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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
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 SI TE 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-w ide VPLSservice using BGP-VPLS in WAN.
VPLS-A
VPLS-A
VPLS-A
VPLS-A
VPLS-A
VPLS-A
VPLS-AMPE5
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-A
VPLS-A
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Summary
I t works w ith existing LDP-VPLS standard
Scalable (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-TreeProtocol
Efficient Interworking ASBR provides dual functionality of PErouter and LDP-BGP interworking
Multiple metro-domains can be interconnected via
single interworking ASBR BGP-VPLS with point-to-multipoint LSP instead ofingress replication for multicast/broadcast unknown
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Thank You !