Virtual Private LAN Service
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FD 100/320Gbps NT and FX NT IHub Services Guide
3HH-11985-AAAA-TQZZA Issue: 13
•
Layer-2 MTU
The Maximum Transmission Unit to be used on pseudowires.
• Reserved
This field is reserved and must be set to zero and ignored on reception except for
the solution described in [BGP-Mhoming] PRD where it is used for VPLS
Preference.
5.11.1.1 Control Flags
The detailed format for the Control Flags bit vector is described in Table 113.
Table 113 Control Flags bit vector
The bits in the Control Flags are defined as follows:
• S — sequenced delivery of frames MUST or MUST NOT be used when sending
VPLS packets to this PE, depending on whether S is 1 or 0, respectively
• C — a Control work MUST or MUST NOT be present when sending VPLS packets
to this PE, depending on whether C is 1 or 0, respectively. By default, Nokia
implementation uses 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 BP pseudowire(s) mapped to that SDP goes
down; there is no BGP-update sent
01234567
DMBZ CSMBZ
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