mtu-signalling

Function

The mtu-signalling command enables the router to send Label Mapping messages carrying the maximum transmission unit (MTU) TLV.

The undo mtu-signalling command disables the router to send Label Mapping messages carrying the MTU TLV.

By default, the router sends Label Mapping messages carrying the private MTU TLV.

Format

mtu-signalling [ apply-tlv ]

undo mtu-signalling [ apply-tlv ]

Parameters

Parameter	Description	Value
apply-tlv	Sends Label Mapping messages carrying the MTU TLV, as defined in RFC 3988. If this parameter is not configured, Label Mapping messages carry a Huawei proprietary MTU TLV.	-

Views

MPLS-LDP view

Default Level

2: Configuration level

Usage Guidelines

Usage Scenario

An MPLS MTU value determines the maximum size of a Label Mapping message exchange between two devices on the same network. Before packet transmission, devices calculate the MPLS MTU value to avoid packet fragmentation during the transmission, relieving the load on the network. The MPLS MTU value advertised between devices is carried in the MTU TLV field of the Label Mapping message.

After the mpls ldp command is run, an MPLS LDP-enabled label switching router (LSR) by default sends a Huawei proprietary MTU TLV different from the MTU TLV defined in RFC 3988.

Using the default MTU setting is recommended.
To ensure the communication with non-Huawei devices, run the mtu-signalling apply-tlv command to enable LSRs to send Label Mapping messages carrying the MTU TLV defined in RFC 3988.

Prerequisites

MPLS LDP has been enabled globally using the mpls ldp command in the system view.

Implementation Procedure

When the mtu-signalling command is run, the system displays the following prompt:

  Warning: All the related sessions will be deleted if the operation is performed! Continue? (y/n)

To continue the operation, enter y.

Precautions

The MPLS MTU is a parameter to be negotiated during the LDP label switched path (LSP) establishment. If a Huawei device is connected to a non-Huawei device, run the mtu-signalling apply-tlv command. Otherwise, the user-defined MPLS MTU does not take effect.

The mtu-signalling command must be run before the mpls ldp command is run. Otherwise, the number of network packets increases abruptly.

Example

# Enable LDP to send Label Mapping messages carrying the MTU TLV, as defined in RFC 3988.

<sysname> system-view

[sysname] mpls ldp

[sysname-mpls-ldp] mtu-signalling apply-tlv

Warning: All the related sessions will be deleted if the operation is performed!

Continue? (y/n)y

[sysname-mpls-ldp] quit