IBM SC30-3681-08 manual Line Speed, Minimum Information Rate, Maximum Information Rate

Using Frame Relay

The network delivers this excess data with a lower probability of success than

committed burst size data. Set the Be to a value greater than zero only if you are

willing to accept the risk of discarded data and its effect on higher-layer protocol

performance. The Be should equal the value set up with the network provider.

Use the add permanent-virtual-circuit,change permanent-virtual-circuit,add

switched-virtual-circuit or change switched-virtual-circuit commands during

frame-relay con®guration to set the excess burst size. You can also use theset

circuit console command to dynamically change the excess burst size. Orphan

circuits will receive a default excess burst size equal to the value set in the set

CIR-defaultscommand. If you con®gure 0 for CIR, then you must con®gure a

nonzero value for the excess burst (Be) size. You can also set the default excess

burst size for all Frame Relay circuits on this interface using the set CIR-defaults

command.

Line Speed

The line speed is the interface's line speed.

The FR interface's line speed is con®gured using theset line-speedcon®guration

command. The line speed must be con®gured when internal clocking is used.

However, it is recommended that you con®gure a line speed for external clocking

since the router uses the line speed as the maximum information rate when

congestion monitoring is enabled. Also some of the protocols use an interface's

con®gured line speed when calculating a route's cost.

The line speed is not con®gurable on a Frame Relay dial circuit interface. If the dial

circuit is mapped to an ISDN base interface, 64 Kbps is used as the line speed.

For dial circuits using Channelized T1/E1 as the base net, the line speed is 64

Kbps times the number of timeslots assigned or 56 Kbps if you set the bandwidth of

the Channelized circuit to 56 Kbps. For example, if you set the number of timeslots

for a Channelized circuit to 3, the line speed is 192 Kbps (3 * 64 Kbps).

If the dial circuit is mapped to a V.25bis base interface, the line speed of the

V.25bis interface is used for the FR dial circuit.

Minimum Information Rate

The minimum information rate (IR) is the minimum data rate for a VC that the router

throttles down to when it is noti®ed of congestion. You set the minimum IR as a

percentage of CIR using the set ir-adjustmentcon®guration command. It can be

dynamically changed using the set ir-adjustmentconsole command. If you

con®gure CIR equal to 0, the minimum IR is 1500 bps.

Maximum Information Rate

The maximum information rate is the maximum data rate at which the router

transmits for a VC. If the CIR monitoring feature is enabled and CIR and Bc are

nonzero, the maximum information rate is calculated using CIR, Bc, and Be as

follows:

( Bc + Be ) per Tc interval

If the CIR monitoring feature is enabled and CIR and Bc are con®gured equal to 0,

the maximum information rate is equal to the excess burst size (Be) per second.

398MRS V3.2 Software User's Guide