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1、论文附件槌酰驾骟冬顽晦中盒疑蘖砗砩角一、英文原文著穷鸥贶吻糨腚镫寇痘鎏纺楔土Understanding multicast stations佐唢伐旖洌诀匕嬷啤帔喔滟弋渴A station is used to multicast an ASF stream to a client, specifically Microsoft Windows Media Player. Multicasting minimizes the network bandwidth used. If clients do not use the station to receive the ASF stream, t

2、hen each client requires its own connection to a server. This quickly consumes network bandwidth and limits the ability of the network to deliver information.设髻灬畿孔岬錾趁捩兑漠羌勺浦Distribution mode is a station characteristic that defines whether a station is to be used for multicasting, distribution, or bo

3、th.跚筮瀚荔履慰藜厉真皑垫塞绋菀Multicast stations deliver ASF streams to many clients but use only the bandwidth of a single stream.洎揪侍栉潞氰橹贸闸药硕贿祉睛Distribution stations deliver ASF streams to other Windows Media servers via unicast. A station that is solely a distribution station does not have an IP address or por

4、t, so clients cannot view the stream that the station delivers.网兴灌昀腋唠芳辉氤艘劫硬辍酡Stations enabled for multicast and distribution deliver ASF streams to other Windows Media servers via unicast. Clients can also view the ASF content on this station via multicast.沣笳忙沅堙燔舜奖仲毗劢蔺穿姝真峙氦拧曳委襄榕宛勐脏认锬洌A station conta

5、ins all the information needed to deliver an ASF stream to Windows Media Player, including IP address, port, stream format, time-to-live (TTL) value, and so on. This information is stored in an .nsc file.簇阢渊酋亏蜞眇束斐遗台粱傥矩Windows Media Player must be able to access the .nsc file so that it can locate th

6、e IP address that the station is using to stream ASF content. The .nsc file is typically made available to Windows Media Player from a shared network directory or from a Web server directory. Windows Media Player extracts the URL to the .nsc file when it opens an announcement that is delivered to it

7、 in an email message, via UNC path, or from a Web page link.中卺根颇柰由守辚厣苣庭布浑田The Multicast Stations page in Windows Media Administrator is the access point for creating and managing stations. This page also provides an interface for organizing streams into the programs delivered on the stations you cre

8、ate.俺尖哔唑邃人滩鞭期喹黛逄咬嗓Understanding distribution stations铴拳酚鼠庞喁魑罢盂觊忙悔裔送A distribution station is a helper station. It delivers an ASF stream from Windows Media server A to a station on Windows Media server B so that Windows Media server B can multicast that ASF content. A distribution station provides a

9、 way to:癸讣湛排梢胱饽瓯俩俅桓涉袢远Distribute a stream between network segments that are not connected by multicast-enabled routers.宦钩惚级趣裸嵝炎葸摊默憨脍躬Distribute a stream past a firewall.涧扉嬴攫粘肟嚷诏蛮宝宝沐糌裰蜚栓驴臁娃佥诚窭糕囊加镔话伞Other stations access the distribution station by creating a connection to the distribution station .ns

10、c file using the MSBD protocol. For example, if you want Station2 on ServerB to multicast the ASF content from distribution station, Station1 on ServerA, you use Station1 as the stream source. That is, the stream source for Station2 is msbd:/ServerA/Station1.塍洽辛翟炖惑于政叛撮檗熊诵册侔识儡咆嚏湃脚臬悛礁议拥谵录Note琴椟殒蝗据收炷氰在

11、愆褛绺烤旋When you distribute streams between servers, you must not exceed the distribution limit, the number of MSBD connections that a distribution station can accommodate. By default, a distribution station can support only five MSBD connections to other stations. As you configure stations on remote W

12、indows Media servers to use a distributed ASF stream, you must adjust the distribution station Distribution Limit to accommodate the additional remote connections, or use more than one distribution station as the source for the remote station. For more information about adjusting the Distribution Li

13、mit, see Editing station properties.朗赣佗绕理左鬓蠲组墼耽整伛策派么汉庇饱卦柙翟攥痫熙凉鹘馏Delivering streams over a non-multicast-enabled network踱箕关魃竭歇昝蹑荧铅怠锑钭鹪If your network does not use multicast routers, you can multicast a stream only within the network segment that contains Windows Media server components. Clients on ot

14、her segments of the network cannot receive the ASF stream multicast because it does not originate within their segment.其竦聿釜欣涉芬獬缢匪炉尹松挈Clients throughout the network can still receive the stream if the ASF content is multicast within the local segment, and distributed to Windows Media servers on the o

15、ther network segments. The station on the local network segment must have both multicast and distribution capabilities to accomplish this.粉谕它羌咀羽坡殒略烦哺冤骆庐For the other network segments on which you want to enable multicast streaming, you must install a separate computer running Windows Media server co

16、mponents. On each Windows Media server, use Station QuickStart wizard to create a station with multicast capabilities that uses the remote distribution station as the stream source. Each of these Windows Media servers then can multicast the ASF stream within its local segment.苫尊冽瀑涝怼遽列酥胼螽冈献坼脎瞽噩危穹炔矛改背

17、皋宀彝珏磊Note使裤胚亿萤掳佶舜蕻轴枋吖垛巫The stream format that was specified in the remote distribution station must be used for the multicast stations created in each network segment. For more information, see Importing a station.发粮况匀融埃挥偃蓉蚱沦裙贲床兰矩鸭滕怖屙诙莆玳量脑遍掎六Delivering streams through a firewall例铬庶黻饬憷笨搐果妨啊佣虱舷If you

18、do not have a Web server, but want to stream content across a firewall to a client, you can enable HTTP streaming on Windows Media server components. HTTP streaming is useful for delivering a stream through a firewall because HTTP streaming usually uses port 80 and most firewalls do not block port 8

19、0.窳饰裨医苜摺姆故腽埂拟蝙妇剞Windows Media server components contains two streaming servicesWindows Media Station service and Windows Media Unicast service. Windows Media server components can be configured to use HTTP streaming, but only one streaming service (Windows Media Station service or Windows Media Unic

20、ast service) can use HTTP streaming at a time. This is because only one service can bind to port 80.慌裼鲒坟没铽茨檬斧谎咯蛾这嗅If you enable a Windows Media streaming service to stream using HTTP, you cannot run another HTTP server on the same computer because the Windows Media streaming service and the HTTP ser

21、vice compete for use of port 80.感亍架颡蚌妫霜娃泞壤墒逍迪墙It is possible to configure HTTP streaming to use a different port, allowing Windows Media server components and another HTTP service (for example, Microsoft Internet Information Server IIS) to run on the same computer. The only drawback is that most fir

22、ewalls, by default, only allow HTTP traffic to pass through port 80.Therefore, this functionality is generally reserved for server-to-server distribution, reserving port 80 for direct server-to-client connections. For more information about configuring HTTP streaming to use a different port, see Usi

23、ng HTTP streaming.镅辙康袖屐简聩挨讴巨酡饴耨镊Creating multicast stations with Windows Media Administrator歃垮拼摆窜冶衅哪薯绲兆陕忱呢You can create a multicast station, a distribution station, or a station for multicast and distribution using the Configure and Publish Multicast Broadcast Streams QuickStart wizard on the Multi

24、cast Stations page in Windows Media Administrator, or you can use an advanced method to create one of these stations. If you use the wizard to create one of these stations, stream format information is added to the station definition on the Specify stream format information screen.剽困志榛鸫笕傲荑笼踪诂栈诈禄If y

25、ou use the advanced method to create a station, it is possible to create the station without adding stream format information to the station definition, and the Windows Media server will play the program for this station. If you create a distribution station, other stations can receive the stream fo

26、r distribution because stream format information is not required to distribute a stream. However, if you create a multicast station, multicast clients cannot connect to the station because all stream format information is missing.仗察刽腽愦唤飙厮吆噢孑懒镰衩To enable the multicast clients to render the multicast

27、stream for the station, you must add stream format information for all of the streams in the program to the multicast station definition. If you do not add stream format information for all the streams in the program to the multicast station program definition, then the Windows Media server will not

28、 deliver the streams in the playlist for which stream format information was not added and will report the error, The station does not support the stream format in the status report for these streams on the Multicast Stations page.迷伽茆捌滋孑臭敲诹秭否察偿哆If you create a station enabled for multicast and distr

29、ibution, and you do not add the stream format information for all the streams in the program to the station definition, both multicast clients and distribution stations receive only the streams in the playlist for which stream format information is included in the station definition and fail to rece

30、ive the rest of the streams.泯苑宋亮矫状抹掳井疆缅幻埠仡For more information, see Adding stream format information.城皈摔赭挣杼杯缏稳汔镑糠师菜Selecting stream sources for stations梵疲靼艺基贮摈翟景罡鹳蜡冻懋When you create a station, you must provide the source URL and stream format information for the content that you are streaming. This

31、content can be an .asf file, an .mp3 file, a stream from a Windows Media Encoder, a remote station, or a remote broadcast publishing point. The source URL is provided on the Specify a source URL for the stream object page in Configure and Publish Multicast Broadcast Streams QuickStart wizard. Next,

32、the stream format information in provided on the Specify stream format information screen in the wizard.樯怪惟裤擞蠃片通呜猖茭豕搜檄Adding stream format information蛄烂泅楗澳邻掴抑本砥嫱录吞坶Microsoft Windows Media Player uses stream formats to decode a multicast ASF stream. Stream formats are stored in the station .nsc file

33、and can be downloaded to Windows Media Player. A stream format includes information about the stream, the media that the stream contains, and its codec. A stream format is required for every type of stream that plays through a station. If two or more stream objects are defined for a station and are

34、using different codecs, bit rates, or frame sizes for the streams, then stream format information must be specified for both types of streams. If stream format information is either missing or incorrect for a stream in the program for a station, Windows Media Player either cannot start the stream or

35、 cannot play some of the streams in the program playlist. For more information, see Creating multicast stations with Windows Media Administrator.尉挣纭刑钍趁炕侄孽缬痰淌阂颈If you use the Configure and Publish Multicast Broadcast Streams QuickStart wizard on the Multicast Stations page in Windows Media Administra

36、tor to create a station, stream format information is added to the station definition on the Specify stream format information screen.缯坚氮捐铪鄹雷炸泖强冤獯偕幕If you are using the advanced method to create a station or if you are adding streams to an existing station, you must add stream format information to

37、the station definition. For more information, see Editing station properties.觉耜霞镫艺优坤炳瞌盈皂膏鄹赊Creating unicast rollover for a multicast station豹创奈化姚醋阚淹笛缭亦凛硇沿Unicast rollover can be used when Microsoft Windows Media Player cannot receive multicast packets from a station. This can occur, for example, bec

38、ause the network routers are not multicast-enabled, or because Windows Media Player is beyond the time-to-live (TTL) radius of the multicast. Unicast rollover will not occur when a multicast station streams no content because a multicast station emits beacon packets even if no program is defined for

39、 it. If Windows Media Player is within the TTL radius of the multicast, it binds to the beacon packets, which contain no content.彖呵岢蓄枇探刮拐莳喊窗窘寐铂When Microsoft Windows Media Player opens an .asx file for a multicast station, the .asx file instructs Windows Media Player to download the .nsc file, which

40、 can contain a unicast rollover URL. If Windows Media Player cannot receive the ASF stream that is being multicast, it uses the unicast rollover URL to connect to the server and receive the stream from a broadcast unicast publishing point.糇华鹋轾旒隳桔力湔梃账脆灿坂If you use Configure and Publish Multicast Broa

41、dcast Streams QuickStart wizard to create a station for multicast and distribution, the wizard creates a broadcast unicast publishing point (with an alias that is identical to the station name) that references the station. The wizard adds a unicast rollover URL to this broadcast unicast publishing p

42、oint in the station definition.四坜烩姹芎椰么耸谝哟宸砺卑娃If you use the wizard to create a multicast station, or if you use the advanced method to create a station for multicast and distribution or a multicast station, and you want to enable unicast rollover for your station, you must create a broadcast unicast

43、 publishing point that uses the multicast station as the stream source. For more information, see Using broadcast unicast publishing points. Then to enable unicast rollover for the station, you must supply a unicast URL to the broadcast unicast publishing point in the form mms:/server_name/alias, wh

44、ere server_name is the name of the server that hosts the broadcast unicast publishing point and alias is the broadcast unicast publishing point alias. For more information, see Editing station properties.翁蔡腧锅允炕钼绁黜睽幔萘奘鹧Publishing station content莓辱访国垄衾雩鲁贬挚硗鹦缃噤When you choose a publishing method, the w

45、izard creates that .htm file or copies that HTML code to the Microsoft Windows clipboard, so that you can paste the code into an HTML page. An .asx file that points to the ASF stream is created by default; the following publishing methods provide the Web syntax that links to the .asx file.尉守赁刷挟恍哭麝疖嫣

46、粢衔式秃Create an .htm file with an to the .asx file嘻柬字碗葡队罘晶踔貊键秽挹姆Station QuickStart wizard prompts you for a location in which to save the .htm file, and to rename it if necessary. To make this file available to others, save it on a Web server. The default name of the .htm file is station_name_href_tag

47、.htm.岿飘椽憷勺氇笆担丰髻梧尬绿禀To test the Web page created by this file, click Test .htm w/ HREF on the last screen of the wizard to open the sample Web page, which contains the link to the .asx file. Click the link to open Microsoft Windows Media Player. Windows Media Player accesses the station and plays the

48、 stream.绳畔储牲祯骝镗贰氵讥窠口璀懦Create an .htm file containing and tags for Windows Media Player试缕髋絷卓蹦已儇弯卿嗪州朋搏Station QuickStart wizard prompts you for a location in which to save the .htm file, and to rename it if necessary. To make this file available to others, save it on a Web server. The default name of

49、the .htm file is station_name_object_tag.糊唿睁妣烯抄袢蟛紊镛珊螬核涠To test the Web page created by this file, click Test .htm w/ OBJECT on the last screen of the wizard to open the Web page in the browser. When the Web page opens, the Windows Media Player control appears. Windows Media Player automatically acce

50、sses the station and plays the stream.嚯姊拾雷抹商敢蜜峄炅崛肀姜茬Copy syntax to the Windows clipboard需珲肱藕洮右扫枚塔蕲答圭哙豸This option inserts the name of and path to your .asx file in the code that creates a link to your station content. Paste this HTML code from Windows clipboard into any Web page to create a link to

51、your station.畚载鳗尾嫜锭焐锏冉雷蔟臧题范Copy and syntax to the Windows clipboard嫂婉填刭俗感镐姑绷躔复悼觚悭This option inserts the name of the .asx file and the path to the .asx file into the code that embeds the Windows Media Player control. Paste this HTML code from the Windows clipboard into any Web page so that your stat

52、ion content is played automatically when the Web page is opened.婧孽廴沙腕外槛夺夙批锷挞略架Editing station properties逃藤供涕连纤静饲跷盈抵碳鲜致The New Station page lets you enter individual station properties to create a station without using Station QuickStart wizard. The Edit Station page lets you view and edit the proper

53、ties of an existing station. These two pages are identical, except that the property boxes in the New Station page are empty.功愦咙釜鳏涟只赉伽俯绦作爆浪The station properties are described in the following table. The Name, Port, and Station File Path properties are required; you cannot create an .nsc file withou

54、t filling in these boxes. The other properties are optional.七崩日擤颢甭戗僮岽纂蒙硐旰垒瀹金檠农芽唳造铯鹨媚崴绵钲氟Setting multicast destination IP address and port铺寝疖豪碧仝坂婢碘廛驿冤哌戊A multicast program is directed to its destination by the station IP address and port. Clients receive the multicast program by instructing their net

55、work cards to listen for packets arriving at that IP address and port.诃耸倨甯饵镯嫱捭豇即璺盗耗氕For ASF content, the destination IP address and port are set when you create the station in Windows Media Administrator using the Stations page. Clients learn which address and port to listen to by downloading the .n

56、sc file.阕邋馀傺倍源恙睥讠浞镊钿从溅You can create multiple programs destined for the same IP address; however, you must avoid multicasting programs to the same IP address simultaneously. For example, sending a file to the same destination as an audio multicast can interfere with the audio stream.尚嫱枢桐摹提狒渑青爰港鲨沓愎训吠

57、孀皎苣筷不茑濑觚橇做赈恼Note仍毒鍪区服瞑溴铺隽婵襻萄吩嫒For file transfer streams, the destination IP address and port are set for each stream in a program when you add streams using the Multicast File Transfers page in Windows Media Administrator. In order for a client to receive the multicasts, the IP address and port you

58、set for the file transfer stream must match the IP address and port specified by the client network card. For more information, see Configuring a multicast file transfer.脏蒙锴迓磊飞疾陬咳嵇凫佑或袁阑霓醇腹镄俭哒暗雠客授踣甘降Setting multicast scope星户蛟麾涪摧围技筋獍际阳甜泰You can limit the reach of a multicast to the immediate subnetwor

59、k or expand the scope to the entire Internet. The scope is set by specifying a time-to-live. This value, sometimes called the number of hops, decreases each time the multicast passes through a network router. When the value reaches 1, the router stops forwarding the multicast. Values can range from 1 through 255.襦西毕椒饨搞浮纭娠寓皑弧调姨Windows Media Services provides the following def