Table of Contents
Advertisement
8 — Configuring the V.35/X.21 CE user port
Table 8-2 lists the circuit parameters that can be configured on the Speed Touch 591s
user port.
Parameter
AAL service type
Playout buffer size
User data octets per cell
Pad octet pattern
Service types
The V.35/X.21 circuit emulation version of the Speed Touch 591s supports two data
transfer modes—unstructured data transfer mode and basic structured data transfer
mode (AAL1).
Procedure 8-8 Configuring the AAL service type
CONFIG — OBJECT — PORT — <U>
Playout buffer size
The playout buffer for data flowing from the network port to the user port can be
configured to compensate for the effects of positive and negative cell delay variation.
Cell delay variation is a measurement of the difference in cell propagation delay
occurring on a connection. The playout buffer depth is set to absorb the negative
CDV characteristics of the network (the increased time between the arrival of
consecutive cells, or cell spacing) by ensuring that the buffer has sufficient data so
that the data stream does not run dry between cell arrivals.
Conversely, the playout buffer must also absorb the positive CDV characteristics of
the Speed Touch 591s and network (cells being received with a very short delay
between them, or cell clumping) by providing sufficient cell storage space in the
buffer to avoid overflow under clumping conditions. Buffered data is sent on the
V.35 serial stream at a constant rate, which is independent of the rate at which the
cells are received.
The setting for CDVT determines how much CDV can be tolerated before the Speed
Touch 591s is forced to insert erroneous (fixed-pattern) data. A high CDVT setting
allows the AAL1 VC to tolerate a higher CDV without errors, but at the expense of
a higher transfer delay through the Speed Touch 591s. The CDVT cannot be
configured and is set by default to half the playout buffer size.
8-6
Table 8-2 Circuit parameters
Options
UDT, SDT_w/BASIC
1 to 12 ms, in increments of 0.5 ms
3 to 46, ALL
00 to FF
— CIRCUIT — AAL_SERVICE — UDT or SDT_BASIC
Speed Touch 591s Technical Practices
Default value
UDT
6 ms
ALL
FF
90-8785-01
February 2001
Advertisement
Table of Contents
