# Improve network performance between EC2 instances with ENA Express
<a name="ena-express"></a>

ENA Express is powered by AWS Scalable Reliable Datagram (SRD) technology. SRD is a high performance network transport protocol that uses dynamic routing to increase throughput and minimize tail latency. With ENA Express, you can communicate between two EC2 instances in the same Availability Zone or across Availability Zones within the same Region.

**Benefits of ENA Express**
+ Increases the maximum bandwidth a single flow can use from 5 Gbps up to 25 Gbps within the same Region, up to the aggregate instance limit.
+ Reduces tail latency of network traffic between EC2 instances in the same Availability Zone, especially during periods of high network load.
+ Detects and avoids congested network paths.
+ Handles some tasks directly in the network layer, such as packet reordering on the receiving end, and most retransmits that are needed. This frees up the application layer for other work.

**Note**  
If your application has high packets-per-second requirements and needs to optimize for latency during uncongested periods, [Enhanced networking](enhanced-networking.md) might be a better fit.
ENA Express traffic can't be sent in a Local Zone.
ENA Express support for traffic between Availability Zones is not available in South America (São Paulo), Middle East (Bahrain), and Middle East (UAE).

After you've enabled ENA Express for the network interface attachment on an instance, the sending instance initiates communication with the receiving instance, and SRD detects if ENA Express is operating on both the sending instance and the receiving instance. If ENA Express is operating, the communication can use SRD transmission. If ENA Express is not operating, the communication falls back to standard ENA transmission.

During periods of time when network traffic is light, you might notice a slight increase in median packet latency (tens of microseconds) when the packet uses ENA Express. During those times, applications that prioritize specific network performance characteristics can benefit from ENA Express as follows:
+ Processes can benefit from increased maximum single flow bandwidth from 5 Gbps up to 25 Gbps within the same Region, up to the aggregate instance limit. For example, if a specific instance type supports up to 12.5 Gbps, the single flow bandwidth is also limited to 12.5 Gbps.
+ Longer running processes in the same Availability Zone will experience reduced tail latency during periods of network congestion.
+ Processes can benefit from a smoother and more standard distribution for network response times.

**Topics**
+ [How ENA Express works](#ena-express-how-it-works)
+ [Supported instance types for ENA Express](#ena-express-supported-instance-types)
+ [Tune performance for ENA Express settings on Linux instances](#ena-express-tune)
+ [Review ENA Express settings for your EC2 instance](ena-express-list-view.md)
+ [Configure ENA Express settings for your EC2 instance](ena-express-configure.md)

## How ENA Express works
<a name="ena-express-how-it-works"></a>

ENA Express is powered by AWS Scalable Reliable Datagram (SRD) technology. It distributes packets for each network flow across different AWS network paths, and dynamically adjusts distribution when it detects signs of congestion. It also manages packet reordering on the receiving end.

To ensure that ENA Express can manage network traffic as intended, sending and receiving instances and the communication between them must meet all of the following requirements:
+ Both sending and receiving instance types are supported. See the [Supported instance types for ENA Express](#ena-express-supported-instance-types) table for more information.
+ Both sending and receiving instances must have ENA Express configured. If there are differences in the configuration, you can run into situations where traffic defaults to standard ENA transmission. The following scenario shows what can happen.

  **Scenario: Differences in configuration**    
[See the AWS documentation website for more details](http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ena-express.html)

  In this case, TCP traffic between the two instances can use ENA Express, as both instances have enabled it. However, since one of the instances does not use ENA Express for UDP traffic, communication between these two instances over UDP uses standard ENA transmission.
+ The sending and receiving instances must run in the same Region.
+ The network path between the instances must not include middleware boxes. ENA Express doesn't currently support middleware boxes.
+ (Linux instances only) To utilize full bandwidth potential, use driver version 2.2.9 or higher.
+ (Linux instances only) To produce metrics, use driver version 2.8 or higher.

If any requirement is unmet, the instances use the standard TCP/UDP protocol but without SRD to communicate.

To ensure that your instance network driver is configured for optimum performance, review the recommended best practices for ENA drivers. These best practices apply to ENA Express, as well. For more information, see the [ENA Linux Driver Best Practices and Performance Optimization Guide](https://github.com/amzn/amzn-drivers/blob/master/kernel/linux/ena/ENA_Linux_Best_Practices.rst) on the GitHub website.

**Note**  
Amazon EC2 refers to the relationship between an instance and a network interface that's attached to it as an *attachment*. ENA Express settings apply to the attachment. If the network interface is detached from the instance, the attachment no longer exists, and the ENA Express settings that applied to it are no longer in force. The same is true when an instance is terminated, even if the network interface remains.

After you've enabled ENA Express for the network interface attachments on both the sending instance and the receiving instance, you can use ENA Express metrics to help ensure that your instances take full advantage of the performance improvements that SRD technology provides. For more information about ENA Express metrics, see [Metrics for ENA Express](monitoring-network-performance-ena.md#network-performance-metrics-ena-express).

## Supported instance types for ENA Express
<a name="ena-express-supported-instance-types"></a>

The following instance types support ENA Express.

------
#### [ General purpose ]


| Instance type | Architecture | 
| --- | --- | 
| m6a.12xlarge | x86\_64 | 
| m6a.16xlarge | x86\_64 | 
| m6a.24xlarge | x86\_64 | 
| m6a.32xlarge | x86\_64 | 
| m6a.48xlarge | x86\_64 | 
| m6a.metal | x86\_64 | 
| m6i.8xlarge | x86\_64 | 
| m6i.12xlarge | x86\_64 | 
| m6i.16xlarge | x86\_64 | 
| m6i.24xlarge | x86\_64 | 
| m6i.32xlarge | x86\_64 | 
| m6i.metal | x86\_64 | 
| m6id.8xlarge | x86\_64 | 
| m6id.12xlarge | x86\_64 | 
| m6id.16xlarge | x86\_64 | 
| m6id.24xlarge | x86\_64 | 
| m6id.32xlarge | x86\_64 | 
| m6id.metal | x86\_64 | 
| m6idn.8xlarge | x86\_64 | 
| m6idn.12xlarge | x86\_64 | 
| m6idn.16xlarge | x86\_64 | 
| m6idn.24xlarge | x86\_64 | 
| m6idn.32xlarge | x86\_64 | 
| m6idn.metal | x86\_64 | 
| m6in.8xlarge | x86\_64 | 
| m6in.12xlarge | x86\_64 | 
| m6in.16xlarge | x86\_64 | 
| m6in.24xlarge | x86\_64 | 
| m6in.32xlarge | x86\_64 | 
| m6in.metal | x86\_64 | 
| m7a.12xlarge | x86\_64 | 
| m7a.16xlarge | x86\_64 | 
| m7a.24xlarge | x86\_64 | 
| m7a.32xlarge | x86\_64 | 
| m7a.48xlarge | x86\_64 | 
| m7a.metal-48xl | x86\_64 | 
| m7g.12xlarge | arm64 | 
| m7g.16xlarge | arm64 | 
| m7g.metal | arm64 | 
| m7gd.12xlarge | arm64 | 
| m7gd.16xlarge | arm64 | 
| m7gd.metal | arm64 | 
| m7i.12xlarge | x86\_64 | 
| m7i.16xlarge | x86\_64 | 
| m7i.24xlarge | x86\_64 | 
| m7i.48xlarge | x86\_64 | 
| m7i.metal-24xl | x86\_64 | 
| m7i.metal-48xl | x86\_64 | 
| m8a.16xlarge | x86\_64 | 
| m8a.24xlarge | x86\_64 | 
| m8a.48xlarge | x86\_64 | 
| m8a.metal-24xl | x86\_64 | 
| m8a.metal-48xl | x86\_64 | 
| m8azn.12xlarge | x86\_64 | 
| m8azn.24xlarge | x86\_64 | 
| m8azn.metal-12xl | x86\_64 | 
| m8azn.metal-24xl | x86\_64 | 
| m8g.12xlarge | arm64 | 
| m8g.16xlarge | arm64 | 
| m8g.24xlarge | arm64 | 
| m8g.48xlarge | arm64 | 
| m8g.metal-24xl | arm64 | 
| m8g.metal-48xl | arm64 | 
| m8gb.8xlarge | arm64 | 
| m8gb.12xlarge | arm64 | 
| m8gb.16xlarge | arm64 | 
| m8gb.24xlarge | arm64 | 
| m8gb.48xlarge | arm64 | 
| m8gb.metal-24xl | arm64 | 
| m8gb.metal-48xl | arm64 | 
| m8gd.12xlarge | arm64 | 
| m8gd.16xlarge | arm64 | 
| m8gd.24xlarge | arm64 | 
| m8gd.48xlarge | arm64 | 
| m8gd.metal-24xl | arm64 | 
| m8gd.metal-48xl | arm64 | 
| m8gn.8xlarge | arm64 | 
| m8gn.12xlarge | arm64 | 
| m8gn.16xlarge | arm64 | 
| m8gn.24xlarge | arm64 | 
| m8gn.48xlarge | arm64 | 
| m8gn.metal-24xl | arm64 | 
| m8gn.metal-48xl | arm64 | 
| m8i.24xlarge | x86\_64 | 
| m8i.32xlarge | x86\_64 | 
| m8i.48xlarge | x86\_64 | 
| m8i.96xlarge | x86\_64 | 
| m8i.metal-48xl | x86\_64 | 
| m8i.metal-96xl | x86\_64 | 
| m8id.24xlarge | x86\_64 | 
| m8id.32xlarge | x86\_64 | 
| m8id.48xlarge | x86\_64 | 
| m8id.96xlarge | x86\_64 | 
| m8id.metal-48xl | x86\_64 | 
| m8id.metal-96xl | x86\_64 | 
| m8in.12xlarge | x86\_64 | 
| m8in.16xlarge | x86\_64 | 
| m8in.24xlarge | x86\_64 | 
| m8in.32xlarge | x86\_64 | 
| m8in.48xlarge | x86\_64 | 
| m8in.96xlarge | x86\_64 | 
| m8idn.12xlarge | x86\_64 | 
| m8idn.16xlarge | x86\_64 | 
| m8idn.24xlarge | x86\_64 | 
| m8idn.32xlarge | x86\_64 | 
| m8idn.48xlarge | x86\_64 | 
| m8idn.96xlarge | x86\_64 | 
| m8ib.12xlarge | x86\_64 | 
| m8ib.16xlarge | x86\_64 | 
| m8ib.24xlarge | x86\_64 | 
| m8ib.32xlarge | x86\_64 | 
| m8ib.48xlarge | x86\_64 | 
| m8ib.96xlarge | x86\_64 | 
| m8idb.12xlarge | x86\_64 | 
| m8idb.16xlarge | x86\_64 | 
| m8idb.24xlarge | x86\_64 | 
| m8idb.32xlarge | x86\_64 | 
| m8idb.48xlarge | x86\_64 | 
| m8idb.96xlarge | x86\_64 | 

------
#### [ Compute optimized ]


| Instance type | Architecture | 
| --- | --- | 
| c6a.12xlarge | x86\_64 | 
| c6a.16xlarge | x86\_64 | 
| c6a.24xlarge | x86\_64 | 
| c6a.32xlarge | x86\_64 | 
| c6a.48xlarge | x86\_64 | 
| c6a.metal | x86\_64 | 
| c6gn.4xlarge | arm64 | 
| c6gn.8xlarge | arm64 | 
| c6gn.12xlarge | arm64 | 
| c6gn.16xlarge | arm64 | 
| c6i.8xlarge | x86\_64 | 
| c6i.12xlarge | x86\_64 | 
| c6i.16xlarge | x86\_64 | 
| c6i.24xlarge | x86\_64 | 
| c6i.32xlarge | x86\_64 | 
| c6i.metal | x86\_64 | 
| c6id.8xlarge | x86\_64 | 
| c6id.12xlarge | x86\_64 | 
| c6id.16xlarge | x86\_64 | 
| c6id.24xlarge | x86\_64 | 
| c6id.32xlarge | x86\_64 | 
| c6id.metal | x86\_64 | 
| c6in.8xlarge | x86\_64 | 
| c6in.12xlarge | x86\_64 | 
| c6in.16xlarge | x86\_64 | 
| c6in.24xlarge | x86\_64 | 
| c6in.32xlarge | x86\_64 | 
| c6in.metal | x86\_64 | 
| c7a.12xlarge | x86\_64 | 
| c7a.16xlarge | x86\_64 | 
| c7a.24xlarge | x86\_64 | 
| c7a.32xlarge | x86\_64 | 
| c7a.48xlarge | x86\_64 | 
| c7a.metal-48xl | x86\_64 | 
| c7g.12xlarge | arm64 | 
| c7g.16xlarge | arm64 | 
| c7g.metal | arm64 | 
| c7gd.12xlarge | arm64 | 
| c7gd.16xlarge | arm64 | 
| c7gd.metal | arm64 | 
| c7gn.4xlarge | arm64 | 
| c7gn.8xlarge | arm64 | 
| c7gn.12xlarge | arm64 | 
| c7gn.16xlarge | arm64 | 
| c7gn.metal | arm64 | 
| c7i.12xlarge | x86\_64 | 
| c7i.16xlarge | x86\_64 | 
| c7i.24xlarge | x86\_64 | 
| c7i.48xlarge | x86\_64 | 
| c7i.metal-24xl | x86\_64 | 
| c7i.metal-48xl | x86\_64 | 
| c8a.16xlarge | x86\_64 | 
| c8a.24xlarge | x86\_64 | 
| c8a.48xlarge | x86\_64 | 
| c8a.metal-24xl | x86\_64 | 
| c8a.metal-48xl | x86\_64 | 
| c8g.12xlarge | arm64 | 
| c8g.16xlarge | arm64 | 
| c8g.24xlarge | arm64 | 
| c8g.48xlarge | arm64 | 
| c8g.metal-24xl | arm64 | 
| c8g.metal-48xl | arm64 | 
| c8gb.8xlarge | arm64 | 
| c8gb.12xlarge | arm64 | 
| c8gb.16xlarge | arm64 | 
| c8gb.24xlarge | arm64 | 
| c8gb.48xlarge | arm64 | 
| c8gb.metal-24xl | arm64 | 
| c8gb.metal-48xl | arm64 | 
| c8gd.12xlarge | arm64 | 
| c8gd.16xlarge | arm64 | 
| c8gd.24xlarge | arm64 | 
| c8gd.48xlarge | arm64 | 
| c8gd.metal-24xl | arm64 | 
| c8gd.metal-48xl | arm64 | 
| c8gn.8xlarge | arm64 | 
| c8gn.12xlarge | arm64 | 
| c8gn.16xlarge | arm64 | 
| c8gn.24xlarge | arm64 | 
| c8gn.48xlarge | arm64 | 
| c8gn.metal-24xl | arm64 | 
| c8gn.metal-48xl | arm64 | 
| c8i.24xlarge | x86\_64 | 
| c8i.32xlarge | x86\_64 | 
| c8i.48xlarge | x86\_64 | 
| c8i.96xlarge | x86\_64 | 
| c8i.metal-48xl | x86\_64 | 
| c8i.metal-96xl | x86\_64 | 
| c8id.24xlarge | x86\_64 | 
| c8id.32xlarge | x86\_64 | 
| c8id.48xlarge | x86\_64 | 
| c8id.96xlarge | x86\_64 | 
| c8id.metal-48xl | x86\_64 | 
| c8id.metal-96xl | x86\_64 | 
| c8in.12xlarge | x86\_64 | 
| c8in.16xlarge | x86\_64 | 
| c8in.24xlarge | x86\_64 | 
| c8in.32xlarge | x86\_64 | 
| c8in.48xlarge | x86\_64 | 
| c8in.96xlarge | x86\_64 | 
| c8in.metal-48xl | x86\_64 | 
| c8in.metal-96xl | x86\_64 | 
| c8ib.12xlarge | x86\_64 | 
| c8ib.16xlarge | x86\_64 | 
| c8ib.24xlarge | x86\_64 | 
| c8ib.32xlarge | x86\_64 | 
| c8ib.48xlarge | x86\_64 | 
| c8ib.96xlarge | x86\_64 | 
| c8ib.metal-48xl | x86\_64 | 
| c8ib.metal-96xl | x86\_64 | 

------
#### [ Memory optimized ]


| Instance type | Architecture | 
| --- | --- | 
| r6a.12xlarge | x86\_64 | 
| r6a.16xlarge | x86\_64 | 
| r6a.24xlarge | x86\_64 | 
| r6a.32xlarge | x86\_64 | 
| r6a.48xlarge | x86\_64 | 
| r6a.metal | x86\_64 | 
| r6i.8xlarge | x86\_64 | 
| r6i.12xlarge | x86\_64 | 
| r6i.16xlarge | x86\_64 | 
| r6i.24xlarge | x86\_64 | 
| r6i.32xlarge | x86\_64 | 
| r6i.metal | x86\_64 | 
| r6id.8xlarge | x86\_64 | 
| r6id.12xlarge | x86\_64 | 
| r6id.16xlarge | x86\_64 | 
| r6id.24xlarge | x86\_64 | 
| r6id.32xlarge | x86\_64 | 
| r6id.metal | x86\_64 | 
| r6idn.8xlarge | x86\_64 | 
| r6idn.12xlarge | x86\_64 | 
| r6idn.16xlarge | x86\_64 | 
| r6idn.24xlarge | x86\_64 | 
| r6idn.32xlarge | x86\_64 | 
| r6idn.metal | x86\_64 | 
| r6in.8xlarge | x86\_64 | 
| r6in.12xlarge | x86\_64 | 
| r6in.16xlarge | x86\_64 | 
| r6in.24xlarge | x86\_64 | 
| r6in.32xlarge | x86\_64 | 
| r6in.metal | x86\_64 | 
| r7a.12xlarge | x86\_64 | 
| r7a.16xlarge | x86\_64 | 
| r7a.24xlarge | x86\_64 | 
| r7a.32xlarge | x86\_64 | 
| r7a.48xlarge | x86\_64 | 
| r7a.metal-48xl | x86\_64 | 
| r7g.12xlarge | arm64 | 
| r7g.16xlarge | arm64 | 
| r7g.metal | arm64 | 
| r7gd.12xlarge | arm64 | 
| r7gd.16xlarge | arm64 | 
| r7gd.metal | arm64 | 
| r7i.12xlarge | x86\_64 | 
| r7i.16xlarge | x86\_64 | 
| r7i.24xlarge | x86\_64 | 
| r7i.48xlarge | x86\_64 | 
| r7i.metal-24xl | x86\_64 | 
| r7i.metal-48xl | x86\_64 | 
| r7iz.8xlarge | x86\_64 | 
| r7iz.12xlarge | x86\_64 | 
| r7iz.16xlarge | x86\_64 | 
| r7iz.32xlarge | x86\_64 | 
| r7iz.metal-16xl | x86\_64 | 
| r7iz.metal-32xl | x86\_64 | 
| r8a.16xlarge | x86\_64 | 
| r8a.24xlarge | x86\_64 | 
| r8a.48xlarge | x86\_64 | 
| r8a.metal-24xl | x86\_64 | 
| r8a.metal-48xl | x86\_64 | 
| r8g.12xlarge | arm64 | 
| r8g.16xlarge | arm64 | 
| r8g.24xlarge | arm64 | 
| r8g.48xlarge | arm64 | 
| r8g.metal-24xl | arm64 | 
| r8g.metal-48xl | arm64 | 
| r8gb.8xlarge | arm64 | 
| r8gb.12xlarge | arm64 | 
| r8gb.16xlarge | arm64 | 
| r8gb.24xlarge | arm64 | 
| r8gb.48xlarge | arm64 | 
| r8gb.metal-24xl | arm64 | 
| r8gb.metal-48xl | arm64 | 
| r8gd.12xlarge | arm64 | 
| r8gd.16xlarge | arm64 | 
| r8gd.24xlarge | arm64 | 
| r8gd.48xlarge | arm64 | 
| r8gd.metal-24xl | arm64 | 
| r8gd.metal-48xl | arm64 | 
| r8gn.8xlarge | arm64 | 
| r8gn.12xlarge | arm64 | 
| r8gn.16xlarge | arm64 | 
| r8gn.24xlarge | arm64 | 
| r8gn.48xlarge | arm64 | 
| r8gn.metal-24xl | arm64 | 
| r8gn.metal-48xl | arm64 | 
| r8i.24xlarge | x86\_64 | 
| r8i.32xlarge | x86\_64 | 
| r8i.48xlarge | x86\_64 | 
| r8i.96xlarge | x86\_64 | 
| r8i.metal-48xl | x86\_64 | 
| r8i.metal-96xl | x86\_64 | 
| r8id.24xlarge | x86\_64 | 
| r8id.32xlarge | x86\_64 | 
| r8id.48xlarge | x86\_64 | 
| r8id.96xlarge | x86\_64 | 
| r8id.metal-48xl | x86\_64 | 
| r8id.metal-96xl | x86\_64 | 
| r8in.12xlarge | x86\_64 | 
| r8in.16xlarge | x86\_64 | 
| r8in.24xlarge | x86\_64 | 
| r8in.32xlarge | x86\_64 | 
| r8in.48xlarge | x86\_64 | 
| r8in.96xlarge | x86\_64 | 
| r8idn.12xlarge | x86\_64 | 
| r8idn.16xlarge | x86\_64 | 
| r8idn.24xlarge | x86\_64 | 
| r8idn.32xlarge | x86\_64 | 
| r8idn.48xlarge | x86\_64 | 
| r8idn.96xlarge | x86\_64 | 
| r8ib.12xlarge | x86\_64 | 
| r8ib.16xlarge | x86\_64 | 
| r8ib.24xlarge | x86\_64 | 
| r8ib.32xlarge | x86\_64 | 
| r8ib.48xlarge | x86\_64 | 
| r8ib.96xlarge | x86\_64 | 
| r8idb.12xlarge | x86\_64 | 
| r8idb.16xlarge | x86\_64 | 
| r8idb.24xlarge | x86\_64 | 
| r8idb.32xlarge | x86\_64 | 
| r8idb.48xlarge | x86\_64 | 
| r8idb.96xlarge | x86\_64 | 
| u7i-6tb.112xlarge | x86\_64 | 
| u7i-8tb.112xlarge | x86\_64 | 
| u7i-12tb.224xlarge | x86\_64 | 
| u7in-16tb.224xlarge | x86\_64 | 
| u7in-24tb.224xlarge | x86\_64 | 
| u7in-32tb.224xlarge | x86\_64 | 
| u7inh-32tb.480xlarge | x86\_64 | 
| x2idn.16xlarge | x86\_64 | 
| x2idn.24xlarge | x86\_64 | 
| x2idn.32xlarge | x86\_64 | 
| x2idn.metal | x86\_64 | 
| x2iedn.8xlarge | x86\_64 | 
| x2iedn.16xlarge | x86\_64 | 
| x2iedn.24xlarge | x86\_64 | 
| x2iedn.32xlarge | x86\_64 | 
| x2iedn.metal | x86\_64 | 
| x8g.12xlarge | arm64 | 
| x8g.16xlarge | arm64 | 
| x8g.24xlarge | arm64 | 
| x8g.48xlarge | arm64 | 
| x8g.metal-24xl | arm64 | 
| x8g.metal-48xl | arm64 | 
| x8aedz.24xlarge | x86\_64 | 
| x8aedz.metal-24xl | x86\_64 | 
| x8i.24xlarge | x86\_64 | 
| x8i.32xlarge | x86\_64 | 
| x8i.48xlarge | x86\_64 | 
| x8i.64xlarge | x86\_64 | 
| x8i.96xlarge | x86\_64 | 
| x8i.metal-48xl | x86\_64 | 
| x8i.metal-96xl | x86\_64 | 

------
#### [ Accelerated computing ]


| Instance type | Architecture | 
| --- | --- | 
| g6.48xlarge | x86\_64 | 
| g6e.12xlarge | x86\_64 | 
| g6e.24xlarge | x86\_64 | 
| g6e.48xlarge | x86\_64 | 
| g7e.12xlarge | x86\_64 | 
| g7e.24xlarge | x86\_64 | 
| g7e.48xlarge | x86\_64 | 
| p5.4xlarge | x86\_64 | 
| p5.48xlarge | x86\_64 | 
| p5e.48xlarge | x86\_64 | 
| p5en.48xlarge | x86\_64 | 
| p6-b200.48xlarge | x86\_64 | 
| p6-b300.48xlarge | x86\_64 | 

------
#### [ Storage optimized ]


| Instance type | Architecture | 
| --- | --- | 
| i4g.4xlarge | arm64 | 
| i4g.8xlarge | arm64 | 
| i4g.16xlarge | arm64 | 
| i4i.8xlarge | x86\_64 | 
| i4i.12xlarge | x86\_64 | 
| i4i.16xlarge | x86\_64 | 
| i4i.24xlarge | x86\_64 | 
| i4i.32xlarge | x86\_64 | 
| i4i.metal | x86\_64 | 
| i7i.12xlarge | x86\_64 | 
| i7i.16xlarge | x86\_64 | 
| i7i.24xlarge | x86\_64 | 
| i7i.48xlarge | x86\_64 | 
| i7i.metal-24xl | x86\_64 | 
| i7i.metal-48xl | x86\_64 | 
| i7ie.12xlarge | x86\_64 | 
| i7ie.18xlarge | x86\_64 | 
| i7ie.24xlarge | x86\_64 | 
| i7ie.48xlarge | x86\_64 | 
| i7ie.metal-24xl | x86\_64 | 
| i7ie.metal-48xl | x86\_64 | 
| i8g.12xlarge | arm64 | 
| i8g.16xlarge | arm64 | 
| i8g.24xlarge | arm64 | 
| i8g.48xlarge | arm64 | 
| i8g.metal-24xl | arm64 | 
| i8g.metal-48xl | arm64 | 
| i8ge.12xlarge | arm64 | 
| i8ge.18xlarge | arm64 | 
| i8ge.24xlarge | arm64 | 
| i8ge.48xlarge | arm64 | 
| i8ge.metal-24xl | arm64 | 
| i8ge.metal-48xl | arm64 | 
| im4gn.4xlarge | arm64 | 
| im4gn.8xlarge | arm64 | 
| im4gn.16xlarge | arm64 | 

------

## Tune performance for ENA Express settings on Linux instances
<a name="ena-express-tune"></a>

To ensure that ENA Express can operate effectively, your Linux instance must meet several network configuration requirements.

Rather than configuring each setting manually, you can download and run the ENA Express settings check script from the Amazon GitHub repository. The script validates your instance against the required and recommended settings for ENA Express, and outputs the exact commands to fix any issues it finds.

[https://github.com/amzn/amzn-ec2-ena-utilities/blob/main/ena-express/check-ena-express-settings.sh](https://github.com/amzn/amzn-ec2-ena-utilities/blob/main/ena-express/check-ena-express-settings.sh)

The script checks the following settings and configurations:
+ **MTU size** – ENA Express requires a lower MTU than the default to accommodate additional AWS SRD headers. Newly established TCP connections automatically clamp the MSS to mitigate this, but UDP traffic still requires a lower MTU.
+ **TCP output queue size limit** – Checks that the per-socket in-flight byte limit is sufficient to sustain high throughput. Environments with increased network latency require a higher limit.
+ **Byte queue limit** – Confirms that the byte queue limit (BQL) is disabled on the network interface. BQL can restrict the amount of data queued for device-level transmission, which limits ENA Express performance.
**Note**  
The ENA driver for the Amazon Linux distribution disables byte queue limits by default.
+ **TCP autocorking** – Checks whether TCP autocorking is disabled. Disabling autocorking can reduce latency for certain ENA Express TCP traffic patterns, such as request-response workloads. This might result in a minimal increase in packet processing overhead.
+ **TX queue size and Large LLQ** – Verifies that the transmit queue size for the network interface is large enough for optimal performance. The script also checks whether the ENA module parameter explicitly disables the Large Low Latency Queue (Large LLQ) feature, as it can reduce the available TX queue depth. For more information about Large LLQ and its impact on TX queue size, see [Large Low Latency Queue (Large LLQ)](https://github.com/amzn/amzn-drivers/tree/master/kernel/linux/ena#large-low-latency-queue-large-llq) on GitHub.
+ **RX queue size** – Checks that the receive ring buffer for the network interface is large enough to handle incoming traffic efficiently and avoid packet drops under load.
+ **TCP and network socket buffer sizes** – Validates that the TCP receive and send buffer maximum sizes, as well as the core network socket buffer defaults and maximums, are large enough to sustain high throughput. These settings are important in environments with increased network latency, where you need larger buffers to utilize the connection.
+ **TCP congestion control** – Verifies that the TCP congestion control configuration is optimized for use with ENA Express in environments with increased network latency.

The script also reports additional diagnostic information, including the ENA driver version, ENA SRD statistics, interrupt moderation settings, queue configuration, and socket buffer sizes. This information can be useful for troubleshooting ENA Express performance issues.

To ensure that your instance network driver is configured for optimum performance, also review the [ENA Linux Driver Best Practices and Performance Optimization Guide](https://github.com/amzn/amzn-drivers/blob/master/kernel/linux/ena/ENA_Linux_Best_Practices.rst) on GitHub.