Mstp General Principles - Nokia 7302 Manual

Virtual Private LAN Service
5.4.7.4
MSTP represents modification of RSTP which allows the grouping of different VLANs
into multiple MSTIs. To enable different devices to participate in MSTIs, they must
be consistently configured. A collection of interconnected devices that have the
same MST configuration (region-name, revision and VLAN-to-instance assignment)
comprises an MST region.
There is no limit to the number of regions in the network, but every region can support
a maximum of 1615 MST instances, with different VLAN ranges. VLANs which are
not included explicitly in an MSTP instance fall into the default MSTP instance 0.
Instance 0 is a special instance for a region, known as the Internal Spanning Tree
(IST) instance. All other instances are numbered 1 to 4093. IST is the only
spanning-tree instance that sends and receives BPDUs (typically BPDUs are
untagged). All other spanning-tree instance information is included in MSTP records
(M-records), which are encapsulated within MSTP BPDUs. This means that single
BPDU carries information for multiple MSTI which reduces overhead of the protocol.
Any given MSTI is local to an MSTP region and completely independent from an
MSTI in other MST regions. Two redundantly connected MST regions will use only a
single path for all traffic flows (no load balancing between MST regions or between
MST and SST region).
Traditional L2 switches running MSTP protocol assign all VLANs to the IST instance
per default. The operator may then "re-assign" individual VLANs to a given MSTI by
configuring per VLAN assignment. This means that an ISAM can be considered as
the part of the same MST region only if the VLAN assignment to IST and MSTIs is
identical to the one of L2 switches in access network.
5.4.7.5
The ISAM uses m-VPLS to group different SAPs under a single STP instance. The
VLAN range covering SAPs to be managed by a given m-VPLS is declared under a
specific m-VPLS SAP definition. MSTP mode-of-operation is only supported in an
m-VPLS.
When running MSTP, by default, all VLANs are mapped to the CIST. On the m-VPLS
level VLANs can be assigned to specific MSTIs.
5.4.7.6
The control word command enables the use of the control word individually on each
mesh-sdp or spoke-sdp. By default, the control word is disabled. When the control
word is enabled, all VPLS packets, including the BPDU frames are encapsulated with
the control word.
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MSTP General Principles

MSTP implementation
Pseudowire Control Word
3HH-11985-AAAA-TQZZA
FD 100/320Gbps NT and FX NT IHub Services Guide
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