- •2 Communicating over the Network
- •2.0 Chapter Introduction
- •2.0.1 Chapter Introduction Page 1:
- •2.1 The Platform for Communications
- •2.1.1 The Elements of Communication Page 1:
- •2.1.2 Communicating the Messages Page 1:
- •2.1.3 Components of the Network Page 1:
- •2.1.4 End Devices and their Role on the Network Page 1:
- •2.1.5 Intermediary Devices and their Role on the Network Page 1:
- •2.1.6 Network Media Page 1:
- •2.2 LaNs, waNs, and Internetworks
- •2.2.1 Local Area Networks Page 1:
- •2.2.2 Wide Area Networks Page 1:
- •2.2.3 The Internet - a Network of Networks Page 1:
- •Internetwork
- •Intranet
- •2.2.4 Network Representations Page 1:
- •2.2.5 Activity - Using NeoTrace™ to View Internetworks Page 1:
- •2.3 Protocols
- •2.3.1 Rules that Govern Communications Page 1:
- •2.3.2 Network Protocols Page 1:
- •2.3.3 Protocol Suites and Industry Standards Page 1:
- •2.3.4 The Interaction of Protocols Page 1:
- •Internetwork Protocol:
- •2.3.5 Technology Independent Protocols Page 1:
- •2.4 Using Layered Models
- •2.4.1 The Benefits of Using a Layered Model Page 1:
- •2.4.2 Protocol and Reference Models Page 1:
- •2.4.3 The tcp/ip Model Page 1:
- •2.4.4 The Communication Process Page 1:
- •2.4.5 Protocol Data Units and Encapsulation Page 1:
- •2.4.6 The Sending and Receiving Process Page 1:
- •2.4.7 The osi Model Page 1:
- •2.4.8 Comparing the osi Model with the tcp/ip Model Page 1:
- •2.5 Network Addressing
- •2.5.1 Addressing in the Network Page 1:
- •2.5.2 Getting the Data to the End Device Page 1:
- •2.5.3 Getting the Data through the Internetwork Page 1:
- •2.5.4 Getting the Data to the Right Application Page 1:
- •2.5.5 Warriors of the Net Page 1:
- •2.6 Chapter Labs
- •2.6.1 Lab: Topology Orientation and Building a Small Network Page 1:
- •2.6.2 Lab: Using Wireshark™ to View Protocol Data Units Page 1:
- •2.7 Chapter Summary
- •2.7.1 Summary and Review Page 1:
- •2.8 Chapter Quiz
- •2.8.1 Chapter Quiz Page 1:
2.4.4 The Communication Process Page 1:
The TCP/IP model describes the functionality of the protocols that make up the TCP/IP protocol suite. These protocols, which are implemented on both the sending and receiving hosts, interact to provide end-to-end delivery of applications over a network.
A complete communication process includes these steps:
1. Creation of data at the Application layer of the originating source end device
2. Segmentation and encapsulation of data as it passes down the protocol stack in the source end device
3. Generation of the data onto the media at the Network Access layer of the stack
4. Transportation of the data through the internetwork, which consists of media and any intermediary devices
5. Reception of the data at the Network Access layer of the destination end device
6. Decapsulation and reassembly of the data as it passes up the stack in the destination device
7. Passing this data to the destination application at the Application layer of the destination end device
2.4.4 - The Communication Process Title: "Untouched Message Travels through a Network" The animation depicts the process of sending a message from a user with a handheld PDA over the network to another user at a desktop PC. The PDA protocol stack is connected to router 1. The desktop PC protocol stack is connected to router 2, and the two routers are connected. The envelope or packet travels from the PDA, down through the layers of its TCP/IP stack (Application to Transport to Internet to Network Access) to router 1. It then travels across the communication link to router 2, and up through the layers of the desktop PC protocol stack to the PC (Network Access to Internet to Transport to Application).
2.4.5 Protocol Data Units and Encapsulation Page 1:
As application data is passed down the protocol stack on its way to be transmitted across the network media, various protocols add information to it at each level. This is commonly known as the encapsulation process.
The form that a piece of data takes at any layer is called a Protocol Data Unit (PDU). During encapsulation, each succeeding layer encapsulates the PDU that it receives from the layer above in accordance with the protocol being used. At each stage of the process, a PDU has a different name to reflect its new appearance. Although there is no universal naming convention for PDUs, in this course, the PDUs are named according to the protocols of the TCP/IP suite.
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Data - The general term for the PDU used at the Application layer
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Segment - Transport Layer PDU
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Packet - Internetwork Layer PDU
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Frame - Network Access Layer PDU
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Bits - A PDU used when physically transmitting data over the medium
2.4.5 - Protocol Data Units and Encapsulation The diagram depicts the use of Protocol Data Units (PDU's) and the encapsulation process when sending a message from a user. The user PC is connected to a router. The PDU terminology is given at each encapsulation step. The process starts when the user creates the email message, which is termed a Data PDU. As the data is passed down the protocol stack, a transport header is added, creating a Segment PDU. Next a network header is added, creating a Packet PDU. Then a frame header and trailer are added, creating a Frame PDU. Finally, the frame is transmitted on the medium as bits (zeros and ones). PDU Summary (passing down the stack): - Data - The general term for the PDU used at the Application Layer. - Segment - Transport Layer PDU - Packet - Internetwork Layer PDU - Frame - Network Access Layer PDU - Bits - PDU used when physically transmitting data over the medium.