VPLS Signaling

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    Interdomain LDP-BGP VPLS

    Interworking

    Amit Shukla

    Juniper Networks

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    Background

    Virtual private LAN service (VPLS) glues togetherseveral individual LANs across a packet-sw itchednetwork to appear and function as a single LAN

    There are two standards for VPLS control planethat are deployed today: BGP-based (BGP-VPLS): uses BGP for auto-discovery

    and signaling of PWs (RFC 4761) LDP-based (LDP-VPLS): uses LDP for signaling of PWs(RFC 4762), with discovery via provisioning

    The data plane used by both these standards issame

    Flooding of unknown unicast, learning/aging MACaddresses, etc.

    A key notion in the data plane is of split-horizonforwarding

    MPLS pseudo-wire encapsulation

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    Business Drivers for LDP-BGP VPLSinterworking solution

    To interconnect domains running a

    different VPLS control plane technologies

    To expand LDP-based VPLS service out of

    metro domain to WAN in a scalable andefficient manner.By using BGP-VPLS.

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    Expanding VPLS service using BGP-VPLS

    Why BGP-VPLS in WAN

    ScalableAuto-discovery

    Inter-provider support

    Why LDP-VPLS in Metro Legacy

    Proposed solution requires no changes inMetro network running LDP-VPLS

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    Interconnecting Domains running different VPLS

    control plane technologies (BGP-VPLS and LDP-VPLS)

    Existing inter-AS VPLS options are not

    designed for ASes running different VPLStechnologies (BGP-VPLS and LDP-VPLS) Option-A can be used but doesnt scale.

    It is apparent that interworking function isrequired between BGP-VPLS and LDP-VPLS.

    MPE1

    M-ASBR

    Metro-A

    (LDP-VPLS)

    MPE2LDP-VPLS PW

    VPLS-A

    VPLS-A CPE1

    WAN core

    (BGP-VPLS)

    CPE3

    VPLS-A

    C-ASBR

    BGP-VPLS PWVPLS-A

    MPE3

    VPLS-A

    VPLS-ACPE2

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    Extending the reach of LDP-VPLS metro-domain toWAN via BGP-VPLS to enable region/nation-wideVPLS service

    BGP Session

    LDP Session

    C-ASBR2C-ASBR1

    M-ASBR1M-ASBR2

    WAN

    (BGP-VPLS)

    Metro-B(LDP-VPLS)

    RR

    C-ASBR3

    MPE3

    MPE4

    MPE1

    MPE2

    Metro-A

    (LDP-VPLS)

    MPE5

    M-ASBR3

    MPE6

    Metro-C(LDP-VPLS)

    VPLS-A

    VPLS-A

    VPLS-A

    VPLS-A

    VPLS-A

    VPLS-A

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    Overview of LDP-BGP VPLS interworking

    Interworking operation localized at WAN border-

    router (ASBRs)

    Proposed Interworking mechanism require nochanges in both

    LDP/BGP VPLS control plane specifications (and) Current LDP-VPLS Metro network design

    MPE1

    M-ASBR

    METRO-A

    (LDP-VPLS)

    MPE2

    VPLS-A

    VPLS-A CPE1

    WAN core

    (BGP-VPLS)

    CPE2

    VPLS-A

    C-ASBR

    VPLS-A

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    Control Plane Operation Interworking Autonomous System Border Router

    (interworking ASBR)

    Supports both LDP and BGP VPLS control planes Setup full-mesh of LDP/BGP PWs per interdomain VPLS

    Scalable Only one additional LDP session provisioned per LDP-VPLS

    PE Only one additional PW setup on each LDP-VPLS PE per

    VPLS

    MPE1

    M-ASBR

    METRO-A

    (LDP-VPLS)

    MPE2LDP-VPLS PW

    VPLS-A

    VPLS-A CPE1

    WAN core

    (BGP-VPLS)

    CPE2VPLS-A

    C-ASBR

    BGP-VPLS PW

    VPLS-A

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    How BGP-VPLS view LDP-VPLS

    BGP-VPLS view the LDP-VPLS domain like

    a VPLS site w ith a single CE.

    LDP-VPLS BGP-VPLS

    BGP Site-ID:2

    Advertised BGP

    SignalingRoute

    CPE1

    CPE2

    C-ASBR

    MPE1

    MPE2

    BGP Site-ID:3

    VPLS site

    (Interworking ASBR)

    BGP-VPLS pseudow ire LDP-VPLS pseudow ire

    Metro-ABGP Site-ID:1 WAN

    VPLS-AVPLS-A

    VPLS-A

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    How LDP-VPLS view BGP-VPLS

    LDP-VPLS view the BGP-VPLS domain likea VPLS site w ith a single CE.

    LDP-VPLS BGP-VPLS

    CPE1

    CPE2

    C-ASBR

    MPE1

    MPE2

    VPLS site

    (Interworking ASBR)

    BGP-VPLS pseudow ire LDP-VPLS pseudow ire

    Metro-A WAN

    VPLS-A

    VPLS-A

    VPLS-A

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    Data Plane Operation Fundamental data operations perform on each

    incoming frame on a PW:

    LDP and BGP VPLS PWs terminates on the interworkingASBR

    Common MAC-table maintained to stitch the set of fully-meshed LDP and BGP VPLS pseudowires

    MAC-table populated via learning a source-MAC address

    from incoming frame

    Destination MAC-address lookup to determine destinationpseudowire

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    Mesh Group

    Mesh group concept introduced on aninterworking ASBR

    Groups all the fully meshed PWs of each domain.

    Existing split-horizon forw arding rule applicablefor each mesh group

    Allows forwarding across pseudowires part of a different

    mesh-group. Prohibits forwarding across pseudowires part of a same

    mesh-group.

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    Mesh Groups: Flooding

    Assume CE-1 sends a broadcast ARP request packet. It will be flooded byMPE1, to all PEs in Metro-A domain (including C-ASBR) as its fully-meshed.C-ASBR receives this packet from MPE1 and forwards it to all the

    mesh-groups (PWs) except the one in which packet is received, as aresult packet is forwarded on all PW s part of mesh-group WAN .

    Upon receiving this packet from MPE1, C-ASBR learns the CE-1 Mac-addressvia MPE1 PW. Destination forwarding table on C-ASBR looks like:

    MPE1

    MPE2

    C-ASBR

    CPE1

    CPE2

    LDP-VPLS PW BGP-VLS PW

    M esh-group M etro-A M esh-group W AN

    Floodingpacket flowFrom CE-1

    CE-1

    CE-2

    CE-3

    CE-4

    PW(MPE1)MAC(CE-1)

    Next HopMAC-Addr

    VPLS-A

    VPLS-A

    VPLS-A

    VPLS-A

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    Mesh Groups: Normal Known Unicast

    Here, CE-3 is sending a unicast packet to CE-1 and its assumed thatCE-1s MAC address has been learned on all PEs. CPE1 has learnedCE-1s MAC via C-ASBR so it forwards the packet to C-ASBR.

    C-ASBR forwards this unicast packet on MPE1 PW since both

    incoming and outgoing PWs are in different mesh-groups.

    MPE1

    MPE2

    C-ASBR

    CPE1

    CPE2

    LDP-VPLS PWBGP-VLS PW

    Mesh-group M etro-A M esh-group W AN

    Unicast packet

    CE-1

    CE-2

    CE-3

    CE-4

    VPLS-A

    VPLS-A

    VPLS-A

    VPLS-A

    PW(MPE1)Mac(CE-1)

    Next-hopMac-addr

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    Interconnecting multiple metro domains using a singleinterworking ASBR.

    Each metro domain is mapped to a dedicated mesh group.

    MPE1 M-ASBR1

    METRO-A(LDP-VPLS)

    MPE3

    M-ASBR2

    METRO-B(LDP-VPLS)

    MPE2

    MPE4

    C-ASBR

    CPE3

    CPE1

    CPE2

    WAN(BGP-VPLS)

    LDP-VPLS PW

    BGP-VPLS PW

    LDP-BGP VPLS interworkingusing common-mac table

    VPLS-A

    VPLS-A

    VPLS-A

    VPLS-A

    VPLS-A

    VPLS-A

    VPLS-A

    Mesh Groups Full-mesh Domains

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    Interworking Device With Attached CEs

    MPE1

    M-ASBR

    METRO-A

    (LDP-VPLS)

    MPE2 LDP-VPLS PW

    VPLS-A

    VPLS-A

    CPE1

    WAN

    (BGP-VPLS)

    CPE2

    VPLS-A

    VPLS-A

    C-ASBR

    BGP-VLS PW

    Interworking ASBR can provide PE routerfunctionality at the same time performing the

    LDP-BGP VPLS interworking task.

    VPLS-A

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    MPE1

    M-ASBRMETRO-A

    (LDP-VPLS)

    MPE2 LDP-VPLS PW

    VPLS-A

    VPLS-A

    CPE1

    WAN

    (BGP-VPLS)

    CPE2

    VPLS-A

    VPLS-AC-ASBR

    BGP-VLS PW

    CPE1

    Resiliency

    Interworking ASBR becomes critical for

    inter-domain VPLS service Resiliency becomes critical to complete this

    solution

    Solution is redundancy

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    Background: CE-device resiliency usingBGP-VPLS multihoming

    BGP-VPLS multihoming procedures enables loop-free redundancy to attached CE devices w ithout

    relying on Spanning Tree Protocol (STP).

    CE1

    PE1

    PE3CE3

    PE2

    CE device dual-homed to

    PE devices for redundancy PE4

    CE2

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    Redundancy using BGP-VPLS multihoming

    MPE1

    M-ASBR

    METRO-A

    (LDP-VPLS)

    MPE2 LDP-VPLS PW

    VPLS-A

    VPLS-A

    CPE1

    WAN

    (BGP-VPLS)

    CPE2

    VPLS-A

    VPLS-AC-ASBR1

    BGP-VLS PW

    BGP Site-1

    C-ASBR2

    Existing BGP-VPLS multihoming procedure usedw ith no changes to enable redundancy for LDP-

    VPLS metro.

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    Why use BGP-VPLS multihoming Scalable: Supports multiple metro domains

    Flexible: Precise control over designated forwarder

    Load balancing: Distribution of VPLS customers

    MPE1

    M-ASBR1

    METRO-A

    (LDP-VPLS)

    MPE3 M-ASBR2

    METRO-B

    (LDP-VPLS)

    MPE2

    MP