Simplified PBB-VPLS interworking with MMRP draft-allan-mmrp-for-mac-in-mac-00

Dave Allan, Nigel Bragg, Dinesh MohanJuly 2008

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Problem Statement

> PBBN-VPLS interworking is different…. • It is a VPN of VPNs• Desire to isolate and interconnect active topologies with VPLS

• vs. one large fully transparent overlay

• Number of sites per PE approaching one• Number of sites per PBBN comparatively large• Desire to provide “per-service” multicast containment• Resilient and efficient interconnect is table stakes• Large number of services are aggregated onto any PBBN/VPLS

interface• But are I-tagged

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Objectives

> Simplicity, simplicity, simplicityHOW????1. Peer at the B-component layer vs. I-component layer2. Single pre-provisioned PW mesh for all services carried by the

PBBN1. Operational decoupling of service provisioning when VPLS used for

PBBN transit3. Multicast MAC filtering at ingress to PW mesh for efficiency4. Elimination of requirement for “MAC-withdraw” messaging

• Replace with some form of aggregated MAC invalidation signal/active topology change semaphore

> Resilient interconnect• Including handling severing of a subtending MSTI domain

> Symmetric forwarding

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Observations

> I-component awareness is not required by VPLS• C-MAC flooding and learning maps to well understood B-component

multicast MAC addresses• Appropriate filtering of B-component multicast addresses is sufficient to

isolate services• If I cannot learn about you and you cannot learn about me, we cannot

communicate• Elimination of I-component awareness eliminates need for any signalling

enhancements• Pushes I-component awareness back to the BEBs at the edge

> If a single MSTI domain subtends an individual VPLS VSI, PW “active/standby” status can be used to communicate MSTI state inter MSTP domain and trigger the flush of tables and reset of filters• Aggregated form of “MAC withdraw” more akin to STP “topology change”

BPDU

> 802.1ak MMRP is sufficient to program MAC filtering

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Operational Model

PBBN MSTI PBBN MSTI

1. PBBN selects active uplink

1. PBBN/VPLS locally selects active uplink

2. LDP preferential forwarding status bit selects PW to tie

together active uplinks (independent mode)

Active

ActiveStandby

Standby

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Operational Model

PBBN MSTI PBBN MSTI

3. MMRP registrations for I-SID multicast MAC

program filtering

I-SID 100

I-SID 100

802.1ah OUI I-SID

Well known multicast MACs

24 bits22 bits

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Operational Model

PBBN MSTI PBBN MSTI

4. Far end Change in active uplink signalled by change

of active/standby status

5. Change from active to standby triggers flush of MACs mapped

to that PW, and resets VPLS facing MMRP filtering

6. Change from standby to active triggers generation of VPLS

facing MMRP registration messages

6. Change from standby to active triggers generation of VPLS

facing MMRP registration messages

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Going further, 802.1aq Shortest Path Backbone Bridging

> This is a preliminary view

> SPBB uses (S,G) trees, vs. (*,G) within a spanning tree

> SPBB control plane can overlay VPLS

> MMRP accommodates this with “full participant/application participant” registrations• Send/receive or receive only• Permits H&S style multicast

VPLS

FullParticipantApplication

Participants

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Summary

> MMRP driven multicast filtering at the VPLS PEs eliminates need for I-component awareness• VPLS can be pre-provisioned and decoupled from PBBN

operations• Substantial reduction of state at the VPLS-PEs• Significant adjunct to scalability

> Single subtending PBBN MSTI per VPLS VSI permits preferential forwarding bit to be the synchronization mechanism for learning/flushing and MMRP

> Implementations may co-locate some functions