Cisco CCNA Semester 1 Chapter 7 Version 3.0

1. Cisco CCNASemester 1 Chapter 7Version 3.0 Prepared and Presented by: Terren L. Bichard

2. Ethernet Technologies • Legacy Ethernet • 10BASE5, 10BASE2, and 10BASE-T • The four common features of Legacy Ethernet are: • timing parameters • frame format • transmission process • a basic design rule.

3. Ethernet Technologies • 10BASE5, 10BASE2, and 10BASE-T all share the same timing parameters • 1 bit time at 10 Mbps = 100 nsec = 0.1 µsec = 1 ten-millionth of a second • Also share the same Frame format

4. Legacy Ethernet Technologies • Legacy Ethernet transmission process is identical until the lower part of the OSI physical layer. • The Layer 2 frame data is converted from hex to binary. • As the frame passes from the MAC sublayer to the physical layer, further processes occur prior to the bits being placed from the physical layer onto the medium.

5. Legacy Ethernet Technologies • One important process is the signal quality error (SQE) signal.  • SQE is always used in half-duplex. • SQE can be used in full-duplex operation but is not required.

6. Legacy Ethernet Technologies • SQE is active: • Within 4 to 8 microseconds following a normal transmission to indicate that the outbound frame was successfully transmitted • Whenever there is a collision on the medium • Whenever there is an improper signal on the medium. • Improper signals might include jabber, or reflections that result from a cable short. • Whenever a transmission has been interrupted

7. 10Mbs Ethernet • All 10 Mbps forms of Ethernet take octets received from the MAC sublayer and perform a process called line encoding. • Line encoding describes how the bits are actually signaled on the wire. • The simplest encodings have undesirable timing and electrical characteristics. • Line codes have been designed to have desirable transmission properties. • This form of encoding used in 10 Mbps systems is called “Manchester.”

8. Manchester Encoding • Relies on the direction of the edge transition in the middle of the timing window to determine the binary value for that bit period. • If the top waveform has a falling edge, it is interpreted as a binary 0. • If the second waveform shows a rising edge, it is interpreted as a binary 1. • (See next slide for graphic.)

9. One Bit Period Falling Edge……… Rising Edge…….. The waveform voltage levels at the beginning or end of any bit period are not factors when determining binary values.

10. Timing Limits • The timing limits are based on parameters such as: • Cable length and its propagation delay • Delay of repeaters • Delay of transceivers • Interframe gap shrinkage • Delays within the station

11. 5-4-3 Rule • 5 segments • 4 repeaters • No more than 3 of the segments may have hosts on them.

12. 10Base5 Ethernet • Up to 10Mbps • 500 meter segments • Used as backbone installations • Cable is thick and heavy • Only operates in half-duplex mode

13. 10Base2 Ethernet • smaller size • lighter weight • greater flexibility • Manchester encoding • Uses BNC connectors • 185 meters • Half-duplex only • Up to 30 stations per segment

14. 10BaseT Ethernet • Cheaper and easier to install than coax • Star Topology • 10 Mbps • 100 meters – (90 Meters horizontal) • Manchester encoding • RJ-45 connectors • Half or full duplex

15. 10BaseT Ethernet • Uses hub or switch between workstations • Bridges and Switches create more and smaller collisions domains • Hubs increase the size of collisions domains

16. 100Mbps Ethernet • 100Base-TX and 100Base-FX • one bit time in 100-Mbps Ethernet is 10nsec = .01 microseconds = 1 100-millionth of a second • two separate encoding steps are used by 100-Mbps Ethernet. • The first part of the encoding uses a technique called 4B/5B • The second part of the encoding is the actual line encoding specific to copper or fiber.

17. 10 Mbps 100Mbps

18. 100Base-TX • Uses 4B/5B encoding, which is then scrambled and converted to multi-level transmit-3 levels or MLT-3.