X-Git-Url: http://git.onelab.eu/?p=iproute2.git;a=blobdiff_plain;f=tc-sfq.8;fp=tc-sfq.8;h=0000000000000000000000000000000000000000;hp=337c7950193b5864835a7f80781cd394f10de622;hb=3331a68859fd71047bb1f309048960b48eab2d83;hpb=2bd4a72f2100be7ad7d9518cb1d49bb2a5b71994 diff --git a/tc-sfq.8 b/tc-sfq.8 deleted file mode 100644 index 337c795..0000000 --- a/tc-sfq.8 +++ /dev/null @@ -1,107 +0,0 @@ -.TH TC 8 "8 December 2001" "iproute2" "Linux" -.SH NAME -sfq \- Stochastic Fairness Queueing -.SH SYNOPSIS -.B tc qdisc ... perturb -seconds -.B quantum -bytes - -.SH DESCRIPTION - -Stochastic Fairness Queueing is a classless queueing discipline available for -traffic control with the -.BR tc (8) -command. - -SFQ does not shape traffic but only schedules the transmission of packets, based on 'flows'. -The goal is to ensure fairness so that each flow is able to send data in turn, thus preventing -any single flow from drowning out the rest. - -This may in fact have some effect in mitigating a Denial of Service attempt. - -SFQ is work-conserving and therefore always delivers a packet if it has one available. -.SH ALGORITHM -On enqueueing, each packet is assigned to a hash bucket, based on -.TP -(i) -Source address -.TP -(ii) -Destination address -.TP -(iii) -Source port -.P -If these are available. SFQ knows about ipv4 and ipv6 and also UDP, TCP and ESP. -Packets with other protocols are hashed based on the 32bits representation of their -destination and the socket they belong to. A flow corresponds mostly to a TCP/IP -connection. - -Each of these buckets should represent a unique flow. Because multiple flows may -get hashed to the same bucket, the hashing algorithm is perturbed at configurable -intervals so that the unfairness lasts only for a short while. Perturbation may -however cause some inadvertent packet reordering to occur. - -When dequeuing, each hashbucket with data is queried in a round robin fashion. - -The compile time maximum length of the SFQ is 128 packets, which can be spread over -at most 128 buckets of 1024 available. In case of overflow, tail-drop is performed -on the fullest bucket, thus maintaining fairness. - -.SH PARAMETERS -.TP -perturb -Interval in seconds for queue algorithm perturbation. Defaults to 0, which means that -no perturbation occurs. Do not set too low for each perturbation may cause some packet -reordering. Advised value: 10 -.TP -quantum -Amount of bytes a flow is allowed to dequeue during a round of the round robin process. -Defaults to the MTU of the interface which is also the advised value and the minimum value. - -.SH EXAMPLE & USAGE - -To attach to device ppp0: -.P -# tc qdisc add dev ppp0 root sfq perturb 10 -.P -Please note that SFQ, like all non-shaping (work-conserving) qdiscs, is only useful -if it owns the queue. -This is the case when the link speed equals the actually available bandwidth. This holds -for regular phone modems, ISDN connections and direct non-switched ethernet links. -.P -Most often, cable modems and DSL devices do not fall into this category. The same holds -for when connected to a switch and trying to send data to a congested segment also -connected to the switch. -.P -In this case, the effective queue does not reside within Linux and is therefore not -available for scheduling. -.P -Embed SFQ in a classful qdisc to make sure it owns the queue. - -.SH SOURCE -.TP -o -Paul E. McKenney "Stochastic Fairness Queuing", -IEEE INFOCOMM'90 Proceedings, San Francisco, 1990. - -.TP -o -Paul E. McKenney "Stochastic Fairness Queuing", -"Interworking: Research and Experience", v.2, 1991, p.113-131. - -.TP -o -See also: -M. Shreedhar and George Varghese "Efficient Fair -Queuing using Deficit Round Robin", Proc. SIGCOMM 95. - -.SH SEE ALSO -.BR tc (8) - -.SH AUTHOR -Alexey N. Kuznetsov, . This manpage maintained by -bert hubert - -