Configure Unified ISSU for 802.1ag CFM
A unified in-service software upgrade (ISSU) enables you to upgrade between two different Junos OS releases with no disruption on the control plane and with minimal disruption of traffic. Unified ISSU is automatically enabled for the Connectivity Fault Management (CFM) protocols and interoperates between local and remote maintenance endpoints (MEPs).
The Junos OS provides support for unified ISSU using the loss threshold type length value (TLV), which is automatically enabled for CFM. TLVs are described in the IEEE 802.1ag standard for CFM as a method of encoding variable-length and optional information in a protocol data unit (PDU). The loss threshold TLV indicates the loss threshold value of a remote MEP. The loss threshold TLV is transmitted as part of the CFM continuity check messages.
Starting in Junos OS Release 15.1, configuring ISSU with CFM (802.1ag) is supported only on MX and PTX routers that support TLV. Interoperation with other vendors is not supported.
During a unified ISSU, the control plane may go down for several seconds and cause CFM continuity check packets to get dropped. This may cause the remote MEP to detect a connectivity loss and mark the MEP as down. To keep the MEP active during a unified ISSU, the loss threshold TLV communicates the minimum threshold value the receiving MEP requires to keep the MEP active. The receiving MEP parses the TLV and updates the loss threshold value, but only if the new threshold value is greater than the locally configured threshold value.
An overview of CFM is described starting in IEEE 802.1ag OAM Connectivity Fault Management Overview, and you should further observe the additional requirements described in this topic.
Table 1 shows the Loss Threshold TLV format.
Parameter |
Octet (sequence) |
Description |
---|---|---|
Type=31 |
1 |
Required. Required. If 0, no Length or Value fields follow. If not 0, at least the Length field follows the Type field. |
Length=12 |
2 |
Required if the Type field is not 0. Not present if the Type field is 0. The 16 bits of the Length field indicate the size, in octets, of the Value field. 0 in the Length field indicates that there is no Value field. |
OUI |
3 |
Optional. Organization unique identifier (OUI), which is controlled by the IEEE and is typically the first three bytes of a MAC address (Juniper OUI 0x009069). |
Subtype |
1 |
Optional. Organizationally defined subtype. |
Value |
4 |
Optional. Loss threshold value. |
Flag |
4 |
Optional. Bit0 (identifies an ISSU is in progress) Bit1-31 (reserved) |
Junos OS provides configuration support for the convey-loss-threshold
statement, allowing you to control the transmission of the loss
threshold TLV in continuity check messages PDUs. The convey-loss-threshold
statement specifies that the loss threshold TLV must be transmitted
as part of the continuity check messages. If the convey-loss-threshold
statement is not specified, continuity check messages transmit this
TLV only when a unified ISSU is in progress. The Junos OS provides
this configuration at the continuity-check level. By default, continuity
check messages do not include the loss threshold TLV.
To configure the convey loss threshold, use the convey-loss-threshold
statement at the [edit protocols oam ethernet connectivity-fault-management
maintenance-domain identifier maintenance-association identifier continuity-check]
hierarchy level.
For the remote MEP, the loss threshold TLV is transmitted only
during the unified ISSU if the convey-loss-threshold
statement
is not configured. The remote MEP switches back to the default loss
threshold if no loss threshold TLV is received or the TLV has a default
threshold value of 3.
An example of the ISSU configuration statements follows:
protocols { oam { ethernet { connectivity-fault-management { maintenance-domain identifier { level number; maintenance-association identifier { continuity-check { convey-loss-threshold; interval number; loss-threshold number; hold-interval number; } } } } } } }
The Junos OS saves the last received loss threshold TLV from
the remote MEP. You can display the last saved loss threshold TLV
that is received by the remote MEP, using the show oam ethernet
connectivity-fault-management mep-database maintenance-domain identifier maintenance-association identifier local-mep identifier remote-mep identifier
command, as in the following example:
user@host> show oam ethernet connectivity-fault-management mep-database maintenance-domain md3 maintenance-association ma5 local-mep 2 remote-mep 1 Maintenance domain name: md3, Format: string, Level: 3 Maintenance association name: ma3, Format: string Continuity-check status: enabled, Interval: 1s, Loss-threshold: 3 frames MEP identifier: 2, Direction: up, MAC address: 00:19:e2:b0:76:be Auto-discovery: enabled, Priority: 0 Interface status TLV: none, Port status TLV: none Connection Protection TLV: yes Prefer me: no, Protection in use: no, FRR Flag: no Interface name: xe-4/1/1.0, Interface status: Active, Link status: Up Loss Threshold TLV: Loss Threshold: 3 , Flag: 0x0 Remote MEP identifier: 1, State: ok MAC address: 00:1f:12:b7:ce:79, Type: Learned Interface: xe-4/1/1.0 Last flapped: Never Continuity: 100%, Admin-enable duration: 45sec, Oper-down duration: 0sec Effective loss threshold: 3 frames Remote defect indication: false Port status TLV: none Interface status TLV: none Connection Protection TLV: Prefer me: no, Protection in use: no, FRR Flag: no Loss Threshold TLV: #Displays last received value Loss Threshold: 3 , Flag: 0x0
The Junos OS saves the last transmitted loss threshold TLV from
a local MEP. You can display the last transmitted loss threshold TLV
and the effective loss (operational) threshold for the remote MEP,
using the show oam ethernet connectivity-fault-management mep-database
maintenance-domain identifier maintenance-association identifier local-mep identifier remote-mep identifier
command, as in the following example:
user@host> show oam ethernet connectivity-fault-management mep-database maintenance-domain md3 maintenance-association ma5 local-mep 2 remote-mep 1 Maintenance domain name: md3, Format: string, Level: 3 Maintenance association name: ma3, Format: string Continuity-check status: enabled, Interval: 1s, Loss-threshold: 3 frames MEP identifier: 2, Direction: up, MAC address: 00:19:e2:b0:76:be Auto-discovery: enabled, Priority: 0 Interface status TLV: none, Port status TLV: none Connection Protection TLV: yes Prefer me: no, Protection in use: no, FRR Flag: no Interface name: xe-4/1/1.0, Interface status: Active, Link status: Up Loss Threshold TLV: #Displays last transmitted value Loss Threshold: 3 , Flag: 0x0 Remote MEP identifier: 1, State: ok MAC address: 00:1f:12:b7:ce:79, Type: Learned Interface: xe-4/1/1.0 Last flapped: Never Continuity: 100%, Admin-enable duration: 45sec, Oper-down duration: 0sec Effective loss threshold: 3 frames #Displays operational threshold Remote defect indication: falsePort status TLV: none Interface status TLV: none Connection Protection TLV: Prefer me: no, Protection in use: no, FRR Flag: no Loss Threshold TLV: Loss Threshold: 3 , Flag: 0x0
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