JP2004289716A

JP2004289716A - Data communication system and flow control method

Info

Publication number: JP2004289716A
Application number: JP2003081942A
Authority: JP
Inventors: Tetsuya Yokomoto; 徹哉横本
Original assignee: Fujitsu Telecom Networks Ltd
Current assignee: Fujitsu Telecom Networks Ltd
Priority date: 2003-03-25
Filing date: 2003-03-25
Publication date: 2004-10-14

Abstract

<P>PROBLEM TO BE SOLVED: To effectively use a buffer memory and prevent overflows, in a data communication system including transmission devices having the buffer memory and a flow control method. <P>SOLUTION: The data communication system and flow control method between the transmission devices include a plurality of transmission devices which have a buffer memory 1 for storing data of a frame configuration temporarily and transmitting and receiving them. The transmission device comprises: a means of transmitting a halt frame 6 which transmits a halt frame to an associated transmission device when the volume of data stored in the buffer memory 1 reaches a threshold; a round-trip transmission delay measuring part 5 which measures a round-trip transmission delay time between the device and the associated device by transmitting and receiving a frame for measuring time; and a threshold determining part 7. The threshold of the buffer memory 1 is determined according to round-trip transmission delay time between the transmission devices and a connection transmission speed between the transmission devices. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、ＬＡＮ（ローカルエリアネットワーク）を拡張したＷＡＮ（広域ネットワーク）やＭＡＮ（都市規模ネットワーク）等のネットワークに接続し、バッファメモリを用いてデータを一時的に蓄積して伝送するブリッジやレイヤ２スイッチ等の伝送装置間でフロー制御するデータ通信システム及び伝送装置間のフロー制御方法に関する。
【０００２】
【従来の技術】
複数の端末装置を接続したＬＡＮを拡張したＷＡＮやＭＡＮ等に於いては、バッファメモリを備えたスイッチングハブやブリッジ等の伝送装置を介して、ＩＥＥＥ８０２．３に準拠した可変長フレームとしてデータを伝送するイーサネット（登録商標）等のデータ通信システムが一般的である。又伝送装置は、それぞれ独立同期方式によるクロック信号に従って、フレームのアドレス部の宛先を識別してデータの送受信処理を行うもので、その為に、一時的にデータを蓄積するバッファメモリを備えている。そして、エラーチェックによるエラー発生のフレームや規定長を超えたフレーム等をエラーフレームとして廃棄し、ネットワーク上に無効なデータが伝送されないように制御する機能も備えている。
【０００３】
例えば、図７に示すように、スイッチングハブ，ブリッジ，レイヤ２スイッチ等の伝送装置１００_１〜１００_４が伝送路１０３，１０４，１０５を介して接続され、伝送装置１００_１にはＬＡＮ１０２により複数の端末装置１０１が接続されたデータ通信システムに於いて、各伝送装置１００_１〜１００_４には、前述のように、バッファメモリＢＦを備えている。伝送路１０３，１０４，１０５は、長距離の場合は、例えば、ＦＤＤＩ（ＦｉｂｅｒＤｉｓｔｒｉｂｕｔｅｄＤａｔａＩｎｔｅｒｆａｃｅ）を適用した光伝送路とすることができる。
【０００４】
又ネットワークのエッジ伝送装置間に複数の伝送装置を介して順次伝送することにより長距離のネットワークを構成し、又宛先を識別して出力ポートを選択することにより、メッシュ状のネットワークを構成することができるものであり、各伝送装置１００_１〜１００_４のバッファメモリＢＦは、受信フレームから抽出したクロック信号に従って受信フレームを書込み、自装置のクロック信号に従って読出したフレームの宛先を判定し、その宛先に対応した出力ポートから対向伝送装置又は端末装置へ送出することができる。
【０００５】
このように伝送装置１００_１〜１００_４は、独立同期方式に従ってフレームの送受信を行うものであり、又バッファメモリＢＦの蓄積容量は有限であるから、高トラフィック状態に於いては、バッファメモリＢＦがオーバーフローすることがある。このオーバーフロー状態に於いては、有効なフレームも廃棄されることになり、伝送品質が劣化する。そこで、閾値を設定し、バッファメモリＢＦの蓄積データ量が閾値に達すると、送信側に対して一時停止フレームを送出する。送信側はこの一時停止フレームを受信識別すると、フレームの送信を一時停止して、受信側の伝送装置のバッファメモリのオーバーフローを回避するフロー制御が知られている。
【０００６】
又それぞれバッファメモリを備えた複数のスイッチングハブを階層構造的に接続し、最下位層のスイッチングハブの複数のポートにそれぞれ端末装置を接続し、複数の端末装置をグループ化し、グループ毎の輻輳判断を行い、バッファメモリがオーバーフローする可能性となるような輻輳と判断されたグループに対してのみ輻輳通知を行い、この輻輳通知に含まれるポーズタイムに従って送信側は送信を一時停止するフロー制御を行う手段が知られている（例えば、特許文献１参照）。
【０００７】
【特許文献１】
特開２００２−２２３２２３号公報
【０００８】
【発明が解決しようとする課題】
ＬＡＮ，ＷＡＮ，ＭＡＮ等のネットワークに接続したレイヤ２スイッチ，ブリッジ等の伝送装置に於いては、図７に示すように、バッファメモリＢＦを備えており、このバッファメモリＢＦのオーバーフローが生じないようにフロー制御を行うものである。その場合に、伝送装置１００_１〜１００_４間が数１００ｍ〜数ｋｍ程度の距離の伝送路を介して対向接続されているデータ通信システムに於ける送信側の伝送装置は、受信側の伝送装置からの一時停止フレームを受信識別して、直ちにフレームの送信を一時停止することにより、受信側の伝送装置のバッファメモリのオーバーフローを回避することができる。
【０００９】
しかし、伝送装置１００_１〜１００_４間を数１０ｋｍ以上の光伝送路により接続したデータ通信システムに於いては、受信側の伝送装置から送信側の伝送装置に対して一時停止フレームを送信しても、送信側の伝送装置がこの一時停止フレームを受信するまでに要する時間を無視できないことになり、従って、高速伝送レートの場合には、一時停止フレームを受信識別するまでに多数のフレームを送信するから、受信側の伝送装置のバッファメモリがオーバーフローする問題がある。
【００１０】
そこで、バッファメモリの閾値を低く設定して、蓄積データ量がその閾値に達した時に一時停止フレームを送信することが考えられる。しかし、伝送装置間の伝送路の距離は、それぞれ異なる場合が一般的であるから、一律に閾値を低く設定すると、対向伝送装置間が比較的近距離の場合には、バッファメモリの蓄積容量を有効に利用できない問題が生じる。
【００１１】
本発明は、伝送装置間の距離の遠近に対応してバッファメモリの閾値の設定又は一時停止時間の設定を行って、バッファメモリの蓄積容量の有効利用を図り、同時にオーバーフローを回避することを目的とする。
【００１２】
【課題を解決するための手段】
本発明のデータ通信システムは、図１を参照して説明すると、フレーム構成のデータを一時的に蓄積して送受信する為のバッファメモリ１を有する複数の伝送装置を含むデータ通信システムに於いて、伝送装置は、バッファメモリ１の蓄積データ量が閾値に達した時に一時停止フレームを対向伝送装置に対して送出する一時停止フレーム送信手段６と、対向伝送装置との間の往復伝送遅延時間を時間測定用フレームの送受信により測定する往復伝送遅延測定部５と、往復伝送遅延時間を基にバッファメモリ１の閾値を設定する閾値決定部７とを備えている。
【００１３】
又伝送装置は、バッファメモリ１の蓄積データ量が閾値に達した時に一時停止フレームを対向伝送装置に対して送出する一時停止フレーム送信手段６と、対向伝送装置との間の往復伝送遅延時間を時間測定用フレームの送受信により測定する往復伝送遅延測定部５と、往復伝送遅延時間を基に一時停止フレームに付加して送出する一時停止時間を求める一時停止時間決定部とを備えている。
【００１４】
又往復伝送遅延測定部５は、時間測定用フレームを送信した時刻から、対向伝送装置から折り返し送信された時間測定用フレームを受信した時刻までの時間を往復伝送遅延時間として検出する手段を備えている。又フレームのアドレス部に、時間測定用フレームを示す識別情報を付加し、データ部に、対向伝送装置に対して送信する時に送信又は時間測定の要求を示す情報を付加し、且つ対向伝送装置から返送された時に受信又は時間測定の応答を示す情報を付加した時間測定用フレームを送受信して、対向伝送装置との間の往復伝送遅延時間を測定する手段を備えることができる。
【００１５】
又往復伝送遅延測定部５は、時間測定用フレームを受信識別して、この時間測定用フレームのデータ部の論理を反転して折り返し送信する手段を備えることができる。又時間測定用フレームを受信識別して、この時間測定用フレームのデータ部の時間測定の要求データを、時間測定の応答データに変更して折り返し送信する手段を備えることができる。又対向伝送装置との接続時に送受信する自動交渉用フレームの予約ビット又は未使用ビットを用いて、時間測定用フレームと兼用する手段を備えることができる。
【００１６】
又閾値決定部７は、往復伝送遅延測定部５による対向伝送装置との間の往復伝送遅延時間と、この対向伝送装置との間のコネクション伝送速度とを基に、往復伝送遅延時間及びコネクション伝送速度が大きい程、低い閾値を決定して、バッファメモリ１に対して設定する手段を備えている。
【００１７】
又一時停止時間決定部は、往復伝送遅延測定部５による対向伝送装置との間の往復伝送遅延時間と、この対向伝送装置との間のコネクション伝送速度とを基に、往復伝送遅延時間及びコネクション伝送速度が大きい程、長い一時停止時間を決定して、一時停止フレームに付加する手段を備えている。
【００１８】
又本発明のフロー制御方法は、フレーム構成のデータを一時的にバッファメモリ１に蓄積して伝送装置間で送受信する為のフロー制御方法に於いて、対向伝送装置との間の往復伝送遅延時間を時間測定用フレームの送受信により測定し、この測定した往復伝送遅延時間と、対向伝送装置との間のコネクション伝送速度とを基に、バッファメモリ１の閾値を算出し、このバッファメモリ１の蓄積データ量が閾値に達した時に、対向伝送装置のフレーム送信を一時停止させる為の一時停止フレームを、一時停止フレーム送信手段６を用いて対向伝送装置へ送信する過程を含むものである。
【００１９】
又フレーム構成のデータを一時的にバッファメモリ１に蓄積して伝送装置間で送受信する為のフロー制御方法に於いて、対向伝送装置との間の往復伝送遅延時間を時間測定用フレームの送受信により測定し、この往復伝送遅延時間と、対向伝送装置との間のコネクション伝送速度とを基に、一時停止時間を算出し、バッファメモリ１の蓄積データ量が閾値に達した時に、対向伝送装置のフレーム送信を一時停止させる為の一時停止フレームに、一時停止時間の情報を付加して、対向伝送装置へ送信する過程を含むものである。
【００２０】
又時間測定用フレームは、フレームのアドレス部に時間測定用フレームを示す識別情報を付加し、データ部に対向伝送装置に対して送信する時に送信又は時間測定の要求を示す情報を付加し、且つ対向伝送装置から返送される時に受信又は時間測定の応答を示す情報を付加して送受信し、この時間測定用フレームの送信時刻から受信時刻までの間を往復伝送遅延時間として測定する過程を含むものである。又時間測定用フレームを受信識別し、この時間測定用フレームのデータ部の送信を示す情報の論理を反転して受信を示す情報として折り返し送信する過程を含むことができる。又時間測定用フレームを受信識別し、この時間測定用フレームのデータ部の時間測定の要求データを、時間測定の応答データに変更して折り返し送信する過程を含むことができる。又対向伝送装置との接続時に送受信する自動交渉用フレームの予約ビット又は未使用ビットを用いて、時間測定用フレームとして、対向伝送装置との間の往復伝送遅延時間を測定する過程を含むことができる。
【００２１】
又時間測定用フレームの送受信により測定した対向伝送装置との間の往復伝送遅延時間と、対向伝送装置との間のコネクション伝送速度とを基に、往復伝送遅延時間及びコネクション伝送速度が大きい程、低い閾値を決定して、バッファメモリに対して設定する過程を含むものである。
【００２２】
又時間測定用フレームの送受信により測定した対向伝送装置との間の往復伝送遅延時間と、対向伝送装置との間のコネクション伝送速度とを基に、往復伝送遅延時間及びコネクション伝送速度が大きい程、長い一時停止時間を決定して、一時停止フレームに付加して送信する過程を含むものである。
【００２３】
【発明の実施の形態】
図１は、データ通信システムに於けるブリッジ，レイヤ２スイッチ等の伝送装置の本発明の実施の形態の要部を示すもので、１はバッファメモリ、２はインタフェース部、３は受信キュー、４は送信キュー、５は往復伝送遅延測定部、６は一時停止フレーム送信手段、７は閾値決定部を示す。
【００２４】
バッファメモリ１は、受信キュー３を介したデータフレームを一時的に蓄積し、自装置内のクロック信号に従って読出したデータフレームを送信キュー４に一旦入力する。又バッファメモリ１の蓄積データ量と閾値とを比較し、蓄積データ量が閾値に達すると、一時停止フレーム送信手段６に対して一時停止フレームの送信要求を送出する機能を含むものである。なお、対向伝送装置からの一時停止フレームを受信識別した時は、バッファメモリ１から読出して送信することを一時停止する。停止時間は予め設定することができる。
【００２５】
又インタフェース部２は、対向伝送装置又は端末装置との間のフレームの送受信を行うもので、又対向装置との間のコネクション伝送速度を検出して往復伝送遅延測定部５に通知する機能を含むものである。又往復伝送遅延測定部５は、時間測定用フレームを生成して送信キュー４とインタフェース部２とを介して対向伝送装置に送出し、対向伝送装置から折り返された時間測定用フレームを、インタフェース部２と受信キュー３とを介して受信処理して、対向伝送装置との間の往復伝送遅延時間を測定し、閾値決定部７に対して、測定した往復伝送遅延時間の情報と、コネクションの伝送速度の情報とを転送する。
【００２６】
閾値決定部７は、往復伝送遅延時間が大きい程、バッファメモリ１の閾値を低くし、又コネクションの伝送速度が大きい程、バッファメモリ１の閾値を低くする。即ち、バッファメモリ１に対しては、往復伝送遅延時間が大きい程、一時停止フレームを送出した後の受信データ量が多くなり、又対向伝送装置との間のコネクション伝送速度が大きい程、時間当たりの受信データ量が多くなるから、バッファメモリ１の閾値を低くして、早めに一時停止フレームを送信して、オーバーフローの発生を回避する。このように、バッファメモリ１の閾値を、対向伝送装置との間の距離や伝送速度に対応して自動的に設定することができる。
【００２７】
又往復伝送遅延測定部５からの時間測定用フレームは、例えば、図２に示すフォーマットとすることができる。同図の（Ａ），（Ｂ）は、プリアンブル１１と、開始識別子ＳＦＤ１２と、アドレス部１３と、データ部１４と、エラーチェック部ＣＲＣ１５とを含むフレーム構成を示し、アドレス部１３は、時間測定用専用フレーム識別情報として、他のデータフレームと区別できるようにする。又データ部１４は、（Ａ）に於いては、送信を真（例えば、論理の“１”）、受信を偽（例えば、論理の“０”）として、時間測定用フレームが対向伝送装置に対して送信中のものか、対向伝送装置から折り返し送出したものかを識別可能としている。又（Ｂ）に於いては、データ部１４に、対向伝送装置に対して送信する時に時間測定の要求データ、対向伝送装置から返送された時に、時間測定の応答データを付加する場合を示す。
【００２８】
図２の（Ｃ），（Ｄ）は、既に規格化された対向伝送装置に対するコネクション交渉の為の自動交渉用フレームを示し、（Ｃ）は、１０００ＢＡＳＥ−Ｘ等の１Ｇｂｐｓの伝送速度のネットワークに於ける自動交渉用フレームを示す。このフレームは、１６ビット構成の中のビットＤ０〜Ｄ４，Ｄ９〜Ｄ１１は予約ビットであるから、これらを用いて時間測定用フレームと兼用することができる。又ＮＰ（ＮｅｘｔＰａｇｅ）により、連続したフレームの存在を示すことができるから、この連続したフレームに時間測定用フレームであることを表示して、自動交渉用フレームと兼用することができる。
【００２９】
又図２の（Ｄ）は、１００ＢＡＳＥ−ＴＸ等の１００Ｍｂｐｓの伝送速度のネットワークに於ける自動交渉用フレームを示し、ビットＤ１２が未使用ビットであるから、これを用いて時間測定用フレームとすることができる。この場合、１ビットであるから、前述のように、ビットＤ１５のＮＰを用いて、連続したフレームを付加し、時間測定用フレームと兼用することができる。従って、伝送装置間のコネクション交渉と往復伝送遅延時間測定とを同時に行うことができる。
【００３０】
図３は、往復伝送遅延測定部５（図１参照）の時間測定用フレームの送受信機能の概要を示し、（Ａ）は、送信手段２１と受信手段２２と論理反転部２３とを含み、図示を省略した時間測定用フレーム生成手段からの時間測定用フレームが送信手段２１に入力されると、その時間測定用フレームを図１に於ける送信キュー４に転送し、且つ時間測定用フレーム送信通知信号を図示を省略したタイマ等の時間測定部に転送し、時間の測定を開始させる。
【００３１】
又受信手段２２に於いて、図１に於ける受信キュー３を介して対向伝送装置からの時間測定用フレームを受信した場合は、論理反転部２３に於いて例えば図２の（Ａ）のデータ部１４の送信を示す真（“１”）を、受信を示す偽（“０”）に論理反転して、送信手段２１から折り返して送信する。又対向伝送装置から、フレームのデータ部１４が受信を示す偽として折り返された時間測定用フレームを受信手段２２が受信すると、時間測定用フレームの受信通知信号を前述のタイマ等の時間測定部に転送する。それにより、時間測定用フレームを送信してから折り返して受信するまでの往復伝送遅延時間を測定することができる。
【００３２】
又図３の（Ｂ）は、送信手段３１と受信手段３２とを含み、時間測定用フレーム生成手段から、図２の（Ｂ）に示すフォーマットの時間測定の要求データがフレームのデータ部１４に付加された時間測定用フレームが送信手段３１に転送され、その時間測定用フレームを送出すると共に、タイマ等の時間測定部に時間測定用フレーム送信通知信号を入力して、時間測定を開始させる。又対向伝送装置からの時間測定用フレームを受信し、フレームのデータ部１４に応答データが付加されていれば、時間測定の要求データに対する応答であるから、時間測定用フレーム受信通知信号をタイマ等の時間測定部に転送し、時間測定用フレームを用いた往復伝送遅延時間を測定することができる。又対向伝送装置から時間測定の要求データを付加した時間測定用フレームを受信部３２が識別した時は、送信手段３１から、データ部１５に応答データを付加した時間測定用フレームを送出させる。
【００３３】
図４は、往復伝送遅延測定部と閾値決定部との説明図であり、図１に於ける往復伝送遅延測定部５と、閾値決定部７との機能を示し、４１は時間測定用フレーム送信部、４２は時間測定用フレーム受信部、４３は計数部、４４はコネクション伝送速度通知部、４５は往復伝送遅延測定結果通知部、７１は閾値演算部、７２は閾値設定部を示す。
【００３４】
時間測定用フレーム送信部４１は、送信キュー４（図１参照）を介して時間測定用フレームを送信するもので、図３に於ける送信手段２１，３１の機能に相当し、又時間測定用フレーム受信部４２は、受信キュー３（図１参照）を介して時間測定用フレームを受信するもので、図３に於ける受信手段２２，３２の機能に相当する。そして、時間測定用フレーム送信部４１からの時間測定用フレーム送信通知信号を計数部４３に入力することにより時間測定を開始し、時間測定用フレーム受信部４２からの時間測定用フレーム受信通知信号を計数部４３に入力することにより時間測定を停止するから、時間測定用フレームの往復遅延時間を測定することができる。
【００３５】
又コネクション伝送速度通知部４４は、図１に於けるインタフェース部２からのコネクション伝送速度通知信号を、往復伝送遅延測定結果通知部４５と閾値決定部の閾値演算部７１とに転送する。又往復伝送遅延測定結果通知部４５は、計数部４３に於ける計数値と、コネクション伝送速度通知信号とを基に、所定のビット構成の往復伝送遅延測定結果を閾値演算部７１に転送する。
【００３６】
閾値決定部７の閾値演算部７１は、送信キュー４と受信キュー３との容量を含むバッファメモリ１の容量を表す変数をＢＭＤとし、閾値ＴＨは、

として求めることができる。なお、（１）式に於けるＴＵＤは最大の送信データ量を表す変数、ＴＰＤは一時停止フレームを構成するデータ量を表す変数、ＲＰＤは一時停止フレームを受信して識別する為に要する時間をデータ量に変換した変数、ＲＵＤは一時停止フレームを受信して識別した時点で、送信キューから送信しているフレームの最大データ量を表す変数、ＤＴＶは計数部４３に於ける計数値を表す変数、ＳＰＤはコネクション伝送速度を表す変数を示す。又データ量としては、図２に於けるプリアンプル１１，開始識別子１２及びフレーム間ギャップに相当するデータ量を含むものである。
【００３７】
従って、閾値ＴＨは、対向伝送装置間の往復伝送遅延時間に相当する計数値に対応した変数ＤＴＶと、対向伝送装置間のコネクション伝送速度に対応する変数ＳＰＤとに従って閾値演算部７１に於いて算出される。即ち、対向伝送装置間が長距離で、往復伝送遅延時間が大きい場合に、閾値ＴＨはバッファメモリ１（図１参照）の容量に対して小さい値となる。又コネクション伝送速度が大きい場合も、閾値ＴＨはバッファメモリ１の容量に対して小さい値となる。この算出した閾値ＴＨを閾値設定部７２に通知し、バッファメモリ１（図１参照）に対して、算出した閾値を通知する。又対向伝送装置を変更した時も時間測定用フレームの送受信により往復伝送遅延時間を求め、それを基に閾値を算出して、バッファメモリ１の閾値を更新することができる。又対向伝送装置が一時停止フレームを受信識別してフレームの送信を所定時間停止した後、フレーム送信を再開することになり、それによっても、受信側の伝送装置のバッファメモリ１の蓄積データ量が閾値に達する場合は、再度一時停止フレームを送信することになる。
【００３８】
図５は本発明の他の実施の形態の伝送装置の要部説明図であり、図１と同一符号は同一の機能部分を示し、８は一時停止時間決定部を示す。この一時停止時間決定部８は、往復伝送遅延測定部５からの往復伝送遅延測定結果と、コネクション伝送速度通知信号とを基に、停止フレームに設定する一時停止時間を算出するものである。
【００３９】
又バッファメモリ１の閾値は、予め設定して、その蓄積データ量が閾値に達すると、一時停止フレーム送信手段６に対して一時停止フレーム送信要求を転送する。一時停止フレーム送信手段６は、一時停止時間決定部８からの一時停止時間の情報を、一時停止フレームにを付加して送信キュー４に転送する。対向伝送装置は、この一時停止フレームを受信識別すると、指示された一時停止時間に従ってフレーム送出を一時停止する。従って、一時停止フレームを送信してから対向伝送装置が受信識別するまでの時間が長い場合や伝送速度が大きい場合には、一時停止時間を長くして、受信側の伝送装置のバッファメモリ１のオーバーフローを回避することができる。それにより、フレームの廃棄等が生じないので、伝送品質を改善することができる。
【００４０】
図６は、図５に於ける往復伝送遅延測定部５と一時停止時間決定部８との説明図であり、図４と同一符号は同一機能部分を示し、８１は一時停止時間演算部、８２は一時停止時間通知部を示す。往復伝送遅延測定部５は、図５について説明した場合と同様の動作を行うものであるから、重複した説明は省略する。又一時停止時間決定部８は、一時停止時間演算部８１と一時停止時間通知部８２とを含み、一時停止時間演算部８１は、往復伝送遅延測定結果と、コネクション伝送速度通知信号とに従って、バッファメモリ１の蓄積データ量が閾値に達した時に、対向伝送装置へ通知する一時停止時間を算出する。
【００４１】
この一時停止時間は、送信キュー４と受信キュー３との容量を含むバッファメモリ１（図１参照）の容量を時間に換算して表す変数をＢＭＴすると、一時停止時間ＳＴは、
ＳＴ＝ＢＭＴ−（ＴＵＴ＋ＴＰＴ＋ＲＰＴ＋ＲＵＴ＋ＤＴＶ） …（２）
として求めることができる。なお、（２）式に於けるＴＵＴは最大の送信データ量を時間に換算して表す変数、ＴＰＴは一時停止フレームを構成するデータ量を時間に換算して表す変数、ＲＰＴは一時停止フレームを受信して識別する為に要する時間を表す変数、ＲＵＴは一時停止フレームを受信して識別した時点で、送信キューから送信しているフレームの最大データ量を時間に換算して表す変数、ＤＴＶは計数部４３に於ける計数値を表す変数である。又前述のフレームのデータ量は、プリアンブル１１と開始識別子１２とフレーム間ギャップ等を含めたデータ量である。
【００４２】
算出した一時停止時間ＳＴを、一時停止時間通知部８２に転送すると、この一時停止時間ＳＴを一時停止フレーム送信手段６へ転送する。一時停止フレーム送信手段６は、バッファメモリ１からの一時停止フレーム送信要求に従って生成した一時停止フレームに、一時停止時間ＳＴの情報を付加して送出する。
【００４３】
対向伝送装置は、一時停止フレームを受信識別し、付加された一時停止時間に従った時間、フレームの送信を停止し、一時停止時間経過後に、フレームの送信を再開する。このフレームの送信再開により、受信側の伝送装置のバッファメモリ１の蓄積データ量が閾値に達する場合は、再度一時停止時間の情報を付加した一時停止フレームを送信する。前述のフロー制御により、バッファメモリ１のオーバーフローを回避して、伝送品質を向上することができる。又バッファメモリ１の閾値を予め設定だけではなく、閾値についても往復伝送遅延時間とコネクション伝送速度を基に設定する組み合わせを適用することもできる。
【００４４】
【発明の効果】
以上説明したように、本発明は、対向伝送装置間の往復伝送遅延時間を、時間測定用フレームを用いて測定し、この往復伝送遅延時間と、対向伝送装置との間のコネクション伝送速度とを基に、バッファメモリ１の閾値の設定又は一時停止フレームに付加する一時停止時間の決定を行うもので、各種の伝送距離が混在するデータ通信システムに於いて、その伝送距離及び伝送速度に対応した閾値又は一時停止時間を決定するから、伝送装置のバッファメモリ１の蓄積容量を有効に利用し、且つオーバーフローを防止することができ、インターネットアクセスサービスの高信頼性の確保が可能となる利点がある。
【図面の簡単な説明】
【図１】本発明の実施の形態の伝送装置の要部説明図である。
【図２】時間測定用フレームの説明図である。
【図３】時間測定用フレームの送受信部の概要説明図である。
【図４】往復伝送遅延測定部と閾値決定部との説明図である。
【図５】本発明の他の実施の形態の伝送装置の要部説明図である。
【図６】往復伝送遅延測定部と一時停止時間決定部との説明図である。
【図７】データ通信システムの説明図である。
【符号の説明】
１バッファメモリ
２インタフェース部
３受信キュー
４送信キュー
５往復伝送遅延測定部
６一時停止フレーム送信手段
７閾値決定部
８一時停止時間決定部[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a bridge or layer for connecting to a network such as a WAN (Wide Area Network) or MAN (Urban Scale Network) which is an extension of a LAN (Local Area Network) and temporarily storing and transmitting data using a buffer memory. The present invention relates to a data communication system for performing flow control between transmission devices such as two switches and a flow control method between transmission devices.
[0002]
[Prior art]
In a WAN, MAN, or the like in which a LAN connecting a plurality of terminal devices is extended, data is transmitted as a variable-length frame compliant with IEEE802.3 via a transmission device such as a switching hub or a bridge having a buffer memory. A data communication system such as Ethernet (registered trademark) is generally used. In addition, the transmission device identifies a destination of an address portion of a frame and performs data transmission / reception processing in accordance with a clock signal according to an independent synchronization method, and includes a buffer memory for temporarily storing data. . Further, a function of discarding a frame in which an error occurs due to an error check, a frame exceeding a specified length, or the like as an error frame, and controlling such that invalid data is not transmitted on a network is provided.
[0003]
For example, as shown in FIG. 7, a transmission device 100 such as a switching hub, a bridge, a layer 2 switch, etc. ₁ ~ 100 ₄ Are connected via

transmission lines

103, 104 and 105, and the transmission device 100 ₁ In a data communication system in which a plurality of terminal devices 101 are connected by a LAN 102, each transmission device 100 ₁ ~ 100 ₄ Has the buffer memory BF as described above. In the case of long distances, the

transmission lines

103, 104, and 105 can be optical transmission lines to which, for example, FDDI (Fiber Distributed Data Interface) is applied.
[0004]
In addition, a long-distance network is configured by sequentially transmitting a plurality of transmission devices between edge transmission devices of the network, and a mesh network is configured by identifying a destination and selecting an output port. And each transmission device 100 ₁ ~ 100 ₄ Buffer memory BF writes a received frame in accordance with the clock signal extracted from the received frame, determines the destination of the frame read out in accordance with the clock signal of its own device, and transmits the frame to the opposite transmission device or terminal device from the output port corresponding to the destination. can do.
[0005]
Thus, the transmission device 100 ₁ ~ 100 ₄ Is for transmitting and receiving frames according to the independent synchronization method, and since the storage capacity of the buffer memory BF is finite, the buffer memory BF may overflow in a high traffic state. In this overflow state, valid frames are also discarded, and the transmission quality is degraded. Therefore, a threshold is set, and when the amount of data stored in the buffer memory BF reaches the threshold, a pause frame is transmitted to the transmitting side. When the transmission side identifies the reception of the pause frame, flow control for temporarily stopping the transmission of the frame and avoiding overflow of the buffer memory of the transmission device on the reception side is known.
[0006]
In addition, a plurality of switching hubs each having a buffer memory are connected in a hierarchical structure, terminal devices are connected to a plurality of ports of the lowest-order switching hub, respectively, a plurality of terminal devices are grouped, and congestion determination for each group is performed. Is performed, and congestion notification is performed only for the group determined to be congested such that the buffer memory may overflow, and the transmitting side performs flow control for temporarily stopping transmission according to the pause time included in the congestion notification. Means are known (for example, see Patent Document 1).
[0007]
[Patent Document 1]
JP-A-2002-223223
[0008]
[Problems to be solved by the invention]
A transmission device such as a layer 2 switch or a bridge connected to a network such as a LAN, a WAN, or a MAN includes a buffer memory BF as shown in FIG. 7 so that overflow of the buffer memory BF does not occur. Is to perform flow control. In that case, the transmission device 100 ₁ ~ 100 ₄ A transmission apparatus on the transmission side in a data communication system which is oppositely connected via a transmission path having a distance of about several hundred meters to several kilometers, receives and identifies a pause frame from the transmission apparatus on the reception side, By immediately suspending the transmission of the frame, it is possible to avoid overflow of the buffer memory of the transmission device on the receiving side.
[0009]
However, the transmission device 100 ₁ ~ 100 ₄ In a data communication system in which the transmission frames are connected by an optical transmission path of several tens km or more, even if the transmission-side transmission device transmits a pause frame to the transmission-side transmission device, the transmission-side transmission device does The time required to receive the pause frame cannot be ignored. Therefore, in the case of a high transmission rate, a large number of frames are transmitted until the pause frame is received and identified. There is a problem that the buffer memory overflows.
[0010]
Therefore, it is conceivable to set a low threshold value of the buffer memory and transmit a pause frame when the accumulated data amount reaches the threshold value. However, since the distance of the transmission line between the transmission devices is generally different from each other, if the threshold is set uniformly low, the storage capacity of the buffer memory is reduced when the distance between the opposite transmission devices is relatively short. A problem arises that cannot be used effectively.
[0011]
An object of the present invention is to set a threshold value of a buffer memory or set a pause time in accordance with the distance between transmission devices, thereby effectively utilizing the storage capacity of the buffer memory and simultaneously avoiding overflow. And
[0012]
[Means for Solving the Problems]
The data communication system according to the present invention, which will be described with reference to FIG. 1, is a data communication system including a plurality of transmission devices having a buffer memory 1 for temporarily storing and transmitting data having a frame configuration. The transmission device transmits a pause frame transmitting means 6 for transmitting a pause frame to the opposite transmission device when the amount of data stored in the buffer memory 1 reaches a threshold value, and a round-trip transmission delay time between the opposite transmission device. The system includes a round-trip transmission delay measuring unit 5 for measuring the transmission and reception of the measurement frame, and a threshold determining unit 7 for setting a threshold of the buffer memory 1 based on the round-trip transmission delay time.
[0013]
Further, the transmission apparatus sets a round trip transmission delay time between the pause frame transmitting means 6 for transmitting a pause frame to the opposite transmission apparatus when the amount of data stored in the buffer memory 1 reaches the threshold value and the opposite transmission apparatus. It includes a round trip transmission delay measuring unit 5 for measuring the transmission and reception of the time measurement frame, and a pause time determining unit for calculating a pause time to be transmitted to the pause frame based on the round trip transmission delay time.
[0014]
Further, the round-trip transmission delay measuring section 5 includes means for detecting a time from a time at which the time measurement frame is transmitted to a time at which the time measurement frame transmitted back from the opposite transmission device is received as the round-trip transmission delay time. I have. Also, in the address portion of the frame, identification information indicating a frame for time measurement is added, and in the data portion, information indicating a request for transmission or time measurement when transmitting to the opposite transmission device is added, and from the opposite transmission device, Means may be provided for transmitting and receiving a time measurement frame to which information indicating a response of reception or time measurement has been added when returned, and measuring a round-trip transmission delay time with the opposite transmission device.
[0015]
Further, the round-trip transmission delay measuring section 5 can include means for receiving and identifying the time measurement frame, inverting the logic of the data portion of the time measurement frame, and transmitting it back. Further, it is possible to provide a means for receiving and identifying the time measurement frame, changing the time measurement request data in the data portion of the time measurement frame into time measurement response data, and transmitting it back. Further, it is possible to provide a unit that also serves as a time measurement frame by using a reserved bit or an unused bit of an automatic negotiation frame transmitted and received at the time of connection with the opposite transmission device.
[0016]
Further, the threshold value determining unit 7 determines the round-trip transmission delay time and the connection transmission time based on the round-trip transmission delay time with the opposite transmission device by the round-trip transmission delay measuring unit 5 and the connection transmission speed with the opposite transmission device. There is provided a means for determining a lower threshold value as the speed is higher and setting the threshold value in the buffer memory 1.
[0017]
Further, the pause time determination unit determines the round-trip transmission delay time and the connection based on the round-trip transmission delay time with the opposite transmission device by the round-trip transmission delay measurement unit 5 and the connection transmission speed with the opposite transmission device. Means are provided for determining a longer pause time as the transmission speed is higher, and adding it to the pause frame.
[0018]
The flow control method according to the present invention is a flow control method for temporarily storing frame-structured data in a buffer memory 1 and transmitting / receiving data between transmission apparatuses. Is measured by transmitting and receiving a time measurement frame, and a threshold value of the buffer memory 1 is calculated based on the measured round-trip transmission delay time and the connection transmission speed with the opposite transmission device. When the data amount has reached the threshold value, a step of transmitting a pause frame for temporarily stopping frame transmission of the opposite transmission device to the opposite transmission device using the suspension frame transmission means 6 is included.
[0019]
Also, in a flow control method for temporarily storing frame-structured data in the buffer memory 1 and transmitting and receiving data between the transmission devices, the round-trip transmission delay time between the transmission device and the opposite transmission device is determined by transmitting and receiving the time measurement frame. The pause time is calculated based on the round-trip transmission delay time and the connection transmission speed with the opposite transmission device, and when the amount of data stored in the buffer memory 1 reaches the threshold value, the pause time of the opposite transmission device is calculated. The method includes a step of adding information of a suspension time to a suspension frame for suspending frame transmission and transmitting the information to the opposite transmission apparatus.
[0020]
The time measurement frame has identification information indicating the time measurement frame added to an address portion of the frame, and information indicating a request for transmission or time measurement when transmitted to the opposite transmission device is added to the data portion, and It includes a step of adding and receiving information indicating a response of reception or time measurement when returned from the opposite transmission apparatus, transmitting and receiving, and measuring a round trip transmission delay time from the transmission time to the reception time of the time measurement frame. . Also, the method may include a step of receiving and identifying the time measurement frame, inverting the logic of the information indicating the transmission of the data portion of the time measurement frame, and transmitting the inverted signal as the information indicating the reception. Also, the method may include a step of receiving and identifying the time measurement frame, changing the time measurement request data in the data portion of the time measurement frame into time measurement response data, and transmitting the time measurement frame back. Also, the method may include a step of measuring a round-trip transmission delay time with the opposite transmission device as a time measurement frame by using a reserved bit or an unused bit of an automatic negotiation frame transmitted and received at the time of connection with the opposite transmission device. it can.
[0021]
Also, based on the round-trip transmission delay time to and from the opposite transmission device measured by transmission and reception of the time measurement frame, and the connection transmission speed with the opposite transmission device, the larger the round-trip transmission delay time and connection transmission speed, It involves determining a low threshold value and setting it for the buffer memory.
[0022]
Also, based on the round-trip transmission delay time to and from the opposite transmission device measured by transmission and reception of the time measurement frame, and the connection transmission speed with the opposite transmission device, the larger the round-trip transmission delay time and connection transmission speed, It includes the step of determining a long pause time and adding it to the pause frame and transmitting it.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows a main part of a transmission device such as a bridge and a layer 2 switch in a data communication system according to an embodiment of the present invention, wherein 1 is a buffer memory, 2 is an interface unit, 3 is a reception queue, Indicates a transmission queue, 5 indicates a round-trip transmission delay measuring unit, 6 indicates a pause frame transmitting unit, and 7 indicates a threshold value determining unit.
[0024]
The buffer memory 1 temporarily accumulates the data frame via the reception queue 3 and temporarily inputs the data frame read out according to the clock signal in its own device to the transmission queue 4. Further, it has a function of comparing the amount of data stored in the buffer memory 1 with a threshold value, and sending a request for transmitting a pause frame to the pause frame transmitting means 6 when the amount of stored data reaches the threshold value. When a pause frame from the opposite transmission apparatus is received and identified, reading and transmission from the buffer memory 1 is suspended. The stop time can be set in advance.
[0025]
The interface unit 2 transmits and receives frames to and from the opposite transmission device or the terminal device, and includes a function of detecting a connection transmission speed with the opposite device and notifying the round-trip transmission delay measurement unit 5. It is a thing. The round-trip transmission delay measurement unit 5 generates a time measurement frame and sends it out to the opposing transmission device via the transmission queue 4 and the interface unit 2. The time measurement frame returned from the opposing transmission device is transmitted to the interface unit. 2 and a reception queue 3 to measure the round-trip transmission delay time with the opposite transmission device, and to the threshold determination unit 7, information on the measured round-trip transmission delay time and transmission of the connection Transfer speed information.
[0026]
The threshold value determination unit 7 lowers the threshold value of the buffer memory 1 as the round-trip transmission delay time increases, and lowers the threshold value of the buffer memory 1 as the transmission speed of the connection increases. In other words, for the buffer memory 1, the larger the round-trip transmission delay time, the larger the amount of data received after transmitting the pause frame, and the higher the connection transmission speed with the opposite transmission device, the longer the time per unit time. Therefore, the threshold value of the buffer memory 1 is lowered, and the pause frame is transmitted earlier to avoid overflow. As described above, the threshold value of the buffer memory 1 can be automatically set according to the distance to the opposing transmission device and the transmission speed.
[0027]
The time measurement frame from the round-trip transmission delay measurement unit 5 can have, for example, the format shown in FIG. 3A and 3B show a frame configuration including a preamble 11, a start identifier SFD 12, an address section 13, a data section 14, and an error check section CRC 15, and the address section 13 performs time measurement. Dedicated frame identification information so that it can be distinguished from other data frames. Further, in (A), the data section 14 sets the transmission to true (for example, logic “1”) and the reception to false (for example, logic “0”), and sends the time measurement frame to the opposite transmission device. It is possible to identify whether the data is being transmitted or the data is returned from the opposite transmission device. 3B shows a case where the data section 14 adds time measurement request data when transmitting to the opposing transmission device and time measurement response data when returning from the opposing transmission device.
[0028]
2 (C) and 2 (D) show automatic negotiation frames for connection negotiation with a counterpart transmission device that has already been standardized, and FIG. 2 (C) shows a network with a transmission rate of 1 Gbps such as 1000BASE-X. 2 shows an automatic negotiation frame in the embodiment. In this frame, since bits D0 to D4 and D9 to D11 in the 16-bit configuration are reserved bits, these bits can be used also as a time measurement frame. Also, since the presence of a continuous frame can be indicated by NP (Next Page), it is possible to indicate that the continuous frame is a frame for time measurement and also to use the frame for automatic negotiation.
[0029]
FIG. 2D shows a frame for automatic negotiation in a network with a transmission rate of 100 Mbps such as 100BASE-TX. Since bit D12 is an unused bit, it is used as a time measurement frame. be able to. In this case, since it is one bit, as described above, a continuous frame can be added using the NP of the bit D15, and can also be used as a time measurement frame. Therefore, connection negotiation between transmission devices and round-trip transmission delay time measurement can be performed simultaneously.
[0030]
3A and 3B show an outline of the transmission / reception function of the time measurement frame of the round-trip transmission delay measurement unit 5 (see FIG. 1). FIG. 3A includes a transmission unit 21, a reception unit 22, and a logical inversion unit 23. When the time measurement frame from the time measurement frame generation means is omitted and is input to the transmission means 21, the time measurement frame is transferred to the transmission queue 4 in FIG. The signal is transferred to a time measuring unit such as a timer (not shown) to start measuring time.
[0031]
When the receiving means 22 receives a time measurement frame from the opposite transmission device via the reception queue 3 shown in FIG. 1, the logical inversion unit 23 outputs, for example, the data shown in FIG. The true (“1”) indicating the transmission of the unit 14 is logically inverted to the false (“0”) indicating the reception, and the transmission unit 21 loops back and transmits. Further, when the receiving unit 22 receives the time measurement frame returned from the opposite transmission device as false indicating that the data portion 14 of the frame has been received, the reception notification signal of the time measurement frame is sent to the time measurement unit such as the timer. Forward. This makes it possible to measure the round-trip transmission delay time from the transmission of the time measurement frame to the return and reception.
[0032]
FIG. 3 (B) includes a transmitting means 31 and a receiving means 32. The time measuring request data in the format shown in FIG. 2 (B) is transmitted from the time measuring frame generating means to the frame data section 14. The added frame for time measurement is transferred to the transmission means 31, and the frame for time measurement is transmitted. At the same time, a time measurement frame transmission notification signal, such as a timer, is input to the time measurement unit to start time measurement. If a time measurement frame is received from the opposite transmission device and response data is added to the data portion 14 of the frame, the response to the time measurement request data is received. And the round trip transmission delay time using the time measurement frame can be measured. When the receiving unit 32 identifies the time measurement frame to which the request data for time measurement is added from the opposite transmission device, the transmitting unit 31 causes the data unit 15 to transmit the time measurement frame to which the response data is added.
[0033]
FIG. 4 is an explanatory diagram of a round-trip transmission delay measuring section and a threshold determining section, showing the functions of the round-trip transmission delay measuring section 5 and the threshold determining section 7 in FIG. , 42, a time measurement frame receiving unit, 43, a counting unit, 44, a connection transmission speed notification unit, 45, a round-trip transmission delay measurement result notification unit, 71, a threshold calculation unit, and 72, a threshold setting unit.
[0034]
The time measurement frame transmission unit 41 transmits a time measurement frame via the transmission queue 4 (see FIG. 1), and corresponds to the function of the

transmission units

21 and 31 in FIG. The frame receiving section 42 receives the time measurement frame via the reception queue 3 (see FIG. 1), and corresponds to the function of the receiving means 22, 32 in FIG. The time measurement is started by inputting the time measurement frame transmission notification signal from the time measurement frame transmission unit 41 to the counting unit 43, and the time measurement frame reception notification signal from the time measurement frame reception unit 42 is transmitted. Since the time measurement is stopped by inputting the data to the counting unit 43, the round trip delay time of the time measurement frame can be measured.
[0035]
The connection transmission speed notification unit 44 transfers the connection transmission speed notification signal from the interface unit 2 in FIG. 1 to the round-trip transmission delay measurement result notification unit 45 and the threshold calculation unit 71 of the threshold determination unit. The round-trip transmission delay measurement result notifying section 45 transfers a round-trip transmission delay measurement result having a predetermined bit configuration to the threshold value calculating section 71 based on the count value in the counting section 43 and the connection transmission speed notification signal.
[0036]
The threshold calculator 71 of the threshold determiner 7 sets a variable representing the capacity of the buffer memory 1 including the capacity of the transmission queue 4 and the reception queue 3 to BMD, and the threshold TH is:

Can be sought. In the equation (1), TUD is a variable indicating the maximum amount of transmission data, TPD is a variable indicating the amount of data constituting a pause frame, and RPD is a time required for receiving and identifying the pause frame. The variable converted into the data amount, RUD is a variable representing the maximum data amount of the frame transmitted from the transmission queue when the pause frame is received and identified, and DTV is a variable representing the count value in the counting unit 43. , SPD indicate variables indicating the connection transmission speed. The data amount includes the data amount corresponding to the preamble 11, the start identifier 12, and the inter-frame gap in FIG.
[0037]
Therefore, the threshold value TH is calculated by the threshold value calculating unit 71 in accordance with the variable DTV corresponding to the count value corresponding to the round trip transmission delay time between the opposite transmission devices and the variable SPD corresponding to the connection transmission speed between the opposite transmission devices. Is done. That is, when the distance between the opposite transmission devices is long and the round-trip transmission delay time is long, the threshold value TH is smaller than the capacity of the buffer memory 1 (see FIG. 1). Also, when the connection transmission speed is high, the threshold value TH is a small value with respect to the capacity of the buffer memory 1. The calculated threshold value TH is notified to the threshold value setting unit 72, and the calculated threshold value is notified to the buffer memory 1 (see FIG. 1). Also, when the opposite transmission device is changed, the round trip transmission delay time is obtained by transmitting and receiving the time measurement frame, the threshold value is calculated based on the transmission delay time, and the threshold value of the buffer memory 1 can be updated. Further, after the opposite transmission apparatus has received and identified the paused frame and stopped transmitting the frame for a predetermined time, the transmission of the frame is restarted, which also reduces the amount of data stored in the buffer memory 1 of the transmission apparatus on the receiving side. If the threshold is reached, the pause frame will be transmitted again.
[0038]
FIG. 5 is an explanatory view of a main part of a transmission apparatus according to another embodiment of the present invention, wherein the same reference numerals as those in FIG. 1 indicate the same functional parts, and 8 indicates a pause time determination unit. The temporary stop time determining unit 8 calculates a temporary stop time to be set in the stop frame based on the round trip transmission delay measurement result from the round trip transmission delay measuring unit 5 and the connection transmission speed notification signal.
[0039]
The threshold value of the buffer memory 1 is set in advance, and when the accumulated data amount reaches the threshold value, a pause frame transmission request is transferred to the pause frame transmission means 6. The pause frame transmitting means 6 adds the pause time information from the pause time determination unit 8 to the pause frame and transfers the information to the transmission queue 4. Upon receiving and identifying the pause frame, the opposite transmission device suspends frame transmission according to the instructed pause time. Therefore, when the time from transmission of the pause frame to reception and identification by the opposite transmission device is long or when the transmission speed is high, the pause time is lengthened and the buffer memory 1 of the transmission device on the reception side is extended. Overflow can be avoided. As a result, since the frame is not discarded, the transmission quality can be improved.
[0040]
FIG. 6 is an explanatory diagram of the round-trip transmission delay measuring unit 5 and the pause time determining unit 8 in FIG. 5. The same reference numerals as those in FIG. Indicates a pause time notification unit. The round-trip transmission delay measuring section 5 performs the same operation as that described with reference to FIG. 5, and a duplicate description will be omitted. Further, the pause time determination unit 8 includes a pause time calculation unit 81 and a pause time notification unit 82. The pause time calculation unit 81 performs buffering according to the round trip transmission delay measurement result and the connection transmission speed notification signal. When the amount of data stored in the memory 1 reaches the threshold value, a temporary stop time to be notified to the opposite transmission device is calculated.
[0041]
This pause time is calculated by converting a variable representing the capacity of the buffer memory 1 (see FIG. 1) including the capacity of the transmission queue 4 and the reception queue 3 into time into BMT.
ST = BMT- (TUT + TPT + RPT + RUT + DTV) (2)
Can be sought. In the equation (2), TUT is a variable representing the maximum amount of transmission data in terms of time, TPT is a variable representing the amount of data constituting the pause frame in terms of time, and RPT is a variable representing the pause frame. A variable representing the time required for receiving and identifying, RUT is a variable representing the maximum data amount of the frame transmitted from the transmission queue at the time of receiving and identifying the pause frame, and DTV is representing a variable. It is a variable representing the count value in the counting section 43. The data amount of the above-mentioned frame is a data amount including the preamble 11, the start identifier 12, the gap between frames, and the like.
[0042]
When the calculated pause time ST is transferred to the pause time notification section 82, the pause time ST is transferred to the pause frame transmitting means 6. The pause frame transmitting means 6 transmits the pause frame generated according to the pause frame transmission request from the buffer memory 1 with the information of the pause time ST added thereto.
[0043]
The opposite transmission apparatus receives and identifies the pause frame, stops transmitting the frame for a time according to the added pause time, and resumes the transmission of the frame after the pause time has elapsed. When the amount of data stored in the buffer memory 1 of the transmission device on the receiving side reaches the threshold value due to the restart of the transmission of the frame, the pause frame to which the information of the pause time is added is transmitted again. By the above-described flow control, it is possible to avoid overflow of the buffer memory 1 and improve transmission quality. Not only the threshold value of the buffer memory 1 is set in advance, but also a combination of threshold values based on the round trip transmission delay time and the connection transmission speed can be applied.
[0044]
【The invention's effect】
As described above, the present invention measures the round-trip transmission delay time between the opposite transmission devices using the time measurement frame, and calculates the round-trip transmission delay time and the connection transmission speed between the opposite transmission device. Based on this, the threshold value of the buffer memory 1 is set or the pause time to be added to the pause frame is determined. In a data communication system in which various transmission distances are mixed, the transmission distance and the transmission speed are adjusted. Since the threshold or the suspension time is determined, there is an advantage that the storage capacity of the buffer memory 1 of the transmission device can be effectively used, overflow can be prevented, and high reliability of the Internet access service can be secured. .
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a main part of a transmission device according to an embodiment of the present invention.
FIG. 2 is an explanatory diagram of a time measurement frame.
FIG. 3 is a schematic explanatory diagram of a transmission / reception unit for a time measurement frame.
FIG. 4 is an explanatory diagram of a round-trip transmission delay measurement unit and a threshold value determination unit.
FIG. 5 is an explanatory diagram of a main part of a transmission device according to another embodiment of the present invention.
FIG. 6 is an explanatory diagram of a round-trip transmission delay measurement unit and a suspension time determination unit.
FIG. 7 is an explanatory diagram of a data communication system.
[Explanation of symbols]
1 Buffer memory
2 Interface section
3 Receive queue
4 Transmission queue
5 Round-trip transmission delay measurement unit
6 Pause frame transmission means
7 threshold value determination unit
8 Pause time determination section

Claims

In a data communication system including a plurality of transmission devices having a buffer memory for temporarily storing and transmitting data having a frame configuration,
The transmission device, a pause frame transmitting means for transmitting a pause frame to the opposite transmission device when the amount of data stored in the buffer memory reaches a threshold, and a round-trip transmission delay time between the opposite transmission device A data communication system comprising: a round-trip transmission delay measuring unit for measuring a transmission and reception of a time measurement frame; and a threshold determining unit for setting the threshold of the buffer memory based on the round-trip transmission delay time.

In a data communication system including a plurality of transmission devices having a buffer memory for temporarily storing and transmitting data having a frame configuration,
The transmission device, a pause frame transmitting means for transmitting a pause frame to the opposite transmission device when the amount of data stored in the buffer memory reaches a threshold, and a round-trip transmission delay time between the opposite transmission device A round-trip transmission delay measuring unit that measures the transmission and reception of the time measurement frame; and a pause time determining unit that calculates a pause time to be transmitted to the pause frame based on the round-trip transmission delay time. Characteristic data communication system.

The round-trip transmission delay measuring unit includes means for detecting a time from a time at which a time measurement frame is transmitted to a time at which a time measurement frame transmitted back from the opposite transmission device is received as a round-trip transmission delay time. The data communication system according to claim 1 or 2, wherein:

The round-trip transmission delay measurement unit adds identification information indicating the time measurement frame to an address portion of the frame, and, in a data portion, information indicating a request for transmission or time measurement when transmitting to the opposite transmission device. And transmitting and receiving a time measurement frame to which information indicating a reception or time measurement response has been added when returned from the opposite transmission device, and measures a round-trip transmission delay time with the opposite transmission device. The data communication system according to any one of claims 1 to 3, further comprising means.

5. The apparatus according to claim 1, wherein the round-trip transmission delay measurement unit includes means for receiving and identifying the time measurement frame, inverting the logic of the data portion of the time measurement frame, and transmitting the inverted frame. The data communication system according to claim 1.

The round-trip transmission delay measurement unit includes means for receiving and identifying the time measurement frame, changing the time measurement request data in the data portion of the time measurement frame to time measurement response data, and transmitting the return data. The data communication system according to any one of claims 1 to 4, wherein:

The said round-trip transmission delay measurement part was equipped with the means used also as said time measurement frame using the reserved bit or the unused bit of the frame for automatic negotiations transmitted / received at the time of connection with the opposing transmission apparatus. The data communication system according to any one of claims 1 to 4.

The threshold value determining unit is configured to determine the round-trip transmission delay time and the connection based on a round-trip transmission delay time between the round-trip transmission delay measuring unit and the opposite transmission device and a connection transmission speed with the opposite transmission device. 2. The data communication system according to claim 1, further comprising: means for determining a lower threshold value as the transmission speed increases, and setting the threshold value in the buffer memory.

The temporary stop time determination unit, based on the round trip transmission delay time between the opposite transmission device by the round trip transmission delay measurement unit and the connection transmission speed with the opposite transmission device, the round trip transmission delay time and 3. The data communication system according to claim 2, further comprising: means for determining a longer suspension time as the connection transmission speed is higher, and adding the suspension time to the suspension frame.

In a flow control method for temporarily storing frame configuration data in a buffer memory and transmitting and receiving the data between transmission devices,
A round-trip transmission delay time with the opposite transmission device is measured by transmitting and receiving a time measurement frame, and a threshold value of the buffer memory is set based on the round-trip transmission delay time and a connection transmission speed with the opposite transmission device. Calculating, when the amount of data stored in the buffer memory reaches the threshold value, transmitting a pause frame for temporarily stopping frame transmission of the opposite transmission device to the opposite transmission device. Flow control method.

In a flow control method for temporarily storing frame configuration data in a buffer memory and transmitting and receiving the data between transmission devices,
A round-trip transmission delay time with the opposite transmission device is measured by transmitting and receiving a time measurement frame, and a pause time is calculated based on the round-trip transmission delay time and a connection transmission speed with the opposite transmission device. A step of, when the amount of data stored in the buffer memory reaches a threshold, adding information of the pause time to a pause frame for temporarily stopping frame transmission of the opposite transmission device and transmitting the frame to the opposite transmission device; A flow control method comprising:

The time measurement frame, the identification information indicating the time measurement frame is added to the address portion of the frame, and information indicating a request for transmission or time measurement when transmitting to the opposite transmission device is added to the data portion, and The method includes a step of adding and receiving information indicating a response of reception or time measurement when returned from the opposite transmission device, transmitting and receiving, and measuring a round trip transmission delay time from a transmission time to a reception time of the time measurement frame. The flow control method according to claim 10 or 11, wherein:

13. The method according to claim 10, further comprising the step of receiving and identifying the time measurement frame, inverting the logic of information indicating transmission of a data portion of the time measurement frame, and transmitting the inverted signal as information indicating reception. The flow control method according to claim 1.

11. The method according to claim 10, further comprising a step of receiving and identifying the time measurement frame, changing the time measurement request data in the data portion of the time measurement frame into time measurement response data, and transmitting the time measurement frame back. 13. The flow control method according to claim 12.

As a time measurement frame using a reserved bit or an unused bit of a frame for automatic negotiation transmitted and received at the time of connection with the opposite transmission device, the method includes a step of measuring a round-trip transmission delay time with the opposite transmission device. The flow control method according to claim 10, wherein:

The round-trip transmission delay time and the connection transmission speed based on the round-trip transmission delay time with the opposite transmission device measured by transmission and reception of the time measurement frame and the connection transmission speed with the opposite transmission device. 11. The flow control method according to claim 10, further comprising the step of determining a lower threshold value and setting the lower threshold value in the buffer memory as the value is larger.

The round-trip transmission delay time and the connection transmission speed based on the round-trip transmission delay time with the opposite transmission device measured by transmission and reception of the time measurement frame and the connection transmission speed with the opposite transmission device. 12. The flow control method according to claim 11, further comprising a step of determining a longer pause time as the time is longer, adding the pause time to the pause frame, and transmitting the frame.