interface Virtual-Template1
bandwidth 320
ip unnumbered Loopback1
ip tcp header-compression iphc-format
service-policy output ADSL-2
ip rtp header-compression iphc-format
Tunable Transmission Ring
The transmission (tx) ring is the first-in, first-out (FIFO) buffer used to hold frames before transmission
at the DSL driver level. The tx ring defines the maximum number of packets that can wait for
transmission at Layer 2.
The tx ring complements the ability of LLQ to minimize jitter and latency of voice packets. For
maximum voice quality, a low tx ring setting should be used. For maximum data throughput, a high tx
ring setting should be used.
You can configure the size of the tx ring for each PVC. The default value is 60. However, the value of
the setting can be from 2 through 60.
A low tx ring setting, such as 3, is required for latency-critical traffic.
Note
For example, when the tx ring limit is configured as 3 and LLQ is configured on the PVC, the worst case
delay for a voice packet is the time required to transmit three data packets. When the buffering is reduced
by configuring the tx ring limit, the delay experienced by voice packets is reduced by a combination of
the tx ring and LLQ mechanism.
The size of the tx ring buffer is measured in packets, not particles.
Note
Configuration Example
The following example is a configuration of the tx ring limit on an ATM PVC interface. To enable the
tx ring limit, enter the tx-ring-limit command.
class-map match-all VOIP
match ip dscp 32
class-map CRITICAL
match access-group 100
!
policy-map 1751_ADSL
class CRITICAL
priority 48
class VOIP
bandwidth 64
set ip precedence 6
!
interface Loopback1
ip address 10.0.0.10 255.255.255.252
!
interface ATM0/0
dsl operating-mode auto
no ip address
no atm ilmi-keepalive
!
interface ATM0/0.1
OL-3317-03
Configuring an ADSL WAN Interface Card on Cisco 1700 Series Routers
Configuring Quality of Service Parameters
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