying the destination address region and a transfer unit of the data link layer level transfer the frame of the frame. 13. The storage means stores, in addition to the address information, a new identifier that enables the node at the next stage to identify the packet flow at a data link layer. 13. The means according to claim 12, further comprising means for writing the new identifier in an area defined as a source address area of the frame and an area for writing upper layer protocol identification information. Router equipment. 14. The storage means stores, as a part of the new identifier, a node identifier assigned to the next-stage node or to the router device exclusively for the data link layer level transfer. 14. The router device according to claim 13, wherein: 15. An identifier capable of identifying a flow to which a packet received from a certain logical network belongs in a data link layer, and a next stage belonging to another logical network to which a data link layer frame of a packet belonging to this flow should be transferred. If the information stored in the address area of the received frame indicates that the frame should be transferred at the data link layer level, then at least one of the frames of the frame is stored. A node at the next stage obtained without performing network layer processing by referring to the stored correspondence relationship using the information written in the area defined as the area for writing the upper layer protocol identification information as an identifier. The frame transfer method characterized by adding the address information of the above to the frame and transferring the frame.