FSP 150CC-GE20x Product Training Course 8 - CFM & Y.1731
FSP 150CC-GE206 R4.4.x FSP 150CC-GE201 R4.3.x
October 2010 V1.3
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Module Contents
Connectivity Fault Management (CFM)
Y.1731
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Connectivity Fault Management
Connectivity Fault Management is an emerging standard aimed at enhancing Ethernet service OAM capability CFM is defined by IEEE 802.1ag and ITU-T Y.1731 (with extended
functionality)
The main features provided by CFM include the ability to detect, verify, isolate and report connectivity faults on a service instance
The FSP 150CC-GE206 supports the following features Configure Maintenance Domain
Configure Maintenance Associations
Configure and manage Maintenance Points (MEP and MIP)
Transmit and receive Continuity Check Messages
Initiate and respond to Link Trace and Loopback Messages
Detect and raise CFM related alarms
Y.1731 Ethernet AIS
Y.1731 Performance Monitoring (Loss and Delay Measurement)
CFM based Link Loss Forwarding
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Connectivity Fault Management (CFM) Overview
A Maintenance Domain (MD) is a bridged network maintained by an operator
Each MD is assigned a Maintenance Domain Level (0-7)
Multiple domains at different levels create a hierarchy of MDs
A Maintenance Association (MA) represents the service instance being monitored
It consists of two or more MEPs which define the boundary of the MA
Maintenance Points
can be created at port and VLAN level
Maintenance End Point (MEP)
At the boundary of a Maintenance Association
initiate and respond to CFM messages
Maintenance Intermediate Point (MIP)
MIPs receive and respond to messages.
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Customer Domain
Service Provider Domain
Operator Domain
Operator A Provider Bridges Operator B Provider Bridges CPE CPE
MD Level=5
MD Level=3
MD Level=2
Operator Domain
MEP MIP MA
Connectivity Fault Management (CFM) Overview
Up MEP – CFM traffic is sent towards the bridge (e.g. from LAN towards WAN through the device)
Down MEP – CFM traffic is sent away from the bridge (e.g. from WAN towards the network)
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Connectivity Fault Management (CFM) Maintenance Domain Hierarchy
MIPs at a higher level are MEPs at a lower level
Higher domain subscribes to service of lower domain
Maintenance level restricts visibility upward and downward in hierarchy
Network topology of Provider is not visible to customer.
Similarly, Provider cannot see Operator’s network topology.
Higher level can only see what lower level allows to be seen
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Feature Overview CFM – MEP Directionality
“Up” means CFM traffic sent towards the bridge
“Down” means CFM traffic sent away from the bridge
On the FSP 150CC, the bridge functionality is implemented in the FPGA
GE206 Supports:
Client ports:
VLAN-based up and down-MEPs on client ports
Port-based down-MEPs on client ports
Network ports:
Port-based down-MEPs on network ports
VLAN-based down-MEPs on network ports
LAN WAN
Down MEP
CFM Traffic
Up MEP
CFM Traffic
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Connectivity Fault Management (CFM) CFM Messages
The standard defines a set of CFM messages along with supporting protocols and procedures
CFM messages are used for monitoring and managing the connectivity between the maintenance points in a MA
CFM messages include:
Continuity Check messages (CCM)
Link Trace messages (LTM)
Loopback messages (LBM)
Y.1731
Alarm Indication Signal (AIS)
Delay Measurement Messages (DMM)
Loss Measurement Message (LMM)
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Periodic multicast message toward other MEPs in the same MA Provides heartbeat for connectivity check
Also used for MEP MAC discovery
CCM contains: Source MAC Address, Maintenance Level, MA ID, MEP ID, Sequence #
RDI bit indicates CCM from a MEP has not been received
CCM MEP receiver: Checks for valid CCM data (maintenance level, MAID, MEPID, etc)
Monitors for missing MEP IDs
Populates CCM database
CCM Interval 3.3 msec
10 msec
100 msec
1 sec
10 sec
1 min
10 min
Connectivity Fault Management (CFM) Continuity Check Messages (CCM)
B
A D
Provider Domain
Operator B Operator A
MEP MIP MA
C
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Some RDI Received a CCM from one or more MEPs with the RDI bit set
A MEP will set the RDI bit if it has detected one or more of the following defects
Some MAC Status One or more remote MEPs sent CCM with interface status TLV
(Type/Length/Value tuple) indicating its interface is not up
All remote MEPs sent CCM with port status TLV indicating its port is not up
Some Remote MEP CCM Defect is raised if no CCM received for one or more remote MEPs in the MA for 3
consecutive intervals. If the defect persists for 2.5 secs, the alarm is raised.
Erroneous CCM: CCM received from MEP not configured in the MA
A CCM is from a MEP with the same MEP ID as the receiving MEP
The CCM interval of a received CCM does not match the receiving MEP’s MA value.
Crossconnect CCM: The MA ID does not match the MAID of the receiving MEP
The MD is less than the level of the receiving MEP’s level
Connectivity Fault Management (CFM) CCM Alarms
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Connectivity Fault Management (CFM) Loopback Messages (LBM)
Loopback Messages (LBM) are unicast messages used for fault isolation (similar to ping)
LBMs are used to verify the connectivity between two maintenance points - i.e. between two MEPs or between a MEP and MIP
At the destination, a Loopback Reply (LBR) is sent back to the sender
MEP MIP LBM LBR
Provider Domain Provider Domain
Operator B Operator A
A
C
B
D
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Connectivity Fault Management (CFM) Link Trace Message (LTM)
Link Trace Messages (LTM) are used for path discovery
Sent from the source MEP to the target MEP (or MIP)
At each intermediate MIP to the target, a Link Trace Response (LTR) message is sent back to the originating MEP
The LTM is forwarded to the next MIP until the target MEP is reached
Based on the information in the LTRs received, the originating MEP can determine the path to the target MEP
Up to 10 link trace operations can be active at one time.
Provider Domain
MEP MIP LTM LTR
D
Operator B Operator A
A
C
B
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Connectivity Fault Management (CFM) Maintenance Domain (MD) Creation
Up to 32 MD’s are supported
Format Types:
String
MAC – Integer
DNS Name
No Name
MD Level: 0-7
MIP Creation Control*:
None
Default
Explicit
* Discussed later
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Connectivity Fault Management (CFM) Maintenance Association (MA) Creation - Network
Up to 32 MANET’s supported
Format Types:
Integer
Primary VID
String
VPN ID
ICC Format
CCM Interval:
3.3, 10, 100 msec; 1, 10 s; 1, 10 m
MEP List:
All MEPs that are part of this MA, one of which will be local
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Connectivity Fault Management (CFM) MA Creation – Component
Associates the MA to a port on the device
Associated Port
Primary VID
MIP Creation Control*:
None
Default
Explicit
Defer
* Discussed later
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Connectivity Fault Management (CFM) Maintenance End Point (MEP) Creation
Direction
State:
Expects to received CCMs
CCM Generation
Fault Alarm Priority:
Lowest priority fault that will result in an alarm
VLAN Priority:
P-bit value for this MEP
Primary VID:
VLAN ID for this MEP
At most 1 MEP per MA per device is supported
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Not intended to be used to measure performance (e.g. roundtrip delay)
Only 1 loopback operation can be initiated at a time per MEP
Invoked by choosing the “Loopback” option when right-clicking on the MEP Destination Type:
MAC Address – MAC address of the port supporting the remote MEP
Remote MEP Id – ID of the remote MEP
Destination ID based on the “Destination Type”
Number of LBMs to be transmitted: 1 – 50
Number of padding bytes in the Data TLV: 0 – 1473
Data Pattern: All Zeroes
All Ones
Alternate
VLAN Priority: 0 – 7
Transmit LBM Sequence number: automatically incremented by the system and is the value used in the first LBM sent in the group of LBMs.
VLAN Drop Enable: If an S-Tag is applied, “true” results in the DE-bit (Drop Eligible bit) being set.
Connectivity Fault Management (CFM) Loopback Initiation
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Only 1 link trace can be initiated at a time per MEP
A single multicast message is transmitted
Invoked by choosing the “Initiate LTM” option when right-clicking on the MEP
Destination Type:
MAC Address – MAC address of the port supporting the remote MEP
Remote MEP Id – MEP ID of the remote MEP
Destination ID
based on the “Destination Type”
TTL [1-255]
LTM Time To Live the max number of 802.1ag hops
Use FDB Only [Enabled/Disabled]
Next LTM Transaction ID (automatically incremented by the system)
Egress ID [8 octets]
Identifies the MEP Linktrace Initiator.
Connectivity Fault Management (CFM) Link Trace Initiation
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As a response to the LTM a device receives LTR
Based on the received LTRs there is a Database generated consisting of all MEPs and MIPs that have responded with their statuses, MAC addresses etc.
Connectivity Fault Management (CFM) Link Trace Response
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If a MIP is required, an MA or the default MD must exist.
MIPs are only created at the lowest MD level that is higher than the level where a MEP exists on that port.
MIP Creation Contol: None: MIPs are not created
Explicit: MIPs are created on the ports for the specified VIDs only if a MEP exists on that port at a lower MD level.
Default: MIPs are created when the MA is created.
Defer: Only applicable to the MA. The enclosing MD’s MIP Creation Control attribute is used to dictate MIP creation.
Two ways that a MIP can be created: As the result of the creation of an MA. If MA has MIP Creation Control:
Default: Created at same MD level as the MA and for all ports that do not support a MEP.
Explicit: Created at higher MD level as the MA if a MEP exists
As the result of creating an entry in the “CFM Vlan Table”
Connectivity Fault Management (CFM) MIPs
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Connectivity Fault Management (CFM) Ethernet AIS
AIS – Alarm Indication Signal
AIS frames can be generated by a MEP based on Error conditions on the underlying Ethernet port
link level
Error conditions reported by CCMs Mismerge/ Crossconnect CCM
Loss of connectivity
Unexpected or Error CCM
AIS defect
AIS frames are sent to higher level MEPs to report problems on the lower level MEPs
Higher Level MEPs can be configured to react in different ways to the reception of an AIS, e.g. Generate AIS frame for higher level MEPs
Activate Link Loss Forwarding
Do nothing (Suppress AIS)
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Connectivity Fault Management (CFM) Link Loss Forwarding
Link Loss Forwarding is an easy way to inform remote equipment about error conditions on the service.
If an error condition exists the Ethernet port is taken down causing the remote device to see a Link Loss
MEPs can be configured to switch off the underlying Ethernet port on reception of
AIS defect
CCM with Interface Status TLV “isDown”
RDI
Remote MEP CCM Failure
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Connectivity Fault Management (CFM) Y.1731 Performance Monitoring
On-demand layer 2 test frames between MEPs in the same MA. Less processing overhead and more accuracy than layer 3 test frames as used in ESA tests
until now.
Loss Measurement Single-ended LM fully supported
MEP sends LM messages, the other MEP responds with LMR
LM messages carry data frame counts
Delay Measurement MEP sends DMM, the other MEP responds with DMR
DM messages carry time stamps
Offered via ESA Probe Do not need to create a Reflector
Select protocol Y.1731, associate with LAN up MEPs,
Parameters are
Destination MEP
DMM and LMM interval
DMM size
ESA statistics are collected, e.g. packet count, loss, one-way and round-trip delay, jitter, … Times are in microseconds!
Binned and retrievable like regular ESA results
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End of CFM & Y.1731