Gigabit Ethernet and 10 Gigabit Ethernet signaling

1. Gigabit Ethernet and 10 Gigabit Ethernet signaling Eric Lynskey ECE 734: Sept. 29 and Oct. 2, 2003

2. BS in EE from UNH in 2000 Currently MS student in EE Employed at IOL since Fall 1997 Have been active in FEC, GEC, 10GEC, EFM Interest in physical layer and optical communications Voting member of IEEE 802.3 An editor of IEEE 802.3ae Contact Information Phone is 862-3499 Email is elynskey@iol.unh.edu Speaker Introduction

3. Presentation Goals (mine): • Talk about high speed networking technologies • 1 Gigabit Ethernet (copper and fiber) • 10 Gigabit Ethernet (copper, fiber, and more copper) • Analog and digital signaling characteristics of each • Provide you with some practical experience and knowledge • Generate discussion and questions

4. Presentation Goals (yours): • To learn about high speed networking • System considerations • Design issues • Interesting engineering problems • To get some potential thesis topics • To get involved in the discussion

5. Happy Birthday Ethernet “So in 1973, while searching for a word to describe the medium that would be everywhere, that would be passive and would serve as a medium for the propagation of electromagnetic waves into particular data packets, we took that word [Ethernet] that had fallen into disuse and called it the ether network.” • Invented in May of 1973 by Bob Metcalfe while working for Xerox PARC.

6. History of Ethernet Standards • Sept 1990, 10BASE-T • June 1995, 100BASE-TX • June 1998, 1000BASE-X (gigabit over fiber) • June 1999, 1000BASE-T (gigabit over copper) • June 2002, 10GBASE-R/LX4 (10gig over fiber) • ???? 2004, 10GBASE-CX4 (10gig over twinax) • ???? 200?, 10GBASE-T (10gig over UTP)

7. 802 overview and architecture

8. Ethernet frame format

9. 802.3z Architecture

10. The PCS • Translates the data to be sent into a form suitable for the media (encode/decode) • Zero DC content (DC Balanced) • Rich transition density for clock recovery • Error detection • Adds control characters such as start of packet, end of packet • Performs inverse on the receive side

11. The PMA • Serializes and deserializes (SERDES) parallel data to/from serial data • Serial data is then sent to PMD • PMA may scramble/descramble data to suppress frequency content, or encode data, or increase transition density (long runs of unbroken 1s or 0s may look like DC signal over a short term)

12. Ethernet Encodings • Fast Ethernet 802.3u • 4B/5B and scramble • Gigabit Ethernet 802.3z • 8B/10B • Gigabit Ethernet 802.3ab • Convolutional encoder, Viterbi decoder, scramble • 10Gigabit Ethernet 802.3ae • 8B/10B • 64B/66B and scramble

13. The PMD • Takes the serial data stream(s) from the PMA and drives them onto the media, may require electrical to optical conversion, etc. • When receiving, the PMD may utilize channel equalization techniques to counter distortion of the received signal and error correction techniques to restore damaged bits. • PMD receiver will use a phase lock-loop (PLL) to recover the transmit clock

14. Ethernet Physical Signaling • Ethernet (10BASE-T) - Manchester Encoding • Fast Ethernet (100BASE-TX) – MLT-3 • Fast Ethernet (100BASE-FX) – NRZI • Gigabit Ethernet (1000BASE-T) – 4D PAM5 • Optical Gigabit and 10 Gigabit – NRZ

15. NRZ Data stream

16. 1000BASE-SX Signaling

17. NRZ Eye Diagrams

18. 1000BASE-SX Eye Diagram

19. 1000BASE-T Signaling

20. 802.3z Objectives

21. PHY Block Diagram

22. Fiber optic channel diagram

23. Operating Ranges

24. Different fiber types

25. Total internal reflection

26. Fiber attenuation curve • Transmission windows • 850nm • 1300nm • 1550nm

27. Dispersion

28. Laser Transmitter

29. Laser Receiver

30. The Ten Bit Interface (TBI)

31. Receiver • The receiver recovers the link partner’s transmit clock from the received data stream via a phase locked loop (PLL). • This clock is then used to sample the incoming data at the correct times. • If the timing is off, the received data will be incorrectly interpreted.

32. De-Serialization • The de-serializer samples the serial waveform at 1.25GHz, and assembles a 10 bit parallel words to be transmitted up to the PCS

33. Transmitter • The PMA receives 10 bit words from the PCS at 125 MHz • The PMA must Serialize this 10 bit word, and transmit at 10 times 125 MHz, therefore 1.25 GHz • Works in the same fashion as the de-serializer, just in the opposite way • Could use 20bit words and work at 62.5MHz

34. COMMA Reception • A COMMA is a string of 7 bits inside of a 10 bit word, used for alignment • COMMA + = b’0011111 • COMMA – = b’1100000 • Upon reception of a COMMA, the PMA must realign the current code group (10 bit word) boundary • To realign the code group, the PMA may delete or modify up to four code groups in order to align the correct receive clock and the code group containing the COMMA • COMMAs are transmitted during IDLE periods

35. PCS Block Diagram

36. Purpose of the PCS • The PCS also encodes each octet of data using 8B/10B encoding • The 1000BASE-X PHY, unlike the 10BASE-T PHY, is always generating signaling even when a frame is not being transmitted. The PCS must fit data being passed down from the GMII into this signaling • The PCS ensures the integrity of the channel through the synchronization process

37. Thank you Fibre Channel -8B/10B Encoding • The 1000BASE-X PCS uses 8B/10B encoding, which was originally design to be used for Fibre Channel • 8B/10B encoding maps each octet of data in a frame to one of two possible 10bit code_groups • 8B/10B ensures that there is a density of transitions from 1 to 0 and vice-versa • 8B/10B encoding also allows for the creation of special code_groups

38. Code Groups • Data Code-Groups • Each possible octet value is mapped to two possible 10bit code-groups. Which code-group it maps to depends upon the current running disparity • Special Code-Groups • Special code-groups do not map to a specific octet value • Each special code-group has a unique meaning within the PCS

39. Sample of PCS codes

41. What is 1000BASE-T? • A member of the Gigabit Ethernet family of standards. • Supports the CSMA/CD media access control protocol. • Supports full-duplex data transfer at 1000Mbps. • Supports up to 100m of 4-pair unshielded twisted pair (UTP) cable. • Maintains a bit error rate (BER) better than 10-10. • Meets or exceeds FCC Class A requirements.

42. Unshielded twisted pair (UTP) cable

43. The category system • TIA/EIA-568-A defines a performance rating system for UTP cable and connecting hardware: • Category 3 performance is defined up to 16MHz. • Category 4 performance is defined up to 20MHz. • Category 5 performance is defined up to 100MHz. • 1000BASE-T requires category 5 or better performance.

44. Performance parameters for UTP cable • DC resistance • characteristic impedance and structural return loss • attenuation • near-end crosstalk (NEXT) loss • propagation delay

45. Performance parameters for UTP connecting hardware • DC resistance • attenuation • NEXT loss • return loss

46. Attenuation • Electrical signals lose power while travelling along imperfect conductors. • This loss, or attenuation, is a function of conductor length and frequency. • The frequency dependence is attributed to the skin effect. • Skin Effect: • AC currents tends to ride along the skin of a conductor. • This skin becomes thinner with increasing frequency. • A thinner skin results in a higher loss. • Attenuation increases up to 0.4% per degree Celsius above room temperature (20oC).

47. Attenuation vs. frequency

48. Near-end crosstalk (NEXT) loss • Crosstalk: • Time-varying currents in one wire tend to induce time-varying currents in nearby wires. • When the coupling is between a local transmitter and a local receiver, it is referred to as NEXT. • NEXT increases the additive noise at the receiver and degrades the signal-to-noise ratio (SNR).

49. NEXT loss vs. frequency (pair A)

50. Reflections • When a circuit looks into an electrically long cable, it sees the characteristic impedance of that cable. • Characteristic impedance is defined by the structure of the cable. • An unshielded twisted pair has a characteristic impedance of 100W. • Maximum Power Transfer Theorem: • maximum power is transferred from a source to its load only when the source and load impedances are matched. • When the source and load impedances are not matched, where does the rest of the power go? • Answer: back to the source (a reflection)