計算機專業(yè)畢業(yè)設計外文翻譯--互聯網絡分層模型

1、<p>　　附錄A 外文翻譯-原文部分</p><p>　　Internetworking and Layered Models</p><p>　　The Internet today is a widespread information infrastructure, but it is inherently an insecure channel for sending

2、messages. When a message (or packet) is sent from one Website to another, the data contained in the message are routed through a number of intermediate sites before reaching its destination. The Internet was designed to

3、accommodate heterogeneous platforms so that people who are using different computers and operating systems can communicate. The history of the Internet is complex a</p><p>　　Early arpanet researchers accompl

4、ished the initial demonstrations of packetswitching technology. In the late 1970s, the growth of the Internet was recognised and subsequently a growth in the size of the interested research community was accompanied by a

5、n increased need for a coordination mechanism. The Defense Advanced Research Projects Agency (DARPA) then formed an International Cooperation Board (ICB) to coordinate activities with some European countries centered on

6、packet satellite research, </p><p>　　review body. </p><p>　　Since the early 1980s, the Internet has grown beyond its primarily research roots, to include both a broad user community and increase

7、d commercial activity. This growth in the commercial sector brought increasing concern regarding the standards process. Increased attention was paid to making progress, eventually leading to the formation of the Internet

8、 Society in 1991. In 1992, the Internet Activities Board was reorganised and renamed the Internet Architecture board (IAB) operating under the aus</p><p>　　1.1 Networking Technology</p><p>　　Dat

9、a signals are transmitted from one device to another using one or more types of transmission media, including twisted-pair cable, coaxial cable and fibre-opticable. A message to be transmitted is the basic unit of networ

10、k communications. A message may consist of one or more cells, frames or packets which are the elemental units for network communications. Networking technology includes everything from local area networks (LANs) in a lim

11、ited geographic area such as a single building, departmen</p><p>　　1.1.1 Local Area Networks (LANs)</p><p>　　A local area network (LAN) is a communication system that allows a number of independ

12、ent devices to communicate directly with each other in a limited geographic area such as a single office building, a warehouse or a campus. LANs are standardised by three architectural structures: Ethernet, token ring an

13、d fibre distributed data interface (FDDI).</p><p>　　(1) Ethernet</p><p>　　Ethernet is a LAN standard originally developed by Xerox and later extended by a joint venture between Digital Equipment

14、 Corporation (DEC), Intel Corporation and Xerox. The access mechanism used in an Ethernet is called Carrier Sense Multiple Access with Collision Detection (CSMA/CD). In CSMA/CD, before a station transmits data, it must c

15、heck the medium where any other station is currently using the medium. If no other station is transmitting, the station can send its data. If two or more statio</p><p>　　(2) Token Ring</p><p>　　

16、Token ring, a LAN standard originally developed by IBM, uses a logical ring topology. The access method used by CSMA/CD may result in collisions. Therefore, stations may attempt to send data many times before a transmiss

17、ion captures a perfect link. This redundancy can create delays of indeterminable length if traffic is heavy. There is no way to predict either the occurrence of collisions or the delays produced by multiple stations atte

18、mpting to capture the link at the same time. Token ring reso</p><p>　　(3) Fiber Distributed Data Interface (FDDI)</p><p>　　FDDI is a LAN protocol standardised by ANSI and ITU-T. It supports data

19、 rates of 100 Mbps and provides a high-speed alternative to Ethernet and token ring. When FDDI was designed, the data rate of 100 Mbps required fibre-optic cable. The access method in FDDI is also called token passing. I

20、n a token ring network, a station can send only one frame each time it captures the token. In FDDI, the token passing mechanism is slightly different in that access is limited by time. Each station keeps a tim</p>

21、<p>　　1.1.2 Wide Area Networks (WANs)</p><p>　　A WAN provides long-distance transmission of data, voice, image and video informationover large geographical areas that may comprise a country, a continen

22、t or even the world.In contrast to LANs (which depend on their own hardware for transmission), WANs can utilise public, leased or private communication devices, usually in combination.</p><p><b>　　(1)

23、PPP</b></p><p>　　The Point-to-Point Protocol (PPP) is designed to handle the transfer of data using either asynchronous modem links or high-speed synchronous leased lines.</p><p>　　The PPP

24、 frame uses the following format:</p><p>　?、貴lag field: Each frame starts with a one-byte flag whose value is 7E(0111 1110). The flag is used for synchronisation at the bit level between the sender and recei

25、ver.</p><p>　?、贏ddress field: This field has the value of FF(1111 1111).</p><p>　　③Control field: This field has the value of 03(0000 0011).</p><p>　?、躊rotocol field: This is a two-

26、byte field whose value is 0021(0000 0000 0010 0001) for TCP/IP.</p><p>　?、?Data field: The data field ranges up to 1500 bytes.</p><p>　　⑥CRC: This is a two-byte cyclic redundancy check. Cyclic r

27、edundancy check (CRC) is </p><p>　　implemented in the physical layer for use in the data link layer. A sequence of redundant bits (CRC) is appended to the end of a data unit so that the resulting data unit b

28、ecomes exactly divisible by a predetermined binary number. At its destination, the incoming data unit is divided by the same number. If there is no remainder, the data unit is accepted. If a remainder exists, the data un

29、it has been damaged in transit and therefore must be rejected.</p><p><b>　　(2) X.25</b></p><p>　　X.25 is widely used, as the packet switching protocol provided for use in a WAN. It w

30、as developed by the ITU-T in 1976. X.25 is an interface between data terminal equipment and data circuit terminating equipment for terminal operations at the packet mode on a public data network. X.25 defines how a pack

31、et mode terminal can be connected to a packet network for the exchange of data. It describes the procedures necessary for establishing connection, data exchange, acknowledgement, flow control and</p><p>　　(3

32、)Asynchronous Transfer Mode (ATM)</p><p>　　ATM is a revolutionary idea for restructuring the infrastructure of data communication. It is designed to support the transmission of data, voice and video through

33、a high data-rate transmission medium such as fibre-optic cable. ATM is a protocol for transferring cells. A cell is a small data unit of 53 bytes long, made of a 5-byte header and a 48-byte payload.</p><p>　

34、　The header contains a virtual path identifier (VPI) and a virtual channel identifier (VCI). These two identifiers are used to route the cell through the network to the final destination. An ATM network is a connection-o

35、riented cell switching network. This means that the unit of data is not a packet as in a packet switching network, or a frame as in a frame relay, but a cell. However, ATM, like X.25 and frame relay, is a connection-orie

36、nted network, which means that before two systems can communi</p><p>　　1.2 Connecting Devices</p><p>　　Connecting devices are used to connect the segments of a network together or to connect net

37、works to create an internetwork. These devices are classified into five categories: switches, repeaters, bridges, routers and gateways. Each of these devices except the first one (switches) interacts with protocols at di

38、fferent layers of the OSI model. Repeaters forward all electrical signals and are active only at the physical layer. Bridges store and forward complete packets and affect the flow control o</p><p>　　Figure 1

39、-1</p><p>　　1.2.1 Switches</p><p>　　A switched network consists of a series of interlinked switches. Switches are hardware software devices capable of creating temporary connections between two

40、or moredevices to the switch but not to each other. Switching mechanisms are generally classifiedinto three methods: circuit switching, packet switching and message switching.</p><p>　　(1)Circuit switching c

41、reates a direct physical connection between two devices such as telephones or computers. Once a connection is made between two systems, circuit switching creates a dedicated path between two end users. The end users can

42、use the path for as long as they want.</p><p>　　(2) Packet switching is one way to provide a reasonable solution for data transmission. In a packet-switched network, data are transmitted in discrete units of

43、 variable-length blocks called packets. Each packet contains not only data, but also a header with control information. The packets are sent over the network node to node. At each node, the packet is stored briefly befor

44、e being routed according to the information in its header. In the datagram approach to packet switching, each packet is t</p><p>　　1.2.2 Bridges</p><p>　　Bridges operate in both the physical and

45、 the data link layers of the OSI model. A single bridge connects different types of networks together and promotes interconnectivity between networks. Bridges divide a large network into smaller segments. Unlike repeater

46、s, bridges contain logic that allows them to keep separate the traffic for each segment. Bridges are smart enough to relay a frame towards the intended recipient so that traffic can be filtered. In fact, this filtering o

47、peration makes bridg</p><p>　　1.2.3 Routers</p><p>　　Routers operate in the physical, data link and network layers of the OSI model. The Internet is a combination of networks connected by router

48、s. When a datagram goes from a source to a destination, it will probably pass through many routers until it reaches the router attached to the destination network. Routers determine the path a packet should take. Routers

49、 relay packets among multiple interconnected networks. In particular, an IP router forwards IP datagrams among the networks to which it con</p><p>　　(1)The routing module receives an IP packet from the proce

50、ssing module. If the packet is to be forwarded, it should be passed to the routing module. It finds the IP address of the next station along with the interface number from which the packet should be sent. It then sends t

51、he packet with information to the fragmentation module. The fragmentation module consults the MTU table to find the maximum transfer unit</p><p>　　(MTU) for the specific interface number.</p><p>

52、;　　(2)The routing table is used by the routing module to determine the next-hop address of the packet. Every router keeps a routing table that has one entry for each destination network. The entry consists of the destina

53、tion network IP address, the shortest distance to reach the destination in hop count, and the next router (next hop) to which the packet should be delivered to reach its final destination. The hop count is the number of

54、networks a packet enters to reach its final destination. A rout</p><p>　　particular router is equal to the sum of the metrics of networks that comprise the</p><p>　　route. A router chooses the r

55、oute with the shortest (smallest value) metric. The metric</p><p>　　assigned to each network depends on the type of protocol. The Routing Information</p><p>　　Protocol (RIP) treats each network

56、as one hop count. So if a packet passes through 10</p><p>　　networks to reach the destination, the total cost is 10 hop counts. The Open Shortest</p><p>　　Path First protocol (OSPF) allows the a

57、dministrator to assign a cost for passing through a network based on the type of service required. A route through a network can have different metrics (costs). OSPF allows each router to have several routing tables base

58、d on the required type of service. The Border Gateway Protocol (BGP) defines the metric should specify the optimum path for the packet. The table can be either static or dynamic. A static table is one that is not changed

59、 frequently, but a dy</p><p>　　(3)A metric is a cost assigned for passing through a network. The total metric of a particular router is equal to the sum of the metrics of networks that comprise the</p>

60、<p>　　route. A router chooses the route with the shortest (smallest value) metric. The metric</p><p>　　assigned to each network depends on the type of protocol. The Routing Information</p><

61、p>　　Protocol (RIP) treats each network as one hop count. So if a packet passes through 10</p><p>　　networks to reach the destination, the total cost is 10 hop counts. The Open Shortest</p><p>

62、;　　Path First protocol (OSPF) allows the administrator to assign a cost for passing through a network based on the type of service required. A route through a network can have different metrics (costs). OSPF allows each

63、router to have several routing tables based on the required type of service. The Border Gateway Protocol (BGP) defines the metric totally differently. The policy criterion in BGP is set by the administrator. The policy A

64、defines the paths that should be chosen.</p><p>　　附錄B 外文翻譯-譯文部分</p><p><b>　　互聯網絡分層模型</b></p><p>　　今天，互聯網是一個廣泛的信息基礎設施，而它本質上是一個不安全的發(fā)送郵件的通道。當一個消息（或分組）從一個網站發(fā)送到另一個網站時，在消息中包含的

65、數據是通過一個路由的數目到達目的地之前的中間點。互聯網被設計為容納異構平臺，使人們使用不同電腦進行溝通的操作系統?；ヂ摼W的歷史是復雜的，涉及許多方面 ——技術，組織和社區(qū)。</p><p>　　早期ARPANET的研究人員完成了最初的packetswitching技術。在70年代末，隨著互聯網的增長，后來在研究界的關注規(guī)模也增大了，于此同時協調機制也需要增加。美國國防高級研究項目局（DARPA），成立了一個國際合

66、作委員會（工商銀行），一些歐洲國家以配合衛(wèi)星研究為中心的數據包的活動，或者說因特網配置控制委員會（局）協助DARPA的管理互聯網活動。1983年，DARPA認識到，互聯網的持續(xù)增長導致了社會所要求的協調機制因此而轉型。IAB的振興互聯網工程任務組（IETF）為一對IAB的成員。到1985年有了巨大的增長，在實際工程方面，互聯網的這種增長引起了IETF的工作小組形式。 DARPA已不再是主要參與互聯網的資金。從那時起，互聯網一直是降低DA

67、RPA的活動。 IAB公司認識到IETF的重要性日益增加，并改組為主要標準的Internet工程指導小組（IESG）審查機構。</p><p>　　20世紀80年代初以來，互聯網已經超越了其主要研究的項目，包括廣泛的用戶群，以此來增加商業(yè)活動。這一增長在商業(yè)界帶來了越來越多的關注。增加重視并取得進展，最終在1991年形成了互聯網協會。1992年，互聯網活動委員會進行了重組和改名,互聯網架構委員會（IAB）在互聯網

68、的贊助下運作。IAB中，IESG和IETF相互支持的關系導致他們采取更多的措施，審批標準，隨著規(guī)定服務和其他措施,將促進IETF的工作。</p><p><b>　　1.1網絡技術</b></p><p>　　數據信號從一個設備傳送到另一個設備時需使用一個或多個類型的傳輸介質，包括雙絞線電纜，同軸電纜和光纖電纜。一個信息傳送是網絡通信的基本單位。一個消息可能是一個或多

69、個單元格，幀或數據包為單位的網絡元素通訊。網絡技術包括一切從局域網在有限的地理區(qū)域，如單個建設，部門或校園廣域網（WAN）在較大的地理區(qū)域，可能包括一個國家，非洲大陸乃至整個世界。</p><p>　　1.1.1局部區(qū)域網絡（局域網）</p><p>　　局域網（LAN）對本地區(qū)域網絡（LAN）是一種通信系統，允許獨立的數目設備直接與每一個有限的地理區(qū)域等作為一個單一的辦公樓，倉庫或校園。

70、三是規(guī)范局域網建筑結構：以太網，令牌環(huán)網和光纖分布式數據接口（FDDI）。</p><p><b>　　(1)以太網</b></p><p>　　以太網是局域網標準,最初是由施樂公司開發(fā)的，后來延長了聯合企業(yè)之間的數字設備公司（DEC），英特爾公司和施樂公司。訪問機制用在以太網稱為載波偵聽多路訪問碰撞檢測。在CSMA / CD中，前一站傳送的數據，它必須檢查目前使用的

71、媒介。如果沒有其他發(fā)射站，該站可發(fā)送其數據。如果在兩個或更多的站發(fā)送數據的同時，那它可能會導致沖突。因此，要不斷檢查各站的任何碰撞。如果碰撞發(fā)生時，所有站的數據可忽略收到。發(fā)送站等待一段時間才能重新發(fā)送數據。以至減少第二碰撞的可能性，發(fā)送站隨機生成的決定因素是應該等待多久才能重新發(fā)送數據。</p><p><b>　　(2)令牌環(huán)</b></p><p>　　令牌環(huán)網

72、，局域網標準最初是由IBM開發(fā)，采用了邏輯環(huán)的拓撲。訪問方法使用CSMA / CD的可能導致沖突。因此，車站的互聯網絡和三分層模型前一個傳輸，嘗試將數據發(fā)送多次捕捉一個完美的鏈接。這種冗余可以創(chuàng)建不可估計長度的延遲，如果在交通繁忙的時候，有沒有辦法試圖預測碰撞和多個電視臺制作延誤在同一時間的聯系。令牌環(huán)網解決這種不確定性使站輪流發(fā)送數據。作為訪問方法，令牌傳遞順序從車站到車站，直到遇到一個站發(fā)送數據。該站為發(fā)送的數據等待令牌。該車站然后

73、捕獲令牌和發(fā)送的數據幀。此數據幀左右的收益環(huán)，每個站再生框架。每個中間站檢查目的地址，如果發(fā)現該幀是給另一個車站，它繼電器鄰近車站。預期的收件人確認自己的地址，復制信息，進行錯誤檢查和變化中的四個幀的最后一個字節(jié)表示位該地址已被確認和幀復制。完整的數據包，然后周圍環(huán)，直到它返回到車站。</p><p>　　(3)光纖分布式數據接口（FDDI）</p><p>　　FDDI的網絡協議是一個由

74、ANSI和ITU - T的標準化。它支持的數據傳輸速率100 Mbps和提供高速替代以太網和令牌環(huán)。當光纖分布式數據介面是設計，100 Mbps的數據速率所需的光纖電纜。在FDDI的訪問方法又稱為令牌傳遞。在令牌環(huán)網，一站可以只發(fā)送一幀每次捕獲令牌。在光纖分布式數據介面，令牌傳遞機制略有不同的是訪問時間的限制。每個站保持一個計時器，顯示該令牌時，應離開車站。如果一個站接收指定的令牌時間早，它可以保持令牌和發(fā)送數據，直到離開預定的時間。另

75、一方面，如果一個站接收到令牌在指定時間或晚于這個時候，應該讓令牌傳遞給下一個車站，等待它的下一個轉折。FDDI的實現為雙環(huán)。在大多數情況下，數據傳輸，僅局限于主環(huán)。二次環(huán)是提供了與主環(huán)的故障情況。一個問題在主環(huán)發(fā)生時，第二圈可激活完成數據電路和維護服務。</p><p>　　1.1.2廣域網（WAN） </p><p>　　一個廣域網提供長途數據，語音，圖像和視頻傳輸的信息 在廣大的地理區(qū)

76、域，可能包括一個國家，一個大陸乃至世界。 相對于局域網，廣域網可以利用公共出租或私人通訊設備，通常將他們結合使用。 </p><p><b>　　(1)購買力平價 </b></p><p>　　點對點協議（PPP）是用于設計處理數據傳輸或使用異步調制解調器鏈接或高速同步租用線路。PPP幀使用格式如下：</p><p>　?、贅酥咀侄危好總€幀開頭

77、有一個字節(jié)標志，它的值是7E（0111 1110）。該標志用于同步在發(fā)送者和接收者之間的水平位。 </p><p>　　②地址欄：此欄有法郎（1111 1111）值。 </p><p>　?、劭刂谱侄危涸撟侄蔚闹?3（0000 0011）。 </p><p>　　④協議字段：這是一個兩個字節(jié)的字段的值是0021（0000 0000 0010 0001） 為TCP /

78、 IP協議。 </p><p>　?、輸祿颍簲祿蚍秶_1500個字節(jié)。 </p><p>　?、奕A潤：這是一個兩個字節(jié)的循環(huán)冗余校驗。循環(huán)冗余校驗（CRC） 實現在物理層的數據鏈路層。一個序列 （CRC）的冗余位是追加到一個數據單元結束時，使所產生的數據 單位變成了一個預定的整除的二進制數。在它的目的地，傳入的數據單元除以相同的號碼。如果沒有余下的時間， 數據單元被接受。如果其余的存在

79、，數據單位已在運輸途中受損 因此必須予以拒絕。</p><p><b>　　(2) X.25 </b></p><p>　　X.25作為交換成廣域網的使用提供了一個協議數據包。這是由ITU - T制定于1976年。X.25是一個終端設備之間的數據接口和數據電路終端行動終止在設備上的數據包模式公共數據網絡。X.25定義了如何將一個終端連接到一個數據包網絡的數據交換。它描

80、述了必要的程序，建立了連接和數據的交換，然后確認流量控制和數據控制。 </p><p>　　(3)異步傳輸模式（ATM） </p><p>　　ATM是一種重組的數據通信基礎設施的革命思想。它旨在通過支持高數據率的數據傳輸，語音和視頻傳輸介質，如光纖電纜。ATM是一個細胞轉移協議。一 個細胞是一個53字節(jié)的小數據單元長，一個5字節(jié)的報頭，并建立一個48字節(jié)的有效載荷。 互聯網絡和5分層模型

81、標頭包含一個虛擬路徑標識符（VPI）和一個虛擬通道標識符（VCI的）。 這兩個標識符用于路由通過網絡向最終目的地的細胞。 ATM網絡是一個面向連接的細胞交換網。然而，自動柜員機，如X.25和幀中繼是面向連接的網絡， 這意味著前兩個系統可以溝通，他們必須進行連接。至 啟動一個連接，系統使用一個20字節(jié)的地址。</p><p><b>　　1.2連接器件</b></p><p

82、>　　連接設備是用于將網絡的一個部分連接在一起或互聯的網絡。這些設備可分為五類：交換機，中繼器，網橋，路由器和網關。這些設備的每一個除第一（交換機）與交互在OSI模型的不同層協議.中繼器積極的轉發(fā)所有的電子信號，只在物理層。網橋完整的存儲和轉發(fā)數據包并影響一個單一的局域網流量控制。網橋活躍在物理和數據鏈路層。路由器提供兩個單獨的鏈接局域網和活躍于物理層，數據鏈路層和網絡層。最后，網關不兼容的局域網之間提供翻譯服務或應用程序，并積極

83、在所有層次。連接設備，在OSI模型的不同層協議見圖1-1:</p><p><b>　　圖 1-1</b></p><p><b>　　1.2.1開關</b></p><p>　　交換式網絡由一組相互關聯的開關系列組成。交換機是在硬件/軟件設備之間建立的，它是連接兩個或多個臨時網絡到交換機的設備。開關機制一般分為三種方法：

84、電路開關，分組交換和信息交換。</p><p>　　(1)電路交換兩個設備之間建立了直接的物理連接，如電話或電腦。一旦建立了連接了兩個系統，那么電路開關兩端就會建立一個用戶專用的道路。</p><p>　　(2)分組交換是一種為數據傳輸提供合理的解決方案的設備。每個數據包不僅包含數據，而且還可控制信息。數據包通過網絡發(fā)送節(jié)點到節(jié)點信息。在分組交換數據包方式，每個數據包被視為是獨立的，它是單

85、獨存在的，在虛電路方式分組交換中，如果是是發(fā)送者和接收者之間選擇在開始會議期間的，所有的數據包會沿著這條路線一個接一個。盡管這兩種方法似乎是相同的，但是它們之間存在著根本區(qū)別。在電路交換中，兩者之間的最終用戶的路徑只包含一個通道。在這種方法中，計算機（或節(jié)點）接收到相應的路由信息,那么它是免費的，然后發(fā)送它,該方法已被淘汰。</p><p><b>　　1.2.2 網橋</b></p&

86、gt;<p>　　網橋橫跨在兩個物理鏈路層和數據鏈路層的OSI模型間，將不同類型的網絡互聯起來，并促進網絡之間的聯系。網橋部分劃分成較小的一個大型網絡。網橋有足夠的能力朝著預期的收件人，使之能夠被過濾。其實，這使得網橋的過濾操作控制功能有用，并使得能夠安全通過這種交通分區(qū)。網橋可以訪問連接到它的所有車站的物理地址。當幀進入網橋，網橋不僅重新生成了信號，而且還檢查地址，目的地和新的副本轉發(fā)給該段地址所屬。當遇到一包的網橋，它

87、讀取包含在框架中的地址并比較所有環(huán)節(jié)上站表的地址。當它找到互聯網絡和7種分層模型時，就會發(fā)現有部分車站所屬的中繼到該數據包片段。</p><p><b>　　1.2.3路由器 </b></p><p>　　路由器工作在物理層，數據鏈路和網絡層的OSI模型。該互聯網是由路由器連接的網絡的結合。路由器使用 在數據報目的地的地址選擇下跳到轉發(fā)數據報。 路由器 提供連接到許多

88、不同的物理網絡類型：以太網,令牌環(huán)，點至點鏈接，FDDI等。 </p><p>　　(1)模塊的路由處理模塊接收來自一個IP數據包。如果數據包要轉發(fā)，那它應該傳遞給路由模塊。它發(fā)現IP地址應該從該數據包接口數目的下一站被發(fā)送。然后處理被它發(fā)送的信息包的碎片模塊。該協商的成體系模塊表的MTU最大傳輸單元（MTU）為特定的接口。 </p><p>　　(2)路由器是由路由模塊用來確定下一跳地址

89、的數據包。每個路由器的路由表中保存了每一個目的地入境的網絡。該項目是目標網絡的IP地址，最短距離 到達目的地的跳數，下一個路由器應該以該數據包發(fā)送到最終目的地。路由器應該是當有一個路由表咨詢時，隨時可以轉發(fā)。路由表應指定為數據包的最佳路徑。該表可以是靜態(tài)或動態(tài)的。靜態(tài)表不是經常更換的，而動態(tài)表在自動更新時，某處可能有網絡在變化。今天，互聯網需要動態(tài)路由表來實現。 </p><p>　　(3)度量是通過網絡傳遞的分

90、配成本。一個總指標特別是路由器等于組成該網絡的數據總和路線。路由器選擇具有最短（最小價值線）的指標。度量分配給每個網絡取決于協議類型。路由信息協議（RIP）對待每一個網絡跳數為1。因此，如果一個數據包通過10次網絡到達目的地，總成本為10跳計數。開放式最短路徑優(yōu)先協議（OSPF）允許管理員指定途經成本對服務所需的類型為基礎的網絡。一個通過網絡路由可以有不同的指標。OSPF協議允許每個路由器有多個路由表構成的所需服務類型，是邊界網關協議（