1. 1 CSCD 433 Network Programming Fall 2011 Lecture 6 Ethernet Evolution and Performance

2. Topics Ethernet Revisited Faster and Faster Ethernet Up to 10 Gigabit and beyond.... 2

3. Ethernet Performance

4. Ethernet was designed by Bob _________ in 1973, at the Xerox Company in Palo Alto, CA Since the 1970's, Ethernet has become faster Why? Ethernet

5. 1. Changes in physical medium Coaxial, UTP cables, Fiber optic 2. Improved media access control methods CSMA to CSMA/CD to none needed 3. Improved signal encoding methods Manchester encoding to 4B/5B, 8B/10B and more 4. Cables to hubs to switches 5. Mandating Full Duplex Ethernet Speedup

6. History of Ethernet

7. 7 An Introduction of Ethernet The History of Ethernet Technology – 1973, Metcalfe developed Ethernet at Palo Alto. – 1980, Digital, Intel and Xerox developed the standard of 10Mpbs Ethernet. – 1992, the Grand Junction Network Company brought up the structure of 100Mbps Ethernet – 1998, addressed the standard of Gigabit Ethernet – 2002, 10 Gigabit standard http://www.trendcomms.com/multimedia/training/broadband%20networks/web/mai n/ethernet/theme/chapter1/EnetIntroduction.html

8. Classical or Standard Ethernet

9. 9 Categories of Standard Ethernet

10. Ethernet Recap Classic Ethernet One long cable, 500 meter max segment Snaked around building as single, long cable All computers attached Thick Ethernet Began as thick yellow cable, marked every 2.5 meters to show computer attachments Thin Ethernet Thinner, bent more easily connections with BNC connectors Cheaper to install, 185 meter max segment

11. 11 10Base5 implementation Ethernet segment length

12. 12 10Base2 Implementation Ethernet segment length

13. 13 Coaxial cable has single copper conductor at its center A plastic layer provides insulation between center conductor and a braided metal shield Metal shield helps to block any outside interference from fluorescent lights, motors, and other computers Resistant to signal interference and can support greater cable lengths between network devices than twisted pair cable Only half-duplex is possible with coaxial cable! Efficiency Coaxial Cable A: outer plastic sheath B: woven copper shield C: inner dielectric insulator D: copper core

14. 14 10Base-T implementation UTP = Unshielded Twisted Pair

15. 15 Efficiency Twisted Pair Twisted pair cabling comes in two varieties Shielded and Unshielded. Unshielded twisted pair (UTP) is the most popular Cable has four pairs of wires inside jacket Each pair twisted with different number of twists per inch Eliminate interference from adjacent pairs and other electrical devices Tighter twisting, higher supported transmission rate and greater cost per foot Most important Two connections for each host, Full duplex is now possible!

16. 2 Pairs of Wires in a UTP Cable Are Always Used No matter whether the device is a hub or a switch, 2 pairs of wires in a UTP cable are always used to connect a host to the device. 2 pairs 12- 16

17. 17 Efficiency Twisted Pair Category Speed Use 1 1 Mbps Voice Only (Telephone Wire)‏ 2 4 Mbps LocalTalk & Telephone (Rarely used)‏ 3 16 Mbps 10BaseT Ethernet 4 20 Mbps Token Ring (Rarely used)‏ 5 100 Mbps (2 pair) 100BaseT Ethernet 1000 Mbps (4 pair) Gigabit Ethernet 5e 1000 Mbps Gigabit Ethernet 6 10000 Mbps Gigabit Ethernet

18. 18 Ethernet Cabling The most common kinds of Ethernet cabling. Three kinds of Ethernet cabling. (a) 10Base5, (b) 10Base2, (c) 10Base-T. Difference in Segment length Costs Less

19. Ethernet Recap Used Manchester encoding More later.... Ethernet could contain multiple segments and multiple repeaters Used CSMA/CD for shared media What does CSMA/CD stand for? Carrier Sense Multiple Access/Collision Detection Review this...

20. 20 CSMA/CD Protocol All hosts transmit & receive on one channel Packets are of variable size When a host has a packet to transmit 1. Carrier Sense: Check that the line is quiet before transmitting 2. Collision Detection: Detect collision as soon as possible Collision is detected, stop transmitting; wait a random time, then return to step 1. binary exponential backoff

21. 21 Ethernet CSMA/CD algorithm Algorithm 1. NIC receives datagram from network layer, creates frame 2. If NIC senses channel idle, starts frame transmission If NIC senses channel busy, waits until channel idle, then transmits 3. If NIC transmits entire frame without detecting another transmission, NIC is done with frame !

22. Ethernet CSMA/CD algorithm 4. If NIC detects another transmission while transmitting, aborts and sends jam signal 5. After aborting NIC enters exponential backoff after mth collision, NIC chooses a K, small integer, at random from {0,1,2,…,2 m -1} NIC then waits K·512 bit time, Returns to Step 2 22

23. Minimum Frame Size In order to allow collision detection, frames must have a Minimum Frame Size (MFS) Consequently small frames must be padded out to reach MFS MFS (bits) is related to length of the LAN, and transmission rate (bits/sec)‏ Ethernet and Fast Ethernet the MFS is 64 bytes Gigabit Ethernet it is 416 or 520 bytes Full duplex versions of Ethernet Collisions are avoided, and so MFS does not apply!

24. Ethernet Performance One result of sharing“Ether” More stations on an Ethernet network, Higher number of collisions, Worse performance Typical performance 10-Mbps Ethernet network Around 100 stations Supports a bandwidth of only about 40 to 60 percent of the expected value of 10 Mbps How would you increase performance? Fewer Collisions, reduce the collision domain!

25. Fast Ethernet

26. Fast Ethernet 802.3u When switches became popular 10 Mbps Ethernet was standard... back in 1995 How to make Ethernet faster? Fast Ethernet proposed by IEEE Committee Wanted speeds of 100 Mbps Old standard 802.3, New amended standard 802.3u Not really New - Kept everything the same Why might you want to do this? Backward compatibility!!! Golden rule of Computer Science

27. Fast Ethernet Primary concern of Fast Ethernet developers Preserved CSMA/CD medium access method of 802.3 Ethernet while boosting data rate Point is to make it FASTER! Kept frame format Wanted Fast Ethernet fit within traditional Ethernet installations One version of the Fast Ethernet standard runs on older Category 3 cable installations.

28. Fast Ethernet Another important idea Multiple Ethernet types, 10 and 100 Mbps could coexist How? A Fast Ethernet-compatible hub does speed matching when exchanging frames Has auto-negotiate feature Devices detect speed of incoming transmissions and adjust appropriately

29. 29 IEEE 802.3u - Fast Ethernet Technically IEEE 802.3u is not a new standard, but an addendum to IEEE 802.3 standard. Transmission rate is 100 Mbps. Fast Ethernet is only defined for star topology LANs (i.e., shared-medium hubs and switching hubs). Uses category 3 and category 5 UTP, STP, and fibre cables.

30. Fast Ethernet Four Schemes 100Base-TX Runs on two pairs of Category 5 data-grade twisted-pair wire, max distance 100 meters between hub and workstation 100Base-T4 Runs on four pairs of cable, including Category 3 cable, max distance 100 meters between hub and workstation 100Base-FX Runs on optical cable at distances up to 2 kilometers, used to connect hubs over long distances in a backbone configuration 100Base-SX Called Short Wavelength Fast Ethernet, for a Fast Ethernet over fiber-optic cable using 850 nm wavelength optics

31. Fiber Optic Cabling Fiber optic cabling consists of center glass core surrounded by layers of protective materials Fiber optic cable transmits signals over longer distances than coaxial and twisted pair Signals consist of light instead of electrical pulses Has capability to carry information at greater speeds Center core of fiber cables is made from glass or plastic fibers, plastic coating then cushions fiber center, and kevlar fibers help to strengthen cables and prevent breakage Outer insulating jacket made of teflon or PVC

32. Fiber Optic Cabling Two types of fiber cables Single mode Multimode Multimode cable has larger diameter, allows light take different paths, has more trouble with attenuation Both cables provide high bandwidth at high speeds Single mode can provide more distance, but it is more expensive

33. Fast Ethernet Higher frequency used in Fast Ethernet standard is prone to attenuation, Cable distance is more limited than in old Ethernet 10Base-T If encoding scheme of traditional Ethernet were used with Fast Ethernet, High-end frequency would be above 200 Mhz Double maximum frequency rating of Category 5 cable New encoding schemes were implemented to allow higher-frequency transmissions

34. Encoding Schemes for Ethernet Manchester Encoding Standard Ethernet Synchronous clock encoding technique used by physical layer Recall, Manchester encoding 0 is indicated by a 0 to 1 transition at center of bit 1 is indicated by a 1 to 0 transition at center of bit Manchester encoded signal contains frequent level transitions... allows receiver to extract the clock signal and correctly decode the value and timing of each bit

35. Manchester Encoding Up transition = 1 Down transition = 0 Manchester Encoding Standard Ethernet

36. Drawback Manchester encoding can consume up to approximately twice bandwidth of original signal (20 MHz)‏ Penalty for introducing frequent transitions For a 10 Mbps LAN, the signal spectrum lies between the 5 and 20 MHz Additional bandwidth is not significant issue for coaxial cable transmission, but CAT5e cable bandwidth more limited Needed more efficient encoding method

37. Fast Ethernet Encoding 4B/5B encoding is a type of 'Block coding' Processes groups of bits rather than outputting a signal for each individual bit (as in Manchester encoding)‏ Group of 4 bits encoded so that an extra 5th bit is added

38. 4B/5B encoding (Frame Encoding – shorthand)‏ All data is encoded prior to transmission Every 4 bit group (16 different combinations) is mapped onto a 5 bit code (symbol) 5B symbols for 4B data groups are chosen such that a maximum of 2 successive zeros occur 5B symbols which are not used for data encoding are used as control symbols - symbols such as 0001, 00010... are not used Multi-Level Transmit-3 levels No transition = 0 Any transition (up or down) = 1 Reduces frequency of signal Fast Ethernet Encoding

39. Thus, 100 Mbps transmission Uses a 4b/5b MLT code Uses three signal levels and allows a 100 Mbps signal to occupy only 31 MHz of bandwidth Gigabit Ethernet Uses five levels and 8b/10b encoding, to provide even more efficient use of the limited cable bandwidth, 1 Gbps within 100 MHz of bandwidth

40. Fast Ethernet Fast Ethernet supports Full-Duplex switched mode to provide even better performance A full-duplex nonshared link Don't need CSMA/CD Each end system has its own channel Collision detection and loopback functions can be disabled If both end systems are transmitting at same time, combined data rate is 200 Mbps

41. All Gigabit Ethernet

42. Gigabit Ethernet Yet, more speed More modified standards, 1998 - 1999 802.3z which required optical fiber and 802.ab over UTP Gigabit Ethernet is 1 Gbps or 1,000 Mbps extension of IEEE 802.3 Ethernet networking standard Primary niches corporate LANs, campus networks, and service provider networks Can be used to tie together existing 10 and 100 Mbps Ethernet networks Gigabit Ethernet competes with ATM (Asynchronous Transfer Mode) as core networking technology Many ISPs use Gigabit Ethernet in their data centers

43. Gigabit Ethernet Extensions Gigabit Ethernet Required Changes 1. Increased frame size beyond 1500 bytes Can have Jumbo frames of up to 9000 bytes Idea is that at higher speeds it makes sense to have larger frames Transmitting larger frames means fewer CPU interrupts and more data getting through instead of more headers

44. Gigabit Ethernet Extensions Also, mixing classic Ethernet with Gigabit Ethernet buffer overruns are likely So, flow control is supported One end sends control frame telling it to pause for a time

45. Pause Function Implement a simple “stop-start” flow control scheme If a device wants to temporarily inhibit incoming frames, it sends a PAUSE frame to the full-duplex partner PAUSE frame contains a parameter indicating the length of time the partner should wait before sending more frames 12- 45

46. 10 Gigabit Ethernet

47. 47 Easy Migration to Higher Performance 10 Gigabit Ethernet – Is simplest way to scale enterprise and service provider (SP) networks – Leverages installed base of more 300 million Ethernet switch ports – Supports all data services – Supports local, metro, and wide area networks

48. 48 Easy Migration to Higher Performance – Is faster, cheaper, and simpler than alternatives – Optionally matches MAN/WAN backbone speed of OC-192 Promises ability for Ethernet to use SONET/SDH for Layer1 transport across WAN transport backbone SONET: Synchronous Optical NETwork SDH: equivalent Synchronous Digital Hierarchy network

49. 49 Low Cost of Ownership Each new generation of Ethernet provides 10 times the bandwidth at only three to four times the cost of the previous generation 10 Gbps WAN PHY links will cost less than 10 Gbps OC-192c links – 10 Gbps WAN PHY is an asynchronous Ethernet link – SONET/SDH is difficult, expensive to implement timing and jitter requirement

50. 50 Ethernet Economics

51. 51 Application for 10 Gigabit Ethernet 10 Gigabit Ethernet in LAN 10 Gigabit Ethernet in MAN 10 Gigabit Ethernet in WAN 10 Gigabit Ethernet in SAN

52. 52 10 Gigabit Ethernet in LAN Campus Backbone – Higher speed links Inter-Campus – Long distance connectivity Server Farm – Higher bandwidth content – Broadband Access driven demand to & from servers

53. 53 10 Gigabit Ethernet in LAN(cont.)‏ Extended Storage Area Networks – Meeting SAN QoS requirements across WANs Removal of LAN bottlenecks Eliminate of 1Gbps link aggregation issues

54. 54 10 Gigabit Ethernet in LAN(cont.)‏

55. 55 10 Gigabit Ethernet in MAN

56. 56 10 Gigabit Ethernet in WAN

57. 57 10 Gigabit Ethernet in WAN(cont.)‏ Seamless access to the optical infrastructure Simple, very high speed, low cost inter/intra- PoP connection

58. References Encoding Schemes (very thorough)‏ http://gbenthien.net/encoding.pdf Cabling http://fcit.usf.edu/network/chap4/chap4.htm Ethernet Encoding Schemes http://fengnet.com/book/CNF/ch02lev1sec1.ht ml

59. Summary Ethernet has evolved over many years Physical cabling, changes in encoding, changing Media Access has allowed Ethernet to change with changes in technology Managed to maintain its cost-effectiveness in the face of competing technologies

60. 60 Assignment P roblems from the Book