This chapter describes the tasks for configuring QoS weighted fair queueing (WFQ) and Distributed WFQ (DWFQ) on a router. For a complete description of the commands mentioned in this chapter, refer to the Quality of Service Solutions Command Reference; the commands are listed alphabetically within that guide. To locate documentation of specific commands, use the command reference, master index, or search online.
WFQ provides traffic priority management that automatically sorts among individual traffic streams without requiring that you first define access lists. WFQ can also manage duplex data streams such as those between pairs of applications, and simplex data streams such as voice or video. There are two categories of WFQ sessions: high bandwidth and low bandwidth. Low-bandwidth traffic has effective priority over high-bandwidth traffic, and high-bandwidth traffic shares the transmission service proportionally according to assigned weights.
When WFQ is enabled for an interface, new messages for high-bandwidth traffic streams are discarded after the configured or default congestive messages threshold has been met. However, low-bandwidth conversations, which include control message conversations, continue to enqueue data. As a result, the fair queue may occasionally contain more messages than its configured threshold number specifies.
With standard WFQ, packets are classified by flow. Packets with the same source IP address, destination IP address, source Transmission Control Protocol (TCP) or User Datagram Protocol (UDP) port, or destination TCP or UDP port belong to the same flow. WFQ allocates an equal share of the bandwidth to each flow. Flow-based WFQ is also called fair queueing because all flows are equally weighted.
The Cisco IOS software provides two forms of WFQ:
To configure WFQ and DWFQ, perform the tasks in the following sections:
See the section "Fair Queueing Configuration Examples" later in this chapter for examples of how to configure fair queueing in your network.
To configure fair queueing on an interface, use one of the following commands in interface configuration mode after specifying the interface:
Configure an interface to use fair queueing.
Configure an interface to use fair queueing on a Cisco router using a VIP-based interface.
WFQ uses a traffic data stream discrimination registry service to determine to which traffic stream a message belongs. See the table accompanying the description of the fair-queue command in the Quality of Service Solutions Command Reference for the attributes of a message that are used to classify traffic into data streams. Defaults are provided for the congestion threshold after which messages for high-bandwidth conversations are dropped, and for the number of dynamic and reservable queues; however, you can fine-tune your network operation by changing these defaults.
For DWFQ, packets are classified by flow. Packets with the same source IP address, destination IP address, source TCP or UDP port, destination TCP or UDP port, protocol, and type of service (ToS) field belong to the same flow.
To monitor fair queueing services in your network, use the following commands in EXEC mode:
show interfaces [interface] fair-queue
Show information about an interface configured for WFQ and DWFQ.
Show status of the fair queueing configuration.
This section provides the following examples of QoS fair queueing configurations:
The following example requests a fair queue with a congestive discard threshold of 64 messages, 512 ---dynamic queues, and 18 RSVP queues:
interface Serial 3/0 ip unnumbered Ethernet 0/0 fair-queue 64 512 18
The following example enables DWFQ on the HSSI 0/0/0 interface:
interface Hssi0/0/0 description 45Mbps to R2 ip address 126.96.36.199 255.255.255.252 fair-queue
The following is sample output from the show interfaces fair-queue command for this configuration:
Router# show interfaces hssi 0/0/0 fair-queue Hssi0/0/0 queue size 0 packets output 35, drops 0 WFQ: global queue limit 401, local queue limit 200