Alcatel Speed Touch 591s, Техническое руководство пользователя, Страница: 62 / 184

5 — Configuring frame relay port parameters
5-10 Speed Touch 591s Technical Practices
90-8785-01 February 2001
QoS thresholds
The quality-of-service thresholds can be set for the four frame relay queues; refer to
Alcatel 7350 ASAM Technical Practices for further information on frame relay QoS.
Procedure 5-12 Configuring QoS thresholds
1 Enter:
CONFIG — OBJECT — PORT — <U>
↵
— STREAM — OPTIONS — THRESHOLDS
2 Select:
REAL_TIME or LOW_DELAY or COM_THRUPUT or BEST_EFFORT
3 Select:
ACT or SCT or MCT
4 Enter the desired value for the threshold:
<value>
↵
where value is the queue threshold in ms (see Table 5-3 for values)
Pacing
The Speed Touch 591s uses pacing to control the rate at which frame relay and frame
forwarding traffic travels from the user port to the network port. Pacing smooths out
traffic peaks so that the data is transmitted more evenly, thus avoiding peaks at the
receiving end, usually a central node. Since the central node receives data
simultaneously from several different sources, bursts of data can cause congestion on
the node. Use of the pacing feature prevents this problem.
The SHDSL line on the Speed Touch 591s network port runs at a much faster rate
than the user port. Without pacing, frames arriving on the user port would be
converted to ATM cells and sent out at the SHDSL line rate on the network port,
producing bursts of data at the receiving end. Pacing allows the data frames to be
more evenly spread in cells on the SHDSL line, with empty cells inserted between
data cells. This helps with traffic management on the receiving end because the node
can discard the empty cells, giving it more time to process the data cells.
Default pacing values are calculated and applied by the Speed Touch 591s as a
function of the user port clock rate (see section 5.1 for details) and the SHDSL line
rate. The device on the other end of the SHDSL line dictates the line rate across the
SHDSL line because the Speed Touch 591s acts as a slave device.