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T101 Networks

T101 Networks. 2 – Ethernet media. Lesson Objectives. to describe different Ethernet standards to describe Ethernet copper media to describe Ethernet fibre media. What is the Medium?. the media is the thing through which the transmission signal propagates

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T101 Networks

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  1. T101 Networks 2 – Ethernet media

  2. Lesson Objectives • to describe different Ethernet standards • to describe Ethernet copper media • to describe Ethernet fibre media

  3. What is the Medium? • the media is the thing through which the transmission signal propagates • electricity passes through the medium of metal (normally copper) cables • light pulses pass through the medium of fibre optic cables • radio waves pass through space • Ethernet has definitions for copper and fibre optic cables • radio waves are covered by other specifications (IEEE 802.11 or WiFi) and another lecture • IEEE 802.11 and WiFi are not Ethernet standards

  4. Ethernet Evolves • the original commonly accepted Ethernet specification operated at 10 Mbits/s over coaxial cable • current commonly installed Ethernet operates at 100 Mbits/s (to the desktop) and 1 Gigabit/s to server computers • most desktop computers today have gigabit NICs installed • the complete specifications for 10 Gigabit/s Ethernet are still being written but some of the technology is available today

  5. Ethernet Names • the IEEE use a naming convention to specify the speed and media that Ethernet uses 100BaseTX 100 represents the Ethernet speed in Mbits/s the T is short for twisted pair and the X is used to distinguish from T4 and T2 which were other standards which never took off Base means baseband as opposed to broadband transmission which effectively means that the medium only carries Ethernet signals

  6. Ethernet Names 10BaseF how fast is this? the F is short for fibre optic baseband or broadband transmission?Is Ethernet the only signal on this medium?

  7. Ethernet Names 100BaseFX how fast is this? fibre or copper cable? baseband or broadband transmission?Is Ethernet the only signal on this medium?

  8. Ethernet Names 100BaseSX how fast is this? fibre or copper cable? baseband or broadband transmission?Is Ethernet the only signal on this medium?

  9. Copper Cables • in the early days of Ethernet coaxial cables were the only method of connection • two coaxial standards were used and these were • 10Base-5 also called thicknet • 10Base-2 also called thinnet • we are no longer interested in these standards because they are obsolete

  10. 10Base5 “frozen yellow garden hose” made obsolete by 10Base2

  11. 10Base2 • (hand round the 10Base2 kit) • made obsolete by 10BaseT and 100BaseT • when you examine 10Base2 equipment it is very easy to understand that it is a shared medium because there is only one conductor and all devices are connected to it

  12. UTP Cable • Unshielded Twisted Pair cable is the dominant medium in use today • it is found in virtually every single office throughout the world • it is relatively cheap • although modern UTP cable was designed for Ethernet networks (especially 100BaseTX) it has other uses • telephones are usually cabled on Ethernet UTP; in fact UTP was designed for telephones

  13. UTP • “Unshielded” means that there is no metal shield or screen surrounding the conductors • “Twisted Pair” means that the individual cables are twisted together in pairs

  14. TIA/EIA • UTP cable standards used for Ethernet networks are not defined by the IEEE • the TIA/EIA standards body already had cable standards in place (for telephony) by the time Ethernet was ready to use UTP • today TIA/EIA define the cable standards that Ethernet uses • the most commonly used standard of past years has been the Cat 5, the current standard is Category 5E or even Category 6

  15. Cat 3 Standard • Category 3 cables are now considered obsolete • Cat 3 allowed Ethernet to operate at speeds up to 10 Mbits/s (10BaseT) • Cat 3 cable was made obsolete by Cat 5 cable • most offices today will have Cat 5 or better cable installed • Cat 3 cable is not suitable for 100 Mbits/s Ethernet 100BaseTX

  16. Cat 5 Standard • Category 5 cables are no longer installed in new installations, but they are still very common in recent installations • Cat 5 cables have been made obsolete in modern installations by Cat 5e • Cat 5 cables allow transmission up to 1000 Mbits/s (1000BaseT Ethernet) but it is more commonly used for 100 Mbits/s (100BaseT) • Cat 5 is currently “unrecognised” by TIA/EIA

  17. Cat 5e • Category 5e is the minimum specification cable for new installations although some organisations are installing Cat 6 or better • Cat 5e specifies some minor modifications to Cat 5 specifically to allow 1000 Mbits/s (1000BaseT Ethernet) to be more reliable

  18. UTP in Practice • how can you tell the difference between a Cat5, Cat5e and Cat6 UTP cable? • summary of standards and their use

  19. UTP Termination • the TIA/EIA specify how to terminate their UTP (Cat5, 5e, 6 etc) cables • current specifications state that an RJ45 plug is used • the individual cores are colour-coded and have to be terminated in the correct sequence

  20. Cat 5, 5e and 6 • Cat 5, 5e and 6 cables all have 4 pairs of wires (8 wires) • the pairs are colour coded • patch cables are terminated using one of two standard schemes T568A and T568B

  21. T568A and B • T568B is the most commonly found of the two

  22. UTP Cable in 10BaseT and 100BaseT only two pairs are used (although all pairs are always terminated) the data signal is sent down one pair of wires and is received along the other pair the twisted pairs are colour coded – one half of the pair has a solid colour and the other half has the same colour with white; the four pairs are: white/blue & blue white/orange & orange white/green & green white/brown & brown the two pairs that are used in 10BaseT and 100BaseTX are the orange and green pairs 1000BaseT uses all four pairs

  23. UTP Patch Cable

  24. UTP Summary • Cat 5, 5e and 6 have 8 wires that are made into 4 twisted pairs • UTP patch cables are terminated with an RJ45 plug using either T568A or T568B • 100BaseTX and 1000BaseT are the common Ethernet standards that use UTP cables • 10BaseT and 100BaseTX use two of the four pairs; one for transmitting and one for receiving • 1000BaseT uses all four pairs bi-directionally

  25. Fibre Optic Cable • fibre optic cable is a medium made of very pure and very thin glass that is designed to carry light for very long distances • all modern long distance communication today is either achieved using fibre optic cables or radio (satellite or microwave) • fibre optic cables are everywhere and their use continues to grow

  26. Videos • CCNA1_3_2_6_en.swf • CCNA1_3_2_8_en.swf

  27. Fibre Optic v Copper Cables • glass is cheaper than copper but • fibre is awkward, slow and expensive to terminate • copper is much, much easier to terminate • volts are easier to generate than light pulses which require expensive optical devices • light travels further than electricity • Ethernet UTP copper cables only work up to 100m • Ethernet over fibre optic cables can go 50km or more

  28. Ethernet Media

  29. Ethernet Media in Practice • factors shown in the previous comparison mean that UTP copper is used where the distance is 100m or less • fibre optic is only used where the distance in greater than 100m

  30. Fibre Cable Terminators • Ethernet fibre optic cables always come in pairs because one fibre is used for transmission and the other is used for reception • fibre cables have a variety of connectors

  31. Fibre Terminators • ST and SC connectors are two fairly common fibre terminators

  32. Ethernet over Fibre Optic • 100BaseSX is a 100 Mbits/s standard over fibre optic cable • up to 300m distance • uses LEDs and is cheaper than 100BaseFX • 100BaseFX is a 100 Mbits/s standard over fibre optic cable • up to 2km distance • uses lasers and is more expensive than 100BaseSX

  33. Ethernet over Fibre Optic • 1000BaseSX is a 1 Gbit/s standard over fibre optic cable • up to 220m or 500m depending on fibre • uses cheaper optical devices • 1000BaseLX is a 1 Gbit/s standard over fibre optic cable • up to 2km (or 10-20km) depending on fibre • uses lasers and is more expensive than 1000BaseSX

  34. Fibre Optic Summary • fibre optic cable is cheap to produce but very expensive to terminate • optical devices that use fibre optic cables are also expensive • Ethernet over fibre optic is capable of distances up to 70km

  35. Ethernet Summary

  36. How much does fibre cost? • a 1000Base-SX transceiver = $580 • a 1000Base-LX transceiver = $1,157 • a 1000Base-LH transceiver = $6,400 • and you’ll need two of them • and they all look the same!

  37. Transmit and Receive • 10 Mbit/s and 100 Mbit/s Ethernet transmits and receives on different lines 100BaseTX transmits on orange (pins 1+2), receives on green (pins 3+6) 100BaseSX transmits on one fibre, receives on another

  38. Gigabit Ethernet • 1000BaseT Gigabit Ethernet uses all 4 pairs of a Cat5 or Cat5e cable bi-directionally • performance issue • 1000 Mbits/sec = 125 MBytes/sec • PCI bus speed = 133 MBytes/sec (shared) • PCI Express = 250 MBytes/sec (point to point) • therefore the PCI bus is not suitable for Gigabit Ethernet, especially in server computers • Gigabit Ethernet cards should be PCI-E or PCI-X

  39. Summary • Ethernet has many different standards, identified by name such as 100BaseTX • UTP cable consists of 8 wires arranged as 4 twisted pairs • different categories of UTP cable are used for different Ethernet standards • fibre optic cable is used for distances over 100m • fibre optic cable is more expensive to terminate and the optical hardware is more expensive

  40. Homework • watch this video on youtube which shows how a fibre connector is terminated • http://www.youtube.com/watch?v=OosMQHQlY40 • read the Wikipedia article on Fast Ethernet (100BaseTX, 100BaseSX, 100BaseFX) • http://en.wikipedia.org/wiki/Fast_Ethernet • next week: Ethernet hubs and switches

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