Benefits of VLAN Translation
Earlier, the router supported Rewrite Push and Pop operations to push and remove 1 or more 802.1Q tags from the service frames only. The CoS transparency could not be achieved along with VLAN tag manipulation.
This problem is solved with the VLAN Translation feature. The current implementation of the feature allows one or more 802.1Q tags to be replaced with other 802.1Q tags and thus the desired tag manipulation can be achieved. In a scenario with two EFPs egressing the same interface, each EFP can have a different VLAN rewrite operation, which is more flexible.
VLAN translation feature includes the following functionalities:
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1:1 VLAN translation - The VLAN of the incoming traffic (CE VLAN) is replaced by another VLAN (PE VLAN). The specification of the VLAN translation happens during the creation of the service request. The CoS field of the new tag is set to the same value as the CoS field of the existing VLAN tag.
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2:1 VLAN translation - The double tagged (Q-in-Q) traffic at the U-PE UNI port can be mapped to different flows to achieve service multiplexing. The CoS field of the new tag is set to the inner CE-VLAN (second tag) CoS value.
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1:2 VLAN translation - The outermost tag can be replaced with two tags. The CoS field of the new tags is set to the same value as the CoS field of the incoming 802.1Q VLAN tag.
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2:2 VLAN translation - The outermost two tags can be replaced with other two tags. The CoS field of the new tags is set to the same value as the CoS field of the incoming Q-in-Q (outer and inner tag CoS) service frame.
Scenarios showing VLAN Translation
The following scenarios show the VLAN translation.
Scenario 1 - 1:1 VLAN Translation
In the scenario above, t he broadcast or multicast from CPE1 has to be sent to CPE2 and CPE3. The incoming tag in the frame has a CoS value of 3. The service needs to be created that enables the CoS value to pass transparently to the other sites with the desired VLAN translation.
This behavior can be achieved using the 1:1 VLAN translation command on the service instance attached to CPE1. The Egress Service instance on Remote UPE device should be configured with the right encapsulation or Rewrite operation to achieve the correct tagging behavior (VLAN 50 on outgoing tag) for CPE3. As there is no inner tag here, the outer CoS is propagated in the newly added tag to both CPE2 and CPE3 ACs.
Scenario 2 - 2:1 VLAN Translation
The above scenario depicts an instance of a local E-Line service, with one AC (AC1) with double VLAN ID (inner 100 andouter 10) and the other AC (AC2) with VLAN ID (30). The frame with CoS=3 from the inner VLAN 100 in AC1 has to be delivered in AC2 with VLAN 30 and CoS=3. Similarly, for remote instance, we have AC (AC3) with VLAN 50 and same inner CoS 3 should be transparently carried over MPLS cloud to AC3 from AC1. The way we can achieve this behavior on router is with 2:1 VLAN translation command on service instance connected to AC1.
In this particular scenario, since there is a inner Tag present, inner CoS will be propagated in the newly added Tag to both CPE2 and CPE3 ACs.
Limitations for VLAN Translation with QoS
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Only 1:1 and 2:1 translate rewrites are supported. 1:2 and 2:2 translations are not supported.
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Translate operation can only be applied to a unique tag matching service instance.
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VLAN Translation is not supported on TEFP, encapsulation untagged, and BDI interfaces.
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Any VLAN Translation with rewrite pop2 is not supported.
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Translation is only supported for 802.1Q (0x8100) encapsulation.
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Translation is not supported for 802.1AD (0x88A8) and Customer Ethertype (0x9100 and 0x9200).
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Egress QoS policy is not supported on Trans 2:1 and 1:1 VLAN Translation, if ingress Translation or push EFPs do not have policy.
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For 1:1 to 1:1 scenario, marking is not supported.
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Ingress POP 0 or 1:1 CoS marking is not supported.
Limitations for VLAN Translation with QoS for RSP3
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EVC filtering is not supported.
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In L2VPN scenario EXP to CoS at the disposition does not work for EXPs set with conditional marker.
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CoS values is not supported with 2:1 translation for packets generated in ASIC IP SLA probes.
Scale Restrictions for RSP3
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A maximum of 4K EFP/BDs are supported.
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A maximum of 4K EoMPLS tunnels are supported.
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A maximum of 3500 L2 VFI circuits are supported.