pped etaf Transport Layer

1
?p?ped? ?etaf????(Transport Layer)

2
?e??????

• ? ????? t?? ep?p?d?? µetaf????
• ?a st???e?a t?? p??t??????? µetaf????
• ?a p??t?????a µetaf???? t?? ??ad??t???
• UDP (User Datagram Protocol)
• RPC (Remote Procedure Call)
• RTP (Real-time Transport Protocol)
• TCP (Transport Control Protocol)
• ???e? µ??f?? t?? TCP
• T?µata ap?d?s??

3
?p??es?e? IP Best-Effort
Data

• ? ?p??es?a p?? te???? p??sf??e? t? ep?ped?
  d??t??? ??e? ta a??????a ?a?a?t???st???
• ?a??ta te???? pa?ad????ta? e?t?? se????
  (out-of-order)
• ?p??e? ?a pa???s?ast??? pa??ta pe??ss?te?e? ap?
  µ?a f???? (duplicates).
• ?a pa??ta pa?ad?d??ta? µet? ap? a??a??et?
  ?a??st???s?.

4
?p??es?e? t?? ?p?p?d?? ?etaf????

• ???sf??e? ?t? ?a? t? ep?ped? ?e???? ?ed?µ????!
• ?????ta? t?? pa??d?s? t?? µ???µ?t??
• ?a?ad?de? ta µ???µata µe t? s?st? se???
• ?p?st????e? a??a??et? µ??e??? µ???µ?t??
• ?p?st????e? t? s???????sµ? µeta?? t??
  ep??????????t??
• ?p?t??pe? t? ??e??? t?? ???? p??? t? pa?a??pt?
• ?p?st????e? t?? p???p?e??a p???ap??? ???st??
• G?at? t?te ??e???eta? t? ep?ped? µetaf????

5
G?at? ??e???eta? t? ?p?ped? ?etaf????
If all real networks were flawless and all had
the same service primitives and were guaranteed
never, ever to change, the transport layer might
not be needed A. Tanenbaum

• ?p?ped? ?e???? ded?µ????
• ? s??des? e??a? ?e???? e?????
• ?e? ?p???e? pe??pt?s? pa??d?s?? ded?µ???? e?t??
  se????
• ?e?????sµ???? a???µ?? s??d?se??

6
??e???? ???? ?a? ??e???? S?µf???s??

• ??e???? ???? (Flow Control)
• ??e???? S?µf???s?? (Congestion Control)
• ?????e? t? ??? t?? ap?st???a ?ts? ?ste ?a µ?
  st???e? pe??ss?te?a ded?µ??a ap? ?sa µp??e? ?a
  µetaf??e? t? d??t??

7
St???e?a t?? ???t??????? ?etaf????
? s??s? t?? ep?p?d?? ???t???, ?etaf???? ?a?
?fa?µ????.
8
??e????se?? ?a? ????p?e??a
9
??e????se?? ?a? ????p?e??a

• ??a d?ad??as?a d?µ?????e?ta? st?? ?p?????st? 2
  ?a? p??s?????te st? d?e????s? 1522.
• ??a d?ad??as?a st?? ?p?????st? 1 ap? t? TSAP 1208
  ??t? ?a s??de?e? µe t?? 1522 t?? e??p??et?t? 2.
• ?f?? s??de???? (connect), a??????? ?a
  a?ta??????? µ???µata
• ?f?? te?e??s??? e?e??e?????? (release) t??
  s??des?.

10
??e????se?? ?a? ????p?e??a

• ??? ??a p????aµµa ???e? se p??a d?e????s? ?a
  s??de?e?
• Sta?e??? d?e????se?? (TSAP), p.?.,
• http port 80
• ftp port 21
• telnet port 23
• smtp port 25
• ???aµ???? ??e????se?? (Initial Connection
  Protocol)
• Name or directory server

11
??µ??????a S??d?se?? (Connection Establishment)

• ?p??es?e? µe ? ????? s??des?
• G?a ?a ep?te???e? µ?a s??des? µeta?? d?? hosts,
• ? host 1 st???e? t? µ???µa ?t? ???e? ?a
  d?µ??????se? µ?a s??des? (connection request (CR
  ? SYN))
• ? host 2 apa?t? µe t?? epa???e?s?
  (acknowledgement (ACK))
• O host 1 a????e? ?a st???e? ta p??ta ded?µ??a
  (DATA).
• ???ß??µa ?? ?a s?µße? a? ??p??a µ???µata ?a????,
  ?a??ste??s??? ? ft?s??? pe??ss?te?e? ap? µ?a
  f???? (duplicates)
• ?.?., Se µ?a s??d?a??a?? µe t??pe?a, a????e? µ?a
  s??des?, µet? ???eta? µetaf??? ???µ?t?? ?a? t????
  ??e??e? ? s??des?.
• ?? ?a s?µße? a? ? ?d?a s??d?a??a?? ?a?aeµfa??ste?
  (p?? µp??e? ?a ?a?aeµfa??ste?)

12
??µ??????a S??d?se?? (Connection establishment)

• ?? ?p???s??µe p?? ?p???e? µ???st?? ?????? T µet?
  ap? t?? ?p??? ??a pa??t? de? µp??e? ?a s??e??se?
  ?a ?p???e?.
• G?a ?a ap?fe?????? ?s? t? d??at? pe??ss?te?a
  p??ß??µata, ???s?µ?p??e?ta? t? three way
  handshake ??a t?? d?µ??????a ?p??asd?p?te
  s??des??. ?a ?a?a?t???st??? t?? µe??d?? e??a?
• ? a?????? a???? a???µ?? (seq) e??a? t??a??? (low
  order bits from a clock)
• ? ?a?a??pt?? d?at??e? t?? d??? t?? a???? a???µ?
  (ack)
• ??p???? a???µ?? e??a? apa???e?µ???? ??a ?a
  ap?fe????ta? p??ß??µata ?ta? ??a? ?p?????st??
  a?????p????e? (reset).

13
?p?te??? S??des??
14
?p?f??? ???ß??µ?t??
15
S???????sµ?? µet? ap? ??????p???s?
16
??e?????s? S??des??

• S??t???sµ?? ap?st???a ?a? pa?a??pt? ??e???eta?
  ?a? st?? pe??pt?s? p?? ?a e?e??e???e? µ?a s??des?
• ???s? p???? (µ??µ?) ??a t?? d?at???s? t??
  ?at?stas?? ???e s??des??.

17
?? ???ß??µa t?? ??? St?at??
18
??e?????s? S??des?? (Connection Release)
19
??e?????s? S??des?? (Connection Release)
20
??d??µes? ???µ? ?a? ??e???? ????
?sa buffers
???sa buffers
? pa?a??pt?? s??e??? e??µe???e? t?? ap?st???a ??a
t? µ??e??? t?? e?e??e??? e?d??µes?? µ??µ?? ??a ?a
ap?fe???e? ?pe??e???sµa (buffer overflow)
??????? buffers
21
?a??de??µa
? ?p?t???? ap?st??? µ???µat??, ?p??e?a
µ???µat??
22
????p?e??a
????p?e??a p??? ta p??? (Upward multiplexing)
23
?p?? ???t?????? ?etaf????

• Primitives
• LN LISTEN (??aµ??? s??d?se??)
• ?a??ta
• CR Call Request (????es? d?µ??????a? s??des??)
• CA Call Accepted (?p??t?s? st? CA)
• CLRR Clear Request (?e?µat?sµ?? s??des??)
• CLRC Clear Confirmation (?p??t?s? st? CLRR)
• CRT Credit (??a?e???s? ?a?a?????)

• ?atast?se??
• IDLE
• AWAIT (??aµ??? epa???e?s?? st? CR)
• PWAIT (??aµ??? S??des??)
• EST (established) S??des? ??e? ep?te???e?
• REC pa?a?aß? ded?µ????
• DISC p??sp??e?a ??a ap?s??des?

24
?p?? ???t?????? ?etaf????
25
???t?????a ??ad??t???

• UDP (User Datagram Protocol)
• RPC (Remote Procedure Call)
• TCP (Transport Control Protocol)
• ???e? µ??f?? t?? TCP

26
?et?d?s? Byte Streams

• ?a p??t?????a UDP/TCP/ ????? ??p??e? ?????
  (µ??µ?) st?? ?p??a ?? efa?µ???? ???f??? ?t?
  p????f???a ?????? ?a µetad?s??? st?? pa?a??pt?.
• ?a p??t?????a de? ???????? ta bytes se µ???µata.
• ??? ap?fas??e? t? p??t?????? p?te ?a ste??e? ta
  ded?µ??a st? pa?a??pt?
• ?ta? µa???e? a??et? bytes (maximum segment size)
• ?ta? t? ??t?se? ? efa?µ??? (push operation)
• ?????µet??

27
User Datagram Protocol (UDP)

• ???sf??e? e????ste? ?p??es?e?
• ?????st? ??e??? sfa?µ?t??
• ?e? ?p?st????e?
• ??e??? ???? ? s?µf???s??
• ?pa?aµet?d?s? se pe??pt?s? sfa?µ?t??
• ?a?a?aß? ded?µ???? st?? s?st? se???
• ???a? ap?? ?a? ???sµ??e? efa?µ???? t?
  ???s?µ?p????? ??a µet?d?s? µ? e?a?s??t??
  p????f?????, p.?. f??? ? video ? ??a a?ta??a??
  µ????? µ???µ?t??.

28
?p??efa??da UDP

• UDP Length (s?µpe???aµßa??µ???? ?a? t?? 8 bytes
  t?? ep??efa??da?)
• Checksum (p??a??et???) header, pseudoheader,
  data
• Pseudoheader IP source and destination
  addresses, protocol number and UDP Length

29
Remote Procedure Call (RPC)

• ??te?e? µ?a d?ad??as?a (???t??a) se ap?µa???sµ???
  ?p?????st?
• ? ßas??? ?d?a e??a? ?a ?p???e? µ?a d?ad??as?a ?
  ?p??a t???e? se ap?µa???sµ??? ?p?????st? a??? ?a
  fa??eta? ?t? t???e? t?p???.
• ????e? p??? ap? UDP.

30
Real-Time Transport Protocol (RTP)

• ???t?????? t? ?p??? ???s?µ?p??e?ta? ??a efa?µ????
  p?a?µat???? ?????? (internet radio, internet
  telephony, music and video-on-demand, other
  multimedia).
• ????e? p??? ap? t? UDP
• ????p?e??a d?af???? p???? se ??? ap? UDP segments
• ???sf??e? ep?p??s?ete? ?p??es?e?

31
? ?p??efa??da RTP

• P Padding
• X Extension Header
• CC Contributing Sources
• M Application specific
• Payload type Encoding used

• SeqNum detects lost packets
• Timestamp
• Synchronization source identifier multiplexing
  of sources
• Contributing source mixers

32
Transport Control Protocol (TCP)

• ???sf??e? ?p??es?e? a???p?st?? µetaf???? ???? ap?
  bytes.
• S?????? ?????e? ta ded?µ??a se segments µe 1460
  bytes (??a ?a µ?? ??e???eta? ?a teµa??st??? ap?
  ?aµ???te?a ep?peda, p.?., Ethernet µ???st?
  p?a?s?? 1500 bytes).
• ?p?st????e? p???p?e??a ???s?µ?p????ta? ports
  (TSAP).
• ??e? ?? s??d?se?? t?? TCP e??a? d?p???
  ?ate????s?? (full duplex)
• ?p?st????e? epe????ta ded?µ??a (Urgent data).

33
?? ???t?????? TCP

• ???e TCP byte ??e? t?? d??? t?? 32-bit a????
  a???µ? (sequence number).
• ??af??et???? a???? a???µ?? ???s?µ?p??e?ta? ??a
  t?? epa???e?se?? (ACKs).
• TCP Segmets ap?te????ta? ap? ep??efa??da µe
  20-bytes ?p???e?t??? ?a??? ?a? p??a??et??? ped?a.
  
• ???s?µ?p??e? ta p??t?????a ???s?a????t??
  pa?a????? (sliding window go back n, and
  selective repeat).
• ???a? s?ed?asµ??? ??a ?a ap?fe??e? a?t???afa
  (duplicates) ta ?p??a ????? ?a??ste??se? p??? ?
  ???fte? µ?sa st? d??t??.

34
? ?p??efa??da t?? TCP
35
? ?p??efa??da t?? TCP

• TCP header length ????µ?? t?? 32-bit words p??
  ?p?????? st?? ep??efa??da TCP
• Flags
• URG epe????ta ded?µ??a p?? a??????? ap? t?
  s?µe?? st? ?p??? de???e? t? Urgent Pointer
• ACK epa???e?s?
• PSH (push) ?µes? pa??d?s? st?? pa?a??pt?
• RST ??????p???s? t?? s??des??
• SYN ??t?µa ??a d?µ??????a ??a? s??des??
• FIN ??t?µa ??a ??e?s?µ? t?? s??des??
• Checksum header, pseudoheader, data
• Pseudoheader IP source and destination
  addresses, protocol number and UDP Length
• Options maximum TCP payload

36
S??des? TCP
37
?? ?atast?se?? (states) t?? TCP

• CLOSED de? ?p???e? ??te a?aµ??eta? s??des?
• LISTEN ? e??p??et?t?? (server) a?aµ??e? s??des?
• SYN RCVD ??t?µa ??a s??des? ??e? pa?a??f?e?
• SYN SENT ??t?µa ??a ??a s??des? ??e? sta?e?
• ESTABL ? s??des? ??e? ep?te???e? ?a?
  a?ta???ss??ta? ded?µ??a
• FIN WAIT 1 ? efa?µ??? ??e? ste??e? a?t?µa
  ap?s??des??
• FIN WAIT 2 ? ???? p?e??? pa???aße t? a?t?µa
  ap?s??des??
• TIMED WAIT ?e??µ??e? µ????? ?t?? ??a ta pa??ta
  ?a f????? ap? t? d??t??
• CLOSING ?a? ?? d?? µe???? p??spa???? ?a ??e?s???
  t? s??des? ta?t?????a.
• CLOSE WAIT ? ???? µe??? e?e???p???se ap?s??des?
• LAST ACK ?e??µ??e? µ????? ?t?? ??a ta pa??ta t??
  s??des?? ?a f????? ap? t? d??t??

38
???a?? ?epe?asµ???? ?atast?se?? ??a S??des? ?a?
?p?s??des? TCP.
39
?et?d?s? ?ed?µ???? ???s?µ?p????ta? S??d?se?? TCP
40
???ß??µata t?? TCP

• ?et?d?s? e??? Byte ???e f???
• S??d??µ? ?a??? ?a?a????? (silly window syndrome).
• ?pa?????? t?? a????t?? a???µ?? (sequence number
  overflow)
• ?p?d?s? (keep the pipe full)

41
?et?d?s? ???? Byte ???e F???

• ???ß??µa st?? ap?d?s? af?? ap?st?????ta? 41-byte
  pa??ta µe µ??? ??a byte p?a?µat??? ded?µ??a!
• ??s? Nagles Algorithm
• ?ta? ft????? ded?µ??a 1 byte ???e f???, t?te
• ?f?? ft?se? ? epa???e?s?, ??a ta bytes p?? ?????
  s?ss??e?te? st?? µ??µ? ap?st?????ta? µa?? st?
  ep?µe?? pa??t? ?a? ??a ta ?p????pa f??????ta? st?
  µ??µ? µ???? ?a ep?st???e? ? epa???e?s?.
• ? p?? p??? ??s? de? d???e?e? p??ta
• ?? s?µßa??e? se efa?µ???? p?? ?p?????? ded?µ??a
  p?? de? µp????? ?a pe??µ????? (p.?., ??s? t??
  p??t????? (mouse position)).

42
S??d??µ? ?a??? ?a?a????? (silly window syndrome).

• ? efa?µ??? st?? pa?a??pt? d?aß??e? ta ded?µ??a
  ap? t? µ??µ? ??a byte ???e f???.

• Clarks Algorithm

43
?pa?????? t?? a????t?? a???µ?? (Sequence number
wrap-around)

• 32-bit ????? ????µ??
• ? apa?t??µe??? ?????? epa??????? t?? ?d???
  a????t?? a???µ?? ??a d??f??e? ta??t?te? µet?d?s??
  d??eta? st?? p??a?a.
• G?a ?????? ta??t?te?, ? ?????? epa??????? t??
  ?d??? a???? a???µ?? e??a? p??? µ?????! ?????te???
  ap? t?? µ???st? ??? e??? pa??t?? st? ??ad??t??.

44
?p?d?s? ????? µ???st? pa?????? (Keep the Pipe
Full)

• ?? µ???st? pa?????? µe 16-bit ped?? e??a? 65536.
• Se ??a d??t?? µe RTT pe??p?? 100ms, ? a???µ??
  t?? bits p?? ??e???eta? ??a ?a ?eµ?se? t? ?a????
  se d??f??e? ta??t?te? µet?d?s?? d??eta? st??
  p??a?a.
• G?a ?????? ta??t?te?, ? ap?st???a? p??pe? ?a
  pe?????se? t?? ???µ? µet?d?s?? µe ap?t??esµa t?
  ?a???? ?a ?p????s?µ?p??e?ta?

45
?p??tas? t?? TCP ???s?µ?p????ta? ta ?a?d?a t??
?p??????

• ?? epe?t?se?? p??spa???? ?a ep?f????? ?s? t?
  d??at? µ????te?e? a??a??? st? ?p????? p??t??????
  TCP.
• ?a ep??????????ta µ??? s?µf????? st?? a??? t??
  s??d???e??? ?at? p?s? ?a ???s?µ?p???s??? t??
  ep?????? ? ???.
• G?a ?a ?????? ta p??a?afe????ta p??ß??µata,
  ???s?µ?p?????ta? ?? a??????e? ep??????
• 32-bit timestamp ??a ?a ?e?????e? ta pa??ta t??
  ???e ??????
• ????ap??s?? t?? µ????te??? µ???da? ded?µ????
  (multiplier). ???ad? a?t? ? a???? a???µ?? ?a
  µet?? bytes, µet?? 2 ? 4 ? pe??ss?te?a bytes.

46
??e???? S?µf???s? st? TCP (Congestion Control)

• ?? p??t?????? ??e? d?? a?t?fat????? st?????
• ?a e????e? (µe??se?) t? s?µf???s? ?a? ta ?aµ??a
  pa??ta.
• ?a ???e? ?s? t? d??at? ?a??te?? ???s? t?? p????
  t?? d??t??? ?a? ?a µe??st?p???se? t?
  d?e?pe?a??t??? ??a??t?ta (throughput) t??
  d??t???.
• G?a ?a pet??e? t??? st????? t??
• ????? a????e?se? s?µf???s? t?te µe???e? t? ???µ?
  µe t?? ?p??? ap?st???e? pa??ta.
• ??? de? ?p???e? s?µf???s? t?te p??spa?e? ?a
  ste??e? pe??ss?te?a pa??ta ??a ?a a???se? t?
  throughput.
• G?a ?a ???p???se? t??? st????? t??, e????e?
  d??aµ??? t? pa?????? s?µf???s??.
• ?? TCP d?at??e? µ?a µetaß??t? congestionWindow
  (d?af??et??? ap? t? flowWindow)
• ?? e?e??? pa?????? e??a? p??ta t? e????st? t??
  d??.

47
F?se?? t?? ???????µ??

• ?? pa?????? a????eta? se d?? f?se??
• Congestion Avoidance Se a?t? t? f?s? t? pa??????
  a????eta? ??aµµ??? µe st??? ?a ap?f??e? t?
  s?µf???s?.
• ?? d?? f?se?? ???????ta? ap? ??a threshold.
• ??? t? pa?????? e??a? µ????te?? ap? t? threshold
  t?te ???s?µ?p??e? t? slow start
• ??? t? pa?????? e??a? µe?a??te?? ap? t? threshold
  t?te ???s?µ?p??e? t? congestion avoidance

48
Slow Start vs. Congestion Avoidance

• Congestion Avoidance
• G?a ???e pa?????? p?? pa?a?aµß??eta? ep?t????, t?
  pa?????? a????eta? ?at? ??a

• Slow Start
• G?a ???e epa???e?s? (ACK) p?? pa?a?aµß??eta?, t?
  pa?????? a????eta? ?at? ??a.

49
?p??e?a ?a??t??

• Se pe??pt?s? ap??e?a? pa??t??, t?te t? TCP
  a?t?µata ?p???te? s?µf???s? ?a? s??ep?? µe???e?
  t? ???µ? µet?d?s??
• ?p??e?a pa??t?? a????e?eta? af?? ???e? t? a??????
  ?????µet?? (timer).
• Se pe??pt?s? s?µf???s??
• Threshold congestionWindow/2
• ? ap?d?s? t?? p??t??????? e??a? p??? e?a?s??t?
  st?? ?at?????? ?a????sµ? t?? ?????µ?t???
  (??at?)
• ? ?a????sµ?? t?? ?????µ?t??? e??a? d?s????
  p??ß??µa (??at?)

50
?a??de??µa t?? ?a?a????? t?? TCP
51
?a????sµ?? t?? ?????µ?t???
52
?p?????sµ?? t?? RTT

• ?? TCP e?t?µ? t? RTT ???s?µ?p????ta? t??
  a??????µ?
• ?p??
• ? e??a? t? te?e?ta?? de??µa RTT
• a 7/8
• ?? ?????µet?? ?a?????eta? sa?
• St? a????? TCP, ß2.
• ???ß??µa ?e? ?p??????e? t?? ap????s? (variance)
  t?? ?ata??µ??

53
?p?????sµ?? t?? RTT

• ??t?µ?s? t?? ap????s?? D (variance)
• ?p??
• ? e??a? t? te?e?ta?? de??µa RTT
• a 7/8
• ?? ?????µet?? ?a?????eta? sa?
• ???ß??µa ?? s?µßa??e? ?ta? t? de??µa ??e? sta?e?
  pe??ss?te?e? ap? µ?a f????
• Karns Algorithm ?a??ta p?? ????? sta?e? p??a?
  t?? µ?a? f???? de? ?p????????ta? st? RTT ? D

54
??a??a?t???? ???p?? ?????e?s?? ?p??e??? ????
S?µf???s??

• ? ap?d?s? t?? a??????µ?? ap?s?µf???s?? t?? TCP
  ßas??eta? se µe???? ßa?µ? st?? a???ße?a t??
  ?????µ?t???.
• ??? ??s??µe t? ????? s??t???t??? (µe????
  ?a??st???s?), t?te ? p??? ?a ?a??ste?e?
  ?pe?ß????? p??? ap??atast?se? t?? ep????????a.
• ??? ??s??µe t? ????? p??? µ????, t?te ?a ????µe
  a??e?aste? epa?aµetad?se??.
• ???e? e?d?se?? t?? TCP ????? ep?p??s?et???
  t??p??? a????e?s?? ap??e???.
• ? ap?st???a?, ?ta? pa?a??ße? n s??e??µe?e?
  epa???e?se?? t?? ?d??? pa??t??, t?te ?p??????e?
  p?? t? pa??t? ??e? ?a?e? ?a? ?e???? epa?aµet?d?s?
  ?a??? ?a? t? µ??a??sµ? ap?s?µf???s?? (?p???e?
  e?s???s? ??a n3).
• ? a??????µ?? ???s?µ?p??e? ep?s?? t? ?????µet??
  sa? ep?p??s?et? d????da asfa?e?a?.

55
TCP se ?s??µata ???t?a

• ???ß??µa ?ta? ? p??? a????e?se? ap??e?a ?p???te?
  ?t? p?????e e? a?t?a? s?µf???s??, ?µ?? se
  as??µata d??t?a ?? ap??e?e? ???? µet?d?s?? e??a?
  s???? fa???µe??!

56
Transactional TCP

• ?? ?p???s??µe p?? ??a? pe??t?? ???e? ap?? ?a
  ??t?se? µ?a p????f???a ap? ??a e??p??et?t?, ?a
  p??e? t?? ap??t?s? ?a? ?a te?e??se? t?? s??des?.
  ?p?s??, ? pe??t?? a?aµ??e? p?? ? ap??t?s? e??a?
  a???p?st? (p.?., µ?a µetaf??? ???µ?t??).
• ?e t? TCP t? p?? p??? se????? ??e???eta? µ?a
  se??? µe e???a µ???µata t? ?p??a a??????? µ?a
  s??des?, a?ta???ss??? p????f???e? ?a? st?
  s????e?a ??e????? t?? s??des?.
• ??t? ? d?ad??as?a de? e??a? ?a????? ap?d?t??? ?a?
  ??e???eta? ??t? p?? ap??.
• ?? UDP ?a ?ta? ?a?? ep????? (ap? p?e????
  ap?d?s??) a??? de? e??a? a???p?st? (de?
  ?p?st????e? e??es? ?a? a?aµet?d?s? sfa?µ?t??)

57
Transactional TCP
TCP
58
T?µata ?p?d?s??

• ???ß??µata ?p?d?s??
• S?µf???s? (ft????? pe??ss?te?a pa??ta ap? ?sa
  µp??e? ?a p?????se? ? d??µ?????t??)
• ?? ?s?????sµ???? p????
• ?.?., gigabit ??aµµ? s??dedeµ??? µe ??p???? a???
  ?/?
• S???????sµ?? (synchronous overloads)
• ??a ?e????? p???a?e? µ?a ???? se??? ap? a??s?d?t?
  p??ß??µata
• ???µ?s? t?? p??t??????? (bandwidth-delay product)
• ?et??se?? ??a t?? ap?d?s? t?? d??t???
• ?e????ste t?? s?et???? pa?aµ?t???? ?a? µet?????
  ?a? p??spa??ste ?a ?ata??ßete t? s?µßa??e?.