Data Communication I

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Urban Bilstrup (E327)

090901

[email protected]

www2.hh.se/staff/urban

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Internet - Sweden, Northern Europe

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Internet - Internet Addresses



Everyone should be

able to address

everyone!



IP-addresses.



Everyone should be

able to understand

everyone!



Internet Protocol.



RFC* 791

Internet

coriolis

194.47.1.137

home-v4

207.200.89.226 (home-v4.websys.aol.com)

fibbla

129.16.20.156 (fibbla.ce.chalmers.se)

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Internet – Adress Space

IP uses a 32 bits address field, four octets. These four octets are presented as four decimal numbers 0-255. The four octets are divide into a network part and host part. (194.47.1.137)

0 7 7 0 7 _{0 7} 0 Class A 0 Net-ID 0 7 7 0 7 _{0 7} 0 Class B 1 0 Net-ID

Host-ID 16M hosts each

Host-ID 65536 host each

0

7 7 0 7 _{0 7} 0

Class C 1 1 Net-ID Host-ID 256 hosts each

0

7 7 0 7 _{0 7} 0

Class D 1 0 Multicast address

0

1 1

0

7 7 0 7 _{0 7} 0

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Internet

coriolis% traceroute 129.16.20.156

traceroute to 129.16.20.156 (129.16.20.156), 30 hops max, 40 byte packets 1 cat5500-1.net.hh.se (194.47.1.1) 1.069 ms 0.696 ms 0.623 ms 2 halmstad-1-FE1-0-0.sunet.se (130.242.201.145) 1.620 ms 0.525 ms 0.418 ms 3 MLM-BB-1-POS1-2.sunet.se (130.242.210.26) 2.027 ms 2.179 ms 2.231 ms 4 STK-BB-1-POS10-0.sunet.se (130.242.204.241) 9.457 ms 9.833 ms 10.823 ms 5 GBG-BB-1-POS4-0.sunet.se (130.242.204.234) 18.576 ms 17.736 ms 18.048 ms 6 chalmers-1-POS4-0-0.sunet.se (130.242.200.110) 18.450 ms 17.907 ms 18.211 ms 7 cth1-gw.sunet.se (130.242.202.86) 120.884 ms 180.229 ms 106.058 ms 8 ed-ge-gw.chalmers.se (129.16.2.102) 19.229 ms 19.085 ms 19.005 ms 9 fibbla.ce.chalmers.se (129.16.20.156) 19.286 ms 19.209 ms 19.479 ms

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Internet - Internet Protocol Stack

Application Presentation Session Transport Network Datalink Physical Application TCP UDP IP Device Driver and Hardware

Application processes

Operative system

sockets

OSI referens

modell

Internet

protokollets

modell

•Open Systems Interconnection (OSI). •International Standard Organization (ISO). •Sockets => a

interface between the application and the operative system. •Sockets => a file handle that is used for network

communications, it can also be used for inter-process

communications in a local host.

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Internet – Port Numbers



Internet Assigned Numbers Authority (IANA)



Well known port numbers 0-1023



Registered port numbers 1024-49151



Dynamic or private port numbers 49152 -65535

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ftp-data 20/tcp File Transfer [Default Data] ftp-data 20/udp File Transfer [Default Data] ftp 21/tcp File Transfer [Control]

ftp 21/udp File Transfer [Control]

telnet 23/tcp Telnet telnet 23/udp Telnet

smtp 25/tcp Simple Mail Transfer smtp 25/udp Simple Mail Transfer

domain 53/tcp Domain Name Server domain 53/udp Domain Name Server

http 80/tcp World Wide Web HTTP http 80/udp World Wide Web HTTP

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Internet



As long as the information is put into a IP packet the network gets the

information that is needed for the packet to find the path from a one

computer to another computer.



Problem can appear if only IP-protocol is used!!!!!



Most data transmissions include more data then can be fit into one IP

packet (1500 characters).



Sometimes it goes wrong and the network lose a packet.

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Internet - Transport protocol



User Datagram Protocol (UDP)

• Non connected

• Do not guarantee packet delivery

• Do not guarantee the right packet sequence

delivery.

• RFC 768



Transmission Control Protocol (TCP)

• Connected.

• Guarantee a packets delivery.

• Guarantee the right packet sequence delivery.

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Internet - UDP



UDP transmission

between ”coriolis”

and the server

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Internet - TCP



TCP transmission

between the client

”coriolis” and the

webbserver ”fibbla”

at Chalmers.

129.16.20.156 fibbla.ce.chalmers.se 194.47.1.137 coriolis.hh.se SYN j SYN j+1, ACK k ACK k+1 DATA request DATA response and ACK of the

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Internet Domain Name Server (DNS)



A distributed mapping system between host names and IP

(for example fibbla.ce.chalmers.se => ???).



DNS is implemented as hierarchical database.

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Application Protocol



File Transfer Protocol (FTP), rfc 959.



Hyper Text Transfer Protocol (HTTP), rfc 1945 och

rfc 2068.



Simple Mail Transfer Protocol (SMTP), rfc 821.



Network News Transport Protocol (NNTP), rfc 977.

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HTTP overall function



Stateless protocol



The client opens a TCP connection and sends a

request to a server and the server answers with the

requested data and than the connection is closed.



Uniform Resource Locator (URL)

coriolis.hh.se Web browser Network _Web server förfrågan svar

Http://www.hh.se:80/index.html

Protokoll _{Host namn}

Port nummer

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HTTP Applikations Protokollet



HTTP command (method).



A number of methods; GET, HEAD, POST, PUT,

OPTIONS, DELETE, TRACE.



The most usual is GET (Client request).

GET /index.html HTTP/1.0 Method Request URI Protocol

For example:

First comes a header that tells the configuration of the client. Keyword: Value

For example:

User-Agent: Mozilla/4.0

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HTTP Applikations Protokollet



Server response.

Protocol Status-code Description For example:

HTTP/1.0 200 OK [CRLF]

Then some header-information and requested data:

Keyword: Value

Date: Wed, 1 Jan 2001 15:30:24 GMT [CRLF] Server: Apache/1.3.6 (Unix)[CRLF]

Last-Modified: Mon, 17 May 1999 15:46:21 GMT [CRLF] Accept-Range: bytes [CRLF]

Content-Length: 10352 [CRLF] Connection: Close [CRLF]

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HTTP Application Protocol

The body of the HTML document: