tpa DLC

1
???t?pa DLC
HDLC (ISO), ADCCP (ANSI), LAPB (CCITT), SDLC
(IBM). ??µ? p?a?s??? Address ??a
s??desµ??? p???ap??? p??sp??as??. HDLC
High-level Data Link Control ISO International
Standards Organization ADCCP Advanced Data
Communications Control Procedure ANSI American
National Standards Institute LAPB Link Access
Procedure, Balanced CCITT Consultative
Committee for International Telephony and
Telegraphy SDLC Synchronous Data Link Control

2

• Format byte e??????
• ??d? ep?pt???? p?a?s???
• RR Receive Ready (?t??µ?? ??a ???? normal
  ACK).
• RNR Receive Not Ready (?CK a??? de ??t?e? ???a
  ded?µ??a).
• REJ Reject (??t? NAK).
• Selective reject (??a p??t??e?? ep??e?t???
  epa?a??pt??? ARQ).

?a p?a?s?a p????f???a? ???s?µ?p????? ?p?s??????s?
?at? n (mod B).
?a ep?pt??? p?a?s?a st?????? ACKs (RN) ?????
ded?µ??a.
?? a???µ?µ??a p?a?s?a (??a a?????p???s?,
te?µat?sµ? ?a? ???e? e?d???? e?t????).

• P/F (poll/final) bit
• P1 (??t?e? ap????s?)
• F1 (d??e? ap??t?s?)

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?at?stas? ?a??????? ap????s?? Normal Response
Mode (NRM)
Station A
Station B

• ? ? a?????p??e? t? s??desµ? p??? t? ?.
• ? ? ap?d??eta?.
• ? ? a?????p??e? t? s??desµ? p??? t?? C.
• ? ? pe??µ??e? p??? ?a? ?a?ap??spa?e?.
• ? C ap?d??eta?.
• ? ? st???e? st?? ?.
• ? ? staµat?e? ?a st???e? st?? ? ?a? t?? ??t?e?
  ap? t?? ? ?a ste??e?.
• ? ? st???e? st?? ?.
• ? ? st???e? t? te?e?ta?? p?a?s??.
• ? ? ??t?e? ap? t?? C ?a t?? ste??e?.
• ? C st???e? µ??? ??a p?a?s??.
• O ? ?p?s?????e? ?a? ?a?ast???e? st?? ?.
• ? ? ?p?s?????e?.
• ? ? st???e? ??a ded?µ??a st? te?e?ta?? p?a?s??.

SETM Set mode (NRM) UA Unnumbered
acknowledgement (µ? a???µ?µ??? ACK)
4
?s????p?µ??? as??????? ?at?stas? Asynchronous
Balanced Mode (ABM)
Station A
Station B

• ? ? a?????p??e? t? s??desµ? p??? t? ?.
• ? ? ap?d??eta? sa? de?te?e???.
• ? ? a????e? ?a st??e?? st?? ?.
• ? ? ?aµß??e? s?µa UA ?a? a????e? ?a st??e?? st??
  ?.
• ? ? ??t?e? epa??????.
• ? ? ?p?s?????e?.
• S??e?????? ?a? ?? d?? ?a st??????.
• ? ? ep?ßeßa???e? ta ded?µ??a p?? ??aße µe ACK.
• O B ep?ßeßa???e? ??a ta ded?µ??a p?? ??aße ap?
  t?? ?.
• ? ? ???st?p??e? st?? ? ?t? de? ???e? ???a
  ded?µ??a.
• ? ? ep?ßeßa???e? t? ???st?p???s?.
• ? ? ap?s??d?eta? ap? t?? ?.
• ? ? ep??????e? t?? ap?s??des?.

SETM Set mode (ABM)
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???t?????? a?????p???s?? ?a? ap?s??des??
? µet?d?s? ded?µ???? ???eta? µ??? st?? p???
pe???d??? (up periods).
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???t?????? ?s????p?µ???? (balanced)
a?????p???s?? ?a? ap?s??des??

• ?? ??µµ?t? t?? a?????p???s?? ???eta? t??p??
  ?e??a??a (three-way handshake).

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T?µata d?e????s??d?t?s?? st? ep?ped? d??t???
? d?e????s??d?t?s? de? ???eta? st?? DLC (e?t??
ap? t?? pe??pt?s? p???ap??? p??sp??as??).
Sta datagram d??t?a ???e pa??t? pe????e?
p????f???e? s?et???? µe t?? p??? ?a? t??
p?????sµ? t??. ??e????t?µa e?e????a st?
d??µ?????s?. ?e?????t?µa ??e???eta? epa?ad??ta??
t?? pa??t?? sta ?????te?a ep?peda.
8

9
Sta e??????? ?????µata, µ??? ta ?????µata
(circuits) se ???e s??desµ? p??pe? ?a
d?a???????ta? µe t?? d?e????s??d?t?s?.
?a pa??ta pe??????? ap?? ??a? ta?t?p???t?
e???????? ?????µat?? (virtual circuit identifier
VCI).
10

11

12
?? ?.25 p??t?p? ep?ped? d??t??? (CCITT)

• ?p??efa??da pa??t?? ded?µ????
• ?a ped?a SN ?a? RN µp????? ?a epe?ta???? ?a? se 7
  bits (modulus 128).
• C 0 ??a pa??ta ded?µ???? ?a? 1 ??a pa??ta
  e??????.
• ? 0 ??a t? te?e?ta?? pa??t? t?? µ???µat?? ?a? 1
  a?????.
• Modulus 01 ??a mod 8 ?a? 10 ??a mod 128.
• D 0 s?µa??e? ap? ???? se ???? (end to end) ?CK
  ?a? 1 s?µa??e? t?p??? ACK.
• Q 1 ??a ??e??? ?????te??? ep?p?d??.
• ?a SN ?a? RN a???µ??? ta pa??ta µ?a?
  s???e???µ???? s??d????e??? (session).

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T??ef????? d??t??
1920s A a?a??????? s??desµ??
ep????????a?. ? µeta???? (switching) ????ta?
?e????a?t???. 1988 To f???t??? d??t?? e??a?
p???? ??a ??f?a?? d??t?? p?? p??spe?a??eta? ap?
t?p??? a?a?????? loops. A a?a???????
s??desµ?? ep????????a?. D ??f?a??? s??desµ??
ep????????a?. ? µeta???? ???eta? ??e?t??????.
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ISDN
?? t??ef?????? eta???e? ep???µ??? ?a ??????
???????? t? f???t??? d??t?? ??f?a?? (d??. ?a
??f??p???s??? ta a?a?????? local loops). ??a
t?t??? d??t?? ???eta? INTEGRATED SERVICES DIGITAL
NETWORK (ISDN). ???eta? integrated ???? t??
??a??t?ta? e?s?µ?t?s?? f???? ?a? ded?µ???? (?a?
p??a??tata ?a? ????? efa?µ????). F??? ? 64
?bps ?????ep?d?ast??? ?????f???a ? ????te?? ap?
104 bits a?? µ???µa (login, ATM
t?ape???) ?????a ? pe??p?? 107 µe 109 bits a??
µ???µa Video ? 105 µe 108 bps flow ?etaf???
a??e??? ? gt105 bits a?? µ???µa
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??p??? p??sßas? st? ISDN

• ?a local loops p??sßas?? e??a? ??????
  s??est?aµ??a ?e??? (twisted pairs) ?a? ap?te????
  t? ½ t?? s???????? ep??d?s?? t?? t??ef??????
  d??t???.
• To s??est?aµ??? ?e???? pa?aµ??e?, a???
  ???s?µ?p??e?ta? ??a ??f?a?? µet?d?s? µ????
  192Kbps
• ??t? ep?t??pe? t?? ?pa??? d?? 64Kbps ?a?a???? (?
  ?a????a), e??? 16Kbps ?a?a???? (D ?a????), s??
  ??p??? overhead.
• ???? ?? ???ste? p??spe?a????? t? ?a???? D µe
  a?ta????st??? t??p?.
• ???e ? ?a???? e??a? s??dedeµ??? µe t? p??? ??a
  ???st? ???e f???
• D ?a???? (16Kbps) ???s?µ?p??e?ta? ??a t??
  e??at?stas? ???se?? ??a ? ?a????a ?a? ?? d??t??
  µeta????? pa??t?? ??a a????ep?d?ast???? efa?µ????
  ?aµ???? ???µ?? µet?d?s??.
• ? ?a???? (64Kbps) ?a???? µeta????? ?????µat??
  ??a f??? ? ded?µ??a.
• ???te???sa ?p??es?a primary service (µe?????
  ???ste?) 24 64Kbps 1.5Mbps ? 31 64Kbps
  1.96 Mbps

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A????ep?d?ast??? ?????f???a (interactive
traffic)
? a????ep?d?ast??? ?????f???a µeta?? te?µat????
?a? ?p?????st? p??a??tata µe???eta? ???? t?? PCs
?a? t?? sta?µ?? e??as?a?. ?ts? ? pe??ss?te??
s?µßat??? a????ep?d?ast??? ?????f???a ?a
p?????eta? ap? a????p??e?e?? s??a??a??? ?p?? ATM,
??e?t??????? pa?a??e??e? ?.t.?. p.?. ??
?p???s??µe ?t? ???e ?t?µ? se µ?a p??? ???e?
s??a??a?? ded?µ???? µe ???µ? 5 s??a??a??? t??
??a. ???e s??a??a?? d?µ?????e? ??a pa??t? 1000
bits ?a? ?p?????? 106 ??t????? st?? p???. ?ts?
????µe s??????? ?????f???a 5 109 bits a?? ??a
t? ?p??? e??a? ????te?? ap? 1.5?bps. To
s?µp??asµa e??a? ?t? ? a????ep?d?ast???
?????f???a ?a e??a? ??a as?µa?t? (se ????) ???sµa
t?? ?????f???a? se µe????t??? d??t?a.
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F???

• ? s???????? ????? t?? ?????f???a? f???t????
  ded?µ???? ep?s??a?e µ???? p??sfata a?t? t?? ap???
  ded?µ????.
• ? ?????f???a ded?µ???? a????eta? p?? ??????a.
• ? ?????f???a f???t???? ded?µ???? ?a e??a?
  ????a??? st? ISDN ??a t? p??se??? µ?????, a??? t?
  video µp??e? ?a e??a? ????a??? st? B-ISDN.

?etaf??? a??e??? ?a? e????a?

• ??a? s??desµ?? 1.5Mbps µetaf??e? pe??p?? 75
  t?p?µ??e? se??de? a?? de?te???ept?. H Britannica
  ??e???eta? 20 ?ept?.
• ??a? s??desµ?? 1.5Mbps µetaf??e? µ?a e????a
  ??af???? ?????? a????s?? µe?????? 109 bits µ?sa
  se 11 ?ept?.
• ?a??? ? µet?d?s? ded?µ???? ???eta? ???????te??
  ?a? f????te?? ?p???e? t?s? ?a st?????ta? p????
  pe??ss?te?a ded?µ??a ap? ?sa ??e?????ta? (p.?.
  ap?st??? ?e?µ???? ?? e????a a?t? ?a a??s????µe
  ??a s?µßat?t?ta epe?e??as?a? ?e?µ????).

Video

• 0.1 100?bps ?a ?fe?????? saf?? ap? ?????te????
  ???µ??? µet?d?s??.

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?e?????sµ?? t?? ISDN
To p?e????t?µa t?? ISDN se s??s? µe ta ?p?????ta
d??t?a pa??t?? e??a? ? ?a??te?? µetaf??? a??e???
(s?? ??a a?ta????st??? p?e????t?µa st??
t??ef?????? eta???e?). ? µetaf??? µe?????
a??e??? ?a? e?????? de? e??a? a??µa ??a??p???t???
??????? (µ?a e????a ??af???? ?????? a????s??
µe?????? 109 bits ??e???eta? p??? ap? 4 ??e?
sta 64?bps, 11 ?ept? sta 1.5Mbps).
ISDN e??e?a? ????? (B-ISDN)

• ?a s?st?µata Broadband ISDN s?ed?????ta? µe
  t?p??? p??sßas? ?pt???? ??a? 155Mbps.
• ??a?µat??? ?????? ???µ?? µetaf???? a??e???.
• ???te?d?as???e??.
• HDTV µe ??t?s?.
• ?????ep?d?as? µe LANs ?????? ta??t?t??.
• ?????? d??at?? efa?µ???? e????a? ß??te?.
• ? ????t???t?ta t?? ?pt???? ???? (1014bps) ???e?
  t? B-ISDN f?s??? st??? p??? ep?te???.

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??? (Asynchronous Transfer Mode)

• ?? ATM e??a? ??a p??t?????? µeta????? pa??t?? ??a
  
• B-ISDN d??t?a.
• ?a pa??ta ??? ?a????ta? ?e??? (cells) ?a? ?????
  sta?e??
• µ???? (53 bytes 5 bytes ep??efa??da 48 bytes
  ded?µ????).
• ????? ep?????? t?? p??t?p?? a?t??
• ?p??e? ?a a?tape????e? se e????t??? (bursty)
  ?????f???a.
• ?p??e? ?a pa???e? p???????? ???µ??? µet?d?s??.
• ?a pa??ta f???t???? ded?µ???? p??pe? ?a e??a?
  µ???? (lt1000bits) ??a ?a e??a? µ????? ??
  ?a??ste??se?? st?? pa?a???? t?? pa??t??
  (packetization delay).
• ?eta???e?? p??? ?????? ta??t?t?? e??a? e?????te??
  ?a ft?a?t??? ??a pa??ta sta?e??? µ?????.

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Format ep??efa??da? ???
?? ped?? flow control (e?????? ????)
???s?µ?p??e?ta? ??a ?a ß????se? t? ???st? ?a
p???p???e? d?af??et???? efa?µ???? ?a? ??? ??a ?a
ß????se? st?? pe??pt?s? s?µf???s?? st? d??t??. ?
d?e????s? (address) e??a? ??s?ast??? ?d?a µe
t?? a???µ? e???????? ?????µat??. ?????e? ??a ???e
s??desµ? ?a? ta?t?p??e? t? s??d???e?? µ?sa st?
s????? t?? s??d?a???e?? p?? ???s?µ?p????? t?
s???e???µ??? s??desµ?. ? d?e????s? d?aµe???eta?
sta ped?a VCI ?a? VPI. ?? s??d?a???e?? p??
a????????? t? ?d?? µ???p?t? ??a a??et??? ??µß???
µp????? ?a ????? t? ?d?? VPI. ???sµ????
µeta???e?? ???t??e µ??? t? VPI ap??p????ta? ?ts?
t?? p???p????t?ta µeta?????. Ge???t???
p??????µ? g(x) x8 x2 x 1
21
? ???s? t?? CRC e??a? ???? as?????st? ed? ??e?
t? s?µßat??? d?µ? e??? p??t??e???? p??????µ?? ep?
(x 1) ?a? ??a ??e? e????st? ap?stas? 4. ?????e?
µ??? t?? ep??efa??da ???e ?e???? ?a? e?a???sseta?
µeta?? d?? ?atast?se??. ?p???e? µ??? ??a bit
st?? ep??efa??da, t? bit p??te?a??t?ta? (priority
bit), ??a ??e??? ????. ??t? µp??e? ?a t? ??se? ?
???st?? ??a ?a ?p?de??e? ?e??? ?aµ????
p??te?a??t?ta? ta ?p??a µp????? ?a ?a???? ap? t?
d??t?? se pe??pt?s? s?µf???s??. ??t? t? bit
µp??e? ep?s?? ?a te?e? ap? t? d??t?? ??a ?a
?p?de??e? ??a? ???st? p?? pa?aß???e? t? s?µf???a
???µ?? ded?µ???? a?t??. ?a? p??? t? cell µp??e?
?a e??ata?e?f?e? se pe??pt?s? s?µf???s??. ?? bit
p??te?a??t?ta? e??a? p??a??? a?epa???? ??a t??
ep???s? t?? p??ß??µat?? s?µf???s??.
22
??? ep?ped? ???sa?µ???? (??? Adaptation Layer
AAL)
Ta????µ?s? ?p??es??? ??a t? AAL
23
A?L t?p?? 3/4
g(x) x10 x9 x5 x4 x 1 LI Length
Indicator (e?de??t?? µ?????) ??D Multiplexing
Identifier (ta?t?p???t?? p???p?e??a?) PDU
Protocol Data Unit (µ???da ded?µ????
p??t???????) SAR Segmentation And Reassembly
(tµ?µat?p???s? ?a? epa?as??a?µ?????s?) ST
Segment Type (t?p?? tµ?µat??)
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Datagram ?????f???a p?? ???s?µ?p??e? ATM d??t??

• ? datagram ?????f???a d??µ????e?ta?
  ???s?µ?p????ta? µ???µa e??????? ?????µata µeta??
  datagram µeta?????.