Bridges

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Bridges
2
G?f??e? (bridges)

• ?e?t??????? st? de?te?? ep?ped?
• ???s?µ?p?????ta? ??a
• ?? d?as??des? t?p???? d??t??? t?? ?d?a? ?
  d?af??et???? te???????a?
• ??? pe?????sµ? t?? pa??t??
• ?? d?as??des? ?e???af??? ap?µa???sµ???? t?p????
  d??t???

3
??????s? ß?s? MAC d?e????se??
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MAC Relay Entity
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??d? Gef????

• Transparent Basic
• ???a?? ?a??te?? ap? epa?a??pt?
• Source Routing
• ?as??eta? se p????f???a p?? pe????eta? st?
  e?se???µe?? frame ??a ?a p?????se? t? pa??t?
• Transparent Learning
• ?a?a??e? ap? ???e frame ap? p??? interface ???e
  ?a? ???s?µ?p??e? t?? p????f???a st? µ?????
• Transparent Spanning Tree (IEEE 802.1)
• ?atas?e???e? ??a ?p?s????? t?? d??t??? ??a ?a
  ap?f??e? t??? ß???????

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Transparent Learning Bridge

• ? epe?e??ast?? e?et??e? t? d?e????s? ap?st???a
  ?a? pa?a??pt? se ???e frame ap? ???e port
  (interface)

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???a??? pe??pt?se?? ??a t?? ap?fas? p?????s? t??
frame

• ?e? ??????e? ?a???a?
• G?????e? t?? ap?st???a
• G?????e? t?? pa?a??pt?
• ???? ???e? ?????
• Se ???e pe??pt?s? de? e?p?µpe? t? frame p?s? st?
  d??t?? ap? t? ?p??? p?????e.

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F??t????sµa ????s??

• ??a pa??t? e?p?µpeta? ap? t?? ? ??a ???e ??a? ap?
  t??? ?????? ?p?????st??

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? ?????? µ?a? learning bridge
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Looping
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?????????a ?e????t?? p?? ?d????? se looping

• Event
• 1 ABC sends packet onto LAN 1, received on ports
  a, b, c at bridges
• 2 Bridge 3 sends packet onto LAN 2
• 3. Bridge 1 sends packet onto LAN 2
• 4. Bridge 1 sends packet onto LAN 1

• Result
• Bridges note ABC is on LAN 1 and,
• Queue packet on ports d, e, f for LAN 2
• 2. Bridges 1 and 2 note ABC is on LAN 2 and,
  queue packet on ports a and b for LAN 1
• 3. Bridge 2 ABC still on LAN 2
• Bridge 3 ABC has moved to LAN 2
• Queue packet on ports b and C for LAN 1
• 4. Bridge 2 ABC moved to LAN 1
• Bridge 3 ABC moved to LAN 1
• Queue packet on ports e and f for LAN 2

12

• G?a ?a ap?f??? t? looping ?atafe??? se te??????
  d?µ??????a? t?? spanning tree t?? d??t???.

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Blocking

• ?? ap?? apa???e?s? se µ?a ??f??a ?a st???e?
  pa??ta p?s? st? d??t?? ap? t? ?p??? t?? ???a?,
  t?te µp??e? ?a ?d????? se apa???e?s? ep????????a?
  p?? e??a? ???st? ?? blocking.

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??ad??t??s? t?p???? d??t??? d?af??et????
te???????a?

• ? ???st?? ??e? t?? ?p??es?a p?? p??sd?????eta?
  ap? t? ?aµ???te?? p???t?ta ?p??es?a? t?? d??t???
  p?? ???s?µ?p??e?

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???ß??µata p?? p??pe? ?a a?t?µet?p?st??? ap? t?
??f??a

• ??af??et???? µ??f?? d?e????se??
• little indian vs big indian
• ??af??et??? µ??f? Frame
• status bits?
• ??af??et??? µ??e??? Frames
• 1518 vs 4416
• ??af??et???? ta??t?te? (a????? ??a buffer)
• ??a?e???s? frame
• ap????f?s? st??? te?µat?sµ??? ? ap?s??s?
• ??af??et???? t??p?? p??sßas?? st? µ?s?
• CSMA/CD e?a?t??? TOKEN

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Remote bridges
???µ????ta? ?a? half-bridges ??at? ?e?t???????
sa? µ?a