The Rules that Govern Communication
A set of interconnection protocols needed to perform communication functions is called a protocol suite. Protocol suites are implemented in software, hardware, or both through hosts and networking devices.A great way to visualize how a suite interacts is to look like a stack. A protocol stack shows how the individual protocol is implemented in a suit. The protocols are viewed in layers, each with a high level of service depending on the functionality specified by the protocol shown at the bottom.
The bottom layers of the stack relate to transmitting data over the network and providing services to the upper layers, which focus on the content being sent.As the data suggests, we can use layers to describe the activity that takes place as an example of a face-to-face interaction. At the bottom, the physical layer, we have two people, each with a voice that can say words in a loud voice. In the middle, the layer of rules, we have a contract to speak in a common language. At the top, the layer of content, are the words that are actually spoken. This is the content of the conversation.
At the human level, some communication rules are formal and others are simply understood according to custom and practice. For the devices to communicate successfully, a suite of network protocols must describe specific requirements and interactions . Some common networking protocols are the Hypertext Transfer Protocol (HTTP), the Transmission Control Protocol (TCP), and the Internet Protocol (IP)
Note: IP in this course refers to the IPv4 and IPv6 protocols. IPv6 is the most recent version of IP and the most common replacement for IPv4.The figures illustrate networking protocols that describe the following processes:How the message is formatted or structured, as shown in Figure 1.The process by which network devices share information about pathways with other networks, as shown in
How and when error and system messages are passed between devices .The configuration and the end of the data transfer sessions
Communication between a web server and a web client is an example of interaction between several protocols. The protocols shown in the figure include:
HTTP – is an application protocol that controls how web servers and web clients interact. Specifies the content and formatting of HTTP requests and responses that are exchanged between the client and the server . HTTP depends on the other protocol to govern how messages are transmitted between client and server.
TCP – A transport protocol that organizes individual conversations. The TCP divides HTTP messages into smaller pieces, called classes. These segments are sent between the destination server’s web server and the client process. TCP is also responsible for controlling the size and rate of messages exchanged between the server and the client.
Ethernet – is a network access protocol that defines two basic functions: communication over a data link and the physical transmission of data over network media. Network access protocols are responsible for formatting packets and transmitting media.
Suites of Industry Protocols and Standards
A suite of protocols is a set of protocols that work together to provide comprehensive network communication services. A suite of protocols can be specified by a standards organization or developed by a supplier. The protocol suites, like the four illustrated in the figure, can be a bit overwhelming. However, this course will only cover the protocols of the TCP / IP protocol suite.The TCP / IP protocol suite is an open standard . A standards-based protocol is a process that has been approved by the networking industry and approved by a standards body.
The use of standards in the development and implementation of protocols ensures that products from different manufacturers can interact successfully .Some protocols are proprietary, which means that a company or a supplier controls the definition of the protocol and its functioning. AppleTalk and Novell Netware are examples of proprietary protocols, which are legacy protocol suites. It is not uncommon for a supplier (or group of suppliers) to develop a proprietary protocol to meet the needs of its customers and later help make this proprietary protocol an open standard.
Development of TCP / IP
The first packet switching network and provider on the Internet today was the Advanced Research Projects Agency Network (ARPNET), which came to life in 1969 by connecting mainframe computers to four locations. Urpenet was funded by the US Department of Defense for use by universities .
The TCP / IP protocol suite.
Some of the more famous people are shown in the figures. Click on each protocol to see the translation and description of the acronym. Individual protocols are configured in layers using the TCP / IP protocol model: Application, Transport, Internet and Network Access Layer. TCP / IP protocols are specific to application, transport, and Internet layers. Network access layer protocols are responsible for delivering IP packets to the physical medium. These lower-level protocols are developed by various standard organizations.
The TCP / IP protocol suite is implemented as a TCP / IP stack on both sending and receiving hosts so that applications can be delivered from end to end on a network. Ethernet protocols are used to transmit IP packets to the physical medium used by LAN.research laboratories.
TCP / IP Communication Process
Figures illustrate the complete communication process using an example of a web server transmitting data to a client. This process and protocols will be discussed in more detail in the following chapters.1. In Figure , the animation begins when the Web server prepares the Hypertext Markup Language (HTML) page as data to send.2. The HTTP header of the application protocol is added to the beginning of the HTML data. The header contains various information, including the HTTP version that the server uses and a status code indicating that it contains information for the web client.3.
The HTTP application layer protocol provides web page data in HTML format to the transport layer. The TCP transport layer protocol is used to manage individual conversations, in this example between the web server and the web client.4. Next, the IP information is added to the beginning of the TCP information . This information is called IP packets.5. The Ethernet protocol adds information to both ends of the IP packet, called a data link frame. This frame is delivered to the nearest router along the way to the web client.
Each router removes and adds new data link information before transmitting the packet.6. These data are now transported via the internetwork, which consists of media and intermediate devices.7. The animation begins when the client receives the data link frames that contain the data. Each protocol header is processed and then deleted in the reverse order of its addition. Ethernet information is processed and deleted, followed by IP protocol information, TCP information, and finally HTTP information.8. The information on the web page is then transmitted to the client’s web browser software.