Multi-core network packet steering: Difference between revisions

Revision as of 13:39, 10 July 2025

Revision as of 13:43, 10 July 2025

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=== RSS ===

[[File:RSS architecture.png|upright=1.7|thumb|Simple view of the receive side scaling architecture]]

Receive Side Scaling (RSS) is ana hardware supported technique, leveraging an [[indirection|indirection table]] indexed by the last bits of the result provided by ana [[hash function]], taking as inputs the [[Header (computing)|header fields]] of the packets.

The hash function input is usually customizable and the header fields used can vary between use case and implementations.

Some notable exampleexamples of header fields usedchosen as keys for the hash are the [[Internet Protocol|layer 3 IP]] source and destination addresses, the protocol and the [[transport layer|layer 4]] source and destination portports.

In this way, packets corresponding to the same flow will be directed to the same receiving queue, without loosing the original order, causing an [[Out-of-order delivery|out-of-order delivery]]. Moreover all incoming flows will be [[Load balancing (computing)|load balanced]] across all the available cores thanks to the hash function properties. <br>

Another important feature introduced by the indirection table is the capability of changing the mapping of flows to the cores without having to change the hash function, but by simply updating the table entries.<ref>{{Cite web|title=RSS intel doc|url=https://www.intel.com/content/dam/support/us/en/documents/network/sb/318483001us2.pdf|access-date=2025-07-08|website=earn.microsoft.com|language=en-US}}</ref><ref name="RSS overview by microsoft" /><ref>{{Cite web|title=RSS by redhat|url=https://docs.redhat.com/en/documentation/red_hat_enterprise_linux/6/html/performance_tuning_guide/network-rss|access-date=2025-07-08|website=docs.redhat.com|publisher=Red Hat Documentation|language=en-US}}</ref><ref name="RSS kernel linux docs" /><ref>{{Cite web|title=Receive-side scaling enhancements in windows server 2008|url=https://download.microsoft.com/download/a/d/f/adf1347d-08dc-41a4-9084-623b1194d4b2/rss_server2008.docx|access-date=2025-07-08|website=microsoft.com|publisher=Microsoft|language=en-US}}</ref>