?????? Broadband Network Technologies

1
??????Broadband Network Technologies

• ???????????????? ?!?????spamning tree?
  802.1w Rapid spamning tree ????

????????? ? ? ??? 935606  
??? 935623   ??? 935626   ???
935629   ??? 935632   ???
935633   ??? 935649   ???
2
????
3
??????(Broadcast)?

• ????Spanning Tree??????
• ?Host ????Broadcast Frame (??ARP Request)?
  Router?,
• Frame???Switch A???Switch A ??Frame
  ??Destination MAC Address ??(BroadcastFFFFFFFF
  FFFF),?????Frame Flood?Segment B??Broadcast
  Frame ??Switch B ?,Switch B???????,Flood?Frame?Seg
  ment A??Broadcast Frame ?????????????????,??Router
  ?????Frame?
• ??Bridge?Switch???????Flood????????Port?,????
  ???????

4
Spanning Tree??????

• Spanning Tree Protocol?????,???????????,?????STP?S
  witch??????????????,????(Block)????????Port,Spanni
  ng Tree??????????,???????????,STP?????????Port????
  ??????????
• ??Spanning Tree????Bridge?Switch?????????,????
  ??????BPDU (Bridge Protocol Data Unit)?Hello
  Message?MulticastFrame???BPDU???,??STP????????????
  ?????????????

5
??????--STP ?????

• ????Root Bridge
• ???????????Bridge ?Switch ????Root
  Bridge,?RootBridge???????????,?????Port?Block????P
  ort??Forwarding??,Root Bridge????????(Root)?
• ?BPDU???????????Bridge ID,?? Bridge
  ???????Bridge ID,Root Bridge??Spanning
  Tree???????Bridge ID?Bridge?Switch?
• Bridge ID??Bridge Priority (2 Bytes)?Bridge
  MAC Address (6 Bytes)???,???802.1D Bridge
  Priority??32768?????,??Switch?Bridge
  Priority?32768 (?????8000),?MAC
  Address?0A0C5123456,??Bridge
  ID?800000A0C5123456?
• Root Bridge ???Port ??Designated
  Port,Designated Port ?????Forwarding???,??Forwardi
  ng???,??Port??????????

6

• Non-Root Bridge????Root Port
• ????Root ?Bridge?Switch??,??????Root
  Port???,Root Port?????Non-Root Bridge??Root
  Bridge??,Root Port???????????(Leaf)????
• Root Port?Non-Root Bridge??Root
  Bridge??Port??????PathCost ?Port,Root
  Port?????Forwarding ???
• Path Cost?????Port????????????Frame?Root
  Bridge???Cost ???Path Cost ???????????,????????Cos
  t ????,IEEE 802.1D ????Path Cost ??????
• ????Port ?????Path Cost ???Root
  Bridge,?????PortPriority?Port????Root Port?

7

• ????????????Designated Port
• ????????(Collision Domain)????Designated
  Port,DesignatedPort????Cost???Root
  Bridge,Designated Port ????Forwarding???,????Segme
  nt?????????????Segment?????????Port ????Path
  Cost,????Bridge ID ???Port ?????Designate Port?

8

• Spanning Tree Protocol???
• ?STP?????Cost?Spanning Tree ?,???Enable???Root
  Port?Designated Port,????Port?????Disable,???????R
  oot Port?Designated Port ????,??????????????????ST
  P ????????????BPDU,????????????,????Spanning
  Tree????????
• ??????????????,???Bridge?????Root
  Bridge??????Hello BPDU,?????Bridge???????????(Max
  Age)????Hello BPDU,?Bridge??????Root
  Bridge?????,???Bridge ?????Bridge
  ?????????,???????????????

9
IEEE 802.1w RSTP?? ??

• ?IEEE???802.1d??????????????????????????????,
  ?????????,?RSTP?????802.1d???????IEEE 802.1w
  RSTP???Cisco?802.1d?????????,?Portfast?Uplinkfast?
  Backbonefast??IEEE 802.1w?????????(??)???????(???)
  ???LAN???????,??????????????-?????,???802.1d??????
  ?????RSTP???802.1d?????,???????????????????????,
  ???802.1d?Forward_Delay?Max_Age???????,???????????
  ????????RSTP??????BPDU??????????????????????????
  ??????,???????????????BPDU?BPDU?????????????????
  ????????????????BPDU,???????????????,?????????????
  ?????

10

• ?RSTP?,?????????????,??????????,?802.1d??????(?
  ????)?????????????802.1w??????????(Topology
  Change Notification,TCN)?802.1d????,?????????????8
  02.1d?,TCN????????,???????????????802.1d
  TCN??????????????????,????????????????????RSTP????
  ?,?????????????TCN???????,??????????????TCN???????
  ,????????????????MAC??? ????,RSTP??????????????
  ????????,???????????????????,RSTP?????????????????
  ?????????????????????????,??????????????,?????????
  ????????????????(Agreement)?????(Proposal)??,?????
  802.1d??,????????-??????????????????,802.1w???????
  ????,???????,802.1w??????802.1d???