Contents

Configuring CFD·· 1

About CFD·· 1

Basic CFD concepts· 1

CFD levels· 1

Packet processing of MPs· 3

CFD functions· 3

Protocols and standards· 4

Restrictions and guidelines: CFD configuration· 4

CFD tasks at a glance· 5

Prerequisites for CFD·· 5

Configuring basic CFD settings· 5

Enabling CFD·· 5

Configuring service instances· 5

Configuring MEPs· 6

Configuring CFD functions· 6

Configuring CC· 6

Configuring one-way LM·· 8

Configuring two-way DM·· 8

Verifying and maintaining CFD·· 9

Verifying CFD configuration and running status· 9

Displaying and clearing CFD test results· 10

CFD configuration examples· 10

Example: Configuring CFD in a Layer 2 VPN (L2VPN networking) 10

Configuring CFD

About CFD

Connectivity Fault Detection (CFD), which conforms to IEEE 802.1ag Connectivity Fault Management (CFM), is an end-to-end link layer OAM mechanism. CFD is used for link connectivity detection, fault verification, and fault location in Layer 2 networks.

Basic CFD concepts

Maintenance domain

A maintenance domain (MD) defines the network or part of the network where CFD plays its role. An MD is identified by its MD name.

Maintenance association

A maintenance association (MA) is a part of an MD. You can configure multiple MAs in an MD as needed. An MA is identified by the MD name + MA name.

In an MPLS Layer 2 VPN, an MA can only serve the specified cross-connect.

Maintenance point

An MP is configured on a port and belongs to an MA. MPs include the following types: maintenance association end points (MEPs) and maintenance association intermediate points (MIPs).

MEPs define the boundary of the MA. Each MEP is identified by a MEP ID.

In an MPLS Layer 2 VPN, the MA to which a MEP belongs defines the cross-connect or VSI of packets sent by the MEP.

MEPs include inward-facing MEPs and outward-facing MEPs:

·     An inward-facing MEP does not send packets to its host port. Rather, it sends packets to other ports on the device. In an MPLS Layer 2 VPN, the packets are broadcast in the cross-connect to which the MEP belongs.

·     An outward-facing MEP sends packets to its host port.

MEP list

A MEP list is a collection of local MEPs allowed to be configured and the remote MEPs to be monitored in the same MA. It lists all the MEPs configured on different devices in the same MA. The MEPs all have unique MEP IDs. When a MEP receives from a remote device a continuity check message (CCM) carrying a MEP ID not in the MEP list of the MA, it drops the message.

The local device must send CCM messages carrying the Remote Defect Indication (RDI) flag bits. Otherwise, the peer device cannot sense certain failures. When a local MEP has not learned all remote MEPs in the MEP list, the MEPs in the MA might not carry the RDI flag bits in CCMs.

CFD levels

MD levels

To accurately locate faults, CFD introduces eight levels (from 0 to 7) to MDs. The bigger the number, the higher the level and the larger the area covered. Domains can touch or nest (if the outer domain has a higher level than the nested one) but cannot intersect or overlap.

MD levels facilitate fault location and make fault location more accurate. As shown in Figure 1, MD_A in light blue nests MD_B in dark blue. If a connectivity fault is detected at the boundary of MD_A, any of the devices in MD_A, including Device A through Device E, might fail. If a connectivity fault is also detected at the boundary of MD_B, the failure points can be any of Device B through Device D. If the devices in MD_B can operate correctly, at least Device C is operational.

 

NOTE: This section assumes that physical links between devices are in good condition.

 

Figure 1 Two nested MDs

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CFD exchanges messages and performs operations on a per-domain basis. By planning MDs correctly in a network, you can use CFD to rapidly locate failure points.

MA and MP levels

The level of an MA equals the level of the MD to which the MA belongs.

The level of a MEP equals the level of the MD to which the MEP belongs.

CFD grading example

Figure 2 demonstrates a grading example of the CFD module. Four levels of MDs (0, 2, 3, and 5) are designed. The bigger the number, the higher the level and the larger the area covered. MPs are configured on the ports of Device A through Device F. Port A of Device B is configured with the following MPs:

·     A level 5 MIP.

·     A level 3 inward-facing MEP.

·     A level 2 inward-facing MEP.

·     A level 0 outward-facing MEP.

Figure 2 CFD grading example

 

Packet processing of MPs

A MEP forwards packets at a higher level without any processing and only processes packets of its level or lower.

CFD functions

CFD functions, which are implemented through the MPs, include:

·     Continuity check (CC).

·     Loss measurement (LM).

·     Delay measurement (DM).

Continuity check

Connectivity faults are usually caused by device faults or configuration errors. Continuity check examines the connectivity between MEPs. This function is implemented through periodic sending of CCMs by the MEPs. A CCM sent by one MEP is intended to be received by all the other MEPs in the same MA. If a MEP fails to receive the CCMs within 3.5 times the sending interval, the link is considered as faulty and a log is generated. When multiple MEPs send CCMs at the same time, the multipoint-to-multipoint link check is achieved. CCM frames are multicast frames.

LM

The loss measurement (LM) function measures the frame loss between a pair of MEPs.

In one-way LM, the source MEP sends loss measurement messages (LMMs) to the target MEP. The target MEP responds with loss measurement replies (LMRs). The source MEP calculates the number of lost frames according to the counter values of the two consecutive LMRs (the current LMR and the previous LMR). LMMs and LMRs are unicast frames.

The one-way LM function can be implemented in one of the following ways:

·     Short-period LM—The source MEP sends a configurable number of LMMs at a configurable interval. The test result is printed when the test ends.

·     Continual LM—The source MEP continually sends LMMs at a configurable interval until continual LM is administratively disabled. To view the test result, use the display cfd slm history command on the target MEP.

DM

The DM function measures frame delays between two MEPs, including the following types:

·     One-way frame delay measurement

The source MEP sends a one-way delay measurement (1DM) frame, which carries the transmission time, to the target MEP. When the target MEP receives the 1DM frame, it does the following:

¡     Records the reception time.

¡     Calculates and records the link transmission delay and jitter (delay variation) according to the transmission time and reception time.

1DM frames are unicast frames.

The one-way DM function can be implemented in one of the following ways:

¡     Short-period DM—The source MEP sends a configurable number of 1DM frames at a configurable interval. To view the test result, use the display cfd dm one-way history command on the target MEP.

¡     Continual DM—The source MEP continually sends 1DM frames at a configurable interval until continual DM is administratively disabled. To view the test result, use the display cfd dm one-way history command on the target MEP.

·     Two-way frame delay measurement

The source MEP sends a delay measurement message (DMM), which carries the transmission time, to the target MEP. When the target MEP receives the DMM, it responds with a delay measurement reply (DMR). The DMR carries the reception time and transmission time of the DMM and the transmission time of the DMR. When the source MEP receives the DMR, it does the following:

¡     Records the DMR reception time.

¡     Calculates the link transmission delay and jitter according to the DMR reception time and DMM transmission time.

DMM frames and DMR frames are unicast frames.

The two-way DM function can be implemented in one of the following ways:

¡     Short-period two-way DM—The source MEP sends a configurable number of DMMs at a configurable interval.

¡     Continual two-way DM—The source MEP continually sends DMMs at a configurable interval until continual two-way DM is administratively disabled. To view the test result, use the display cfd dm two-way history command on the target MEP.

Protocols and standards

·     IEEE 802.1ag, Virtual Bridged Local Area Networks Amendment 5: Connectivity Fault Management

Restrictions and guidelines: CFD configuration

When you configure CFD, configure CC before you use the MEP ID of the remote MEP to configure other CFD functions. This restriction does not apply when you use the MAC address of the remote MEP to configure other CFD functions.

CFD tasks at a glance

To configure CFD, perform the following tasks:

1.     Configuring basic CFD settings

a.     Enabling CFD

b.     Configuring service instances

c.     Configuring MEPs

2.     Configuring CFD functions

a.     Configuring CC

b.     (Optional.) Configuring one-way LM

c.     (Optional.) Configuring two-way DM

Prerequisites for CFD

For CFD to work correctly, design the network by performing the following tasks:

·     Grade the MDs in the entire network, and define the boundary of each MD.

·     Assign a name for each MD. Make sure the devices in the same MD use the same MD name.

·     Define the MA in each MD according to the VLAN, cross-connect, or VSI you want to monitor.

·     Assign a name for each MA. Make sure that the devices in the same MA in the same MD use the same MA name.

·     Determine the MEP list of each MA in each MD. Make sure devices in the same MA maintain the same MEP list.

Configuring basic CFD settings

Enabling CFD

1.     Enter system view.

system-view

2.     Enable CFD.

cfd enable

By default, CFD is disabled.

Configuring service instances

About this task

Before configuring the MEPs and MIPs, you must first configure service instances. A service instance is a set of service access points (SAPs), and belongs to an MA in an MD.

In an MPLS Layer 2 VPN, the MD and MA define the level attribute and cross-connect or VSI attribute of the messages handled by the MEPs in a service instance.

Procedure

1.     Enter system view.

system-view

2.     Create an MD.

cfd md md-name [ index index-value ] level level-value [ md-id { dns dns-name | mac mac-address subnumber | none } ]

3.     Create a service instance.

cfd service-instance instance-id ma-id { icc-based ma-name | integer ma-num | string ma-name } [ ma-index index-value ] md md-name xconnect-group group-name connection connection-name

Configuring MEPs

About this task

CFD is implemented through various operations on MEPs. As a MEP is configured on a service instance, the MD level and VLAN attribute or cross-connect or VSI attribute of the service instance become the attributes of the MEP.

Restrictions and guidelines

You can specify an interface as the MEP for only one of the non-VLAN-specific MAs at the same level. In addition, the MEP must be outward facing.

If a MEP in a non-VLAN-specific MA does not receive a CCM message within 3.5 CCM intervals from a remote MEP, the local MEP sets its interface to link down state. This behavior of the local MEP facilitates fast switchover for Smart Link.

Prerequisites

Before you configure MEPs, you must configure service instances.

Configuring MEPs in an MPLS Layer 2 VPN

1.     Enter system view.

system-view

2.     Configure a MEP list.

cfd meplist mep-list service-instance instance-id

The created MEP must be included in the configured MEP list.

3.     Enter interface view.

¡     Enter Layer 3 Ethernet interface view.

interface interface-type interface-number

¡     Enter Layer 3 Ethernet subinterface view.

interface interface-type interface-number.subnumber

4.     Create a MEP.

cfd mep mep-id service-instance instance-id inbound

 

Configuring CFD functions

Configuring CC

About this task

After the CC function is configured, MEPs in an MA can periodically send CCM frames to maintain connectivity.

You must configure CC before you use the MEP ID of the remote MEP to configure other CFD functions. This restriction does not apply when you use the MAC address of the remote MEP to configure other CFD functions.

When the lifetime of a CCM frame expires, the link to the sending MEP is considered disconnected. When setting the CCM interval, use the settings described in Table 1.

Table 1 CCM interval field encoding

CCM interval field	Transmission interval	Maximum CCM lifetime
1	10/3 milliseconds	35/3 milliseconds
2	10 milliseconds	35 milliseconds
3	100 milliseconds	350 milliseconds
4	1 second	3.5 seconds
5	10 seconds	35 seconds
6	60 seconds	210 seconds
7	600 seconds	2100 seconds

 

	NOTE: ·     The value range for the interval field is 1 to 7. If you set the value to 1, the continuity check might work incorrectly due to hardware restrictions. ·     The CCM messages with an interval field value of 1 to 3 are short-interval CCM messages. The CCM messages with an interval field value of 4 to 7 are long-interval CCM messages.

 

Restrictions and guidelines

When you configure the CCM interval, follow these restrictions and guidelines:

·     Configure the same CCM interval field value for all MEPs in the same MA.

·     After the CCM interval field is modified, the MEP must wait for another CCM interval before sending CCMs.

Configuring CC in an MPLS Layer 2 VPN

1.     Enter system view.

system-view

2.     (Optional.) Set the CCM interval field.

cfd cc interval interval-value service-instance instance-id

By default, the interval field value is 4.

3.     Enter interface view.

¡     Enter Layer 3 Ethernet interface view.

interface interface-type interface-number

¡     Enter Layer 3 Ethernet subinterface view.

interface interface-type interface-number.subnumber

4.     Enable CCM sending on a MEP.

cfd cc service-instance instance-id mep mep-id enable

By default, CCM sending is disabled on a MEP.

5.     (Optional.) Enable hardware CC for remote MEPs.

cfd hardware-cc service-instance instance-id remote-mep mep-list

By default, hardware CC is disabled for a remote MEP.

Configuring one-way LM

About this task

The one-way LM function measures frame loss between MEPs. Frame loss statistics include the number of lost frames, the frame loss ratio, and the average number of lost frames for the source and target MEPs.

Restrictions and guidelines

To configure one-way LM in a Layer 2 VPN, first configure the same frame counting mode on the source MEP and target MEP.

Configuring the frame counting mode

1.     Enter system view.

system-view

2.     Enter interface view.

¡     Enter Layer 3 Ethernet interface view.

interface interface-type interface-number

¡     Enter Layer 3 Ethernet subinterface view.

interface interface-type interface-number.subnumber

3.     Configure the frame counting mode.

cfd frame-count mode { dot1p-based | port-based }

By default, no frame counting mode is configured for LM.

This command takes effect only in Layer 2 VPNs.

 

Configuring short-period LM

To configure short-period LM, execute the following command in any view:

cfd slm service-instance instance-id mep mep-id { target-mac mac-address | target-mep target-mep-id } [ dot1p dot1p-value ] [ number number ] [ interval { interval | msec msec-interval } ]

Configuring continual LM

1.     Enter system view.

system-view

2.     Configure continual LM.

cfd slm continual service-instance instance-id mep mep-id { target-mac mac-address | target-mep target-mep-id } [ dot1p dot1p-value ] [ interval { interval | msec msec-interval }][ period period ]

By default, continual LM is not configured.

Configuring two-way DM

About this task

The two-way DM function measures the two-way frame delay, average two-way frame delay, and two-way frame delay variation between two MEPs. It also monitors and manages the link transmission performance.

Configuring short-period two-way DM

To configure two-way DM, execute the following command in any view:

cfd dm two-way service-instance instance-id mep mep-id { target-mac mac-address | target-mep target-mep-id } [ dot1p dot1p-value ] [ number number ] [ interval interval ]

Configuring continual two-way DM

1.     Enter system view.

system-view

2.     Configure continual two-way DM.

cfd dm two-way continual service-instance instance-id mep mep-id { target-mac mac-address | target-mep target-mep-id } [ dot1p dot1p-value ] [ interval interval ]

By default, continual two-way DM is not configured.

Verifying and maintaining CFD

Verifying CFD configuration and running status

Verifying basic CFD configuration

Perform display tasks in any view.

·     Display CFD status.

display cfd status

·     Display MD configuration information.

display cfd md

·     Display service instance configuration.

display cfd service-instance [ instance-id ]

Verifying MP configuration and running status

Perform display tasks in any view.

·     Display MP information.

display cfd mp [ interface interface-type interface-number ]

·     Display the attribute and running information of a MEP.

display cfd mep mep-id service-instance instance-id

·     Display information about a remote MEP.

display cfd remote-mep service-instance instance-id mep mep-id

·     Display the MEP list in a service instance.

display cfd meplist [ service-instance instance-id ]

Displaying CFD packet information

Perform display tasks in any view.

·     Display LTR information received by a MEP.

display cfd linktrace-reply [ service-instance instance-id [ mep mep-id ] ]

·     Display the content of the LTR messages received as responses to the automatically sent LTMs.

display cfd linktrace-reply auto-detection [ size size-value ]

Displaying and clearing CFD test results

Displaying CFD test results

Perform display tasks in any view.

·     Display the two-way DM result on the specified MEP.

display cfd dm two-way history [ service-instance instance-id [ mep mep-id ] ] [ number number ]

·     Display the LM result on the specified MEP.

display cfd slm history [ service-instance instance-id [ mep mep-id ] ] [ number number ]

CFD configuration examples

Example: Configuring CFD in a Layer 2 VPN (L2VPN networking)

Network configuration

As shown in Figure 3:

·     Configure a static PW between PE 1 and PE 2 to enable CE 1 and CE 2 to communicate with each other. Assume that the MAC addresses of Device A through Device D are 0010-FC01-6511, 0010-FC02-6512, 0010-FC03-6513, and 0010-FC04-6514, respectively.

·     Configure HundredGigE 1/0/1.1 on Device A and Device B as AC interfaces, and associate them with cross-connect svc of cross-connect group vpna.

·     Assign the network to MD_A (level 5). MD_A has two edge interfaces: HundredGigE 1/0/1.1 on Device A and HundredGigE 1/0/1.1 on Device B. They are both inward-facing MEPs.

·     Configure CC to monitor the connectivity between the inward-facing MEPs. Configure LB to locate link faults.

·     After the status information of the entire network is obtained, use LT, LM, and DM to detect link faults.

Figure 3 Network diagram

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Procedure

1.     Configure a static PW. (Details not shown.)

For information about configuring a static PW, see MPLS L2VPN in MPLS Configuration Guide.

2.     Enable CFD:

# Enable CFD on Device A.

<DeviceA> system-view

[DeviceA] cfd enable

# Configure Device B in the same way Device A is configured. (Details not shown.)

3.     Configure service instances:

# Create MD_A (level 5) on Device A, and create service instance 1 (in which the MA is identified by vpnma and serves cross-connect svc of cross-connect group vpna).

[DeviceA] cfd md MD_A level 5

[DeviceA] cfd service-instance 1 ma-id string vpnma md MD_A xconnect-group vpna connection svc

# Configure Device B in the same way Device A is configured. (Details not shown.)

4.     Configure MEPs:

# On Device A, configure a MEP list in service instance 1, and create inward-facing MEP 1001 in service instance 1 on HundredGigE 1/0/1.1.

[DeviceA] cfd meplist 1001 2001 service-instance 1

[DeviceA] interface hundredgige 1/0/1.1

[DeviceA-HundredGigE1/0/1.1] cfd mep 1001 service-instance 1 inbound

[DeviceA-HundredGigE1/0/1.1] quit

# On Device B, configure a MEP list in service instance 1, and create inward-facing MEP 2001 in service instance 1 on HundredGigE 1/0/1.1.

[DeviceB] cfd meplist 1001 2001 service-instance 1

[DeviceB] interface hundredgige 1/0/1.1

[DeviceB-HundredGigE1/0/1.1] cfd mep 2001 service-instance 1 inbound

[DeviceB-HundredGigE1/0/1.1] quit

5.     Configure CC:

# On Device A, enable the sending of CCM frames for MEP 1001 in service instance 1 on HundredGigE 1/0/1.1.

[DeviceA] interface hundredgige 1/0/1.1

[DeviceA-HundredGigE1/0/1.1] cfd cc service-instance 1 mep 1001 enable

[DeviceA-HundredGigE1/0/1.1] quit

# On Device B, enable the sending of CCM frames for MEP 2001 in service instance 1 on HundredGigE 1/0/1.1.

[DeviceB] interface hundredgige 1/0/1.1

[DeviceB-HundredGigE1/0/1.1] cfd cc service-instance 1 mep 2001 enable

[DeviceB-HundredGigE1/0/1.1] quit

6.     Configure the frame counting mode:

# Configure the frame counting mode as port-based for HundredGigE 1/0/1.1 on Device A.

[DeviceA] interface hundredgige 1/0/1.1

[DeviceA-HundredGigE1/0/1.1] cfd frame-count mode port-based

[DeviceA-HundredGigE1/0/1.1] quit

# Configure the frame counting mode as port-based for HundredGigE 1/0/1.1 on Device B.

[DeviceB] interface hundredgige 1/0/1.1

[DeviceB-HundredGigE1/0/1.1] cfd frame-count mode port-based

[DeviceB-HundredGigE1/0/1.1] quit

Verifying the configuration

1.     Verify the one-way LM function after the CC function obtains the status information of the entire network:

# Use short-period LM to test the frame loss from MEP 1001 to MEP 2001 in service instance 1 on Device A.

[DeviceA] cfd slm service-instance 1 mep 1001 target-mep 2001

Reply from 0010-fc02-6512:

Far-end frame loss : 10                   Far-end frame loss rate : 10.00%

Near-end frame loss: 20                   Near-end frame loss rate: 20.00%

Reply from 0010-fc02-6512:

Far-end frame loss : 40                   Far-end frame loss rate : 40.00%

Near-end frame loss: 40                   Near-end frame loss rate: 40.00%

Reply from 0010-fc02-6512:

Far-end frame loss : 0                    Far-end frame loss rate : 0.00%

Near-end frame loss: 10                   Near-end frame loss rate: 10.00%

Reply from 0010-fc02-6512:

Far-end frame loss : 30                   Far-end frame loss rate : 30.00%

Near-end frame loss: 30                   Near-end frame loss rate: 30.00%

Average:

Far-end frame loss : 20                   Far-end frame loss rate : 20.00%

Near-end frame loss: 25                   Near-end frame loss rate: 25.00%

Packet statistics:

Sent LMMs: 5    Received: 5

# Use continual LM to test the frame delay from MEP 1001 to MEP 2001 in service instance 1 on Device A.

[DeviceA] cfd slm continual service-instance 1 mep 1001 target-mep 2001

# Display the one-way LM result on MEP 1001 in service instance 1 on Device A.

[DeviceA] display cfd slm history service-instance 1 mep 1001

Service instance: 1

MEP ID: 1001

Send status: Testing

Test state: Active

Reply from 0010-fc02-6512:

Far-end frame loss : 10                   Far-end frame loss rate : 10.00%

Near-end frame loss: 20                   Near-end frame loss rate: 20.00%

Reply from 0010-fc02-6512:

Far-end frame loss : 40                   Far-end frame loss rate : 40.00%

Near-end frame loss: 40                   Near-end frame loss rate: 40.00%

Reply from 0010-fc02-6512:

Far-end frame loss : 0                    Far-end frame loss rate : 0.00%

Near-end frame loss: 10                   Near-end frame loss rate: 10.00%

Reply from 0010-fc02-6512:

Far-end frame loss : 30                   Far-end frame loss rate : 30.00%

Near-end frame loss: 30                   Near-end frame loss rate: 30.00%

Reply from 0010-fc02-6512:

Far-end frame loss : 20                   Far-end frame loss rate : 20.00%

Near-end frame loss: 25                   Near-end frame loss rate: 25.00%

Average:

Far-end frame loss : 20                   Far-end frame loss rate : 20.00%

Near-end frame loss: 25                   Near-end frame loss rate: 25.00%

Packet statistics:

Sent LMMs: 100    Received: 100

2.     Verify the two-way DM function after the CC function obtains the status information of the entire network:

# Use short-period DM to test the two-way frame delay from MEP 1001 to MEP 2001 in service instance 1 on Device A.

[DeviceA] cfd dm two-way service-instance 1 mep 1001 target-mep 2001

Frame delay:

Reply from 0010-fc02-6512: 10us

Reply from 0010-fc02-6512: 9us

Reply from 0010-fc02-6512: 11us

Reply from 0010-fc02-6512: 5us

Reply from 0010-fc02-6512: 5us

Average: 8us

Frame delay variation: 1us 2us 6us 0us

Average: 2us

Packet statistics:

Sent DMMs: 5        Received: 5        Lost: 0

# Use continual DM to test the frame delay from MEP 1001 to MEP 2001 in service instance 1 on Device A.

[DeviceA] cfd dm one-way continual service-instance 1 mep 1001 target-mep 2001

# Display the two-way DM result on MEP 1001 in service instance 1 on Device A.

[DeviceA] display cfd dm two-way history service-instance 1 mep 1001

Service instance: 1

MEP ID: 1001

Send status: Testing

Test state: Active

Frame delay:

Reply from 0010-fc02-6512: 10us

Reply from 0010-fc02-6512: 9us

Reply from 0010-fc02-6512: 11us

Reply from 0010-fc02-6512: 5us

Reply from 0010-fc02-6512: 5us

Average: 8us

Frame delay variation: 1us 2us 6us 0us

Average: 2us

Packet statistics:

Sent DMMs: 5        Received: 5        Lost: 0