To address the issues with network interoperability, the ISO researched different communication systems. As a result of this research, the ISO created the ISO OSI model to serve as a framework on which a suite of protocols can be built. The vision was that this set of protocols would be used to develop an international network that would not depend on proprietary systems. In the computer industry, proprietary means that one company or a small group of companies uses their own interpretation of tasks and processes to implement networking. Usually, the interpretation is not shared with others, so their solutions are not compatible; hence they do not communicate. Meanwhile, the TCP/IP protocol suite was used in the first network implementations. It quickly became a standard, meaning that it was the protocol suite implemented in practice. Consequently, it was chosen over the OSI protocol suite and became the standard in network implementations today.
為了解決網路互通性的問題，ISO 研究了各種不同的通訊系統。研究的成果是 ISO 建立了 ISO OSI 模型，作為建構一套協定的框架。當時的願景是以這組協定發展出不依賴專屬系統的國際網路。在電腦產業中，專屬（proprietary）指的是一家公司或少數幾家公司以自己對工作與流程的詮釋來實作網路。這種詮釋通常不與他人分享，因此它們的解決方案彼此不相容，也就無法通訊。與此同時，TCP/IP 協定套組已被用於最早的網路實作。它很快成為標準，也就是實務上實際採用的協定套組。因此，它取代了 OSI 協定套組，成為現今網路實作的標準。
The OSI reference model describes how data is transferred over a network. The model addresses hardware and software equipment and transmission.
OSI 參考模型描述資料如何在網路上傳輸。此模型涵蓋硬體與軟體設備以及傳輸。
The OSI model provides an extensive list of functions and services that can occur at each layer. It also describes the interaction of each layer with the layers directly above and below it. More importantly, the OSI model facilitates an understanding of how information travels throughout the network. It provides vendors with a set of standards that help ensure compatibility and interoperability between the various types of network technologies that companies produce around the world. The OSI model is also used for computer network design, operation specifications, and troubleshooting.
OSI 模型提供了每一層可能發生的功能與服務的詳盡清單。它也描述了每一層與其直接上層及下層之間的互動。更重要的是，OSI 模型有助於理解資訊如何在整個網路中傳遞。它為廠商提供一組標準，協助確保全球各公司所生產的各種網路技術之間的相容性與互通性。OSI 模型也用於電腦網路設計、運作規範與疑難排解。
Roughly, the model layers can be grouped into upper and lower layers. Layers 5 to 7, or upper layers, are concerned with user interaction and the information that is communicated, its presentation, and how the communication proceeds. Layers 1 to 4, the lower layers, are concerned with how this content is transferred over the network.
大致上，模型的各層可分為上層與下層。第 5 到第 7 層，即上層，關注的是使用者互動、所傳達的資訊、資訊的呈現，以及通訊如何進行。第 1 到第 4 層，即下層，關注的是這些內容如何透過網路傳輸。
The OSI reference model separates network tasks into seven layers, which are named and numbered.
OSI 參考模型將網路工作分為七層，各層都有名稱與編號。
- Layer 1: The physical layer defines electrical, mechanical, procedural, and functional specifications for activating, maintaining, and de-activating the physical link between devices. This layer deals with the electromagnetic representation of bits of data and their transmission. The physical layer specifications define line encoding, voltage levels, the timing of voltage changes, physical data rates, maximum transmission distances, physical connectors, and other attributes. This layer is the only layer implemented solely in hardware.第 1 層：實體層定義啟動、維持與停用裝置之間實體鏈結所需的電氣、機械、程序與功能規格。這一層處理資料位元的電磁表示方式及其傳輸。實體層規格定義了線路編碼、電壓準位、電壓變化的時序、實體資料速率、最大傳輸距離、實體接頭及其他屬性。這一層是唯一完全以硬體實作的層。
- Layer 2: The data link layer defines how data is formatted for transmission and controlled access to physical media. This layer typically includes error detection and correction to help ensure reliable data delivery. The data link layer involves network interface controller to network interface controller (NIC-to-NIC) communication within the same network or subnet. This layer uses a physical address, sometimes called a MAC address, to identify hosts on the local network.第 2 層：資料鏈結層定義資料如何格式化以便傳輸，並控制對實體媒介的存取。這一層通常包含錯誤偵測與更正，以協助確保資料可靠遞送。資料鏈結層負責同一網路或子網路內，網路介面控制器對網路介面控制器（NIC 對 NIC）的通訊。這一層使用實體位址（有時稱為 MAC 位址）來識別本地網路上的主機。
- Layer 3: The network layerprovides connectivity and path selection beyond the local segment, all the way from the source to the final destination. The network layer uses logical addressing to manage connectivity. In networking, the logical address is used to identify the sender and the recipient. The postal system is another common system that uses addressing to identify the sender and the recipient. Postal addresses follow the format that includes name, street name, and number, city, state, and country. Network logical addresses have a different format than postal addresses; they are determined by the network layer rules. Logical addressing helps ensure that a host has a unique address or that it can be uniquely identified in terms of network communication.第 3 層：網路層提供超越本地區段的連線能力與路徑選擇，一路從來源端到最終目的端。網路層使用邏輯定址來管理連線。在網路中，邏輯位址用來識別寄件者與收件者。郵政系統是另一個常見的使用位址來識別寄件者與收件者的系統。郵政地址的格式包含姓名、街道名稱與門牌號碼、城市、州別與國家。網路邏輯位址的格式與郵政地址不同，它由網路層的規則所決定。邏輯定址有助於確保主機擁有唯一的位址，或在網路通訊中能被唯一識別。
- Layer 4: The transport layer defines the segmenting and reassembling of data belonging to multiple individual communications, defines the flow control, and defines the mechanisms for reliable transport if required. The transport layer serves the upper layers, which in turn interface with many user applications. To distinguish between these application processes, the transport layer uses its own addressing. This addressing is valid locally, within one host, unlike addressing at the network layer. The transport services can be reliable or unreliable. The selection of the appropriate service depends on application requirements. For instance, the file transfer may be reliable to guarantee that the file arrives intact and whole. On the other hand, a missing pixel when watching a video might go unnoticed. In networking, this is called an unreliable service.第 4 層：傳輸層定義屬於多個個別通訊的資料如何分段與重組，定義流量控制，並在需要時定義可靠傳輸的機制。傳輸層為上層提供服務，而上層又與許多使用者應用程式介接。為了區分這些應用程式處理程序，傳輸層使用自己的定址方式。與網路層的定址不同，這種定址只在單一主機內部有效。傳輸服務可以是可靠的或不可靠的。應選擇哪一種服務取決於應用程式的需求。例如，檔案傳輸可能需要可靠服務，以保證檔案完整無缺地送達。另一方面，觀看影片時少了一個像素可能不會被察覺。在網路中，這稱為不可靠服務。
- Layer 5: The session layer establishes, manages, and terminates sessions between two communicating hosts to allow them to exchange data over a prolonged time period. The session layer is mainly concerned with issues that application processes may encounter and not with lower-layer connectivity issues. The sessions, also called dialogs, can determine whether to handle data in both directions simultaneously or only handle data flow in one direction at a time. It also takes care of checkpoints and recovery mechanisms. The session layer is explicitly implemented with applications that use remote procedure calls.第 5 層：會議層建立、管理並終止兩個通訊主機之間的會議，讓它們能在較長的時間內交換資料。會議層主要關注應用程式處理程序可能遇到的問題，而非下層的連線問題。會議（也稱為對話）可以決定是同時處理雙向資料，還是一次只處理單一方向的資料流。它也負責檢查點與復原機制。會議層明確地實作在使用遠端程序呼叫的應用程式中。
- Layer 6: The presentation layer helps ensure that data sent by the application layer of one system is "readable" by the application layer of another system. It achieves that by translating data into a standard format before transmission and converting it into a format known to the receiving application layer. It also provides special data processing that must be done before transmission. It may compress and decompress data to improve the throughput and may encrypt and decrypt data to improve security. Compression/decompression and encryption/decryption may also be done at lower layers.第 6 層：表現層協助確保某一系統的應用層所送出的資料，能被另一系統的應用層「讀取」。它的做法是在傳輸前將資料轉換成標準格式，再轉換成接收端應用層所認識的格式。它也提供傳輸前必須完成的特殊資料處理。它可以壓縮與解壓縮資料以提升吞吐量，也可以加密與解密資料以提升安全性。壓縮／解壓縮與加密／解密也可能在較低的層執行。
- Layer 7: The application layer is the OSI layer that is closest to the user. It provides services to user applications that want to use the network. Services include email, file transfer, and terminal emulation. An example of a user application is the web browser. It does not reside at the application layer but uses protocols that operate at the application layer. Operating systems also use the application layer when performing tasks triggered by actions that typically do not involve communication over the network. Examples of such actions are opening a remotely located file with a text editor or importing a remotely located file into a spreadsheet. The application layer differs from other layers in that it does not provide services to any other OSI layer.第 7 層：應用層是 OSI 模型中最接近使用者的一層。它為想要使用網路的使用者應用程式提供服務。這些服務包括電子郵件、檔案傳輸與終端機模擬。使用者應用程式的一個例子是網頁瀏覽器。瀏覽器本身並不位於應用層，而是使用在應用層運作的協定。作業系統在執行某些由通常不涉及網路通訊的動作所觸發的工作時，也會使用應用層。這類動作的例子包括用文字編輯器開啟位於遠端的檔案，或將遠端檔案匯入試算表。應用層與其他層的不同之處在於，它不為任何其他 OSI 層提供服務。