Abstract image of a woman sitting on books and studying on a laptop

tcpip

Download as PPT, PDF
Nikhil Saxena, profile picture
Nikhil Saxena

This document provides an overview of the TCP/IP protocol suite. It begins by defining what TCP/IP is, noting that it is a set of protocols that allow cooperating computers to share resources across a network. TCP/IP is made up of the TCP and IP protocols at the transport and network layers respectively. The document then discusses specific protocols at each layer, including application layer protocols like FTP, SMTP, and HTTP, as well as transport layer protocols TCP and UDP. It also covers network layer protocols like IP, ARP, and ICMP. The document concludes by discussing TCP/IP addressing schemes and how networks are divided into subnets.

TechnologyEducation
1 of 52
Downloaded 46 times
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP FTP, SMTP, Telnet, HTTP,… TCP, UDP IP, ARP, ICMP Network Interface 9. TCP/IP 1 Reference: Charles L. Hedrick, “Introduction to the Internet Protocols”, Rutgers University, http://oac3.hsc.uth.tmc.edu/staff/snewton/tcp-tutorial/
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP A. What is TCP/IP? • TCP/IP is a set of protocols developed to allow cooperating computers to share resources across a network • TCP stands for “Transmission Control Protocol” • IP stands for “Internet Protocol” • They are Transport layer and Network layer protocols respectively of the protocol suite • The most well known network that adopted TCP/IP is Internet – the biggest WAN in the world 2
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP What is a protocol? • A protocol is a collection of rules and procedures for two computers to exchange information • Protocol also defines the format of data that is being exchanged 3
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Why TCP/IP is so popular? • TCP/IP was developed very early • Technologies were widely discussed and circulated in documents called “Request for Comments” (RFC) – free of charge • Supported by UNIX operating system 4
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP TCP/IP Model • Because TCP/IP was developed earlier than the OSI 7-layer mode, it does not have 7 layers but only 4 layers TCP/IP Protocol Suite FTP, SMTP, Telnet, HTTP,… TCP, UDP IP, ARP, ICMP Network Interface 5 OSI 7-layer
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP • Application layer protocols define the rules when implementing specific network applications • Rely on the underlying layers to provide accurate and efficient data delivery • Typical protocols: 6 • FTP – File Transfer Protocol • For file transfer • Telnet – Remote terminal protocol • For remote login on any other computer on the network • SMTP – Simple Mail Transfer Protocol • For mail transfer • HTTP – Hypertext Transfer Protocol • For Web browsing
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP • TCP/IP is built on “connectionless” technology, each datagram finds its own way to its destination • Transport Layer protocols define the rules of • Dividing a chunk of data into segments • Reassemble segments into the original chunk • Typical protocols: 7 • TCP – Transmission Control Protocol • Provide further the functions such as reordering and data resend • UDP – User Datagram Service • Use when the message to be sent fit exactly into a datagram • Use also when a more simplified data format is required
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP • Network layer protocols define the rules of how to find the routes for a packet to the destination • It only gives best effort delivery. Packets can be delayed, corrupted, lost, duplicated, out-of-order • Typical protocols: • IP – Internet Protocol • Provide packet delivery • ARP – Address Resolution Protocol • Define the procedures of network address / MAC address translation • ICMP – Internet Control Message Protocol • Define the procedures of error message transfer 8
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Application Layer Application Transport Network Network Interface 9
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP B. Example: SMTP SMTP Server Client SMTP Virtual TCP IP, ARP, ICMP Network Interface 10 SMTP TCP Actual IP, ARP, ICMP Network Interface
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP • The underlying layers have guaranteed accurate data delivery • We need to make a lot agreements with the server in application layer before sending mail 11 1. Agree on how data is represented • Binary or ASCII 2. Ensure the right recipient • There may be 1000 users served by the server 3. Ensure the client has the right to send mail • Some clients are not welcome 4. How to tell the server it is the end of the message • All mail looks the same :
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP • Example: SMTP The following mail is to be sent: Date: Fri, 18 Jan 02 13:26:31 EDT From: enpklun@polyu.edu.hk To: tchsun@eee.hku.hk Subject: meeting Let’s get together Monday at 1pm. 12
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Client SMTP Server access port 25 of server 220 eee.hku.hk SMTP Service at 20 Jan 02 05:17:18 EDT HELO polyu.edu.hk 250 eee.hku.hk – Hello, polyu.edu.hk MAIL From: <enpklun@polyu.edu.hk> 250 MAIL accepted 13
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Client SMTP Server RCPT To:<tchsun@eee.hku.hk> 250 Recipient accepted DATA 354 Start mail input; end with . Date: Fri, 18 Jan 02 13:26:31 EDT From: enpklun@polyu.edu.hk To: tchsun@eee.hku.hk Subject: meeting 14 Let’s get together Monday at 1pm. .
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP • The agreement made in the SMTP protocol • All messages use normal text • All ASCII characters • The responses all begin with numbers • To indicate the status when receiving the command • Some words are reserved words • HELO, MAIL, RCPT… • Mail ends with a line that contains only a period • The information passed with the SMTP messages • The recipient name • The sender name • The mail 15
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP C. Domain Name (mentioned before) • Every computer has a network address • e.g. 158.132.161.99 • To access a computer, we need to specify its network address • Human beings are weak in memorizing numbers • We prefer computer name or domain name • e.g. hkpu10.polyu.edu.hk • Need a machine on the Internet to convert name to number 16
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Domain name hierarchy Example: hkpu10.polyu.edu.hk Computer name • The domain within edu.hk • One of the educational institutions in H.K. 17 • The domain within hk • Note: edu.hk is not the same as edu Root domain name other examples: com – commercial company org – general organization net – major network centre gov – government org. mil – militrary group edu – education org.
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP • An organization needs to register its domain name • e.g. PolyU has registered its name to the domain of edu.hk • Once a domain name is assigned, the organization is free to assign other names belong to its domain • e.g. we can have hkpu10.polyu.edu.hk smtp.polyu.edu.hk mail.polyu.edu.hk 18
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Client Where is www.yahoo.com? Domain Name Server (DNS) of polyu.edu.hk usually UDP Address of www.yahoo.com Where is www.yahoo.com? Become client Where is yahoo.com? Address of www.Yahoo.com Address of the DNS of Yahoo.com DNS of Yahoo.com 19 DNS of com
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP • Nevertheless, such a complicated procedure needs not perform in most cases • Client computers usually remember the answers that it got before • It reduces the loading to the root DNS • To further reduce loading, there can be many root DNS on the Internet • e.g. there are a few “com” root DNS 20
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Transport Layer Message Application Segments Transport Network Network Interface 21 h M h M h M
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP D. TCP and UDP TCP – Transmission Control Protocol • TCP is a connection-oriented protocol • Does not mean it has a physical connection between sender and receiver • TCP provides the function to allow a connection virtually exists – also called virtual circuit • TCP provides the functions: • Dividing a chunk of data into segments • Reassembly segments into the original chunk • Provide further the functions such as reordering and data resend 22 • Offering a reliable byte-stream delivery service
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Dividing and Reassembly Source Port TCP Destination Port Sequence Number Acknowledgement Number Message Checksum Message Data 23
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Sender 1 2 Timeout A2 retransmit A1 1 24 Recipient 2 3 A3 3
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP • A Typical Procedure • Sender • TCP divides a message into segments • Add sequence no. • Send the segments in sequence and wait for acknowledgement • If an acknowledgement for a segment is not received for a certain period of time, resend it until an acknowledgement is received • Recipient • When receiving segments, send the acknowledgement with correct number • Reassembly the segments back to the message 25
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Port Multiplexing • A computer may perform a number of network applications at the same time • FTP + SMTP + HTTP, etc. • Each computer has only one network address, how can it serve so many applications at the same time? ⇒ by port multiplexing FTP Port 21 26 Network add: 158.132.161.99 SMTP Port 25 HTTP Port 80
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Well-known Port Numbers • Some port numbers are reserved for some purposes • • • • Port 21: FTP – file transfer Port 25: SMTP – mail transfer Port 23: TELNET – remote login Port 80: HTTP – Web access • These port numbers are well known to all computers in the network • E.g. whenever a client access port 25 of the server, it means the client needs SMTP service 27
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Client SMTP port = 1357 SMTP Server Located by: network address + TCP port no. Source Port = 1357 Destination Port = 25 Sequence Number Acknowledgement Number Checksum 28 Message Data SMTP port = 25
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Client A SMTP + FTP Server Network address: 158.132.161.99 SMTP port = 1357 Client B 29 FTP port = 1361 SMTP port = 25 FTP port = 21
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Network Layer Message Application Segments Transport Network Network Interface 30 h M h h M h M h h M h M h h M Datagrams / Packets
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP E. Network Addresses and Subnets • A header is added to each segment in the Network layer 3 Segment IP Time to Live Protocol Total Length Header CheckSum Source Address Destination Address Segment 31
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP • Total Length – Total length of a packet (up to 65535 bytes) • Time to Live – How many times this packet can be routed on the network (up to 255) • Protocol – The transport layer protocol that the packet belongs to • TCP: 6 • UDP: 17 • ICMP: 1 32 • Source address – the network address of the computer that sends the data • Destination address – the network address of the computer that the data is sending to
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP • (Already mentioned) • Each computer (host) must have a unique network address (or IP address for TCP/IP suite) • Each IP address is 32-bit long (four bytes) • The four-byte address is written out as a.b.c.d • e.g. Byte 1 Byte 2 Byte 3 Byte 4 158 33 132 161 99 • IP addresses are hierarchical • network I.D. and host I.D. • Each Network I.D. on the Internet needs to be registered to the Internet Assigned Number Authority
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Class A – for very large network 1 bit 7 bits 24 bits 0 Net I.D. Host I.D. • Only 27 (63) networks can belong to this class • Each network, there are 224 hosts or computers • Very few class A networks in the world • e.g. Arpanet – the earliest packet switched WAN (started 40 years ago) 34
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Class B – for medium size network 2 bits 1 0 14 bits Net I.D. 16 bits Host I.D. • 214 (16384) networks can belong to this class • Each network, there are 216 (65536) hosts or computers • Polyu’s address belongs to this group • e.g. 158.132.14.1 1001 1110 35 1000 0100 Network I.D. 0000 1110 0000 0001 Host I.D.
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Class C – for small network 3 bits 21 bits 8 bits 1 1 0 Net I.D. Host I.D. • 221 networks can belong to this class • Each network, there are only 28 (256) hosts or computers 36
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Class D – for multicast network 4 bits 1 1 1 0 28 bits Group no. • Packets are addressed to a multicast group • Not often supported on Internet 37
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Special Addresses 38 • Host I.D. = all ‘1’s ⇒ Directed broadcast “Broadcast to all hosts in the network or subnetwork”, not assigned • Host I.D. = all ‘0’s ⇒ “This network”, not assigned • Network I.D. = 127 is reserved for loopback and diagnostic purposes, not assigned • Network I.D. + Host I.D. = all ‘1’s ⇒ Limited broadcast “Broadcast to all hosts in the current network”, not assigned
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Subnets • A class B address can have 65536 hosts • Difficult to manage • Usually subdivide into a few small subnets • Subnetting can also help to reduce broadcasting traffic 158.132.1.0 Router 158.132.0.0 Total 65536 hosts Router 158.132.2.0 158.132.3.0 39 All traffic to 158.132.0.0 All traffic to 158.132.0.0 Each subnet 256 hosts
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Subnet Mask • How does the router know which subnet a packet should go? • For each interface of the router, a subnet mask is provided to redefine which part of the address is Net ID and which part is Host ID • Become classless addressing A subnet mask: 255.255.255.0 1111 1111.1111 1111. 1111 1111. 0000 0000 40 ‘1’s Net ID ‘0’s Host ID
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP 158.132.1.10 Router E0 A packet with destination address 158.132.1.10 S0 S1 S2 Routing Table S0 Subnet Mask AND 41 S1 S2 158.132.1.0 158.132.2.0 158.132.3.0 255.255.255.0 255.255.255.0 255.255.255.0 158.132. 1. 10 255.255.255. 0 158.132. 1. 0 1001 1110.1000 0100.0000 0001.0000 1010 AND 1111 1111.1111 1111.1111 1111.0000 0000 1001 1110.1000 0100.0000 0001.0000 Advantage: easy to compute
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP F. Routing • How a packet finds its way to a computer in a network? • By using Routers • Routing is the selection of a path to guide a packet from the source to the destination • Criteria in selecting a path may be: • Shortest path • Quickest path • Cheapest path 42
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Internet router U.S. 212.64.123.98 The red path is the shortest path 43 Hong Kong 158.132.161.99
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP 44 • Each router has a table that records the estimated distance to all other routers • If a router knows the entire network topology, the shortest path can be calculated • To achieve this, routers broadcast Link State Advertisement to all other routers periodically • By means of routing protocol • Each router knows the exact topology, and then calculates the shortest path • In practice, it is not possible for a router to all paths. Only the nearer ones are kept • Hence can give wrong estimation
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Host A 158.132.148.66 Default gateway: Router C Subnet 158.132.166.0 S0 Router A T0 T1 T0 S1 45 S1 T1 S1 158.132.166.0 Direct 255.255.255.0 T1 160. 64. 0. 0 Forward 255.255. 0. 0 T0 S0 Router C Routing Table Router B T0 Routing Table S0 160. 64.124.0 Direct 255.255.255.0 S1 160. 64.123.0 Direct 255.255.255.0 S0 Subnet 160.64.124.0 S1 Subnet 160.64.123.0 Host B 160.64.123.98
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP 46 1. Host A wants to send a packet to Host B with address 160.64.123.98 2. Host A checks that 160.64.123.98 is not in the same network 3. Send packet to default gateway (Router C) 4. Default gateway finds that it cannot provide the best route for the packet, inform Host A to send the packet to Router A next time 5. Router C sends the packet to Router A 6. Router A checks from the table the packet should forward to Router B 7. Router B receives the packet and checks in its table the packet should directly deliver to subnet 160.64.123.0 8. Host B (160.64.123.98) receives the packet
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Data Link and Physical Layers Message Application Segments Transport Network h M h h M h M h M h h M h h M Packets Network Interface h h h M 47 h h h M Frames
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP G. Ethernet Encapsulation and ARP • An IP packet should be encapsulated into a frame for transmission by data link layer • e.g. if Ethernet (or IEEE 802.3) is used: Preamble Des. Add 7 1 2/6 Bytes Byte Bytes 48 Sour. Add 2/6 Bytes Length IP Packet FCS 2 46 - 1500 Bytes 4 Bytes Bytes IEEE 802.3 Frame
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP • Only the hardware address (MAC address) is unique to a host • Need to convert a network address to MAC address Source IP = 158.132.148.66 Destination IP = 158.132.148.132 Packet Ethernet Packet 49 Ethernet Frame Ethernet address = ?
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP ARP – Address Resolution Protocol Case 1 1. Broadcast: Who has got IP address 158.132.148.132? What’s your Ethernet address? 2. Reply: I do. My Ethernet address is 00-60-8C-41-37-52 3. 50 Ethernet Frame Ethernet address = 00-60-8C-41-37-52
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP ARP – Address Resolution Protocol Case 2 1. Broadcast: Who has got IP address 158.132.148.132? What’s your Ethernet address? Router 3. 2. Reply: The IP you indicated is not in your network. You can give the packet to me first. My MAC address is 00-60-8C-12-34-56 Ethernet Frame 51 Ethernet address = 00-60-8C-12-34-56
ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP ARP Cache • Will have a heavy traffic if so many ARP broadcast messages are generated • Each host will have a cache to store the mappings (from IP to MAC address) that were obtained before IP Address 158.132.148.80 00-60-8C-27-35-9A 158.132.148.28 52 MAC Address 02-60-8C-1A-37-49 • An entry will only be kept in the cache for a limited amount of time (say, 2 minutes)

More Related Content

PPT
Overview of tcp ip
Computing Cage
 
PDF
RHCE administration iii book by moamen hany
Moamen Hany ELNASHAR
 
PDF
RHCE administration ii book by Moamen Hany
Moamen Hany ELNASHAR
 
PDF
RHCE I Essential book by Moamen Hany
Moamen Hany ELNASHAR
 
PPTX
HyperText Transfer Protocol (HTTP)
Gurjot Singh
 
PPSX
HTTP Presentation
Lana Dujanovic
 
PPTX
Http Introduction
Akshay Dhole
 
PPT
Working on internet
Online
 
Overview of tcp ip
Computing Cage
 
RHCE administration iii book by moamen hany
Moamen Hany ELNASHAR
 
RHCE administration ii book by Moamen Hany
Moamen Hany ELNASHAR
 
RHCE I Essential book by Moamen Hany
Moamen Hany ELNASHAR
 
HyperText Transfer Protocol (HTTP)
Gurjot Singh
 
HTTP Presentation
Lana Dujanovic
 
Http Introduction
Akshay Dhole
 
Working on internet
Online
 

What's hot (20)

PPT
Wireshark working and basics
M A Hafeez
 
PDF
InternetWorking With TCP\IP
hunghanamhus
 
PPTX
Http Protocol
N R Z Malik
 
PPTX
Analogue_GlenBrumpton_NUCUG_Final_1.2_Cleaned
Glen Brumpton
 
PPT
Web Server Technologies I: HTTP & Getting Started
Port80 Software
 
PDF
PLNOG 9: Ivan Pepelnjak - OpenFlow and SDN: hype, useful tools or panacea?
PROIDEA
 
PPTX
02 coms 525 tcpip - introduction to tcpip
Palanivel Kuppusamy
 
PPTX
TCPLS presentation @ietf 109
Olivier Bonaventure
 
PPTX
Innovation is back in the transport and network layers
Olivier Bonaventure
 
PPT
US07FFT-mod_ftp.ppt
webhostingguy
 
PDF
HTTP
Daniel Kummer
 
PPTX
Solving the Problems of FTP
FileCatalyst
 
PPTX
Network testing and debugging
SADEED AMEEN
 
PDF
The Application Layer
adil raja
 
PPTX
Part 6 : Internet applications
Olivier Bonaventure
 
PDF
[Advantech] ADAM-3600 open vpn setting Tutorial step by step
Ming-Hung Hseih
 
PDF
Indroduction to SIP
Chien Cheng Wu
 
PPT
Net essentials6e ch5
APSU
 
PDF
Hypertexttransferprotocolhttp 131012171813-phpapp02
Nidhitransport
 
PPTX
10 routing-bgp
Olivier Bonaventure
 
Wireshark working and basics
M A Hafeez
 
InternetWorking With TCP\IP
hunghanamhus
 
Http Protocol
N R Z Malik
 
Analogue_GlenBrumpton_NUCUG_Final_1.2_Cleaned
Glen Brumpton
 
Web Server Technologies I: HTTP & Getting Started
Port80 Software
 
PLNOG 9: Ivan Pepelnjak - OpenFlow and SDN: hype, useful tools or panacea?
PROIDEA
 
02 coms 525 tcpip - introduction to tcpip
Palanivel Kuppusamy
 
TCPLS presentation @ietf 109
Olivier Bonaventure
 
Innovation is back in the transport and network layers
Olivier Bonaventure
 
US07FFT-mod_ftp.ppt
webhostingguy
 
HTTP
Daniel Kummer
 
Solving the Problems of FTP
FileCatalyst
 
Network testing and debugging
SADEED AMEEN
 
The Application Layer
adil raja
 
Part 6 : Internet applications
Olivier Bonaventure
 
[Advantech] ADAM-3600 open vpn setting Tutorial step by step
Ming-Hung Hseih
 
Indroduction to SIP
Chien Cheng Wu
 
Net essentials6e ch5
APSU
 
Hypertexttransferprotocolhttp 131012171813-phpapp02
Nidhitransport
 
10 routing-bgp
Olivier Bonaventure
 
Ad

Viewers also liked (20)

PPTX
WiFi for mobile networks
t_bindseil
 
PPTX
Computer networks protocols
Mustafa Qamar-ud-Din
 
PPTX
basic it presentation........
vlsaroj
 
PDF
Firewall fundamentals
Thang Man
 
PPTX
Ipv4 &amp; ipv6
alibefkani
 
PPT
Firewall Essentials
Sylvain Maret
 
PPT
TCP/IP
Syed Zaid Irshad
 
PPT
Firewall Penetration Testing
Chirag Jain
 
PPTX
Presentation on dns
Anand Grewal
 
PPTX
Domain name system
Siddharth Chandel
 
PPT
Smtp
Eri Alam
 
ODP
Introduction to DNS
Jonathan Oxer
 
PPTX
TCP/IP Model
farhan516
 
PDF
Presentation on Domain Name System
Chinmay Joshi
 
PPTX
File Transfer Protocol
guest029bcd
 
PPTX
Domain Name System DNS
Akshay Tiwari
 
PDF
DNS - Domain Name System
Peter R. Egli
 
PPTX
Amplitude Modulation ppt
Priyanka Mathur
 
PPT
5. icmp
Swati Arora
 
PDF
TCP/IP – Transmission Control Protocol/ Internet Protocol
We Learn - A Continuous Learning Forum from Welingkar's Distance Learning Program.
 
WiFi for mobile networks
t_bindseil
 
Computer networks protocols
Mustafa Qamar-ud-Din
 
basic it presentation........
vlsaroj
 
Firewall fundamentals
Thang Man
 
Ipv4 &amp; ipv6
alibefkani
 
Firewall Essentials
Sylvain Maret
 
TCP/IP
Syed Zaid Irshad
 
Firewall Penetration Testing
Chirag Jain
 
Presentation on dns
Anand Grewal
 
Domain name system
Siddharth Chandel
 
Smtp
Eri Alam
 
Introduction to DNS
Jonathan Oxer
 
TCP/IP Model
farhan516
 
Presentation on Domain Name System
Chinmay Joshi
 
File Transfer Protocol
guest029bcd
 
Domain Name System DNS
Akshay Tiwari
 
DNS - Domain Name System
Peter R. Egli
 
Amplitude Modulation ppt
Priyanka Mathur
 
5. icmp
Swati Arora
 
TCP/IP – Transmission Control Protocol/ Internet Protocol
We Learn - A Continuous Learning Forum from Welingkar's Distance Learning Program.
 
Ad

Similar to tcpip (20)

PPT
TCP/ IP
Harshit Srivastava
 
PPT
tcp ip protocols.ppt
ssuser3acfba
 
PPT
The Internet protocol suite, commonly known as TCP/IP, is a framework for org...
MathivananP4
 
PPT
TCP/IP Protocol Suite model Transmission Control Protocol
27230106
 
PPTX
tcp-140613123317-phpapp01.pptx
touseeqzulfiqar1
 
PPT
Web Engineering Lecture2
Muhammad Tahir Mehmood
 
PPT
Overview of TCP IP
university of education,Lahore
 
PPT
lecture03for socket programming college.ppt
SoumabhaRoy
 
PPT
lecture03 on socket programming000000.ppt
SoumabhaRoy
 
PPTX
Tcp/ip
Mohd Saleem
 
PPTX
User Datagram Protocol
Purushottam Kamble
 
PPT
Comptia Security + Chapter 1 501
AbdulalimBhnsawy
 
PPTX
Computer network coe351- part2- final
Taymoor Nazmy
 
PPT
testppt ch01(1)
ryaekle
 
PPTX
Transmission Control Protocol (TCP) Basics
jinijames109
 
PDF
Transport Layer Numericals
Manisha Keim
 
PPTX
Networking in python by Rj
Shree M.L.Kakadiya MCA mahila college, Amreli
 
PDF
ADDRESSING PADA TCP IP
Jennifer Daniel
 
PDF
Primer to Browser Netwroking
Shuya Osaki
 
PPTX
Building the Internet of Things with Thingsquare and Contiki - day 2 part 2
Adam Dunkels
 
TCP/ IP
Harshit Srivastava
 
tcp ip protocols.ppt
ssuser3acfba
 
The Internet protocol suite, commonly known as TCP/IP, is a framework for org...
MathivananP4
 
TCP/IP Protocol Suite model Transmission Control Protocol
27230106
 
tcp-140613123317-phpapp01.pptx
touseeqzulfiqar1
 
Web Engineering Lecture2
Muhammad Tahir Mehmood
 
Overview of TCP IP
university of education,Lahore
 
lecture03for socket programming college.ppt
SoumabhaRoy
 
lecture03 on socket programming000000.ppt
SoumabhaRoy
 
Tcp/ip
Mohd Saleem
 
User Datagram Protocol
Purushottam Kamble
 
Comptia Security + Chapter 1 501
AbdulalimBhnsawy
 
Computer network coe351- part2- final
Taymoor Nazmy
 
testppt ch01(1)
ryaekle
 
Transmission Control Protocol (TCP) Basics
jinijames109
 
Transport Layer Numericals
Manisha Keim
 
Networking in python by Rj
Shree M.L.Kakadiya MCA mahila college, Amreli
 
ADDRESSING PADA TCP IP
Jennifer Daniel
 
Primer to Browser Netwroking
Shuya Osaki
 
Building the Internet of Things with Thingsquare and Contiki - day 2 part 2
Adam Dunkels
 

Recently uploaded (20)

PDF
CloudStack 4.21: First Look Webinar slides
ShapeBlue
 
PDF
Architecture types and enterprise applications.pdf
ChristopherTHyatt
 
PDF
A Late Bloomer's Guide to GenAI: Ethics, Bias, and Effective Prompting - Boha...
Mindy Bohannon
 
PPTX
Benefits of Physical activity for teenagers.pptx
Nokwanda Thabethe
 
PDF
Univ-Connecticut-ChatGPT-Presentaion.pdf
ry7r52mzb4
 
PPTX
Group 1 Presentation -Planning and Decision Making .pptx
MatthewLewis227954
 
PDF
Five Habits of High-Impact Board Members
OnBoard
 
PPTX
Web Crawler for Trend Tracking Gen Z Insights.pptx
Actowiz Solustions
 
PPTX
O2C Customer Invoices to Receipt V15A.pptx
ssuserbfa915
 
PDF
Getting started with AI Agents and Multi-Agent Systems
Maxim Salnikov
 
PDF
Enhancing emotion recognition model for a student engagement use case through...
IAESIJAI
 
PDF
A contest of sentiment analysis: k-nearest neighbor versus neural network
IAESIJAI
 
PDF
August Patch Tuesday
Ivanti
 
PPTX
MicrosoftCybserSecurityReferenceArchitecture-April-2025.pptx
SilvioHayashi
 
PPTX
Tartificialntelligence_presentation.pptx
ry7r52mzb4
 
PDF
ENT215_Completing-a-large-scale-migration-and-modernization-with-AWS.pdf
ssuser28425f
 
PPT
Geologic Time for studying geology for geologist
ssuser738f5a
 
PPT
Module 1.ppt Iot fundamentals and Architecture
nanditha7766
 
PDF
Zenith AI: Advanced Artificial Intelligence
Biz Preneurs
 
PDF
1 - Historical Antecedents, Social Consideration.pdf
tuazon2030627
 
CloudStack 4.21: First Look Webinar slides
ShapeBlue
 
Architecture types and enterprise applications.pdf
ChristopherTHyatt
 
A Late Bloomer's Guide to GenAI: Ethics, Bias, and Effective Prompting - Boha...
Mindy Bohannon
 
Benefits of Physical activity for teenagers.pptx
Nokwanda Thabethe
 
Univ-Connecticut-ChatGPT-Presentaion.pdf
ry7r52mzb4
 
Group 1 Presentation -Planning and Decision Making .pptx
MatthewLewis227954
 
Five Habits of High-Impact Board Members
OnBoard
 
Web Crawler for Trend Tracking Gen Z Insights.pptx
Actowiz Solustions
 
O2C Customer Invoices to Receipt V15A.pptx
ssuserbfa915
 
Getting started with AI Agents and Multi-Agent Systems
Maxim Salnikov
 
Enhancing emotion recognition model for a student engagement use case through...
IAESIJAI
 
A contest of sentiment analysis: k-nearest neighbor versus neural network
IAESIJAI
 
August Patch Tuesday
Ivanti
 
MicrosoftCybserSecurityReferenceArchitecture-April-2025.pptx
SilvioHayashi
 
Tartificialntelligence_presentation.pptx
ry7r52mzb4
 
ENT215_Completing-a-large-scale-migration-and-modernization-with-AWS.pdf
ssuser28425f
 
Geologic Time for studying geology for geologist
ssuser738f5a
 
Module 1.ppt Iot fundamentals and Architecture
nanditha7766
 
Zenith AI: Advanced Artificial Intelligence
Biz Preneurs
 
1 - Historical Antecedents, Social Consideration.pdf
tuazon2030627
 

tcpip

  • 1. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP FTP, SMTP, Telnet, HTTP,… TCP, UDP IP, ARP, ICMP Network Interface 9. TCP/IP 1 Reference: Charles L. Hedrick, “Introduction to the Internet Protocols”, Rutgers University, http://oac3.hsc.uth.tmc.edu/staff/snewton/tcp-tutorial/
  • 2. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP A. What is TCP/IP? • TCP/IP is a set of protocols developed to allow cooperating computers to share resources across a network • TCP stands for “Transmission Control Protocol” • IP stands for “Internet Protocol” • They are Transport layer and Network layer protocols respectively of the protocol suite • The most well known network that adopted TCP/IP is Internet – the biggest WAN in the world 2
  • 3. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP What is a protocol? • A protocol is a collection of rules and procedures for two computers to exchange information • Protocol also defines the format of data that is being exchanged 3
  • 4. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Why TCP/IP is so popular? • TCP/IP was developed very early • Technologies were widely discussed and circulated in documents called “Request for Comments” (RFC) – free of charge • Supported by UNIX operating system 4
  • 5. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP TCP/IP Model • Because TCP/IP was developed earlier than the OSI 7-layer mode, it does not have 7 layers but only 4 layers TCP/IP Protocol Suite FTP, SMTP, Telnet, HTTP,… TCP, UDP IP, ARP, ICMP Network Interface 5 OSI 7-layer
  • 6. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP • Application layer protocols define the rules when implementing specific network applications • Rely on the underlying layers to provide accurate and efficient data delivery • Typical protocols: 6 • FTP – File Transfer Protocol • For file transfer • Telnet – Remote terminal protocol • For remote login on any other computer on the network • SMTP – Simple Mail Transfer Protocol • For mail transfer • HTTP – Hypertext Transfer Protocol • For Web browsing
  • 7. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP • TCP/IP is built on “connectionless” technology, each datagram finds its own way to its destination • Transport Layer protocols define the rules of • Dividing a chunk of data into segments • Reassemble segments into the original chunk • Typical protocols: 7 • TCP – Transmission Control Protocol • Provide further the functions such as reordering and data resend • UDP – User Datagram Service • Use when the message to be sent fit exactly into a datagram • Use also when a more simplified data format is required
  • 8. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP • Network layer protocols define the rules of how to find the routes for a packet to the destination • It only gives best effort delivery. Packets can be delayed, corrupted, lost, duplicated, out-of-order • Typical protocols: • IP – Internet Protocol • Provide packet delivery • ARP – Address Resolution Protocol • Define the procedures of network address / MAC address translation • ICMP – Internet Control Message Protocol • Define the procedures of error message transfer 8
  • 9. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Application Layer Application Transport Network Network Interface 9
  • 10. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP B. Example: SMTP SMTP Server Client SMTP Virtual TCP IP, ARP, ICMP Network Interface 10 SMTP TCP Actual IP, ARP, ICMP Network Interface
  • 11. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP • The underlying layers have guaranteed accurate data delivery • We need to make a lot agreements with the server in application layer before sending mail 11 1. Agree on how data is represented • Binary or ASCII 2. Ensure the right recipient • There may be 1000 users served by the server 3. Ensure the client has the right to send mail • Some clients are not welcome 4. How to tell the server it is the end of the message • All mail looks the same :
  • 12. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP • Example: SMTP The following mail is to be sent: Date: Fri, 18 Jan 02 13:26:31 EDT From: enpklun@polyu.edu.hk To: tchsun@eee.hku.hk Subject: meeting Let’s get together Monday at 1pm. 12
  • 13. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Client SMTP Server access port 25 of server 220 eee.hku.hk SMTP Service at 20 Jan 02 05:17:18 EDT HELO polyu.edu.hk 250 eee.hku.hk – Hello, polyu.edu.hk MAIL From: <enpklun@polyu.edu.hk> 250 MAIL accepted 13
  • 14. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Client SMTP Server RCPT To:<tchsun@eee.hku.hk> 250 Recipient accepted DATA 354 Start mail input; end with . Date: Fri, 18 Jan 02 13:26:31 EDT From: enpklun@polyu.edu.hk To: tchsun@eee.hku.hk Subject: meeting 14 Let’s get together Monday at 1pm. .
  • 15. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP • The agreement made in the SMTP protocol • All messages use normal text • All ASCII characters • The responses all begin with numbers • To indicate the status when receiving the command • Some words are reserved words • HELO, MAIL, RCPT… • Mail ends with a line that contains only a period • The information passed with the SMTP messages • The recipient name • The sender name • The mail 15
  • 16. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP C. Domain Name (mentioned before) • Every computer has a network address • e.g. 158.132.161.99 • To access a computer, we need to specify its network address • Human beings are weak in memorizing numbers • We prefer computer name or domain name • e.g. hkpu10.polyu.edu.hk • Need a machine on the Internet to convert name to number 16
  • 17. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Domain name hierarchy Example: hkpu10.polyu.edu.hk Computer name • The domain within edu.hk • One of the educational institutions in H.K. 17 • The domain within hk • Note: edu.hk is not the same as edu Root domain name other examples: com – commercial company org – general organization net – major network centre gov – government org. mil – militrary group edu – education org.
  • 18. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP • An organization needs to register its domain name • e.g. PolyU has registered its name to the domain of edu.hk • Once a domain name is assigned, the organization is free to assign other names belong to its domain • e.g. we can have hkpu10.polyu.edu.hk smtp.polyu.edu.hk mail.polyu.edu.hk 18
  • 19. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Client Where is www.yahoo.com? Domain Name Server (DNS) of polyu.edu.hk usually UDP Address of www.yahoo.com Where is www.yahoo.com? Become client Where is yahoo.com? Address of www.Yahoo.com Address of the DNS of Yahoo.com DNS of Yahoo.com 19 DNS of com
  • 20. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP • Nevertheless, such a complicated procedure needs not perform in most cases • Client computers usually remember the answers that it got before • It reduces the loading to the root DNS • To further reduce loading, there can be many root DNS on the Internet • e.g. there are a few “com” root DNS 20
  • 21. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Transport Layer Message Application Segments Transport Network Network Interface 21 h M h M h M
  • 22. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP D. TCP and UDP TCP – Transmission Control Protocol • TCP is a connection-oriented protocol • Does not mean it has a physical connection between sender and receiver • TCP provides the function to allow a connection virtually exists – also called virtual circuit • TCP provides the functions: • Dividing a chunk of data into segments • Reassembly segments into the original chunk • Provide further the functions such as reordering and data resend 22 • Offering a reliable byte-stream delivery service
  • 23. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Dividing and Reassembly Source Port TCP Destination Port Sequence Number Acknowledgement Number Message Checksum Message Data 23
  • 24. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Sender 1 2 Timeout A2 retransmit A1 1 24 Recipient 2 3 A3 3
  • 25. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP • A Typical Procedure • Sender • TCP divides a message into segments • Add sequence no. • Send the segments in sequence and wait for acknowledgement • If an acknowledgement for a segment is not received for a certain period of time, resend it until an acknowledgement is received • Recipient • When receiving segments, send the acknowledgement with correct number • Reassembly the segments back to the message 25
  • 26. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Port Multiplexing • A computer may perform a number of network applications at the same time • FTP + SMTP + HTTP, etc. • Each computer has only one network address, how can it serve so many applications at the same time? ⇒ by port multiplexing FTP Port 21 26 Network add: 158.132.161.99 SMTP Port 25 HTTP Port 80
  • 27. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Well-known Port Numbers • Some port numbers are reserved for some purposes • • • • Port 21: FTP – file transfer Port 25: SMTP – mail transfer Port 23: TELNET – remote login Port 80: HTTP – Web access • These port numbers are well known to all computers in the network • E.g. whenever a client access port 25 of the server, it means the client needs SMTP service 27
  • 28. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Client SMTP port = 1357 SMTP Server Located by: network address + TCP port no. Source Port = 1357 Destination Port = 25 Sequence Number Acknowledgement Number Checksum 28 Message Data SMTP port = 25
  • 29. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Client A SMTP + FTP Server Network address: 158.132.161.99 SMTP port = 1357 Client B 29 FTP port = 1361 SMTP port = 25 FTP port = 21
  • 30. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Network Layer Message Application Segments Transport Network Network Interface 30 h M h h M h M h h M h M h h M Datagrams / Packets
  • 31. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP E. Network Addresses and Subnets • A header is added to each segment in the Network layer 3 Segment IP Time to Live Protocol Total Length Header CheckSum Source Address Destination Address Segment 31
  • 32. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP • Total Length – Total length of a packet (up to 65535 bytes) • Time to Live – How many times this packet can be routed on the network (up to 255) • Protocol – The transport layer protocol that the packet belongs to • TCP: 6 • UDP: 17 • ICMP: 1 32 • Source address – the network address of the computer that sends the data • Destination address – the network address of the computer that the data is sending to
  • 33. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP • (Already mentioned) • Each computer (host) must have a unique network address (or IP address for TCP/IP suite) • Each IP address is 32-bit long (four bytes) • The four-byte address is written out as a.b.c.d • e.g. Byte 1 Byte 2 Byte 3 Byte 4 158 33 132 161 99 • IP addresses are hierarchical • network I.D. and host I.D. • Each Network I.D. on the Internet needs to be registered to the Internet Assigned Number Authority
  • 34. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Class A – for very large network 1 bit 7 bits 24 bits 0 Net I.D. Host I.D. • Only 27 (63) networks can belong to this class • Each network, there are 224 hosts or computers • Very few class A networks in the world • e.g. Arpanet – the earliest packet switched WAN (started 40 years ago) 34
  • 35. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Class B – for medium size network 2 bits 1 0 14 bits Net I.D. 16 bits Host I.D. • 214 (16384) networks can belong to this class • Each network, there are 216 (65536) hosts or computers • Polyu’s address belongs to this group • e.g. 158.132.14.1 1001 1110 35 1000 0100 Network I.D. 0000 1110 0000 0001 Host I.D.
  • 36. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Class C – for small network 3 bits 21 bits 8 bits 1 1 0 Net I.D. Host I.D. • 221 networks can belong to this class • Each network, there are only 28 (256) hosts or computers 36
  • 37. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Class D – for multicast network 4 bits 1 1 1 0 28 bits Group no. • Packets are addressed to a multicast group • Not often supported on Internet 37
  • 38. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Special Addresses 38 • Host I.D. = all ‘1’s ⇒ Directed broadcast “Broadcast to all hosts in the network or subnetwork”, not assigned • Host I.D. = all ‘0’s ⇒ “This network”, not assigned • Network I.D. = 127 is reserved for loopback and diagnostic purposes, not assigned • Network I.D. + Host I.D. = all ‘1’s ⇒ Limited broadcast “Broadcast to all hosts in the current network”, not assigned
  • 39. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Subnets • A class B address can have 65536 hosts • Difficult to manage • Usually subdivide into a few small subnets • Subnetting can also help to reduce broadcasting traffic 158.132.1.0 Router 158.132.0.0 Total 65536 hosts Router 158.132.2.0 158.132.3.0 39 All traffic to 158.132.0.0 All traffic to 158.132.0.0 Each subnet 256 hosts
  • 40. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Subnet Mask • How does the router know which subnet a packet should go? • For each interface of the router, a subnet mask is provided to redefine which part of the address is Net ID and which part is Host ID • Become classless addressing A subnet mask: 255.255.255.0 1111 1111.1111 1111. 1111 1111. 0000 0000 40 ‘1’s Net ID ‘0’s Host ID
  • 41. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP 158.132.1.10 Router E0 A packet with destination address 158.132.1.10 S0 S1 S2 Routing Table S0 Subnet Mask AND 41 S1 S2 158.132.1.0 158.132.2.0 158.132.3.0 255.255.255.0 255.255.255.0 255.255.255.0 158.132. 1. 10 255.255.255. 0 158.132. 1. 0 1001 1110.1000 0100.0000 0001.0000 1010 AND 1111 1111.1111 1111.1111 1111.0000 0000 1001 1110.1000 0100.0000 0001.0000 Advantage: easy to compute
  • 42. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP F. Routing • How a packet finds its way to a computer in a network? • By using Routers • Routing is the selection of a path to guide a packet from the source to the destination • Criteria in selecting a path may be: • Shortest path • Quickest path • Cheapest path 42
  • 43. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Internet router U.S. 212.64.123.98 The red path is the shortest path 43 Hong Kong 158.132.161.99
  • 44. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP 44 • Each router has a table that records the estimated distance to all other routers • If a router knows the entire network topology, the shortest path can be calculated • To achieve this, routers broadcast Link State Advertisement to all other routers periodically • By means of routing protocol • Each router knows the exact topology, and then calculates the shortest path • In practice, it is not possible for a router to all paths. Only the nearer ones are kept • Hence can give wrong estimation
  • 45. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Host A 158.132.148.66 Default gateway: Router C Subnet 158.132.166.0 S0 Router A T0 T1 T0 S1 45 S1 T1 S1 158.132.166.0 Direct 255.255.255.0 T1 160. 64. 0. 0 Forward 255.255. 0. 0 T0 S0 Router C Routing Table Router B T0 Routing Table S0 160. 64.124.0 Direct 255.255.255.0 S1 160. 64.123.0 Direct 255.255.255.0 S0 Subnet 160.64.124.0 S1 Subnet 160.64.123.0 Host B 160.64.123.98
  • 46. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP 46 1. Host A wants to send a packet to Host B with address 160.64.123.98 2. Host A checks that 160.64.123.98 is not in the same network 3. Send packet to default gateway (Router C) 4. Default gateway finds that it cannot provide the best route for the packet, inform Host A to send the packet to Router A next time 5. Router C sends the packet to Router A 6. Router A checks from the table the packet should forward to Router B 7. Router B receives the packet and checks in its table the packet should directly deliver to subnet 160.64.123.0 8. Host B (160.64.123.98) receives the packet
  • 47. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP Data Link and Physical Layers Message Application Segments Transport Network h M h h M h M h M h h M h h M Packets Network Interface h h h M 47 h h h M Frames
  • 48. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP G. Ethernet Encapsulation and ARP • An IP packet should be encapsulated into a frame for transmission by data link layer • e.g. if Ethernet (or IEEE 802.3) is used: Preamble Des. Add 7 1 2/6 Bytes Byte Bytes 48 Sour. Add 2/6 Bytes Length IP Packet FCS 2 46 - 1500 Bytes 4 Bytes Bytes IEEE 802.3 Frame
  • 49. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP • Only the hardware address (MAC address) is unique to a host • Need to convert a network address to MAC address Source IP = 158.132.148.66 Destination IP = 158.132.148.132 Packet Ethernet Packet 49 Ethernet Frame Ethernet address = ?
  • 50. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP ARP – Address Resolution Protocol Case 1 1. Broadcast: Who has got IP address 158.132.148.132? What’s your Ethernet address? 2. Reply: I do. My Ethernet address is 00-60-8C-41-37-52 3. 50 Ethernet Frame Ethernet address = 00-60-8C-41-37-52
  • 51. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP ARP – Address Resolution Protocol Case 2 1. Broadcast: Who has got IP address 158.132.148.132? What’s your Ethernet address? Router 3. 2. Reply: The IP you indicated is not in your network. You can give the packet to me first. My MAC address is 00-60-8C-12-34-56 Ethernet Frame 51 Ethernet address = 00-60-8C-12-34-56
  • 52. ENG224 INFORMATION TECHNOLOGY – Part I 9. TCP/IP ARP Cache • Will have a heavy traffic if so many ARP broadcast messages are generated • Each host will have a cache to store the mappings (from IP to MAC address) that were obtained before IP Address 158.132.148.80 00-60-8C-27-35-9A 158.132.148.28 52 MAC Address 02-60-8C-1A-37-49 • An entry will only be kept in the cache for a limited amount of time (say, 2 minutes)