# Ping Extensions for Point-to-Multipoint LSPs Connectivity Verification at Egress Nodes

To enable detection of data plane failures at egress nodes in point-to-multipoint LSPs, the MPLS ping extensions in point-to-multipoint LSPs define the following new sub-type-length-values (TLVs) for the Target FEC Stack TLV and new TLVs:

- RSVP P2MP IPv4 Session sub-TLV
- P2MP Responder Identifier TLV
- Echo Jitter TLV

## RSVP P2MP IPv4 Session Sub-TLV Overview

The RSVP P2MP IPv4 Session TLV identifies the point-to-multipoint LSP for which you are verifying the data plane. This TLV has a type number of 17. To identify the point-to-multipoint LSP for which you are running diagnostic connectivity checks, the echo request message must carry a Target FEC Stack TLV that contains an RSVP P2MP IPv4 Session sub-TLV. The point-to-multipoint LSP ping functionality performs necessary validation with RSVP-TE before sending the response to the source. For other sub-TLVs defined for identifying point-to-multipoint LDP MPLS LSP, the ping feature sends an error response.

## P2MP Responder Identifier TLV Overview

The point-to-multipoint MPLS LSP ping extensions enable a specific egress node of the point-to-multipoint MPLS LSP to be selected to verify that the data plane of the path to the particular egress node does not possess any failures. Use the new P2MP Responder Identifier TLV and associated rules for processing the LSP ping message (echo request) that contain this new TLV to validate whether the IP address specified in the TLV is an IP address of one of the interfaces in the router.

- If the IP address in the TLV matches the IP address assigned to one of the interfaces, the point-to-multipoint MPLS LSP ping feature sends the success response to the originator.
- If the IP address specified in the TLV does not match any of the IP addresses assigned to the interfaces, no response is sent to the originator.

If errors exist in the syntax of TLVs in the message received or if the router to which echo request packets are sent is not an egress node for the point-to-multipoint MPLS LSP, the echo response is sent to the originator, regardless of the presence of the P2MP Responder Identifier TLV in the request packet.

IETF draft, Detecting Data Plane Failures in Point-to-Multipoint Multiprotocol Label Switching (MPLS) - Extensions to LSP Ping (draft-ietf-mpls-p2mp-lsp-ping-08.txt) (February 2010 expiration), recommends a particular type value for the P2MP Responder Identifier TLV.

The type value used by point-to-multipoint LSPs in Junos OS differs from the type value specified in the IETF draft. To enable interoperability with routers running Junos OS (which are often employed as the ingress, transit, or branch nodes in point-to-multipoint LSPs), the point-to-multipoint MPLS LSP ping feature in JunosE Software interprets both type values to identify the TLV (P2MP Responder Identifier).

## Echo Jitter TLV Overview

The point-to-multipoint MPLS LSP ping extensions enable the initiator or ingress of the ping operation to request the egress nodes not to send responses immediately after the echo request message is received, but delay the response by a certain period of time. Use the new Echo Jitter TLV and associated rules for processing the LSP ping message (echo request) that contains this the Echo Jitter TLV to delay the transmission of the response by a time interval that is limited by the value specified in the Echo Jitter TLV.

The point-to-multipoint MPLS LSP ping functionality in JunosE Software supports a delay of up to 30 seconds. If the value specified in the Echo Jitter TLV is not within the supported range, the egress node uses a value within the range as the time to wait to send the echo response.

IETF draft, Detecting Data Plane Failures in Point-to-Multipoint Multiprotocol Label Switching (MPLS) - Extensions to LSP Ping, uses a particular type value for the Echo Jitter TLV. The point-to-multipoint MPLS LSP ping functionality in JunosE Software interprets the suggested type value in the draft to denote the new TLV (Echo Jitter).

## Traceroute Overview

The point-to-multipoint LSP ping feature enables the egress node to respond to the traceroute requests that the ingress node initiates in the same manner as the egress node responds to a ping request. No additional or separate configuration is needed to enable the path to the egress nodes to be traced by ingress nodes in point-to-multipoint LSPs.

#### Related Documentation

- TLVs and Sub-TLVs Supported for Point-to-Multipoint LSPs Connectivity Verification at Egress Nodes
- Point-to-Multipoint LSPs Connectivity Verification at Egress Nodes Overview
- Verifying and Troubleshooting MPLS Connectivity