Table Of Contents

Multiprotocol Label Switching "MPLS"

Technology Description

MPLS

Label Distribution Protocol (LDP)

Inventory and Information Model Objects (IMOs)

MPLS Interface

Label Switching Entity

Equivalent Label Switching Entry

MPLS Entry

MPLS Aggregate Entry

Label Distribution Protocol (LDP) Service

Label Distribution Protocol Peer

LDP Peer Discovery Source

Network Topology

Service Alarms

Multiprotocol Label Switching "MPLS"

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This chapter describes the level of support that Cisco ANA provides for MPLS, as follows:

•Technology Description

•Inventory and Information Model Objects (IMOs)

•Network Topology

•Service Alarms

Technology Description

MPLS

Multi-Protocol Label Switching (MPLS) was originally presented as a way of improving the forwarding speed of routers but is now emerging as a crucial standard technology that offers new capabilities for large scale IP networks. Traffic Engineering (TE), the ability of network operators to dictate the path that traffic takes through their network, and Virtual Private Network (VPN) support are examples of two key applications where MPLS is superior to any currently available IP technology. It integrates Layer 2 information about network links (bandwidth, latency, utilization) into Layer 3 (IP) within a particular autonomous system, or ISP, in order to simplify and improve IP packet exchange, while giving network operators a great deal of flexibility to divert and route traffic around link failures, congestion, and bottlenecks.

When packets enter a MPLS-based network, Label Edge Routers (LERs) give them a label (identifier). These labels not only contain information based on the routing table entry (i.e., destination, bandwidth, delay, and other metrics), but also refer to the IP header field (source IP address), Layer 4 socket number information, and differentiated service. Once this classification is complete and mapped, different packets are assigned to corresponding Labeled Switch Paths (LSPs), where Label Switch Routers (LSRs) place outgoing labels on the packets.

Label Distribution Protocol (LDP)

LDP enables neighboring provider or provider edge routers acting as Label Switch Routers (LSRs) in a MPLS-aware network to exchange label prefix binding information which is required for forwarding traffic. The LSRs discover potential peers in the network with which they can establish LDP sessions in order to negotiate and exchange the labels (addresses) to be used for forwarding packets.

Two types of LDP peer discovery are supported:

•Basic discovery—Used to discover directly connected LDP LSRs. A LSR sends hello messages to the "all routers on this subnet" multicast address, on interfaces for which LDP has been configured.

•Extended discovery—Used between non-directly connected LDP LSRs. A LSR sends targeted hello messages to specific IP addresses. Targeted sessions are configured since the routers are not physically connected, and broadcasting would not reach the peers. The IP addresses of both peers are required for extended discovery.

Inventory and Information Model Objects (IMOs)

This section includes the following tables:

•MPLS Interface (IMpls)

•Label Switching Entity (ILse)

•Label Switching Entity (ILse)

•MPLS Entry (IMplsEntry)

•MPLS Aggregate Entry (IMplsAggregateEntry)

•Label Distribution Protocol Service (ILdpService)

•Label Distribution Protocol Peer (ILdpPeer)

•LDP Peer Discovery Source (ILdpPeerDiscoverySource)

MPLS Interface

The following Network/Data Link layer MPLS Interface object, represent an MPLS configuration in a router interface. It is bound by its Containing Termination Points attribute to a Data Link Layer Interface object, and is primarily being accessed by Network layer IP Interface, bound by its Contained Connection Termination Points attribute. It is also being accessed by Label Switching Entity.

Table 12-1 MPLS Interface (IMpls)

Attribute Name	Attribute Description	Scheme	Polling Interval
Distribution Protocol	Distribution protocol (Null, LDP, TDP, RSVP, TDP and LDP)	IP Core	Configuration
Outer and Inner Labels	Outer and inner labels for PathTracer	IP Core	Configuration
Traffic Engineering Properties	Traffic engineering properties (MPLS TE Properties)	IP Core	Configuration
IANA Type	IANA type of the sub/layer	N/A	N/A
Containing Termination Points	Underlying termination points (connection or physical)	IP Core	N/A
Contained Connection Termination Points	Bound Connection Termination Points	IP Core	N/A

Label Switching Entity

The following Label Switching Entity object describes the label distribution protocol independent Label Switching forwarding component of a Label Switching Router (LSR), which is bound by its Logical Sons attribute to all Network or Data Link layer MPLS Interface objects, which IP Packets are being switched between by this Label Switching Entity.

Table 12-2 Label Switching Entity (ILse) 

Attribute Name	Attribute Description	Scheme	Polling Interval
MPLS Table	Array of Equivalent Label Switching Entries between MPLS Interfaces	IP Core	Configuration
MPLS Aggregate Table	Array of Equivalent Label Switching Entries from MPLS Interfaces into VRFs	IP Core	Configuration
MPLS Tunnel Segments	Array of switched MPLS TE tunnel segments (GUI usage) (see Multi Protocol Label Switching Traffic Engineering (MPLS-TE))	IP Core	Configuration
LDP Service	Label Distribution Protocol (LDP) Service which holds the Label Distribution Protocol Peers	IP Core	Configuration
Logical Sons	Array of all MPLS Interfaces, which IP packets are being switched between, by this Label Switching Entity	IP Core	N/A

Equivalent Label Switching Entry

The following Equivalent Label Switching Entry, MPLS Entry and MPLS Aggregate Entry objects describe an MPLS Label Switching Table's entries, each as an array of either MPLS Entries or MPLS Aggregate Entries sharing a single ingress label.

Table 12-3 Equivalent Label Switching Entry (ILSEEntries)

Attribute Name	Attribute Description	Scheme	Polling Interval
Label Switching Entries	Array of either MPLS Entries or MPLS Aggregate Entries (sharing a single ingress label)	IP Core	Configuration

MPLS Entry

Table 12-4 MPLS Entry (IMplsEntry)

Attribute Name	Attribute Description	Scheme	Polling Interval
Incoming Label	Incoming label	IP Core	Configuration
Outgoing Interface and Label	Outgoing interface and label	IP Core	Configuration
Switching Action	Switching action (Null, Pop, Swap, Aggregate, Untagged, Pop and Act)	IP Core	Configuration
Next Hop IP Address	Next hop IP address	IP Core	Configuration

MPLS Aggregate Entry

Table 12-5 MPLS Aggregate Entry (IMplsAggregateEntry)

Attribute Name	Attribute Description	Scheme	Polling Interval
Virtual Routing Entity	Virtual Routing (VRF) entity	IP Core	Configuration
Incoming Label	Incoming label	IP Core	Configuration
Outgoing Interface and Label	Outgoing interface and label	IP Core	Configuration
Switching Action	Switching action (Null, Pop, Swap, Aggregate, Untagged, Pop and Act)	IP Core	Configuration
Next Hop IP Address	Next hop IP address	IP Core	Configuration

Label Distribution Protocol (LDP) Service

The following Label Distribution Protocol (LDP) Service object, which used in MPLS network environments, describes the Label Distribution Protocol service and is accessed only by the Label Switching Entity's LDP Service attribute.

Table 12-6 Label Distribution Protocol Service (ILdpService)

Attribute Name	Attribute Description	Scheme	Polling Interval
Local Identification	Local LDP identification	IP Core	Configuration
Status	Service status (Unknown, Running, Down)	IP Core	Configuration
LDP Peers	Array of Label Distribution Protocol Peers	IP Core	Configuration

Label Distribution Protocol Peer

The following Label Distribution Protocol Peer object describes a remote LDP entity that currently has a LDP Session with a Local Label Distribution Protocol (LDP) Service to which it is bound by the latter's LDP Peer attribute.

Table 12-7 Label Distribution Protocol Peer (ILdpPeer) 

Attribute Name	Attribute Description	Scheme	Polling Interval
Peer Identification	Peer LDP identification	IP Core	Configuration
Transport Addresses	Peer transport IP addresses	IP Core	Configuration
Distribution Method	Label distribution method (Unknown, Downstream, Downstream On Demand)	IP Core	Configuration
Protocol Type	Peer protocol type (Unknown, LDP, TDP)	IP Core	Configuration
Path Vector Limit	Path vector limit for loop detection	IP Core	Configuration
Session Status	LDP session status type (Transient, Initialized, Open Received, Open Sent, Operational)	IP Core	Configuration
Protocol Version	LDP session protocol version	IP Core	Configuration
Hold Time	Hold time for maintaining the session without receiving traffic or keep alive	IP Core	Configuration
Hello Time Interval	Time interval in which hello (Keep Alive) packets should be sent	IP Core	Configuration
Peer Discovery Sources	Array of LDP Peer Discovery Sources	IP Core	Configuration

LDP Peer Discovery Source

The following LDP Peer Discovery Source object describes the discovery source of the Peer, which is done using broadcast on MPLS Interfaces and a Hello message exchanged between Label Switching Routers (LSRs).

Table 12-8 LDP Peer Discovery Source (ILdpPeerDiscoverySource)

Attribute Name	Attribute Description	Scheme	Polling Interval
Interface Name	MPLS interface name on where the peer was discovered	IP Core	Configuration
Source Addresses	Source IP Addresses from which the Hello message was sent	IP Core	Configuration
Type	Discovery Type (Link, Targeted)	IP Core	Configuration

Network Topology

The discovery of Multi Protocol Label Switching (MPLS) network layer topology is done by searching for the existence of the local IP subnet in any one hop away remote side's MPLS Interface. In particular a comparison is made between the local and remote IP subnets gathered from the upper IP network layers.

Service Alarms

The following alarms are supported for this technology:

•Broken LSP Discovered

•MPLS Black Hole Found/MPLS Black Hole Cleared

•MPLS Interface Removed/MPLS Interface Added

•LDP Neighbor Down/LDP Neighbor Up

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Note For a detailed description of these alarms and for information about correlation see the Cisco Active Network Abstraction MPLS User Guide.

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