??sa???? sta d??t??

1
??sa???? sta d??t??
2
?e??e??µe?a

• ???t?a ?p?????st?? Internet
• OSI Internet layer models
• ?a p??t?????a TCP/IP
• IP addressing
• DNS, URLs
• HTTP
• HTML
• Troubleshooting

3
???sµ?? e??? d??t???

• ?e t?? ???????a d??t?? e?????µe t?? s??des?
  ?p?????st?? µeta?? t??? µe ??p??? µ?s?, e?te a?t?
  e??a? apt? (?a??d??), ? ??? (a??a?).
• ?? ????? ??a t?? d?µ??????a d??t??? e??a? ??
  e???
• ????asµ???? p???? (e?t?p?t??, d??t?a??? d?s???).
• ??????µ?a st? s??des? µe t? Internet (p?????
  ?p?????st?? µe µ?a s??des?).
• G?????? a?ta??a?? a??e??? ????? t? ???s?
  a?a??s?µ?? (d?s?ett??, CD, DVD).

4
???t?a ?p?????st?? Internet

• ? d?as??des? p????? ?/? ap?te?e? ??a ???t?? ?/?
• ? d?as??des? d??t??? ???µ?st??e d?ad??t??

??a ? pe??ss?te?a ap? ta ep?µ????? d??t?a e???
d?ad??t??? s????e? t? ß???? t?? d?as??des?? t??
d??t??? ?a? ???µ??eta? ?a??????a??? (backbone)
5
WWW Internet

• Web ? Internet
• Internet ??a f?s??? d??t?? p?? e???e?
  e?at?µµ???a ?p?????st?? p?? ???s?µ?p????? ta ?d?a
  p??t?????a ??a d?aµ???as? ?a? µet?d?s?
  p????f???a? (TCP/IP)
• ??a d??t?? ap? µ????te?a d??t?a
• World Wide Web µ?a s?????? ap? d?as??dedeµ??a
  p???µes??? ????afa p?? e??a? ap????e?µ??a st?
  Internet µp??e? ?a?e?? ?a ta p??spe??se?
  ???s?µ?p????ta? ??a ????? p??t?????? (HTTP)
• To Internet e??a? hardware e?? t? Web e??a?
  software
• ?p?????? p????? ???e? efa?µ???? p?? st??????ta?
  st? Internet
• email, ftp, telnet, chat, news, ?.?p.

6
Internet, Intranet Extranet

• Intranet µ?a pa??µ??a ??????s? ap? d??t?a p??
  ???s?µ?p????? t? s???ta p??t??????? TCP/IP ?a?
  efa?µ???? p?? ßas????ta? st? Internet a??? µ?sa
  st? pe??ß????? e??? ???a??sµ?? ? µ?a? ep??e???s??
  
• Extranet e??a? ? µe??da/d?aµ???as? t?? d??t???
  Internet e??? ???a??sµ?? ? µ?a? ep??e???s?? µe
  t?? ??? ??sµ?, p.?. E- commerce

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Internet forces

• ?? Internet ?a??d??e?ta? ap?
• WWW (t? e??a?e??)
• Hypertext (??a f????? st? ???st? µ?s? p?????s??
  t?? pe??e??µ????)
• ?? 2 p??t?se?? p?? ?d???sa? st?? a??pt??? t??
• Hypertext Transfer Protocol (HTTP) (p??s?ese t?
  p?a?s?? µ?sa st? ?p??? ??a? HTTP client (web
  browser) µp????se ?a p??e? p????f???e? s?et??? µe
  ta ded?µ??a p?? f??t??e (download)
• Hypertext Markup Language (HTML) (pa?e??e µ?a
  d???e?t? µe t? d??at?t?ta ?pes??d?sµ??
  (hyperlinks) µ?sa se ??a ????af?)

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Hypertext
9
?st???a t?? Internet

• sta t??? 40 e?e???t?? ap? ??? (Lincoln lab)
  RAND ? Semi-Automated Ground Environment ? a???
  t?? ?d?a? d?as??des?? ?p?????st??
• 1958 d?µ?????e?ta? t? ARPA (Advanced Research
  Projects Agency) (DoD) st?at??t??? te???????a
  d?ast?µat??
• 1962 Licklider ap? t? MIT (Bush, Turing)?
  interactive computing, d?as??des? ?p?????st?? p??
  ß??s???ta? se µe???e? ap?st?se??
• 1966 ?????s? ??a t? p??t? ARPA d??t?? (ARPANET)
  ??a d?aµ???as? p???? (56Kb/sec) - UCLA, UCSB, SRI
  Utah

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1957 ? Sputnik e?t??e?e? t?? ARPA

• ? S?ß?et??? ???s? ß??e? se t????? t?? Sputnik,
  t?? p??t? te???t? d???f???. ??t? ? t?s? s?µa?t???
  te????????? e?????? se µ?a ep??? ??t????
  a?ta????sµ?? t?? d?? ?pe?d???µe??, e?e???p??e?
  t?? ?µe???????? ??ß????s? ?a? ?d??e? t?? ARPA
  (Advanced Research Projects Agency). ?e s??p? t??
  p?????s? t?? ??e??a? t?? ?????? te???????a? ?a?
  t?? efa?µ???? t?? ??a st?at??t????? s??p???.

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1960 - Ted H. Nelson "hypertext" ?a? "hypermedia"

• ? Ted H. Nelson e??a? ? efe???t?? t?? hypertext.
  ? Nelson ???se t? hypertext sa? ??a e??a???
  s????? ?e?µ???? ? e?????? es?te???? s??dedeµ????
  µe t?s? pe??p???? t??p? p?? de? ?a ?ta? e????? ?
  a?apa??stas? t??? se ?a?t?. ?? hypertext ??e? t??
  d??at?t?ta ?a s??d?e? p????f???e? µ?s? s??d?se??
  se ??a s?µpa??? ?a? e??a?? s?µa.

Ted H. Nelson
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1961 Te???a µeta????? pa??t?? Packet-Switching

• ?? p??t? ????? p??? st? ?e???a µeta????? pa??t??
  (packet-switching) apt?? Leonard Kleinrock, st?
  MIT.

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1964 ??a d??t?? ??a?? ?a a?t??e? µ?a p???????
ß?µßa

• ?? 1964, ? RAND Corporation s?ed?ase ??a d??t??
  ep?????????? p?? ?a µp????se ?a e??se? p??e??,
  p???te?e? ?a? st?at??t???? ß?se?? ?a? ?a µp??e?
  ?a ?e?t?????se? a??µa ?a? se pe??pt?s? p????????
  ape????. ? Paul Baran t?? RAND st?? p??tas? t??
  µe t?t?? "On Distributed Communication Networks."
  p??te??e? ??a d??t?? ????? ?e?t???? ??e??? ?a? µe
  a?t???µ??? ??µß???.

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1969 ?? ARPANET ?e?t????e? µe 4 ??µß???

• ? p??t?? ??µß?? (host) s??d????e µe t? ARPANET
  (Network Measurement Center st? UCLA). ????? t?
  t???? t?? 1969, t?sse??? ??µß?? ?ta? s??dedeµ????
  µe t? ARPANET.

UCLA - Univ. of Calif. at Los Angeles UCSB -
Univ. of Calif. at Santa Barbara UTAH - Utah
University SRI - Stanford Research Institute
15
1971 E-Mail

• ? Ray Tomlinson efe???s?e? ??a p????aµµa email
  ?ste ?a st???e? µ???µata µ?s? d??t???. ?p?s?? t?
  1971, t? ARPANET ??e? µe?a??se? se 15 ??µß??? µe
  23 hosts.

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1973 - Ethernet

• ?e????se ? a??pt??? t?? p??t??????? p?? a???te?a
  ?a ???µaste? TCP/IP ap? t?? ?µ?da t?? Vinton Cerf
  ap? t? Stanford ?a? t?? Bob Metcalfe.

Bob Metcalfe ??µ??????? t?? Ethernet

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1975 - The First Mailing List Is Started

• ???t? ???s? t?? ????? internet ap? t??? Vinton
  Cerf ?a? Bob Kahn se ??a ????af? ??a t?
  p??t?????? e?????? µet?d?s?? (TCP).

Vinton G. Cerf?at??a? t?? Internet"
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1979 - ?a BITNET ?a? USENET d?µ?????????a?

• ? Steve Bellovin f??t?t?? st? pa?ep?st?µ?? t??
  ß??e?a? ?a?????a?, µa?? ?a? t??? p????aµµat?st??
  Tom Truscott ?a? Jim Ellis d?µ???????? t? USENET.
  H IBM d?µ?????e? t? BITNET.

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1983 - Internet

• ?? ARPANET ?a? ta ???t?a ?µ??a?(Defence Data
  Networks) a??????? ?a ???s?µ?p????? p??t??????
  TCP/IP ?? Internet ?e????ta? t?? 1? ?a???a????
  1983. ?? ARPANET ?????eta? st? ARPANET ?a? t?
  MILNET, t? te?e?ta?? e???eta? µe t? ???t?? ?µ??a?
  (Defence Data Network).

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1984 - 1991

• 1984 1,000 ??µß?? s??dedeµ???? st? Internet.
  ?at? t? d????e?a t?? ?d??? ?????? a?apt?????e t?
  voice mail (ta??d??µe?? f????).
• 1989 100,000 ??µß?? st? Internet. ??aµ??f??eta?
  t? d??t?? t?? S?µate??? ??a t?? d??t??s? t??
  ??e??a? ?a? t?? ??pa?de?s?? (CREN) .
• 1991 Gopher burrows into the Internet . The
  National Science Foundation (NSF) lifts the ban
  on commerce on the Internet.
• 1991 ? Gopher eµfa???eta? st? Internet . ??
  ?d??µa ??????? ??e???? (NSF) a??e? t?? apa???e?s?
  t?? eµp????? st? Internet.

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1992 ? Tim Berners-Lee d?µ?????e? t? WWW

• 1,000,000 ??µß?? st? Internet. ?? World Wide Web
  (WWW) a?apt?sseta? apt?? Tim-Berners Lee, ?
  ?p???? d???e?e st?? t?µ?a t?? ?p?????st?? st?
  CERN.

Tim Berners-Lee
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1993 ? p??t?? browser

• ? MOSAIC browser a?apt?????e ?????? apt?? Marc
  Andreesen. ?? WEB µe?a???e? ?at? 341.000

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1994

• Pizza Hut
• ???t? ? Pizza Hut p??sf??e? t?? d??at?t?ta
  pa?a??e??a? p?tsa? online t?? ?????st? t?? 1994.
• Yahoo
• ?? Yahoo, e??a? ? p??t? µ??a?? a?a??t?s?? ?a?
  d?µ?????????e t?? ?p????? t?? 1994 ap? t?? David
  Filo ?a? t?? Jerry Yang st? pa?ep?st?µ?? t??
  Stanford. S?µe?a t? Yahoo pa???e? 167 e?at?µµ???a
  a?a??t?se?? t?? µ??a.

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1995

• Domain Fee??1995, ?a??e???eta? et?s?a s??d??µ?
  50 sta domains, e?t?? ap? ta .edu ?a? .gov.
• Netscape? Marc Andreessen, ? e???fa??? p?s? ap?
  t? Mosaic, ?d??e? t?? eta??e?a Mosaic
  Communications Corporation p?? e??a? ???st? sa?
  Netscape.
• Amazon?? Amazon, a????e? st? Seattle ap? t??
  Jeffrey Bezos.

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1996

• Internet Explorer
• H Microsoft pa???s???e? t?? p??t? ??d?s? t??
  Internet Explorer
• Java
• To 1996 ??a?e t?? eµf???s? t?? ?a? ? ???ssa
  p????aµµat?sµ?? ? Java t?? Sun Microsystems.
• Flash
• ?? 1996, ? FutureWave Software p???????e st??
  Macromedia, ?a? t? FutureSplash Animator ????e t?
  Macromedia Flash 1.0.

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1997

• Winamp? Winamp, e??a? ? p??t?? MP3 music player.
• business.com?? domain name business.com, t?
  ?p??? e??e ?ata?????e? ??a 50 t? 1995, p??e?te
  ??a 150,000 t? 1997. ?? 1999 ??st??e?
  7,500,000.
• Blog? ???? "weblog" ???e? t?? eµf???s? t?? t? 97
  ap? t?? Jorn Barger . ???????e? ? ????, "blog,"
  ap? t?? Peter Merholz t? 1999.

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1998

• PayPal
• ?? PayPal, ?d?????e t?1998 ap? t?? Peter Thiel
  ?a? Max Levchin. ?? Paypal ??????a ????e ? p??
  d?aded?µ???? t??p?? p????µ?? st? d?ad??t?? ?a?
  e?d??? st? eBay.
• Google
• ? Larry Page ?a? Sergey Brin, ?fe?a? t? Google
  st?? ??? t? 1998 µe pe??p?? 10,000 e??t?µata t??
  µ??a. ?? 1999 e??e 500,000 e??t?µata t?? ?µ??a,
  ?a? e?? t? 2000 100 e?at?µ???a t?? ?µ??a. S?µe?a
  t? Google ??e? ?ata????af?se? 4.28 d?se?at?µ???a
  web pages ?a? pa???e? 250 e?at?µ???a search
  results t?? ?µ??a.

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2006 - Web 2.0

• Web 2.0

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???pt??? t?? Internet

• t? de?aet?a t?? 80 ? a???µ?? t?? ?/? st?
  d?ad??t?? a?apt?????e e??et???

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???pt??? t?? Internet

• ? ????? t?? Internet traffic ??p???? ??µ?? t??
  Moore ? (Larry Roberts, 2003)

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???pt??? t?? Internet
32
??? d???e?e?

• ??a ???a?t?a?? client-server s?st?µa
• ? Web server ap????e?e? Web pages ?a? ?e?t????e?
  ?? µes?t??
• ?? Web Browsers e??a? ?? pe??te? p?? a?t???ta?
  se??de? ap? t?? ?at?????? server ?a? t??
  pa???s?????? µe t?? ?at?????? µ??f?
• p.?. ?ta? ???f??µe ??a URL ? ?????µe ???? se ??a
  s??desµ? µ?a? se??da?
• ? a?t?s? p??a??e? st?? Web server p?? ??e? t?
  se??da
• ? server ap?st???e? t? pe??e??µe?? t?? se??da?
  st?? ?p?????st? pe??t?
• ? Browser d?e?µ??e?e? t?? ??d??a HTML ?a?
  pa???s???e? t? ?e?µe??/t?? e????e?/?.?p.
• ?? HyperText Transfer Protocol (HTTP) ?a?????e?
  t? µ??f? t?? µ???µ?t?? p?? a?ta???ss??? ? browser
  ? Web server
• ? HyperText Markup Language (HTML) ?a?????e? t?
  pe??e??µe?? t?? e????f?? ???s?µ?p????ta?
  et???tte? tags

HTTP ??t?s?
???p??et?t?? WWW (server)
?e??t?? WWW (client)
?p?st??? ??????
33
????te?t????? ???t???
?p?????st?? - ?
?p?????st?? - ?
?????? ?p????????a
??a?µat??? ?p????????a
F?s??? µ?s?
34
??? ???eta? ? ep????????a
F?s??? µ?s? µet?d?s??
35
OSI Internet model

• OSI - Open Systems Interconnect - Reference
  Model
• Physical af??? t? f?s??? µ?s? µetaf???? p.?.
  serial parallel cables, Ethernet Token Ring
  cabling, telephone wiring, ?.?p.
• Data Link ?a?????e? t? p?? ? p????f???a
  µetad?deta? st? f?s??? ep?ped? e??a? ?pe?????
  ??a t?? ???? µet?d?s? ??e??? t?? f?s???? µ?s??
• Network p??sd?????e? t?? d?e????se?? t??
  s?st?µ?t?? st? d??t?? f???t??e? ??a t??
  p?a?µat??? µet?d?s? t?? ded?µ????. ???a? e??µe??
  ??a t? f?s??? µ?s? pa?et??e? t?? p????f???a µe
  t?t??? t??p? ?ste ?a µp??e? ?a µetad??e? ap? t?
  f?s??? µ?s?. Se p???? d??t?a t? ep?ped? a?t? de?
  pa???e? ??e??? ??a t? a? µetaf?????e s?st? ?
  p????f???a, p.?. t??e??as?, ??d??.
• Transport pa???e? t?? ?p??es?e? ??a t?? ??e???
  a???p?st?a? p?? de? pa???e? t? p??????µe??
  ep?ped?. ?as??? e?asfa???e? ?t? t? Network layer
  ?e?t????e? ap?d?t??? d?af??et??? apa?te?
  a?aµet?d?s? t?? ded?µ????.
• Session f???t??e? ?a d?µ?????e? s??d?se?? µeta??
  s?st?µ?t??, efa?µ???? ? ???st?? ?ste?a ap?
  a?t?se?? p?? ?aµß??e? ap? ta a??te?a st??µata
• Presentation pa???e? ??a s??ep?? interface p??
  ???s?µ?p????? ?? d??f??e? efa?µ???? ?p??es?e?
  ?ta? d?µ?????e?ta? µ?a s??des?, p.?.
  data-compression
• Application e??a? t? interface t?? d??t??? sta
  p??t?????a efa?µ???? te????? ???st?, ?p?? e??a?
  ta HTTP POP3.

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OSI Internet model

• Internet Model (TCP/IP)
• Application protocols
• HTTP (Hyper-Text Transfer Protocol)
  ???s?µ?p??e?ta? ap? t??? Web browsers µeta??
  ????? ??a ?a p??spe??s??? ded?µ??a ap????e?µ??a
  se Web servers
• SMTP (Simple Message Transfer Protocol)
  ???s?µ?p??e?ta? ap? t? e-mail, ?.?p.
• Transport Layer - TCP UDP t? TCP pa???e? µ?a
  ????? pa?a????????µe?? a???p?st? ?p??es?a
  µetaf????, e?? t? UDP pa???e? µ?a ap?? ?p??es?a
  µetaf???? ????? ??e??? a???p?st?a?. ?a? ta d??
  pa?????? ?p??es?e? t?? session layer d??ad?
  d?a?e??????ta? ??e? t?? s??d?se?? µeta?? t??
  d?af??et???? ?/?.
• Network Layer - IP a????e?e? t?? d?e????se?? t??
  s?s?e??? st? d??t?? p??sd?????e? p?? ?a
  pa?ad????? ta ded?µ??a (IP datagrams ? packets)
  ap? t?? ??a? ?/? st?? ????. G?a ?a ???e? a?t?
  ???e ?/? p??pe? ?a ??e? µ?a d?e????s? (IP
  address)

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TCP/IP Headers

• IP protocol ? p??s??te? packet routing info ????
  sta 20 bytes
• TCP protocol ? p??s??te? p????f???a ??a ?a
  d?µ???????e? ??a virtual circuit.
• pe???aµß??e? ep?s?? message formatting, circuit
  management, flow control, error correction.

38
?? t?p?????e? s?ed?ast???
39
Routers - Firewall

• Router (gateway)
• ????e?e? st? ep?ped? t?? ???t???
• ????e? ?p?d??t?a
• ???spa?e? ?a ste??e? ta pa??ta ap? t?? ?a??te??
  d?ad??µ?

• Firewall
• ?? te???? p??stas?a? e??a? ????sµ??? ? ????? p??
  d?µ?????e? ??a? p??state?t??? µ??a??sµ? µeta??
  t?? ?p?????st? sa? ? t?? d??t??? sa? ?a? p??a???
  ep?ß?aß??? pe??e??µ???? t?? Internet.

40
Routing Protocols

• Routers (? Gateways) e??a? µ??a??? e?d???? s??p??
  st? Internet p?? p??sd???????? t? d?ad??µ? t??
  pa??t?? ap? t?? p??? st?? p?????sµ?
• ?ta? ??a? router ?aµß??e? ??a pa??t?, e????e? t?
  d?e????s? p?????sµ??
• e????e? t? d?e????s? µ?sa ap? ??a routing table
• µe ß?s? ta pe??e??µe?a t?? routing table, p????e?
  ta pa??ta se ??a? ???? router (? st?? te????
  p?????sµ? a? e??a? d??at??)
• Routing Information Protocol (RIP)
• pe?????fe? p?? ?? routers a?ta???ss??? routing
  table information
• Open Shortest Path First Protocol (OSPF)
• pe??ss?te?? robust ???µa??t? protocol ap? t?
  RIP
• de? a?ta???sse? ?????????? routing tables,
  e??µe???e? µ??? t??? a??a?µ????? s??d?sµ???
• Internet Control Message Protocol (ICMP)
• s?µp????µa t?? IP, e?d?p??e? t?? ap?st???a (?
  ????? router) ??a a??µa?e? s?????e?, p.?.
  unreachable host, s?µf???s? d??t???

41
IP Address

• ???e s?s?e?? p?? ???s?µ?p??e? t? p??t??????
  TCP/IP ??e???eta? µ?a IP address
• ?/? (Host) µ?a µ??ad??? IP address ??a ???e
  ???ta d??t???
• Routers se ???e p??ta ? s??des?
• Printers
• ???e? s?s?e???
• ? IP Address p??pe? ?a e??a? µ??ad???
• ??a pa??de??µa
• 147.102.1.1
• ? d?aµ??f?s? ???eta? µe t? ????sµ??? TCP/IP

42
IP Address ?? e??a?

• 32-bit d?ad???? a???µ?? (address)
• 11000000101010000111000100010011
• ??a??e?ta? se 4 ??t?de? (8-bit)
• 11000000.10101000.01110001.00010011
• ?etat??peta? se ??a? a???µ? µe te?e?e?
• 192.168.113.19
• ?? e???? ???e ??t?da? e??a? 0-255
• ? d?e????s? IP p??sd?????e? ??a ???e s?s?e??
• t? d??t?? (Network ID) st? ?p??? ß??s?eta? ?a?
• t?? ?d?a t?? s?s?e?? - ?/? st? d??t?? (Host ID)

43
IPv4

• ???? 32-bits
• ?epe?asµ???? a???µ?? IP d?e????se??
• S??e??? µe?a??te??? p??a?e? d??µ?????s??
• ?e? pa???e? p???t??? e??p???t?s? se efa?µ???? p??
  t? apa?t???
• ?e? pa???e? ????? ep?peda asf??e?a?

44
IPv6

• 128-bits (296 ep?p???? d?e????se??)
• ??????? epe?e??as?a ep??efa??d??
• µ??a??sµ??? asf??e?a? ?a? p?st?p???s??
• ?? d?e????se?? a?at??e?ta? se interfaces (??? se
  ??µß??? t?? d??t??? ?p?? ????ta? µe t? IPv4)

45
Network ID Host ID
Network ID e??a? ?????? ?a? d?aµ?????eta? se ????? t??? ?p?????st?? t?? d??t??? (?d?? segment) ???ad???? se ???????? t? d??t?? Area code Host ID p??sd?????e? µ?a s???e???µ??? s?s?e?? µ?sa st? d??t?? (segment) ???ad???? st? s???e???µ??? d??t?? (segment) Phone Number

• 192.168.0.13

46
Network Segments
47
?P Addresses - Classes

• ?? ???se?? t?? IP d?e????se?? ?a???????? p??e?
  ??t?de? (ap? t?? 4) af????? t? Network ID p??e?
  t? Host ID
• Class A - N.H.H.H
• 1? ??t?da ap? 1 - 127
• Class B - N.N.H.H
• 1? ??t?da ap? 128 - 191
• Class C - N.N.N.H
• 1? ??t?da ap? 192 - 223
• Class D ?
• Class D (1110) ??a multicasting
  (single message sending to a
  subset of the network)
• Class E (11110) pe??aµat????

48
?P Addresses Class A

• ?p??ad?p?te address a????e? µe 0 st? p??t? bit
  t?? 1?? ??t?da?
• 00000001.00000000.00000000.00000000 (1.0.0.0)
• 01111111.00000000.00000000.00000000 (127.0.0.0)
• H 1? ??t?da af??? t? Network ID ?? ???e? t?
  Host ID
• 0.0.0.0 (?????)
• 1.0.0.0
• 2.0.0.0
• 127.0.0.0 (Loop Back Address)
• 126 p??a?? Network IDs ?a? 25625625616.772.216
  Host IDs
• ???ta afa????µe 2 ap? t?? s??????? a???µ? t??
  Hosts
• St?? d?e????se?? Host IDs de µp????µe ?a ????µe 1
  se ??a ta bits (desµe?µ??? d?e????s? broadcast
  address (µ???µa p??? ????? t??? hosts t??
  d??t???))
• St?? d?e????se?? Host IDs de µp????µe ?a ????µe 0
  se ??a ta bits (desµe?µ??? d?e????s? This
  network only)

49
?P Addresses Class B

• ?p??ad?p?te address a????e? µe 10 sta p??ta 2
  bits t?? 1?? ??t?da?
• 10000000.00000000.00000000.00000000 (128.0.0.0)
• 10111111.11111111.00000000.00000000
  (191.255.0.0)
• 1? 2? ??t?da af??? t? Network ID ?? ???e? t?
  Host ID
• 128.0.0.0
• 128.1.0.0
• 128.255.0.0
• 129.0.0.0
• 129.1.0.0
• 191.255.0.0
• 128 ??? 191 64256 16.384 p??a?? Network IDs
  ?a? 256256 (-2) Host IDs
• ???ta afa????µe 2 ap? t?? s??????? a???µ? t??
  Hosts
• St?? d?e????se?? Host IDs de µp????µe ?a ????µe 1
  se ??a ta bits (desµe?µ??? d?e????s? broadcast
  address (µ???µa p??? ????? t??? hosts t??
  d??t???))
• St?? d?e????se?? Host IDs de µp????µe ?a ????µe 0
  se ??a ta bits (desµe?µ??? d?e????s? This
  network only)

50
?P Addresses Class C

• ?p??ad?p?te address a????e? µe 110 sta p??ta 3
  bits t?? 1?? ??t?da?
• 11000000.00000000.00000000.00000000 (192.0.0.0)
• 11011111.11111111.11111111.00000000
  (223.255.255.0)
• 1? - 2? - 3? ??t?da af??? t? Network ID ?
  te?e?ta?a t? Host ID
• 192.0.0.0 192.0.255.0
• 192.1.0.0 192.1.255.0
• 192.255.0.0 192.255.255.0
• 193.0.0.0 193.255.255.0
• 223.0.0.0 223.255.255.0
• 192223312562562.097.152 p??a?? Network IDs
  ?a? 256 (-2) Host IDs
• ???ta afa????µe 2 ap? t?? s??????? a???µ? t??
  Hosts
• St?? d?e????se?? Host IDs de µp????µe ?a ????µe 1
  se ??a ta bits (desµe?µ??? d?e????s? broadcast
  address (µ???µa p??? ????? t??? hosts t??
  d??t???))
• St?? d?e????se?? Host IDs de µp????µe ?a ????µe 0
  se ??a ta bits (desµe?µ??? d?e????s? This
  network only)

51
Special ?P Addresses

• St?? d?e????se?? Host IDs de µp????µe ?a ????µe 1
  se ??a ta bits
• Broadcast Address (µ???µa p?? st???eta? p???
  ????? t??? hosts t?? d??t???)
• t? ?d?? ?a? ??a t?? 255.255.255.255
• St?? d?e????se?? Host IDs de µp????µe ?a ????µe 0
  se ??a ta bits
• This network only
• ?? d?e????se?? p?? a??????? µe t? 127
• Loopback Addresses (t?? ???s?µ?p??e? t? TCP/IP
  software ??a t?? ea?t? t?? ?? s?µe?? e??????,
  s?????? ???s?µ?p??e?ta? ? 127.0.0.1)
• ?? d?e????se?? ??a Private Networks
  (p??state??µe?e? d?e????se??)
• 10.0.0.0 10.255.255.255
• 172.16.0.0 172.31.255.255
• 192.168.0.0 192.168.255.255

52
?P Addressing Rules

• ???e s?s?e?? ??e???eta? µ?a µ??ad??? IP Address
• ??e? ?? s?s?e??? st? ?d?? tµ?µa d??t??? (Network
  Segment) µ???????ta? t? ?d?? Network ID (Subnet
  Mask)
• ???e tµ?µa d??t??? (Network Segment) ??e? ??a
  µ??ad??? Network ID (Subnet Mask)

IP address 192.168.0.13 Subnet Mask
255.255.255.0
53
Subnets Subnet Masks
54
Subnets Subnet Masks

• ???µ?????s? pa??t?? µ?sa se ??a d??t?? µe
  ?p?d??t?a

55
?a?ade??µata µe subnet masks

• ?a? ????? d?se? t?? IP 201.222.5.0. ??
  ?p???s??µe ?t? ?????µe 20 subnets µe 5 hosts st?
  ?a???a. ?? subnet mask p??pe? ?a
  ???s?µ?p???s??µe?
• 201.222.5.0.
• 11001001.11011110.00000101.00000000

56
?a?ade??µata µe subnet masks
Required Number of Physical Segments 20  
Maximum Number of Hosts/Physical Segment 5  
Network Address 201.222.5.0.  
     
Proposed Custom Subnet Mask 255.255.255.248  
Number of Subnets Supported 32  
Maximum Number of Host ID per Subnet 6
Subnet IDs 210.222.5.0 210.222.5.8 210.222.5.16 210.222.5.24 210.222.5.248  
  1st Host Last Host on Subnet
Host ID Ranges per Subnet 210.222.5.0 210.222.5.8 210.222.5.16 210.222.5.24 210.222.5.248 210.222.5.1 210.222.5.6 210.222.5.8 210.222.5.14 210.222.5.16 210.222.5.22 210.222.5. 24 210.222.5..30 210.222.5.249 210.222.5.254
57
?a?ade??µata µe subnet masks
Required Number of Physical Segments 250  
Maximum Number of Hosts/Physical Segment 100  
Network Address 191.254.0.0  
     
Proposed Custom Subnet Mask 255.255.255.0  
Number of Subnets Supported 254  
Maximum Number of Host ID per Subnet 254  
Subnet IDs 191.254.1.0 191.254.2.0 191.254.3.0 191.254.4.0 191.254.254.0  
    1st Host Last Host on Subnet
Host ID Ranges per Subnet 191.254.1.0 191.254.2.0 191.254.3.0 191.254.4.0 191.254.254.0 191.254.1.1 191.254.1.254 191.254.2.1 191.254.2.254 191.254.3.1 191.254.3.254 191.254.4.1 191.254.4.254 191.254.254.1 191.254.254.254
58
?P Addressing - Default Gateway

• apa?a?t?t? ??a ?a ????µe ap?µa???sµ??? p??sßas?
• e??a? ? d?e????s? t?? router p?? ß??s?eta? st?
  tµ?µa d??t??? (Network Segment) µe t??
  s???e???µ??? Host
• ????? t? Default Gateway ???e Host ?a ?p?epe ?a
  ??at? µ?a d?ad??µ? (route) ??a ???e ap?µa???sµ???
  d??t?? se ??a t?p??? Routing Table
• ?a??de??µa
• 192.168.0.13 (IP Address)
• 255.255.255.0 (Network Mask)
• 192.168.0.1 (Default Gateway)

59
?p?d?s? IP d?e????se??

• ?e t? ß???e?a t?? TCP/IP software
• Stat???
• ape??e?a? ap?d?s?
• Routers, Servers, Printers
• ??t?µata
• DHCP Server
• Client Computers

60
?p??t?s? IP d?e????se??

• Public Addressing
• Registered Internet IP addresses
• µp????? ?a s??de???? ape??e?a? st? Internet
• ISPs (Internet Service Providers)
• Private Addressing
• Non-Registered Internet IP addresses
• p.?. 10.0.0.0
• de µp????? ?a s??de???? ape??e?a? st? Internet
• ??e?????ta? ??p??? ??? (Network Address
  Translation) ? ??p??a ?p??es?a Proxy ??a ?a
  s??de???? (pe???aµß??eta? se µe?????? routers,
  proxy servers ? firewalls)

61
???µ?????s?

• ? Router A p?? e???e? ta Segment1 Segment2
  p??se????e? ta 2 a?t? tµ?µata d??t??? ape??e?a?

• ? Router A de? µp??e? ?a p??se???se? ape??e?a? ta
  Segment3 Segment4 ????? ??p??a ß???e?a
  (indirect routing)
• ??? p??se???se?? Static Dynamic Routing

62
???µ?????s? pa??de??µa
63
DNS ?? e??a?

• Domain Name System
• ?a???e? ??a? t??ef????? ?at????? ??a t??? IP
  a???µ??? (DNS service)
• ??a ?e?a????? ?ata?eµ?µ??? ß?s? ded?µ???? µe
  ???µata

• Top Level Domains (TLD)
• p.?. gr, uk, us ? com, org
• Mid-Level Domains
• p.?. ac, co
• Organization names
• p.?. ekdd, uoa
• Machine names
• p.?. softlab, theseas

64
DNS ??? ?e?t????e?

• ???e Domain pe???aµß??e? ??a? ?/? p?? s??t??e?
  ??a? p??a?a p?? ape??????e? ta ???µata t?? d????
  t?? domain
• To DNS protocol ep?t??pe? st??? ?/?? ?a pa??????
  p????f???e? ap? t?? p??a?a ?ts? ????? t??
  p?a?µat???? IP d?e????se??
• ?ta? ??a? local nameserver de µp??e? ?a
  apa?t?se?, ?? e??t?se?? d??µ???????ta? se ??????
  DNS servers t?? domain
• Sta ap?te??sµata t?? e??t?se?? µp??e? ?a ???e?
  caching

65
DNS Management
66
Domains Zones

• Name Servers ta p?????µµata p?? ??at???
  p????f???e? ??a t? domain namespace
• ?? Name Severs s?????? ??at??? p????f???e? ??a
  Zones (??a µ???? t?? domain namespace)
• ?? Name Severs ????? d??a??µata ??a µ?a ?
  pe??ss?te?e? Zones µp??e? ?a µetaß?ß?????
  d??a??µata (delegation) se ?????? Name Severs ??a
  ?????? d?a?e???s??

• ?.?. t? Domain ca pe???aµß??e? ??a ta ded?µ??a
  ??a t? ca s?? ta ded?µ??a ??a ta ab.ca, on.ca ?a?
  qc.ca
• ? Zone ca pe???aµß??e? µ??? ta ded?µ??a ??a t? ca
  ta ?p??a ?? ep? t? p?e?st?? e??a? de??te?
  (pointers) sta e???s??d?t?µ??a subdomains p??
  e??a? ta ab.ca, on.ca qc.ca p?? e??a? ?e????st?
  Zones
• ta subdomains bc.ca sk.ca a?????? d?a?e???st???
  st? ???? ca

67
???s?µa Links

• http//www.allwhois.com
• ??a a?a??t?s? ?p????d?p?te domain name
• http//www.internic.net/regist.html
• ??a p????f???e? d?a?e???st?? µ?t???? top-level
  domains
• ??t? ap? t?? e????? t?? ICANN
• http//www.iana.org/root-whois/index.html
• ??a p????f???e? d?a?e???st?? µ?t???? top-level
  domains a?? ???a
• https//grweb.ics.forth.gr
• ? e???????? d?a?e???st?? t?? µ?t???? .gr
• ?????? ?p?t??p? ???ep?????????? ?a??d??µe???
• http//www.ripe.net
• Regional Internet Registry for Europe
  (p????f???e? ??a d??t?a)
• ??a a?a??t?s? http//www.ripe.net/perl/whois/

68
URLs ?? e??a?

• Uniform Resource Locators (URLs)
• A?af????ta? ?a? ?? Uniform Resource Identifiers
  (URIs)
• Ge???? µ??f? URL
• ltprotocolgt//ltdomain namegt/ltlocal namegt
• p.?.
• http//pse.primedu.uoa.gr/index.html
• ftp//pse.primedu.uoa.gr/users/araptis

69
Hypertext Transfer Protocol (HTTP)

• ???t?????? t?? application-level
• ???t??? Client/server
• HTTP client is (eg) a web browser (p.?. Internet
  Explorer)
• HTTP server is a web server (p.?. IIS)
• ? client a????e? ??a TCP connection se µ?a port
  t?? server (s?????? st?? 80)
• st???e? ??a HTTP request st?? server
• ? server apa?t? µe ??a HTTP response
• HTTP/1.0 ep?t?epe µ??? connectionless message
  passing
• ???e request/response apa?t??se ??a s??des?
• ??a ?a ???e?? download µ?a se??da µe e????e?
  apa?t??se p???ap??? s??d?se??
• p??? overhead p?? µp??e? ?a ?pe?f??t?se? t??
  server
• HTTP/1.1 pa???e? µ?a µ???µ? s??des? by default
• µ???? ???e? ? s??des? µeta?? client server,
  pa?aµ??e? a????t? µ???? ??p???? ?a t?? d?a???e?
  (? ?a ???e? timeout)
• ? client µp??e? ?a st???e? p???ap?? requests
  ????? ?a pe??µ??e? apa?t?se??
• p.?. µp??e? ?a ??t?se? ??e? t?? e????e? µ?a?
  se??da? µe t? µ?a

70
HTTP Request

• First line
• Method
• URL
• HTTP version
• HTTP Headers
• Blank line
• (Optional) Entity

71
HTTP Response

• First line
• HTTP version
• Response code
• Response text
• HTTP Headers
• Blank line
• (Optional) Entity

72
HTTP Methods

• ??af??et???? µ???d?? ep?t??p??? d?af??et?????
  t??p??? µetaf???? ded?µ????
• µe????? ap? a?t?? e??a?

Method Purpose
GET Request a specific object
HEAD Request header for a specific object
POST Send information as an entity
PUT Publish entity to server
73
HTTP Examples (1)
First Line

• Http Request Client asking for a file
  /webdev/example.html to be sent
• GET /webdev/example.html HTTP/1.1
• Host cis1.msroot.student.paisley.ac.uk
• User-Agent Mozilla/5.0 (X11 U Linux i586
  en-US rv0.9.3) Gecko/20010808
• Accept text/xml, application/xml,
  application/xhtmlxml,
  text/htmlq0.9, image/png, image/jpeg,
  image/gifq0.2, text/plainq0.8,
  text/css, /q0.1
• Accept-Language en-us
• Accept-Encoding gzip, deflate, compressq0.9
• Accept-Charset ISO-8859-1, utf-8q0.66,
  q0.66
• Keep-Alive 300
• Connection keep-alive
• Referer http//cis1.msroot.student.paisley.ac.uk/
  webdev/index.html

Headers
74
HTTP Examples (2)
First Line

• Http Response Server responds as following
• HTTP/1.1 200 OK
• Date Wed, 14 Nov 2001 132718 GMT
• Server Apache/1.3.9 (Unix) Debian/GNU
  PHP/4.0.3pl1 ApacheJServ/1.1
• Last-Modified Fri, 19 Oct 2001 084800 GMT
• ETag "143a7-1788-3bcfe8c0"
• Accept-Ranges bytes
• Content-Length 402
• Keep-Alive timeout15, max100
• Connection Keep-Alive
• Content-Type text/html charsetiso-8859-1
• lthtmlgt
• ltheadgt
• lttitlegtHTML Quick Examplelt/titlegt
• lt/headgt
• ltbodygt
• lth1gtQuick Examplelt/h1gt

Headers
Entity
75
HTTP Examples (3)

• Http Request Client asking for a file to be
  sent only if it has been modified since the last
  time it saw it, to save on bandwidth
• GET /webdev/newexample.html HTTP/1.1
• Host cis1.msroot.student.paisley.ac.uk
• User-Agent Mozilla/5.0 (X11 U Linux i586
  en-US rv0.9.3) Gecko/20010808
• Accept text/xml, application/xml,
  application/xhtmlxml, text/htmlq0.9,
  image/png,image/jpeg, image/gifq0.2,
  text/plainq0.8, text/css, /q0.1
• Accept-Language en-us
• Accept-Encoding gzip, deflate, compressq0.9
• Accept-Charset ISO-8859-1, utf-8q0.66,
  q0.66
• Keep-Alive 300
• Connection keep-alive
• If-Modified-Since Fri, 19 Oct 2001 084806 GMT
• If-None-Match "143a3-884-3bcfe8c6"
• Cache-Control max-age0

First Line
Headers
76
HTTP Examples (4)
First Line

• Http Response Server responds as following
• HTTP/1.1 304 Not Modified
• Date Wed, 14 Nov 2001 131936 GMT
• Server Apache/1.3.9 (Unix) Debian/GNU
  PHP/4.0.3pl1 ApacheJServ/1.1
• Connection Keep-Alive
• Keep-Alive timeout15, max100
• ETag "143a3-884-3bcfe8c6"

Headers
77
Caching

• ?? browsers ?????? cache st?? se??de? ??a ?a
  µe??s??? t? downloading
• s??t????? ??a? p??s????? ???? ap????e?s?? (cache)
  ??a t?? p??sfate? se??de?
• ?ta? ??te?ta? µ?a se??da, e??????? a? ?p???e? st?
  cache
• a? ???, st???eta? ??a GET request
• ?ta? f???e? t? response message,
• pa???s???eta? ? se??da ap????e?eta? st? cache
  (µa?? µe t?? p????f???a p?? ß??s?eta? st??
  header)
• a? e??a? ?d? st? cache, st???eta? ??a GET request
  µe ??a header If-Modified-Since µe ta ded?µ??a
  t?? cached se??da?
• ?ta? f???e? t? response message,
• a? ? ??d???? status e??a? 200, pa???s???e?
  ap????e?e? t? se??da st? cache
• a? ? ??d???? status e??a? 304, t?te pa???s???e?
  t?? cached version

78
Troubleshooting

• ?? p??t? p???µa p?? ?a p??pe? ?a ????????µe
  e??a? ? t?p?????a t?? d??t??? µa?.

Internet
Internet
PC
Cable / DSL Modem
Router/Gateway/Firewall
79
Troubleshooting
PC
Internet
Cable / DSL Modem
Hub/Switch
Router/Gateway/Firewall
Corporate Firewall
Internet
Company network
PC
80
(No Transcript)
81
(No Transcript)
82
Troubleshooting

• ???????µe t?? f?s??? s??des? t?? ?p?????st? µe t?
  d??t??.
• ???????µe a? t? ?a??d?? e??a? s?st? t?p??et?µ???
  ?a? st?? d?? ???e? t??. ??de??µ???? t?
  ap?s??d???µe ?a? t? ?a?as??d???µe ??a ?a e?µaste
  s???????.
• ???????µe t? ?a??d?? ??a t???? f???? ? ?????
  ?at?????a

83
Troubleshooting

• ?a ?a??d?a s?µf??a µe t? ???s?µ?t?ta t???
  ???????ta? se 3 e?d?.
• Straight through (client 2 switch, router 2
  switch)
• Cross-over (client 2 client, router 2 router)
• Roll-over (terminal console ap? router, ?
  manageable switch)
• ?? t?p?? t?? ?a??d??? p?? af????? t?? p???t?ta
  e??a? ?? e???
• UTP (unshielded twisted pair)
• FTP (foiled twisted pair)
• STP (shielded twisted pair)

84
Troubleshooting
??p?a fa??eta? ? t??p?? s??des?? t?? ?a??d???
straight ?a? µe ta d?? standard.
85
Troubleshooting
?? cross-over, a? pa?at???sate e??a? st?? µ?a
???? t?? straight µe t? T568B standard ?a? ? ????
ep?s?? straight, a??? µe t? T568A standard. H
d?af??? t?? d?? standard e??a? ? ??s? st??
connector t?? p??t??a?? ?a? t?? p??s???? d?sµ??
(d??ad? t?? ?e??a???? ?sp?? p??t??a?? -
p??t??a??, ?sp?? p??s??? p??s???)
86
Troubleshooting

• Se????? 1 - PC -gt DSL/Cable modem ?p?????????µe
  µe t?? ISP ??a ?a µ????µe a? ???s?µ?p?????e
  dynamic ? static IP configuration. ?a pe??ss?te?a
  DSL ?a? cable modem ???s?µ?p????? t? dynamic
  mode, ?p?te ?a?? e??a? ?a d???µ?s??µe t? DHCP
  p??ta.
• Se????? 2 - PC -gt Gateway device ?d? ??
  ???µ?se?? e??a? a?????a µe t? p?? e??a?
  ???µ?sµ??? ? s?s?e?? gateway. ?a?? ? t?p???
  s??desµ?????a e??a? ? DHCP.
• ? DHCP (Dynamic Host Configuration Protocol)
  server d??e? d??aµ???? d?e????se?? st??? clients
  t?? ?p?d??t??? t??.

87
Troubleshooting

• Se????? 3 - PC -gt Hub/switch -gt Gateway device -gt
  DSL or cable modem ???pe ß?µata 1 ?a? 2.
• Se????? 4 - PC -gt ?ta????? ???t?? ?p?????????µe
  µe t?? d?a?e???st? d??t??? ?a? ??t?µe a? t?
  d??t?? µa? ???s?µ?p??e? dynamic ? static IP
  addressing.

88
Troubleshooting
TCP/IP manually configured with static IP
configuration
TCP/IP configured for DHCP / dynamic IP addressing
89
ipconfig
90
ipconfig /all
91
ipconfig /all ????? s??des? d??t???
92
Windows XP Network Connection Details
93
ping 127.0.0.1.

• St?? ??aµµ? e?t???? p???t???????µe ping
  127.0.0.1.

94
Troubleshooting

• ??t? e??a? ? loopback address t?? PC µa?. ?
  e?t??? ??e? st? PC µa? ?a ste??e? ??a pa??t? st??
  ea?t? t??. ???a? ??a? ap??? t??p?? ??a ?a
  ßeßa?????µe ?t? t? TCP/IP d???e?e? s?st? st??
  ?p?????st? µa?.
• ?? ? e?t??? ap?t??e? t?te p??pe? ?a
  ep?d?????s??µe ? ?a e??atast?s??µe ap? t?? a???
  t? TCP/IP. ?at?p?? ?????µe ping st?? IP address
  t?? PC µa? ??a ?a ßeßa?????µe ?t? ? ???ta d??t???
  d???e?e? ?a??????. ?? a?t? ap?t??e?, pe???µe ap?
  t?? a??? t??? drivers t?? ???ta? d??t???.

95
Troubleshooting

• ???????µe ??a t?? ?pa??? Firewall
• ???????µe t?? s??des?µ?t?ta µ???? t?? ep?µe??
  ??µß?
• ???s??? e?? ??a ping ap?t??e? de? s?µa??e? a?t?
  apa?a?t?ta ?e??? ??µß?. ?p??e? ?a e??a? ??a
  switch, ??a? router, ? ??a firewall ???µ?sµ??a ?a
  ap???e???? ta pa??ta ICMP (se a?t? a???e? ?a? t?
  ping). ??? ? e?t??? traceroute pe??se? t??
  s?s?e?? p?? de? apa?t? se ping t?te p??a??? t?
  ????? e??a? a????.

96
Ping www.uoa.gr
97
Nslookup www.uoa.gr

• ??e???? DNS Server

98
Nslookup www.uoa.gr

• ??? ?p???e? p??ß??µa st?? DNS server ????µe t?
  a??????? µ???µa.

99
??d???? ???µ?se?? ???µat?????a ?p?????st??

• ?? ?a???e? ???µat?????a? ?a p??pe? ?a
  efa?µ????ta? se ??e? t?? e??atast?se?? t??
  p??s?p???? ?p?????st?? t?? e??ast?????.
  ?????????? µe????? s?st?se?? ?? ?p??e? µp??e? ?a
  fa???? ???s?µe? st?? ?a????sµ? ?a?????
  ???µat?????a?.
• Ge????? ?ate????se??
• G?a p???? s?µßat?t?ta µe pe??ß?????ta DNS, ??
  a???????? ?a?a?t??e? s???st?ta? ?a
  ???s?µ?p?????ta? st? st?at????? ???µat?????a? ??a
  ??a ta ???µata a-z, A-Z, 0-9 ?a? -.
• ???? ?? ?p????p?? ?a?a?t??e?, ??a pa??de??µa t?
  underscore _, de? e??a? ??????? RFC 1123
  ?a?a?t??e?, de? s???st??ta? ?a? ?a p??pe? ?a
  ap?fe????ta?.

100
??d???? ???µ?se?? Servers

• Windows Servers
• ?a ???µata t?? Servers p??pe? ?a e??a? µ??ad???
  st? d??t?? µa? ?a? ?a µ?? ?epe????? t??? 15
  ?a?a?t??e?. S???eta ???µata servers ?e???? e??a?
  p??t?µ?t?a ?a? saf?? p?? ???s?µa sta tµ?µata
  d?a?e???s?? ?a? ?p?st??????. ?ts? p??te??eta? ?
  ???µat?????a XXXXSRV ?p?? XXXX ? ??d???? t??
  site.

101
??d???? ???µ?se?? Clients

• ?a?? e??a? ?a a????????e? ????? ???µat?????a µe
  a?t? t?? Servers ?p?? ? ??d???? ?e?t???????t?ta?
  ?a e??a? PC a??? ep?p???? ?a ?p???e? ?a? µ?a
  a????sa a???µ?s? (XXXXPCyy, ?p?? XXXX t? site
  name ?a? yy ? a????sa a???µ?s?) e?t?? ap? t??
  Administrator Client ? ?p???? ?a ??e? ?? ??d???
  ?e?t???????t?ta? ADPC ?a? de? ?a ??e? a????sa
  a???µ?s? µ?a? ?a? e??a? µ??ad???? se ???e
  e??ast???? (XXXXMPC, ?p?? XXXX t? site name).
• ?a?ade??µata
• NAVPC01
• NAVPC19
• NAVADPC

102
??d???? ???µ?se?? Users

• ?e??ß????? e??as?a? st??? clients
• ?? pe??ß????? e??as?a? st??? clients ?a?????eta?
  µ?s? t?? Group Policy Objects. ???????µe t???
  ???ste? ???e e??ast????? se 2 ?at?????e? ?a?
  d?µ???????µe ap? ??a OU ??a t?? ???e µ?a. ?ts?,
  ????µe t? OU Ordinary Users ??a t??? ap????
  ???ste? ?a? t? OU Advanced Users ?p?? e?e? ?a
  ?p????ta? ta accounts p?? ????? ep?p????
  d??a??µata ?p?? server operators, ?.a.

103
??d???? ???µ?se?? Users

• G?a t??? Ordinary Users d?µ???????µe t? ????
  Ordinary Users Policy GPO (?p?? XXXX t? site st?
  ?p??? a???e? t? e??ast????, ??a pa??de??µa GEOL
  a? a?afe??µaste st? e??ast???? t?? Ge????????
  s?????) p?? ????e? ta e???
• T?te? d??f????? pe?????sµ??? st? ???st? ?p?? de?
  ep?t??pe? t?? p??sßas? st? drive c, ???ße?
  d??f??a e?????d?a ap? t? desktop, ?.a.
• ???e? redirect t? my documents st? Server t??
  e??ast????? p?? a?afe??µaste