basic ethernet b03 slide 1 ethernet networking technology overview and network design

Basic Ethernet B03 Slide 1

Ethernet Networking

Technology Overviewand

Network Design


Agenda

10 Mbit/s Ethernet technology3

2

1 What is a Local Area Network?

Overview of network technologies


Agenda

5

4 100 Mbit/s Ethernet technology

Switching technology




2



5





What is a Local Area Network?

• Definition of a LAN• Why use a LAN?• Characteristics of LANs• LAN Topologies and Structured

Cabling• Repeaters, Bridges and Routers• Switching and Segmenting networks• Virtual LANs


Definition of a LAN

• A LAN is a system of cabling, equipment and software which allows computers to share and exchange data electronically, using an agreed format (protocol), within a ‘local’ area


Other types of Area Network

• WAN - Wide Area Network– Interconnecting LANs and users over

long distances, often on a public network

• MAN - Metropolitan Area Network– Interconnecting LANs and users within a

city area, typically by dedicated fibre optics


Why use a LAN?

• An island of information


Why use a LAN?

• Users can share data– Saves time, makes work more efficient

• Connect different computers together– A LAN can be the common denominator

• Users can share resources (printers, storage)– Saves money on expensive capital equipment– Centralised administration

• E-mail, Internet and Multimedia– Reduces paper documents, better information


LAN Characteristics

• How are LANs characterised?– By speed (bandwidth)– By topology– By special features– By their target application

• LAN technologies are optimised for certain application areas


Network Topologies

BUSNodes are all connected

to the same circuit

RINGNodes are connected

in a daisy chain


Network Access Methods

Token PassingNodes wait their turn

to use the network

ContentionNodes try to use the network at any time

T


Network Wiring Topologies

Bus Ring

STAR wiring

topology

Nodes are physically wired to a central point


Structured Cabling

• Uses UTP for floor wiring• Uses Fibre for backbone connections• Many more wires installed than users

- flood wiring• All cables star-wired from central

points• Flexible, resilient, future proof, easy

moves


Connecting nodes to a LAN

Network Operating System

(NOS) Software

Network Interface Card (NIC)

Cable

Communicationby an agreed

Protocol

Network Hub

To other hosts on the network

MACAddress

“DTE”


Network Protocols• Protocols are the “language” used

on a network• The network just sends and

receives packets of data, while the protocol ensures that the right data is delivered to the right place

• Using common protocols allows computers from different manufacturers to exchange data


Protocols defined...

A protocol is a common system where both parties acknowledge the same rules governing communication.


Interconnecting Networks

• Three ways to join network segments together: Repeaters, Bridges and Routers

• Repeaters extend physical networks• Bridges link networks of the same

type together• Routers connect networks of

different types together


Connecting network segments with Repeaters

Repeater

All network traffic visible to all the nodes on the network

Repeater forwards all

activity


Connecting network segments with Bridges

Bridge

Local Traffic stays on local

segment


segment

Bridge only forwards traffic intended for the other network


Connecting networks together with Routers

Router

Router


segments

Routers transfer protocol-specific traffic (e.g. IP, IPX) between different network types, e.g. across a WAN

WAN X.25, Frame Relay, ISDN etc.

Local Network

Remote Network


Summary

• Networks allow computers to share data quickly and cheaply

• Networks are a combination of hardware and software

• Network technologies can be shared or switched, or a mix of both



What is a Local Area Network?

5




2 Overview of network technologies

1


Overview of Network technologies

• Ethernet: 10 Mbit/s • Fast Ethernet: 100 Mbit/s • Gigabit Ethernet: 1000 Mbit/s • IBM Token Ring: 4 and 16 Mbit/s• 100VG-AnyLAN: 100 Mbit/s • FDDI: 100 Mbit/s • ATM: 25, 155 and 622 Mbit/s


Ethernet Technologies

• 10 Mbit/s Ethernet– One of the oldest network technologies,

and still the most popular

• Fast Ethernet (100 Mbit/s)– Upgrade route from 10 Mbit/s, providing

higher performance

• Gigabit Ethernet (1000 Mbit/s)– The next generation for servers and

backbones, providing very high throughput


Gigabit Ethernet

• Promoted by the Gigabit Ethernet Alliance

• Being standardised in IEEE 802.3z, due in 1998

• Uses same CMSA/CD technology as Ethernet, running at 1000 Mbit/s

• Gigabit Ethernet on copper cabling is a special problem

• High-performance backbone technology


Network Technologies: Summary

• Networking technologies can be classified by their access mechanism

• Contention-based technologies are less efficient than other solutions, but the overall cost of ownership is lower

• Ethernet covers all parts of a LAN from desktop to backbone



2




5 Switching technology



10 Mbit/s Ethernet

• Origins of 10 Mbit/s Ethernet• How Ethernet works

– CSMA/CD operation– Full and Half Duplex modes– Ethernet frames

• Components of an Ethernet LAN– Software and Network Interface Card– Transceivers and Cabling– Repeaters and Hubs– Switches


Origins of 10 Mbit/s Ethernet

• Original system design by DEC, Intel, and Xerox (hence DIX Ethernet)

• Designed in 1970’s, first specifications 1980

• Ethernet type II adopted as IEEE 802.3 10BASE-X, first published in 1985


How Ethernet works 1• All transmission is at 10 million bits per second

(0’s or 1’s)• Users are connected to common cable (media)• Access to the media is by a simple set of rules

known as Carrier Sense Multiple Access / Collision Detect (CSMA/CD).– Listen for silence on cable (CS)– Transmit data without waiting your turn (MA)– If you hear someone else talking - stop sending,

and wait for a random time before trying again (CD)


How Ethernet Works 2

1. Send when the network is quiet

2. Collision is detected if another station sends

3. Both stations wait for a random time

4. Re-send again when the network is quiet


Full and Half Duplex 1

• Normal Ethernet only allows one frame on the cable at a time (Half Duplex)

• UTP and fibre optics use separate circuits for Transmit and Receive

• Full Duplex allows frames to be sent and received at the same time over a point-to-point link

• Both ends must support Full Duplex• Repeaters cannot support full duplex


Full and Half Duplex 2

Half Duplex Operation

Transmit only - OK

Receive only - OK

Transmit and Receive = Collision

Full Duplex Operation

Transmit and Receiveat same time on separatecircuits - OK


How Data is Transferred

• All data is transferred in ‘packets’• A packet of data has addressing details

at the start, and error checking data at the end. This is known as a ‘frame’

• Moving data in small pieces gives everyone an equal chance to get their data through

• Smaller packets are more likely to be delivered without errors


The Ethernet Frame

• Preamble allows timing alignment

• Start Of Frame delimiter indicates start of frame

• CRC (Cyclic Redundancy Check) is a checksum to ensure the frame was received OK

• Total frame length varies from 64 to 1,518 bytes (after SOF delimiter)

Preamble CRC (checksum)

Data 46 - 1500 Bytes

Source MAC Address

DestinationMAC Address

SOFdelimiter Type/length

6 bytes 6 Bytes 2 4


Components of an Ethernet LAN

Shared cableExternal Transceiver

Drop cable (external XCVR)

Network Interface card

Software

Point-to-point link cable (integral XCVR)

Hub:Repeater, Bridge, Switch

orRouter


Network Interface Card

• The Network Interface Card (NIC) contains:– the connection to the transceiver, or

a built-in transceiver– circuitry for generating frames and

accessing the network– the physical MAC address– a software interface to the protocol

software in the host


Transceivers

XCVR

• Transceivers provide the electrical and physical connection between the Adapter and the shared network cable

• This type of transceiver is not used much today as most NICs have this function built in.

AUI drop cable

Thick Ethernet Cable


Current Transceiver Uses

• Connecting standard hub/router/switch AUI interfaces to cable media

• Connecting ‘legacy’ cards to newer cabling


Ethernet Cable Options

10Base5

10Base2

10BaseT100BaseTX

10BaseFL100BaseFX

Thick Ethernet

Thin Ethernet

Twisted Pair (UTP)

Fibre Optic

BNC

RJ45SMA* Screw typeST BayonetSC Dual Mini

AUI connection viaVampire Tap

Ethernet Cable Connector

The cable provides physical connection between the adapter cards. Multiple cable types are available.

Usage

Half-duplexshared cable

Full-DuplexPoint-to-point link

Half-duplexshared cable


* SMA now obsolete, no new equipment manufactured to support this standard


Ethernet Cable Options

10BaseFL100BaseFX

Fibre Optic

Lucent LCNew sub-miniature SC

3M Volition VF-45Fibre version of RJ-45

AMP MT-RJFibre version of RJ-45

New fibre connectors becoming widespread during 1999/2000.



Cable Distances and Taps

10BASE5 = 10 Mbps Baseband 500 metres length (100 taps)

10BASE2 = 10 Mbps Baseband 200 (185)metres (30 Taps)

10BASE-T =10 Mbps Baseband (100 metres) Twisted pair (single Tap)


10 Mbit/s Repeaters

• 10 Mbit/s Repeaters allow more users AND more distance

• Repeaters do a number of tasks:– restore the signal levels (amplify signal)– ensure that collisions are recognised,

and stop anyone else transmitting until it is safe


• Si può vedere l’hub come un multiport repeater.

• Come nel coassiale esiste la regola dei 4 repeater negli hub a 10Mb/s

Four Repeater Roule

HubHub

HubHub

HubHub

HubHub


Ethernet 5-4-3 RuleRepeater

Repeater

Repeater

Repeater

Multinode Segment

Multinode Segment

Multinode Segment

Link Segment

Link Segment

• Maximum of five segments• Maximum of four repeaters between any two nodes• Maximum of three multi-node segments


Why are there Limits?• Transmission from a user down the

network cable takes time.• All users must see transmission before

user has transmitted half of his frame.• This may need to checked by

calculating the Round Trip Delay Time.– i.e. RT Delay < time for min frame length– or time for 64 Bytes (512 Bit times)

• The 5-4-3 rule is usually sufficient for 10 Mbit/s Ethernet


Ethernet Hubs

• Hubs provide a central connection point for networks

• Commonly used with Structured Cabling Schemes


Hubs and Management

• Hubs can be combined to create one big repeater - stackable, chassis based

• Flexible options for integrating all media types

• Management features allow network supervisors to see traffic flow and solve problems fast

• Other advanced features also added– e.g. security


10 Mbit/s Ethernet: Summary

• Repeater– copies everything from one segment to

another: collisions, fragments, all frames including broadcasts

• Bridges and Switching Hubs– Selected frames including broadcasts are

copied, based on the destination MAC address

• Router– Copies / converts selected frames based on

protocol address



2







100 Mbit/s Ethernet

• Relationship with 10BASE-X• Media options and technologies• Repeaters and configuration rules• Media Independent Interface (MII)• N-Way Auto-Negotiation• 100BASE-X switching


100BASE-X Networks

• Based on CSMA/CD• Transmission at 100 Million Bits

per second• Uses same frames as 10 Mb

Ethernet– Whole protocol stack and NOS remain

unchanged– Easy migration from existing systems


Auto-Negotiation (Nway)

• Nway auto-negotiation– Negotiation of a ‘way’ from N options– Happens between the two ends of a

link– Fastest available ‘way’ is selected– If only one end has Nway then speed

is detected (but not always duplex mode)


MII - Media Independent Interface

• MII is a standardised interface between a 100BASE-X transceiver and the connected station (DTE)

• The DTE can control the transceiver function, e.g. full/half duplex & speed

• The transceiver can ‘declare’ its capabilities to the DTE


100BASE-X Media Options

Cable IEEE 802.3u Standard Pairs Used Distance

UTP Cat 5 100BASE-TX 2 100mUTP Cat 3,4,5 100BASE-T4 4 100mFibre 100BASE-FX 2 fibres 412m*Fibre 100BASE-FX 2 fibres 2000m**

* Half Duplex DTE-DTE ** Full Duplex DTE-DTE


100BASE-X Technologies: TX

• 100BASE-TX– Uses two twisted pairs– Same system as 10BASE-T but faster!– Must have Category 5 cable to run on– Max distance 100m– Full or Half duplex possible


100BASE-X Technologies: FX

• 100BASE-FX– Uses two 62.5/125 multimode fibres – Operates at 1300nm (10BASE-FL

operates at 850nm)– Full duplex is possible but no auto-

negotiation– The maximum link length depends on

the configuration of the network • i.e. it gets shorter if you have a repeater


100BASE-X Repeaters

• Primary use for 100BASE-X repeaters is to add more users

• Otherwise the same functions as 10BASE-X repeater


100BASE-X Repeater Classes

• IEEE 802.3u defines two classes of repeater according to signal delay– Class I (the worst class!)

• delay of less than 140 bit times

– Class II• delay of less than 92 bit times

• 1 bit time is 1/100,000,000th of a second (10 nanoseconds)


100m

Basic Configuration Rules

• Maximum of one Class I repeater in a collision domain

• Maximum of 2 Class II repeaters, but limited distance

Class I

100m 100m

Class II

100m

5mClass II


Calculating complex configurations

• As with 10 Mbit/s Ethernet, the Round Trip Delay time must be less than 512 bit times to guarantee collision detection

• The basic rules about repeaters only cover the situations in the previous slide, so always calculate anything else


Calculating the Delay

“Typical bit time delays” for 100 Mbit/s network components

Component Delay per metre Max delayTwo TX/FX DTEs 100Two T4 DTEs 138One T4 and one TX/FX DTE 127Cat 3 Cable Segment 1.14 114 (100m)Cat 4 Cable segment 1.14 114 (100m)Cat 5 Cable segment 1.112 111.2 (100m)Shielded Twisted Pair Cable 1.112 111.2 (100m)Fibre Optic Cable 1.0 412 (412m)Class I Repeater 140Class II Repeater all TX/FX 92Class II Repeater with any T4 67AT-MC101 40


Example Calculation 1

100Mbps Hub 100Mbps Hub60m Fibre

80m UTP 100m UTP

Device Delay (bit times)Two DTEs 100180m Cat 5 UTP 2002* Class II Repeaters 18460m Fibre segment 60margin 4TOTAL 548

The above system is outside the limits and will not function correctly


Example Calculation 2200m Fibre

100m UTP

Device Delay (bit times)Two DTEs 100100m Cat 5 UTP 111Class II Repeater 92200m Fibre segment 200Margin 4TOTAL 507

The above system is within the 512 bit time limit so will work OK.

100Mbps Hub


Switched 100 Mbit/s

• Similar to switched 10 Mbit/s Ethernet• Most 100 Mbit/s switches support 10

Mbit/s ports too• Requires an order of magnitude

increase in throughput– 160 Mb/s for 16 port 10Mbps switch– 1.6 Gb/s for 16 port 100Mbps switch

• Key application as backbone switch



• 100 Mbit/s and 10 Mbit/s Ethernet use the same CSMA/CD technology and software

• Shared multi-drop cables are not supported• Round Trip Delay time calculations are

essential for network design• 100 Mbit/s can be integrated into a 10

Mbit/s network only with switching technology


H H

H H

H H

H H

H H


• Distances are more restricted so 100Mbps tends to be switch-centric in design.

SS S

S

S

H SS



2



5





Switching Technology 1

– The maximum bandwidth available on a shared network is limited to the network speed, regardless of the number of nodes

– The maximum traffic that these nodes could generate is more than the network could carry

– Sharing the same media introduces a bottleneck

Conversation


Switching Technology 2

Three simultaneo

us conversatio

ns

A Switching Hub at the centre of the network can handle multiple point-to-point conversations at the same time

The use of the network is more efficient


Segmenting Networks 1

• Very large networks are less efficient, even with switching technology

• It is unusual for all users on a large network to need frequent communications with all other users

• Segmenting a large network into functional groups improves performance and manageability



100%

• Large networks generate a lot of traffic at the hub in the centre

• The broadcast load is proportional to the square of the number of nodes



25%Non-

broadcast inter-

network traffic

Broadcast load is

quartered

25%


Switched 10 Mbit/s• Switch separates traffic that is sent direct

from station to station - Datagrams.• MAC addresses are learned from

incoming frames.• Frames are only sent out of port where

the destination address resides.• Broadcast frames are forwarded to all

ports, to the MAC address FF-FF-FF-FF-FF-FF


Switching Techniques 1

Store and forward switchingWhole frame buffered in memory, then sent

Preamble CRC


Source Address

Destination AddressSOF delimiter Type/length

6 bytes 6 Bytes 2 4

Cut-through switchingForwarding started just after the destination MAC address arrives


Switching Techniques 2

Fragment-free cut-through

frame forwarded after 64 Bytes

Preamble

CRC


Source Address

Destination AddressSOF delimiter Type/length

6 bytes 6 Bytes 2 4


Segment Switching

• Switch is used to ‘feed’ hubs.• Small groups of users share 10 Mbit/s

segments from switch e.g. Turbo Stack• Reasonable MAC address capacity

required• Extra features

hub

hub

hub

hub

switch


Workgroup Switching

• Small switch provides dedicated switch ports to individual ‘power’ users.

• Low MAC address capacity required• Low cost per port

Switch


Backbone/Enterprise Switching

• Large, high capacity switch used to connect backbone segments of large networks.

• Huge MAC address capacity required• Modular design - chassis based• Very high throughput capability


Bandwidth Switching

• Switches can be used to connect segments of different speeds, e.g. 10 and 100 Mbit/s

• The 10 Mbit/s segments can be ‘multiplexed’ onto the 100 Mbit/s segment

• The switch must use Store-and-Forward to change the bandwidth

Switch100 Mbit/s

10 Mbit/s


Rules for using Switches

• Switch is essentially a bridge, so start any repeater counts again.

• Too many switches in network could cause delay. IEE 802.3 says max 7 bridges. (This is an arbitrary number based on Token Ring limitations)

• Keep number of hops to main servers low.


Sw

10 Mbps

100 Mbps

….

Hub Dual-Speed Autosensing

• Reti miste: con utenti a 10 e 100 mbps• Configurazione Stackable: facilmente espandibile• Percorso di migrazione da Ethernet a Fast

Ethernet

SwitchModule


Virtual LANs (VLANs) 1

• A company-wide network may not be the right solution, due to high traffic and security issues

• The user may want to divide their big network into smaller sections

• But, flexibility is also needed as people move around

• A “Virtual Network” solves this problem


Virtual LANs 2

Virtual Network Virtual Network SwitchSwitch

VLAN “A”VLAN “A”

VLAN “B”VLAN “B”

VLAN “C”VLAN “C”



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6


1000 Mbit/s Ethernet technology



The pressure on networks today

• Traffic Flows have changed– Used to be 80% local, 20% backbone– Now 20% local and 80% backbone

• User requirements have changed– Word processing was dominant– Now Internet use is the dominant application

• Application useage has changed– It only takes 8 bytes to send the word ‘airplane’– It takes 80,000 bytes to send an image of an airplane– It takes 8,000,000 to send a video clip of an airplane


1000Mbps Gigabit Systems

• Same frame formats and protocols as 10/100 Ethernet

• Same Full/Half Duplex mode• Same management (SNMP/RMON)

systems• Primarily a fibre based technology• Standardised by IEEE as 802.3z


1000BaseX Cable Options

Standard Media Range

1000BaseLX Single Mode Fibre 3km+

1000BaseLX Multi-Mode Fibre 550m

1000BaseSX Multi-Mode 300m

(most common type)

1000BaseCX Twinaxial Cable 25m

1000BaseT UTP 100m


1000BaseX Media

• The basic media carrier for 100Base is the GBIC

• GBICs are a media independent device (similar to transceiver in 10Base)

• Provide plug in options for SX or LX fibre


1000BaseX Hardware

• Switches and Routers for Networks

• Two primary types of switch– Core Switches……Multiple Gigabit ports

– Edge Switches……Multiple 10/100 ports 1 or 2 Gigabit ports


A new layer of performance

100Base Hub

10Base Hub 10Base Hub

10Base Switch

100Base Switch

1000Base Edge

100Base Hub

10Base Hub 10Base Hub

10Base Switch

100Base Switch

1000Base Edge

1000Base Core

Perfo

rman

ce


Thank you for your attention

basic ethernet b03 slide 1 ethernet networking technology overview and network design

Documents

basic ethernet b03 slide

network design slide

lan network

local area slide

better information slide

island of information

central point slide

time t slide