Tài liệu IP over ATM doc

10
IP over ATM
Overview
This module focuses on IP QoS mechanisms that can be used on ATM interfaces.
It includes the following topics:
n Introduction to IP over ATM
n Per-VC WRED
n VC Bundling
n Per-VC CB-WFQ
n RSVP to SVC Mapping
Objectives
Upon completion of this module, you will be able to perform the following tasks:
n List the requirements of IP QoS in combination with ATM QoS
n Describe the hardware and software requirements for advanced IP QoS
mechanisms on ATM interfaces
n Describe per-VC queuing
n Describe and configure per-VC WRED
n Describe and configure VC bundling
n Describe and configure per-VC CB-WFQ
n Describe RSVP to SVC mapping
n Monitor and troubleshoot IP QoS on ATM interfaces
10-2 IP QoS IP over ATM Copyright  2001, Cisco Systems, Inc.
Introduction to IP over ATM
Objectives
Upon completion of this lesson, you will be able to perform the following tasks:
n Describe the QoS-related problems when using ATM networks
n Describe the hardware and software requirements for advanced IP QoS
mechanisms on ATM interfaces
n Describe per-VC queuing
Copyright  2001, Cisco Systems, Inc. IP QoS IP over ATM 10-3
© 2001, Cisco Systems, Inc. IP QoS IP over ATM-5

IP vs. ATM
Technology comparison
IP vs. ATM
Technology comparison
IP
• Connectionless
• Per-packet QoS (IP
precedence)
• Small number of service
classes
• IP precedence or DSCP
does not encode
service parameters
ATM
• Connection oriented
• Per-connection (virtual
circuit) QoS
• Large number of QoS
traffic classes (CBR,
VBR, UBR, ABR)
• Rich traffic parameters
(PCR, MCR, SCR )
specified for each VC

The Internet Protocol (IP) is a routed protocol that is used to transmit data in
packets. It uses the best-effort delivery for individual packets without any flow
control. Transmission Control Protocol (TCP) is used with IP to provide a
connection-oriented service.
Asynchronous Transfer Mode (ATM), on the other hand, provides connections
between endpoints in the ATM network. The connections are called virtual circuits

(VCs).
IP’s default best effort service can be supplemented by differentiated quality of
service based on IP precedence or DSCP marking. A QoS solution using IP
precedence is limited to 8 classes, 2 of which are reserved and 1 should be used
for the default best-effort class. A QoS solution using DSCP scales up to 64
classes.
ATM provides a wider range of services:
n Constant Bit Rate (CBR) is useful for delay-sensitive applications such as
voice. This service provides bandwidth and delay guarantees.
n Variable Bit Rate—Real Time (VBR-RT) is useful for burstier delay-sensitive
applications. This service provides bandwidth and delay guarantees.
n Variable Bit Rate—Non Real Time (VBR-NRT) is useful for bursty traffic.
This service provides bandwidth guarantees.
n Available Bit Rate (ABR) is useful for best-effort traffic that is allowed more
bandwidth, when available or configured. This service provides bandwidth
guarantees and access to extra bandwidth.
n Unspecified Bit Rate is useful for the real best effort where there are no
guarantees.
10-4 IP QoS IP over ATM Copyright  2001, Cisco Systems, Inc.
IP’s IP precedence or DSCP are only used to mark packets. They do not include
any service parameters. Service parameters depend on the QoS mechanism being
deployed.
ATM’s services also include various per-connection service parameters, such as:
n Sustained Cell Rate (SCR) for CBR, VBR and ABR services
n Minimum Cell Rate (MIR) for ABR
n Peak Cell Rate (PCR) for VBR, ABR and UBR services
n Maximum Burst Size (MBS)
Both IP and ATM can implement Quality of Service (QoS). The decision on which
technology to use for quality of service should be based on a number of factors,
such as:

n Availability of ATM
n Interaction between ATM and IP
n Scalability options of the technology
n Performance limitations
This module introduces the possibilities of combining IP QoS with ATM.

Copyright  2001, Cisco Systems, Inc. IP QoS IP over ATM 10-5
© 2001, Cisco Systems, Inc. IP QoS IP over ATM-6
Integrating IP and ATM
Integrating IP and ATM
• Overlay model (ATM forum)
– ATM VC’s are manually established between pairs
of devices
– IP packets are sent across these VC’s
– ATM switches are not IP aware
• Peer model (MPLS)
– ATM switches are IP aware on control (but not
data) plane
– ATM VC’s are established on-demand based on IP
routing tables

There are two main approaches to integration of IP with/over ATM:
n The traditional way (overlay model) is to use individual permanent virtual
circuits (PVC) to establish point-to-point adjacencies between IP routers. IP
routing protocols are used to provide reachability across a network of ATM
connections. ATM has no knowledge of IP and cannot use IP information to
optimize its links.
n The newer approach (MPLS) is to make ATM switches IP aware. ATM
switches run an IP routing protocol to establish virtual circuits.
This module focuses on the QoS available with traditional permanent and switched

virtual circuits (PVCs and SVCs).
The IP QoS- IP over MPLS module discusses QoS possibilities when using the
peer model.

10-6 IP QoS IP over ATM Copyright  2001, Cisco Systems, Inc.
© 2001, Cisco Systems, Inc. IP QoS IP over ATM-7
IP QoS and ATM
IP QoS and ATM
• Routers can be interconnected over an ATM
backbone using different ATM services:
– UBR – congestion management is virtually
impossible because routers are allowed to
transmit packets at line speed
– VBR – congestion management is easier, but it
requires conservative setting of transmit rates
– CBR – similar to VBR from IP perspective
– ABR – pushes congestion back to the source,
requires dynamic adjustment to available
bandwidth

Achieving good quality of service for IP classes greatly depends on the type of
ATM network and services used.
n Using UBR, prevents routers from detecting congestion in the network. It is
therefore difficult to manage congestion based on IP precedence or DSCP.
The reason for this is because all packet drops happen on the congested link
somewhere in the ATM network.
n VBR makes it easier to push congestion back to the source where it can be
managed by routers.
n CBR is typically used for non-bursty delay sensitive traffic. It is therefore
more important to prevent congestion by correctly provisioning the class that is

using CBR.
n ABR is a good solution where bandwidth can be utilized to the maximum
without having many drops in the ATM network.

Copyright  2001, Cisco Systems, Inc. IP QoS IP over ATM 10-7
© 2001, Cisco Systems, Inc. IP QoS IP over ATM-8
UBR Virtual Circuits
UBR Virtual Circuits
• Solution:
– Set CLP on the router based on IP information to minimize the
effect of cell drops
No congestion
Router allowed to
send at full speed
Congestion
Random
CLP marking
Unintelligent drops
based on CLP

A solution using UBR can be improved in terms of IP QoS, by marking less
important packets with the CLP bit for congestion control. In case of congestion,
the ATM switches will drop the less important packets to give more bandwidth for
the higher-priority packets.
The ATM FORUM also calls the UBR service category a “best effort” service,
which requires neither tightly constrained delay nor delay variation. In fact, UBR
provides no specific quality of service or guarantee throughput whatsoever. This
traffic is therefore “at risk” since the network provides no performance guarantees
for UBR traffic. The Internet and Local Area Networks are examples of this type
of “best effort” delivery performance. Examples of this are LAN emulation

(LANE), IP over ATM, and non-mission-critical traffic.
This solution is fairly limited, since it allows for only two classes on the IP layer
where congestion should be managed.

10-8 IP QoS IP over ATM Copyright  2001, Cisco Systems, Inc.
© 2001, Cisco Systems, Inc. IP QoS IP over ATM-9
VBR Virtual Circuits
VBR Virtual Circuits
• Solution:
– Set CLP on the router based on IP information
– Use available IP QoS mechanisms to manage congestion at the
source
Router is sending
at configured rate
Congestion is
possible
Unintelligent random
drops
Congestion!

A solution using VBR is better at providing feedback to routers sending cells into
the ATM network. Congestion will occur on a router’s virtual circuit, where it can
be managed by using the QoS mechanisms available in the Cisco IOS software.
CLP marking can be used for less-important packets or for those packets above
the Sustained Cell Rate (SCR) to improve the chances for higher-priority packets
when congestion occurs in the ATM network.
The rt-VBR service category supports time-sensitive applications, which also
requires constrained delay and delay variation requirements, but which transmit at
a time varying rate constrained to a PCR, SCR, and MBS define a traffic contract
in terms of the worst-case source traffic pattern for which the network guarantees

a specified QOS. Examples of such bursty, delay-variation-sensitive sources are
voice and variable-bit-rate video.
The nrt-VBR service category supports applications that have no constraints on
delay and delay variations, but which still have variable-rate, bursty traffic
characteristics. This class of application expects a low Cell Loss Ratio (CLR).
The traffic contract is the same as that for rt-VBR. Applications include packet
data transfers, terminal sessions, and file transfers. Networks may statistically
multiplex these VBR sources effectively.
Copyright  2001, Cisco Systems, Inc. IP QoS IP over ATM 10-9
© 2001, Cisco Systems, Inc. IP QoS IP over ATM-10
CBR and ABR Virtual Circuits
CBR and ABR Virtual Circuits
• Solution:
– Use available IP QoS mechanism to handle congestion at the
source
Router is sending
at configured rate.
Congestion!

CBR virtual circuits, are used for delay-sensitive traffic. This traffic should not
experience congestion due to keeping the quality of data being transmitted. If
congestion occurs, it can be managed by the IP layer using the IP QoS
mechanisms on the router’s ATM interface.
The CBR service category supports real-time applications requiring a fixed
amount of capacity defined by the PCR. CBR supports tightly constrained
variations in delay. Example applications are voice, constant-bit-rate video, and
Circuit Emulation Services (CES). Normally, networks must allocate the peak rate
to these types of source.
The ABR service category works in cooperation with sources that can change
their transmission rate in response to rate-based network feedback used in the

context of closed-loop flow control. The aim of ABR service is to dynamically
provide access to capacity currently not in use by other service categories to users
who can adjust their transmission rate in response to feedback. In exchange for
this cooperation by the user, the network provides a service with very low loss.
Applications specify a maximum transmit-rate (PCR_ and the minimum required
rate, called the Minimum Cell Rate (MCR). ABR service does not provide
bounded delay variation; hence real-time applications are for ABR are LAN
interconnection, high-performance file transfers, database archival, non-time-
sensitive traffic, and web browsing.
10-10 IP QoS IP over ATM Copyright  2001, Cisco Systems, Inc.
© 2001, Cisco Systems, Inc. IP QoS IP over ATM-11
Congestion Management in ATM
Networks
Congestion Management in ATM
Networks
• Congestion management on routers should
be performed on a per-VC basis
• Design options:
– Make sure there is no congestion in the ATM
network (ABR, CBR, VBR) and use IP QoS
mechanisms at the source (CB-WFQ, WRED)
– Mark less important packets with the CLP bit in
case there is congestion in the ATM network (CB-
Policing, CB-Marking)
– Use multiple parallel (per-CoS) virtual circuits with
ATM QoS (VC Bundling)

This module discusses three different approaches to designing QoS in IP networks
on ATM:
1. Using IP QoS mechanisms to ensure there is no congestion in the AMT

network
2. Using ATM QoS mechanisms with IP precedence used for classification (VC
Bundling)
3. Combining both IP and ATM QoS mechanisms

Copyright  2001, Cisco Systems, Inc. IP QoS IP over ATM 10-11
© 2001, Cisco Systems, Inc. IP QoS IP over ATM-12
Per-VC Queuing
Per-VC Queuing
• Per-VC queuing is required in order to handle congestion on per-VC
basis
• Per-VC queuing prevents head-of-line blocking by slow virtual circuits
ATM Port Adapter
VC 1/50
VC 1/64
VC 1/76
VC 1/39
ATM interface
Cell queue VC 1/50
Cell queue VC 1/64
Cell queue VC 1/76
Cell queue VC 1/39
VIP Memory
Frame queue VC 1/50
Frame queue VC 1/64
Frame queue VC 1/76
Frame queue VC 1/39
ATM
hardware
shaping

Per-VC queuing with per-VC
congestion management

One of the most important parts of implementing QoS is to make ATM virtual
circuits appear as physical interfaces on routers; that is, each VC must have its
own queue (per-VC queuing). Per-VC queuing prevents one congested VC from
slowing down other VCs (head-of-line blocking).
Per-VC queuing can then be supplemented by various IP QoS mechanisms, such
as:
n WRED
n CAR
n CB-WFQ
n CB-LLQ
n CB-Policing
n CB-Shaping
n CB-Marking
CB-Marking and CB-Policing can also be used to set the CLP bit.

10-12 IP QoS IP over ATM Copyright  2001, Cisco Systems, Inc.
Summary
The following steps have to be taken prior to the designing of a QoS solution for IP
over ATM:
n Implement Per-VC queuing (to prevent head-of-line blocking and allow for IP
QoS mechanisms to be implemented on individual virtual circuits)
n Decide on the technology that will be used to implement QoS
Review Questions
Answer the following questions:
1. What are the main differences between IP and ATM?
2. Which QoS services does ATM support?
3. How should congestion be handled when an ATM backbone is used?

4. Why is per-VC queuing so important?
Copyright  2001, Cisco Systems, Inc. IP QoS IP over ATM 10-13
Per-VC WRED
Objectives
Upon completion of this lesson, you will be able to perform the following tasks:
n Describe per-VC WRED
n Configure per-VC WRED
n Monitor and troubleshoot per-VC WRED
10-14 IP QoS IP over ATM Copyright  2001, Cisco Systems, Inc.
© 2001, Cisco Systems, Inc. IP QoS IP over ATM-17
Per-VC WRED
Per-VC WRED
• Single ATM VC is established over an ATM
cloud between a pair of routers
– ABR, VBR, UBR or CBR
– Using UBR will not result in proper operation, as
there is no ATM shaping in UBR
• All IP traffic toward a next-hop router is
forwarded across a single ATM VC
• Congestion is managed entirely on the IP
layer using WRED on each individual ATM
VC, resulting in differentiated IP services

A simple addition to best-effort service on ATM interfaces is Weighted Random
Early Detection (WRED). WRED is most efficient when the majority of the traffic
is TCP (TCP reacts to random drops and slows down the transmission rate). With
other protocols, packet sources may not respond or may resend dropped packets at
the same rate. Thus, dropping packets does not decrease congestion. WRED
treats non-IP traffic as precedence 0, the lowest precedence. Therefore, non-IP
traffic is more likely to be dropped than IP traffic

UBR would probably result in congestion somewhere in the ATM network, thus
preventing any intelligent congestion management on the IP layer.
Any other ATM service (CBR, VBR or ABR) will push congestion back to the
source where WRED can be used to drop packets based on the IP precedence or
DSCP value.

Copyright  2001, Cisco Systems, Inc. IP QoS IP over ATM 10-15
© 2001, Cisco Systems, Inc. IP QoS IP over ATM-18
Per-VC WRED : Intelligent
IP Packet Discard
Per-VC WRED : Intelligent
IP Packet Discard
VIP2-50 PA-A3-XX
Per
Per
-
-
VC
VC
WRED:WRED:
Intelligent Discard
Intelligent Discard
Threshold Exceeded
VC1
VC2
VC3
No discard
No discard
on PAon PA
Traffic Traffic

ShapingShaping
Per
Per
-
-
VC
VC
QueuesQueues

Per-VC queuing requires an Enhanced ATM Port Adapter that support up to 4096
cell queues. Each virtual circuit is assigned a queue and the ATM scheduler
forwards cells according to the ATM service and shaping parameters.
The router (or VIP on Cisco 7x00 series routers) also assigns one queue per virtual
circuit.
Cell departure is shaped if ABR, VBR or CBR services are used, thus causing
congestion in the frame queue if packet arrival is greater than the shaping rate in
ATM. Per-VC WRED can be used to manage congestion within individual queues
(classes).


10-16 IP QoS IP over ATM Copyright  2001, Cisco Systems, Inc.
© 2001, Cisco Systems, Inc. IP QoS IP over ATM-19
Configuring Per-VC WRED
Configuring Per-VC WRED
• The following configuration steps are needed
to enable per-VC WRED:
– Create a Random-Detect-Group template with a
WRED profile
– Apply the WRED template to an ATM interface or
to individual ATM VCs

– Verify and monitor the operation of per-VC WRED

Applying WRED to individual VCs is slightly different than applying WRED to
interfaces. A Random Detect Group must be created if non-default WRED
profiles need to be used on VCs. Standard WRED parameters (per-precedence
minimum threshold, maximum threshold and maximum drop probability) are set in
the random-detect-group configuration mode.

Copyright  2001, Cisco Systems, Inc. IP QoS IP over ATM 10-17
© 2001, Cisco Systems, Inc. IP QoS IP over ATM-20
random-detect-group name
random-detect-group name
Router(config)#
• Creates a WRED template
Create and configure RED-group
Create and configure RED-group
exponential-weighting-constant exp
exponential-weighting-constant exp
Router(cfg-red-group)#
• Defines WRED weighting constant
• Default: 9
precedence IP-prec min-threshold max-threshold prob-denominator
precedence IP-prec min-threshold max-threshold prob-denominator
Router(cfg-red-group)#
• Defines RED profile for specified precedence
• Default: as with per-interface WRED

The random-detect-group global configuration command creates a WRED
profile and enters the red-group configuration mode. WRED per-precedence
profiles are configured in the red-group configuration mode, using similar

commands as with per-interface WRED, except the commands are not preceded
by the random-detect keyword.
Any class (IP precedence) can be configured with a RED profile different from
the default by using the precedence command in the red-group configuration
mode:
n Minimum threshold—When the average queue depth is above the minimum
threshold, RED starts dropping packets. The rate of packet drop increases
linearly as the average queue size increases, until the average queue size
reaches the maximum threshold.
n Maximum threshold—When the average queue size is above the maximum
threshold, all packets are dropped. If the difference between the maximum
threshold and the minimum threshold is too small, many packets might be
dropped at once, resulting in global synchronization.
n Mark probability denominator—This is the fraction of packets dropped
when the average queue depth is at the maximum threshold. For example, if
the denominator is 512, one out of every 512 packets is dropped when the
average queue is at the maximum threshold.
WRED does not calculate the drop probability using the current queue length, but
instead uses the average queue length. The average queue length is constantly
recalculated, using two terms:
n The previously calculated average queue size
n The current queue size
10-18 IP QoS IP over ATM Copyright  2001, Cisco Systems, Inc.
An exponential weighting constant N influences the calculation by weighing the
two terms. It therefore influences how the average queue size follows the current
queue size, in the following way:
n A low value of N makes the current queue size more significant in the new
average size calculation, therefore allowing larger bursts
n A high value of N makes the previous average queue size more significant in
the new average size calculation, so that bursts influence the new value to a

smaller degree
The default value is 9 and should suffice for most scenarios, except perhaps those
involving extremely high-speed interfaces (such as OC12), where it can be
increased slightly (to about 12) to allow more bursts.
Note The default WRED parameter values are based on the best available data.
Cisco recommends that you do not change the parameters from their default
values unless you have determined that your applications will benefit from the
changed values.

Copyright  2001, Cisco Systems, Inc. IP QoS IP over ATM 10-19
© 2001, Cisco Systems, Inc. IP QoS IP over ATM-21
Apply WRED group to
an ATM PVC
Apply WRED group to
an ATM PVC
random-detect [attach random-detect-group]
random-detect [attach random-detect-group]
Router(config-if-atm-vc)#
• Enables WRED on a PVC using the selected WRED
profile
• Default WRED parameters are used if the group
name is omitted or refers to non-existent group
• Default: no WRED is used on the ATM PVC

The last step in the configuration of per-VC WRED is to attach a random-detect-
group to a virtual circuit. The random-detect command is used in the VC
configuration mode to enable WRED. If no random-detect-group is specified
WRED will use the default WRED profiles.

10-20 IP QoS IP over ATM Copyright  2001, Cisco Systems, Inc.

© 2001, Cisco Systems, Inc. IP QoS IP over ATM-22
show queueing random-detect [interface intf [vc vpi vci ]]
show queueing random-detect [interface intf [vc vpi vci ]]
Router#
• Displays WRED parameters for an ATM
(sub)interface or for individual VC
Monitoring and Troubleshooting
Per-VC WRED
Monitoring and Troubleshooting
Per-VC WRED
show queueing interface interface [vc vpi vci]
show queueing interface interface [vc vpi vci]
Router#
• Displays interface queues or individual per-VC
queue

The show queuing random-detect command display WRED parameters and
statistics for a specific interface or virtual circuit. There is only a single queue into
which packets from all IP precedences are placed after dropping has taken place.
The show queuing interface command displays per-VC queue parameters and
statistics. The “Queuing strategy” reported by the command lists “random early
detection (RED)” as the queuing mechanism. The default minimum thresholds are
spaced evenly between half and the entire maximum threshold. Thresholds are
specified in terms of packet count.
Copyright  2001, Cisco Systems, Inc. IP QoS IP over ATM 10-21
© 2001, Cisco Systems, Inc. IP QoS IP over ATM-23
WRED Case Study
WRED Case Study
• WRED is applied to a ATM PVCs in a network with
the following IP precedence definitions

IP prec. Meaning
0 High-loss best-effort traffic
1 Low-loss best-effort traffic
2 Premium traffic outside of the contract
3 Premium traffic in the contract
4 Unused
5 Voice-over-IP
6 Routing protocol traffic
7 Routing protocol traffic
• WRED queue length is 100 packets for PVCs with
SCR > 10 Mbps and 40 packets for slower PVCs

The case study shows a QoS design where packets are classified into three user
classes:
n Best-effort class
n Premium class
n Voice class
The Best-effort and Premium classes use two IP precedence values to mark
high-drop (out-of-contract) traffic and low-drop (within contract) traffic.
IP precedence values 6 and 7 are reserved for control messages (for example,
routing protocols) and should not be used for user traffic.
The design lists these two additional requirements:
n Virtual circuits faster than 10Mbps should have queues that can hold up to 100
packets
n Slower virtual circuits can store up to 40 packets in the queue
All virtual circuits should manage congestion by using WRED.


10-22 IP QoS IP over ATM Copyright  2001, Cisco Systems, Inc.
© 2001, Cisco Systems, Inc. IP QoS IP over ATM-24

Case Study WRED Profile
Case Study WRED Profile
Packet Discard
Probability
Average
Queue Size
0.1
RSVP
15
10
20
25
30
35
37
Precedence 2
Precedence 0
Precedence 3
Precedence 1
VoIP
Routing

The figure illustrates the WRED parameters that should be implemented for fast
and slow virtual circuits. The minimum and maximum thresholds should reflect a
different maximum queue size for fast VCs (100 instead of 40).
High drop Best-effort and Premium packets start being dropped when the average
queue size reaches 10 or 15 respectively (25 or 37 on fast VCs). If the queue still
grows the low-drop Best-effort packets start being dropped when the queue size
reaches 20 (50 on fast VCs). High drop packets, of course, are more aggressively
dropped than low-drop packets.

Control packets, VoIP packets and packets of RSVP flows are only dropped in
extreme situations when the average queue size is close to the maximum (40 for
slow VCs and 100 for fast VCs).
Copyright  2001, Cisco Systems, Inc. IP QoS IP over ATM 10-23
© 2001, Cisco Systems, Inc. IP QoS IP over ATM-25
Router Configuration
Router Configuration
• Step #1 - configure WRED profile for slow
PVCs
random-detect-group slow-wred-profile
precedence 0 10 25 10
precedence 1 20 40 10
precedence 2 15 25 10
precedence 3 25 40 10
precedence 4 1 10 10
precedence 5 35 40 10
precedence 6 30 40 10
precedence 7 30 40 10
random-detect-group slow-wred-profile
precedence 0 10 25 10
precedence 1 20 40 10
precedence 2 15 25 10
precedence 3 25 40 10
precedence 4 1 10 10
precedence 5 35 40 10
precedence 6 30 40 10
precedence 7 30 40 10

The figure shows the configuration of WRED profiles used for slow VCs.

10-24 IP QoS IP over ATM Copyright  2001, Cisco Systems, Inc.
© 2001, Cisco Systems, Inc. IP QoS IP over ATM-26
Router Configuration
Router Configuration
• Step #2 - configure WRED profile for fast
PVCs
random-detect-group fast-wred-profile
precedence 0 25 62 10
precedence 1 50 100 10
precedence 2 37 62 10
precedence 3 62 100 10
precedence 5 87 100 10
precedence 4 1 10 10
precedence 6 75 100 10
precedence 7 75 100 10
random-detect-group fast-wred-profile
precedence 0 25 62 10
precedence 1 50 100 10
precedence 2 37 62 10
precedence 3 62 100 10
precedence 5 87 100 10
precedence 4 1 10 10
precedence 6 75 100 10
precedence 7 75 100 10

The figure shows the configuration of WRED profiles used for fast VCs.
Note This configuration simply uses scaled thresholds to support up to 100 packets
in the queue.

Copyright  2001, Cisco Systems, Inc. IP QoS IP over ATM 10-25

© 2001, Cisco Systems, Inc. IP QoS IP over ATM-27
Router Configuration
Router Configuration
• Step #3 - Apply WRED profile on various
PVCs
interface ATM11/0/0
ip address 17.1.0.1 255.255.255.0
atm pvc 50 0 50 aal5snap 25000 50000 10 inarp
random-detect fast-wred-profile
!
interface ATM11/0/0.100 point-to-point
ip address 17.1.1.1 255.255.255.252
atm pvc 100 0 100 aal5snap 17000 34000 10 inarp
random-detect fast-wred-profile
!
interface ATM11/0/0.101 point-to-point
ip address 17.1.1.5 255.255.255.252
atm pvc 101 5 101 aal5snap 2000 4000 10 inarp
random-detect slow-wred-profile
interface ATM11/0/0
ip address 17.1.0.1 255.255.255.0
atm pvc 50 0 50 aal5snap 25000 50000 10 inarp
random-detect fast-wred-profile
!
interface ATM11/0/0.100 point-to-point
ip address 17.1.1.1 255.255.255.252
atm pvc 100 0 100 aal5snap 17000 34000 10 inarp
random-detect fast-wred-profile
!
interface ATM11/0/0.101 point-to-point

ip address 17.1.1.5 255.255.255.252
atm pvc 101 5 101 aal5snap 2000 4000 10 inarp
random-detect slow-wred-profile

The figure shows the configuration of three virtual circuits. Two are using the
WRED profile for fast VCs and the third is using the WRED profile for slow VCs.