???%20360:%20???t?a%20?p?????st??.%20??sa????

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??? 360???t?a ?p?????st??.??sa????

• ??d?s??? ???st?? ?a?a???t??

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G?at? ???t?a ?p?????st??

• ?p??e???s?a??? ?fa?µ????
• ?.?., e? ap?st?se?? p??sßas? se ß?se?? ded?µ????.
• ????????µ?s? ???µ?t?? ap? t?? ?ataµe??sµ? p????
  (research sharing)
• ?e?t??s? a???p?st?a? (reliability)
• ????a??? ?fa?µ????
• ????t?? ???ste?
• ???sßas? se p????f???e? µ?s? ????t?? t??ef???? ?
  f???t?? ?p?????st?.
• ?p????????a?? µ?s?

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???ß??µa

• T????µe ?a ?t?s??µe ??a d??t?? t? ?p???
• Ta µp??e? ?a µe?a???e? se pa???sµ?a ???µa?a
  (epe?t?s?µ? - scalable).
• Ta µp??e? ?a ?p?st????e? ??a e???? efa?µ???? ap?
  µetaf??? a??e??? (file transfer), t??ed??s?e??
  (teleconferencing), ??e?t?????? eµp????
  (electronic commerce), ??f?a??? ß?ß??????e?
  (digital libraries)
• ??? s?ed?????µe ??a t?t??? d??t?? (????? ?a?
  ????sµ??? hardware and software)
• ??? 360 ? st???? t?? µa??µat?? e??a? a???ß?? ?a
  d?se? ap??t?s? st?? p?? p??? e??t?s?!

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?? ?a ?a?????µe

• A. Tanenbaum, Computer Networks
• ?e?????? µa??µat??
• ?p?p??s?ete? ?????f???e?
• www.eng.ucy.ac.cy/Christos/Courses/ECE360

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?pa?t?se?? ap? ta d??t?a

• ????? ??t??? t?? apa?t?se?? ?a? t??? pe?????sµ???
  t?? d??t???
• ?????aµµat?st?? (application programmers) ??????
  ?p??es?e? t?? ?p??e? ?a a???p???s??? ?? efa?µ????
  t???, p.?. pa??d?s? pa??t?? µ?sa se ded?µ??a
  ??????? p?a?s?a ? a???p?st? pa??d?s? pa??t??
  (reliable delivery).
• S?ed?ast?? (network designers) ep?d??????
  pa?a?????? ???s? t?? p???? t?? d??t???
• ?a????a? ?p??es??? (network provider) ep?d???e?
  d??t?? t? ?p??? e??a? e????? st? ?e?t?????a ?a?
  st? s??t???s?.

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?pa?t?se?? S??e?t???t?ta (connectivity)

• ?p????????a µeta?? s?????? ?p?????st??
• ?as???? d?µ???? µ???de?
• ??µß??
• ?p?????st?? (computers, hosts, servers),
  d??µ?????t?? (routers), µeta???e?? (switches)
  ??p.
• ?e??e??
• ?µ?a???????, as??µate?, ?pt???? ??p.
• S?µe?? p??? s?µe?? (point-to-point) ? p???ap???
  p??sßas?? (multiple access)

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?pa?t?se?? S??e?t???t?ta (connectivity)

• ???t?a ?a? ??ad??t?a

??? ? pe??ss?te??? s??dedeµ???? ??µß??
??? ? pe??ss?te?a s??dedeµ??a d??t?a
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?pa?t?se?? ?p?d?t???? ?ataµe??sµ?? p????
(resource sharing)

• ????p?e??a µe d?a??es? ?????? (Synchronous Time
  Division Multiplexing)
• ????p?e??a µe d?a??es? s????t?ta? (Frequency
  Division Multiplexing)

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?pa?t?se?? ?p?d?t???? ?ataµe??sµ?? p????
(resource sharing)

• Stat?st??? p???p?e??a (Statistical multiplexing)
• ?ata??µ? ?????-d?ast?µ?t?? (time slots) ß?s? t??
  ??t?s??

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?pa?t?se?? ?p?st????? ?????? ?p??es???

• ?a????a p?? ?a µp????? ?a pa?????? ?p??es?e? ?p??
• ????p?st? ep????????a (reliable communication)
• ?p????????a µe µ???? ?a??st???s? (low delay)
• ?? ?a???? ???ße? t?? p???p????t?ta t?? d??t???
  ap? t??? p????aµµat?st??

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?pa?t?se?? ?p?d?t???t?ta (Performance)

• ????? ????? (bandwidth, throughput)
• Hz vs. bps
• ?a??st???s? (latency or delay)

Latency Propagation Transmission Queue
Propagation Distance / Speed of light
Transmission Packet size / Bandwidth
Throughput TransferSize / TransferTime
TranferTime RTT TransferSize / Bandwidth

• ?p??e?a pa??t?? (packet loss)
• ??a??µa?s? ?a??st???s?? (jitter)

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?a??de??µa 1
??? ?p?????st?? ß??s???ta? se ap?stas? 100Km.
??s?? ?????? ??e???eta? ??a t? µet?d?s? 1?? ap?
t?? ??a st?? ???? ded?µ???? ?t? s??d???ta? µe
?e??? ????t???t?ta? 100Mbps st?? ?p??a
??e?t??µa???t??? ??µata ta??de???? µe ta??t?ta
3x108 m/s
??t?µa
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?a??de??µa 2
??? ?p?????st?? ß??s???ta? se ap?stas? 100Km.
??s?? ?????? ??e???eta? ??a t? µet?d?s? 1?? ap?
t?? ??a st?? ???? ded?µ???? ?t? s??d???ta? µe
?e??? ????t???t?ta? 100Mbps st?? ?p??a
??e?t??µa???t??? ??µata ta??de???? µe ta??t?ta
3x108 m/s
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?pa?t?se?? ?p?d?t???t?ta (Performance)

• G???µe?? ?a??st???s?? ????? ????? (Delay
  Bandwidth product)
• ? a???µ?? t?? d?ad???? ??f??? (bits) p?? ??????
  µ?sa st? ?a????. (Amount of data in flight or
  in the pipe)
• ?a??de??µa

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???t??a ?eta?????

• ?eta???? ?????µat?? (circuit switching)
• ???ta e?asfa???eta? ?a? p????ate?ta? (reserved)
  f?s??? s??des? µeta?? ap?st???a ?a? pa?a??pt?
• ?et? ?e???? ? µet?d?s? t?? p????f?????
• ?? ?????µa p?? s??d?e? t? ap?st???a ?a? pa?a??pt?
  ???s?µ?p??e?ta? ap???e?st??? ??a t?? ep????????a
  t?? d??.
• ?? ap?d?t??? ???s? t?? p???? t?? d??t???
• ?eta???? ?a??t?? (packet switching)
• ?e? ?p???e? ape??e?a? s??des? µeta?? ap?st???a
  ?a? pa?a??pt?. ? ap?st???a? ?e???? aµ?s?? ?a
  st???e? p????f???e?.
• ???e pa??t? ß??s?e? t? d??µ? t?? µ?sa st?
  d??t??
• ??s???? ? pa???? e????se?? ??a t?? p???t?ta
  ?p??es?a?.
• ???????? ?eta???? ?????µat?? (virtual circuit
  switching)

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???t?????? (protocol)

• ? S?µf???a a??µesa se d?? ep??????????ta µ???, ??
  p??? t?? t??p? µe t?? ?p??? ?a p??????se? ?
  ep????????a.

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???t??? ?e??t?-???p??et?t? (Client-Server model)
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???t??? ?p????????a? ?µ?t?µ?? ??µß??
(Peer-to-peer Communication)
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?? µp??e? ?a p?e? ?????

• ???? st? f?s??? ep?ped? (bit errors)
• ?p??e?a pa??t?? e? a?t?a? s?µf???s??
  (congestion and buffer overflow)
• ?p??e?a ?e??e?? ? ??µß??
• ?a??ta ft????? st?? d??t? ?a??ste??µ??a
• ?a??ta ft????? st?? d??t? e?t?? se????
  (out-of-order)
• ??p???? t??t?? ?p????pte? ? pa?eµßa??e? st??
  s??d?a??a?? µeta?? d?? ??µß??.

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????te?t????? ???t???
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G?at? ?p?peda

• ?ataµe??sµ?? t?? p???p????? p??ß??µat?? se
  µ????te?a, p?? ap?? p??ß??µata.
• ???e ep?ped? e??a? ?pe????? ??a t?? a?t?µet?p?s?
  ??p???? p??ß??µ?t?? p?? µp??e? ?a p????????.
• ???e ep?ped? ???ße? t?? p???p????t?ta t?? ap? ta
  ?p????pa ep?p?da ?a? t??? ???ste?.
• ?a??te?? d?µ? ap?te???µe?? ap? p???? st???e?a
  (modular).
• ??a ?a???????a ?p??es?a µp??e? ?a ???p????e?
  µetat??p??ta? µ??? ??a ep?ped? (st??µa).

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?a?ade??µata St??ßa? ???t???????
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?a??de??µa ???? ????µ?t?? µeta?? St??µ?t??
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???t??? ??af???? OSI (Open System
Interconnection)
?fa?µ????
?a???s?as??
S???d??
?etaf????
???t???
?e????
F?s???
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???t??? OSI

• F?s??? st??µa (Physical Layer)
• ?et?d?s? a?at???ast?? bits (0 ? 1) ap? t??
  ap?st???a st?? d??t?.
• St??µa ?e???? ?ed?µ???? (Data Link Layer)
• ?eµa???e? ta ded?µ??a se p?a?s?a ded?µ????
  (frames)
• ?p?ßeßa???e? ?t? ? ep????????a t?? F?s????
  st??µat?? e??a? a???p?st? (??a?s?a epa???e?s??
  -acknowledgement frames)
• ?????e?s? ?a? ep?d?????s? ?a??? (Error detection
  and correction).
• ??e???? ???? (flow control).

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???t??? OSI

• St??µa ???t??? (Network Layer)
• ???µ?????s? pa??t??
• ??e???? s?µf???s??
• ??d?s? ???a??asµ?? (billing)
• St??µa ?etaf???? (Transport Layer)
• ?eµa???e? ta µ???µata se µ????te?e? µ???de?
• ?p?ßeßa???e? ?t? ??e? ?? µ???de? ft????? st? ????
  ???? ?a? epa?as??a?µ????e? t? µ???µa.
• ????p?e??a s??d?se??/s??µ?? (steams)
• ?p??es?e? µetaf???? pa??t?? ap? ???? se ????
  (end-to-end). (p.?., a???p?st? µetaf???
  ded?µ???? st?? d??t?).
• ??e???? s?µf???s?? (congestion) ?a? ???? pa??t??

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???t??? OSI

• St??µa S???d?? (Session Layer)
• ?p??at?stas? s???d?? µeta?? d?af???? µ??a???
  (sessions)
• ??a?e???s? s??t???? (token management)
• S???????sµ?? (synchronization)
• St??µa ?a???s?as?? (Presentation Layer)
• ??d???p???s? ded?µ????
• St??µa ?fa?µ??? (Application Layer)
• S?µßat?t?ta µeta?? efa?µ????

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???t??? ??af???? TCP/IP
?e? ????? ???p????e?
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?at??????p???s? ???t???
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??p??? ???t?? (Local Area Network)
?a?t????? (Ring)
Ethernet
???t?a ??p?µp??
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?s??µat? ??p??? ???t?? (Wireless Local Area
Network)
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??t??p???t??? ???t?? (Metropolitan Network)
???t?? ?a??d?a??? ???e??as??
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???t?? ???e?a? ?e?????? (Wide Area Network)
?p?d??t?? (subnet)
???µ?????t?? (router)
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?? ???t??? t?? ??ad??t???