JP2004222106A - Method of detecting and releasing loop generation in lan using spanning tree protocol and relay device - Google Patents

Method of detecting and releasing loop generation in lan using spanning tree protocol and relay device Download PDF

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JP2004222106A
JP2004222106A JP2003009118A JP2003009118A JP2004222106A JP 2004222106 A JP2004222106 A JP 2004222106A JP 2003009118 A JP2003009118 A JP 2003009118A JP 2003009118 A JP2003009118 A JP 2003009118A JP 2004222106 A JP2004222106 A JP 2004222106A
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relay device
loop
lan
transmission path
test frame
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Japanese (ja)
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Masaaki Odaka
雅昭 小▲高▼
Munekazu Hirata
宗和 平田
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Fujitsu Ltd
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Fujitsu Ltd
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Abstract

<P>PROBLEM TO BE SOLVED: To prevent the function down of a network by detecting an abnormality of the network resulting from the occurrence of a loop transmission route in a short time to automatically release the loop transmission route with respect to a method of detecting and releasing loop generation in a LAN (local area network) using spanning tree protocols and a LAN relay device. <P>SOLUTION: A test frame for loop detection is transmitted into a LAN using spanning tree protocols from one relay device 1 in the LAN and is circulated on a loop transmission route, and it is detected whether or not the test frame for loop detection has been returned to and received by the relay device 1 which has transmitted the test frame for loop detection. In the case that the test frame for loop detection has been returned to and received by the relay device 1, the occurrence of a loop transmission route is judged, and connection ports which have received the test frame for loop detection are disconnected. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、スパニングツリープロトコル使用のＬＡＮ（Ｌｏｃａｌ Ａｒｅａ Ｎｅｔｗｏｒｋ）におけるループ発生の検出及び解除方法並びにＬＡＮ中継装置に関し、スパニングツリープロトコルを使用する冗長構成のＬＡＮにおいて、ＬＡＮの伝送経路にループ伝送経路が発生していることを自動検知し、かつ、該ループ伝送経路を自動解除する方法及びＬＡＮ中継装置に関する。
【０００２】
【従来の技術】
ＬＡＮの伝送経路が一筆書きで繋がっていれば、ＬＡＮに接続された通信機器間で種々の通信が可能であるが、ＬＡＮを構成する各中継装置の故障や中継装置間の伝送路の切断などの障害が発生しても、障害箇所を迂回する迂回経路を形成して通信が可能となるよう、ＬＡＮを構成する中継装置間の伝送経路に冗長構成が採られている。
【０００３】
このようなＬＡＮにおいて、冗長構成の伝送路上にループ伝送経路が形成され、パケットフレームが該ループ伝送経路を経由して各中継装置間で繰り返し中継され、無限ループ動作状態に陥るという現象が発生する。このような現象を防ぐために、ループ伝送経路の発生を検出し、該ループ伝送経路の論理的な接続ポートの少なくとも一つを切断して、ループ伝送経路の中継経路を断つためのプロトコルがスパニングツリープロトコルである。
【０００４】
いま、図２の（ａ）に示すように、ＬＡＮを構成する中継装置１、中継装置２、中継装置３がループ状に伝送路で接続されている場合、中継装置１、中継装置２、中継装置３はそれぞれ、該ループ伝送路上にパケットフレームを無限に中継し続け、同一のパケットフレームがＬＡＮ上に永久に周回し、トラフィック負荷が増大してネットワークの機能がダウンしてしまう。
【０００５】
これを防ぐため、図２（ｂ）に示すように、ループ伝送経路を形成する１つのリンク、例えば、中継装置２と中継装置３との間の接続ポートを論理的にブロックすることにより、中継装置２と中継装置３との間の論理的な接続路を遮断してＬＡＮのループ伝送経路を切断する。このループ伝送経路を検出し、論理的にループ伝送経路を切断するプロトコルがスパニングツリープロトコルである。なお、図において、論理的にブロックされた状態の接続ポートを点線で表している。
【０００６】
スパニングツリープロトコルでは、図３（ａ）に示すように、ルートブリッジの中継装置１からＢＰＤＵ（ブリッジプロトコルデータユニット）というフレームを定期的に送信し、下流の中継装置２、中継装置３は、該ＢＰＤＵフレームを受信すると、上流の伝送路又は中継装置に異常がないかを常に確認する。
【０００７】
なお、中継装置２と中継装置３との接続ポートが論理的にブロックされていても、ＢＰＤＵフレームは中継装置２と中継装置３との間で物理伝送路を通して伝達される。下流の中継装置２、中継装置３は、上流の伝送路又は中継装置からのＢＰＤＵフレームの受信が途切れた場合、上流の伝送路又は中継装置が異常であると判断し、該上流からの中継経路を他の中継経路に切り替える。
【０００８】
例えば、図３（ｂ）に示すように、中継装置２において上流の中継装置１からのＢＰＤＵフレームの受信が途切れたことを検知すると、中継装置２は、中継装置１との中継経路を、中継装置３との中継経路に切り替える。
【０００９】
このように自動的にループ状伝送経路を検出し、論理的に該ループ状伝送経路を切断し、また、上流の伝送路又は中継装置の異常を検出して迂回中継経路に切り替えるためのスパニングツリープロトコル及びＢＰＤＵフレームについては下記の非特許文献１等に記載されている。
【非特許文献１】
日経コミュニケーション編集「２００１年版 通信・ネットワーク用語ハンドブック」日経ＢＰ社、２００１年３月２３日、ｐ．５４，ｐ．５６２
【００１０】
【発明が解決しようとする課題】
しかしながら、中継装置に以下の（１）〜（３）のような特殊な故障が発生した場合、中継経路の切り替えが適正に行われず、ループ伝送経路が発生する場合がある。
（１）ＢＰＤＵフレームを送信している接続ポートの送信機能のみが故障し、該接続ポートの受信機能が正常な場合、
（２）ＢＰＤＵフレームを受信している接続ポートの受信機能のみが故障し、該接続ポートの送信機能が正常な場合、
（３）中継装置の受信ポートから先におけるスパニングツリープロトコルのＢＰＤＵフレームを中継する機能（スパニングツリープロトコルエンジン）のみが故障し、他の中継装置とのパケットフレーム送受信機能が正常な場合。
【００１１】
例えば、図４（ａ）に示すように、上記（１）又は（２）の故障が中継装置１と中継装置２との間で発生した場合、又は上記（３）の故障が中継装置２で発生した場合、中継装置２は、中継装置１からのＢＰＤＵフレームの受信がないため、中継装置３との接続ポートのブロック状態を解除し、中継装置３とのパケットフレームの送受信を開始するが、中継装置２から中継装置１への接続ポートの送信動作は正常に機能するため、図４（ｂ）に示すように、中継装置１→中継装置２→中継装置３→中継装置１のループ伝送経路が発生し、ネットワークの機能ダウンを招いてしまう。
【００１２】
このようなスパニングツリープロトコル使用のＬＡＮにおけるループ伝送経路を自動検出し、ループ伝送経路を解除する技術はこれまでになく、実際のネットワークの運用において、ループ伝送経路が発生してネットワークの機能ダウンが発生した場合、人手を介してループ伝送経路の発生によるネットワーク機能ダウンの復旧措置を行っていたため、障害切り分け作業等にも時間が掛かるという問題があった。ループ伝送経路の発生によるネットワークの機能ダウンは被害が大きく、復旧に要する時間は最短であることがが要求される。
【００１３】
本発明は、スパニングツリープロトコル使用のＬＡＮにおけるループ伝送経路の発生によるネットワークの異常を短時間で検出し、該ループ伝送経路を自動的に解除することができるループ発生の検出及び解除方法並びにその機能を有する中継装置を提供することを目的とする。
【００１４】
【課題を解決するための手段】
本発明のスパニングツリープロトコル使用のＬＡＮにおけるループ発生の検出及び解除方法は、（１）スパニングツリープロトコル使用のＬＡＮ内の１つの中継装置から、該ＬＡＮ内にループ検出用テストフレームを送信するステップと、該ループ検出用テストフレームがループ伝送経路を周回し、該ループ検出用テストフレームを送信した中継装置に戻って受信されたか否かを検出するステップと、該ループ検出用テストフレームが該中継装置に戻って受信された場合に、ループ伝送経路が発生していると判断し、該ループ検出用フレームを受信した接続ポートを切断するステップと、を含むものである。
【００１５】
また、本発明のスパニングツリープロトコル使用のＬＡＮにおける中継装置は、（２）スパニングツリープロトコル使用のＬＡＮ内にループ検出用テストフレームを送信する手段と、該ループ検出用テストフレームがループ伝送経路を周回し、該中継装置に戻って受信されたか否かを検出する手段と、該ループ検出用テストフレームが該中継装置に戻って受信された場合に、ループ伝送経路が発生していると判断し、該ループ検出用フレームを受信した接続ポートを切断する手段と、を備えたものである。
【００１６】
【発明の実施の形態】
本発明によるループ発生の検出及びその解除を、図１を参照して説明する。ＬＡＮ内の或る一つの中継装置１から、ループ検出用テストフレームを定期的に全接続ポートより送信する。そして、そのループ検出用テストフレームがループ伝送経路を周回して、該中継装置１に戻ってきた場合、中継装置１は、ループ伝送経路が発生していると判断し、該ループ検出用フレームを受信した接続ポートを強制的に切断する。
【００１７】
例えば、図１（ａ）に示すように、中継装置１からループ検出用テストフレームを送信した場合、該ループ検出用テストフレームが、中継装置１→中継装置３→中継装置２→中継装置１のループ伝送経路を周回して戻って来た場合、図１（ｂ）に示すように中継装置１は中継装置２との接続ポートを切断することにより、ループ伝送経路を解除する。
【００１８】
【発明の効果】
以上説明したように、本発明によれば、ＬＡＮ内の中継装置から、ループ検出用テストフレームを送信し、該ループ検出用テストフレームがループ伝送経路を周回して、該中継装置に戻って受信された場合に、該中継装置はループ伝送経路が発生していると判断し、該ループ検出用フレームを受信した接続ポートを強制的に切断することにより、ループ伝送経路の発生によるネットワークの異常を短時間で検出して自動的に中継経路を矯正し、ネットワークの機能ダウンを防ぐことができる。
【図面の簡単な説明】
【図１】本発明によるループ発生の検出及びその解除の説明図である。
【図２】ループ伝送経路の中継経路を断つためのスパニングツリープロトコルの説明図である。
【図３】ＢＰＤＵフレームによる異常検出と中継経路切り替えの説明図である。
【図４】特殊な故障が発生した場合にループ伝送経路が発生する例の説明図である。
【符号の説明】
１，２，３ ＬＡＮを構成する中継装置[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for detecting and canceling the occurrence of a loop in a LAN (Local Area Network) using a spanning tree protocol, and a LAN relay apparatus. In a redundant LAN using a spanning tree protocol, a loop transmission path is included in a LAN transmission path. The present invention relates to a method for automatically detecting the occurrence and automatically canceling the loop transmission path, and a LAN relay device.
[0002]
[Prior art]
If the transmission path of the LAN is connected with a single stroke, various communications can be performed between communication devices connected to the LAN. However, failure of each relay device constituting the LAN, disconnection of the transmission path between the relay devices, and the like. Even if the failure occurs, a redundant configuration is adopted in a transmission path between the relay devices configuring the LAN so that a communication can be performed by forming a bypass route that bypasses the failure location.
[0003]
In such a LAN, a phenomenon occurs in which a loop transmission path is formed on a transmission path having a redundant configuration, and a packet frame is repeatedly relayed between the relay devices via the loop transmission path, resulting in an infinite loop operation state. . In order to prevent such a phenomenon, a protocol for detecting the occurrence of a loop transmission path, disconnecting at least one of the logical connection ports of the loop transmission path, and disconnecting the relay path of the loop transmission path is called a spanning tree. Protocol.
[0004]
Now, as shown in FIG. 2A, when the relay device 1, the relay device 2, and the relay device 3 configuring the LAN are connected by a transmission line in a loop, the relay device 1, the relay device 2, and the relay Each of the devices 3 continuously relays the packet frame on the loop transmission path indefinitely, and the same packet frame circulates forever on the LAN, increasing the traffic load and deteriorating the function of the network.
[0005]
In order to prevent this, as shown in FIG. 2B, one link forming a loop transmission path, for example, a connection port between the relay device 2 and the relay device 3 is logically blocked, so that relaying is performed. The logical connection path between the device 2 and the relay device 3 is cut off to disconnect the loop transmission path of the LAN. A protocol that detects this loop transmission path and logically disconnects the loop transmission path is the spanning tree protocol. In the figure, connection ports in a logically blocked state are indicated by dotted lines.
[0006]
In the spanning tree protocol, as shown in FIG. 3A, a frame called a BPDU (bridge protocol data unit) is periodically transmitted from the relay device 1 of the root bridge, and the downstream relay devices 2 and 3 When the BPDU frame is received, it always checks whether there is any abnormality in the upstream transmission line or the relay device.
[0007]
Note that, even if the connection port between the relay device 2 and the relay device 3 is logically blocked, the BPDU frame is transmitted between the relay device 2 and the relay device 3 through the physical transmission path. When the reception of the BPDU frame from the upstream transmission line or the relay device is interrupted, the downstream relay device 2 and the relay device 3 determine that the upstream transmission line or the relay device is abnormal, and the relay route from the upstream. To another relay route.
[0008]
For example, as illustrated in FIG. 3B, when the relay device 2 detects that the reception of the BPDU frame from the upstream relay device 1 is interrupted, the relay device 2 sets the relay route with the relay device 1 to the relay route. Switch to the relay route with the device 3.
[0009]
As described above, the spanning tree for automatically detecting the loop transmission path, logically disconnecting the loop transmission path, and detecting the abnormality of the upstream transmission path or the relay device and switching to the bypass relay path. The protocol and the BPDU frame are described in the following Non-Patent Document 1 and the like.
[Non-patent document 1]
Edited by Nikkei Communication, "Handbook of Communication and Network Terms in 2001", Nikkei BP, March 23, 2001, p. 54, p. 562
[0010]
[Problems to be solved by the invention]
However, when a special failure such as the following (1) to (3) occurs in the relay apparatus, the switching of the relay path is not performed properly, and a loop transmission path may occur.
(1) If only the transmission function of the connection port transmitting the BPDU frame fails and the reception function of the connection port is normal,
(2) When only the reception function of the connection port receiving the BPDU frame fails and the transmission function of the connection port is normal,
(3) A case where only the function (spanning tree protocol engine) of relaying the BPDU frame of the Spanning Tree Protocol from the receiving port of the relay device breaks down, and the function of transmitting and receiving packet frames with other relay devices is normal.
[0011]
For example, as shown in FIG. 4A, when the failure (1) or (2) occurs between the relay device 1 and the relay device 2, or when the failure (3) occurs in the relay device 2. When this occurs, the relay device 2 releases the blocking state of the connection port with the relay device 3 because there is no reception of the BPDU frame from the relay device 1, and starts transmitting and receiving the packet frame with the relay device 3. Since the transmission operation of the connection port from the relay device 2 to the relay device 1 functions normally, as shown in FIG. 4B, the loop transmission path of the relay device 1 → the relay device 2 → the relay device 3 → the relay device 1 Occurs, and the function of the network is reduced.
[0012]
There has never been a technology to automatically detect a loop transmission path in a LAN using such a spanning tree protocol and release the loop transmission path. In actual network operation, a loop transmission path occurs and network functions are down. When the error occurs, the network function has been restored manually due to the occurrence of a loop transmission path, and thus a problem has arisen in that it takes time to perform a fault isolation operation or the like. Network function down due to the occurrence of the loop transmission path is severely damaged, and it is required that the time required for restoration be as short as possible.
[0013]
The present invention relates to a method for detecting and canceling the occurrence of a loop capable of automatically detecting a network abnormality due to the occurrence of a loop transmission path in a LAN using a spanning tree protocol and automatically releasing the loop transmission path, and a function thereof. It is an object of the present invention to provide a relay device having the following.
[0014]
[Means for Solving the Problems]
The method for detecting and canceling the occurrence of a loop in a LAN using the spanning tree protocol according to the present invention includes the steps of (1) transmitting a loop detection test frame into the LAN from one relay device in the LAN using the spanning tree protocol; Detecting whether or not the test frame for loop detection circulates around a loop transmission path and returns to the relay device that transmitted the test frame for loop detection to detect whether or not the test frame for loop detection is received by the relay device. And receiving the loop detection frame, and determining that a loop transmission path has occurred, and disconnecting the connection port that has received the loop detection frame.
[0015]
Further, the relay device in the LAN using the spanning tree protocol according to the present invention includes: (2) means for transmitting a loop detection test frame in the LAN using the spanning tree protocol, and the loop detection test frame circulates around the loop transmission path. Means for detecting whether or not the loop frame has been received by returning to the relay device; and determining that a loop transmission path has occurred when the loop detection test frame is received by returning to the relay device. Means for disconnecting the connection port that has received the loop detection frame.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Detection and cancellation of occurrence of a loop according to the present invention will be described with reference to FIG. A test frame for loop detection is periodically transmitted from all connection ports from one relay device 1 in the LAN. Then, when the loop detection test frame circulates around the loop transmission path and returns to the relay device 1, the relay device 1 determines that a loop transmission path has occurred, and transmits the loop detection frame. Forcibly disconnect the received connection port.
[0017]
For example, as shown in FIG. 1A, when a test frame for loop detection is transmitted from the relay device 1, the test frame for loop detection is transmitted from the relay device 1 → the relay device 3 → the relay device 2 → the relay device 1. When returning after looping around the loop transmission path, the relay apparatus 1 releases the loop transmission path by disconnecting the connection port with the relay apparatus 2 as shown in FIG.
[0018]
【The invention's effect】
As described above, according to the present invention, a loop detection test frame is transmitted from a relay device in a LAN, and the loop detection test frame circulates around a loop transmission path and returns to the relay device to receive the test frame. In this case, the relay apparatus determines that a loop transmission path has occurred, and forcibly disconnects the connection port that has received the loop detection frame, thereby causing an abnormality in the network due to the occurrence of the loop transmission path. It is possible to detect in a short time and automatically correct the relay route, thereby preventing the function of the network from being down.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of detection of loop occurrence and its release according to the present invention.
FIG. 2 is an explanatory diagram of a spanning tree protocol for cutting a relay route of a loop transmission route.
FIG. 3 is an explanatory diagram of abnormality detection and relay route switching using a BPDU frame.
FIG. 4 is an explanatory diagram of an example in which a loop transmission path occurs when a special failure occurs.
[Explanation of symbols]
1,2,3 Relay device constituting LAN

Claims (2)

スパニングツリープロトコル使用のＬＡＮ内の１つの中継装置から、該ＬＡＮ内にループ検出用テストフレームを送信するステップと、
該ループ検出用テストフレームがループ伝送経路を周回し、該ループ検出用テストフレームを送信した中継装置に戻って受信されたか否かを検出するステップと、
該ループ検出用テストフレームが該中継装置に戻って受信された場合に、ループ伝送経路が発生していると判断し、該ループ検出用フレームを受信した接続ポートを切断するステップと、
を含むことを特徴とするスパニングツリープロトコル使用のＬＡＮにおけるループ発生の検出及び解除方法。Transmitting a loop detection test frame from one relay device in the LAN using the spanning tree protocol to the LAN;
Detecting whether or not the loop detection test frame circulates around a loop transmission path and is received back to the relay device that transmitted the loop detection test frame;
When the loop detection test frame is received by returning to the relay device, determining that a loop transmission path has occurred, and disconnecting the connection port that has received the loop detection frame;
A method for detecting and canceling the occurrence of a loop in a LAN using a spanning tree protocol, comprising: スパニングツリープロトコル使用のＬＡＮ内にループ検出用テストフレームを送信する手段と、該ループ検出用テストフレームがループ伝送経路を周回し、該中継装置に戻って受信されたか否かを検出する手段と、該ループ検出用テストフレームが該中継装置に戻って受信された場合に、ループ伝送経路が発生していると判断し、該ループ検出用フレームを受信した接続ポートを切断する手段と、を備えたことを特徴とするスパニングツリープロトコル使用のＬＡＮにおける中継装置。Means for transmitting a test frame for loop detection in a LAN using a spanning tree protocol, means for detecting whether the test frame for loop detection circulates a loop transmission path and is returned to the relay device, and Means for determining that a loop transmission path has occurred when the test frame for loop detection is received back to the relay device, and disconnecting the connection port that has received the frame for loop detection. A relay device in a LAN using a spanning tree protocol.
JP2003009118A 2003-01-17 2003-01-17 Method of detecting and releasing loop generation in lan using spanning tree protocol and relay device Pending JP2004222106A (en)

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JP2006352763A (en) * 2005-06-20 2006-12-28 Fujitsu Ltd Apparatus and method for detecting network failure
JP2007235691A (en) * 2006-03-02 2007-09-13 Kddi Corp Loop generating direction judgment system and loop separation system in mac bridge network
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