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Configuring an ADSL WAN Interface Card on Cisco 1700 Series Routers
OL-3317-03
Configuring Quality of Service Parameters
Multilink PPP over ATM with Link Fragmentation and Interleaving
This feature allows multilink PPP (MLPPP) encapsulation over a single slow link to fragment and
interleave packets to a small enough size that the delay requirements of delay-sensitive traffic will be
met.
Fragment size at the MLPPP bundle can be configured by using the virtual-template interface
bandwidth command and the ppp multilink fragment-delay command. The ideal fragment size for
MLPPP over ATM should allow the fragments to fit into an exact multiple of ATM cells. These
commands calculate fragment size using the following formula:
fragment size = bandwidth x fragment-delay / 8.
For example, if the MLPPP ATM header is 10 bytes and the AAL5 packet overhead is 8 bytes, the
fragment size for MLPPP over ATM can be calculated as follows:
fragment size = 48 x # of cells - 10 - 8.
In this case, 2 cells per fragment are desirable, so the fragment size is calculated at 78 bytes.
The total bandwidth usable on this interface is 75 percent of the value declared in the bandwidth
command. To change this default value, enter the max-reserved-bandwidth command.
LLQ must be enabled when you configure MLPPP with link fragmentation and interleaving.
Note The Cisco 1700 series routers only support PPP encapsulation for MLPPP with link fragmentation
and interleaving. The dialer interface is not supported.
MLPPP + LFI Configuration
The following example shows a Cisco 1751 router configuration with MLPPP + LFI:
hostname zorro
username ruby-1 password 7 36497A4872384A
!
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
priority 64
set ip precedence 6
!
interface ATM0/0
dsl operating-mode auto
no ip address
no atm ilmi-keepalive
!
int atm0/0.1 point-to-point
pvc 0/33
vbr-rt 160 160 1
tx-ring-limit 3
protocol ppp Virtual-Template1
!
interface Loopback1
ip address 10.0.0.10 255.255.255.255
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