# 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.

**Benefits of ENA Express**
+ Increases the maximum bandwidth a single flow can use from 5 Gbps up to 25 Gbps within the Availability Zone, up to the aggregate instance limit.
+ Reduces tail latency of network traffic between EC2 instances, 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 sends or receives a high volume of packets per second, and needs to optimize for latency most of the time, especially during periods when there is no congestion on the network, [Enhanced networking](enhanced-networking.md) might be a better fit for your network.
ENA Express traffic can't be sent in a Local Zone.

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 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 Availability Zone, 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 should 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)
+ [Prerequisites for Linux instances](#ena-express-prereq-linux)
+ [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 Availability Zone.
+ 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\$164 | 
| m6a.16xlarge | x86\$164 | 
| m6a.24xlarge | x86\$164 | 
| m6a.32xlarge | x86\$164 | 
| m6a.48xlarge | x86\$164 | 
| m6a.metal | x86\$164 | 
| m6i.8xlarge | x86\$164 | 
| m6i.12xlarge | x86\$164 | 
| m6i.16xlarge | x86\$164 | 
| m6i.24xlarge | x86\$164 | 
| m6i.32xlarge | x86\$164 | 
| m6i.metal | x86\$164 | 
| m6id.8xlarge | x86\$164 | 
| m6id.12xlarge | x86\$164 | 
| m6id.16xlarge | x86\$164 | 
| m6id.24xlarge | x86\$164 | 
| m6id.32xlarge | x86\$164 | 
| m6id.metal | x86\$164 | 
| m6idn.8xlarge | x86\$164 | 
| m6idn.12xlarge | x86\$164 | 
| m6idn.16xlarge | x86\$164 | 
| m6idn.24xlarge | x86\$164 | 
| m6idn.32xlarge | x86\$164 | 
| m6idn.metal | x86\$164 | 
| m6in.8xlarge | x86\$164 | 
| m6in.12xlarge | x86\$164 | 
| m6in.16xlarge | x86\$164 | 
| m6in.24xlarge | x86\$164 | 
| m6in.32xlarge | x86\$164 | 
| m6in.metal | x86\$164 | 
| m7a.12xlarge | x86\$164 | 
| m7a.16xlarge | x86\$164 | 
| m7a.24xlarge | x86\$164 | 
| m7a.32xlarge | x86\$164 | 
| m7a.48xlarge | x86\$164 | 
| m7a.metal-48xl | x86\$164 | 
| m7g.12xlarge | arm64 | 
| m7g.16xlarge | arm64 | 
| m7g.metal | arm64 | 
| m7gd.12xlarge | arm64 | 
| m7gd.16xlarge | arm64 | 
| m7gd.metal | arm64 | 
| m7i.12xlarge | x86\$164 | 
| m7i.16xlarge | x86\$164 | 
| m7i.24xlarge | x86\$164 | 
| m7i.48xlarge | x86\$164 | 
| m7i.metal-24xl | x86\$164 | 
| m7i.metal-48xl | x86\$164 | 
| m8a.16xlarge | x86\$164 | 
| m8a.24xlarge | x86\$164 | 
| m8a.48xlarge | x86\$164 | 
| m8a.metal-24xl | x86\$164 | 
| m8a.metal-48xl | x86\$164 | 
| m8azn.12xlarge | x86\$164 | 
| m8azn.24xlarge | x86\$164 | 
| m8azn.metal-12xl | x86\$164 | 
| m8azn.metal-24xl | x86\$164 | 
| 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\$164 | 
| m8i.32xlarge | x86\$164 | 
| m8i.48xlarge | x86\$164 | 
| m8i.96xlarge | x86\$164 | 
| m8i.metal-48xl | x86\$164 | 
| m8i.metal-96xl | x86\$164 | 
| m8id.24xlarge | x86\$164 | 
| m8id.32xlarge | x86\$164 | 
| m8id.48xlarge | x86\$164 | 
| m8id.96xlarge | x86\$164 | 
| m8id.metal-48xl | x86\$164 | 
| m8id.metal-96xl | x86\$164 | 

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


| Instance type | Architecture | 
| --- | --- | 
| c6a.12xlarge | x86\$164 | 
| c6a.16xlarge | x86\$164 | 
| c6a.24xlarge | x86\$164 | 
| c6a.32xlarge | x86\$164 | 
| c6a.48xlarge | x86\$164 | 
| c6a.metal | x86\$164 | 
| c6gn.4xlarge | arm64 | 
| c6gn.8xlarge | arm64 | 
| c6gn.12xlarge | arm64 | 
| c6gn.16xlarge | arm64 | 
| c6i.8xlarge | x86\$164 | 
| c6i.12xlarge | x86\$164 | 
| c6i.16xlarge | x86\$164 | 
| c6i.24xlarge | x86\$164 | 
| c6i.32xlarge | x86\$164 | 
| c6i.metal | x86\$164 | 
| c6id.8xlarge | x86\$164 | 
| c6id.12xlarge | x86\$164 | 
| c6id.16xlarge | x86\$164 | 
| c6id.24xlarge | x86\$164 | 
| c6id.32xlarge | x86\$164 | 
| c6id.metal | x86\$164 | 
| c6in.8xlarge | x86\$164 | 
| c6in.12xlarge | x86\$164 | 
| c6in.16xlarge | x86\$164 | 
| c6in.24xlarge | x86\$164 | 
| c6in.32xlarge | x86\$164 | 
| c6in.metal | x86\$164 | 
| c7a.12xlarge | x86\$164 | 
| c7a.16xlarge | x86\$164 | 
| c7a.24xlarge | x86\$164 | 
| c7a.32xlarge | x86\$164 | 
| c7a.48xlarge | x86\$164 | 
| c7a.metal-48xl | x86\$164 | 
| 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\$164 | 
| c7i.16xlarge | x86\$164 | 
| c7i.24xlarge | x86\$164 | 
| c7i.48xlarge | x86\$164 | 
| c7i.metal-24xl | x86\$164 | 
| c7i.metal-48xl | x86\$164 | 
| c8a.16xlarge | x86\$164 | 
| c8a.24xlarge | x86\$164 | 
| c8a.48xlarge | x86\$164 | 
| c8a.metal-24xl | x86\$164 | 
| c8a.metal-48xl | x86\$164 | 
| 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\$164 | 
| c8i.32xlarge | x86\$164 | 
| c8i.48xlarge | x86\$164 | 
| c8i.96xlarge | x86\$164 | 
| c8i.metal-48xl | x86\$164 | 
| c8i.metal-96xl | x86\$164 | 
| c8ib.12xlarge | x86\$164 | 
| c8ib.16xlarge | x86\$164 | 
| c8ib.24xlarge | x86\$164 | 
| c8ib.32xlarge | x86\$164 | 
| c8ib.48xlarge | x86\$164 | 
| c8ib.96xlarge | x86\$164 | 
| c8ib.metal-48xl | x86\$164 | 
| c8ib.metal-96xl | x86\$164 | 
| c8id.24xlarge | x86\$164 | 
| c8id.32xlarge | x86\$164 | 
| c8id.48xlarge | x86\$164 | 
| c8id.96xlarge | x86\$164 | 
| c8id.metal-48xl | x86\$164 | 
| c8id.metal-96xl | x86\$164 | 
| c8in.12xlarge | x86\$164 | 
| c8in.16xlarge | x86\$164 | 
| c8in.24xlarge | x86\$164 | 
| c8in.32xlarge | x86\$164 | 
| c8in.48xlarge | x86\$164 | 
| c8in.96xlarge | x86\$164 | 
| c8in.metal-48xl | x86\$164 | 
| c8in.metal-96xl | x86\$164 | 

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


| Instance type | Architecture | 
| --- | --- | 
| r6a.12xlarge | x86\$164 | 
| r6a.16xlarge | x86\$164 | 
| r6a.24xlarge | x86\$164 | 
| r6a.32xlarge | x86\$164 | 
| r6a.48xlarge | x86\$164 | 
| r6a.metal | x86\$164 | 
| r6i.8xlarge | x86\$164 | 
| r6i.12xlarge | x86\$164 | 
| r6i.16xlarge | x86\$164 | 
| r6i.24xlarge | x86\$164 | 
| r6i.32xlarge | x86\$164 | 
| r6i.metal | x86\$164 | 
| r6id.8xlarge | x86\$164 | 
| r6id.12xlarge | x86\$164 | 
| r6id.16xlarge | x86\$164 | 
| r6id.24xlarge | x86\$164 | 
| r6id.32xlarge | x86\$164 | 
| r6id.metal | x86\$164 | 
| r6idn.8xlarge | x86\$164 | 
| r6idn.12xlarge | x86\$164 | 
| r6idn.16xlarge | x86\$164 | 
| r6idn.24xlarge | x86\$164 | 
| r6idn.32xlarge | x86\$164 | 
| r6idn.metal | x86\$164 | 
| r6in.8xlarge | x86\$164 | 
| r6in.12xlarge | x86\$164 | 
| r6in.16xlarge | x86\$164 | 
| r6in.24xlarge | x86\$164 | 
| r6in.32xlarge | x86\$164 | 
| r6in.metal | x86\$164 | 
| r7a.12xlarge | x86\$164 | 
| r7a.16xlarge | x86\$164 | 
| r7a.24xlarge | x86\$164 | 
| r7a.32xlarge | x86\$164 | 
| r7a.48xlarge | x86\$164 | 
| r7a.metal-48xl | x86\$164 | 
| r7g.12xlarge | arm64 | 
| r7g.16xlarge | arm64 | 
| r7g.metal | arm64 | 
| r7gd.12xlarge | arm64 | 
| r7gd.16xlarge | arm64 | 
| r7gd.metal | arm64 | 
| r7i.12xlarge | x86\$164 | 
| r7i.16xlarge | x86\$164 | 
| r7i.24xlarge | x86\$164 | 
| r7i.48xlarge | x86\$164 | 
| r7i.metal-24xl | x86\$164 | 
| r7i.metal-48xl | x86\$164 | 
| r7iz.8xlarge | x86\$164 | 
| r7iz.12xlarge | x86\$164 | 
| r7iz.16xlarge | x86\$164 | 
| r7iz.32xlarge | x86\$164 | 
| r7iz.metal-16xl | x86\$164 | 
| r7iz.metal-32xl | x86\$164 | 
| r8a.16xlarge | x86\$164 | 
| r8a.24xlarge | x86\$164 | 
| r8a.48xlarge | x86\$164 | 
| r8a.metal-24xl | x86\$164 | 
| r8a.metal-48xl | x86\$164 | 
| 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\$164 | 
| r8i.32xlarge | x86\$164 | 
| r8i.48xlarge | x86\$164 | 
| r8i.96xlarge | x86\$164 | 
| r8i.metal-48xl | x86\$164 | 
| r8i.metal-96xl | x86\$164 | 
| r8id.24xlarge | x86\$164 | 
| r8id.32xlarge | x86\$164 | 
| r8id.48xlarge | x86\$164 | 
| r8id.96xlarge | x86\$164 | 
| r8id.metal-48xl | x86\$164 | 
| r8id.metal-96xl | x86\$164 | 
| u7i-6tb.112xlarge | x86\$164 | 
| u7i-8tb.112xlarge | x86\$164 | 
| u7i-12tb.224xlarge | x86\$164 | 
| u7in-16tb.224xlarge | x86\$164 | 
| u7in-24tb.224xlarge | x86\$164 | 
| u7in-32tb.224xlarge | x86\$164 | 
| u7inh-32tb.480xlarge | x86\$164 | 
| x2idn.16xlarge | x86\$164 | 
| x2idn.24xlarge | x86\$164 | 
| x2idn.32xlarge | x86\$164 | 
| x2idn.metal | x86\$164 | 
| x2iedn.8xlarge | x86\$164 | 
| x2iedn.16xlarge | x86\$164 | 
| x2iedn.24xlarge | x86\$164 | 
| x2iedn.32xlarge | x86\$164 | 
| x2iedn.metal | x86\$164 | 
| x8g.12xlarge | arm64 | 
| x8g.16xlarge | arm64 | 
| x8g.24xlarge | arm64 | 
| x8g.48xlarge | arm64 | 
| x8g.metal-24xl | arm64 | 
| x8g.metal-48xl | arm64 | 
| x8aedz.24xlarge | x86\$164 | 
| x8aedz.metal-24xl | x86\$164 | 
| x8i.24xlarge | x86\$164 | 
| x8i.32xlarge | x86\$164 | 
| x8i.48xlarge | x86\$164 | 
| x8i.64xlarge | x86\$164 | 
| x8i.96xlarge | x86\$164 | 
| x8i.metal-48xl | x86\$164 | 
| x8i.metal-96xl | x86\$164 | 

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


| Instance type | Architecture | 
| --- | --- | 
| g6.48xlarge | x86\$164 | 
| g6e.12xlarge | x86\$164 | 
| g6e.24xlarge | x86\$164 | 
| g6e.48xlarge | x86\$164 | 
| g7e.12xlarge | x86\$164 | 
| g7e.24xlarge | x86\$164 | 
| g7e.48xlarge | x86\$164 | 
| p5.4xlarge | x86\$164 | 
| p5.48xlarge | x86\$164 | 
| p5e.48xlarge | x86\$164 | 
| p5en.48xlarge | x86\$164 | 
| p6-b200.48xlarge | x86\$164 | 
| p6-b300.48xlarge | x86\$164 | 

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


| Instance type | Architecture | 
| --- | --- | 
| i4g.4xlarge | arm64 | 
| i4g.8xlarge | arm64 | 
| i4g.16xlarge | arm64 | 
| i4i.8xlarge | x86\$164 | 
| i4i.12xlarge | x86\$164 | 
| i4i.16xlarge | x86\$164 | 
| i4i.24xlarge | x86\$164 | 
| i4i.32xlarge | x86\$164 | 
| i4i.metal | x86\$164 | 
| i7i.12xlarge | x86\$164 | 
| i7i.16xlarge | x86\$164 | 
| i7i.24xlarge | x86\$164 | 
| i7i.48xlarge | x86\$164 | 
| i7i.metal-24xl | x86\$164 | 
| i7i.metal-48xl | x86\$164 | 
| i7ie.12xlarge | x86\$164 | 
| i7ie.18xlarge | x86\$164 | 
| i7ie.24xlarge | x86\$164 | 
| i7ie.48xlarge | x86\$164 | 
| i7ie.metal-24xl | x86\$164 | 
| i7ie.metal-48xl | x86\$164 | 
| 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 | 

------

## Prerequisites for Linux instances
<a name="ena-express-prereq-linux"></a>

To ensure that ENA Express can operate effectively, update the settings for your Linux instance as follows.
+ If your instance uses jumbo frames, run the following command to set your maximum transmission unit (MTU) to `8900`.

  ```
  [ec2-user ~]$ sudo ip link set dev eth0 mtu 8900
  ```
+ Increase the receiver (Rx) ring size, as follows:

  ```
  [ec2-user ~]$ ethtool -G device rx 8192
  ```
+ To maximize ENA Express bandwidth, configure your TCP queue limits as follows:

  1. Set the TCP small queue limit to 1MB or higher. This increases the amount of data that's queued for transmission on a socket.

     ```
     sudo sh -c 'echo 1048576 > /proc/sys/net/ipv4/tcp_limit_output_bytes'
     ```

  1. Disable byte queue limits on the eth device if they're enabled for your Linux distribution. This increases data queued for transmission for the device queue.

     ```
     sudo sh -c 'for txq in /sys/class/net/eth0/queues/tx-*; do echo max > ${txq}/byte_queue_limits/limit_min; done'
     ```
**Note**  
The ENA driver for the Amazon Linux distribution disables byte queue limits by default.
+ To minimize ENA Express TCP traffic latency, you can disable the TCP autocorking feature. This might result in a minimal increase in packet overhead:

  ```
  sudo bash -c 'echo 0 > /proc/sys/net/ipv4/tcp_autocorking'
  ```

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

To check your Linux instance configuration for optimal ENA Express performance, you can run the following script that's available on the Amazon GitHub repository:

[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 runs a series of tests and suggests both recommended and required configuration changes.

# Review ENA Express settings for your EC2 instance
<a name="ena-express-list-view"></a>

You can verify the ENA Express settings by instance or by network interface. To update the ENA Express settings, see [Configure ENA Express settings for your EC2 instance](ena-express-configure.md).

------
#### [ Console ]

**To view ENA Express settings for a network interface**

1. Open the Amazon EC2 console at [https://console.aws.amazon.com/ec2/](https://console.aws.amazon.com/ec2/).

1. In the left navigation pane, choose **Network interfaces**.

1. Select a network interface to see the details for that instance. You can choose the **Network interface ID** link to open the detail page, or you can select the checkbox on the left side of the list to view details in the detail pane at the bottom of the page.

1. In the **Network interface attachment** section on the **Details** tab or detail page, review settings for **ENA Express** and **ENA Express UDP**.

**To view ENA Express settings for an instance**

1. Open the Amazon EC2 console at [https://console.aws.amazon.com/ec2/](https://console.aws.amazon.com/ec2/).

1. In the left navigation pane, choose **Instances**.

1. Select an instance to see the details for that instance. You can choose the **Instance ID** link to open the detail page, or you can select the checkbox on the left side of the list to view details in the detail pane at the bottom of the page.

1. In the **Network interfaces** section on the **Networking** tab, scroll right to review settings for **ENA Express** and **ENA Express UDP**.

------
#### [ AWS CLI ]

**To get the ENA Express settings for an instance**  
Use the [https://docs.aws.amazon.com/cli/latest/reference/describe-instances.html](https://docs.aws.amazon.com/cli/latest/reference/describe-instances.html) command. This command example returns a list of ENA Express configurations for the network interfaces attached to each of the running instances that are specified by the `--instance-ids` parameter.

```
aws ec2 describe-instances \
    --instance-ids i-1234567890abcdef0 i-0598c7d356eba48d7 \
    --query 'Reservations[*].Instances[*].[InstanceId, NetworkInterfaces[*].Attachment.EnaSrdSpecification]'
```

The following is example output.

```
[
    [
        [
            "i-1234567890abcdef0",
            [
                {
                    "EnaSrdEnabled": true,
                    "EnaSrdUdpSpecification": {
                        "EnaSrdUdpEnabled": false
                    }
                }
            ]
        ]
    ],
    [
        [
            "i-0598c7d356eba48d7",
            [
            {
                    "EnaSrdEnabled": true,
                    "EnaSrdUdpSpecification": {
                        "EnaSrdUdpEnabled": false
                    }
                }
            ]
        ]
    ]
]
```

**To get the ENA Express settings for a network interface**  
Use the [https://docs.aws.amazon.com/cli/latest/reference/describe-network-interfaces.html](https://docs.aws.amazon.com/cli/latest/reference/describe-network-interfaces.html) command.

```
aws ec2 describe-network-interfaces \
    --network-interface-ids eni-1234567890abcdef0 \
    --query NetworkInterfaces[].[NetworkInterfaceId,Attachment.EnaSrdSpecification]
```

The following is example output.

```
[
    [
        "eni-1234567890abcdef0",
        {
            "EnaSrdEnabled": true,
            "EnaSrdUdpSpecification": {
                "EnaSrdUdpEnabled": false
            }
        }
    ]
]
```

------
#### [ PowerShell ]

**To get the ENA Express settings for a network interface**  
Use the [https://docs.aws.amazon.com/powershell/latest/reference/items/Get-EC2NetworkInterface.html](https://docs.aws.amazon.com/powershell/latest/reference/items/Get-EC2NetworkInterface.html) cmdlet.

```
Get-EC2NetworkInterface `
    -NetworkInterfaceId eni-1234567890abcdef0 | `
Select-Object `
    Association, 
    NetworkInterfaceId, 
    OwnerId, 
    @{Name = 'AttachTime'; Expression = { $_.Attachment.AttachTime } },
    @{Name = 'AttachmentId'; Expression = { $_.Attachment.AttachmentId } },
    @{Name = 'DeleteOnTermination'; Expression = { $_.Attachment.DeleteOnTermination } },
    @{Name = 'NetworkCardIndex'; Expression = { $_.Attachment.NetworkCardIndex } },
    @{Name = 'InstanceId'; Expression = { $_.Attachment.InstanceId } },
    @{Name = 'InstanceOwnerId'; Expression = { $_.Attachment.InstanceOwnerId } },
    @{Name = 'Status'; Expression = { $_.Attachment.Status } },
    @{Name = 'EnaSrdEnabled'; Expression = { $_.Attachment.EnaSrdSpecification.EnaSrdEnabled } },
    @{Name = 'EnaSrdUdpEnabled'; Expression = { $_.Attachment.EnaSrdSpecification.EnaSrdUdpSpecification.EnaSrdUdpEnabled } }
```

The following is example output.

```
Association         : 
NetworkInterfaceId  : eni-0d1234e5f6a78901b
OwnerId             : 111122223333
AttachTime          : 6/11/2022 1:13:11 AM
AttachmentId        : eni-attach-0d1234e5f6a78901b
DeleteOnTermination : True
NetworkCardIndex    : 0
InstanceId          : i-1234567890abcdef0
InstanceOwnerId     : 111122223333
Status              : attached
EnaSrdEnabled       : True
EnaSrdUdpEnabled    : False
```

------

# Configure ENA Express settings for your EC2 instance
<a name="ena-express-configure"></a>

You can configure ENA Express for supported EC2 instance types without needing to install any additional software. For more information, see [Supported instance types for ENA Express](ena-express.md#ena-express-supported-instance-types).

------
#### [ Console ]

**To manage ENA Express for a network interface**

1. Open the Amazon EC2 console at [https://console.aws.amazon.com/ec2/](https://console.aws.amazon.com/ec2/).

1. In the left navigation pane, choose **Network interfaces**.

1. Select a network interface that is attached to an instance. You can choose the **Network interface ID** link to open the detail page, or you can select the checkbox on the left side of the list.

1. Choose **Manage ENA Express** from the **Action** menu at the top right side of the page. This opens the **Manage ENA Express** dialog, with the selected network interface ID and current settings displayed.

   If the network interface you selected is not attached to an instance, this action does not appear in the menu.

1. To use **ENA Express**, select the **Enable** checkbox.

1. When ENA Express is enabled, you can configure UDP settings. To use **ENA Express UDP**, select the **Enable** checkbox.

1. To save your settings, choose **Save**.

**To manage ENA Express for an instance**

1. Open the Amazon EC2 console at [https://console.aws.amazon.com/ec2/](https://console.aws.amazon.com/ec2/).

1. In the left navigation pane, choose **Instances**.

1. Select the instance that you want to manage. You can choose the **Instance ID** to open the detail page, or you can select the checkbox on the left side of the list.

1. Select the **Network interface** to configure for your instance.

1. Choose **Manage ENA Express** from the **Action** menu at the top right side of the page.

1. To configure ENA Express for a network interface that's attached to your instance, select it from the **Network interface** list.

1. To use **ENA Express** for the selected network interface attachment, select the **Enable** checkbox.

1. When ENA Express is enabled, you can configure UDP settings. To use **ENA Express UDP**, select the **Enable** checkbox.

1. To save your settings, choose **Save**.

**To configure ENA Express when you attach a network interface**

1. Open the Amazon EC2 console at [https://console.aws.amazon.com/ec2/](https://console.aws.amazon.com/ec2/).

1. In the left navigation pane, choose **Network interfaces**.

1. Select a network interface that is not attached to an instance (**Status** is **Available**). You can choose the **Network interface ID** link to open the detail page, or you can select the checkbox on the left side of the list.

1. Select the **Instance** that you'll attach to.

1. To use **ENA Express** after you attach the network interface to the instance, select the **Enable** checkbox.

1. When ENA Express is enabled, you can configure UDP settings. To use **ENA Express UDP**, select the **Enable** checkbox.

1. To attach the network interface to the instance and save your ENA Express settings, choose **Attach**.

------
#### [ AWS CLI ]

**To configure ENA Express when you attach a network interface**  
Use the [https://docs.aws.amazon.com/cli/latest/reference/;attach-network-interface.html](https://docs.aws.amazon.com/cli/latest/reference/;attach-network-interface.html) command, as shown in the following examples.

**Example 1: Use ENA Express for TCP traffic, but not UDP traffic**  
This example configures `EnaSrdEnabled` as `true`, and allows `EnaSrdUdpEnabled` to default to `false`.

```
aws ec2 attach-network-interface \
    --network-interface-id eni-1234567890abcdef0 \
    --instance-id i-1234567890abcdef0 \
    --device-index 1 \
    --ena-srd-specification 'EnaSrdEnabled=true'
```

**Example 2: Use ENA Express for both TCP traffic and UDP traffic**  
This example configures both `EnaSrdEnabled` and `EnaSrdUdpEnabled` as `true`.

```
aws ec2 attach-network-interface \
    --network-interface-id eni-1234567890abcdef0 \
    --instance-id i-1234567890abcdef0 \
    --device-index 1 \
    --ena-srd-specification 'EnaSrdEnabled=true,EnaSrdUdpSpecification={EnaSrdUdpEnabled=true}'
```

**To update ENA Express settings for a network interface attachment**  
Use the [https://docs.aws.amazon.com/cli/latest/reference/modify-network-interface-attribute.html](https://docs.aws.amazon.com/cli/latest/reference/modify-network-interface-attribute.html) command as shown in the following examples.

**Example 1: Use ENA Express for TCP traffic, but not UDP traffic**  
This example configures `EnaSrdEnabled` as `true`, and allows `EnaSrdUdpEnabled` to default to `false` if it has never been set previously.

```
aws ec2 modify-network-interface-attribute \
    --network-interface-id eni-1234567890abcdef0 \
    --ena-srd-specification 'EnaSrdEnabled=true'
```

**Example 2: Use ENA Express for both TCP traffic and UDP traffic**  
This example configures both `EnaSrdEnabled` and `EnaSrdUdpEnabled` as `true`.

```
aws ec2 modify-network-interface-attribute \
    --network-interface-id eni-1234567890abcdef0 \
    --ena-srd-specification 'EnaSrdEnabled=true,EnaSrdUdpSpecification={EnaSrdUdpEnabled=true}'
```

**Example 3: Stop using ENA Express for UDP traffic**  
This example configures `EnaSrdUdpEnabled` as `false`.

```
aws ec2 modify-network-interface-attribute \
    --network-interface-id eni-1234567890abcdef0 \
    --ena-srd-specification 'EnaSrdUdpSpecification={EnaSrdUdpEnabled=false}'
```

------
#### [ PowerShell ]

**To configure ENA Express when you attach a network interface**  
Use the [https://docs.aws.amazon.com/powershell/latest/reference/items/Add-EC2NetworkInterface.html](https://docs.aws.amazon.com/powershell/latest/reference/items/Add-EC2NetworkInterface.html) cmdlet as shown in the following examples.

**Example 1: Use ENA Express for TCP traffic, but not UDP traffic**  
This example configures `EnaSrdEnabled` as `true`, and allows `EnaSrdUdpEnabled` to default to `false`.

```
Add-EC2NetworkInterface `
    -NetworkInterfaceId eni-1234567890abcdef0 `
    -InstanceId i-1234567890abcdef0 `
    -DeviceIndex 1 `
    -EnaSrdSpecification_EnaSrdEnabled $true
```

**Example 2: Use ENA Express for both TCP traffic and UDP traffic**  
This example configures both `EnaSrdEnabled` and `EnaSrdUdpEnabled` as `true`.

```
Add-EC2NetworkInterface `
    -NetworkInterfaceId eni-1234567890abcdef0 `
    -InstanceId i-1234567890abcdef0 `
    -DeviceIndex 1 `
    -EnaSrdSpecification_EnaSrdEnabled $true `
    -EnaSrdUdpSpecification_EnaSrdUdpEnabled $true
```

**To configure ENA Express settings for your network interface attachment**  
Use the [https://docs.aws.amazon.com/powershell/latest/reference/items/Edit-EC2NetworkInterfaceAttribute.html](https://docs.aws.amazon.com/powershell/latest/reference/items/Edit-EC2NetworkInterfaceAttribute.html) cmdlet as shown in the following examples.

**Example 1: Use ENA Express for TCP traffic, but not UDP traffic**  
This example configures `EnaSrdEnabled` as `true`, and allows `EnaSrdUdpEnabled` to default to `false` if it has never been set previously.

```
Edit-EC2NetworkInterfaceAttribute `
    -NetworkInterfaceId eni-1234567890abcdef0 `
    -EnaSrdSpecification_EnaSrdEnabled $true ; 
Get-EC2NetworkInterface -NetworkInterfaceId eni-0123f4567890a1b23 | `
Select-Object `
    NetworkInterfaceId, 
    @{Name = 'EnaSrdEnabled'; Expression = { $_.Attachment.EnaSrdSpecification.EnaSrdEnabled }}, 
    @{Name = 'EnaSrdUdpEnabled'; Expression = { $_.Attachment.EnaSrdSpecification.EnaSrdUdpSpecification.EnaSrdUdpEnabled }} | `
Format-List
```

**Example 2: Use ENA Express for both TCP traffic and UDP traffic**  
This example configures both `EnaSrdEnabled` and `EnaSrdUdpEnabled` as `true`.

```
Edit-EC2NetworkInterfaceAttribute `
    -NetworkInterfaceId eni-1234567890abcdef0 `
    -EnaSrdSpecification_EnaSrdEnabled $true `
    -EnaSrdSpecification_EnaSrdUdpSpecification_EnaSrdUdpEnabled $true ;
Get-EC2NetworkInterface -NetworkInterfaceId eni-1234567890abcdef0 | `
Select-Object `
    NetworkInterfaceId, 
    @{Name = 'EnaSrdEnabled'; Expression = { $_.Attachment.EnaSrdSpecification.EnaSrdEnabled }}, 
    @{Name = 'EnaSrdUdpEnabled'; Expression = { $_.Attachment.EnaSrdSpecification.EnaSrdUdpSpecification.EnaSrdUdpEnabled }} | `
Format-List
```

**Example 3: Stop using ENA Express for UDP traffic**  
This example configures `EnaSrdUdpEnabled` as `false`.

```
Edit-EC2NetworkInterfaceAttribute `
    -NetworkInterfaceId eni-0123f4567890a1b23 `
    -EnaSrdSpecification_EnaSrdUdpSpecification_EnaSrdUdpEnabled $false ; 
Get-EC2NetworkInterface -NetworkInterfaceId eni-0123f4567890a1b23 | `
Select-Object `
    NetworkInterfaceId, 
    @{Name = 'EnaSrdEnabled'; Expression = { $_.Attachment.EnaSrdSpecification.EnaSrdEnabled }}, 
    @{Name = 'EnaSrdUdpEnabled'; Expression = { $_.Attachment.EnaSrdSpecification.EnaSrdUdpSpecification.EnaSrdUdpEnabled }} | `
Format-List
```

------

## Configure ENA Express at launch
<a name="ena-express-configure-on-launch"></a>

You can use one of the following methods to configure ENA Express directly when you launch an instance. The specified links refer you to the AWS Management Console instructions for these methods.
+ **Launch instance wizard** – You can configure ENA Express at launch with the launch instance wizard. For more information, see **Advanced network configuration** in the [Network settings](ec2-instance-launch-parameters.md#liw-network-settings) for the launch instance wizard.
+ **Launch template** – You can configure ENA Express at launch when you use a launch template. For more information, see the [Create an Amazon EC2 launch template](create-launch-template.md) page, then expand the **Network settings** section and review the **Advanced network configuration**.