Computer Networks and Internets Term Presentation

1
Computer Networks and Internets Term
Presentation

• ASLIHAN BÜLBÜL
• 28672442386
• 19.11.2007-23.11.2007

2
Client/Server Architecture

• What are Client and Server?
• Characteristics of Clients and Servers
• Information Flow between Client and Servers
• Communication Paradigm
• The important issues about Client Server
  Communication
• Most Commonly Used Server Types
• Web Server
• E-mail Server
• FTP Server
• IRC Server
• DNS Server
• Telnet/SSH Server
• DHCP (Dynamic Host Configuration Protocol)

3
What are Client and Server?

• What is Client?
• What is Server?

4
Characteristics of Client and Servers

• Client Software
• Local running. (on PC).
• Contact initiator.
• Active contact with one remote server at a time.
• No need of special hardware or sophisticated OS.
• For one session execution.
• Arbitrary application program.

• Server Software
• Not local running.
• Contact expectant.
• Contact from arbitrary clients, but offering a
  single service.
• Need of powerful hardware and sophisticated OS.
• One service, many clients.
• Special-purpose program.

5
Information Flow Between Client and Servers

• Type of Information flow.
• Request-Response Mechanism.
• Server behaviors in Request- Response Mechanism.
• Client behaviors in Request- Response Mechanism.

6
Communication Paradigm

• Establish communication.
• Exchange messages.
• Terminate communication.
• Ex. Video
• http//www.youtube.com/watch?vey9HCvTIO70

7
The important issues about Client Server
Communication

• Client and Server communication protocols.
• Working style of Client and Servers.
• How can a client find server?
• Port Numbers.
• How can servers hardware capacity and internet
  connection speed can be specified?

8
Most Common Server Types

• Web Server
• Publishing web sites.
• Importance of Adjusting connection capacity
• In LANs or ISPs system rooms(colocation).
• Web hosting
• Need of
• 7x24 internet connection
• Real and static IP address
• Domain name
• Port situation (80th TCP port)
• Examples Open Source Apache Server on Linux,
  IIS(Internet Information System) on Windows XP
  OS, Windows 2000.

9
Most Common Server Types-2

• E-Mail Server
• Delivery of e-mail from sender to receivers
  e-mail server.
• Saving e-mails and deliver them when user
  connects.
• E-mail sending operation
• 1.Connecting to the server.
• 2.Sending e-mail.
• 3.Looking receiver addresss domain name by
  server. (xxx_at_ddd.com)
• 4.Delivering the mails according to domain name.
  (if same domain deliver to own POP3 server,
  otherwise ask to the DNS server and learn the IP
  address).
• 5.Send e-mail with STMP(Simple Mail Transfer
  Protocol) to the other server.
• 6.Looking to the user name of this e-mail
  address and accept this e-mail.

10
Most Common Server Types-3

• FTP(File Transfer Protocol) Server
• A program or file transfer from network.
• Download links
• Connecting to FTP
• Web browsers
• Command line of OSs.
• FTP Client Programs (cuteFTP, FlashFXP)
• Updating web sites.
• Remote control of PC.
• User types (anonymous and private) and security.
• Ex for Linux, ProFTP, PureFTP
• for Windows, an FTP Server exists with
  IIS(Internet Information Server)
• Uses TCP 21th port.

11
Most Common Server Types-4

• IRC (Internet Relay Chat) Server
• Communication and chat.
• Basic client server paradigm.
• More than one clients and server at the scene.
• Ex for UNIX/shell ircII
• for WindowsmIRC or PIRCH
• for Macintosh Ircle

12
Most Common Server Types-5

• DNS (Domain Name)Server
• Conversion between domain names and IPs.
• Resource Records (tables).
• Hierarchical communication of DNS servers.
• Cache (temporary database) and TTL (time to
  live).
• Duties of DNS
• Response to Clients
• Response to other DNS servers.
• nslookup command.
• For client requests UDP 53th port.
• For other DNS requests TCP 53th port.
• Mostly used DNS server is BIND (Berkeley Internet
  Domain).

13
Most Common Server Types-6

• Telnet/SSH (Secure Shell) Servers
• Remote connection and using commands. (LAN and
  internet)
• Terminal usage.
• E-mail send/receive, e-chat, news group in the
  past, management and control duties now.
• Difference of SSH from Telnet.
• Text-based servers.

14
DHCP(Dynamic Host Configuration Protocol)

• IP address specification.
• Distributing IP addresses.
• IP address pool.
• Net mask, gateway and DNS server addresses.

15
Most Common Server Types
Web Server Includes the web sites (hosting).
E-Mail Server Includes the e-mail accounts and emails.
FTP Server Programs and files for downloading exist here.
IRC Server Communication and chat.
DNS Server Domain names are converted to IP addresses here.
Telnet/SSH Servers Remote connection and using commands.
16
PORTS

• Definitions and Classification
• TCP (Transport Control Protocol)
• Characteristics of TCP
• UDP (User Datagram Protocol)
• TCP/UDP and Application Programs
• Port Numbers of various application programs
• Packet Loss and Retransmission

17
Definitions and Classification

• What is PORT?
• Why port is needed?
• Entrance points.
• Security.
• Types of ports
• TCP (Transport Control Protocol)
• UDP (User Datagram Protocol)

18
TCP (Transport Control Protocol)
Source Port Destination Port Source Port Destination Port Source Port Destination Port Source Port Destination Port
Sequence Number Sequence Number Sequence Number Sequence Number
Acknowledgement Number Acknowledgement Number Acknowledgement Number
Hlen Rserved Code bits Window
Checksum Urgent Pointer Checksum Urgent Pointer Checksum Urgent Pointer Checksum Urgent Pointer
Options (optional) Padding Options (optional) Padding Options (optional) Padding Options (optional) Padding
Data Data Data Data
. . . .

• Segmentation and TCP
• Secure Communication
• Advantage and disadvantages of security
• Source Port
• Destination Port
• Connection-Oriented
• SYN, SYN/ACK, ACK, FIN
• Acknowledgement information
• Optimum Window Size (536 byte)

19
Characteristics of TCP

• Connection-Orientation
• Point-To-Point Communication
• Complete Reliability
• Full Duplex Communication
• Stream Interface
• Reliable Connection Startup
• Graceful Connection Shutdown

20
UDP (User Datagram Protocol)

• Simpler than TCP
• No handshaking
• Not secure communication
• No acknowledgement information
• Advantages and disadvantages

21
TCP/UDP and Application Programs

• Differences of TCP and UDP
• Where to use TCP or UDP?
• Simultaneous usage of TCP UDP
• Ex. MSN messenger, Skype
• See the open ports
• http//www.youtube.com/watch?vfuZylN8ZV_o

Port Numbers of some network Servers
DNS 53 (UDP)
TFTP 69 (UDP)
SNMP 161 (UDP)
FTP 20 21 (TCP)
Telnet 23 (TCP)
SMTP 25 (TCP)
HTTP 80 (TCP)
POP3 110 (TCP)
22
Packet Loss and Retransmission

• Acknowledgement message (ACK)
• Timer
• Delay
• Retransmission
• Concurrent working of application programs.
• Duplicate packets problem

23
IP (Internet Protocols)

• General Expression about IP
• The explanation of IPv4
• IPv4 address format
• The explanation of IPv6
• IPv6 address format
• Transition Duration to IPv6
• IPV4 vs. IPv6

24
General Expression about IP

• What is IP?
• The Success of IP
• Unique
• Locator
• Identifier
• Handling heterogeneity
• IP datagram
• Compatibility
• Frame sizes and IP

25
IPv4

• IP and IPv4
• 32 bit address
• Solving need of IP
• NAT (Network Address Translation), CIDR
  (Classless Inter-Domain Routing), DHCP
• What will happen in 2010s?
• Deficiencies of IPv4
• Quality of service
• Security
• Compatibility with electronic devices
• IPv4 Routing Protocols

26
IPv4 Address Format

• Four numbers, each ranging from 0 to 255
• Ex. 147.132.42.18
• Classes of networks
• A class (1-126)
• B class (128-191)
• C class (192-223)

27
IPv6

• Why IPv6 is needed?
• Transition from IPv4 to IPv6
• Changes in this transition duration
• Producers and IPv6 (MAC OS, Solaris, Linux,
  WinXP/2003)
• Providing IPv6 support to application programs
• IOS (Interface Operating Systems) Nokia,
  Cisco,3Com
• Ex. video http//www.youtube.com/watch?vqsWNWm2O
  0_Q

28
IPv6 Address Format

• 8 Pieces, 32 x hexadecimal numbers
• 324128 bits.
• Ex 3FFE0B00000000000000000000000046
• 00000000000000000000000000000000
• Same with ? 00000000 or
• 201002340000000000670000000000E2
• Same with ? 20102340067E2
• 40A1000016FE000000000C2386E1
• Same with ? 40A1016FE00C2386E1
• Or
• 40A1016FEC2386E1
• Only once usage of

29
Transition Duration to IPv6

• Changes in Client-Server Software
• Cost of change
• Updating
• Client programs,
• OSs,
• Hardware
• Network Connection device software updates.

30
IPv4 vs. IPv6
Ex. video http//www.youtube.com/watch?v-ZW8v0zd
6C0
IPv4 IPV6
32 bit address 128 bit address
Uses base 10 Uses base 16
No abbreviation Allow abbreviation
4 x 8 bits 8 x 16 bits
Pieces are separated with . Pieces are separated with
127.0.0.1 is loopback address 00000001 or 1 is loopback address
31
Sources

• BOOKS
• Bilgisayar Aglari ve Güvenligi Alper ÖZBILEN
  (Pusula Yayincilik)
• IPv6 clearly explained- Pete LOSHIN
• Internetworking with TCP/IP volIII Client Server
  Programming and Applications
• INTERNET Sources
• http//en.wikipedia.org/wiki/IP_address
• www.youtube.com (videos)

32
Thank you for listening.

• Questions