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This chapter describes the tasks for configuring QoS Generic Traffic Shaping (GTS) 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.
To configure GTS, perform the tasks in the following sections:
The section "GTS Configuration Examples" later in this chapter contains examples of these configuration tasks.
To configure GTS for outbound traffic on an interface or subinterface, use the following command in interface configuration mode:
traffic-shape rate bit-rate [burst-size Configure traffic shaping for outbound traffic on an interface.
Command
Purpose
[excess-burst-size]]
To configure GTS for outbound traffic on an access list, use the following commands beginning in global configuration mode:
access-list access-list-number Assign traffic to an access list interface interface-type interface-number Enter interface configuration mode. traffic-shape group access-list bit-rate Configure traffic shaping for outbound traffic on an interface for the specified access list.
Step
Command
Purpose
1 .
2 .
3 .
[burst-size [excess-burst-size]]
Repeat Steps 1 through 3 for each type of traffic you want to rate limit.
If traffic shaping is performed on a Frame Relay network with the traffic-shape rate command, you can also use the traffic-shape adaptive command to specify the minimum bit rate to which the traffic is shaped.
To configure adaptive GTS for outbound traffic on an interface or subinterface, use the following commands in interface configuration mode:
1 traffic-shape rate bit-rate [burst-size Enable traffic shaping for outbound traffic on an interface. 2 traffic-shape adaptive [bit-rate] Configure minimum bit rate that traffic is shaped to when BECNs are received on an interface. 3 Configure reflection of BECN signals as FECNs.
Step
Command
Purpose
[excess-burst-size]]
With adaptive GTS, the router uses backward explicit congestion notifications (BECNs) to estimate the available bandwidth and adjust the transmission rate accordingly. The actual maximum transmission rate will be between the rate specified in the traffic-shape adaptive command and the rate specified in the traffic-shape rate command.
Configure these commands on both ends of the link, enabling the router at the high-speed end to detect and adapt to congestion even when traffic is flowing primarily in one direction.
To monitor the current traffic shaping configuration and statistics, use any of the following commands in EXEC mode:
show traffic-shape [interface-name] Show the current traffic-shaping configuration. show traffic-shape statistics [interface-name] Show the current traffic-shaping statistics.
Command
Purpose
This section provides the following examples of GTS configurations:
This example shows the configuration of two traffic-shaped interfaces on a router. Ethernet 0 is configured to limit User Datagram Protocol (UDP) traffic to 1 Mbps. Ethernet 1 is configured to limit all output to 5 Mbps.
access-list 101 permit udp any any interface Ethernet0 traffic-shape group 101 1000000 125000 125000 ! interface Ethernet1 traffic-shape rate 5000000 625000 625000
The following is a sample display for the show traffic-shape command for the example shown:
Router# show traffic-shape
access Target Byte Sustain Excess Interval Increment Adapt
I/F list Rate Limit bits/int bits/int (ms) (bytes) Active
Et0 101 1000000 23437 125000 125000 63 7813 -
Et1 5000000 87889 625000 625000 16 9766 -
The following is a sample display for the show traffic-shape statistics command for the example shown:
Router# show traffic-shape statistics
Access Queue Packets Bytes Packets Bytes Shaping
I/F List Depth Delayed Delayed Active
Et0 101 0 2 180 0 0 no
Et1 0 0 0 0 0 no
In this example, a customer may use all of a T1 line for 30 seconds in a burst, but the long-term average is limited to 64 kbps. This configuration restricts the amount of load the system can induce on the outbound network interface.
interface <his interface or sub-interface> traffic-shape rate 64000 8000 46080000
If you need to restrict the amount of load the system can induce both outbound and inbound, and therefore the total load it can induce on the Internet Service Provider (ISP), configure traffic shaping on both the inbound and outbound interfaces, as in the following example:
interface <serial interface or sub-interface> traffic-shape rate 64000 8000 46320000 interface <LAN interface> traffic-shape rate 64000 8000 46320000
Perhaps you need to restrict the flow of NNTP to each of some set of sites across an intervening backbone out an interface to 64 kbps. This example illustrates how to configure that control and provide one site with 256 kbps:
access-list 101 permit <nntp to hither> access-list 102 permit <nntp to thither> access-list 103 permit <nntp to yon> ! interface <the (sub-)interface leading to the above places> traffic-shape group 101 64000 traffic-shape group 102 64000 traffic-shape group 103 256000
Separate token buckets are maintained for each access list, and traffic not matching any access list is not shaped at all.
This example does not restrict flow across a Frame Relay subinterface that has been layered onto a single DLC. However, in the presence of BECN bits from the network, the flow is throttled back to the committed information rate (CIR). The access rate of the interface is assumed to be 1544 kbps, and the CIR is 64 kbps.
interface <relevant sub-interface> traffic-shape rate 1544000 traffic-shape adaptive 64000 traffic-shape fecn-adapt
If the traffic-shape fecn-adapt command is configured at both ends of the link, the far end will reflect received forward explicit congestion notifications (FECNs) as BECNs in a Q.922 TEST RESPONSE messages.
Frame Relay networks are often asymmetrical, that is, the access rate at one site may differ from the access rate at another. In such cases, it may be worthwhile to configure the faster rate to shape to the access rate of the slower, as well as to respond to BECNs. Using the previous example as a starting point, in which the access rate is 1544 kbps and the CIR is 64 kbps, and the access rate at the far end is 128 kbps, the configuration of the subinterfaces would be as follows:
interface <relevant sub-interface>
traffic-shape rate 128000
traffic-shape adaptive 64000
Posted: Thu Jun 3 14:25:08 PDT 1999
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