?eta???? (Switching)

1
?eta???? (Switching)

• ??? s??µat????µe d?ad??t?a

2
?e??????

• ?eta???? ?????µ?t?? (Circuit switching)
• ?eta???? ?a??t?? (Packet switching)
• ?eta???? ????????? ?????µ?t?? (Virtual circuit
  switching)
• ?e?t?????a ?eta??????
• ????? (Switching hardware)
• ATM

3
?eta???? ?????µ?t?? (Circuit switching)

• ? ep????????a µeta?? d?? µe??? ???eta? ef?s??
  ?p???e? f?s??? ?????µa t? ?p??? s??d?e? ap?st???a
  ?a? pa?a??pt?.

4
?eta???? ?a??t?? (Packet switching)

• ? ap?st???a? st???e? pa??ta ?p?te ???e? (????? ?a
  ???e? a? ?p???e? pe??pt?s? ?a ?ata?????? st??
  p?????sµ? t??)
• ???e pa??t? d??µ????e?ta? a?e???t?ta ap?
  p??????µe?a pa??ta.
• Se pe??pt?s? ap??e?a? e??? d??µ?????t?, ta
  ep?µe?a pa??ta ?a ???s?µ?p???s??? e?a??a?t???
  µ???p?t?a.

5
?eta???? ????????? ?????µ?t?? (virtual circuit
switching)

• ? ep????????a µeta?? d?? µe??? ?e???? af?? ß?e?e?
  ?a? p????at??e? µ???p?t? ap? t?? ap?st???a p???
  t?? pa?a??pt?.
• ???e pa??t? d??µ????e?ta? s?µf??a µe t? ped?? VCI
  (virtual circuit identifier)
• ??a ta pa??ta ???s?µ?p????? t? ?d?? µ???p?t?.

6
G?f??e? (Bridges)

• ?? ??f??e? de? e??a? ap?d?t???? ?a? p?a?t????
  t??p?? s??des?? µe????? d??t???. ????
  pe?????sµ???? a???µ?? t?p???? d??t??? µp????? ?a
  s??de???? µe ??f??e?.
• ? a??????µ?? ep???????? d??t??? de? e??a?
  ap?d?t???? ??a µe???a d??t?a.

7
???µ?????s? ?a??t??
???a?a? ???µ?????s?? ???µ?????t? 1
??????sµ?? T??a
A 2
B 1
C 3
D 0
E 1
F 1
G 1
H 1
8
???µ?????s? ?a??t?? µe ???????? ?????µata

• ????µa e??????? ?????µata (permanent virtual
  circuits PVC)

???µ?????t?? 1
T??a ??s?d?? VCI ??s?d?? T??a ???d?? VCI ???d??
2 5 1
???µ?????t?? 3
???µ?????t?? 2
T??a ??s?d?? VCI ??s?d?? T??a ???d?? VCI ???d??
3 9 2
T??a ??s?d?? VCI ??s?d?? T??a ???d?? VCI ???d??
0 7 1
9
???µ?????s? ?a??t?? µe ???????? ?????µata

• ???s????? e??????? ?????µata (switched virtual
  circuits SVC)

???µ?????t?? 1
T??a ??s?d?? VCI ??s?d?? T??a ???d?? VCI ???d??
2 5 1
???µ?????t?? 3
???µ?????t?? 2
T??a ??s?d?? VCI ??s?d?? T??a ???d?? VCI ???d??
3 9 2
T??a ??s?d?? VCI ??s?d?? T??a ???d?? VCI ???d??
0 7 1
10
S?????s? t?? ???t???? ?eta?????
???ß??µa ?eta???? ?a??t?? ???????? ?????µa
???a??d??s? ????pat??? (circuit setup) ?e? ??e???eta? ??e???eta?
??e????se?? (addressing) ???e pa??t? ??e? t?? p???? d?e????s? t?? te????? pa?a??pt? ???e pa??t? ??e? µ??? t? VCI
?at?stas? (state Information) ?? d??µ?????t?? de? ??at??? t?? ?at?stas? G?a ???e s??des? ??e???eta? p????f???a ?at?stas??
???µ?????s? ???e pa??t? d??µ????e?ta? a?e???t?ta ??a ta pa??ta a????????? t? ?d?? µ???p?t?
?p??e?a d??µ?????t? ?aµ?a s???pe?a ??a??pt??ta? ??e? ?? s??d?a???e?? p?? pe????? ap? t? ded?µ??? d??µ?????t?.
????t?ta ?p??es??? (Quality of Service) ??s???? ?????? ef?s?? ?p?????? p????
??e???? S?µf???s?? (Congestion Control) ??s????? ??????? ef?s?? ?p?????? p????
11
????? ?eta????? (switching hardware)

• ??a? ?p?????st?? µe a??et?? ???te? d?epaf??
  (interface) µp??e? ?a ???s?µ?p????e? sa? ?????
  µeta?????.
• ?? p??ß??µa e??a? ?t? ?a e??a? ?e???? a????.

• ?p?????? e?e?d??e?µ??e? s?s?e??? ??a t? p??ß??µa
  t?? µeta????? µe ßas????? st?????
• Throughput,
• ep??tas? ???µa?a? (scalability),
• ??st??

12
????? ?eta?????

• ?? ???e? (e?s?d?? ?a? e??d??) (input, output
  ports) e??????? t?? d?epaf??, ap????e???? pa??ta
  se ?????, ß??s???? t? ???a e??d??, t??????
  a??????µ??? ??a t?? pa???? p???t?ta? ?p??es???,
  ??p.

13
Crossbar switches

• ???e ???a e?s?d?? e??a? s??dedeµ??? µe ???e ???a
  e??d??.
• ??? ? p???p????t?ta µeta????? µpa??e? st? ???a
  e??d??.

14
Crossbar Switch Knockout Algorithm

• ??e? t? d??at?t?ta ?a d??µ?????se? µ???? lltn
  pa??ta ap? t?? ?d?a ???a e??d??.
• ? d?ad??as?a ep?????? t?? l t??e??? pa??t?? p??
  ?a d??µ????????? e??a? ? a??????µ?? knockout.

15
Crossbar Switch Knockout Algorithm

• ?p????e?s? st?? ????? e??d?? (output buffering).
• ??t? µ?a? ????? ? ?p??a ?a d??eta? pa??ta l f????
  p?? ??????a ap ?t? µp??e? ?a ste??e? ???,
  ?p?????? l ????? ?? ?p??e? ?e?t??????? e?a????
  (round robin).

16
?eta???? µe ????????st? ???µ?

• ? µ??µ? p??pe? ?a ?e?t????e? n f???? p?? ??????a
  ap ?t? ?? ??aµµ?? (wide I/O bus).

17
?eta???? µe ??t?d??µ?????s? (Self-Routing
Fabrics)

• ???t?? Banyan
• ?p?te?e?ta? ap? ap???? ??µß??? µeta????? 2 x 2
• Se ???e pa??t? ep??????ta? ep??efa??da
  a?t?d??µ?????s??
• ???e ??µß?? ap?fas??e? p?? ?a d??µ?????se? t?
  pa??t? ap? ??a bit st?? ep??efa??da.
• ?e? ?p?????? s??????se?? e?? ta pa??ta
  d?a???µ????? ?at? a???? a???µ?.
• ????p????t?ta n log2 n

18
?eta???? µe ??t?d??µ?????s? (Self-Routing
Fabrics)

• ???t?? Batcher-Banyan
• ???t?? Banyan t?? ?p???? p????e?ta? ???? d??t??
  t? ?p??? d?a???µ??e? t?? ???e? e??d?? ?at? a????
  a???µ?.

?? ???µat?st?? ??µß?? d??µ??????? t? µe????
d?e????s? st?? p??? ???d?
19
?eta???? ?a??t?? ??? (cells)

• ???t?p? t? ?p??? p????e?ta? ap? t? ß??µ??a??a
  t??ef???a?.
• ?e???????a ßas?sµ??? st? µeta???? e????????
  ?????µ?t??.
• ??a ta pa??ta (cells) ????? t? ?d?? µ??e??? (53
  bytes)
• ????? pa??ta ep?t??p??? ?a??te?? ??e??? st??
  ?????.
• ?a??ta ?d??? µe?????? ap??p????? t?? d?a?e???s?
  t?? pa??t??.
• ?p?t??p??? t?? µeta???? µ?s? ?????? (a?t?
  ????sµ????).
• ?p?t??p??? t?? pa??????? d?a?e???s? p???ap???
  pa??t??.

20
?? ?a??t? ATM (ATM Cell)

• User-Network Interface (UNI)
• GFC Generic Flow Control (still being defined)
• VCI Virtual Circuit Identifier
• VPI Virtual Path Identifier
• Type management, congestion control, AAL5
  (later)
• CLP Cell Loss Priority
• HEC Header Error Check (CRC-8)
• Network-Network Interface (NNI)
• switch-to-switch format
• GFC becomes part of VPI field

21
?eµa??sµ?? ?a? ?pa?as?????t?s? (Segmentation and
Reassembly)

• Sta d??t?a ATM ?p???e? t? st??µa ???sa?µ???? p??
  e??a? ?pe????? ??a t? teµa??sµ? ?a?
  epa?as?????t?s? µ???d?? ded?µ????. (???
  Adaptation Layer (AAL))
• AAL 1 ?a? 2 e??a? s?ed?asµ??e? ??a efa?µ???? p??
  ??e?????ta? e????se?? p???t?ta? (p.?., f??? ?a?
  video))
• AAL 3/4 e??a? s?ed?asµ??e? ??a ded?µ??a (packet
  data)
• AAL 5 ???a? e?a??a?t??? t?? AAL 3/4.

22
?a??t? st? ?p?st??µa AAL 3/4 (Convergence
Sublayer Protocol Data Unit (CS-PDU))

• CPI Commerce part indicator (version field)
• Btag/Etag Beginning and Ending tag
• BAsize ??t?µ?s? t?? a?a??a?a? µ??µ??
• Length ?? µ??e??? ???? t?? pa??t??

AAL 3/4 Header
23
ALL 3/4 Cell Format

• Type
• BOM (10) beginning of message
• COM (00) continuation of message
• EOM (01) end of message
• SEQ sequence of number
• MID multiplexing identifier
• Length number of bytes of PDU in this cell