Virtual Private LAN Services
7750 SR OS Services Guide Page 493
• C, a Control word MUST or MUST NOT be present when sending VPLS packets to this
PE, depending on whether C is 1 or 0, respectively. By default, Alcatel-Lucent
implementation uses value 0.
• MBZ, Must Be Zero bits, set to zero when sending and ignored when receiving.
• D indicates the status of the whole VPLS instance (VSI); D=0 if Admin & Operational
status are up, D=1 otherwise.
Here are the events that set the D-bit to 1 to indicate VSI down status in BGP update message sent
out from a PE:
• local VSI is shutdown administratively using the “config service vpls shutdown”
• all the related endpoints (SAPs or LDP pseudowires) are down
• There are no related endpoints (SAPs or LDP pseudowires) configured yet in the VSI
→ The idea is to save the core bandwidth by not establishing the BGP pseudowires to an
empty VSI
• Upon reception of a BGP Update message with D-bit set to 1 all the receiving VPLS PEs
must mark related pseudowires as down.
The following events do not set the D-bit to 1
• local VSI is deleted - a BGP Update with unreach-NLRI is sent out. Upon reception all
remote VPLS PEs must remove the related pseudowires and BGP routes.
• if the local SDP goes down, only the BGP pseudowire(s) mapped to that SDP goes down.
There is no BGP-update sent.
Supported VPLS Features
BGP VPLS just added support for a new type of pseudowire signaling based on MP-BGP. It is
based on the existing VPLS instance hence it inherited all the existing Ethernet switching
functions. Here are some of the most important existing VPLS features ported also to BGP VPLS:
• VPLS data plane features: for example FIB management, SAPs, LAG access, BUM rate
limiting.
• MPLS tunneling: LDP, LDP over RSVP-TE, RSVP-TE, MP-BGP based on RFC3107
(Option C solution)
• HVPLS topologies, Hub and Spoke traffic distribution
• Coexists with LDP VPLS (with or without BGP-AD) in the same VPLS instance.
→ LDP, BGP-signaling should operate in disjoint domains to simplify loop avoidance
• Coexist with BGP-based multi-homing.
• BGP VPLS is supported as the control plane for BVPLS.
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