VT cross-connections for BLSR

BLSR access

A VT-accessed BLSR must contain VT Type 3 nodes but may also include VT Type 2 and/or VT Type 1 nodes. For BLSRs containing VT Type 1 nodes, VT circuits can be provisioned if they do not pass through a Type 1 node. In rings operating with automatic ring discovery, the Ring Node VT Type parameter can be reported using the View → Rings → Ring Map command from the System View menu.

Reference the following for Ring Node VT Type descriptions:

Type 1: The node does not support VT BLSR access. All Alcatel-Lucent products which support BLSRs but do not support VT access.
Type 2: The node (Release 4.0 and later) supports VT-accessed STS-1 pass-through cross-connections only. VT cross-connection provisioning is not supported. Type 2 nodes are equipped with LNW26B 28, 31, 77, or 121B-159B OC-48 OLIU circuit packs.
Type 3: The node (Release 4.0 and later) supports VT cross-connections and VT-accessed STS-1 pass-through cross-connections. Type 3 nodes are equipped with LNW27, 29, 32, 76, 202, or 221–259 OC-48 OLIU circuit packs or LNW56, 57, 58, 502, 523, 527, 554, or 555 OC-192 OLIU circuit packs.

VT cross-connection parameters

In addition to regular BLSR STS-1 cross-connection parameters, the following parameters are required for provisioning VT1.5 BLSR cross-connections:

VT Source NE Name (vtloca): vtloca is the source node TID of a VT1.5 BLSR cross-connection.
VT Accessed (vtacc): vtacc is an attribute of a STS-1 BLSR pass-through cross-connection. It specifies whether or not the VTs transported within the STS-1 are cross-connected at the VT1.5 rate at other nodes in the circuit.

Rules for VT Source/Destination NE Name parameters

The following rules apply for specifying parameters when manually provisioning the VT squelch map entries:

VT Cross-Connection Type	VT Source NE Name (vtloca)
1-way unswitched or 2-way unswitched	Must not be provisioned.
1-way pass-through or 2-way pass-through	Must not be provisioned.
2-way add/drop (including inter-ring and switched cross-connections)	Must be provisioned if the source aid is a VT in a BLSR protection group.
1-way (including inter-ring and switched cross-connections)	Must be provisioned if the source aid is a VT in a BLSR protection group.

Source/Destination NE Name (loca/locz) parameters

In addition to provisioning vtloca parameters when provisioning VT cross-connections, it is also necessary to provision the Source NE Name (loca) and/or Destination NE Name (locz) parameters for the STS-1 that is carrying the VT connections. For each direction of transmission, the source/destination node of a VT-accessed STS-1 is the nearest node in the ring at which VT cross-connections are provisioned to that STS-1. When provisioning multiple VT cross-connections on a single STS-1, the STS-1 loca/locz parameter for all the VT cross-connections must be the same.

If, at a given ring node in a VT circuit, the STS-1 carrying the VT traffic will not be VT accessed at that node, the user may provision a single STS-1 pass-through cross-connection rather than multiple VT pass-through cross-connections. This single cross-connection will not use VT fabric capacity. For this STS-1 cross-connection it is necessary to provision both the loca and locz parameters. For each direction of transmission, the source/destination node of this STS-1 is the nearest node in the ring at which VT cross-connections are provisioned to that STS-1.

VT Accessed STS-1 pass-through cross-connections

In addition to provisioning the loca and locz parameters for VT-accessed STS-1 pass-through cross-connections, it is also necessary to mark these cross-connections as VT Accessed(vtacc) in order to properly unsquelch these STS-1s at switching nodes if the source or destination node is isolated. Likewise, if an STS-1 pass-through is not supporting VT circuits, it must not be marked as VT Accessed.