Switch Principles of operation

스위치동작원리

1.�Ethernet�UTP�Cable

1

ALL�OF�THE�NETWORK�SOLUTION

UTP�Cable 구조

2

1

2

3

4

5

6

7

8

1

2

3

4

5

6

7

8

TIA/EIA-568A TIA/EIA-568B


RJ-45�Port�구조

3

1 TX+

2 TX-

3 RX+

4 Not Used

5 Not Used

6 RX-

7 Not Used

8 Not Used

RX+ 1

RX- 2

TX+ 3

Not Used 4

Not Used 5

TX- 6

Not Used 7

Not Used 8

MDI MDI-X

MDI : Medium Dependent Interface

MDI-X : Medium Dependent Interface Crossover


PC간 Cable�연결

4

1 TX+

2 TX-

3 RX+

4 Not Used

5 Not Used

6 RX-

7 Not Used

8 Not Used

MDI

TX+ 1

TX- 2

RX+ 3

Not Used 4

Not Used 5

RX- 6

Not Used 7

Not Used 8

MDI

TIA/EIA-568A TIA/EIA-568BCrossover Cable


Hub/Switch와 PC간 연결

5

1 TX+

2 TX-

3 RX+

4 Not Used

5 Not Used

6 RX-

7 Not Used

8 Not Used

MDI

RX+ 1

RX- 2

TX+ 3

Not Used 4

Not Used 5

TX- 6

Not Used 7

Not Used 8

MDI-X

Straight Cable

TIA/EIA-568A TIA/EIA-568ATIA/EIA-568B TIA/EIA-568B


2.�Hub의동작원리

6


Hub의 구조

7

MDI-X MDI-X

MDI-X MDI-X

MDI MDI

MDI MDI

Straight Cable TX

TX

RX

RX

TX

TX

RX

RX

RX

RX

TX

TX

RX

RX

TX

TX

TXRX TXRX

RX TX RX TX


CSMA/CD

8

MDI-X MDI-X

MDI-X MDI-X

MDI MDI

MDI MDI

TX

TX

RX

RX

TX

TX

RX

RX

RX

RX

TX

TX

RX

RX

TX

TX

TXRX TXRX

RX TX RX TX

Carrier Sense Multiple Access


CSMA/CD

9

MDI-X MDI-X

MDI-X MDI-X

MDI MDI

MDI MDI

TX

TX

RX

RX

TX

TX

RX

RX

RX

RX

TX

TX

RX

RX

TX

TX

TXRX TXRX

RX TX RX TX

Collision Detection


Hub/Switch간연결

10

TX RX

RXTXTX

RX

Crossover Cable


3.�Switch�탄생배경

11


Hub의 한계 및Bridge의 등장

12

CSMA/CD

1.�RX로 Traffic이들어오면 TX�기능이 Disable된다.

2.�TX로 Traffic전송하는 도중에 RX에서 Traffic이들어오면전송을 멈추고 ZAM�신호를 전달한다.�

Hub에 연결된장비는 Half�Duplex로 동작함

Hub에 연결된장비 중 한대가 Taffic을전송하고있으면 나머지장비는 전송하지못함

※ 5대의 장비가Hub에 10Mbps�회선으로연결되어 있다면?

10Mbps를 5대의장비가 Share하기때문에 각 장비는평균 2Mbps의 Traffic�전달이 가능함


Bridge의한계 및 Switch의등장

13

MDI-X MDI-X

MDI-X MDI-X

MDI MDI

MDI MDI

TX

TX

RX

RX

TX

TX

RX

RX

RX

RX

TX

TX

RX

RX

TX

TX

TXRX TXRX

RX TX RX TX

CPU

Destination MAC A.A.A가 4번 Port

에 연결되어 있군!!

1.�Delay가 많이발생한다.

2.�많은 Port를연결할 수 없다.


Switch�개요

14

MDI-X MDI-X

Buffer Buffer

ASIC

ASIC

ASIC

ASIC

Buffer

MDI-X

Buffer

MDI-X

CAM(MAC-address)

Destination MAC A.A.A가 4번 Port

에 연결되어 있군!!


4.�ARP�(Address�Resolution�Protocol)

15


ARP란 무엇인가?

16

IP address : 10.10.10.12MAC address : 0025.22C1.0B9F

IP address : 10.10.10.100MAC address : 0050:C2B3:B191

ICMP

Source IP : 10.10.10.12Destination IP : 10.10.10.100

Source MAC : 0025.22C1.0B9FDestination MAC :

ARP

요청

10.10.10.100의MAC address가 뭐야?



17



ICMP



ARP

요청


ARP Request


ARP�Request�Packet

18



19



ICMP



ARP

요청


ARP Request

ARP Reply


ARP�Reply�Packet�구조

20


GARP(Gratuitous�ARP)란 무엇인가?

21


1.�MAC�address�변경

2.�IP�address�설정 및 변경

3.�DHCP로 받은 address�충돌여부확인

4.�VRRP/HSRP에서 Active/Standby�변경 시

GARP(Gratuitous ARP)


GARP(Gratuitous�ARP)�Packet�구조

22

reply

FF:FF:FF:FF:FF:FF

reply (2)


5.�Switch�동작원리

23


Collision�Domain�생성

24

MDI-X MDI-X

MDI-X MDI-X

MDI MDI

MDI MDI

TX

TX

RX

RX

TX

TX

RX

RX

RX

RX

TX

TX

RX

RX

TX

TX

TXRX TXRX

RX TX RX TX

Full Duplex Full Duplex

Full Duplex Full Duplex


Switch�동작원리 :�Learning�&�Flooding

25

Port #1 Port #2

Port #3 Port #4

GARP



Source MAC : 0025.22C1.0B9F Destination MAC : FFFF.FFFF.FFFF

VLAN Port MAC address

GARP

Source MAC : 0050:C2B3:B191 Destination MAC : FFFF.FFFF.FFFF

1 4 0050:C2B3:B191

1 1 0025.22C1.0B9F

Switch는 Destination�MAC�address를 MAC�address�table에서

찾지 못한 경우들어온 Port를 제외한 나머지 Port들로 Flooding함

Switch는 유입된 Frame의 Source�MAC�address�정보를 Learning하

여 MAC�address�table을 만든다.


Switch�동작원리 :�Forwarding�&�Filtering

26

Port #1 Port #2

Port #3 Port #4

ARP



Source MAC : 0025.22C1.0B9F Destination MAC : FFFF.FFFF.FFFF


ARP

Source MAC : 0050:C2B3:B191 Destination MAC : 0025.22C1.0B9F

1 4 0050:C2B3:B191

1 1 0025.22C1.0B9F

Switch는 Destination�MAC�address를 MAC�address�table에서

찾은 경우 해당MAC�address가 존재하는 Port로만 Forwarding함

Switch는 Frame이 유입된 Port로는 전송하지 않으며, MAC�address를

table에 존재하는 경우타 Port로는 전송하지 않음


Switch�동작원리 :�Unknown�Unicast

2727

Port #1 Port #2

Port #3 Port #4

Frame



Source MAC : 0025.22C1.0B9F Destination MAC : 0050.C2B3.B191


1 4 0050:C2B3:B191

1 1 0025.22C1.0B9F


Duplex�mismatch

28

Full-Duplex Half-Duplex

Collision?

Duplex�mismatch보다 양쪽모두 Half-Duplex로 구성하는

것이속도가더빠르다.


Port�Speed�mismatch

29

Port

#1

Port

#2

Buf

fer

Buf

fer

50Mbps 10Mbps

Buffer Full40Mbps Drop

Buf

fer

100Mbps10Mbps


MAC�Spoofing과MAC-address�Table

30

Port

#1

ASI

C

Source MAC : 0025.22C1.0B9F

Destination MAC : 0050.C2B3.B191

Control-Plane

Data-Plane

Process

Source MAC : 0025.22C1.0B9F

CAM table

Hash

Destination MAC : Hash

Not 48bit16bit or 17bitSource MAC #1

Source MAC #2Source MAC #3Source MAC #4Source MAC #5...

CAM table

더이상MAC�address�학습이불가능하여Hub처럼동작


Redundancy�구조에서의 Looping�발생

31

Unknown Unicast/Broadcast/Multicast

Engineering

Switch Principles of operation