Alcatel Speed Touch 591s, Техническое руководство пользователя

Страница: 124 / 184

12 — Configuring T1/E1 CE channel groups
12-6 Speed Touch 591s Technical Practices
90-8785-01 February 2001
12.7 Configuring the playout buffer size
The playout buffer compensates for the effects of cell delay variation in cell delivery
and can be configured for each channel group. It absorbs the negative CDV of the
incoming AAL1 cell stream by storing cells and transmitting them when cells arrive
late. This cell store counteracts the increased time between cells arriving at the
interworking function.
The playout buffer also absorbs the positive CDV of the incoming AAL1 cell stream
by storing cells that arrive too soon. This cell store counteracts the decreased time
between cells arriving at the interworking function.
The buffer size is the total size of the buffer. The buffer fills up to the median fill
level before it transmits cells. This means that the median fill level determines the
forwarding delay introduced by the channel group. The median fill level is the
tolerance of the channel group for negative CDV. The difference between the median
fill level and the buffer size is the tolerance of the channel group for positive CDV.
The median fill level on the Speed Touch 591s is set to half the buffer size and cannot
be configured.
The median fill level of the buffer can be configured by configuring the CDV
tolerance; see Alcatel 7350 ASAM Technical Practices for further details.
The size of the playout buffer can be configured from 1.0 to 12 ms in 0.5-ms
increments. The default size is 6.0 ms.
Larger playout buffer sizes introduce larger overall cell transfer delay.
Smaller playout buffer sizes have a limited ability to manage clumping or the effects
of queuing delays in the network. Small playout buffers can lead to a starvation state
that occurs when the buffer has no cells to transmit. This causes CRC errors in the
data transfer.
For more information about the playout buffer, see Alcatel 7350 ASAM Technical
Practices.
Procedure 12-6 Configuring the playout buffer
CONFIG — OBJECT — CHANNELGROUP — <endpoint>
↵
— OPTIONS —
PLAYOUT_BUFF — <value>
↵
where
endpoint is U;group, and group is a channel group identifier—CG1 to CG24 for a T1 port
and CG1 to CG31 for an E1 port
value is 1.0 to 12 ms in increments of 0.5 ms