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Chapter 9 - Ethernet

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Chapter 9 - Ethernet

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Xác định các đặc điểm cơ bản của phương tiện truyền thông mạng được sử dụng trong Ethernet. Mô tả các tính năng liên kết vật lý và dữ liệu của Ethernet. Mô tả chức năng và đặc điểm của phương pháp kiểm soát truy cập phương tiện truyền thông được sử dụng bởi giao thức Ethernet. Giải thích tầm quan trọng của lớp 2 địa chỉ được sử dụng để truyền dữ liệu và xác định các loại khác nhau của địa chỉ mạng lưới hoạt động tác động và hiệu suất. So sánh và tương phản ứng dụng...

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Nội dung Text: Chapter 9 - Ethernet

Chapter 9 - Ethernet CCNA Exploration 4.0 Học viện mạng Bách khoa - Website: www.bkacad.com
Overview • Identify the basic characteristics of network media used in Ethernet. • Describe the physical and data link features of Ethernet. • Describe the function and characteristics of the media access control method used by Ethernet protocol. • Explain the importance of Layer 2 addressing used for data transmission and determine how the different types of addressing impacts network operation and performance. • Compare and contrast the application and benefits of using Ethernet switches in a LAN as apposed to using hubs. • Explain the ARP process. H c vi n m ng Bách khoa - Website: www.bkacad.com
Physical and Data Link Features of Ethernet • Standards and Implementation H c vi n m ng Bách khoa - Website: www.bkacad.com
Physical and Data Link Features of Ethernet IEEE (Electrical and Electronics Engineers) Standards • The first LAN is the original version of Ethernet. Robert Metcalfe and his coworkers at Xerox designed it more than thirty years ago. The first Ethernet standard was published in 1980 by a consortium of Digital Equipment Corporation, Intel, and Xerox (DIX).It was released as an open standard. The first Ethernet standard products were sold in the early 1980s. • In 1985, the IEEE standards committee for Local and Metropolitan Networks published standards for LANs. These standards start with the number 802, and 802.3 is for Ethernet. To compare to the International Standards Organization (ISO) and OSI model, the IEEE 802.3 standards had to address the needs of Layer 1 and the lower portion of Layer 2 of the OSI model. As a result, some small modifications to the original Ethernet standard were made in 802.3. • Ethernet operates in the lower two layers of the OSI model: the of the Data Link layer and the Physical layer. H c vi n m ng Bách khoa - Website: www.bkacad.com
Physical and Data Link Features of Ethernet H c vi n m ng Bách khoa - Website: www.bkacad.com
Physical and Data Link Features of Ethernet H c vi n m ng Bách khoa - Website: www.bkacad.com
Physical and Data Link Features of Ethernet • Media Access Control (MAC) is the lower Ethernet sublayer of the Data Link layer. MAC is implemented by hardware, typically in the computer Network Interface Card (NIC). • The Ethernet MAC sublayer has two primary responsibilities: – Data Encapsulation – Media Access Control • Logical Topology: all the nodes (devices) in that network segment share the medium. This requires examining the addressing in the frame provided by the MAC address, and using of CSMA/CD. H c vi n m ng Bách khoa - Website: www.bkacad.com
Physical and Data Link Features of Ethernet H c vi n m ng Bách khoa - Website: www.bkacad.com
Physical and Data Link Features of Ethernet • Most of the traffic on the Internet originates and ends with Ethernet connections. Since its inception in the 1970s, Ethernet has evolved to meet the increased demand for high-speed LANs. When optical fiber media was introduced, Ethernet adapted to this new technology to take advantage of the superior bandwidth and low error rate rate that fiber offers. Today, the same protocol that transported data at 3 Mbps can carry data at 10 Gbps. • The success of Ethernet is due to the following factors: – Simplicity and ease of maintenance – Ability to incorporate new technologies – Reliability – Low cost of installation and upgrade H c vi n m ng Bách khoa - Website: www.bkacad.com
Physical and Data Link Features of Ethernet H c vi n m ng Bách khoa - Website: www.bkacad.com
Characteristics of Network Media used in Ethernet H c vi n m ng Bách khoa - Website: www.bkacad.com
Characteristics of Network Media used in Ethernet • Early Ethernet Media: Coaxial cable – Logical and physical bus topology – 10BASE5, or Thicknet, used a thick coaxial that allowed for cabling distances of up to 500 meters before the signal required a repeater. – 10BASE2, or Thinnet, used a thin coaxial cable that was smaller in diameter and more flexible than Thicknet and allowed for cabling distances distances of 185 meters. • Now, it was replaced by UTP cables. – The UTP cables were easier to work with, lightweight, and less expensive. – Physical topology was a star topology using hubs. Hubs concentrate connections. Any single cable to fail without disrupting the entire network. However, repeating the frame to all other ports did not solve the issue of collisions. H c vi n m ng Bách khoa - Website: www.bkacad.com
Characteristics of Network Media used in Ethernet Legacy Ethernet • In 10BASE-T networks, typically using a hub. This created a shared media. Only one station could successfully transmit at a time: half- duplex communication. • More devices, more collisions. • Using CSMA/CD to manage collisions, with little or no impact on performance. As the number of devices and subsequent data traffic increase, however, the rise in collisions can have a significant impact on the user's experience. H c vi n m ng Bách khoa - Website: www.bkacad.com
Characteristics of Network Media used in Ethernet Current Ethernet • 100BASE-TX Ethernet. Switches replace hubs • Switches can control the flow of data by isolating each port and sending a frame only to its proper destination (if the destination is known), rather than send every frame to every device. • The switch reduces or minimizes the possibility of collisions. • Support full-duplex communications (transmit and receive signals at the same time) • 1Gbps Ethernet and beyond. H c vi n m ng Bách khoa - Website: www.bkacad.com
Characteristics of Network Media used in Ethernet • The applications tax even the most robust networks. For example, the increasing use of Voice over IP (VoIP) and multimedia services requires connections that are faster than 100 Mbps Ethernet. • 1000 Mbps (Gigabit) Ethernet is used. • Some of the equipment and cabling in modern, well-designed and installed networks may be capable of working at the higher speeds with only minimal upgrading. This reduces the total cost. H c vi n m ng Bách khoa - Website: www.bkacad.com
Characteristics of Network Media used in Ethernet • The increased cabling distances enabled by the use of fiber-optic cable in Ethernet-based networks has resulted in a blurring of the distinction between LANs and WANs. Ethernet was initially initially limited to LAN cable systems within single buildings, and then extended to between buildings. It can now be applied across a city in what is known as a Metropolitan Area Network (MAN). H c vi n m ng Bách khoa - Website: www.bkacad.com
Ethernet Frame H c vi n m ng Bách khoa - Website: www.bkacad.com
Layer 2 addressing and its Impact on Network Operation and Performance • The Frame – Encapsulating the Packet H c vi n m ng Bách khoa - Website: www.bkacad.com
Ethernet frame structure •The Preamble is used for timing synchronization in the asynchronous 10 Mbps and slower implementations of •10101011 10101011 Ethernet. Faster versions of Ethernet are synchronous, and this timing information is redundant but retained for compatibility •The Destination Address field contains the MAC destination address. It can be unicast, multicast (group), or broadcast (all nodes) •The source address is generally the unicast address of the transmitting Ethernet node (can be virtual entity – group or multicast) H c vi n m ng Bách khoa - Website: www.bkacad.com
Ethernet frame structure •The type value specifies the Length if value < 1536 decimal, upper-layer protocol to receive (0x600) need LLC to identify the data after Ethernet processing is completed. upper protocol •The length indicates the number of bytes of data that follows this field. (so contents of the Data field are decoded per the the protocol indicated) •The maximum transmission unit (MTU) for Ethernet is 1500 octets, so the data should not exceed that size •Ethernet requires that the frame be not less than 46 octets or 4 more than 1500 octets (Pad is bytes required if not enough data) CRC •Type if value => 1536 decimal, (0x600) it identify upper protocol H c vi n m ng Bách khoa - Website: www.bkacad.com

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