10- and 100-Mbps Ethernet

Transcription

1 Ethernet Basics

2 10-Mbps Ethernet Three 10-Mbps Ethernet standards: 10BASE5 10BASE2 10BASE-T 10BASE2 and 10BASE5 were around more than 20 years and have been replaced by newer alternatives 10BASE-T s use is declining, but it is still used it some networks

3 Comparing 10-Mbps Ethernet Options

4 10-Mbps Ethernet 10-Mbps Ethernet standards cover all of IEEE OSI physical layer (Layer 1) standards and the lower half of the OSI Layer 2 (the MAC sublayer) IEEE Logical Link Control (LLC) defines the upper sublayer of OSI Layer 2 for Ethernet

5 Ethernet Standards and the OSI Layers

6 10-Mbps Ethernet 10BASE5, 10BASE2, and 10BASE-T all use different physical layer specifications All three types share the same settings for timing-related features There are also three types of frames allowed on an Ethernet network

7 Ethernet Framing Review

8 10-Mbps Ethernet All three 10-Mbps Ethernet options use a logical bus topology All three 10-Mbps Ethernet options use asynchronous transmission logic (do not send any signals when idle) Receivers must synchronize themselves to the sender each time a device sends a frame; done by using the Preamble and Start Frame Delimiter (SFD)

9 10-Mbps Ethernet Other key features identical across all types of 10-Mbps Ethernet: Shared medium CSMA/CD and half duplex Design rules about the number of hubs or repeaters between two end-user devices Timing parameters Frame format Logical bus topology Asynchronous transmission silence between frames

10 10BASE-T Approved in 1990 Similar to 10BASE2 and 10BASE5 Major change from the physical bus topology Uses a physical star and UTP cabling In 1997, full duplex standard was approved, allowing simultaneous transmission and reception of signals by a device, which significantly increases performance

11 10BASE-T Wiring Supports Categories 3, 5, and 5e unshielded twisted-pair (UTP) cabling Works better with Cat5 than Cat3 Current installations of cabling are at least Cat5e which will allow support of Gigabit Ethernet

12 Using a Straight-Through UTP Cable

13 10BASE-T Wiring Straight-through cables are used to connect a NIC to a hub The NIC s transmit pins (1 and 2) are connected to the hub s receive pins (1 and 2) The NIC s receive pins (3 and 6) are connected to the hub s transmit pins (3 and 6)

14 TIA- Standard Pinouts

15 TIA/EIA 568A Pinouts

16 10BASE-T Wiring Hubs and switches are often connected together to forward data This type of connection requires a crossover cable The same cable can be used to connect two PCs directly without using a hub or switch

17 10BASE-T Crossover Cable

18 10BASE-T Design: Using Hubs, CSMA/CD, and Half Duplex 10BASE2, 10BASE5, and 10BASE-T all use the same CSMA/CD algorithm to avoid and recover from collisions 10BASE-T requires CSMA/CD when using hubs, but usually not when using switches

19 10BASE-T Design: Using Hubs, CSMA/CD, and Half Duplex: the 5,4,3 Rule Key design rule when using hubs: Between any two devices on a LAN, there can be at most Five cable segments Four hubs Three LAN segments with devices attached to them

20 Example of a Long Delay for Hearing a Collision

21 The Rule Makes sure that CSMA/CD works correctly by ensuring a collision can be heard in a reasonable amount of time A collision fragment must propagate back to the sending device for it to know there has been a collision The delay for the electricity to get from the collision point back to the sending device is affected distance, cable type and any repeaters or hubs in the path

22 The Rule Each repeater or hub adds to the delay All 10-Mbps Ethernet network standards require that a frame be able to go from one end of the network and back to the other in 50 microseconds In today s network designs, hubs are

23 Good Design Practice with 10BASE-T Hubs

24 10BASE-T Design: Using Switches The exclusive use of switches eliminates the rule s restrictions Switches have small collision domains If collisions can t occur, rule is not needed

25 Using Switches to Create Many Smaller Collision Domains

26 10BASE-T Design: Using Switches In the previous slide, each collision domain is a cable up to 100 meters long, with no hosts attached; no collisions occur 1997 IEEE802.3i standard defines full duplex with these restrictions Ethernet switches/bridges must be used (no hubs/repeaters Only two Ethernet interfaces can be in the same collision domain

27 10BASE-T Design: Using Switches Full duplex more than doubles the bandwidth Devices on either end of a cable can send at the same time CSMA/CD can be disabled Collisions cannot occur, so no collision waste

28 100-Mbps Ethernet In the 1990s, use of 10BASE-T LANs grew rapidly (cheaper to install) The Internet grew quickly, about 10% per month Eventually, 10Mpbs to the desktop was not fast enough

29 100-Mbps Ethernet: 100BASE-TX The Fast Ethernet family was introduced in BASE-TX (IEEE 802.3u), which specifies Cat5 copper cabling, became widely popular The 100BASE-T standard, using Cat3 cabling, was not widely supported

30 100-Mbps Ethernet: 100BASE-TX 10BASE-T and 100BASE-TX Equivalent Features Support CSMA/CD and half duplex Support autonegotiation today Use Cat5/5e cabling Have same cable length restrictions Use same Ethernet frame format Use most of the same timing parameters Use the same RJ-45 pinouts Can disable CSMA/CD and use full duplex

31 100-Mbps Ethernet: 100BASE-TX 10BASE-T and 100BASE-TX differences Relate to physical layer 100BASE-TX transmits data at 100 Mbps, ten times faster than 10BASE-T 100BASE-TX is synchronous (always sending some bits, even when idle) The bit-time of 100BASE-TX is 1/10 th the bit-time of 10BASE-T

32 Common Ethernet Timing Settings for 100 Mbps Ethernet Standards

33 Designing Ethernets with Two Speeds Autonegotiation allows NIC and switch ports to use either 10 or 100 Mbps and either half or full duplex Mixed speeds were common on LANs Today, mixed speeds are more likely to be 100 Mbps and 1 Gbps

34 Typical 10/100 Ethernet Design

35 Designing Ethernets with Two Speeds Autonegotiation provides design and upgrade flexibility NICs can be used that support only 10 Mbps, 10 or 100 Mbps, or only 100 Mbps Upgrades do not have to be completed over one weekend Note: Hubs cannot be used in this design

36 100BASE-FX Can run longer distances than 100BASE-TX Often used between buildings on a campus 100 Mbps speed Fiber Distributed Data Interface (FDDI) was also popular

37 Backbone Design Using FDDI

38 100BASE-FX Asynchronous Transfer mode (ATM) became popular in the mid-1990s Took place of FDDI equipment Equipment overhead caused some inefficiencies 100BASE-FX allowed similar cabling distances and speeds as FDDI, overcame some of the inefficiencies

39 100BASE-FX 100BASE-FX was not as popular as 100BASE-TX because: Not enough benefit seen in replacing existing FDDI backbones ATM allowed higher transfer speeds (155 or 622 Mbps) Introduction of Gigabit Ethernet ended need for it

40 Gigabit Ethernet and Beyond Gigabit Ethernet runs at 1 Gigabit per second (Gbps), which is 1000 Mbps Often called GigE Originally the IEEE 802.3z standard that uses fiber Now available over UTP IEEE 802.3ab Uses same framing as other Ethernet

41 Gigabit Ethernet and Beyond Common Ethernet Timing Settings for 1000-Mbps Ethernet Standards

42 Gigabit Ethernet and Beyond 1000BASE-X Refers to three separate Gigabit Ethernet standards, all of which use fiber-optic cabling Two popular commercial versions: 1000BASE-SX (short distances) 1000BASE-LX (long distances)

43 Gigabit Ethernet and Beyond Comparing 1000BASE-SX and 1000BASE-LX

44 Gigabit Ethernet and Beyond 1000BASE-X Advantages Versus 1000BASE-T with Copper Cabling Noise immunity, because fiber-optic cabling is not susceptible to interference from nearby radiation Because 1000BASE-X is not electrical, no grounding problems exist Provides various options for different types of cabling, connectors and price points Cabling distance allows a more widely dispersed Ethernet LAN

45 Gigabit Ethernet and Beyond Comparing Maximum Cabling Distances: 1000BASE-X and 1000BASE-T

46 Gigabit Ethernet and Beyond Backbone with Two 1000BASE-X Links

47 Gigabit Ethernet and Beyond Backbone Links With 1000BASE-X, longer backbone links can be built than with ATM Up to eight parallel 1000BASE-X links could be used between switches in a single Gigabit EtherChannel Most backbone links have at least two parallel channels for redundancy

48 Gigabit Ethernet and Beyond Gigabit Ethernet Connectors Both 1000BASE-SX and 1000BASE-LX use two fiber strands one to communicate in each direction The concept is similar to using pairs of copper wires in copper cabling The connectors are typically either SC or MT-RJ connectors

49 Gigabit Ethernet and Beyond SC Connector

50 Gigabit Ethernet and Beyond MT-RJ Connector

51 Gigabit Ethernet and Beyond Backbone Links The small circles at the end of each connector represent the end of the actual fibers The transmitter on one end must connect to the detector on the other end Every fiber optical cable essentially acts like a crossover cable

52 Gigabit Ethernet and Beyond Matching Transmitter with Receiver on 1000BASE-X

53 Gigabit Ethernet and Beyond 1000BASE-T Development of Gigabit over copper required much more engineering work than Gigabit over fiber 1000BASE-T uses Cat5e cabling (Cat5 cable can be re-terminated and made to pass the Cat5e standard without replacing the cable) 2 bits (called a symbol) are sent at a time All four pairs of wires are used, with each pair transmitting twice as many bits per second as 100BASE-TX, which gives 4 x 250 Mbps = 1 Gps Each wire pair can simultaneously send and receive!

54 Gigabit Ethernet and Beyond 1000BASE-T If a NIC sends a frame and begins to send one at the same time, a collision is assumed Gigabit Ethernet does not use CSMA/CD or half duplex by choice - to do so, Gigabit hubs would be needed and none are made Gigabit switches are used instead of hubs Ethernet standards faster than Gigabit do not support CSMA/CD and half duplex

55 Gigabit Ethernet and Beyond 1000BASE-T Straight-Through Cable Pin Lead Names

56 Gigabit Ethernet and Beyond Future of Ethernet Next step is migration of the desktop to 1 Gbps Many LAN installations already run multiple 1-Gbps links as an EtherChannel between switches 10 Gigabit standards for fiber and copper have been approved by the IEEE IEEE 802.3ae standard allows links up to 40 kilometers, allowing Ethernet MAN

57 Gigabit Ethernet and Beyond Service Provider MAN with 10 Gigabit and 1 Gigabit Ethernet

58 Gigabit Ethernet and Beyond Networking Media Speeds Copper Up to 1000 Mbps (1 Gbps) (probably more) Wireless Up to 1000 Mbps (1 Gbps) (probably more) Optical Up to 10 Gbps (probably more)

59 Summary Ethernet has increased in speed 1000 times, from 10 Mbps to 10,000 Mbps All Ethernet forms share a common frame structure, which leads to excellent interoperability Most copper Ethernet connections are now switched full duplex 10GigE and faster were exclusively fiber technologies, but some are now available over copper

60 Summary 10BASE5, 10BASE2 and 10BASE-T are considered legacy Ethernet technologies The four common features of legacy Ethernet are timing parameters, frame format, transmission process, and the basic design rule The rule states that a single (10BASE5, 10BASE2 and 10BASE-T) LAN can have no more than 5 segments, 4 repeaters, and 3 segments occupied between any two LAN devices 10BASE-T uses twisted-pair cabling and was introduced in 1990

61 Summary Because 10BASE-T has multiple wires, it is capable of full duplex signaling 10BASE-T carries 10 Mbps of traffic in half duplex mode and 20 Mbps in full duplex mode 10BASE-T links can have unrepeated distances of up to 100 meters; repeaters, hubs, bridges and switches can extend the network beyond that distance A 10BASE-T LAN can be extended indefinitely by stringing together switches; each connection between switches is limited to 100 meters

62 Summary 100-Mbps Ethernet is known as FastEthernet 100-Mbps Ethernet can be implemented with twisted-pair copper wire (100BASE-TX) or with fiber (100BASE-FX) 100-Mbps Ethernet forms can transmit 200 Mbps in full duplex 100-Mbps Ethernet uses two separate encoding steps to enhance signal integrity Two fiber versions of Gigabit Ethernet, 1000BASE- SX and 1000BASE-LX, offer these advantages: Noise immunity, small size, increased unrepeated distances and bandwidth Gigabit Ethernet over fiber is the preferred backbone technology