Lecture CCNA Exploration 4.0 (Kỳ 3) - Chapter 2: Basic switch concepts and configurations

This chapter summarize the operation of Ethernet as defined for 100/1000 Mbps LANs in the IEEE 802.3 standard. Explain the functions that enable a switch to forward Ethernet frames in a LAN. Configure a switch for operation in a network designed to support voice, video, and data transmissions. Configure basic security on a switch that will operate in a network designed to support voice, video, and data transmissions.
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Lecture CCNA Exploration 4.0 (Kỳ 3) - Chapter 2: Basic switch concepts and configurations Chapter 2: Basic switch concepts and configurations CCNA Exploration 4.0 1 Overview Học viện mạng Bach Khoa - Website: www.bkacad.com 2 Key elements of Ethernet/802.3 networks Học viện mạng Bach Khoa - Website: www.bkacad.com 3 Media Access Control (MAC) Deterministic, Non-Deterministic •MAC refers to protocols that logical bus determine which computer topology and on a shared-medium physical star or environment, or collision extended star domain, is allowed to transmit the data. •MAC, with LLC, comprises logical ring the IEEE version of the OSI topology and a Layer 2 physical star topology •There are two broad categories of Media Access Control, deterministic (taking turns) and non-deterministic logical ring (first come, first served) topology and physical dual-ring topology Học viện mạng Bach Khoa - Website: www.bkacad.com 4 CSMA/CD • CSMA/CD used with Ethernet performs three functions: listen-before-transmit 1. Transmitting and receiving data packets 2. Decoding data packets and checking them for Transmitting& valid addresses before listening. passing them to the upper layers of the OSI model 3. Detecting errors within data packets or on the network Học viện mạng Bach Khoa - Website: www.bkacad.com 5 CSMA/CD Học viện mạng Bach Khoa - Website: www.bkacad.com 6 Backoff •After a collision occurs and all stations allow the cable to become idle (each waits the full inter-frame spacing) •The stations that collided must wait an additional and potentially progressively longer period of time before attempting to retransmit the collided frame •The waiting period is intentionally designed to be random •If the MAC layer is unable to send the frame after 16 attempts, it gives up and generates an error to the network layer Học viện mạng Bach Khoa - Website: www.bkacad.com 7 Extra: Backoff • The stations involved in transmitting frames at the time of the collision must then reschedule their frames for retransmission. The transmitting stations do this by generating a period of time to wait before retransmission, which is based on a random number chosen by each station and used in that station's backoff calculations. • k= min(n,10) ; n= the number of transmission attempts • 0Ethernet Slot Time Học viện mạng Bach Khoa - Website: www.bkacad.com 9 Ethernet Slot Time Học viện mạng Bach Khoa - Website: www.bkacad.com 10 Ethernet Communications Học viện mạng Bach Khoa - Website: www.bkacad.com 11 Remind Học viện mạng Bach Khoa - Website: www.bkacad.com 12 Ethernet frame structure •At the data link layer the frame structure is nearly identical for all speeds of Ethernet from 10 Mbps to 10,000 Mbps •At the physical layer almost all versions of Ethernet are substantially different from one another with each speed having a distinct set of architecture design rules •The Ethernet II Type field is incorporated into the current 802.3 frame definition. The receiving node must determine which higher-layer protocol is ...