Oam Overview; Lsp Diagnostics - Alcatel-Lucent 7750 SR OS Service Manual

OAM Overview

OAM Overview
Delivery of services requires a number of operations occur properly and at different levels in the
service delivery model. For example, operations such as the association of packets to a service,
VC-labels to a service and each service to a service tunnel must be performed properly in the
forwarding plane for the service to function properly. In order to verify that a service is
operational, a set of in-band, packet-based Operation, Administration, and Maintenance (OAM)
tools is required, with the ability to test each of the individual packet operations.
For in-band testing, the OAM packets closely resemble customer packets to effectively test the
customer's forwarding path, but they are distinguishable from customer packets so they are kept
within the service provider's network and not forwarded to the customer.
The suite of OAM diagnostics supplement the basic IP ping and traceroute operations with
diagnostics specialized for the different levels in the service delivery model. There are diagnostics
for MPLS LSPs, SDPs, Services and VPLS MACs within a service.

LSP Diagnostics

The 7750 SR OS LSP diagnostics are implementations of LSP ping and LSP traceroute based on
RFC 4379, Detecting Multi-Protocol Label Switched (MPLS) Data Plane Failures. In an LDP
ECMP network, a unique-path trace can be accomplished by specifying a unique 127/8 IP address
for the path-destination ip-address parameter. Note that the 7750 SR can send multipath type 0 or
8, and up to a maximum of 36 bytes for multipath length (refer to RFC 4379 for more details). The
7750 SR supports unique-path trace on an LER of an LDP ECMP path. LSP ping, as described in
the draft, provides a mechanism to detect dataplane failures in MPLS LSPs. LSP ping and LSP
traceroute are modeled after the ICMP echo request/reply used by ping and traceroute to detect
and localize faults in IP networks.
For a given FEC, LSP ping verifies whether the packet reaches the egress label edge router (LER),
while in LSP traceroute mode, the packet is sent to the control plane of each transit label switched
router (LSR) which performs various checks to see if it is actually a transit LSR for the path.
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