Added next-hop-network-instance under mpls egress config.

[vishnureddybadveli]

Change Scope
(M) release/models/mpls/openconfig-mpls-static.yang

Packet flow:
An IP in MPLS packet enters the device from the backbone/provider network
The MPLS packet enters from the “DEFAULT” network-instance
The inner IP packet is a customer packet
Goal is to decap/pop a provider MPLS label and lookup on the inner IP packet in the customer’s VRF

Intent is to do a lookup for the nexthop (to determine egress interface and rewrite) in a vrf that is different from the ingress interface's VRF.
For example: in some vpc use case ingress interface is in the default VRF as it's facing the providers network and the egress interface is in a customer specific VRF.

Currently model does not support mpls route to a specific next hop network instance, we are adding support for network instance in which to resolve the next hop.

/network-instances/network-instance/mpls/lsps/static-lsps/static-lsp/egress/lsp-next-hops/lsp-next-hop/config/next-hop-network-instance
/network-instances/network-instance/mpls/lsps/static-lsps/static-lsp/egress/lsp-next-hops/lsp-next-hop/state/next-hop-network-instance

Platform Implementations
Arista:
CLI configuration:

mpls static top-label <label> <nexthop-ip> vrf <vrf> pop payload-type ipv4/6
mpls static top-label <label> <nexthop-ip> vrf <vrf> pop 

Not adding any OC to cover the payload-type because this is not needed operationally and the vendor is expected to support any payload type without statically configuring it.

Juniper:
https://www.juniper.net/documentation/us/en/software/junos/cli-reference/topics/ref/statement/vrf-table-label-edit-routing-instances-vp.html

[dplore]

/gcbrun

[OpenConfigBot]

No major YANG version changes in commit 1db5287

[dplore]

Please update the PR description to include why the change is being added and update the yang model version numbers.

[AnnamalaiRajeev]

Hello Vishnu as discussed on the operators board. Please include vendor config and usecase. Limit augment to only egress LSP. thx

[vishnureddybadveli]

Hello Vishnu as discussed on the operators board. Please include vendor config and usecase. Limit augment to only egress LSP. thx

Rajeev, description is updated with only egress use case and one vendor config. We are looking for a second vendor that can implement similar functionality. Once we find second vendor I will work on the augment part.

[dplore]

@vishnureddybadveli , can you provide a config example from JunOS? The referenced documentation sort of sounds like it matches this use case, but it's not clear. An example config snippet would help. Or alternatively, you could reference a different implementation if that is easier to provide an example.

[dplore]

/gcbrun