close

keyboard_arrow_left

Table of Contents Expand all

play_arrow Basic CoS Configuration
play_arrow Weighted Random Early Detection (WRED) and Explicit Congestion Notification (ECN)
- play_arrow WRED and Drop Profiles
- play_arrow Explicit Congestion Notification (ECN)
play_arrow CoS Queue Schedulers, Traffic Control Profiles, and Hierarchical Port Scheduling (ETS)
- play_arrow Queue Schedulers and Scheduling Priority
- play_arrow Port Scheduling and Shaping
- play_arrow Troubleshooting Egress Bandwidth Issues
- play_arrow Traffic Control Profiles and Priority Group Scheduling
- play_arrow Hierarchical Port Scheduling (ETS)
play_arrow Data Center Bridging and Lossless FCoE
- play_arrow Data Center Bridging
- play_arrow Lossless FCoE
play_arrow CoS Buffers and the Shared Buffer Pool
- play_arrow CoS Buffers Overview
- play_arrow Shared Buffer Pool Examples
play_arrow CoS on EVPN VXLANs
- CoS Support on EVPN VXLANs
play_arrow Configuration Statements and Operational Commands
- Junos CLI Reference Overview

list Table of Contents

English

keyboard_arrow_right

Configuring Global Ingress and Egress Shared Buffers

date_range 29-Nov-23

arrow_backward

arrow_forward

Although the switch reserves some buffer space to ensure a minimum memory allocation for ports and queues, you can configure how the system uses the rest of the buffer space to optimize the buffer allocation for your particular mix of network traffic. The global shared buffer pool is memory space that all of the ports on the switch share dynamically as they need buffers. You can allocate global shared memory space to different types of ingress and egress buffers to better support different mixes of network traffic.

CAUTION:

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

Use the default shared buffer settings (for a network with a balanced mix of lossless, best-effort, and multicast traffic) or one of the recommended shared buffer configurations for your mix of network traffic (mostly best-effort unicast traffic, mostly best-effort traffic on links enabled for Ethernet PAUSE, mostly multicast traffic, or mostly lossless traffic). Either the default configuration or one of the recommended configurations provides a buffer allocation that satisfies the needs of most networks.

After starting from one of the recommended configurations, you can fine-tune the shared buffer settings, but do so with caution to prevent traffic loss due to buffer misconfiguration.

You can configure the percentage of available (user-configurable) buffer space allocated to the global shared buffers. Any space that you do not allocate to the global shared buffer pool is added to the dedicated buffer pool. The default configuration allocates 100 percent of the available buffer space to the global shared buffers.

You can partition the ingress and egress shared buffer pools to allocate more buffers to the types of traffic your network predominantly carries, and fewer buffers to other traffic. From the buffer space allocated to the ingress shared buffer pool, you can allocate space to:

Lossless buffers—Percentage of shared buffer pool for all lossless ingress traffic. The minimum value for the lossless buffers is 5 percent.
Lossless headroom buffers—Percentage of shared buffer pool for packets received while a pause is asserted. If Ethernet PAUSE is configured on a port or if priority-based flow control (PFC) is configured on priorities on a port, when the port sends a pause message to the connected peer, the port uses the headroom buffers to store the packets that arrive between the time the port sends the pause message and the time the last packet arrives after the peer pauses traffic. The minimum value for the lossless headroom buffers is 0 (zero) percent. (Lossless headroom buffers are the only buffers that can have a minimum value of less than 5 percent.)

Note:
On a QFX Virtual Chassis and an EX4600/EX4650 Virtual Chassis, the minimum value for the lossless headroom buffer is 3 percent.
Lossy buffers—Percentage of shared buffer pool for all best-effort ingress traffic (best-effort unicast, multidestination, and strict-high priority traffic). The minimum value for the lossy buffers is 5 percent.

The combined percentage values of the ingress lossless, lossless headroom, and lossy buffer partitions must total exactly 100 percent. If the buffer percentages total more than 100 percent or less than 100 percent, the switch returns a commit error. All ingress buffer partitions must be explicitly configured, even when the lossless headroom buffer partition has a value of 0 (zero) percent.

From the buffer space allocated to the egress shared buffer pool, you can allocate space to:

Lossless buffers—Percentage of shared buffer pool for all lossless egress queues. The minimum value for the lossless buffers is 5 percent.
Lossy buffers—Percentage of shared buffer pool for all best-effort egress queues (best-effort unicast and strict-high priority queues). The minimum value for the lossy buffers is 5 percent.
Multicast buffers—Percentage of shared buffer pool for all multidestination (multicast, broadcast, and destination lookup fail) egress queues. The minimum value for the multicast buffers is 5 percent.

The combined percentage values of the egress lossless, lossy, and multicast buffer partitions must total exactly 100 percent. If the buffer percentages total more than 100 percent or less than 100 percent, the switch returns a commit error. All egress buffer partitions must be explicitly configured and must have a value of at least 5 percent.

To configure the shared buffer allocation and partitioning using the CLI:

Configure the percentage of available (nonreserved) buffers used for the ingress global shared buffer pool:
```
[edit class-of-service shared-buffer]
user@switch# set ingress percent percent
```

Configure the global ingress buffer partitions for lossless, lossless-headroom, and lossy traffic:

content_copy zoom_out_map
[edit class-of-service shared-buffer]
user@switch# set ingress buffer-partition lossless percent percent
user@switch# set ingress buffer-partition lossless-headroom percent percent
user@switch# set ingress buffer-partition lossy percent percent

Configure the percentage of available (nonreserved) buffers used for the egress global shared buffer pool:
```
[edit class-of-service shared-buffer]
user@switch# set egress percent percent
```

Configure the global egress buffer partitions for lossless, lossy, and multicast queues:

content_copy zoom_out_map
[edit class-of-service shared-buffer]
user@switch# set egress buffer-partition lossless percent percent
user@switch# set egress buffer-partition lossy percent percent
user@switch# set egress buffer-partition multicast percent percent

arrow_backward PREVIOUS Understanding CoS Buffer Configuration

NEXT arrow_forward Configuring Ingress and Egress Dedicated Buffers

Traffic Management User Guide (QFX Series Switches and EX4600 Switches)

Configuring Global Ingress and Egress Shared Buffers

Stay in touch

Helped me install or use the product
Accelerated my deployment

Discuss the product with a co-worker
Make a purchase inquiry

Traffic Management User Guide (QFX Series Switches and EX4600 Switches)

Configuring Global Ingress and Egress Shared Buffers

Related Documentation

Stay in touch