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38                            游飛龍 環狀線 DCS 光纖骨幹系統設計原則





                                                五、故障收斂時間


                 ෂ፩ӻ୕߰Ϟఊɓ݂ღᓃ(̙ঐ݊ண௪א༩ࢰ)ପ͛dۆෂ፩ӻ୕Ꮠͭуʲ౬ෂ፩༩ࢰא

            ઼ਗ௪౪ண௪dίϤʲ౬ཀ೻ʕdਗ਼ኬߧᔟ͟ϤΈᜄӻ୕ෂ፩ʘՉቱዚཥӻ୕(ԷνБԓ္

            છӻ୕)Ϟ̙ঐஈ׵ᓙৃًٙرdԨආϾԴБછʕːೌج္છΐԓ༶Ъfה˸ෂ፩ӻ୕݂ٙ
            ღʲ౬ࣛගٜટאගટᅂᚤӻ୕ᐄ༶዁Ъf߰મ͜SDHӻ୕Ъމෂ፩৶฀dۆSDHӻ୕ٙʲ

            ౬ࣛගԨʔ৷׵50૩߆(ms)dၣ༩஝ᅼฏʃdۆʲ౬ࣛගฏʃfЇ׵layer2ٙၣ༩ӻ୕ۆԱ

            IEEE 802.1Dܔᙄࣣ༶ЪdՉʕSTPϗᏡڋ֐࠽(defaut)̙ঐ༺Ց50߆dϾRSTPۆ̙ಯˇՑߒ
            2~3߆d຅್Ϥʲ౬ࣛගɰԱၣ༩஝ᅼʿՉண֛ݖ࿴ϾϞהᄣಯdϤ̮ீཀၣ༩ਞᅰண֛(Է

            νjForwarding delayʿhello timeഃ)͵̙ሜ዆Ϥʲ౬ࣛගf

                 Layer2ٙၣ༩ʹ౬ኜ̀඲޴࢙׵IEEE 802.1Dd௰ڋٙ802.1Dܔᙄࣣ݊1998ϋ̈وٙd
            ʔཀd͟׵ၣ༩ண௪ٙҞ஺೯࢝d΢ɽᅀਠה೯࢝ٙண௪Չ஝ࣸԨӚ୕ɓd˲802.1Dසމ

            ܔᙄࣣdԨڢ੶Փ஝ᇍdઓ΢ɽၣ༩ண௪ʮ̡ίணࠇၣ༩ʹ౬ኜࣛdމл̹ఙᓒ̂dேึ

            ޴࢙׵802.1Ddɦ͟׵೯࢝ཀҞ˲802.1DසމܔᙄًࣣٙرɨdʔΝᅀਠගٙၣ༩ண௪ίቇ
            ͜ɪɰϞʔ޴࢙ٙဲᅇf΢ɽᅀה͛ପٙၣ༩ʹ౬ኜί޴࢙׵802.1Dٙਿᓾɨdމ̋஺Չ

            ϗᏡࣛගdึ΢І೯࢝ʔΝٙစၑج˸੶ʷSTP՘֛dڛဧ̔त(Alcatel)೯࢝FSTPdϾܠ߅

            (CISCO)ۆ೯࢝RSTPഃഃdί2004ϋوٙ802.1Dۆਗ਼ܠ߅ٙRSTPॶɝܔᙄࣣʫf
                 IEEE 802.1D (Media Access Control (MAC) Bridges)˴ࠅʫ࢙݊Ⴍ׼ᓒ࢝ዓ՘֛(Spanning

            Tree Protocol dSTP)ʿҞ஺ᓒ࢝ዓ՘֛(RSTP)ٙ༶ЪdSTP՘֛݊஝ᇍί዗ટኜ(Bridge)א݊
            ၣ༩ʹ౬ኜ(Switch) MACᄴɪٙɓ၇ஷৃ༶Ъ՘֛fSTP˴ࠅͦٙ݊ίԴ͜Bridge אSwitch

            ஹટϓၣ༩ࣛdᒒеΪމԴ͜ʯቱ༩ࢰ(Redundant Path)ዚՓϾପ͛৙ਸ਼(Loop)fSTP̙˸ਈ

            ಻ʿᒒеၣ༩৙ਸ਼d౬̩༑Ⴍdί዗ટኜאၣ༩ʹ౬ኜගdίϞ௪͜༩ࢰٙݖ࿴ɨdSTP̙

            ˸ᆽڭίၣ༩ɪٙՇࡈືᓃග̥Ϟఊɓ༩ࢰπίf
                 STP՘֛౤Զəɓࡈೌ৙ਸ਼ٙၣ༩d຅ɓ̨˕౪STP՘֛ٙၣ༩ʹ౬ኜίၣ༩ןᅝʕ೯

            ତϞ৙ਸ਼ًٙرɨd̴ึኺИ(Block)ɓࡈאεࡈʯቱٙၣ༩਽(Port)dSTP՘֛ܵᚃʔᓙήਈ

            ಻Ϥၣ༩d຅೯ତၣ༩ןᅝҷᜊࣛdSTP՘֛ึІਗኺИ(disable)ݔԬၣ༩਽d˸ᒒе፹Ⴌ
            ପ͛fੂБSTP՘֛စၑجٙ዗ટኜא݊ၣ༩ʹ౬ኜึ֛ಂʹ౬ଡ଼࿒ৃࢹdϤଡ଼࿒ৃࢹ၈މ

            BPDU (Bridge Protocol Data Unit)f࣬ኽBPDUٙʫ࢙dவԬՈϞSTP՘֛ٙၣ༩ண௪ਗ਼̙˸

            ˸ዓًഐ࿴ٙ˙όԸІਗܔ࿴ɓࡈೌ৙ਸ਼ٙၣ༩f
                 νɪࠑdᓒ࢝ዓ՘֛˴ࠅٙͦٙ݊ᒒеlayer2ʹ౬ኜٙၣ༩ගପ͛εቱ৙ਸ਼(loop)d߰ၣ

            ༩ʕପ͛ʔ͍੬৙ਸ਼ఱึிϓᄿᅧࠬᅳʿ/אMACᄴෂ፩ʔᖢ֛dԨਗ਼ኬߧၣ༩ෂ፩ʕᓙf

            ᄿᅧࠬᅳ݊ɔ˄ၣ༩ɪה೯͛ٙମ੬ෂ፩ତ൥dܸ݊ɽඎٙᄿᅧ܆̍Цኽəၣ༩᎖ᄱdኬߧ
            ɓছٙ܆̍ೌج͍੬ෂ৔dאਗ਼ிϓၣ༩ʕᓙf߰ၣ༩஝ᅼฏɽ˲௪౪༩ࢰฏεࣛdۆ຅ၣ
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