When the kernel has several packets to send out over a network device, it has to decide which ones to send first, which ones to delay, and which ones to drop. This is the job of the queueing disciplines, several different algorithms for how to do this "fairly" have been proposed. If you say N here, you will get the standard packet scheduler, which is a FIFO (first come, first served). If you say Y here, you will be able to choose from among several alternative algorithms which can then be attached to different network devices. This is useful for example if some of your network devices are real time devices that need a certain minimum data flow rate, or if you need to limit the maximum data flow rate for traffic which matches specified criteria. This code is considered to be experimental. To administer these schedulers, you'll need the user-level utilities from the package iproute2+tc at <ftp://ftp.tux.org/pub/net/ip-routing/>. That package also contains some documentation; for more, check out <http://www.linuxfoundation.org/collaborate/workgroups/networking/iproute2>. This Quality of Service (QoS) support will enable you to use Differentiated Services (diffserv) and Resource Reservation Protocol (RSVP) on your Linux router if you also say Y to the corresponding classifiers below. Documentation and software is at <http://diffserv.sourceforge.net/>. If you say Y here and to "/proc file system" below, you will be able to read status information about packet schedulers from the file /proc/net/psched. The available schedulers are listed in the following questions; you can say Y to as many as you like. If unsure, say N now.
Say Y here if you want to use the Class-Based Queueing (CBQ) packet scheduling algorithm. This algorithm classifies the waiting packets into a tree-like hierarchy of classes; the leaves of this tree are in turn scheduled by separate algorithms. See the top of <file:net/sched/sch_cbq.c> for more details. CBQ is a commonly used scheduler, so if you're unsure, you should say Y here. Then say Y to all the queueing algorithms below that you want to use as leaf disciplines. To compile this code as a module, choose M here: the module will be called sch_cbq.
Say Y here if you want to use the Hierarchical Token Buckets (HTB) packet scheduling algorithm. See <http://luxik.cdi.cz/~devik/qos/htb/> for complete manual and in-depth articles. HTB is very similar to CBQ regarding its goals however is has different properties and different algorithm. To compile this code as a module, choose M here: the module will be called sch_htb.
Say Y here if you want to use the Hierarchical Fair Service Curve (HFSC) packet scheduling algorithm. To compile this code as a module, choose M here: the module will be called sch_hfsc.
Say Y here if you want to use the ATM pseudo-scheduler. This provides a framework for invoking classifiers, which in turn select classes of this queuing discipline. Each class maps the flow(s) it is handling to a given virtual circuit. See the top of <file:net/sched/sch_atm.c> for more details. To compile this code as a module, choose M here: the module will be called sch_atm.
Say Y here if you want to use an n-band priority queue packet scheduler. To compile this code as a module, choose M here: the module will be called sch_prio.
Say Y here if you want to use an n-band queue packet scheduler to support devices that have multiple hardware transmit queues. To compile this code as a module, choose M here: the module will be called sch_multiq.
Say Y here if you want to use the Random Early Detection (RED) packet scheduling algorithm. See the top of <file:net/sched/sch_red.c> for more details. To compile this code as a module, choose M here: the module will be called sch_red.
Say Y here if you want to use the Stochastic Fair Blue (SFB) packet scheduling algorithm. See the top of <file:net/sched/sch_sfb.c> for more details. To compile this code as a module, choose M here: the module will be called sch_sfb.
Say Y here if you want to use the Stochastic Fairness Queueing (SFQ) packet scheduling algorithm. See the top of <file:net/sched/sch_sfq.c> for more details. To compile this code as a module, choose M here: the module will be called sch_sfq.
Say Y here if you want to use the True Link Equalizer (TLE) packet scheduling algorithm. This queueing discipline allows the combination of several physical devices into one virtual device. See the top of <file:net/sched/sch_teql.c> for more details. To compile this code as a module, choose M here: the module will be called sch_teql.
Say Y here if you want to use the Token Bucket Filter (TBF) packet scheduling algorithm. See the top of <file:net/sched/sch_tbf.c> for more details. To compile this code as a module, choose M here: the module will be called sch_tbf.
Say Y here if you want to use the Generic Random Early Detection (GRED) packet scheduling algorithm for some of your network devices (see the top of <file:net/sched/sch_red.c> for details and references about the algorithm). To compile this code as a module, choose M here: the module will be called sch_gred.
Say Y if you want to schedule packets according to the Differentiated Services architecture proposed in RFC 2475. Technical information on this method, with pointers to associated RFCs, is available at <http://www.gta.ufrj.br/diffserv/>. To compile this code as a module, choose M here: the module will be called sch_dsmark.
Say Y if you want to emulate network delay, loss, and packet re-ordering. This is often useful to simulate networks when testing applications or protocols. To compile this driver as a module, choose M here: the module will be called sch_netem. If unsure, say N.
Say Y here if you want to use the Deficit Round Robin (DRR) packet scheduling algorithm. To compile this driver as a module, choose M here: the module will be called sch_drr. If unsure, say N.
Say Y here if you want to use the Multi-queue Priority scheduler. This scheduler allows QOS to be offloaded on NICs that have support for offloading QOS schedulers. To compile this driver as a module, choose M here: the module will be called sch_mqprio. If unsure, say N.
Say Y here if you want to use the CHOKe packet scheduler (CHOose and Keep for responsive flows, CHOose and Kill for unresponsive flows). This is a variation of RED which trys to penalize flows that monopolize the queue. To compile this code as a module, choose M here: the module will be called sch_choke.
Say Y here if you want to use the Quick Fair Queueing Scheduler (QFQ) packet scheduling algorithm. To compile this driver as a module, choose M here: the module will be called sch_qfq. If unsure, say N.
Say Y here if you want to use classifiers for incoming packets. If unsure, say Y. To compile this code as a module, choose M here: the module will be called sch_ingress.
Say Y here if you want to be able to classify packets using only extended matches and actions. To compile this code as a module, choose M here: the module will be called cls_basic.
Say Y here if you want to be able to classify packets based on traffic control indices. You will want this feature if you want to implement Differentiated Services together with DSMARK. To compile this code as a module, choose M here: the module will be called cls_tcindex.
If you say Y here, you will be able to classify packets according to the route table entry they matched. To compile this code as a module, choose M here: the module will be called cls_route.
If you say Y here, you will be able to classify packets according to netfilter/firewall marks. To compile this code as a module, choose M here: the module will be called cls_fw.
Say Y here to be able to classify packets using a universal 32bit pieces based comparison scheme. To compile this code as a module, choose M here: the module will be called cls_u32.
Say Y here to make u32 gather additional statistics useful for fine tuning u32 classifiers.
Say Y here to be able to use netfilter marks as u32 key.
The Resource Reservation Protocol (RSVP) permits end systems to request a minimum and maximum data flow rate for a connection; this is important for real time data such as streaming sound or video. Say Y here if you want to be able to classify outgoing packets based on their RSVP requests. To compile this code as a module, choose M here: the module will be called cls_rsvp.
The Resource Reservation Protocol (RSVP) permits end systems to request a minimum and maximum data flow rate for a connection; this is important for real time data such as streaming sound or video. Say Y here if you want to be able to classify outgoing packets based on their RSVP requests and you are using the IPv6 protocol. To compile this code as a module, choose M here: the module will be called cls_rsvp6.
If you say Y here, you will be able to classify packets based on a configurable combination of packet keys. This is mostly useful in combination with SFQ. To compile this code as a module, choose M here: the module will be called cls_flow.
Say Y here if you want to classify packets based on the control cgroup of their process. To compile this code as a module, choose M here: the module will be called cls_cgroup.
Say Y here if you want to use extended matches on top of classifiers and select the extended matches below. Extended matches are small classification helpers not worth writing a separate classifier for. A recent version of the iproute2 package is required to use extended matches.
Size of the local stack variable used while evaluating the tree of ematches. Limits the depth of the tree, i.e. the number of encapsulated precedences. Every level requires 4 bytes of additional stack space.
Say Y here if you want to be able to classify packets based on simple packet data comparisons for 8, 16, and 32bit values. To compile this code as a module, choose M here: the module will be called em_cmp.
Say Y here if you want to be able to classify packets based on multiple byte comparisons mainly useful for IPv6 address comparisons. To compile this code as a module, choose M here: the module will be called em_nbyte.
Say Y here if you want to be able to classify packets using the famous u32 key in combination with logic relations. To compile this code as a module, choose M here: the module will be called em_u32.
Say Y here if you want to be able to classify packets based on metadata such as load average, netfilter attributes, socket attributes and routing decisions. To compile this code as a module, choose M here: the module will be called em_meta.
Say Y here if you want to be able to classify packets based on textsearch comparisons. To compile this code as a module, choose M here: the module will be called em_text.
Say Y here if you want to use traffic control actions. Actions get attached to classifiers and are invoked after a successful classification. They are used to overwrite the classification result, instantly drop or redirect packets, etc. A recent version of the iproute2 package is required to use extended matches.
Say Y here if you want to do traffic policing, i.e. strict bandwidth limiting. This action replaces the existing policing module. To compile this code as a module, choose M here: the module will be called act_police.
Say Y here to take generic actions such as dropping and accepting packets. To compile this code as a module, choose M here: the module will be called act_gact.
Say Y here to use the generic action randomly or deterministically.
Say Y here to allow packets to be mirrored or redirected to other devices. To compile this code as a module, choose M here: the module will be called act_mirred.
Say Y here to be able to invoke iptables targets after successful classification. To compile this code as a module, choose M here: the module will be called act_ipt.
Say Y here to do stateless NAT on IPv4 packets. You should use netfilter for NAT unless you know what you are doing. To compile this code as a module, choose M here: the module will be called act_nat.
Say Y here if you want to mangle the content of packets. To compile this code as a module, choose M here: the module will be called act_pedit.
Say Y here to add a simple action for demonstration purposes. It is meant as an example and for debugging purposes. It will print a configured policy string followed by the packet count to the console for every packet that passes by. If unsure, say N. To compile this code as a module, choose M here: the module will be called act_simple.
Say Y here to change skb priority or queue_mapping settings. If unsure, say N. To compile this code as a module, choose M here: the module will be called act_skbedit.
Say Y here to update some common checksum after some direct packet alterations. To compile this code as a module, choose M here: the module will be called act_csum.
Say Y here to extend the u32 and fw classifier to support classification based on the incoming device. This option is likely to disappear in favour of the metadata ematch.