chapter 10: ethernet and fibre cable business data communications, 5e

39
Chapter 10: Ethernet and Fibre Cable Business Data Communications, 5e

Post on 21-Dec-2015

219 views

Category:

Documents


3 download

TRANSCRIPT

Page 1: Chapter 10: Ethernet and Fibre Cable Business Data Communications, 5e

Chapter 10: Ethernet and Fibre Cable

Business Data Communications, 5e

Page 2: Chapter 10: Ethernet and Fibre Cable Business Data Communications, 5e

Business Data Communications, 5e

2

Increase in High-Speed LANs

• Extraordinary growth in speed, power, and storage capacity of PCs

• Increasing use of LANs as computing platforms

• Examples– Server farms– Workgroups with “power” requirements– High-speed backbones

Page 3: Chapter 10: Ethernet and Fibre Cable Business Data Communications, 5e

Business Data Communications, 5e

3

Increase in High-Speed LANs

• Fast Ethernet and Gigabit Ethernet

• Fibre Channel

• High-speed Wireless LANs

Page 4: Chapter 10: Ethernet and Fibre Cable Business Data Communications, 5e

Business Data Communications, 5e

4

Characteristics of Some High-Speed LANS

Page 5: Chapter 10: Ethernet and Fibre Cable Business Data Communications, 5e

Business Data Communications, 5e

5

Trends Influencing Emergenceof High-Speed LANs

• Explosive growth of speed and computing power of PCs

• Recognition by MIS organizations of the value and importance of networked computing– Centralized server farms– Power workgroups– High-speed local backbone

Page 6: Chapter 10: Ethernet and Fibre Cable Business Data Communications, 5e

Business Data Communications, 5e

6

Traditional Ethernet

• Ethernet and CSMA/CD (IEEE 802.3)• Carrier sense multiple access with collision

detection• Four step procedure

– If medium is idle, transmit

– If medium is busy, listen until idle and then transmit

– If collision is detected, cease transmitting

– After a collision, wait a random amount of time before retransmitting

Page 7: Chapter 10: Ethernet and Fibre Cable Business Data Communications, 5e

Business Data Communications, 5e

7

Ethernet MAC Frame Format

• Preamble: 7-octet pattern of 0s &1s used to establish bit synchronization.

• Start Frame Delimiter (SFD): Indicates actual start of frame.• Destination Address (DA): Specifies the station(s) for which the

frame is intended• Source Address (SA): Specifies the station that sent the frame.• Length: Length of LLC data field in octets. • LLC Data: Data unit supplied by LLC.• Pad: Octets added to ensure that the frame is long enough for proper

CD operation.• Frame Check Sequence (FCS): A 32-bit CRC, based on all fields

except preamble, SFD, and FCS.

Page 8: Chapter 10: Ethernet and Fibre Cable Business Data Communications, 5e

Business Data Communications, 5e

8

Ethernet MAC Frame

Page 9: Chapter 10: Ethernet and Fibre Cable Business Data Communications, 5e

Business Data Communications, 5e

9

802.3 Medium Notation

• Notation format:<data rate in Mbps><signaling method><maximum segment length in hundreds of meters>

• e.g 10Base5 provides 10Mbps baseband, up to 500 meters

• T and F are used in place of segment length for twisted pair and fiber

Page 10: Chapter 10: Ethernet and Fibre Cable Business Data Communications, 5e

Business Data Communications, 5e

10

802.3 10BaseX Media Options

Page 11: Chapter 10: Ethernet and Fibre Cable Business Data Communications, 5e

Business Data Communications, 5e

11

Bridges

• Allow connections between LANs and to WANs• Used between networks using identical

physical and link layer protocols• Provide a number of advantages

– Reliability: Creates self-contained units

– Performance: Less contention

– Security: Not all data broadcast to all users

– Geography: Allows long-distance links

Page 12: Chapter 10: Ethernet and Fibre Cable Business Data Communications, 5e

Business Data Communications, 5e

12

Bridge Functions

• Read all frames from each network

• Accept frames from sender on one network that are addressed to a receiver on the other network

• Retransmit frames from sender using MAC protocol for receiver

• Must have some routing information stored in order to know which frames to pass

Page 13: Chapter 10: Ethernet and Fibre Cable Business Data Communications, 5e

Business Data Communications, 5e

13

Bridge Operation

Page 14: Chapter 10: Ethernet and Fibre Cable Business Data Communications, 5e

Business Data Communications, 5e

14

Key Aspects of Bridge Function

• Makes no modification to content or format of frames it receives; simply copies from one LAN and repeats with exactly the same bit pattern as the other LAN.

• Should contain enough buffer space to meet peak demands.

• Must contain addressing and routing intelligence. • May connect more than two LANs.

Page 15: Chapter 10: Ethernet and Fibre Cable Business Data Communications, 5e

Business Data Communications, 5e

15

Hubs

• Alternative to bus topology• Each station is connected to the hub by two lines

(transmit and receive)• When a single station transmits, the hub repeats

the signal on the outgoing line to each station.• Physically a star; logically a bus.• Hubs can be cascaded in a hierarchical

configuration.

Page 16: Chapter 10: Ethernet and Fibre Cable Business Data Communications, 5e

Business Data Communications, 5e

16

Two-Level Hub Topology

Page 17: Chapter 10: Ethernet and Fibre Cable Business Data Communications, 5e

Business Data Communications, 5e

17

Layer 2 Switches

• Also called a “switching hub”• Has replaced hub in popularity, particularly for

high-speed LANs• Provides greater performance than a hub• Incoming frame from a particular station is

switched to the appropriate output line to be delivered to the intended destination

• At the same time, other unused lines can be used for switching other traffic

Page 18: Chapter 10: Ethernet and Fibre Cable Business Data Communications, 5e

Business Data Communications, 5e

18

Ethernet Hubs and Switches

• Shared medium hubs

• Switched LAN hubs

x

Page 19: Chapter 10: Ethernet and Fibre Cable Business Data Communications, 5e

Business Data Communications, 5e

19

Advantages of Switched Hubs

• No modifications needed to workstations when replacing shared-medium hub

• Each device has a dedicated capacity equivalent to entire LAN

• Easy to attach additional devices to the network

Page 20: Chapter 10: Ethernet and Fibre Cable Business Data Communications, 5e

Business Data Communications, 5e

20

Types of Switched Hubs

• Store and forward switch– Accepts a frame on input line– Buffers it briefly– Routes it to appropriate output line

• Cut-through switch– Begins repeating the frame as soon as it

recognizes the destination MAC address– Higher throughput, increased chance of error

Page 21: Chapter 10: Ethernet and Fibre Cable Business Data Communications, 5e

Business Data Communications, 5e

21

Differences Between Switched Hubs and Bridges

• Bridge frame handling is done in software. A layer 2 switch performs the address recognition and frame forwarding functions in hardware.

• Bridges typically only analyze and forward one frame at a time; a layer 2 switch can handle multiple frames at a time.

• Bridges uses store-and-forward operation; layer 2 switches use cut-through instead of store-and-forward operation

• New installations typically include layer 2 switches with bridge functionality rather than bridges.

Page 22: Chapter 10: Ethernet and Fibre Cable Business Data Communications, 5e

Business Data Communications, 5e

22

Problems With Layer 2 Switches

• Broadcast overload • Lack of multiple links• Can be solved with subnetworks connected by

routers• However, high-speed LANs layer 2 switches

process millions of packets per second whereas a software-based router may only be able to handle well under a million packets per second

Page 23: Chapter 10: Ethernet and Fibre Cable Business Data Communications, 5e

Business Data Communications, 5e

23

Layer 3 Switches

• Implement the packet-forwarding logic of the router in hardware.

• Packet-by-packet switch operates like a traditional router– Forwarding logic is in hardware– Achieves an order of magnitude increase in performance

compared to software-based routers

• Flow-based switch identifies flows of IP packets that have the same source and destination– Once flow is identified, a predefined route can be established to

speed up the forwarding process– Again, huge performance increases over a pure software-based

router are achieved

Page 24: Chapter 10: Ethernet and Fibre Cable Business Data Communications, 5e

Business Data Communications, 5e

24

Why Use Ethernet for High-Speed Networks?

• Negative– CSMA/CD is not an ideal choice for high-speed LAN

design due to scaling issues, but there are reasons for retaining Ethernet protocols

• Positive– Use of switched Ethernet hubs in effect eliminates

collisions– CSMA/CD protocol is well understood; vendors have

experience building the hardware, firmware, and software

– Easy for customers to integrate with existing systems

Page 25: Chapter 10: Ethernet and Fibre Cable Business Data Communications, 5e

Business Data Communications, 5e

25

Fast Ethernet

• Refers to low-cost, Ethernet-compatible LANs operating at 100 Mbps

• 802.3 committee defined a number of alternatives to be used with different transmission media

Page 26: Chapter 10: Ethernet and Fibre Cable Business Data Communications, 5e

Business Data Communications, 5e

26

802.3 100Base-T Options

Page 27: Chapter 10: Ethernet and Fibre Cable Business Data Communications, 5e

Business Data Communications, 5e

27

802.3 100BaseX Media Options

Page 28: Chapter 10: Ethernet and Fibre Cable Business Data Communications, 5e

Business Data Communications, 5e

28

Gigabit Ethernet

• Retains CSMA/CD protocol and Ethernet format, ensuring smooth upgrade path

• Uses optical fiber over short distances

• 1-gbps switching hub provides backbone connectivity

Page 29: Chapter 10: Ethernet and Fibre Cable Business Data Communications, 5e

Business Data Communications, 5e

29

Gigabit Ethernet Media Options

Page 30: Chapter 10: Ethernet and Fibre Cable Business Data Communications, 5e

Business Data Communications, 5e

30

10-Gbps Ethernet

• Driven by increased network traffic– Increased number of network connections

– Increased connection speed of each end-station (e.g., 10 Mbps users moving to 100 Mbps, analog 56k users moving to DSL and cable modems)

– Increased deployment of bandwidth-intensive applications such as high-quality video

– Increased Web hosting and application hosting traffic

Page 31: Chapter 10: Ethernet and Fibre Cable Business Data Communications, 5e

Business Data Communications, 5e

31

10-Gbps Ethernet vs ATM

• No expensive, bandwidth-consuming conversion between Ethernet packets and ATM cells is required

• Combination of IP and Ethernet offers quality of service and traffic policing capabilities that approach those provided by ATM

• A wide variety of standard optical interfaces have been specified for 10-Gbps Ethernet, optimizing its operation and cost for LAN, MAN, or WAN applications

Page 32: Chapter 10: Ethernet and Fibre Cable Business Data Communications, 5e

Business Data Communications, 5e

32

Physical Layer Options for 10-Gbps Ethernet

Page 33: Chapter 10: Ethernet and Fibre Cable Business Data Communications, 5e

Business Data Communications, 5e

33

Example 100-Mbps Ethernet Backbone Strategy

Page 34: Chapter 10: Ethernet and Fibre Cable Business Data Communications, 5e

Business Data Communications, 5e

34

Fibre Channel

• Combine the best features of channel and protocol-based technologies– the simplicity and speed of channel communications

– the flexibility and inter-connectivity that characterize protocol-based network communications.

• More like a traditional circuit-switched or packet-switched network, in contrast to the typical shared-medium LAN

Page 35: Chapter 10: Ethernet and Fibre Cable Business Data Communications, 5e

Business Data Communications, 5e

35

Fibre Channel Goals

• Full-duplex links with two fibers per link

• Performance from 100 Mbps to 800 Mbps on a single link (200 Mbps to1600 Mbps per link)

• Support for distances up to 10 km

• Small connectors• High-capacity utilization

with distance insensitivity

• Greater connectivity than existing multidrop channels

• Broad availability (i.e., standard components)

• Support for multiple cost/performance levels, from small systems to supercomputers

• Ability to carry multiple existing interface command sets for existing channel and network protocols

Page 36: Chapter 10: Ethernet and Fibre Cable Business Data Communications, 5e

Business Data Communications, 5e

36

Fibre Channel Elements

• Nodes– The end systems

– Includes one or more N_ ports for interconnection

• Fabric– Collection of switching elements s between systems

– Each element includes multiple F_ ports

– Responsible for buffering and for routing frames between source and destination nodes

Page 37: Chapter 10: Ethernet and Fibre Cable Business Data Communications, 5e

Business Data Communications, 5e

37

Fibre ChannelProtocol Architecture

• FC-0 Physical Media: Includes optical fiber, coaxial cable, and shielded twisted pair, based on distance requirements

• FC-1 Transmission Protocol: Defines the signal encoding scheme

• FC-2 Framing Protocol: Defines topologies, frame format, flow/error control, and grouping of frames

• FC-3 Common Services: Includes multicasting• FC-4 Mapping: Defines the mapping of various

channel and network protocols to Fibre Channel

Page 38: Chapter 10: Ethernet and Fibre Cable Business Data Communications, 5e

Business Data Communications, 5e

38

Fibre Channel Media

• Media options include shielded twisted pair, video coaxial cable, and optical fiber

• Data rates range from 100 Mbps to 3.2 Gbps

• Point-to-point link distances range from 33 m to 10 km

Page 39: Chapter 10: Ethernet and Fibre Cable Business Data Communications, 5e

Business Data Communications, 5e

39

Fibre Channel Topologies

• Fabric/Switched Topology– includes at least 1 switch to interconnect end systems.

– may also use multiple switches for a switched network, with switches also supporting end nodes

• Point-to-point topology – only two ports, directly connected, with no intervening fabric

switches

• Arbitrated loop topology – Simple, low-cost topology for connecting up to 126 nodes in a

loop.

– Operates in a manner roughly equivalent to token ring protocols