deploying and managing ip over wdm networks - Index of

48 Deploying and Managing IP over WDM Networks
3.5.4 MPLS Tools
Apart from these tools, the IETF working groups are proposing some MPLSspecific
tools for monitoring and carrying out basic operations and maintenance
(OAM) of MPLS-enabled networks. Most proposed diagnostic tools rely upon
IP (e.g., the LSP ping [29] and the generic tunnel tracing [30]).
3.5.4.1 LSP Ping
LSP ping is a simple and efficient mechanism to detect or diagnose data plane
failures in MPLS LSPs, specific to reservation protocol with traffic engineering
extensions (RSVP-TE) networks.
Ingress LSR sends ICMP echo_request messages over the LSP, which
should be returned by the egress LSR. If after a defined time period ICMP messages
are not returned, then ingress LSR sends a LSP-ping probe packet
(RSVP-TE extension) to the egress LSR over the LSP under test. Egress LSR
acknowledges receipt of the probe packet by returning the LSP_ECHO object
in the RSVP Resv message back to the ingress LSR.
If the ingress LSR does not receive a Resv message from the egress LSR
that consists of an LSP_ECHO object within a period of time, it declares the
LSP as down. At this point, the ingress LSR should apply the necessary procedures
to fix the LSP. This may include generating a message to a networkmanagement
console, tearing down and rebuilding the LSP, and rerouting user
traffic to a backup LSP.
3.5.4.2 Generic Tunnel Tracing
This tool helps to reduce the time of detecting or diagnosing failures within a
tunneled network. It solves some missing functionality in traditional traceroute
command. Its main features are:
• Trace path through generic tunnels (e.g., MPLS, IP-in-IP);
• Support heterogeneous nested tunnels (e.g., IP-in-IP over MPLS);
• Trace through forwarding plane or control plane.
This tool requires a protocol that supports these applications. This
protocol reveals the path between two points in an IP network. When access
policy allows it, the protocol also reveals tunnel details, including type of tunnel.
The protocol supports traceProbe and traceResponse messages carried over
UDP.
Another interesting proposal for MPLS-OAM can be found in [31].