Page 492 7750 SR OS Services Guide
In addition to the pseudowire label information, the "Layer2 Info Extended Community" attribute
must be included in the BGP Update for BGP VPLS to signal the attributes of all the pseudowires
that converge towards the originator VPLS PE.
The format is described below:
+------------------------------------+
| Extended community type (2 octets) |
+------------------------------------+
| Encaps Type (1 octet) |
+------------------------------------+
| Control Flags (1 octet) |
+------------------------------------+
| Layer-2 MTU (2 octet) |
+------------------------------------+
| Reserved (2 octets) |
+------------------------------------+
The meaning of the fields:
• Extended community type – the value allocated by IANA for this attribute is 0x800A
• Encaps Type - Encapsulation Type, identifies the type of pseudowire encapsulation. The
only value used by BGP VPLS is 19 (13 in HEX).This value identifies the encapsulation
to be used for pseudowire instantiated through BGP Signaling which is the same as the
one used for Ethernet pseudowire type in regular VPLS. There is no support for an
equivalent Ethernet VLAN pseudowire in BGP VPLS in BGP Signaling. Still it is
desirable to check the pseudowire-template vc-type to identify what kind of pseudowire is
really to be used. While vc-type ether should be the default for interoperability with JNPR,
it is desired to still have the vc-type vlan option to allow for the QoS transparency
features.
• Control Flags - control information regarding the pseudowires, see below for details
• Layer-2 MTU is the Maximum Transmission Unit to be used on the 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.
The detailed format for the Control Flags bit vector is described below:
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|D| MBZ |C|S| (MBZ = MUST Be Zero)
+-+-+-+-+-+-+-+-+
The following bits in the Control Flags are defined:
• 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
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