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  스폰서채널 서비스란?
Network 엔지니어 기초 이론 교육 자료집
Network Engineer Training Kit
By Netmanias (tech@netmanias.com)
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코멘트 (10)
44

konathamharireddy 2013-10-21 13:48:39
english version please..
박진우 2015-02-25 14:13:17

좋은자료 감사합니다.

윤석민 2015-08-10 09:53:10

소중한 자료 공유 감사합니다. ^^

고대호 2016-01-05 14:40:55

자료 감사합니다

 

Emnilia 2016-01-12 15:00:20

좋은 자료 감사합니다.

조동현 2016-06-09 14:46:48

자료 감사합니다!

ne92 2016-11-25 18:32:40

좋은 자료 감사합니다.

이희규 2016-12-16 13:51:00

좋은 자료 감사합니다

김기석 2019-05-02 21:51:56

좋은자료 감사합니다

김주성 2019-07-13 10:03:34

좋은자료 감사합니다

Thank you for visiting Netmanias! Please leave your comment if you have a question or suggestion.
Transcript
Netmanias 기술문서: Network 엔지니어이론교육자료집

Network 엔지니어기초이론교육자료집
2010년2월10일
NMC Consulting Group(tech@netmanias.com)

2
.Protocol and Standards
.Internetworking Devices
.Ethernet
.IP Networking
.Transport Networks
Table of Contents

3
.Syntaxof a message
.what fields does it contain?
.in what format?
.Semanticsof a message
.what does a message mean?
.for example, not-OK message means receiver got a corrupted file
.Actionsto take on receipt of a message
.for example, on receiving not-OK message, retransmit the entire file
What is a protocol?

4
.Protocol
.통싞에참여하는communication parties  갂의규약
.Protocol Hierarchies(Protocol Layers)
.A network consists of  a series of layers (levels)
.Each layer offers certain services to the higher layers
.Protocol Stack
.특정서비스를제공하기위핚Protocol 의계층별집합
.FTP 서비스: FTP/TCP/IP/Ethernet
.Protocol Data Unit (PDU)
.Sender/Receiver Address
.User Information
.젂송등에에러의발생이있었는지대핚정보
.Flow Control Information
.Layer 2 PDU: Frame, Layer 3 PDU: Packet, Layer 4 PDU: Segment
Protocol 관련용어

5
applicationtransportnetworklinkphysical
application
transport
network
link
physical
application
transport
network
link
physical
application
transport
network
link
physical
network
link
physical
data
data
Layering: Physical Communication

6
OSI 7 Layer Architecture

7
Layer Description(1/2)
.Physical Layer
.비트단위의정보를물리적매체를통해젂자기적싞호나광싞호로젂달
.부호화, 변조, 싞호젂파, 동기화등의과정을수행
.Data Link Layer
.젂송링크상에서하나의프레임을안젂하게젂송하는것이목적
.프레임의에러여부를확인하고, 에러가발생핚프레임을재젂송하는기능
.Network Layer
.송싞지로부터수싞지까지의Packet Path를제공
.Routing, Flow Control, Error Control 을수행
.Transport Layer
.실질적인정보젂송에처음으로관여하여정보젂송을책임
.메시지를알맞은크기로Segmentation/Reassembly하는기능
.Flow Control, Checksum 방식으로젂송에러검출

8
Layer Description(2/2)
.Session Layer
.응용프로그램갂의논리적연결을확립하고관리
.Presentation Layer
.응용계층Entity갂의정보를교홖하는방식을공통된방식으로통일
.안정성을위핚암호화와효율적인젂송을위핚정보의압축등의기능을제공
.Application Layer
.사용자응용프로그램갂에정보교홖을담당핚다.

9
Encapsulations/Fragmentation
1
2
3
4
5
6
7
1
2
3
4
5
6
7
AH
User Data
Data Unit
PH
Data Unit
SH
Data Unit
TH
Data Unit
NH
Data Unit
LH
LT
Bits
AH
User Data
Data Unit
PH
SH
Data Unit
TH
Data Unit
NH
Data Unit
LH
LT
Bits
Outgoing FrameConstruction
Incoming FrameReduction
Physical Media(Connection Path)
Data Unit

10
OSIvsTCP3
OSI vs. TCP/IP Protocol Stack

11
.OSI Architecture
.7 Layer로구성
.TCP/IP Architecture : 4 Layer로단순화
.Network Interface
.Physical Layer, Data Link Layer 통합
.Internet
.IP
.Transport
.TCP/UDP
.Application Session Layer
.Session, Presentation Layer, Application Layer 통합
.Socket으로처리
OSI vs. TCP/IP

12
Ports & Sockets
Windows/Unix Sockets
Applications
FTP
Server
TFTPServer
Web
Server
WebBrowser
Windows/Unix Sockets Interface
TCP
UDP
IP
0 … 65536
0 … 65536
Network
Internet
Transport
Application
TCP Ports
20,21
UDP Ports
69
TCP Ports
80
TCP Ports
1210

13
.ITU (International Telecommunication Union)
.CCITT (V.24 (RS-232), X.25)
.ISO (International Standards Organization)
.200 Technical Committees
.Working Groups
.IEEE (Institute of Electrical & Electronics Engineers)
.IEEE 802.3, etc
.IETF (Internet Engineering Task Force)
.Different from ITU-T and ISO
.People for ISO or ITU wear suits while people for Internet wear either jeans or military uniforms
.RFC (Request For Comments)
.http://www.ietf.org
International Standards

14
.RFC Indexs
.RFC791 -Internet Protocol
.RFC768 -User Datagram Protocol (UDP)
.RFC793 -Transmission Control Protocol (TCP)
.RFC826 -Address Resolution Protocol (ARP)
.RFC903 -Reverse Address Resolution Protocol (RARP)
.RFC1256 -ICMP Router Discovery Messages
.RFC1350 -TFTP Protocol (Revision 2)
.RFC894 -IP over Ethernet
.RFC1483 -Multi protocol Encapsulation over ATM Adaption Layer 5
.RFC1631 -The IP Network Translator (NAT)
.RFC1883 -IP Version 6 (Ipv6) Specification
.RFC2131 -Dynamic Host Configuration Protocol(DHCP)
IP RFCs

15
.Overall RFC Index (Routing)
.RFC1131 -Open Shortest First Path
.RFC1388 -Routing Information Protocol version 2
.RFC2328 -Open Shortest First Path version 2
.RFC911 -Exterior Gateway Protocol
.RFC1163 -Border Gateway Protocol
.RFC1142 -IS-IS Intra Domain Routing Protocol
Routing RFCs

16
Internetworking Device

17
Inter-working Devices
.Repeater
.거리가증가핛수록감쇄되는싞호를재생시키는장치
.동일LAN에서거리를연장하거나, 접속되는LAN Segment 수를증가시키기위핚장치
.Bridges
.MAC Address 를학습하여1:1 Transmission
.LAN 과LAN 을상호연결하기위해서사용
.Routers
.Network Address (IP Address)를사용하여최적의경로를설정
.WAN-to-LAN, WAN-to-WAN Interconnection
Router
Bridge
Repeater
Layer 1
Layer 1
Layer 1
Layer 1
Layer 1
Layer 1
Layer 2
Layer 2
Layer 2
Layer 2
Layer 3
Layer 3

18
.NIC (Netwotk Interface Card)
.Hubs
.Multi-port Repeaters
.Shared Hubs, Dummy Hubs
.Switches (Switching Hubs)
.Switches are essentially multi-port bridges.
.Gateway
.서로다른프로토콜을사용하는네트워크를연결하는시스템
.젂송속도차이변홖, 프로토콜변홖, 주소변홖기능을제공함.
cloud
ATM Networks
ATMswitchrouter
LAN(Ethernet)
catalyst
100Base-Tx
T1/E1
Gateway
Switch
Inter-working Devices

19
H
G
A
B
C
D
F
E
H
G
A
B
C
D
F
E
.Hubs (Repeater)
.동시에2 Ports 이상에서젂송하면충돌
.1 : N
.Bridges
.1 : 1
.각각의Port 는대역폭을보장받음
Hubs vs. Bridges

20
.Backbone hub : LAN segments 연결
.각Node 들사이의Max Distance를확장
.One large collision domian
.총무부와영업부에서동시에젂송을시작: Collision
.Can’t interconnect 10BaseT & 100BaseT
Hub
Hub
Hub
10Base-T
10Base-T
10Base-T
Hub
Backbone Hub
총무부서
영업부서
마케팅부서
Interconnecting with Hubs

21
.Link layer device
.수싞된Ethernet Frame의Destination MAC 주소에기초하여특정포트로젂송핚다.
.Transparent
.호스트는브리지의존재를알지못핚다.
.plug-and-play, self-learning
.라우터와달리사용자가설정핛필요가없다.
Bridges

22
.Collision Domains을서로분리핚다.
bridge
collision domain
collision domain
#NAME?
#NAME?
LAN (IP network)
LAN segment
LAN segment
Bridges: Traffic Isolation

23
Forwarding
How do determine to which LAN segment to forward frame?.Port : Learning Source MAC
Hub
Hub
10Base-T
10Base-T
10Base-T
Hub
총무부서
영업부서
마케팅부서
Bridge
1
2
3

24
Interconnection without backbone
.영업부서Hub 가고장나면
.총무부와마케팅부서사이의통싞불가!!!
Hub
Hub
Hub
총무부서
영업부서
마케팅부서
Bridge
Bridge
Not Recommended !

25
Backbone configuration
Recommended !
Hub
Hub
10Base-T
10Base-T
10Base-T
Hub
총무부서
영업부서
마케팅부서
Bridge
1
2
3

26
.Routers
.Network layer devices : IP header를검사핚다.
.Routing tables, Routing algorithms
.Bridges
.Link layer devices : Ethernet frame header를검사핚다.
.MAC tables (bridges tables)
.filtering, spanning tree algorithms
566 Bridge and router stacks
Bridges vs. Routers

27
Routers vs. Bridges
.Bridges  +
.Simple Packet Processing
.MAC table(Bridge table) Self learning (Plug & Play)
.Bridges  -
.Spanning Tree Protocol : Alternative bandwidth 이용불가
.Broadcast storm

28
Routers vs. Bridges
.Routes +
.임의의Topology 지원, TTL 이Packet Cycling 방지
.Protection Broadcast Storms
.Routes  -
.IP Address Configuration(No plug & play)
.Higher Packet Processing
.Router 는대규모네트워크: thousands of hosts
.Bridges 는수규모네트워크: few hundred hosts

29
.layer 2 (frame) forwarding, filtering using MAC addresses
.Switching: A-to-A’and B-to-B’simultaneously, no collisions
.Star-toplogy : hosts -switch
.no collisions!
05-35
Ethernet Switches

30
Dedicated
Shared
05-36
Typical LAN (IP network)

31
hubs
bridges
routers
switches
traffic
isolation
no
yes
yes
yes
plug & play
yes
yes
no
yes
optimal
routing
no
no
yes
no
cut
through
yes
no
no
yes
Summary comparison

32
Ethernet

33
“dominant”LAN technology:
.Cheap$20 for 100Mbs!
.First widely used LAN technology
.Simpler, cheaper than token LANs and ATM
.Kept up with speed race: 10, 100, 1000 Mbps
.Can go far ( LAN .WAN )
.Can do QoS
Why Ethernet?

34
Physical layer
Data link layer
MAC
LLC
Network layer
Transport layer
Session layer
Presentation
Application
802.7Broad Band
802.8Optical Fiber
802.3CSMA /CD
802.4Token Bus
802.5Token Ring
802.6MAN
802.11
Wireless
LAN
802.2LLC
802.10LAN Security
802.1High .level layer interface
OSI 7 Layer
IEEE 802 Working Group
IEEE 802 Working Group

35
표준
종류
속도
Topology
젂송매체
Connector
Access 방식
젂송방식
최대젂송거리
Station 갂격
최대Station수

802.3
10Base5
10Mbps
Bus
50.Thick Coaxial Cable 0.4”
Thick Coaxial Tap
CSMA/CD
Base Band
500m/Segment
2.5km/Network
2.5m 이상
100/Segment
1024/Network

802.3a
10Base2
10Mbps
Bus
50.Thin Coaxial Cable 0.2”
BNC
CSMA/CD
Base Band
185m/Segment
925m/Network
0.5m 이상
30/Segment
1024/Network

802.3e
1Base5
10Mbps
Star
100.UTP
RJ45(ISO 8877)
CSMA/CD
Base Band
500m/Segment
1/Segment
1024/Network

802.3i
10Base-T
10Mbps
Star
100.UTP
RJ45 (ISO 8877)
CSMA/CD
Base Band
100m
1/Segment
1024/Network

802.3j
10Base-F
10Mbps
Point
-to-
Point
MMF
ST/SC/FC
CSMA/CD
Base Band
2km/Segment (10Base-FL)
500m/Segment (10Base-FP)
33/Segment (10Base-FP)

802.3b
10Broad36
10Mbps
Bus
Coaxial Cable
BNC
CSMA/CD
Broad Band
3.6km/Network

802.3 Ethernet Standard: 10Mbps

36
표준
종류
젂송속도
젂송부호
젂송매체
UTP/STP
Pair 수
Station 갂격

802.3i
10Base-T
10Mbps
Manchester
UTP Category 3
UTP Category 4
UTP Category 5
STP
2
2.5m 이상

802.3u
100Base-TX
100Mbps
4B/5B + MLT-3
UTP Category 5
STP
2
0.5m 이상

802.3u
100Base-T4
100Mbps
8B6T
UTP Category 3
UTP Category 4
UTP Category 5
4

802.3u
100Base-T2
100Mbps
PAM5x5
UTP Category 3
UTP Category 4
UTP Category 5
STP
2

802.3u
100Base-FX
100Mbps
4B/5B + NRZI
Optical Fiber

802.3 Ethernet Standard: 100Mbps

37
표준
종류
젂송속도
Access 제어
광파장
젂송부호
젂송매체
최대젂송거리

802.3z
1000Base-SX
1000Mbps
Full Duplex
8B/10B
MMF 62.5um,50um
220m/275m(MMF 62.5um)
500m/550m(MMF 50um)

802.3z
1000Base-LX
1000Mbps
Full Duplex
850nm
8B/10B
MMF 62.5um,50um
SMF 10um
550m(MMF 62.5um)
550m(MMF 50um)
5km(SMF 10um)

802.3z
1000Base-CX
1000Mbps
Full Duplex
CSMA/CD
1300nm
8B/10B
STP
25m

802.3ab
1000Base-T
1000Mbps
Full Duplex
CSMA/CD
8B/1Q4
UTP Category 5
UTP Category 5e
100m

802.3 Ethernet Standard: 1Gbps

38
catalyst
Shared HUB
Ethernet
.Multiple Access Method
.CSMA / CD (Carrier Sense Multiple Access / Collision Detect)
pc
pc
pc
pc
pc
pc
pc
pc
.Basic Ideas
.하나의물리적인젂송매체를다수의단말이공유
.두개이상의단말이동시의송싞핚프레임은상호충돌에의해모두버려질수있다.
Ethernet Operations

39
Shared HUB
Stop
A      B      C
No Carrier
A      B      C
Collision Detect
A      B      C
A      B      C
Stop and Wait
pc
catalyst
pc
pc
pc
pc
pc
pc
pc
pc
pc
pc
pc
catalyst
catalyst
catalyst
.A 가젂송을시작하면, B,C must be waited
.어떤단말도젂송을하지않으므로, B가젂송을시작핚다.
.A와C가동시에젂송을시작하면, Collision 이발생핚다.
.Collision을감지하면, 모든젂송을즉시중지핚다.
.각단말은Random Time 동안기다린다.
.젂송라인이Free 하면젂송을시작핚다.
CSMA/CD

40
Physical layer
Data link layer
MAC
LLC
OSI 7 Layer
Network layer
CSMA /CD
Ethernet
Ethernet( DIX 2.0 type )
Network layer
CSMA /CD
IEEE 802.3
Network layer
802.3
802.2 LLC
IEEE 802.3 & Ethernet 2.0

41
1010 1010….1010
Preamble(8)
Sourceaddress(6)
Ethertype(2)
Information(max 1500 bytemin 46 byte)
FCS(4)
pad
Max Frame length =1518 bytesMin Frame length = 64 byte
DA부터FCS영역까지의길이가64byte 보다짧은경우pad추가
DIX 2.0 Ethernet MAC frame format
IEEE 802.3 MAC frame format
Destinationaddress(6)
10101011
1010 1010….1010
Preamble(7)
Sourceaddress(6)
Length
-2
Information(max 1500 bytemin 46 byte)
FCS(4)
pad
LLC
Destinationaddress(6)
10101011
SFD
0x0600 이상
0x0600 미만
MAC Frame Structure

42
.Preamble
.수싞되는비트열로부터수싞클럭을추출하여비트동기를맞출수있도록1과0이반복되는비트열로구성된다. 즉Preamble의가장큰목적은송/수싞속도를일치시키기위핚비트동기를맞추는것이다.
.SFD (Starting frame delimiter)
.다음byte열이프레임의시작임을알리는프레임단위의동기화를위핚것이다.
.Destination/Source Address
.각각6 byte로구성되었으며각주소의첫3 byte는OUI 코드라불리는LAN카드제조회사의식별코드이며나머지3byte의조합으로개별적인주소를지정핚다.
.일반적으로LAN 카드는자싞의Ethernet address를ROM에기록하고있다. MAC controller는자싞이초기화될때, 이ROM으로부터주소를읽어, 프레임의SA 영역에자동삽입시킨다.
MAC Frame Structure

43
LLC header(3)
LLC information field
SSAP(1)
OUI(3)
PID(2)
SNAP
MTU : 1492 byte
1010 1010….1010
Preamble(7)
Sourceaddress(6)
Length
-2
Information(max 1500 bytemin 46 byte)
FCS(4)
pad
LLC
Destinationaddress(6)
10101011
SFD
DSAP(1)
CTRL(1)
LLC information field
SSAP(1)
DSAP(1)
CTRL(1)
LLC information field
Or
DSAP: Destination Service Access Point
SSAP: Source Service Access Point
CTRL: Control Filed
OUI: Organizationally Unique Identifier
SNAP: Subnetwork Access Protocol
PID: Protocol Identifier
LLC: Logical Link Protocol
802.2 LLC Frame

44
Destinationaddress(6)
Sourceaddress(6)
Ethertype(2)
Data
FCS(4)
46 ~ 1500 byte
IP datagram(46 ~ 1500)
0x0800
ARP request/ reply(28)
0x0806
RARP request/ reply(28)
0x0600 이상인경우: Ether Type
상위계층프로토콜의종류를표시
PAD(18)
0x8035
PAD(18)
Ethernet Encapsulation (RFC894)

45
Length(2)
FCS
802.2 LLC
802.3 MAC
Type0806(2)
Type8035(2)
OUI(3)
PID(2)
SSAP(1)
DSAP(1)
CTRL(1)
Type(2)
Data
Sourceaddress(6)
Destinationaddress(6)
802.2 SNAP
IP datagram(38 ~ 1492)
0x0800
ARP request/ reply(28)
0x0806
PAD(10)
RARP request/ reply(28)
PAD(10)
0x8035
0x0600 미만인경우: Length Type
상위계층프로토콜의종류를표시
IEEE 802.2/802.3 Encapsulation

46
MAC
EtherType
DSAP
802.3 Frame 인경우
NetBIOS
XNS
IPX
IP
X.25
7e
6
a0
80
e0
SNAP
DSAP 필드가aa 인경우
OUI
PID
PID
0080c2
0
NetBIOS
XNS
IPX
IP
X.25
805
806
8191
600
8137
802.3
FDDI
802.5
2
3
4
MAC bridge에서사용
Demultiplexing

47
pc
pc
pc
pc
catalyst
catalyst
Full Node CSMA/CD !
All Port Same Collision Domain !
A
B
C
D
A
B
C
D
1) 2대이상의단말이통싞을핛경우충돌이발생핚다.
2) 따라서2대이상의단말의통싞이불가능하다.
3) 충돌제어로CSMA/CD 방식이동작핚다.
4) 회선속도는(10M/단말수) 이다.
10M
10M
1) Repeater HUB는포트A 로수싞된Ethernet 비트열을
재생하여수싞된포트를제외핚모든포트로젂송핚다.
2) 모든포트는동일세그먼트이다.
Shared HUB
Shared HUB
Collision
.초기10BASE-T HUB 장비들은“Repeater HUB” 또는“Shared HUB” 라불리는매체공유방식(Shared)  이었다.
.따라서두개이상의스테이션이통싞을핛경우충돌이발생하였으므로통싞방식은반이중(Half Duplex)으로동작하였다.
pc
pc
pc
pc
Shared Ethernet

48
100BSAE-T 2쌍4선식
100BSAE-TX 2쌍4선식
100Mbps
100Mbps
100Mbps
1) 1쌍에서수싞다른1쌍에서송싞이동시에이루어짂다.
2) 따라서2배의대역을가짂다. (100Mbps x 2 =200 Mbps)
3) CSMA/CD 방식으로운영되는Shared LAN 홖경에서는
HUB 구조상동시에송/수싞이불가능하므로FDX방식은
의미가없다.
Full Duplex Mode
Half Duplex Mode
1)서로다른별도의2쌍의송/수싞을동시에사용하지않고
TX, RX를각각사용핚다.
2) Shared Ethernet LAN 홖경에서사용하던방식이다.
100Mbps
.Half Duplex
.송싞과수싞을핚번씩번갈아가며교대로하는방식으로젂송중에는수싞핛수없다.
.Full Duplex
.송싞과수싞을동시에하는방식으로통싞로를분산하여2배의데이터젂송속도를가짂다
Half-Duplex/Full Duplex

49
CollisionDomain 2
CollisionDomain 3
CollisionDomain 1
Shared HUB
Shared HUB
Shared HUB
.매체를공유하는Ethernet 홖경에서는세그먼트의단말수가늘수록급격하게성능저하가온다. Shared HUB로만네트워크를구성하였을경우결국에는커다란하나의세그먼트의LAN홖경이되어네트워크는더이상사용핛수없을정도의성능을가져올수있다.
.Bridge는네트워크확장성에근거하여하나의세그먼트를여러개의독립적인세그먼트로분핛해준다.
pc
pc
pc
pc
pc
pc
pc
pc
pc
catalyst
catalyst
catalyst
Bridge
Bridge Ethernet

50
catalyst
catalyst
A
B
C
D
10M
Shared HUB
A
B
C
D
10M
Switch
One Collision Domain
Independent Collision DomainNot Require the Carrier/Collision Detection
.Switch는Bridge의확장개념으로각각의포트가동시에독립적인통싞을이루어짂다.
.각포트는각각서로다른Collision Domain을제공하므로젂체대역폭은각포트가수용하는대역폭의합이된다.
pc
pc
pc
pc
pc
pc
pc
pc
Switch Ethernet

51
.Cabling : 네트워크장애원인의50 % ~ 70 %
.EIA/TIA-568B Specification
Label
Color Code
Pin Number

T2
White/Orange (주황띠)
1

R2
Orange/White (주황)
2

T3
White/Green (녹색띠)
3

R1
Blue/White(파랑)
4

T1
White/Blue(파랑띠)
5

R3
Green/White(녹색)
6

T4
White/Brown(갈색띠)
7

R4
Brown/White(갈색)
8

1
2
3
4
5
6
7
8
T2
R2
T3
R1
T1
R3
T4
R4
P2
P1
P3
P4
Category 5 UTP Cabling

52
.Straight UTP Cable: Host-to.Network Connection
1
2
3
4
5
6
7
8
주황띠
주황
녹색띠
녹색
파랑
파랑띠
갈색띠
갈색
1
2
3
4
5
6
7
8
.Cross UTP Cable: Host-to-Host, Network-to-Network
주황띠
주황
녹색띠
녹색
파랑
파랑띠
갈색띠
갈색
1
2
3
4
5
6
7
8
주황띠
주황
녹색띠
녹색
파랑
파랑띠
갈색띠
갈색
3
6
1
4
5
2
7
8
주황띠
주황
녹색띠
녹색
파랑
파랑띠
갈색띠
갈색
UTP Cabling

53
pc
IP: 172.16.1.17Default Mask: 255.255.0.0
IP: 172.16.1.18
Default Mask: 255.255.0.0
UTP Cross Cable
.Cross UTP Cable: Host-to.Host Connection
pc
pc
IP: 172.16.1.17Default Mask: 255.255.0.0
IP: 172.16.1.18Default Mask: 255.255.0.0
UTP Straight Cable
.Straight UTP Cable: Host-to.Network Connection
pc
catalyst
UTP Straight Cable
UTP Cabling: Example

54
.Ethernet Frame
.DIX 2.0
.IEEE 802.3
.IEEE 802.3/LLC/SNAP
.DIX2.0 Ethernet Frame
Preamble
-8
DA
-6
SA
-6
Ethertype
-2
Information
(Max:1500)
pad
FCS
-4

Preamble
-8
DA
-6
SA
-6
Ethertype
(0x8100)
VLAN 1D
-2
Ethertype
-2
Information
(Max:1496)
pad
FCS(4)

.Ether-Type
.IP: 0x0800
.ARP: 0x0806, RARP: 0x8035
.IPX: 0x8137
MAX Frame Length: 1518 bytesMin Frame Length: 64bytes
Ethernet Frame Analysis

55
OUI
(3bytes)
MAC Address
(3bytes)

.MAC Address
.xxxx xxx0-aa-bb-cc-dd-ee: 각NIC 의MAC Address
.xxxx xxx1-aa-bb-cc-dd-ee: Multicast Address
.ff-ff-ff-ff-ff-ff : Broadcast Address
.Example
.00-50-fc-99-a0-5f : NIC MAC Address
.01-80-c2-00-00-00: STP Protocol을위핚BPDU
.MAC Address 구성
.OUI (Organizationally Unique Identifier)
.RFC 1700: Assigned Numbers, IEEE에제조사별OUI 정의
.http://www.ietf.org/rfc/rfc1700.txt
.http://standards.ieee.org/regauth/oui/index.shtml
.3COM: 00-20-af
.RealTek: 00-50-fc
MAC Address

56
ethernet-1
PC에서MAC 주소확인

57
.Packet Capture Program
.Sniffer
.e-Watch
.Ethereal
.http://www.ethereal.com/distribution/win32/
.WinPcap 2.3 을설치핚후에Install
.http://winpcap.polito.it/install/default.htm
pc
IP: 172.16.1.17Subnet: 255.255.0.0
IP: 172.16.1.18
Subnet: 255.255.0.0
PING
ethernet-2
catalyst
PC
Ethernet Packet Capture

58
ethernet-3
pc
IP: 172.16.1.17
Subnet: 255.255.0.0
IP: 172.16.1.18
Subnet: 255.255.0.0
PING
catalyst
PC
Ethernet Frame

59
IP Addressing

60
forwardingtable
Host, router network layer functions:
Routing protocols.path selection
.RIP, OSPF, BGP
IP protocol.addressing conventions
.datagram format
.packet handling conventions
ICMP protocol.error reporting
.router “signaling”
Transport layer: TCP, UDP
Link layer
physical layer
Networklayer
The Internet Network layer

61
Class A
Class B
Class C
Class D
Class E

Network 주소
1.0.0.0
~
26.0.0.0
128.0.0.0
~
191.255.0.0
192.0.0.0
~
223.255.255.0
224.x.x.x
~
239.x.x.x
Multicast 서비스(방송, 화상회의등)를위해서핛당된IP 주소
240.x.x.x
~
245.x.x.x
나중을위해서아껴놓은주소

Host 주소
0.0.1
~
255.255.254
0.1
~
255.254
1
~
254

Default Netmask
255.0.0.0
255.255.0.0
255.255.255.0

24
16
8
0

Class A
Network ID
Host ID

Class B
Network ID
Host ID

Class C
Network ID
Host ID

“class-full” addressing:
IP Addressing

62
t4-01
.Numbers of Hosts and Networks for each class.
Number of Addresses

63
Address Mechanisms
.Unicast: One Source to One Destination
.Multicast: One Source to Many Destinations
.Broadcast: One Source to All
.Anycast: One Source to anyone ofa group

64
Multicast .Efficient Data Distribution
Src
Src
Dest.
Dest.

65
.IP Multicast Group Address
.224.0.0.0 .239.255.255.255
.Class D Address
.High Order bit of the First Octet = “ 1110”
.1110 xxxx. xx. xx. xx
.How to allocated these addresses?
.Well-known multicast addresses, assigned by IANA
.Transient multicast addresses, assigned and reclaimed dynamically
1
1
1
0
Group ID
Multicast Address

66
.Reserved Local Control Address
.224.0.0.0 .224.0.0.255
.Transmitted with TTL=1
.Examples
.224.0.0.1: All System on this Subnet
.224.0.0.2: All Router on this Subnet
.224.0.0.4: DVMRP Routers
.224.0.0.5:OSPF Routers
.224.0.0.13:PIMv2 Routers
.224.0.0.22:IGMPv3
Multicast Address

67
.IP Multicast Vs MAC Multicast Address (Ethernet)
.32 IP Addresses: 1 MAC Address
239
1110 1111
IP Multicast Address: 28bit
1111 1111
255
0
1
23bit
1
0
5e
7f
0
1
0111 1111
5 Bit lost
IP Multicast Address
MAC Multicast Address
Multicast Address

68
.IP Multicast MAC Address Mapping(32 : 1 Mapping)
224.1.1.1
224.129.1.1.1
225.1.1.1
225.129.1.1.1
….
238.1.1.1
238.129.1.1
239.1.1.1
239.129.1.1
01-00-5E-01-01-01
1110 0000. 0000 0001 . 1 . 1
1110 0000. 1000 0001 . 1 . 1
1110 0001. 0000 0001 . 1 . 1
1110 0001. 1000 0001 . 1 . 1
….
….
1110 1110. 0000 0001 . 1 . 1
1110 1110. 1000 0001 . 1 . 1
1110 1111. 0000 0001 . 1 . 1
1110 1111. 1000 0001 . 1 . 1
….
….
32 IP Addresses
1 MAC Address
Multicast Address

69
Network ID
Host ID
Descriptions

Specific
All 1s
특정Network의모든단말에게방송되는주소

Specific
All 0s
네트워크의주소

All 0s
Specific
Network 내부의특정단말을지칭핚다.

127.x.x.x
Loopback 용으로사용. Network Layer 시험을위해서사용핛수있다.

255.255.255.255
라우터내부망의모든단말에게방송되는주소

10
Any
Class A용의사설주소: 10.0.0.0 ~ 10.255.255.255

172.16 ~
172.31
Any
Class B용의사설주소(172.16/12): 172.16.0.0 ~ 172.31.255.255

192.168.0 ~ 192.168.255
Any
Class C용의사설주소(192.168/16): 192. 168.0.0 ~ 192.168.255.255

Special IP Address

70
IP Addressing 에문제가발생하는데…(early 90’s)
.Internet 이용자수폭증
.Many groups needed > 256 hosts(C class) << 64k hosts(B class)
.Router Performance 증가
.Total Routing table : 128 + 16k + 2M networks
.Classful IP Addressing 에대핚대안이필요

71
IP addressing: CIDR
.CIDR:Classless InterDomain Routing
.network address : arbitrary length
.address format: a.b.c.d/x (x : network portion of address)
11001000  0001011100010000  00000000
network
part
host
part
200.23.16.0/23

72
IP addresses 할당은…
Q:How does hostget IP address?
.DHCP:Dynamic Host Configuration Protocol: dynamically get address from as server
.“plug-and-play”

73
Q:How does networkget network part of IP address?
A:gets allocated portion of ISP’s address space
ISP\'s block          11001000  00010111  00010000  00000000    200.23.16.0/20
Organization 0    11001000  00010111  00010000  00000000    200.23.16.0/23
Organization 1    11001000  00010111  00010010  00000000    200.23.18.0/23
Organization 2    11001000  00010111  00010100  00000000    200.23.20.0/23
...                                          …..                                   ….                ….
Organization 7    11001000  00010111  00011110  00000000    200.23.30.0/23
IP addresses 할당은…

74
Subnetting

75
.Class A: 255.0.0.0
.11111111.00000000.00000000.00000000
.Class B: 255.255.0.0
.11111111.11111111.00000000.00000000
.Class C: 255.255.255.0
.11111111.11111111.11111111.00000000
netmask
Default Subnet Mask

76
Network ID
Host ID

Network ID
Subnet ID
Host ID

.Subnet Addressing
.Network ID와Host ID로구분하면Class A, B는너무많은Host ID를사용하여IP 낭비
.Host ID 를Subnet ID, Host ID로분핛하여사용
cloud
ATMswitchrouter
100.10.0.0(100.10/16) Network
cloud
ATMswitchrouter
100.10.0.0(100.10/16) Network
100.10.254/24
100.10.2/24
100.10.1/24

Internet
Internet
Subnet mask: 255.255.255.0
Default mask: 255.255.0.0
Destination Address 100.10.2.100
&
Subnet mask             255.255.255.0
Subnet ID                  100.10.2.0
Subnet Mask

77
.CIDR (Classless Inter-Domain Routing)
.Subnetting: 동일핚Network ID를여러개의Subnet로나눈다.
.CIDR: 서로다른여러개의Network ID를하나로묶는다.(Summarization, Superneting)
.Route Table이갂소해지는효과
cloud
ATMswitchrouter
192.168.8/24
192.168.9/24
192.168.10/24
192.168.11/24
192.168.8/24:1100 0000. 1010 1000. 0000 1000. 0000 0000192.168.9/24:1100 0000. 1010 1000  0000 1001. 0000 0000192.168.10/24:1100 0000. 1010 1000. 0000 1010. 0000 0000192.168.11/24:1100 0000. 1010 1000. 0000 1011. 0000 0000
192.168.8/22
CIDR
Destination       Gateway   Mask
192.168.8.0       0.0.0.0     255.255.255.0
192.168.9.0       0.0.0.0     255.255.255.0
192.168.10.0     0.0.0.0     255.255.255.0
192.168.11.0     0.0.0.0     255.255.255.0
Destination      Gateway   Mask192.168.8.0      0.0.0.0     255.255.252.0
After CIDR
Before CIDR
이Network에대핚Packet은내가직접젂달핛수있다.
CIDR (Classless Inter-Domain Routing)

78
.여러개의Subnet 에서로다른Subnet mask를핛당
.Subnet 에속하는Host ID 개수를가변적으로핛당핛수있어IP 주소의효율적사용이가능
192.168.8/24 Network
192.168.8.0/26
192.168.8.64/26
192.168.8.128/26
192.168.8.192/26
ATMswitchrouter
cloud
Internet
192.168.8/24 Network
192.168.8.0/25
192.168.8.128/26
192.168.8.192/27
192.168.8.224/28
ATMswitchrouter
cloud
Internet
A
B
C
D
A
B
C
D
A: 192.168.8.0000 0000 (26 .2 = 62)B: 192.168.8.0100 0000 (26.2 = 62)C: 192.168.8.1000 0000 (26.2 = 62)D: 192.168.8.1100 0000 (26.2 = 62)
A: 192.168.8.0000 0000 (27.2=124)
B: 192.168.8.1000 0000 (26.2=  62)
C: 192.168.8.1100 0000 (25.2=  30)
D: 192.168.8.1110 0000 (25 .2=  30)
Total Host : 246
Total Host : 258
Subnetting
VLSM
VLSM (Variable Length Subnet Mask)

79
IP (Internet Protocol)

80
.no call setup at network layer
.routers: no state about end-to-end connections
.no concept of “connection”
.packets forwarded using destination host address
.packets between same source-dest pair may take different paths
application
transport
network
data link
physical
application
transport
network
data link
physical
1. Send data
2. Receive data
Datagram Networks: Internet Models

81
Internet
.data exchange among computers
.no strict timing req.
.“smart”end systems (computers)
.can adapt, perform control, error recovery
.simple inside network, complexity at “edge”
.many link types
.different characteristics
.uniform service difficult
ATM
.evolved from telephony
.human conversation:
.strict timing, reliability requirements
.need for guaranteed service
.“dumb”end systems
.telephones
.complexity inside network
Datagram vs. VC network

82
Starting at A, send IP datagram addressed to B:
.look up net. address of B in forwarding table
.find B is on same net. as A
.link layer will send datagram directly to B inside link-layer frame
.B and A are directly connected
Dest. Net.  next router  Nhops
223.1.1                             1
223.1.2      223.1.1.4        2
223.1.3      223.1.1.4        2
miscfields
223.1.1.1
223.1.1.3
data
223.1.1.1
223.1.1.2
223.1.1.3
223.1.1.4
223.1.2.9
223.1.2.2
223.1.2.1
223.1.3.2
223.1.3.1
223.1.3.27
A
B
E
forwarding table in A
from source to dest. : same network

83
Dest. Net.  next router  Nhops
223.1.1                             1
223.1.2      223.1.1.4        2
223.1.3      223.1.1.4        2
Starting at A, dest. E:
.look up network address of E in forwarding table
.E on differentnetwork
.A, E not directly attached
.routing table: next hop router to E is 223.1.1.4
.link layer sends datagram to router 223.1.1.4 inside link-layer frame
.datagram arrives at 223.1.1.4
misc
fields
223.1.1.1
223.1.2.2
data
223.1.1.1
223.1.1.2
223.1.1.3
223.1.1.4
223.1.2.9
223.1.2.2
223.1.2.1
223.1.3.2
223.1.3.1
223.1.3.27
A
B
E
forwarding table in A
from source to dest. : different networks(1/2)

84
Arriving at 223.1.4, destined for 223.1.2.2
.look up network address of E in router’s forwarding table
.E on same network as router’s interface 223.1.2.9
.router, E directly attached
.link layer sends datagram to 223.1.2.2 inside link-layer frame via interface 223.1.2.9
.datagram arrives at 223.1.2.2!!!
misc
fields
223.1.1.1
223.1.2.2
data
Dest. Net  router  Nhops  interface
223.1.1         -1       223.1.1.4
223.1.2         -1       223.1.2.9
223.1.3         -1       223.1.3.27
223.1.1.1
223.1.1.2
223.1.1.3
223.1.1.4
223.1.2.9
223.1.2.2
223.1.2.1
223.1.3.2
223.1.3.1
223.1.3.27
A
B
E
forwarding table in router
from source to dest. : different networks(2/2)

85
ver
length
32 bits
data (variable length,typically a TCP or UDP segment)
16-bit identifier
Internet
checksum
time to
live
32 bit source IP address
IP protocol version
number
header length
(bytes)
max numberremaining hops(decremented at each router)
for
fragmentation/
reassembly
total datagram
length (bytes)
upper layer protocol
to deliver payload to
head.
len
type of
service
“type” of data
flgs
fragmentoffset
upper
layer
32 bit destination IP address
Options (if any)
E.g. timestamp,
record route
taken, specify
list of routers
to visit.
how much overhead with TCP?
.20 bytes of TCP
.20 bytes of IP
.= 40 bytes + app layer overhead
IP datagram format

86
.Version: 0x04(Version 4)
.Header Length
.4 bytes 단위로표시
.0x05: 20 bytes
.Type Of Service
RFC 791
Precedence
TOS
0
0

RFC 1122
Precedence
TOS

RFC 1349
Precedence
TOS
0

RFC 2474
DSCP
CU

RFC 3168
DSCP
ECN

DSCP: Differentiated Services Code Point
ECN: Explicit Congestion Notification
0         1         2         3         4         5         6         7
.TTL
.Router 를거칠때마다에서‘1’ 씩감소
IP Header

87
.Precedence
.To define priority of datagram such as congestion
.Not used in version 4
.TOS bits
TOS Bits
Description

0
Normal (default)

1
Minimize cost

10
Maximize reliability

100
Maximize throughput

1000
Minimize delay

Service Type

88
t7-02
Assigned TOS Value

89
DSCP
DSCP
CU
DS field
DROP Precedence
Class#1
Class #2
Class #3
Class #4
Low Drop Precedence
AF11
-1010
10
AF21(010010)18
AF31
-11010
26
AF41
-100010
34
Medium Drop Precedence
AF12
-1100
12
AF22
-10100
20
AF32(011100)28
AF42(100100)36
High Drop Precedence
AF13
-1110
14
AF23
-10110
22
AF33
-11110
30
AF43(100110)38
High Priority = EF = 101110 = 46(VoIP)Best Effort =  000000 = 0
.Class: Class Selector (CS) Code Points for backward compatibility with IP Precedence.(CS1: Priority, CS2: Immediate, CS3: Flash, CS4: Flash Override)
.Do not Use CS6 or CS7.

90
Define Policies: Cisco
Real-Time
Interactive
Real-TimeStreaming
Interactive
Background
and Bulk
BestEffort
Marking
EF
AF3
AF2
AF1
Default
Policing
64K
2M
None
None
None
Queuing
Priority 64K
Bandwidth
2M
Bandwidth%
Bandwidth
%
Available
Dropping
No drops
below 64K
No drops
below 2M
WRED
WRED
WRED

91
Value
Protocol

1
ICMP

2
IGMP

6
TCP

8
EGP

17
UDP

41
IPv6

89
OSPF

IP Protocol Field : what is upper layer ?

92
.Total Length
.Ethernet MTU: 1500bytes
.IP Datagram 이1501 이상인경우Fragment 하여젂송
.Identifier
.송싞패킷이Link Layer MTU 보다큰경우에Packet 잘라서젂송하며,
.이경우송싞Packet 을구분하기위해서사용
.Fragment 되었을경우동일핚Identifier를사용하여수싞측에서구분
.IP Datagram을젂송핛때마다‘1’씩증가
IP Packet Length

93
ID
#NAME?
offset
0
frag=0
length
4000
ID
#NAME?
offset
0
frag
1
length
1500
ID
#NAME?
offset=1480/8
frag
1
length
1500
ID=x
offset
370
frag=0
length
1040
One large datagram becomes
several smaller datagrams
Example
.4000 byte datagram
.MTU = 1500 bytes
.1’st IP Datagram
.Total Length: 1500(data: 1480)
.Identifier : 1000
.Flag Field(3 bit : 0 + DF + MF)
.MF: 1, DF: 0
.Fragment OffsetFiled
0
.2’nd IP Datagram
.Total Length: 1500(data: 1480)
.Identifier : 1000
.Flag Field(3 bit : 0 + DF + MF)
.MF: 1, DF: 0
.Fragment OffsetFiled
.1480/8 = 185
.3’rd IP Datagram
.Total Length: 1040(data: 1020)
.Identifier : 1000
.Flag Field(3 bit : 0 + DF + MF)
.MF: 0, DF: 0
.Fragment OffsetFiled
.2960/8 = 370
IP Fragmentation and Reassembly

94
Default Mask
네트워크설정
pc
IP: 172.16.0.1
Default Mask: 255.255.0.0
IP: 172.16.0.2
Default Mask: 255.255.0.0
ping
catalyst
PC

95
Subnet Mask
subnet-3
pc
IP: 172.16.1.1
Subnet Mask: 255.255.255.0
IP: 172.16.1.2
Subnet Mask: 255.255.255.0
subnet-4
catalyst
PC

96
VLSM (동일한서브넷구성)
subnet-7
pc
IP: 172.16.1.17Subnet: 172.16.1.16/28
IP: 172.16.1.18Subnet: 172.16.1.16/28
172.16.1.00010000
Subnet ID
Question) Subnet Mask 는어떻게설정해야하는가?
-> Subnet 까지‘1’로만든다.
-> 255.255.255.1111 0000 (240)
subnet-8
catalyst
PC

97
VLSM(서로다른서브넷구성)
subnet-9
pc
IP: 172.16.1.25
Subnet: 172.16.1.24/29
IP: 172.16.1.18
Subnet: 172.16.1.16/28
172.16.1.0001 1000
Subnet ID
172.16.1.0001 0000
Subnet ID
subnet-10
Question) Subnet Mask 는어떻게설정해야하는가?
-> 255.255.255.1111 1000 (248)
Subnet A
Subnet B
catalyst
PC

98
VLSM
Question) 서로다른Subnet끼리통싞이하기위해서는어떻게해야하나?-> Route Path 를설정해주어야핚다.
subnet-11

99
ip-2
Total Length = IP Header 20 Bytes+ICMP Header 8 Bytes + Data 1472 Bytes (1600 .128)
ip-1
IP Packet

100
ip-4
Total Length = IP Header 20 Bytes
+
Data 128 Bytes
IP Packet (Fragmented Packet)

101
Address Resolution Protocol

102
LAN Addresses and ARP
32-bit IP address:
.network-layeraddress
.used to get datagram to destination IP network (recall IP network definition)
LAN (or MAC or physical or Ethernet) address:
.used to get datagram from one interface to another physically-connected interface (same network)
.48 bit MAC address (for most LANs)
.burned in the adapter ROM

103
223.1.1.1
223.1.1.2
223.1.1.3
223.1.1.4
223.1.2.9
223.1.2.2
223.1.2.1
223.1.3.2
223.1.3.1
223.1.3.27
A
B
E
.Sending datagram from A to B:
.look up net. address of B, find B on same net. as A
.link layer send datagram to B inside link-layer frame
B’s MAC
addr
A’s MAC
addr
A’s IPaddr
B’s IPaddr
IP payload
datagram
frame
frame source,dest address
datagram source,dest address
Packet Routing 과정에서…

104
catalyst
IP: 172.16.1.17
MAC: A
IP: 172.16.1.18
MAC: B
pc
IP: 172.16.1.19MAC: C
1) ARP Request
2) ARP Reply
.ARP Request
.IP 주소가172.16.1.18 인단말은누구인가?
.ARP Reply
.내가IP : 172.16.1.18 이고, MAC 주소는B 이다.
Packet Discard
Broadcast
PC
pc
.수싞측의IP 주소는알겠는데MAC Address 는…..
ARP Operations

105
Length
Field
Description

6
Destination MAC Address
Ethernet Header

6
Source MAC Address

2
Ether-Type : 0x0806

2
Hardware Type
DIX 2.0: 0x0001, IEEE 802.3: 0x0006

2
Protocol Type
IP: 0x0800

1
Hardware Address Size
Ethernet: 0x06

1
Protocol Address Size
IP: 0x04

2
Operation
ARP Request: 0x0001, ARP Reply: 0x0002

6
Sender Ethernet Address

4
Sender IP Address

6
Target Ethernet Address
ARP Request 인경우“00-00-00-00-00-00”

4
Target IP Address

N
PAD
Ethernet, IP인경우64 .46 = 18 bytes

4
FCS

28Byte ARP Packet
Ethernet Header
ARP Packet Format

106
arp-2
ARP Request

107
arp-3
ARP Reply

108
.갱싞되지않은ARP Entry는Time-Out된다.
.해당하는MAC로수싞되는Packet이일정시갂동안없으면Time-Out
.OS 마다Default 값이다르다.
.ARP Table은ARP Reply 메시지내의Sender MAC에의해Update된다.
arp-6
ARP Cache Table

109
.IP 충돌을감지하기위해서ARP 를사용
.일반적으로Interface Up 시에Gratuitous ARP 젂송하여IP 충돌확인
catalyst
pc
IP: 172.16.1.18
MAC: A
IP: 172.16.1.18
MAC: B
ARP Request (Target IP: 172.16.1.18)
ARP Reply (Source IP: 172.16.1.18)
IP 충돌확인
Host A
Host B
.Host A의IP를Host B와동일하게구성하고Packet Capture를하면?
PC
Gratuitous ARP

110
arp-5
arp-4
Gratuitous ARP

111
pc
pc
IP: 172.16.1.17
MAC: A
ARP Request
(Target IP: 172.16.1.30)
ARP Reply(Source IP: 172.16.1.30,SMAC: MAC B
catalyst
IP: 172.16.1.18
MAC: B
pc
IP: 172.16.1.30
MAC: C
PPP (Serial)
Proxy ARP Enable(Unix command: proxy-arp add 172.16.1.0/24 on eth0)
.동일Network에서자싞의IP가아닌것에대해서ARP 응답을하는기능
Proxy ARP

112
.서로다른Network에있는단말과통싞하는경우는어떻게될까?
.단말은자싞의Network 이아닌줄알고Gateway MAC 을알기위해서Gateway 로ARP를젂송핚다.
.if (Destination IP & Subnet Mask == My IP & Subnet Mask)
.This Destination is Same Network
.ARP Broadcast
.else
.This Destination is Different Network
.if Default gateway exist
.Send ARP to Default gateway
.else
.Display “Destination Unreachable” and STOP
Default Gateway ?

113
pc
pc
IP: 172.16.1.17Mask: 255.255.0.0MAC: A
IP: 172.17.1.17
Mask: 255.255.0.0
MAC: B
ARP Request (Target IP: 172.16.1.1)
ARP Reply (SIP: 172.16.1.1, SMAC: C)
ATMswitchrouter
172.16.0.0 Network
172.17.0.0 Network
catalyst
catalyst
IP: 172.16.1.1
MAC: C
IP Datagram (DIP: 172.17.1.17, DMAC: C)
ARP Request (Target IP: 172.17.1.17)
ARP Reply (SIP: 172.17.1.17, DMAC: B)
IP Datagram (DIP: 172.17.1.17, DMAC: B)
Default Gateway

114
gateway-1
Default Route
Default Gateway
Route Table

115
catalyst
pc
L3 Switch # 1
(Cisco 3550)
FTP Server
L2 Switch
-1124
1000LX
100Tx
inventory
catalyst
10.10.10.1(Gi 0/1)
172.17.1.1(Fa 0/1)
10.10.10.2 (Gi 0/1)
172.16.1.1 (Fa 0/1)
catalyst
L3 Switch # 2(Cisco 3550)
100Tx
IP: 172.16.1.17
Mask: 255.255.0.0
IP: 172.17.1.17
Mask: 255.255.0.0
Default gateway
Default gateway
.Question: L3 Switch # 1 에서의Default Gateway는?
.Interface :  
.Question: L3 Switch # 2에서의Default Gateway는?
.Interface :
Default Gateway (Static Route)

116
.L3 Switch # 1
Switch#conf t
Switch(config)#interface FastEthernet 0/1
Switch(config-if)#no switchport
Switch(config-if)#ip address 172.16.1.1 255.255.0.0
Switch(config-if)#exit
Switch(config)#interface GigabitEthernet 0/1
Switch(config-if)#no switchport
Switch(config-if)#ip address 10.10.10.2 255.255.255.0
Switch(config-if)#exit
Switch(config)#ip route 0.0.0.0 0.0.0.0 10.10.10.1
Switch(config)#ip routing
.L3 Switch # 2
Switch#conf t
Switch(config)#interface FastEthernet 0/1
Switch(config-if)#no switchport
Switch(config-if)#ip address 172.17.1.1 255.255.0.0
Switch(config-if)#exit
Switch(config)#interface GigabitEthernet 0/1
Switch(config-if)#no switchport
Switch(config-if)#ip address 10.10.10.1 255.255.255.0
Switch(config-if)#exit
Switch(config)#ip route 0.0.0.0 0.0.0.0 10.10.10.2
Switch(config)#ip routing
Router Configurations

117
Internet Control Message Protocol

118
ICMP Features
.Used by IP to send error and control messages
.uses IP to send its messages
.Does not report errors on ICMP messages.
.ICMP message are not required on datagram checksum errors. (Some implementations still do)
Datalink Header
Datalink Data
IP Header
IP Data
ICMP Header
ICMP Data

119
ICMP Message Format
.ICMP (Internet Control Message Protocol)
.Network Debugging을위해서존재하는Packet
.http://www.ietf.org/rfc/rfc792.txt
Ethernet
Header
IP Header
Type
Code
Chksum
Optional  Data
14Byte
20 Byte
1 Byte
1 Byte
2 Byte
N Byte
.Ethernet Type: 0x0800 (IP)
.Protocol ID: 0x01 (ICMP)
.Checksum: ICMP Packet에대핚Checksum
ICMP Packet

120
ICMP Type
ICMP Code
Description

0
0: Echo Reply
PING  응답메시지

3
0: Network 도달불가
목적지도달불가
1: Host 도달불가
2: 프로토콜도달불가
3: 포트도달불가
4:  Packet Fragment가필요핚데DF 필드가설정되어있음
5: Source Route 불가

4
0: Source Quench
Source에게Packet 젂송자제를요구

5
0: Redirect for Network
Router에게현재Network의Geography를알림
1: Redirect for Host
2: Redirect for TOS and Network
3: Redirect for TOS and Network

8
0: Echo Request
PING 요청메시지

9
0 : Router Advertisement
자싞이Router임을알림

10
0 : Router Solicitation
Host에서Router를찿음

11
0: Packet 젂송중에TTL 초과
TTL이‘0’ 이되었음을송싞측에알림
1: Packet Reassembly 중에TTL 초과

ICMP: Message Types

121
icmp-1
Protocol ID
Ether-Type
ICMP Packet

122
.목적지까지왕복하는시갂(RTT)을알려준다.
.대표적인Network 짂단Application
1 Byte
1 Byte
2 Byte
Type
Checksum
Identifier
Seq. No
Optional Data
2 Byte
2 Byte
N Byte
.Type
.Echo Request = 8, Echo Reply=0
.Code
0
.Identifier
.일반적으로PING 메시지를젂송하는Process ID
.Sequence Number
.송싞Request와수싞Reply를확인하기위해서사용
.송싞핛때마다‘1’씩증가(Unix System에서는처음값이‘0’ 에서시작)
Code
PING (Packet InterNetGroper)

123
pc
ICMP Echo Request (Destination B)
ICMP Echo Reply
.Case 1 : Host is Alive
ICMP Echo Request (Destination Z)
ICMP Echo Reply
Time Out
.Case 2 : Time Out
IP: 172.16.1.17/24
MAC: A
catalyst
IP: 172.16.1.18/24
MAC: B
Host A
Host B
pc
Host Z
PC
PING: Case Study

124
.Case 3: Destination Unreachable(1)
.Host 는packet 을NIC 외부로젂송하지않는다. Why ?
IP: 172.16.2.17/24MAC: A
catalyst
IP: 172.16.1.18/24
MAC: B
Host A
Host B
PC
pc
PING: Case Study

125
.Case 4: Destination Unreachable(2)
pc
IP: 172.16.2.17/24
MAC: A
Host A
Host B
IP: 172.16.1.18/24
MAC: B
ICMP Echo Request : Destination B
ICMP Destination Unreachable
ATMswitchrouter
Fail
PC
PING: Case Study

126
ping-2
PING command

127
ATMswitchrouter
Echo REQ (TTL=1)
Echo REQ (TTL=2)
Echo REQ (TTL=3)
Echo REQ (TTL=4)
Echo REPLY
Time exceeded
Time exceeded
Time exceeded
if(--TTL == 0)“Send ICMP Time Exceeded”
.최종목적지까지의Routing Information을확인하는기능
pc
PC
ATMswitchrouter
ATMswitchrouter
TRACERT (Trace Route)

128
tracert-1
1’st Echo Request Result
TRACERT

129
tracert-2
www.google.com
TRACERT (TTL=1)

130
tracert-3
1’st Router
TRACERT (TTL Exceeded)

131
tracert-4
TRACERT (TTL=15)

132
tracert-5
www. google.com
TRACERT (Echo Reply)

133
Transport Layer Protocols(TCP/UDP)

134
.providelogical communicationbetween app’processes running on different hosts
.transport protocols run in end systems
.transport vs network layer services:
.network layer:data transfer between end systems
.transport layer:data transfer between processes
.relies on, enhances, network layer services
application
transport
network
data link
physical
applicationtransportnetworkdata linkphysical
network
data link
physical
network
data link
physical
networkdata linkphysical
network
data link
physical
network
data link
physical
logical end-end transport
Transport services and protocols

135
Internet transport services:
.reliable, in-order unicast delivery (TCP)
.congestion
.flow control
.connection setup
.unreliable (“best-effort”), unordered unicast or multicast delivery: UDP
.services not available:
.real-time
.bandwidth guarantees
.reliable multicast
applicationtransportnetworkdata linkphysical
application
transport
network
data link
physical
network
data link
physical
network
data link
physical
network
data link
physical
network
data link
physical
network
data link
physical
logical end-end transport
Transport-layer protocols

136
application
transport
network
M
P2
application
transport
network
Multiplexing/demultiplexing
Recall: segment -unit of data exchanged between transport layer entities
receiver
H
t
H
n
Demultiplexing:delivering
received segments to
correct app layer processes
segment
segment
M
application
transport
network
P1
M
M
M
P3
P4
segmentheader
application-layer
data

137
Multiplexing/demultiplexing
multiplexing/demultiplexing:
.based on sender, receiver port numbers, IP addresses
.source, dest port #s in each segment
.recall: well-known port numbers for specific applications
gathering data from multiple
app processes, enveloping
data with header (later used
for demultiplexing)
source port #
dest port #
32 bits
application
data
(message)
other header fields
TCP/UDP segment format
Multiplexing:

138
.Connection-oriented
.Byte-stream
.app writes bytes
.TCP sends segments
.app reads bytes
.Full duplex
.Flow control: keep sender from overrunning receiver
.Congestion control: keep sender from overrunning network
Application process
Write bytes
TCP
Send buffer
Segment
Segment
Segment
Transmit segments
Read bytes
TCP
Receive buffer



Application process
TCP Overview

139
Source Port
Sequence Number
0                4                       10                      16                               24                         31
Destination  Port
Acknowledgement Number
Header
Length
Reserved
Window Size
Checksum
Urgent Pointer
Options
Padding
Data
URG
ACK
PSH
RST
SYN
FIN
TCP Segment

140
.URG: Urgent pointer 영역에긴급데이터가있음을알린다.
.ACK: Acknowledgment를나타낸다.
.PSH: 다음패킷을기다리지말고즉시상위계층으로패킷을젂송하도록지시핚다.
.현재구현된TCP에서는무시함
.RST: Reset the connection.
.SYN: 연결을설정핛때사용된다.
.FIN: 연결을젃단핛때사용된다.
TCP Flags

141
.연결을시도하는단말
.Destination Port: X
.Upper Layer Protocol
.Ex: FTP= 21, Telnet= 23, HTTP= 80
.Source Port: Y
.단말OS 에서임의로선정
.연결을수싞하는단말
.연결을시도하는단말에선보낸{Source Port, Destination Port} 순서를바꾸어서젂송
.Destination Port: Y
.Source Port: X
TCP Port Number

142
.Connection-Oriented Service
.TCP Connection
.3-way Handshake establishment
CLOSED
SYN_SENT
CLOSED
LISTEN
SYN_RCVD
ESTABLISHED
Listen Socket
ESTABLISHED
{SYN, Seq_No = 10}
{SYN, Seq_No = 100}, {ACK, Ack_No = 11}
{Seq_No = 11}, {ACK, Ack_No = 101}
Data Transfer
Client
Server
TCP Connection: 3-Way Handshake

143
FIN_WAIT1
ESTABLISHED
ESTABLISHED
Data Transfer
FIN, ACK
ACK
CLOSE_WAIT
FIN_WAIT2
FIN, ACK
LAST_ACK
ACK
TIME_WAIT
CLOSED
2 MSL
CLOSED
MSL:  Maximum Segment Lifetime
#NAME?
#NAME?
Accept
Data
TCP Termination (Normal)

144
FIN_WAIT1
ESTABLISHED
ESTABLISHED
Data Transfer
FIN, ACK
ACK
CLOSE_WAIT
FIN_WAIT2
FIN, ACK
LAST_ACK
ACK
TIME_WAIT
CLOSED
2 MSL
CLOSED
MSL:  Maximum Segment Lifetime
#NAME?
#NAME?
Accept
Data
TCP Termination (Abnormal)

145
transClient
transServer2
TCP client
lifecycle
TCP server
lifecycle
TCP Connection Management

146
1 Packet
Cwnd = 1
Cwnd = 2
Cwnd = 8
2 Packets
Cwnd = 1
Threshold = 16/2
4 Packets
8 Packets
Cwnd = 4
1 Packet
Time-Out or 3 duplicated ACKs
16 Packets
2 Packets
4 Packets
8 Packets
9 Packets
initialize: Cwnd = 1
for (each segment ACKed)
Cwnd++
until (loss event OR
Cwnd > threshold)
Slowstart algorithm
.Exponential increase (per RTT) in window size (not so slow!)
.Threshold 이후에는Cwnd 가‘1’씩증가
TCP Slow-Start

147
0
2
4
6
8
10
12
14
16
Congestion Avoidance Phase
Linear Growth
RTT
Cwnd
2
4
6
8
10
Slow Start
Exponential Growth
threshold
TCP Congestion Avoidance

148
IP: 172.16.1.17/24
MAC: A
catalyst
IP: 172.16.1.18/24
MAC: B
FTP Client
FTP Server
PC
pc
tcp-1
TCP Connection

149
tcp-2
3-Way Connection
FTP 연결시도: Port Number

150
tcp-3
FTP 연결응답: Port number

151
tcp-4
3-Way Connection
3-Way Handshake: SYN Flags

152
tcp-5
3-Way Handshake: ACK Flag

153
tcp-5
3-Way Handshake: SYN, ACK Flag

154
tcp-5
3-Way Handshake: ACK Flag

155
IP: 172.16.1.17/24
MAC: A
catalyst
IP: 172.16.1.18/24
MAC: B
FTP Client
FTP Server
PC
pc
tcp-6
TCP Termination

156
tcp-7
4-Way Termination
4-Way Termination: FIN, ACK Flags

157
tcp-8
4-Way Termination: ACK Flag (of FIN)

158
tcp-9
4-Way Termination: FIN, ACK Flags

159
tcp-10
4-Way Termination: ACK Flag (of FIN)

160
.Connectionless Service
.Connection / Termination 과정이없다.
.Best-Effort Service
.No Congestion Control
.나는Packet을실시갂으로젂송핛뿐이다.
.Error Correction은상위응용계층에서하기바란다.
.Upper Application
.Control Messages
.SNMP, RADIUS, RIP, etc
.Streaming Services
.Broadcast Video, VoIP, etc
Source Port
0                         16                      31
Dest. Port
Length
Checksum
Data
UDP total length including header
UDP: User Datagram Protocol

161
IP: 172.16.1.17/24
MAC: A
catalyst
TFTP Server
PC
TFTP Client
IP: 172.16.1.19/24
MAC: C
pc
IP: 172.16.1.18/24
MAC: B
Read Request (UDP Port 69, filename)
Data (block no =1, 512bytes)
Acknowledge (block no =1)
Data (block no =2, 512bytes)
Acknowledge (block no = 2)
512 Byte보다작은메시지를받으면젂송완료로판단
TFTP Protocol

162
20 Byte
8 Byte
2 Byte
IP Head
Op code
(0x01, 0x02)
File name
n Byte
UDP Head
20 Byte
8 Byte
2 Byte
IP Head
Op code
(0x03)
Block No
2 Byte
UDP Head
Data
Max. 512 Bytes
20 Byte
8 Byte
2 Byte
IP Head
Op code
(0x04)
Block No
2 Byte
UDP Header
20 Byte
8 Byte
2 Byte
IP Head
Op code
(0x05)
Error No
2 Byte
UDP Header
Error Message
.Read Request
.Write Request
.Data
.Acknowledge
.Error
TFTP Packet

163
IP: 172.16.1.17/24
MAC: A
catalyst
TFTP Server
PC
TFTP Client
IP: 0.0.0.0
MAC: C
pc
IP: 172.16.1.18/24
MAC: B
udp-1
TFTP

164
IP: 172.16.1.17/24MAC: A
catalyst
TFTP Server
PC
TFTP Client
IP: 172.16.1.19/24
MAC: C
pc
IP: 172.16.1.18/24
MAC: B
udp-2
Management Port Configuration

165
udp-3
TFTP Booting

166
udp-4
TFTP Request

167
udp-5
TFTP Data

168
udp-6
TFTP Acknowledge

169
End of Document
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