SR P2MP policy

The CLI can be used to configure a P2MP policy, its CPs, and path instances on the root node. The CLI can also be used to create the replication segments on the root, transit, and leaf nodes. The P2MP policy can be assigned to NG-MVPN Inclusive P-Multicast Service Interfaces (IPMSIs) and Selective PMSIs (SPMSIs).

On each node, each replication segment represents a unique P2MP LSP with the following key: <tree ID, root ID, instance ID>. The instance ID and tree ID are unique to each root.

NG-MVPN can be configured using the CLI or SNMP on the PCCs.

The root node discovers all of the leaf nodes through NG-MVPN. The root and leaf nodes information is updated to the PCE using PCEP.

The PCE calculates the shortest path from the root to the leaf nodes and takes into account any programmed constraints. The PCE has an end-to-end view of the network through BGP LS.

After calculating the tree, the PCE downloads the P2MP policy to the root and the replication policies to the root, transit, and leaf nodes.

Updates to the P2MP policy or the replication paths are calculated by the PCE and downloaded accordingly.

This section provides examples to configure an MVPN service with SR P2MP policies for SPMSIs and IPMSIs. The configuration examples use the following network.

node-2-(100.101.1.x/24)---P-(101.102.1.x/24)----Leaf-1
|--(101.103.1.x/24)----Leaf-2

The following are the network settings:

• Node-2 is 100.0.0.100.
• P is 100.0.0.101.
• Leaf-1 is 100.0.0.102.
• Leaf-2 is 100.0.0.103.

The following example show a reserved label block configured (in this example, ‟treeSID”), from which the tree SID labels are allocated.

[ex:/configure router "Base" mpls-labels]
A:admin@node-2# info
    reserved-label-block "treeSID" {
        start-label 30000
        end-label 30999
    }

A:node-2>config>router>mpls-labels# info 
----------------------------------------------
            reserved-label-block "treeSID"
                start-label 30000 end-label 30999
            exit

[ex:/configure router "Base" p2mp-sr-tree]
A:admin@node-2# info
    reserved-label-block "treeSID"

A:node-2>configure>router>p2mp-sr-tree# info 
----------------------------------------------
        reserved-lbl-block "treeSID"

[ex:/configure router "Base" p2mp-sr-tree]
A:admin@node-2# info
    ...
    p2mp-policy "IPMSI-VPRN1" {
        admin-state enable
        node-2-address 100.0.0.100
        tree-id 9000
        candidate-path "Primary-path" {
            admin-state enable
            active-instance 1
            preference 1000
            path-instances 1 {
                instance-id 1000
            }
        }
    }
    p2mp-policy "SPMSI-VPRN1" {
        admin-state enable
        node-2-address 100.0.0.100
        tree-id 9000
        candidate-path "Primary-path" {
            admin-state enable
            active-instance 1
            preference 1000
            path-instances 1 {
                instance-id 1000
            }
        }
    }

A:node-2>config>router>p2mp-sr-tree# info 
----------------------------------------------
        ...
        p2mp-policy "IPMSI-VPRN1"
            node-2-address 100.0.0.100
            node-2-tree-id 9000
            p2mp-candidate-path "Primary-path"
                preference 1000
                instances
                    instance 1 instance-value 1000
                exit
                active-instance 1
                no shutdown
            exit
            no shutdown
        exit
        p2mp-policy "SPMSI-VPRN1"
            node-2-address 100.0.0.100
            node-2-tree-id 9001
            p2mp-candidate-path "Primary-path"
                preference 1000
                instances
                    instance 1 instance-value 1000
                exit                  
                active-instance 1
                no shutdown
            exit
            no shutdown
        exit

[ex:/configure service vprn "1"]
A:admin@node-2# info
    customer "1"
    interface "to14" 
    pim {
        rp {
            ipv4 {
                bsr-candidate {
                admin-state enable
            }
                rp-candidate {
                admin-state enable
            }
        }
    }
    mvpn {
        c-mcast-signaling bgp
        auto-discovery {
            type bgp
        }
        vrf-target {
            unicast true
        }
        provider-tunnel {
            inclusive {
                p2mp-sr {
                    static-policy "IPMSI-VPRN1"
                    admin-state enable
                }
            }
            selective {    
                data-threshold {
                    group-prefix 231.0.0.0/24 {
                        threshold 10
                    }
                }
                p2mp-sr {
                    static-policy "SPMSI-VPRN1"
                    admin-state enable
                }
                data-threshold 231.0.0.0/24 10
               
            }
        }
    }
    bgp-ipvpn {
        mpls {
            admin-state enable
            route-distinguisher "70:70"
            vrf-target {
                community "target:70:70"
            }
            auto-bind-tunnel {
                resolution filter
                resolution-filter {
                    sr-isis true
                }
            }
        }
    }

A:node-2>config>service>vprn# info 
----------------------------------------------
            route-distinguisher 70:70
            auto-bind-tunnel
                resolution-filter
                    sr-isis
                exit
                resolution filter
            exit
            vrf-target target:70:70
            interface "to14" create
            exit
… 
            pim
                rp
                    static
                    exit
                    bsr-candidate     
                        no shutdown
                    exit
                    rp-candidate
                        no shutdown
                    exit
                exit
                no shutdown
            exit
            mvpn
                auto-discovery default
                c-mcast-signaling bgp
                provider-tunnel
                    inclusive
                        p2mp-sr
                            static-policy " IPMSI-VPRN1"
                            no shutdown
                        exit
                    exit
                    selective
                        p2mp-sr
                            static-policy " SPMSI-VPRN1"
                            no shutdown
                        exit          
                        data-threshold 231.0.0.0/24 10
                    exit
                exit
                vrf-target unicast
                exit
            exit
            no shutdown

[ex:/configure router "Base" p2mp-sr-tree]
A:admin@node-2# info   
    ...
    replication-segment "IPMSI-VPRN1-NODE-2" {
        admin-state enable
        instance-id 1000
        node-2-address 100.0.0.100
        tree-id 9000
        sid-action push
        downstream-nodes 1 {
            admin-state enable
            next-hop-address "100.101.1.2"
            label {
                sid-list 1 {
                    replication-sid 30000
                }
            }
        }
    }
    replication-segment "SPMSI-VPRN1-node-2" {
        admin-state enable
        instance-id 1000
        node-2-address 100.0.0.100
        tree-id 9001
        sid-action push
        downstream-nodes 1 {
            admin-state enable
            next-hop-address "100.101.1.2"
            label {
                sid-list 1 {
                    replication-sid 30001
                }
            }
        }
    }

A:node-2>configure>router>p2mp-sr-tree# info 
----------------------------------------------
        ...
        replication-segment "IPMSI-VPRN1-NODE-2"
            node-2-address 100.0.0.100
            node-2-tree-id 9000
            sid-action push
            instance-id 1000
            next-hop-id "1"
                next-hop-address 100.101.1.2
                replication-sid 30000
                no shutdown
            exit
            no shutdown
        exit
        replication-segment "SPMSI-VPRN1-NODE-2"
            node-2-address 100.0.0.100
            node-2-tree-id 9001
            sid-action push
            instance-id 1000
            next-hop-id "1"
                next-hop-address 100.101.1.2
                replication-sid 30001
                no shutdown
            exit
            no shutdown
        exit

[ex:/configure router "Base" p2mp-sr-tree]
A:admin@node-2# info
    admin-state enable
    reserved-label-block "treeSID"
    replication-segment "rs-IPMSI-VPRN1-100.0.0.100" {
        admin-state enable
        instance-id 1000
        replication-sid 30000
        node-2-address 100.0.0.100
        tree-id 9000
        sid-action swap
        downstream-nodes 1 {
            admin-state enable
            # toleaf1
            next-hop-address "101.102.1.2"
            label {
                sid-list 1 {
                    replication-sid 30000
                }
            }
        }
        downstream-nodes 2 {
            admin-state enable
            # toleaf2
            next-hop-address "101.103.1.2"
            label {
                sid-list 1 {
                    replication-sid 30000
                }
            }
        }
    }

A:node-2>configure>router>p2mp-sr-tree# info 
----------------------------------------------
        reserved-lbl-block "treeSID"
        replication-segment "rs-IPMSI-VPRN1-100.0.0.100"
            node-2-address 100.0.0.100
            node-2-tree-id 9000
            sid-action swap
            incoming-sid 30000
            instance-id 1000
            next-hop-id "1"
                next-hop-address 101.102.1.2 //toleaf-1
                replication-sid 30000
                no shutdown
            exit
            next-hop-id "2"
                next-hop-address 101.103.1.2 //toleaf-2
                replication-sid 30000
                no shutdown
            exit
            no shutdown
        exit

[ex:/configure router "Base" p2mp-sr-tree]
A:admin@node-2# info
    admin-state enable
    reserved-label-block "treeSID"
    replication-segment "rs-IPMSI-VPRN1-100.0.0.100" {
        admin-state enable
        instance-id 1000
        replication-sid 30000
        node-2-address 100.0.0.100
        tree-id 9000
        sid-action pop
    }

A:node-2>configure>router>p2mp-sr-tree# info 
----------------------------------------------
        reserved-lbl-block "treeSID"
        replication-segment "rs-IPMSI-VPRN1-100.0.0.100"
            node-2-address 100.0.0.100
            node-2-tree-id 9000
            sid-action pop
            incoming-sid 30000
            instance-id 1000
            no shutdown
        exit

[ex:/configure router "Base" p2mp-sr-tree]
A:admin@node-2# info
    admin-state enable
    reserved-label-block "treeSID"
    replication-segment "rs-IPMSI-VPRN1-100.0.0.100" {
        admin-state enable
        instance-id 1000
        replication-sid 30000
        node-2-address 100.0.0.100
        tree-id 9000
        sid-action pop
    }

A:node-2>configure>router>p2mp-sr-tree# info 
----------------------------------------------
        reserved-lbl-block "treeSID"
        replication-segment "rs-IPMSI-VPRN1-100.0.0.100"
            node-2-address 100.0.0.100
            node-2-tree-id 9000
            sid-action pop
            incoming-sid 30000
            instance-id 1000
            no shutdown
        exit

Only facility bypass and link protection are supported for a P2MP policy. Node protection is not supported. The facility bypass can be created using shared replication segments. Shared replication segments do not have a tree ID. They are identified using a replication segment identifier within the tree ID.

At the Point of Local Repair (PLR), the primary replication segment has a protection next hop. This protection next-hop has a second OIF with its own outgoing label, which is used for the facility protection tunnel.

The facility protection tunnel can consist of multiple transit nodes until the tunnel reaches the Merge Point (MP). Replication segments are configured on these transit nodes to complete the facility protection tunnel. Multiple P2MP trees can share the facility protection tunnel at the PLR. The facility protection tunnel uses the implicit null label (see Implicit null case) or an actual label at the Penultimate Hop Popping (PHP) node (see Non-implicit null case).

After the primary path is recovered, the P2MP LSP switches back to the primary path and away from the protection next-hop (FRR). This switch back to primary may cause a brief traffic outage.

The replication SID next-hops send optimistic ARP to populate the ARP table. If the next-hop MAC address is not found in the ARP table (that is, the address is not populated by BFD, IGP, or any other packet), the optimistic ARP populates the ARP table. The reversion from FRR to the primary next-hop happens only if the primary path ARP entry is found in the ARP table.

BFD can be enabled under the p2mp-sr-tree context for the replication segment next-hops. BFD is enabled at the P2MP SR tree level. The P2MP SR tree registers itself with the current available BFD session. The BFD sessions need to be enabled using other protocols. For example, static route, OSPF, or IS-IS can enable the BFD session on an interface. The replication segments are registered with these BFD sessions. The replication segments cannot initiate a BFD session and rely on other protocols to initiate the BFD session because a replication segment is a unidirectional entity, while BFD is a bidirectional protocol.

When BFD is enabled under the p2mp-sr-tree context, all replication next hops that are using a Layer 3 interface with BFD enabled on that interface register with the BFD module. If the BFD status on the Layer 3 interface goes down, any replication segment next-hop that is using that Layer 3 interface goes operationally down. This operationally down status of the next-hop within a replication segment can cause an FRR.

Only single hop BFD is supported. BFD for unnumbered interfaces is not supported.

For IPv6, protocols such as OSPF or LDP create a BFD session to the link local interface. A static route can create a BFD session to link local or global IPv6 addresses. To use BFD for IPv6 next hops within a replication segment, the replication segment needs to be configured with a link local next-hop for protocols that create the BFD session to the link local address. This way, the replication segment next hop finds a BFD session created by one of these protocols.

The maximum P2MP SPMSI value configured under an MVPN selective provider tunnel does not affect any established SPMSIs. It only affects new spawning SPMSI counts.

If any existing SPMSIs are above the maximum P2MP SPMSI threshold, no new SPMSIs are spawned until the number of SPMSIs goes below the threshold.

Global optimization of the P2MP policy candidate path is supported, in addition to local FRR, where the protection next hop is downloaded by the replication segment and the FRR action is triggered by a port failure or BFD failure.

To use the global optimization behavior, the user creates another instance under the P2MP policy. The appropriate replication segments must be created for this optimized instance also. After the entire tree is created, the active instance under the CP can be set to this new, optimized instance and a switch from the previous instance to this optimized instance is performed. While the switch is in progress, the MVPN on the leaf is accepting traffic from both instances of the CP. After the switch is complete, the old instance can be deleted from the candidate path and its replication segments can be removed.

Global optimization is supported on the PCE. Local optimization of a replication segment using PCEP is not supported. If the PCE calculates an optimized path for a candidate path, that path instance is different from the current path instance. For this reason, a candidate path contains two path instances. The PCE must download a new path instance with an LSP ID of 0 and the PLSP ID of the current candidate path. This behavior applies to replication segments only.

When the current path instance is modified from the PCE to the PCC, the PCC-assigned LSP ID and PLSP ID are sent from the PCE to the PCC. This behavior ensures that the LSP ID of the replication segment for the existing path instances does not change.

You can clear all states on the PCC, including replication segments and P2MP policies. The state of the P2MP LSP on the PCC is operationally up as long as there is one valid OIF and is operationally up for that LSP.

Use the following command to clear all states on the PCC:

• MD-CLI

  configure router p2mp-sr-tree admin-state disable

• classic CLI

  configure router p2mp-sr-tree shutdown

For a PCE, to program the datapath with a pop action, the next hops must be programmed as 127.0.0.0/8 or IPv6 ::1. If the replication segment next-hop has no information, the next hop is reported to the PCE with status down.

For CLI-initiated replication segments, the next-hop label action can be set to pop, and the next hop does not need to be programmed as 127.0.0.0/8 or ::1.

For interfaces that are not configured as unnumbered, the next-hop used in the replication segment must be a direct (local) next-hop. The replication segment cannot resolve indirect next-hops to a downstream router loopback or system IP address.

The FRR outage time can exceed 50 ms when a node has a large number of replication segments that are using a protection tunnel for FRR.