# Receive Side Scaling

When Receive Side Scaling (RSS) is enabled, all of the receive data processing for a particular TCP connection is shared across multiple processors or processor cores. Without RSS all of the processing is performed by a single processor, resulting in less efficient system cache utilization.

NOTES:

- This setting has no effect if your system has only one processing unit.
- RSS must be enabled for Intel® I/O Acceleration Technology to function.
- To enable RSS on Microsoft* Windows Server* 2003, you must install Microsoft's Scalable Networking Pack. The Scalable Networking Pack is part of Windows Server 2003 SP2. It is not included in SP1 and requires a separate download. See http://www.microsoft.com for more information.

## RSS Configuration

RSS is enabled on the Advanced tab of the adapter property sheet. If your adapter does not support RSS, or if your operating system does not support it, the RSS setting will not be displayed.

## Receive Side Scaling Queues

This setting allocates queue space to buffer transactions between the network adapter and CPU(s).

Range

- 1 queue is used when low CPU utilization is required.
- 2 queues are used when good throughput and low CPU utilization are required.
- 4 or more queues are used for applications that demand maximum throughput and translations per second.

## Starting RSS CPU

This setting allows you to set the preferred starting RSS processor. Change this setting if the current processor is dedicated to other processes. The setting range is from 0 to the number of logical CPUs - 1. In Server 2008 R2, RSS will only use CPUs in group 0 (CPUs 0 through 63).

## Preferred NUMA Node

This setting allows you to choose the preferred NUMA (Non-Uniform Memory Access) node to be used for memory allocations made by the network adapter. In addition the system will attempt to use the CPUs from the preferred NUMA node first for the purposes of RSS. On NUMA platforms, memory access latency is dependent on the memory location. Allocation of memory from the closest node helps improve performance. The Windows Task Manager shows the NUMA Node ID for each processor.

| Note: This setting only affects NUMA systems. It will have no effect on non-NUMA systems.

## Teaming

- If RSS is not enabled for all adapters in a team, RSS will automatically be disabled for the team.
- If an adapter that does not support RSS is added to a team, RSS will automatically be disabled for the team.
- If a non-Intel adapter is added to a team, RSS will automatically be disabled for the team.
- Non-Intel adapters with RSS enabled cannot be added to a team.