聯(lián)通MSTP交流

1、上海貝爾阿爾卡特傳輸網(wǎng)絡(luò)部上海貝爾阿爾卡特傳輸網(wǎng)絡(luò)部 MSTP產(chǎn)品與技術(shù)交流產(chǎn)品與技術(shù)交流All rights reserved Jan. 2003, Alcatel Shanghai bell MSTP技術(shù)的發(fā)展技術(shù)的發(fā)展新興的以太網(wǎng)業(yè)務(wù)新興的以太網(wǎng)業(yè)務(wù) 第三代第三代MSTP系統(tǒng)的技術(shù)特征系統(tǒng)的技術(shù)特征 上海貝爾阿爾卡特的第三代上海貝爾阿爾卡特的第三代MSTP產(chǎn)品產(chǎn)品內(nèi)容內(nèi)容All rights reserved Jan. 2003, Alcatel Shanghai bellMSTP技術(shù)的發(fā)展All rights reserved Jan. 2003, Alcatel Shanghai b

2、ellMSTP的發(fā)展的發(fā)展MSTP的提出的提出第一代第一代MSTP第二代第二代MSTP第三代第三代MSTPAll rights reserved Jan. 2003, Alcatel Shanghai bellMSTP的提出的提出為在現(xiàn)有的SDH/SONET構(gòu)架上提供Ethernet/IP/ATM等多業(yè)務(wù)接入技術(shù)上的發(fā)展主要體現(xiàn)在對以太網(wǎng)提供的支持上，包括最初的以太網(wǎng)點到點透傳MSTP，以及當(dāng)前提供以太網(wǎng)二層交換能力的MSTP，直到近來的第三代MSTP在近期TDM業(yè)務(wù)仍為主導(dǎo)的情況下，在步入純IP寬帶城域網(wǎng)之前，選擇All rights reserved Jan. 2003, Alcatel

3、Shanghai bell以太網(wǎng)點到點透傳以太網(wǎng)點到點透傳MSTP(第一代第一代MSTP) MSTP以太網(wǎng)接口的信號直接映射到SDH的虛容器(VC)中，進行點到點傳送以太網(wǎng)透傳租線業(yè)務(wù)業(yè)務(wù)粒度受限于VC，一般最小為2Mbps不能提供不同以太網(wǎng)業(yè)務(wù)的QoS區(qū)分不提供流量控制不提供多個以太網(wǎng)業(yè)務(wù)流的統(tǒng)計復(fù)用和帶寬共享保護完全基于SDH物理層，不提供以太網(wǎng)業(yè)務(wù)層保護All rights reserved Jan. 2003, Alcatel Shanghai bell以太網(wǎng)二層交換以太網(wǎng)二層交換MSTP(第二代第二代MSTP) 一個或多個用戶以太網(wǎng)接口與一個或多個獨立的基于SDH虛容器的點對點鏈路之

4、間，實現(xiàn)基于以太網(wǎng)鏈路層的數(shù)據(jù)幀交換相比第一代MSTP，第二代MSTP主要在帶寬共享方面提供了一定改善提供基于802.3x的流量控制提供多用戶隔離和VLAN劃分支持提供基于STP/RSTP等的以太網(wǎng)業(yè)務(wù)層保護倒換一些以太網(wǎng)二層交換MSTP還支持基于802.1p的優(yōu)先級轉(zhuǎn)發(fā)802.1p只是規(guī)定了在網(wǎng)絡(luò)出現(xiàn)阻塞情況下，設(shè)備能夠按照不同的優(yōu)先級(07)來轉(zhuǎn)發(fā)以太網(wǎng)數(shù)據(jù)，從而使高優(yōu)先級的數(shù)據(jù)丟包較小。業(yè)務(wù)的QoS支持不僅包括丟包率，還包括帶寬、時延、時延抖動等其它指標，因此嚴格上802.1p并不能提供QoS支持 All rights reserved Jan. 2003, Alcatel Shangh

5、ai bell第三代第三代MSTP(1) 第二代MSTP相對第一代MSTP有相當(dāng)?shù)募夹g(shù)提高，包括多用戶/業(yè)務(wù)的帶寬共享和隔離，但其缺點不提供良好QoS支持，無法很好的取代利潤豐厚的租線業(yè)務(wù)基于STP/RSTP的業(yè)務(wù)層保護倒換時間太慢和第一代MSTP一樣，所能提供的業(yè)務(wù)帶寬粒度也受限于VC，一般最小為2MbpsVLAN的4096地址空間使其在核心節(jié)點的擴展能力很受限制，不適合大型城域公網(wǎng)應(yīng)用節(jié)點處在環(huán)上不同位置時，其業(yè)務(wù)的接入是不公平的MAC地址的學(xué)習(xí)/維護以及MAC地址表影響系統(tǒng)性能基于802.3x的流量控制只是針對點到點鏈路多用戶/業(yè)務(wù)的帶寬共享是對本地接口而言，還不能對整個環(huán)業(yè)務(wù)進行共享A

6、ll rights reserved Jan. 2003, Alcatel Shanghai bell第三代第三代MSTP(2)以太網(wǎng)新業(yè)務(wù)的QoS要求進一步推動MSTP向第三代發(fā)展第三代MSTP主要是在以太網(wǎng)和SDH間引入了一個中間智能適配層，來將以太網(wǎng)的業(yè)務(wù)要求適配、映射到SDH通道上All rights reserved Jan. 2003, Alcatel Shanghai bellt城域以太網(wǎng)技術(shù)和相應(yīng)服務(wù)城域以太網(wǎng)技術(shù)和相應(yīng)服務(wù)t以太網(wǎng)技術(shù)基礎(chǔ)以太網(wǎng)技術(shù)基礎(chǔ)tVLAN管理t以太網(wǎng)在SDH上的封裝方式: VCAT, LCAS, GFPt以太網(wǎng)性能監(jiān)測計數(shù)器t阿爾卡特的城域以太網(wǎng)業(yè)務(wù)解

7、決方案阿爾卡特的城域以太網(wǎng)業(yè)務(wù)解決方案 AgendaAll rights reserved Jan. 2003, Alcatel Shanghai bellt 以太網(wǎng)是一種本地網(wǎng)通信技術(shù) (LAN)。通信終端之間可以以 10-100-1000-10000 Mbps 的數(shù)率傳輸。t“共享式以太網(wǎng)共享式以太網(wǎng)” 在此方式下， 連接到同一電纜的通信終端數(shù)目無限制。t“交換式以太網(wǎng)交換式以太網(wǎng)” 每個設(shè)備有一專用電纜連接到數(shù)據(jù)交換機上。t 以太網(wǎng)通信中應(yīng)用的協(xié)議稱之為 CSMA/CD(only Shared). 即 “ Carrier Sense, Multiple Access, Collision

8、 Detect”.tMultiple access means that every station is connected to a single copper wiretCarrier Sense says that before transmitting data, a station checks the wire (power sensing) to see if any other station is already sending somethingtCollision Detection means that if a collision occurs, it is det

9、ected by each interferring station (by different power lavel on the cable). Both station back-off, and try a retransmission at randomly selected later timeOverviewAll rights reserved Jan. 2003, Alcatel Shanghai bellEthernet 802.3BehaviourBus shared by all stationsStations listen to the bus activity

10、before sending a frameDuring first phase of tx, the station checks for collisionIf a collision occurs, then Random delay before retransmissionEfficiency of the CSMA/CD method : 25 % - 60 % according to the frame sizeAll rights reserved Jan. 2003, Alcatel Shanghai bellIEEE 802.3MAC frame structurePRE

11、AMBULEDESTADDRSRCADDRDATAPADSTART OFFRAME DELIMITER10101011Length or TypeCHECKSUM176620-15000-464LLC+dataAll rights reserved Jan. 2003, Alcatel Shanghai bellETH Frame (IEEE 802.3 IETF RFC 894)ETH LAN (frames)HeaderPayload6 6 2 46 - 1500 bytesDASALength/Type4FCSETH V. 2DA: Destination MACSA: Source M

12、ACLength:Lenght up to the CRCLLC/SNAP:802.2 FCS:Frame Check SumAll rights reserved Jan. 2003, Alcatel Shanghai bellEthernet II versus IEEE 802.3DESTADDR6620-15000-464SRCADDRDATAPADCHECKSUMETHERNET II(include LLC)IEEE 802.3 1500DESTADDR6620-15000-464SRCADDRDATAPADCHECKSUM0. 1500The ETH interface supp

13、ort two type of frame .All rights reserved Jan. 2003, Alcatel Shanghai bellLength/Type field of 802.3 Frames如果此字段的值小于或等于maxValidFrame (詳見 4.2.7.1)的數(shù)值,則 Length/Type字段顯示了包括后續(xù)業(yè)務(wù)數(shù)據(jù)的的以太網(wǎng)數(shù)據(jù)幀的幀長度。 (Length interpretation).如果此字段的值大于或等于1536 decimal (0 x0600), 則 Length/Type 字段顯示的是 MAC client protocol的種類 (Type

14、interpretation). 當(dāng)此字段是作為 Type 字段使用時, 必須有相應(yīng)的機制來確保MAC客戶端能正確的處理以太網(wǎng)數(shù)據(jù)幀的業(yè)務(wù)數(shù)據(jù)。All rights reserved Jan. 2003, Alcatel Shanghai bell802.2 sub-layer802.2 services802.2 Logical Link control sub-layer provides the following types of service :Connectionless (LLC type 1) : this service is used in QB3 profileConn

15、ection oriented (LLC type 2)The format of the data link frame is the following :In QB3 protocol suite, DSAP = SSAP = 0 xFE, and the control field can get only UI and TEST valuesDSAPSSAPCONTROLDATA1 byte1 byte1 or 2 bytesAll rights reserved Jan. 2003, Alcatel Shanghai bellEthernet 802.3Address format

16、I/G U/L46 bit AddressI/G = 0 individual = 1 groupU/L = 0 globally administrated = 1 locallyXX XX XX YY YY YY24 bits24 bitsE.g.00:20:60:00:00:01Alcatel Telettra01:80:C2:00:00:14AIIL 1ISsFF:FF:FF:FF:FF:FFBroadcastAll rights reserved Jan. 2003, Alcatel Shanghai bellEthernet 802.3優(yōu)點和缺點優(yōu)點和缺點缺點以太網(wǎng)通信協(xié)議是一不嚴

17、密的通信協(xié)議 (偶然的 CSMA/CD)初始化時, 無法為數(shù)據(jù)幀分配優(yōu)先級以太網(wǎng)最大通信線纜長度為2.5 km (with repeaters)在過載網(wǎng)絡(luò)里，會有大量的沖突存在優(yōu)點以太網(wǎng)協(xié)議算法簡單且有效網(wǎng)絡(luò)安裝快速便捷以太網(wǎng)物理連接使用無源電纜，維護簡單在無過載的以太網(wǎng)網(wǎng)絡(luò)上可達到0延遲All rights reserved Jan. 2003, Alcatel Shanghai bellt共享以太網(wǎng)t Bust Star (Hub)t交換以太網(wǎng)t Ethernet Bridging(橋)t Ethernet SwitchingEthernet 拓撲和建網(wǎng)設(shè)備All rights reser

18、ved Jan. 2003, Alcatel Shanghai bellEthernet Devices - RepeatersRepeaters (shared Ethernet) :用來將碼流從一個網(wǎng)絡(luò)轉(zhuǎn)發(fā)到另一個網(wǎng)絡(luò)上, 使兩個網(wǎng)絡(luò)在邏輯上表現(xiàn)為一個網(wǎng)絡(luò)提供信號放大和必要的信號同步，使之信號能夠傳送更遠的距離Repeater 有一個輸入和一個輸出 Repeaters 必須符合 IEEE 802.3c repeater 標準并使用在半雙工模式的網(wǎng)絡(luò)結(jié)構(gòu)下All rights reserved Jan. 2003, Alcatel Shanghai bellEthernet Devices

19、- HubHub (shared Ethernet) IEEE802.3 Clause 12:用來將兩個或多個單獨的網(wǎng)段連接在一起。所有收發(fā)以太網(wǎng)數(shù)據(jù)幀的終端設(shè)備均處在同一個沖突域里。提供兩個DTE的連接性，并且執(zhí)行恢復(fù)信號振幅，時鐘同步和沖突檢測的基本功能。All rights reserved Jan. 2003, Alcatel Shanghai bellEthernet Devices - BridgesBridges:網(wǎng)橋的主要功能是將兩個單獨的網(wǎng)絡(luò)連接在一起. 特別是網(wǎng)橋可將兩種不同類型的以太網(wǎng)連接在一起，如以太網(wǎng)（Ethernet）和快速以太網(wǎng)（Fast ethernet）網(wǎng)橋偵

20、聽網(wǎng)絡(luò)上所傳輸?shù)乃袛?shù)據(jù)包，并且根據(jù)每個網(wǎng)段來映射相應(yīng)通信結(jié)點的以太網(wǎng)地址，網(wǎng)橋通過這種方式還實現(xiàn)只允許必要的數(shù)據(jù)流通過網(wǎng)橋。大多數(shù)網(wǎng)橋?qū)陕牭降囊蕴W(wǎng)地址記錄下來，并通過建立一張表來維護學(xué)習(xí)到的以太網(wǎng)地址。此過程是網(wǎng)橋自動實現(xiàn)的. 如果在一個穩(wěn)定的網(wǎng)絡(luò)中，如果每個網(wǎng)橋的地址表均在急速增長，那么極有可能是因為網(wǎng)絡(luò)中存在拓撲環(huán).使用生成樹協(xié)議（The Spanning Tree Protocol）通過協(xié)議信令通信可以避免網(wǎng)絡(luò)拓撲成環(huán)，從而避免廣播風(fēng)暴的產(chǎn)生。生成樹協(xié)議是一個軟件通信標準，在IEEE802.1d中有詳細描述。All rights reserved Jan. 2003, Alcate

21、l Shanghai bellEthernet Devices - Switches交換機:交換機實際上是以太網(wǎng)網(wǎng)橋的擴展. 多端口網(wǎng)橋則成為交換機. 每個通信終端有自己的連接直接連接到交換機上，以至于可以以全雙工，全速率方式與交換機通信. 雖然物理連接依然使用共享式傳輸介質(zhì)，但實際通信中物理連接并不互相共享.All rights reserved Jan. 2003, Alcatel Shanghai bellEthernet DevicesSwitched vs. Shared:Reduces TrafficIncreases performanceIn a single collisio

22、n domainIn a single bordcast domainAll rights reserved Jan. 2003, Alcatel Shanghai bellExamples of Ethernet SwitchesGigabit EthernetSwitched EthernetAll rights reserved Jan. 2003, Alcatel Shanghai belltTransparent Bridging: How Ethernet bridging/switching works ?t Auto_Learning(網(wǎng)橋自動記錄它所看到的所有幀的源地址和端口

23、信息)(自學(xué))t Flooding向所有端口轉(zhuǎn)發(fā)(除源端口外)一個目標地址不確定(FFFF)的幀信號,(泛洪)t Filtering(網(wǎng)橋?qū)盘栔幌蚍夏繕说刂返亩丝谵D(zhuǎn)播出去,如果源和目標地址相同,則丟棄該幀)t Forwarding(網(wǎng)橋轉(zhuǎn)發(fā)具有明確目標地址的幀信號)t Aging(MAC地址標中每一條轉(zhuǎn)接地址存活的時間)(老化)Ethernet Transparent Bridging (IEEE 802.1D)All rights reserved Jan. 2003, Alcatel Shanghai bellt A Layer 3 packet retrieve the MAC a

24、ddress of the destination node he wants to send a packet through ARP protocoltwhen a destination MAC address is unknown, the layer 3 packet is broadcasted (L2 broadcast ?) over the network. The destination station answers with a packet containing the destination MAC address which is now known by the

25、 emitting station t Layer 2 switches manage lookup tables for frames forwarding purpose (see illustration in next slides)tPacket are flooded all aver the network =each time an incoming frame with a unicast (or unknown) MAC address has no entry in the lookup table, it is broadcasted to all the other

26、ports tMAC addresses are progressively learned by the switches = the acknoledgment packet allows each switch on the packet route to understand locally the ports it has to “l(fā)ink” together for an incoming MAC addressEthernet Transparent Bridging (IEEE 802.1D)All rights reserved Jan. 2003, Alcatel Shan

27、ghai bellt如果接收幀的目的MAC地址能在MAC地址表里能查詢到的話，數(shù)據(jù)幀可以從某個特定端口轉(zhuǎn)發(fā)出去，否則，數(shù)據(jù)幀將會以廣播到所有端口的方式傳送。tLayer 2 交換機會根據(jù)目的MAC地址來過濾數(shù)據(jù)幀，使之?dāng)?shù)據(jù)幀能從正確的端口轉(zhuǎn)發(fā)。t交換機會略過同一網(wǎng)絡(luò)段里通信結(jié)點的數(shù)據(jù)包轉(zhuǎn)發(fā)tLayer 2 交換機通過超時機制來避免MAC地址表里的地址永久存在tMAC地址表的表項在經(jīng)過沒有更新的一定時間后，會從MAC地址表中將此表項刪除掉Ethernet Transparent Bridging (IEEE 802.1D)IEEE802.1D;IN SWITCH BASE ON MAC ADDR

28、ESS, THE STP ACCORDING WITH IEEE802.1D)All rights reserved Jan. 2003, Alcatel Shanghai bellEthernet bridging: Flooding And LearningABCDEFA-EA-EA-EMAC addr “A” is learned by S1 (port 1)123123132MAC addr “A” is learned by S2 (port 1)MAC addr “A” is learned by S3 (port 1)A-EA-EA-EA-EA-E123A-EMAC addr “

29、A” is learned by S4 (port 3)Until E replies, all the frames sent to E are flooded toward all the Ethernet networkS1S2S3S4All rights reserved Jan. 2003, Alcatel Shanghai bellEthernet Bridging: Learning And ForwardingABCDEFE-AE-AE-AMAC addr “E” is learned by S1 (port 3)123123132MAC addr “E” is learned

30、 by S2 (port 2)E-A123MAC addr “E” is learned by S4 (port 1)From now on, all the frames to A and E will be forwarded to the right path onlyS1S2S3S4All rights reserved Jan. 2003, Alcatel Shanghai bellSpanning Tree Protocol (STP)The flooding mechanism works if the Ethernet bridges are connected in a tr

31、ee topologyAny loopback will result in a broadcast storm(在具有路由回路的情況下,廣播信息可能在次回到源點而今使其在網(wǎng)絡(luò)中無休止的傳播)Networks with a tree topology are not reliableA single failure affects communication (the network is partitioned)The STP protocol is used to “open the loops”(STP 用以在存在回路的網(wǎng)狀網(wǎng)絡(luò)中,阻塞斷開某個端口以消除回路,在樹狀網(wǎng)絡(luò)中其它端口出現(xiàn)故障

32、時,激活某個段口以保持網(wǎng)絡(luò)成樹狀結(jié)構(gòu),用以消除冗余的回路).Some ports are auto- blocked by the Spanning Tree Protocol in order to build a tree active topology over a meshed physical topologyIn case of failures, some ports are unblocked to restore communicationThe STP protocol (defined in IEEE 802.1D-1998) requires long reconfig

33、uration times (minutes) in case of topology changesThe Rapid STP protocol has been defined in IEEE 802.1w and included into IEEE 802.1D-2003 to support fast reconfiguration times (few seconds)802.1D-2003 的協(xié)議中也包含的協(xié)議中也包含R-STPAll rights reserved Jan. 2003, Alcatel Shanghai bellSpanning Tree ProtocolABC

34、DEFA-*A-*A-*123123132A-*A-*A-*A-*A-*123A-*Blocked portsBlocked ports由由STP自動計算確定自動計算確定BLOCK的端口的端口,兩個兩個BLOCK端口之間的通信中斷端口之間的通信中斷All rights reserved Jan. 2003, Alcatel Shanghai bellSpanning Tree Protocol Link FailureABCDEFA-*A-*A-*123123132A-*A-*A-*A-*A-*123A-*Blocked ports當(dāng)原來的線路中斷后當(dāng)原來的線路中斷后,被阻塞的端口由被阻塞的端

35、口由STP自動激活形成通路自動激活形成通路All rights reserved Jan. 2003, Alcatel Shanghai bellSpanning Tree Protocol STP;有不同的STP版本; IEEE802.1D是一種常用的STP版本.STP;在網(wǎng)絡(luò)中選則一個網(wǎng)橋為根網(wǎng)橋作為參考,然后確定到該參考點的可用路徑,STP選擇一個最佳路徑來轉(zhuǎn)發(fā)數(shù)據(jù),冗余路徑回路被阻斷.BPDU(bridge protocol data unit) ;STP會使用到BPDU信息(由各網(wǎng)橋向其它網(wǎng)橋發(fā)出,由各網(wǎng)橋比較接收到的各個BPDU,只轉(zhuǎn)發(fā)最小的BPDU,),BPDU涉及到三個重要信息

36、; - 網(wǎng)橋ID; (= BID)=網(wǎng)橋優(yōu)先級X網(wǎng)橋MAC地址;BID確定具有最小優(yōu)先級的網(wǎng)橋可能選作根網(wǎng)橋,優(yōu)先級的范圍是0-65535, 默認情況下,網(wǎng)橋的優(yōu)先級被設(shè)置為32768或0X8000.(一個橋接收到從各端口來的多個BPDU后,比較將最小BPDU在各端口中發(fā)出) 當(dāng)兩個網(wǎng)橋優(yōu)先級一樣,則MAC地址小的可能選為根網(wǎng)橋. 交換機只使用內(nèi)存的MAC中的某一個MAC作為BID中的MAC地址. - 路徑開銷(COST); 為每兩個交換機端口之間的為一段路徑,設(shè)置一個開銷值,(路徑數(shù)據(jù)速率越高,開銷越小),A交換機到根交換機之間要經(jīng)過多少段路徑,總的路徑開銷值為各段開銷值之和(. - 端口I

37、D; 端口ID與BID相似,端口BID=端口優(yōu)先級X端口號組成,STP的構(gòu)成中,端ID號低的比ID號高的更具有優(yōu)勢,先比教優(yōu)先級,如優(yōu)先級相同,再比較端口號.當(dāng)兩個端口收到的網(wǎng)橋ID和COST一樣,所明兩個端口到根網(wǎng)橋的路徑相同,就要自動阻塞掉一個端口,就比較接收到的兩個端口的ID,接收到的端口ID號大的端口阻塞關(guān)閉. All rights reserved Jan. 2003, Alcatel Shanghai bellSpanning Tree Protocol一個交換機發(fā)出的BPDU內(nèi)容; - 根網(wǎng)橋的ID(該交換機所知道的根網(wǎng)橋ID). - 到根網(wǎng)橋的路徑開銷(發(fā)送BPDU信號的橋到根

38、橋的路徑開銷(COST),每經(jīng)過一端路徑,累加上該段的COST. - 發(fā)送BPDU信號的網(wǎng)橋的ID - 發(fā)送BPDU信號端口的IDAll rights reserved Jan. 2003, Alcatel Shanghai bellSpanning Tree ProtocolSTP的收斂過程;-選舉根網(wǎng)橋;剛開機時,都視自身為根網(wǎng)橋,把自聲的BID放到根網(wǎng)橋中,2S后,接收到其它端口發(fā)來的BPDU信號,進行比較,若接收到的BPDU中的根BPDU和端口ID比自已的大,則不理睬,若接收到的BPDU中的根BPDU和端口ID比自已的小,則用接收到的BID和端口ID替換自己發(fā)送的BPDU信號內(nèi)容.-選

39、舉根端口; 根端口到根網(wǎng)橋的開銷為0;-其它交換機上各端口收到BPDU后,通過比較根路經(jīng)的開銷值,距根橋路徑開銷最小的端口及為根端口.-在網(wǎng)絡(luò)上的每一個物理段上, 選擇標志端口; 兩個標志端口之間處于可轉(zhuǎn)發(fā)的狀態(tài),每個物理段上的兩個端口互向?qū)Ψ桨l(fā)的BPDU信息中,比較到根橋的路徑開銷,路徑開銷小的為端口為標志端口,當(dāng)兩個端口到根橋的路徑一樣,則比較端口ID,小的為標志端口,大的處于阻塞狀態(tài).All rights reserved Jan. 2003, Alcatel Shanghai bellSpanning Tree Protocol端口的幾種狀態(tài);-禁用狀態(tài);(SHUTDOWN),由管理員

40、人工關(guān)閉某個端口-阻塞狀態(tài)(DISABLE);所有橋的端口都以阻塞作為啟動狀態(tài),這是為了防止形成回路,處于阻塞狀態(tài)的端口不能轉(zhuǎn)發(fā)數(shù)據(jù),不能發(fā)BPDU,但可接收BPDU信號.-監(jiān)聽狀態(tài); 阻塞狀態(tài)后轉(zhuǎn)變?yōu)楸O(jiān)聽狀態(tài),處于監(jiān)聽狀態(tài)的端口不能轉(zhuǎn)發(fā)數(shù)據(jù),可以收發(fā)BPDU信號,并選擇根橋,根端口,和標志端口,如果某個端口選舉為非標志端口,則從新返回阻塞狀態(tài).-學(xué)習(xí)狀態(tài); 建立MAC交換表-轉(zhuǎn)發(fā)狀態(tài); 開始轉(zhuǎn)發(fā)數(shù)據(jù).All rights reserved Jan. 2003, Alcatel Shanghai bellSpanning Tree ProtocolSTP所需的時間參數(shù);-HELLO ; 活動端

41、口發(fā)送BPDU所需的時間.-轉(zhuǎn)發(fā)延遲; 監(jiān)聽或?qū)W習(xí)狀態(tài)的持續(xù)時間-最長壽命; BPDU的存儲過期時間.All rights reserved Jan. 2003, Alcatel Shanghai bellSpanning Tree Protocol Port StatesPower onInitializationBlockingStateListeningStateLearningStateForwarding StateDisabledStateEach switch at the initialization time enters the blocking state Discard

42、 frames received from the attached segment Discard frames switched from another port for forwarding No learn station location Reception of BPDU No transmission of BPDU Discard frames received from the attached segment Discard frames switched from another port for forwarding No learn station location

43、 Reception and Process of BPDU Discard frames received from the attached segment Discard frames switched from another port for forwarding Learn station location Reception, Process and Forwarding of BPDU Forward frames received from the attached segment Forward frames switched from another port for f

44、orwarding Learn station location Reception, Process and Forwarding of BPDUActions performed at each STP stateIt waits for the input to go in blocking state until the expiration time, then it moves to Learning StateIt waits for the input to go in blocking state until the expiration time, then it move

45、s to Forwarding StateIt waits for the input to go in blocking state until the expiration time, then it moves to Listening StateA port in Disabled State doesnt participate to the STPProcessing from a STP state to the otherAll rights reserved Jan. 2003, Alcatel Shanghai belltMedia Type: 10/100 Mb/s, 1

46、Gbs, 10Gbs (TBC)t自協(xié)商 Auto negotiationt流量控制 Flow controlEthernet Physical InterfacesAll rights reserved Jan. 2003, Alcatel Shanghai bellAuto negotiationIEEE 802.3:2002 Clause 28 of the ANSI/IEEE Std 802.3Auto negotiation is a flexible mechanism for providing connection interoperability between IEEE 8

47、02.3 device at the highest performance technology available without intervention from a user, manager,Auto negotiation detects the various modes that exist in the device on the other end of the wire and advertises its own abilities to automatically configure the highest performance mode of interoper

48、ationParallel detection function is for the case where only one end of the link supports the auto negotiationAll rights reserved Jan. 2003, Alcatel Shanghai bellAuto negotiation IEEE 802.3:2002 Clause 28 of the ANSI/IEEE Std 802.3Half duplex : Alternat bidirectionnalFull duplex :Point to point commu

49、nicationBetween 2 equipmentsTwo levels :All rights reserved Jan. 2003, Alcatel Shanghai bellAuto negotiation IEEE 802.3:2002 Clause 28 of the ANSI/IEEE Std 802.3Auto negotiation means :Speed resolutionDuplex resolutionPause mode resolutionFor instance100BaseT full duplex 100BaseT half 10BaseT full10

50、BaseT halfAll rights reserved Jan. 2003, Alcatel Shanghai bellEvolution: 10 Gigabit Ethernet IEEE 802.3aeTimelineIEEE 802.3ae Task force (first step in March 1999)first draft discussed in September 200010 Gb/s Ethernet Task Force complete in June 2002Objective: typical Ethernet “price performance”10

51、 x bandwidth with 34x costObjective: connectivity for MAN/WANinterfaces at 1500 nm on SMF; distances up to 40 kmPMD compatible with framing SONET/SDHObjective: “economic” connectivity for LANInterfaces for MMF, VCSEL, wide WDMFull-duplex onlyAll rights reserved Jan. 2003, Alcatel Shanghai bell802.3z

52、 to 802.3ae ComparisonCSMA/ CD + Full DuplexCarrier ExtensionOptical/ Copper MediaLeverage Fibre Channel PMDsReuse 8B/ 10B CodingSupport LAN/MAN distances to 5 kmFull Duplex OnlyThrottle MAC Speed (rate adapt)Optical Media OnlyLeverage OC- 192 PMDs & Create New Optical PMDs From ScratchNew Codin

53、g Schemes (64B/ 66B)Support LAN/MAN distances to 40 km; Provide Direct Attach to SONET/ SDH Gearsource:All rights reserved Jan. 2003, Alcatel Shanghai bellVLAN Bridging (IEEE 802.1Q)洪泛 (i.e. frames with an unknown unicast MAC DA), 組播和廣播幀總是廣播到網(wǎng)絡(luò)里的所有設(shè)備端口而因此導(dǎo)致了網(wǎng)絡(luò)的性能和安全問題同一網(wǎng)絡(luò)里的不同用戶可以被隔離到不同的虛擬局域網(wǎng)里(VLANs)

54、，這樣的不同用戶組是邏輯地工作在不同網(wǎng)絡(luò)里若處在不同VLAN的通信設(shè)備之間需要互相通信時，只有通過上層數(shù)據(jù)設(shè)備才能實現(xiàn)。(e.g. IP routers)VLAN技術(shù)允許不同的物理網(wǎng)絡(luò)劃分為同一個邏輯網(wǎng)段，不同的邏輯網(wǎng)段(Virtual LANs) 屬于不同的廣播域。All rights reserved Jan. 2003, Alcatel Shanghai bellProvider Bridges (IEEE 802.1ad)The nature of Ethernet bridging is not suitable for carrier networks because it doe

55、s not allow segregating the traffic coming from different customersThe VLAN (IEEE 802.1Q) is not enough because it is not possible to ensure that different customers are not using the same VIDVLANs of different customers with the same VID will be managed as the same VLAN in the carrier network (no c

56、ustomer traffic segregation)The S-VLAN (pre-IEEE 802.1ad) allows the service provider to stack another VLAN tag on the frames coming on the UNI such that traffic from different customers is put on different S-VID and thus segregatedIf the customer is sending untagged Ethernet frames, these are sent

57、toward the carrier network as a single S-VLAN tagged framesIf the customer is sending Q-VLAN tagged Ethernet frames, these are sent toward the carrier network as dual tagged framesAll rights reserved Jan. 2003, Alcatel Shanghai bellObjective of VLAN stackingEnhance the existing Ethernet switching te

58、chnology (based on IEEE 802.1Q VLAN) to provide Metro Ethernet servicesThe existing Ethernet technology is not enough to satisfy carrier-grade requirementsIt is not able to provide the segregation of traffic from different customersThe ranges of VLANs used by different customers can overlap so using

59、 the 802.1Q VLAN tag (Q-VLAN) is not enoughIt is not able to provide carrier-grade QoS capabilitiesThe existing Ethernet technology can be simply enhanced with a new Service Provider VLAN tag (S-VLAN) to become a carrier solutionThe S-VLAN can be stacked over the existing customers 802.1Q-VLAN to pr

60、ovide transparency to customer VLANs (thus the name of VLAN stacking)(在輸入的V-LAN客戶業(yè)務(wù)上在加上V-LAN的標號,叫作V-LAN堆棧)All rights reserved Jan. 2003, Alcatel Shanghai bellFrame FormatsDA(6 Byte)Type (8100)(2 Byte)Q-VLAN Tag(2 Byte)Length/Type(2 Byte)Data( 1500 Byte)FCS(4 Byte)Untagged FrameDA(6 Byte)SA(6 Byte)Length