1. Requirements for 802.1AD Provider Bridges June 2003 Muneyoshi Suzuki NTT

2. Reference Model Provider Bridged Network PEB PCB CE User Site of user A User Site of user B User Site of user A User Site of user B User Bridged LAN PEB: Provider Edge Bridge PCB: Provider Core Bridge CE: Customer Equipment

3. 1. P-VID Space zProblem: 12bit VID space defined in 802.1Q-1998 is too small for public service zRequirements: yIf a P-VID identifies an User Bridged LAN, 24 bit (16M users) ID space is needed yIf a P-VID identifies an user site, 32 bit (4G sites) ID space is needed zNote: Providers need ID space, so solution does not need to define a single 24-32 bit P-VID format yHierarchical ID space (e.g., a P-VID consists of 2 VIDs) yMAC-in-MAC (e.g., a P-VID consists of single VID and a portion of Provider Edge Bridges MAC address)

4. 2. Maximum Bridge Diameter zProblem: Recommended value of the Maximum Bridge Diameter is 7 (802.1D-1998, 802.1w-2001), but it is too small for public service zThe standards dont address technical background of the value (What happens if it exceeds 7? xSTP does not converge in periodic time?) zRequirements: yThe value should be extended tens for Provider Bridged Network and 10 for User Bridged LAN yDiameter of a Provider Bridged Network should not affect diameter of User Bridged LANs

5. 3. Loop Prevention zProblem: A loop fatally affects a Bridged LAN zIf an user sends broadcast or unknown destination frames to the provider, then the frames are sent to the user sites but back to the provider through a looped path,....... zRequirements: yProvider Bridged Network should deploy a mechanism for loop prevention yUser Bridged LAN should deploy a mechanism for loop prevention yProvider Bridged Network should deploy mechanisms that protect the network from loops caused by users

6. (3.1) Loop Prevention in Provider Bridged Network zIt is providers responsibility to ensure loop-free tree topology for the Provider Bridged Network zThus, the topology is decided by the providers policy and control zTherefore, it is quite unrealistic scenario to change the topology based on user-xSTP zRequirements: yProvider Bridged Network should deploy provider-xSTP for loop prevention yHowever, it is usually limited to the provider and does not need to interwork with user- xSTP

7. zIt is users responsibility to ensure loop-free tree topology for the User Bridged LAN zThis is because, an user can cause a loop whether the provider supports per-user-xSTP or not zHowever, if xSTP is used in an User Bridged LAN and if the provider forwards it transparently, loops can be prevented zThis is because, the provider ensures loop-free topology and a single xSTP instance on a loop can detect and cut it zRequirements: yUser Bridged LAN should deploy user-xSTP for loop prevention yProvider Bridged Network may support per-user-xSTP, otherwise, it must forward user-xSTP BPDUs transparently (3.2) Loop Prevention in User Bridged LAN

8. (3.3) Provider Bridged Network Protection from Loops Caused by Users zIf Provider Bridged Network supports per-user-xSTP, it can be protected from loops caused by users zOnly Provider Edge Bridges need to support it, because a single xSTP instance on a loop can detect and cut it zHowever, this is not perfect solution, but it does not mean Providers dont need protection zRequirements: yProvider Edge Bridges optionally support per-user-xSTP to protect the network yDevelopment of an OAM tool that detects loop through User and Provider Bridge Networks is indispensable

9. 4. Unlearning User Addresses zProblem: If topology of an User Bridged LAN is changed by the user-xSTP, the Provider Bridges must clear related entries in the FDB zHowever, this is needed only if the User Site is multihomed to the Provider Network zRequirements: yProvider Edge Bridges should support per-user-xSTP or a snooping mechanism for it. yQ-in-Q: If topology change is detected, clear related entries in the FDB, then notify that the fact to the other Provider Bridges using Customer Change Notification BPDU to be developed yMAC-in-MAC: If topology change is detected, clear related entries in the FDB

10. 5. Path Tracing zWhen a provider tests a path that forwards frames for an user, the provider verifies consistency of FDBs in the Provider Bridges zProblem: Verification is not easy in Q-in-Q case, because, the Provider Bridged Network uses user MAC addresses which subject to change and are purged from FDBs in 5 minutes zRequirement: An OAM tool for path tracing is indispensable in Q-in-Q case zNote: In MAC-in-MAC case, path tracing is easy, because the Network uses Provider Edge Bridge addresses

11. Summary of Requirements z24-32 bit ID space for P-VID zExtend Maximum Bridge Diameter zProvider-xSTP does not need to interwork with user-xSTP zSupport of per-user-xSTP in Provider Edge Bridges zDevelopment of an OAM tool for loop detection zQ-in-Q case: yDevelopment of unlearn signaling protocol yDevelopment of an OAM tool for path tracing