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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.

Note:

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.

Table 1: 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:

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:

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:

Change History Table

Feature support is determined by the platform and release you are using. Use Feature Explorer to determine if a feature is supported on your platform.

Release
Description
15.1
Starting in Junos OS Release 15.1, configuring ISSU with CFM (802.1ag) is supported only on MX and PTX routers that support TLV.