About the VCA-VLAN Concept

VCA-VLAN (Virtual Connection Access - VLAN based) is the definition of traffic connectivity between traffic ports, within a single network element. VCA-VLAN construct is used to describe layer-2 connectivity, by providing the incoming VLAN stack for each traffic port. Along with the VLAN stack, the user defines the PCP mapping between VLAN, for managing class of services.

The VCA creation is simplified by hiding the VCE creation that was required previously. The VCA-VLAN main concept is built on defining the VLAN stack on both ports. The software uses the VLAN stack definition to automatically create the VCE in the infrastructure underneath.

VLAN Stack

The VLAN stack definition supports up to three incoming VLANs per port. A maximum of two incoming VLANs can be manipulated by changing the VLAN TPID, VLAN ID or VLAN PCP. A third VLAN can be defined but it can only be preserved; i.e. VLAN TPID, VLAN ID and VLAN PCP keep the same value.

EVC Action

By using VCA-VLAN, the EVC action (push, pop, replace, etc.) is no longer configurable. The EVC action is automatically derived when using the VCA-VLAN stack.

The VLAN difference between VLAN TP-A-X and VLAN TP-Z-X, where X is the same value on both sides, defines the EVC action. When the VLAN is the same on both TP-A-X and TP-Z-X, the EVC action is always replaced with two exceptions, which are:

• If the VLAN-TP-A-1 or VLAN-TP-Z-1 has a VLAN range, the action is preserved.
• If the VLAN stack size is 3 on either TP side, the EVC action between VLAN-TP-A-1 and VLAN-TP-Z-1 must be preserved, since only two VLANs can be manipulated.

VCA Type

The VCA-VLAN can describe connectivity using up to three VLANs. Each VLAN defines a different service.

In a VCA-VLAN containing VLANs, the following definitions apply:

• The most inner VLAN corresponds to the customer VLAN.
• The middle VLAN corresponds to the service provider VLAN.
• The outer VLAN is the operator VLAN, transporting a service from a service provider and identifies as the tunnel VLAN.

Sometimes when dealing with only two VLANs, the VLANs can have a different purpose. They can represent:

• A customer VLAN and service provider VLAN.
• A service provider VLAN and an operator VLAN (tunnel).

In order to differentiate the two use cases, the VCA-VLAN can be configured to contain or not contain a tunnel. By default, the VCA-VLAN never contains a tunnel unless it is absolutely required.

In the VCA-VLAN stack, the VLAN-TP-x-1 is the most inner VLAN, VLAN TP-x-2 is the middle VLAN, and VLAN-TP-x-3 is the outer VLAN.

When a VCA-VLAN contains a tunnel, a VCA is created automatically. The VCA name is the VCA-VLAN name with "-A" or "-Z" appended to it.

The VCA can be used to configure bandwidth regulator on the tunnel. Regulators on the tunnel are shared between all VCA-VLANs using the same tunnel. The PCP of the tunnel VLAN is used for mapping the bandwidth regulator. The bandwidth regulator created on the VCAVLAN with service type, uses the PCP of the service provider VLAN for mapping the bandwidth regulator.

• The VCA"-A" shall be used to create bandwidth regulator on the incoming traffic of the TP-A port.
• The VCA"-Z" shall be used to create bandwidth regulator on the incoming traffic of the TP-Z port.

In the case of VCA-VLAN with a stack of one, the incoming PCP is the outer VLAN PCP.

Using the classification, direct PCP mapping or DSCP mapping can be used for untagged traffic, or for specific CoS mapping. Same classification can be used when the VLAN stack is "all-to-one".

When the EVC action is pop or pop-pop in one direction, the PCP mapping 8P0D-8P0DDecode is used automatically. The PCP mapping is not configurable. The 8P0D-8P0D-Decode is similar to 8P0D-8P0D with the DEI decode enabled. This allows performing color aware bandwidth regulation. If the color aware is not required, the bandwidth regulator should be configured in color blind mode.

In summary, the incoming PCP used for manipulating PCP is always the service provider VLAN, unless bandwidth regulators are configured on the VCA tunnel. In the case of VCA tunnel, the outer VLAN is used.

Multiple PCP mappings can be assigned per direction, on the condition that for a given Green PCP value, the Yellow PCP value must be the same for all PCP mappings on the remote device. When the Green PCP and Yellow PCP values are different, only one (1) CoS profile configuration per remote device is supported.

Example 1:

CoS Profile 1:

PCP-In[0] maps to Green[0]=1 and Yellow[0]=1.

As this is the first configuration, there is no conflict.

CoS Profile 2:

PCP-In[3] maps to Green[3]=1 and Yellow[3]=1

As we are adding another entry that is using the same definition as CoS Profile, this is allowed.

CoS Profile 3:

PCP-In[4] maps to Green[4]=1 and Yellow[4]=2

(Italic) In this example, the configuration will be refused because there is an existing CoS profile (s) that is/are using the Green PCP value (1) with Yellow PCP value (1), resulting in a conflict.

CoS Profile 4:

DSCP-In[5] maps to Green[5]=1 and Yellow[5]=1

Although this is an example of a DCSP CoS Profile configuration, since we are using the same Green PCP value (1) with the same Yellow PCP value (1) as existing configuration, there is no conflict and this allowed.

CoS Profile 5:

DSCP-In[5] maps to Green[5]=1 and Yellow[5]=6

Although this example is for a DSCP CoS Profile configuration, it will be refused because there is an existing CoS profile(s) that is/are using the Green PCP value (5) with Yellow PCP value (5), resulting in a conflict.

Example 2:

CoS Profile 1:

PCP-In[4] maps to Green[4]=1 and Yellow[4]=2

In this example, this configuration will be accepted if there are no other CoS profile configuration in the same device that have defined Green PCP value (1) and Yellow PCP value (2).

CoS Profile 2:

PCP-In[3] maps to Green[3]=1 and Yellow[3]=1

In this example, the configuration will be refused because we have already defined the use of Green PCP value (1) and Yellow PCP value (2) in CoS Profile 1 above.

CFM

The VCA-VLAN is also used to configure CFM sessions. Using VCA-VLAN, the VLAN stack is not redefined in CFM in order simplify configuration and avoid human error. Using VCA-VLAN, UP MEP and Down MEP with up to three VLAN tags can be created.

For details on the fields and their descriptions, refer to the table called Maintenance Association (SOAM ▶CFM ▶MA/MEG) in the article Setting Up Traffic Polocies.

When creating a MEG, the VLAN is provided by selecting a specific VLAN in the VCA-VLAN stack by providing the VCA Name and the VCA-VLAN reference. When a MEP is associated to the MEG, it inherents the VLAN stack definition from the VCA-VLAN, according to its direction (Up or Down).

For Down MEP, the VLAN ID of the selected VCA-VLAN must be configured in the VID list. The only exception is for untag Down MEP; the VID list must be empty. For instance, configuring a Down MEP on VCA VLAN TP-Z-3 is untag, if the VLAN ID is not configured in the VLAN ID list. If the VLAN is configured, the Down MEP contains the VLAN.

The Up MEP can be configured only on the VCA-VLAN-TP-A-1 or VCA VLAN-TP-Z-1. For example, an UP MEP configured on VCA-VLAN-TP-A-1, the MEG VLAN ID in the MEG’s VIDlist shall be the value of VLAN-TP-A-1. The Up MEP is configured on the TP-A port, and therefore, the SOAM frames go through in the UP direction in the VCA-VLAN stack from A-to- Z, and the associated VLANs are added to the SOAM frame. In the case where the port is untag, the user shall reference VCA-VLAN-TP-X only, and the VLAN stack-size of VCA-VLANTP- Y shall be greater than or equal to 1. The VLAN ID supplied in the MEG’s vid-list must be the VLAN ID assigned to the VCA-VLAN-TP-Y-1.