How does cable achieve these data rates?In the late 1980s and early 1990s cable operators started deploying fiber optics in their networks.Cable companies ran fiber out to individual neighborhoods and made use of existing network of coaxial cable to reach the “last mile”to each home.The opticaloptical fibers connect the cable operator’s central facility (the “head end”)to each neighborhood area (the “node”).Fiber has greatly increased the capacitycapacity and reliability of cable TV networks.With a cable Internet connection,data occupy the space of one TV channel.Tune to this channel with your TV,and you’ll see only static,but connected to your cable modem it becomes a data stream flowing at about 40megabits per second (Mbps),which can then be relayed to your personal computer at rates up to 10Mbps.the fiber network also allow signals to be sent back from the home to the head end,making telephone and interactive vidio services possible.
通过有线电视上互联网
初次使用有线电视上互联网可以成为一次极为刺激的经历。图片和文本在你眼前飞快地闪过,图像和声音流畅地播放。当你看到这一切的时候,你会明白这才是因特网应该有的样子。就算对上网老手来讲,这也是一个全新的世界。
在提供这种家庭高速数据接入方面,有线电视已占得先机。在北美,已经有100多万个用户在使用有线调制解调器。在经过了1995年一连串的试验性配置之后,到现在多数大城市中都可以得到主流服务,整套系统已经成熟。
通过有线电视网上网其速度之快是传统拨号方式的100倍。速度快成了导致传统网络服务发生巨大变化的催化剂。有线上网永不下线。这使得用户可以随心所欲地拜访站点,而免去了登录之苦。
有线电视网的数据传输速率怎么会这么快呢?从20世纪80年代末到90年代初,有线服务商开始在网络中配置光纤。有线电视公司把光纤铺到小区,再利用现有的同轴电缆网络深入到千家万户。光纤则将有线电视服务商的中心装置(始端)和小区(节点)连接起来。光纤大大提高了有线电视网的性能和可靠性。网络数据占据电视的一个频道。当你调到这个频道的时候,只能看到静止的画面,但是如果连上你的有线调制解调器,它就会变成速度为每秒约40兆位的数据流。该数据流可以再以每秒10兆位的速度传入个人电脑。光纤网络还允许将信号上传回始端,从而实现电话和互动电视功能。
Staying on Topic
Of course,surfing the web isn’t just about finding the latest or greatest.There’s plenty of valuable information online that’s been there for some time.But how do you find it when you’re not looking for something specific?Simple.Seek out topicbased starting points.Yahoo!’s entire hierarchyhierarchy is based on topics.Each toplevel category is divided into subtopics and some subtopics are further divided,and so on and so on.So,if you’re interested in model railroads,you can navigatenavigate through the Yahoo!directory (Recreation to Hobbies to Models to Trains)or you can simply tipe “model railroad”in the Yahoo!search box.Either way,you’ll get to a whole categary of modelrailroadrelated web sites.As complete as the Yahoo!Databasedatabase is,it’s not the only source for topicbased surfing.Other sites,such as LookSmart,The Argus ClearingHouse,and The Mining Company provide filtered lists of links,organized by topic.
围绕主题
当然冲浪不是仅仅去找最新的或者最好的东西,许多很有价值的信息已在网上存在了一段时间了。假如你不去寻找某一样特定东西,你怎么能够发现它呢?很简单,不要怕花力气去找到一个以题目为等级结构的起点。整个雅虎的等级结构是按题目分类的,从每一个题目分类的最高级向下分成小标题,其中某些小标题还要继续往下分成更小的标题,这样,如果你对铁路模型有兴趣,你就可以在雅虎目录中冲浪航行,从Recreation(娱乐活动)到Hobbies(嗜好),到Models(模型),到Trains(火车)。你也可以直接在雅虎搜索框内键入“Model Railroad”。通过这两种办法你都可以到达与铁路模型相关的整个类别的站点。尽管雅虎数据库是相当完整的,但它并非按标题分类的唯一冲浪资源。另外一些站点,如LookSmart、The Argus ClearingHouse以及The Mining Company,它们提供的经过适当选择的链接列表也是按照标题组织的。
It’s in the Links
Very often people include their own collections of related links on the sites they build.You may have noticed a few on some of your favorite destinationsdestination.For example,a fan’s baseball site may include a handful of links to other terrific baseball sites.A site about making muffinsmuffin may include links to other sites about baking,or deserts in general.It’s this type of linking that makes the Web a “web”in the true sense of the word.And as a surfer,you can take advantage of other people’s explorations.The next time you visit one of you own preferred sites,look for the links.You might find yourself headed in an unexpected,somewhat “cool”direction.
Sometimes people build pages that are simply collections of links.Yahoo!calls these pages “Indices”.They are often huge lists of sites that cover a particularparticular subject,or set of subjects.Whenever you’re surfing Yahoo!,look for the “Indices”category.that’s where the links live.Surf away.
在链接中寻找
人们经常把自己收集的一些相关的链接放到自己创建的网址中去,你有可能注意到一些你最喜欢的目标,例如垒球迷网址可能会包括一些能够链接到另外一些非常棒的垒球站点。一个有关制作松糕的站点通常有可能包括通向烘烤或者甜点心的链接。就是这一类的链接使得因特网找到了万维网的真实感觉。作为一个冲浪者,你可以充分利用别人探索的成果。下次,当你访问你自己喜欢的某一个网站时,寻找一下链接,不知不觉你就会发现自己向着一个意想不到的、有点“酷”味的方向前进。
有时候人们专门创建一些全是链接的网页,雅虎把这些网页叫“索引”。它们是一些很大的列表,包括了一个特定的主题或一组主题,无论何时冲浪雅虎,寻找“索引”类别,那儿是链接所在,尽情地冲吧!