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buffer-partition (Ingress)


Hierarchy Level


The ingress shared buffer pool is divided into three partitions. Each partition reserves a percentage of the available shared buffer pool for a type of traffic, so that the switch provides enough resources to support a mix of best effort (best-effort unicast and multicast) and lossless traffic. To better support the mix of traffic on your network, you can optimize the allocation of ingress shared buffers to different types of traffic by fine-tuning the shared buffer partitions.

The percentages you configure for the three ingress shared buffer partitions must total exactly 100 percent. If the total of the three shared buffer percentages is not 100 percent, the system returns a commit error and does not commit the configuration. You can configure any partition to 0 (zero) percent as long as the allocation to other partitions totals 100 percent.

This is a global allocation that applies to all ingress traffic. All ports on the switch receive the same allocation of ingress shared buffers.

If you do not configure buffer partitions, the switch uses the default partitioning.


Changing the buffer configuration is a disruptive event. Traffic stops on all ports until buffer reprogramming is complete.


The default ingress buffer partition shown in Table 1 supports networks with a balanced mix of best-effort, multicast, and lossless traffic. It is the recommended configuration if you are using the default configuration with two lossless forwarding classes.

Table 1: Default Ingress Shared Buffer Partitioning

Lossless Partition

Lossless-Headroom Partition

Lossy Partition




The sum of the default percentages configured for each partition is 100 percent. The sum of the partition percentages always must total 100 percent.


dynamic-threshold value

Threshold for maximum buffer share for a queue at the ingress buffer partition.


Shared buffer space reserved for all lossless ingress traffic.


Shared buffer space reserved to store packets received while either an 802.3x Ethernet PAUSE or a priority-based flow control (PFC) pause is asserted. (When an ingress interface pauses traffic, it must have the buffer space to store all of the packets currently in the buffer, and also all of the packets received before the connected peer stops sending traffic and the wire is cleared of packets.)


Shared buffer space for best-effort ingress traffic.

percent percent

The percentage of buffer space to allocate to the specified buffer partition (lossless, lossless-headroom, or lossy buffers). The sum of the percentages for the three buffer partitions must total 100 percent.

Required Privilege Level

interfaces—To view this statement in the configuration.

interface-control—To add this statement to the configuration.

Release Information

Statement introduced in Junos OS Release 12.3.

dynamic-threshold option introduced in Junos OS Release 19.1R1 for the QFX Series.