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This is a brief discussion on data encapsulation according to Cisco Certified Network Associate (CCNA) Exam. Let me start; when a host sends out data on a network to receiving device, the data travels from first to last in encapsulation form. It is covered with protocol information at every layer of the OSI model. Each layer communicates just with its neighbor layers on the receiving device. Every layer works with Protocol Data units (PDUs) to converse the information. PDUs grasp the control information fasten to the data at each layer of the OSI model. They are normally fasten to the header in front of the data field but can also be attached in the trailer or end of it. Every Protocol Data unit (PDU) fixes to the data by encapsulating it at every layer of the OSI model and each has a particular name (depending on the information provided in each header). On the receiving device, every neighbor layer just can read this PDU information. And after reading this information is stripped off and then the data is handed to the next upper layer.

Data Link layer performs the process of combination of bits into bytes and bytes into frames. So, Data Link layer employs frames to summarize the packets which were received from the Network Layer for transmitting on a sort of media access. The function of Ethernet stations is to pass data frames between each other using a group of bits recognized as a MAC frame format. This detects errors from a Cyclic Redundancy Check (CRC) (Remember this is error detection, not error correction). The 802.3 frames and Ethernet frame are shown below. NOTE: Encapsulating a frame within a different type of frame is called tunneling.

Digital, Intel and Xerox (DIX) group firstly deployed the Ethernet. DIX group very first created and deployed the first Ethernet LAN Specification which the IEEE used to create the IEEE 802.3 committee. It was 10Mbps network which ran on coax, then ultimately on twisted pair and fiber media. Later, the IEEE expanded the 802.3 Committee into two new committees recognized as 802.3u (Fast Ethernet) and 802.3ab (Gigabit Ethernet on category 5) and then eventually 802.3ae (10Gbps over fiber and coax). Whenever you've to design a Local Area Network (LAN), you must have to be aware of the multiple kinds of Ethernet media available to you. Well, I suggest you to use Gigabit Ethernet to each desktop and 10Gbps between switches. Because, if you combine and match up the multiple kinds of Ethernet media techniques presently obtainable, you can arise with a cost effective network solution which works great. The following table describes the IEEE 802.3 and original Ethernet Physical layer specifications.

Hierarchy is a collection of items. Items being represent as above and beneath in hierarchy or sometimes at the same stage as one another. Theoretically, a hierarchy can be replicated technically as a originate ranking; the origin ranking forms the upper stage and the broods of a certain highest point are at the same stage, beneath their frequent parent. A hierarchy can connect body units whichever vertically or horizontally and directly or indirectly. Direct connections of the hierarchy insofar as they are hierarchical are to individual superior or to any of individual subordinates, while a structure which is mostly hierarchical can also contain different hierarchies.