JPH08191325A - Packet repeating method for bridge, and bridge - Google Patents

Abstract

PURPOSE: To speedily remove congestion and prevent an unnecessary traffic from being generated if the congestion is caused during a data communication between bridge-connected LANs. CONSTITUTION: The filtering data base of the bridge 3 is provided with a flag field, which is flagged when a transmission source is in a congestion state and cleared when the congestion state of the transmission source is reset. Then packets other than a packet indicating that the congestion state of the transmission source is reset are received by the bridge 3. Then the packet is discarded. Further, the bridge 3 includes a 1st memory 35 which stores the filtering data base having the flag field, a 2nd memory 37 which stores sent and received frames between the LANs, and a control part which sets or clears the flag in the flag field corresponding to the address of the transmission source if the congestion state of the transmission source is reset although the congestion is not removed and judges whether or not the received frames stored in the 2nd memory 37 can be transferred based on the contents of the filtering data base.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is directed to a plurality of local area networks (LAs) interconnected by bridges.
The present invention relates to a bridge relay method and a bridge used therefor when data communication is performed between N) and congestion occurs in a partner station.

[0002]

2. Description of the Related Art In conventional communication between a plurality of LANs,
As shown in FIG. 4, the host computer 11 connected to the LAN 1 and the terminal 21 connected to the LAN 2 may communicate via the bridge 3. Here, as a communication protocol between the host computer and the terminal, a protocol originally developed by the host computer vendor is often used. I as a representative of this
BM's SNA (Systems Network A)
There is a rature. Such a unique protocol is called a host system protocol here. Since the host system protocol is premised on allocating individual lines to each terminal, individual communication does not require control over which route is used for transmission. Therefore, the communication packet does not have the network layer address used for the route setting. Therefore, when connecting a host computer to a LAN using these protocols and further connecting between LANs, a bridge is often used. The bridge relays packets based on the MAC address of each device and does not use the network layer address.

However, recently, in addition to the host type protocol which has been conventionally used, NetBIOS, Network
Non-host protocols such as re and TCP / IP have also been used. For example, in FIG. 4, the host computer 11 is used so as to communicate with the terminal 21 by the host protocol and communicate with the terminal 22 by NetBIOS.

The host system protocol such as SNA is a connection type protocol, and the data link protocol is IEEE802.2 Logical Link C.
control (LLC) Type 2 is used. L
In LC Type 2, when congestion occurs in its own station, RNR (Receive Not Read) shown in FIG.
The packet y) is transmitted to the partner station to which the connection is set. The station receiving the RNR suspends the data packet transmission until the congestion of the partner station is released. For example, in FIG. 4, when the host computer 11 and the terminal 21 set up an LLC connection, when the host computer 11 sends an RNR to the terminal 21, the terminal 21 sends a data packet until it is notified that the congestion is released. To stop sending.

On the other hand, host protocol and NetBIO
When another protocol such as S is used together, when congestion occurs in the host computer 11, the terminal 21 using the host system protocol is notified of the congestion by the RNR packet, but the terminal using NetBIOS. 22 is not notified of the congestion of the host computer 11. Therefore, the terminal 22 continues to send data packets to the host computer 11.

[0006]

In the data communication between the LANs interconnected by the conventional bridge as described above, when the number of terminals communicating with the host computer by other than the host system protocol (that is, non-host system protocol) increases. Since the congestion of the host system protocol is hardly released, there is a problem that the connection time-out occurs in the terminal using the host system protocol and the connection cannot be maintained. In particular, it has been a serious problem for users who attach importance to host-type protocols over other protocols.

Further, since the data packet transmitted by the terminal using the non-host system protocol is not received by the host computer during the congestion, it causes unnecessary traffic on the LAN to which the host computer is connected, and this LAN There was also the problem that other terminals connected to would take away the opportunity to transmit.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and when congestion occurs in data communication between bridge-connected LANs, the congestion is promptly released to generate unnecessary traffic. To prevent this, a flag field is provided in the bridge's filtering database, and when the bridge receives a packet that indicates that the source is congested, the flag field corresponding to the source address of the packet is added to the filtering database. When the bridge receives a packet that sets a flag and indicates that the congestion state of the source has been released, this flag is cleared on the contrary, a packet indicating that the source is in a congestion state and the congestion state of the source Packet that does not correspond to any of the packets indicating that the When the packet is received, the filtering database is checked, and if the flag is set in the flag field corresponding to the destination address of the packet, the packet is discarded, and a packet relay method is provided. It is a thing.

Further, according to the present invention, a first memory for storing a filtering database having a flag field, a second memory for storing a transmission / reception frame between LANs, and congestion or cancellation of congestion at a transmission source. And a control unit that sets or clears a flag in the flag field of the transmission source and determines whether transfer of the received frame stored in the second memory is necessary based on the contents of the filtering database. It provides a bridge to do.

[0010]

The packet that is likely to be discarded by the station having the congestion is discarded by the bridge in advance and is not relayed, so that the traffic to the station having the congestion is reduced and the congestion can be quickly released.

[0011]

Embodiments of the present invention will be described below. FIG. 1 shows a configuration example of a bridge. To connect the bridges to the LAN, each bridge has a LAN controller LANCE3
0, 31, internal buses 32, 33, 34, a bridge operation control unit 36 including a microprocessor and a memory,
It is composed of a buffer memory 37 for storing a reception / transmission frame, signal lines 38, 39 and the like. Also, IEEE
According to the 802.1DMAC Bridges standard, each bridge determines the “source address” and “belonging network name (source station is Stored network name) ”in the filtering table of the bridge. Further, the filtering table as the filtering database of the present invention has a flag field as shown in FIG. Each bridge stores a filtering R that stores a filtering table
Have AM35.

Here, it is assumed that the bridge according to the present invention connects LAN1 and LAN2 as shown in FIG.
The host computer 11 connected to the LAN1 and the terminal 21 connected to the LAN2 communicate by the host system protocol,
The terminal 22 connected to the host computer 11 and LAN2 is N
Communication shall be performed by etBIOS. The bridge is L
All packets flowing through AN1 and LAN2 are received, the filtering table is checked, and if the destination is different from the transmission source LAN, it is relayed, and if it is the same, it is discarded. For example, if the destination of the packet received at the port 301 of the bridge 3 is the terminal 21, it is found from the contents of the filtering table that the terminal 21 is connected to the LAN 2 different from the transmission source LAN 1, and this packet is transmitted to the LAN 2. Relay. On the other hand, if the destination of the packet received at the port 301 of the bridge 3 is the terminal 12, the terminal 12 has the same LAN as the source from the contents of the filtering table.
1 is found to be connected, and this packet is discarded without being relayed.

In the bridge according to the present invention, when receiving a packet and determining whether to relay or drop as described above, at the same time, the RR and RN defined by IEEE 802.2 are simultaneously determined.
Check if it is R or REJ packet. The format of these packets is as shown in FIG. And RNR
When the flag is detected, the flag field of the term in which the transmission source is recorded is set to 1 in the filtering table,
On the contrary, when RR or REJ is detected, 0 is cleared. The bridge discards when the flag field of the item in which the destination of the filtering table is recorded is 1 when determining whether to relay or discard.

For example, in FIG. 1, when congestion occurs in the host computer 11, the host computer 11 sends the RNR to the terminal 21. The bridge 3 sets the flag field of the item recorded by the host computer 11 which is the transmission source of the RNR in the filtering table to 1 and
The R packet is relayed to the LAN 2 to which the destination terminal 21 is connected.

When the terminal 21 receives the RNR, the terminal 21 stops transmitting the data packet to the host computer 11. However,
The RR or RNR packet for monitoring is regularly exchanged between the host computer 11 and the terminal 21 in order to maintain the connection. Therefore, when the received packet is an RR or RNR packet, the bridge 3 relays when the destination is connected to a LAN different from the source even if the flag field of the destination item in the filtering table is 1. To do.

On the other hand, the terminal 22 continues to send data packets to the host computer 11. Then, the port 302 of the bridge 3 receives the packet addressed to the host computer 11. However, the host computer 1 of the filtering table
Since the flag field is set to 1 in the term in which 1 is recorded and it is neither an RR packet nor an RNR packet, the bridge 3 discards this packet.

Next, when the congestion of the host computer 11 is released, the host computer 11 notifies the terminal 21 of RR or REJ.
Send a packet. The bridge 3 clears the flag field of the item recorded by the host computer 11 which is the transmission source of RR or REJ in the filtering table to 0, and this packet is transmitted to the L connected to the destination terminal 21.
Relay to AN2. Then, the data packet addressed to the host computer 11 transmitted from the terminal 22 is sent to the port 3 of the bridge 3.
02 has been received and the flag field of the item recorded by the host computer 11 in the filtering table is 0, the bridge 3 relays this packet to the LAN 1.

[0018]

As described above in detail, according to the packet packet relaying method of the present invention, a flag field is provided in the bridge filtering database (FDB), and the bridge is IEEE802.2 LLC Type.
When the RNR of 2 is detected, the flag of the term in which the MAC address of the transmission source is recorded in the FDB is set,
RR or R of IEEE802.2 LLC Type2
Conversely, when detecting an EJ, the flag is cleared, and the bridge checks the FDB when the received packet is not the RR or RNR packet and discards the packet when the flag is set at the destination of the packet. Therefore, when congestion occurs in data communication between LANs that are bridge-connected, it is possible to quickly release the congestion and prevent generation of unnecessary traffic.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 shows a description example of a filtering table according to the present invention.

[Fig. 3] RR, R defined by IEEE802.2
The formats of NR and REJ packets are shown.

FIG. 4 is a block diagram showing a configuration example of a conventional network system interconnected by a bridge.

[Explanation of symbols]

 11 host computer 12, 13, 21, 22 terminal 30 bridge 301, 302 bridge port 30, 31 LAN controller (LANCE) 32, 33, 34 internal bus 35 filtering table RAM 36 bridge operation control unit 37 buffer memory 38, 39 signal line

Claims (2)

[Claims] 1. A flag field is provided in the filtering database of the bridge, and when the bridge receives a packet indicating that the transmission source is in a congestion state, a flag field corresponding to the address of the transmission source of the packet is set in the filtering database. When the bridge receives a packet that sets the flag and indicates that the congestion status of the source has been released, it reverses this flag,
When the bridge receives a packet that does not correspond to any of the packet indicating that the transmission source is in the congestion state and the packet indicating that the congestion state of the transmission source has been released, the filtering database is checked to check the destination of the packet. A packet relay method, wherein the packet is discarded when the flag is set in a flag field corresponding to an address. 2. A first memory for storing a filtering database having a flag field, a second memory for storing transmission / reception frames between LANs, and a transmission source when congestion occurs or is released at the transmission source. Control unit that sets or clears a flag in the flag field corresponding to the address of 1) and determines whether transfer of the received frame stored in the second memory is necessary based on the contents of the filtering database. Yes, the bridge.