TCP: Difference between revisions
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== Portable APIs == | == Portable APIs == | ||
* TCP_NODELAY: Disable [[Nagle's algorithm]] (coalescing of small packets until an ACK is received or a retransmission triggered). See the [[Linux APIs#IPPROTO_TCP|Linux APIs]] page for interactions with TCP_CORK on that platform. | * TCP_NODELAY: Disable [[Nagle's algorithm]] (coalescing of small packets until an ACK is received or a retransmission triggered). See the [[Linux APIs#IPPROTO_TCP|Linux APIs]] page for interactions with TCP_CORK on that platform. | ||
==Offloading/Coalescing== | |||
LRO/TSO are safe to use on routers and bridges so long as all interfaces involved support the technique. | |||
===LRO=== | |||
Large receive offload. Cannot guarantee refragmentation, and thus ought not generally be used on bridges or routers. | |||
===GRO=== | |||
Generic receive offload. Generalizes LRO to guarantee possibility of refragmentation, but coalesces a proper subset of packets suitable for LRO. | |||
===TSO=== | |||
TCP segmentation offload, also known as TCP Large Send. | |||
===GSO=== | |||
Generic segmentation offload, introduced in Linux 2.6.18. Generalizes TSO to guarantee possibility of refragmentation. | |||
==Tuning== | ==Tuning== | ||
===TCP auto-tuning on Linux=== | ===TCP auto-tuning on Linux=== | ||
* netdev 2009-03-11, "[http://patchwork.ozlabs.org/patch/24296/ TCP rx window autotuning harmful at LAN context]" | * netdev 2009-03-11, "[http://patchwork.ozlabs.org/patch/24296/ TCP rx window autotuning harmful at LAN context]" | ||
* The Pittsburgh Supercomputing Center's [http://www.psc.edu/networking/projects/tcptune/#Linux Linux TCP notes] | * The Pittsburgh Supercomputing Center's [http://www.psc.edu/networking/projects/tcptune/#Linux Linux TCP notes] | ||
===TCP auto-tuning on FreeBSD=== | |||
* Finally introduced in [FreeBSD 7.2] by [http://people.freebsd.org/~andre/ Andre Oppermann]: | |||
<pre>With TCP send buffer auto scaling and the default values below it supports 20Mbit/s at 100ms and 10Mbit/s at 200ms. Both read and write buffer are auto-sized.</pre> | |||
== See also == | == See also == | ||
* [[Linux APIs#IPPROTO_TCP|Linux's]] TCP socket options | * [[Linux APIs#IPPROTO_TCP|Linux's]] TCP socket options | ||
* [[FreeBSD APIs#IPPROTO_TCP|FreeBSD's]] TCP socket options | * [[FreeBSD APIs#IPPROTO_TCP|FreeBSD's]] TCP socket options | ||
* [http://linuxgazette.net/135/pfeiffer.html TCP and Linux' Pluggable Congestion Control Algorithms], a 2007 Linux Gazette article by René Pfeiffer | |||
* [http://thread.gmane.org/gmane.linux.network/114003 'net: Generic Receive Offload], Herbert Xu 2008-12-12 linux-net post | |||
* [http://www.linuxfoundation.org/collaborate/workgroups/networking/gso GSO], The Linux Foundation | |||
* [http://kerneltrap.org/node/397 Linux: TCP Segmentation Offload], KernelTrap 2002-09-03 | |||
[[CATEGORY: Networking]] | |||