Configuring MPLS-TP OAM for a Bidirectional Co-routed LSP
This section describes how to configure Multiprotocol Label Switching Transport Profile (MPLS-TP) operation, administration and maintenance (OAM) to monitor a static bidirectional co-routed LSP.
Usage Scenario
MPLS-TP has been widely used on transport networks. Traditional transport networks, such as synchronous digital hierarchy (SDH) and optical transport network (OTN) networks, have set high benchmarks for reliability and maintenance, and therefore MPLS-TP must provide powerful OAM capabilities.
MPLS-TP OAM can detect faults on bidirectional LSPs and collect performance statistics. On the network shown in Figure 11-3, the ingress label edge router (LER) is a maintenance entity group end point (MEP), the egress LER is the remote MEP (RMEP), and transit LERs are maintenance entity group intermediate points (MIPs). MPLS-TP OAM runs on the MEPs, providing continuity check, packet loss detection, and alarm suppression functions.
Pre-configuration Tasks
Configure a bidirectional LSP.
Enable packet statistics collection on a tunnel interface.
Creating an ME Instance and Binding It to a Tunnel Interface
This section describes how to create a maintenance entity (ME) instance and bind it to a tunnel interface. This is a prerequisite to configuring MPLS-TP OAM for LSP.
Context
Resource Reservation Protocol (RSVP) tunnels for transmitting traffic engineering (TE) services are unidirectional, and TE services are transmitted only from the ingress to the egress of a tunnel. To transmit TE services from the egress to the ingress of an RSVP tunnel, you can only use a route to forward the services, but that may cause network congestion. Additionally, if a path from the egress to the ingress is also configured as an RSVP tunnel, two tunnels are established between the ingress and egress. When a tunnel fails, the other tunnel cannot be notified of the fault. As a result, services will be interrupted. To resolve the preceding issue, configure a bidirectional LSP. Static bidirectional LSPs are supported.
Static bidirectional LSP: A static bidirectional LSP is similar to two LSPs in opposite directions. A static bidirectional LSP, however, is only one LSP. It is mapped to two forwarding entries for traffic in opposite directions and goes Up only when both forwarding entries are available. If the LSP is Down in one direction, the LSP is in the Down state. The two forwarding entries are associated with each other. When the IP forwarding capability is unavailable, any intermediate node can send back a response packet along the original path.
Static bidirectional LSPs supported by MPLS-TP can be monitored using MPLS-TP OAM. A MEG corresponds to a static bidirectional LSP and includes only one ME. The ingress and egress of the LSPs are configured as MEPs.
Two P2P LSPs in opposite directions are set up over a bidirectional co-routed transport path in a MEG. This means that there is a single LSP in both directions between a MEP and its RMEP. A single ME operates along this P2P LSP.
Perform the following steps on a MEP and its RMEP:
Procedure
- Run system-view
The system view is displayed.
- (Optional) Run mpls-tp channel-type {0x7ffa | 0x8902 }
An ACH label value is specified.
- Run mpls-tp meg meg-name
A MEG is created, and the MEG view is displayed.
- Run me te interface interface-type interface-number mep-id mep-id remote-mep-id remote-mep-id
An ME instance is created and is bound to a tunnel interface.
- Run commit
The configuration is committed.
(Optional) Configuring CC and CV for an LSP
This section describes how to configure continuity check (CC) and connectivity verification (CV) for an LSP.
Context
CC detects LOC on a link between any MEPs in a MEG. A MEP sends continuity check messages (CCMs) to its remote MEP (RMEP) at a specified interval. If the RMEP does not receive CCMs within a period of 3.5 times as long as the specified interval, the RMEP considers that the connectivity between the MEPs has errors, reports an alarm, and enters the Down state. After that, automatic protection switching (APS) is triggered on both MEPs. Upon receipt of a CCM from the MEP, the RMEP clears the alarm and exits from the Down state.
CV enables a MEP to report alarms when receiving unexpected packets. For example, if a CV-enabled device receives a packet from an LSP and finds that this packet is incorrectly transmitted through the LSP, the device will report an alarm indicating a forwarding error.
Transport networks have strict requirements on the correctness of data forwarding. In addition, MPLS-TP requires that the data plane should be able to work without IP support, which means that packet forwarding is based on label switching only. Therefore, the correctness of label-based forwarding must be ensured.
In practice, CC and CV are used together in the NE20E. The configurations for CC and CV are the same. Perform the following steps on a MEP and its RMEP:
Procedure
- Run system-view
The system view is displayed.
- Run mpls-tp meg meg-name
A MEG is created, and the MEG view is displayed.
- (Optional) Run either of the following commands:
Ensure that the same value is set on the MEP and RMEP; otherwise, an alarm will be generated.
To configure an interval at which CCMs are sent, run the cc interval interval-value command.
Optional CCM transmission intervals and their usage scenarios are as follows:- 3.3 ms: 300 frames are sent per second. This interval is recommended for protection switching.
- 10 ms: 100 frames are sent per second.
- 100 ms: 10 frames are sent per second. This interval is recommended for performance monitoring.
- 1000 ms: 1 frame is sent per second. This interval is recommended for fault management.
- 10000 ms: 6 frames are sent per minute.
- 60000 ms: 1 frame is sent per minute.
- 600000 ms: 6 frames are sent per hour.
To configure a priority for CCMs, run the cc exp exp-value command.
If the MPLS-TP network is severely congested and the priority of CCMs is low, CCMs fail to be sent. Therefore, configure an appropriate priority for CCMs according to network conditions.
- (Optional) On the local MEP, run rdi disable
RDI is disabled.
RDI is enabled by default.
If an MEP detects a defect or fault, the RDI flag is set to 1 in CCMs. The MEP then sends the CCMs to the RMEP to notify it of the defect or fault.
- Perform the following steps to enable CC and CV on the MEP and RMEP (this operation sequence prevents alarm misreports during the enabling process):
- Run the cc send enable command on the MEP to enable the MEP to send CCMs.
- Run the cc send enable command on the RMEP to enable the RMEP to send CCMs.
- Run the cc receive enable command on the MEP to enable the MEP to receive CCMs.
- Run the cc receive enable command on the RMEP to enable the RMEP to receive CCMs.
(Optional) Configuring LB for an LSP
This section describes how to configure loopback (LB) to monitor the connectivity of MPLS-TP links.
Context
LB is the most common tool that monitors the connectivity between MEPs or between a MEP and a MIP. Unlike CC or CV that is performed periodically, LB is performed at a time.
- Availability of a remote device
- Round-trip delay in communication between MEPs
- Loss of ping packets
Item |
Loopback enabled using the ping meg command |
CC enabled using the cc enable command |
|---|---|---|
Configuration procedure |
To enable loopback, perform the following step: Run the ping meg command on a MEP to enable loopback and display statistics in real time. |
To enable CC, perform the following steps:
|
Statistics display |
The ping meg command displays statistics on the MEP. |
An alarm is generated and reported if a connectivity fault between the MEP and its RMEP occurs. |
Detection method |
On-demand monitoring: monitors connectivity of a MEG at a time. |
Proactive monitoring: periodically monitors connectivity of a MEG. |
Detection object |
MEP or MIP |
MEP |
Procedure
- Run ping meg meg-name [ { mip ttl ttl-number { mip-id mip-id-value | node-id node-id value } [ if-num if-numvalue ] } | -c count-value | packet-size size-value | -t timeout-value ] * [ request-tlv ]
LB is enabled to monitor the connectivity of an MPLS-TP link.
The timeout-value parameter specifies a period for waiting for a response packet.
If the network speed is slow, set the timeout-value parameter to a large value in the ping meg command.
(Optional) Configuring Frame LM
This section describes how to configure frame loss measurement (LM) for MPLS-TP services.
Context
- Near-end frame loss data: indicates the number and percentage of lost frames that are sent from an RMEP to a MEP.
- Far-end frame loss: indicates the number and percentage of dropped frames that are sent from a MEP to an RMEP.
Item |
Single-ended Frame LM |
Dual-ended Frame LM |
|---|---|---|
Statistics display |
Statistics can be displayed using either of the following commands on a MEP:
|
Statistics about dual-ended frame LM can be displayed using the display mpls-tp oam meg meg-name statistic-type lost-measure dual-ended command on a MEP. |
Monitoring scenario |
On-demand monitoring Proactive monitoring |
Proactive monitoring |
All the steps must be performed on both the MEP and RMEP unless otherwise specified.
Procedure
- Run system-view
The system view is displayed.
- Run mpls-tp meg meg-name
A MEG is created, and the MEG view is displayed.
- Choose one of the following sub-procedures as needed:
- Configure single-ended frame LM.
- Run lost-measure single-ended receive enable
The RMEP is enabled to receive LMMs from the MEP.
Perform either of the following steps:
- Run lost-measure single-ended [ count count-value | exp exp-value | interval interval-value ]*
Single-ended on-demand frame LM is enabled on the MEP.
- Run lost-measure single-ended proactive [ interval interval-value | exp exp-value ] *
Single-ended proactive frame LM is enabled on the MEP.
- Run lost-measure single-ended [ count count-value | exp exp-value | interval interval-value ]*
- Run lost-measure single-ended receive enable
- Configure dual-ended frame LM.
(Optional) Run cc interval interval-value
An interval at which CCMs are sent is configured.
Typical CCM transmission intervals and their application scenarios are as follows:- 3.3 ms: 300 frames are sent per second. This interval is recommended for protection switching.
- 100 ms: 10 frames are sent per second. This interval is recommended for performance monitoring.
- 1000 ms: 1 frame is sent per second. This interval is recommended for fault management.
(Optional) Run cc exp exp-value
A priority is configured for CCMs.If the MPLS-TP network is severely congested and the priority of CCMs is low, CCMs fail to be sent. Therefore, configure an appropriate priority for CCMs according to network conditions.
- On the MEP, run cc send enable
The MEP is enabled to send CCMs.
- On the RMEP, run cc send enable
The RMEP is enabled to send CCMs.
- On the MEP, run cc receive enable
The MEP is enabled to receive CCMs.
- On the RMEP, run cc receive enable
The RMEP is enabled to receive CCMs.
- Run lost-measure dual-ended enable
Dual-ended frame LM is enabled.
- Configure single-ended frame LM.
(Optional) Configuring Frame DM
This section describes how to configure one- and two-way frame delay measurement (DM) to collect reliability statistics for MPLS-TP services.
Context
- One-way frame DM: In a point-to-point ME, a MEP sends DM frames to its RMEP to carry out one-way frame delay and variation measurement.
If the clocks of the two MEPs are synchronized, one-way frame DM can be conducted; otherwise, only two-way frame delay variation can be measured.
- Two-way frame DM: In a point-to-point ME, a MEP sends delay measurement messages (DMMs) to its RMEP and receives delay measurement replies (DMRs) from the RMEP to carry out two-way frame delay and variation measurement.
Item |
One-Way Frame DM |
Two-Way Frame DM |
|---|---|---|
Statistics display |
Statistics about one-way frame DM can be displayed using the display mpls-tp oam meg meg-name statistic-type delay-measure one-way command on an RMEP. |
Statistics can be displayed using either of the following commands on a MEP:
|
Monitoring scenario |
On-demand monitoring Proactive monitoring |
On-demand monitoring Proactive monitoring |
All the steps must be performed on both the MEP and RMEP unless otherwise specified.
Procedure
- Run system-view
The system view is displayed.
- Run mpls-tp meg meg-name
A MEG is created, and the MEG view is displayed.
- Choose one of the following sub-procedures as needed:
Configure one-way frame DM. Run any of the following commands:
Run delay-measure one-way [ interval interval-value | count count-value | exp exp-value ] *
One-way on-demand frame DM is enabled.
Run either of the following commands to view statistics about one-way on-demand frame DM as needed:
- If the delay-measure one-way command has been run on the MEP to measure the delay on the link from the MEP to the RMEP, run the display mpls-tp oam meg meg-name statistic-type delay-measure one-way command on the RMEP to view DM results.
- If the delay-measure one-way command has been run on the RMEP to measure the delay on the link from the RMEP to the MEP, run the display mpls-tp oam meg meg-name statistic-type delay-measure one-way command on the MEP to view DM results.
On the MEP, run delay-measure one-way proactive [ interval interval-value | exp exp-value ] *
One-way proactive frame DM is enabled.
On the RMEP, run delay-measure one-way proactive receive enable
The receive function is enabled for one-way proactive frame DM.
Run either of the following commands to view statistics about one-way proactive frame DM as needed:
- If the delay-measure one-way proactive command has been run on the MEP, run the display mpls-tp oam meg meg-name statistic-type delay-measure one-way command on the RMEP to view statistics about one-way proactive frame DM in the direction from the MEP to its RMEP.
- If the delay-measure one-way proactive command has been run on the RMEP, run the display mpls-tp oam meg meg-name statistic-type delay-measure one-way command on the MEP to view statistics about one-way proactive frame DM in the direction from the RMEP to its MEP.
Configure two-way frame DM. Configure either two-way on-demand or proactive frame DM as follows:
To enable two-way on-demand frame DM, run the delay-measure two-way [ interval {1000|10000} | count count-value | exp exp-value | two-time-stamp ] * command.
To enable two-way proactive frame DM, run the delay-measure two-way proactive [ interval { 1000 | 10000 } | exp exp-value ] * command.
Verifying the Configuration of MPLS-TP OAM for an LSP
After configuring Multiprotocol Label Switching Transport Profile (MPLS-TP) operation, administration and maintenance (OAM) for a label switched path (LSP), verify the configurations by querying performance statistics and fault detection information.
Procedure
- Run the display mpls-tp oam current-alarm command to check alarms associated with a MEG.
- Run the display mpls-tp oam me brief command to check information about maintenance entities (MEs) in a MEG.
- Run the display mpls-tp oam meg command to check MEG information on the MEP.
- Run the display mpls-tp oam meg meg-name statistic-type command to check MPLS-TP OAM performance statistics.
