Interdomain LDP-BGP VPLS Interworking

Amit ShuklaJuniper Networks

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BackgroundVirtual private LAN service (VPLS) glues together several individual LANs across a packet-switched network to appear and function as a single LANThere are two standards for VPLS control plane that 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 provisioningThe data plane used by both these standards is same• Flooding of unknown unicast, learning/aging MAC

addresses, etc.• A key notion in the data plane is of split-horizon

forwarding• MPLS pseudo-wire encapsulation

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Business Drivers for LDP-BGP VPLS interworking 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 and efficient manner.•By using BGP-VPLS.

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Expanding VPLS service using BGP-VPLS

Why BGP-VPLS in WAN•Scalable•Auto-discovery• Inter-provider support

Why LDP-VPLS in Metro• Legacy

Proposed solution requires no changes in Metro 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 VPLS technologies (BGP-VPLS and LDP-VPLS)• Option-A can be used but doesn’t scale.

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

MPE1M-ASBR

Metro-A(LDP-VPLS)

MPE2LDP-VPLS PW

VPLS-A

VPLS-A CPE1

WAN core(BGP-VPLS)

CPE3VPLS-A

C-ASBR

BGP-VPLS PWVPLS-A

MPE3

VPLS-A

VPLS-ACPE2

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

BGP Session

LDP Session

C-ASBR2 C-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-AVPLS-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 no changes in both• LDP/BGP VPLS control plane specifications (and)• Current LDP-VPLS Metro network design

MPE1M-ASBR

METRO-A(LDP-VPLS)

MPE2VPLS-A

VPLS-A CPE1

WAN core(BGP-VPLS)

CPE2VPLS-A

C-ASBR

VPLS-AInterworking device

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Control Plane OperationInterworking 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

MPE1M-ASBR

METRO-A(LDP-VPLS)

MPE2LDP-VPLS PW

VPLS-A

VPLS-A CPE1

WAN core(BGP-VPLS)

CPE2 VPLS-A

C-ASBR

BGP-VPLS PW

VPLS-ALDP + BGP Control planes

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How BGP-VPLS view LDP-VPLSBGP-VPLS view the LDP-VPLS domain like a VPLS site with a single CE.

LDP-VPLS BGP-VPLS

BGP Site-ID:2

Advertised BGPSignaling Route

CPE1

CPE2

C-ASBR

MPE1

MPE2

<Local-site:1, Offset:1, Label-base:800>

BGP Site-ID:3

VPLS site

(Interworking ASBR)

BGP-VPLS pseudowire LDP-VPLS pseudowire

Metro-ABGP Site-ID:1 WAN

VPLS-AVPLS-A

VPLS-A VPLS-A

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How LDP-VPLS view BGP-VPLS

LDP-VPLS view the BGP-VPLS domain like a VPLS site with a single CE.

LDP-VPLS BGP-VPLS

CPE1

CPE2

C-ASBR

MPE1

MPE2

VPLS site

(Interworking ASBR)

BGP-VPLS pseudowire LDP-VPLS pseudowire

Metro-A WAN

VPLS-A

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 interworking ASBR

• 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 destination pseudowire

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Mesh Group Mesh group concept introduced on an interworking ASBR

• Groups all the fully meshed PWs of each domain.

Existing split-horizon forwarding rule applicable for 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 by MPE1, to all PEs in “Metro-A” domain (including C-ASBR) as it’s 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 a result packet is forwarded on all PWs part of mesh-group “WAN”.Upon receiving this packet from MPE1, C-ASBR learns the CE-1 Mac-address via MPE1 PW. Destination forwarding table on C-ASBR looks like:

MPE1

MPE2

C-ASBR

CPE1

CPE2LDP-VPLS PW BGP-VLS PW

Mesh-group “Metro-A” Mesh-group “WAN”

Flooding packet flowFrom CE-1

CE-1

CE-2

CE-3

CE-4

MAC-Addr Next HopMAC(CE-1) PW(MPE1)

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 it’s assumed that CE-1’s MAC address has been learned on all PEs. CPE1 has learned CE-1’s 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-ASBRCPE1

CPE2

LDP-VPLS PWBGP-VLS PW

Mesh-group “Metro-A” Mesh-group “WAN”

Unicast packet

CE-1

CE-2

CE-3

CE-4

VPLS-A

VPLS-A

VPLS-A

VPLS-A

Mac-addr Next-hopMac(CE-1) PW(MPE1)

Forwarding Table

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Interconnecting multiple metro domains using a single interworking 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 PWBGP-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-ASBRMETRO-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

C-ASBR has three mesh groups: one for BGP in the WAN; one for Metro-A; and

finally, one for its attached CE(s)

Interworking ASBR can provide PE router functionality at the same time performing the LDP-BGP VPLS interworking task.

PE + LDP-BGP Interworking Task

VPLS-A

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MPE1M-ASBR

METRO-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 serviceResiliency becomes critical to complete this solution•Solution is redundancy

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Background: CE-device resiliency using BGP-VPLS multihoming

BGP-VPLS multihoming procedures enables loop-free redundancy to attached CE devices without relying on Spanning Tree Protocol (STP).

CE1

PE1

PE3 CE3PE2

CE device dual-homed toPE devices for redundancy

PE4

CE2

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Redundancy using BGP-VPLS multihoming

MPE1M-ASBR

METRO-A(LDP-VPLS)

MPE2 LDP-VPLS PW

VPLS-A

VPLS-A

CPE1WAN

(BGP-VPLS)

CPE2

VPLS-A

VPLS-AC-ASBR1

BGP-VLS PW

BGP Site-1

C-ASBR2

Two points of interworking for

redundancy

Existing BGP-VPLS multihoming procedure used with 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

MPE4

C-ASBR1

WAN(BGP-VPLS)

LDP-VPLS PW

BGP-VPLS PW

C-ASBR2VPLS-A

VPLS-A

VPLS-A

VPLS-A

BGP SITE 1

BGP SITE 2

Resiliency for multiple LDP-VPLS Metros

VPLS-A

VPLS-A

CPE1

CPE2

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Extending the reach of LDP-VPLS metro-domain to WAN via BGP-VPLS

BGP Session

LDP Session

C-ASBR2 C-ASBR1

M-ASBR1

M-ASBR2

WAN(BGP-VPLS)

Metro-B(LDP-VPLS)

RR

C-ASBR3

MPE1

MPE2

MPE3

MPE4

Metro-A(LDP-VPLS)

Interdomain LDP-BGPinterworking

Interdomain LDP-BGPinterworking

MPE6

M-ASBR3

MPE7

Metro-C(LDP-VPLS)

Scalable way to enable region/nation-wide VPLS service using BGP-VPLS in WAN.

VPLS-A

VPLS-A

VPLS-A

VPLS-A

VPLS-A

VPLS-AVPLS-A

MPE5

Interdomain LDP-BGPinterworking

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Resiliency using BGP-VPLS multi-homing

BGP Session

LDP Session

C-ASBR2

C-ASBR1

M-ASBR1

M-ASBR2

WAN(BGP-VPLS)

Metro-B(LDP-VPLS)

RR

C-ASBR3

MPE1

MPE2

MPE3

MPE4

Metro-A(LDP-VPLS)

Redundant InterworkingASBRs

MPE5

M-ASBR3

MPE6

Metro-C(LDP-VPLS)

C-ASBR3

Enabling resiliency for LDP-VPLS domain “Metro-B”

VPLS-A

VPLS-A

VPLS-AVPLS-A

VPLS-AVPLS-A

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Efficient flooding and broadcasting using P2MP LSP in WAN running BGP-VPLS control plane

Traffic forwarded using ingress replication

Traffic forwarded over P2MP LSP

C-ASBR2

C-ASBR1M-ASBR2

WAN(BGP-VPLS)

RR

C-ASBR3

MPE3

MPE4

Metro-A(LDP-VPLS)

MPE5

M-ASBR3

MPE6

Metro-C(LDP-VPLS)

P

BGP-VPLS in WAN usingP2MP LSP for flooding

LDP-VPLS domain using Ingress replication

LDP-VPLS domain usingIngress Replication

Path of multicast traffic originating from site A3

Multicast frame getting

Forwarded over P2MP LSP

VPLS-A

VPLS-A

VPLS-AVPLS-A

VPLS-A

VPLS-A

Metro-B(LDP-VPLS)

M-ASBR1

MPE3

MPE4

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Summary

It works with existing LDP-VPLS standardScalable (and minor changes to metro design)• Only one (or couple) additional LDP sessions per PE in

metro• Only one (or couple) additional PWs setup per PE per

VPLS

Easier to manage • Adding new sites or PE in a metro area does not require

any provisioning on other remote Metro area• BGP auto-discovery simplifies provisioning task in WAN

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Summary (Cont…)

Resilient• Native BGP-VPLS multi-homing support provides loop-

free redundancy without the need of Spanning-Tree Protocol

Efficient• Interworking ASBR provides dual functionality of PE

router and LDP-BGP interworking• Multiple metro-domains can be interconnected via

single interworking ASBR• BGP-VPLS with point-to-multipoint LSP instead of

ingress replication for multicast/broadcast unknown

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Thank You !