Implementing Cisco QoS in AVVID Networks

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Implementing Cisco QoS in AVVID Networks
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Cisco QoS accelerates the deployment of
intelligent network services by enabling
predictable response for application traffic
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Trend Integrated MultiserviceNetwork Data,
Voice, Video

• Integration of data, voice, and video services
  into a single packet-based infrastructure using
  IP
• Both in enterprise and public service provider
  network infrastructures

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AVVID Network Capacity Planning
Voice is not Free - Especially on low speed
links - Engineer the network for Voice, Video
Data
Link Capacity (Min BW for Voice Min BW for
Video Min BW for Data) / 0.75
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Topics

• QoS Overview
• QoS Architecture
• Classification and Marking
• Congestion Management
• Congestion Avoidance
• Shaping and Policing
• Call Admission Control

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QoS What Is It?

• Provides predictable response times
• Manages delay and jitter-sensitive applications
• Controls loss during bursty congestion
• Sets traffic priorities across the network
• Supports dedicated bandwidth per application
• Avoids and manages network congestion

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Why Invest in QoS?
To guarantee network resources to meet bandwidth,
loss, latency, and jitter requirements of various
traffic classes based on application needs
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QoS Why Is It Needed?Motivation for QoS Is
Manifold

• Integrated networks carry different traffic types
  from a variety of business-enabling applications
• Business drivers and policies dictate
  preferential treatment for some type of traffic
  over others
• Convergence of voice and data networks force us
  to consider servicing two different types of
  traffic on a single wire

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Different QoS Requirements
Traffic is Grouped into Classes that Have Similar
QoS Requirements
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QoS Where Is It Needed?
Central Campus
Remote Branch
WAN
QoSCampus Access
QoSCampus Distrib.
QoSWAN
QoSBranch

• Speed and duplex settings
• Classification/trust on IP Phone and access
  switch
• Multiple queues on IP Phone and access ports

• Classification and trust boundaries on IP Phone ,
  access layer switch and router
• Multiple queues on IP Phone and all access ports

• Layer 3 policing
• Multiple queues on all ports priority queuing
  for VoIP
• WRED within data queue for congestion management

• Low-latency queuing
• Link fragmentation and interleave
• Bandwidth provisioning
• Admission control

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Layer 2 QoS Integration Concerns
Areas where QoS Maybe a concern
Use DSCP Upstream
171.68.192.100
10.0.1.100
IP Phone Voice CoS 5 IP Prec 5 DSCP
EF PC Reclassify CoS 0
1/ Access Layer (L2) 1/ CoS uses as entrance
Criteria to PQ. 2/ Where support exists Map
CoS to DSCP Map VLAN to DSCP
2/ Distribution layer 1/ Map CoS to DSCP Map
VLAN to DSCP 2/ Map IP Addr to DSCP 3/ MAP L4
to DSCP
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QoS Service Types
Certain Applications Require Specific Network
Resources
Integrated Services
Guaranteed
Some Traffic Is More Important Than the Rest
Differentiated
Differentiated Services
Differentiated Services
Best Effort
Some Traffic Is More Important Than the Rest
Best Effort (IP,IPX,AppleTalk)
Ubiquitous Connectivity
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Integrated Services

• Multiple-service module
• Requests specific kind of service from the
  network before sending data
• Uses RSVP
• Intelligent queuing mechanisms

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Differentiated Services (DiffServ)

• Network defined service
• Multiple service module to satisfy differing
  requirements
• Implemented through a 6 bit DSCP Field

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DiffServ Components

• Packet classification and marking
• Congestion management
• Congestion avoidance
• Traffic conditioning

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3 Steps for CoS/QoS Implementation

• ClassificationMarking the packet with a specific
  priority denoting a requirement for special
  service from the network
• SchedulingAssigning packets to one of multiple
  queues (based on classification) for expedited
  treatment through the network
• ProvisioningAccurately calculating the required
  bandwidth for all applications plus element
  overhead

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Evolution of QoS Features
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Topics

• QoS Overview
• QoS Architecture
• Classification and Marking
• Congestion Management
• Congestion Avoidance
• Shaping and Policing
• Call Admission Control

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QoS Architecture
Classification and Marking
Link-Efficiency Management
Policing and Shaping
Congestion Control
Identify and Split Traffic into Different Classes
and Mark according to policies
Discard Misbehaving Traffic to Maintain Network
Integrity and Control Bursts and Conform Traffic
Prioritize, Protect, Discard and Isolate Traffic
Based on Markings
Fragment and compress for WAN efficiency
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Typical Enterprise Network
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Topics

• QoS Overview
• QoS Architecture
• Classification and Marking
• Congestion Management
• Congestion Avoidance
• Shaping and Policing
• Call Admission Control

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Access Layer Traffic Conditioning
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Traffic Classification

• Classify as far out towards the edge as possible
• Classify locally generated voice packets using
  dial-peer
• If LAN switch can set CoS bits in 802.1p/q
  header, use these to classify on router
• Any classification technique can be usedACL,
  input interface, Network-Based Application
  Recognition (NBAR), CAR, etc.

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Classify at Layer 3 or Layer 2
Standard IPV4 Three MSB Called IP
Precedence (DiffServ May Use Six D.S. Bits Plus
Two for Flow Control)
Layer 3IPV4
Version Length
Len
ID
Offset
TTL
Proto
FCS
IP-SA
IP-DA
Data
ToS1 Byte
Three Bits Used for CoS (Class of Service)
Layer 2ISL
FCS 4 Bytes
ISL Header26 Bytes
Encapsulated Frame 124.5 KBytes
Three Bits Used for CoS (User Priority)
Layer 2802.1Q/p
TAG4 Bytes
FCS
DATA
PT
SA
DA
SFD
PREAM.
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Classification and Marking Tools
TOOLS
Modular QoS Command Line Interface
(MQC) Policy-Based Routing (PBR) Access Control
List (ACL)/Routemap Dial Peers Committed Access
Rate (CAR)
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Modular QoS CLI (MQC)
Big term, simple meaning a command line
interface (CLI) for configuring complex QoS
policies in a simplified way

• A new command syntax for configuring QoS policy
• Reduces configuration steps and time
• Configure policy, not raw per-interface
  commands
• Uniform CLI across all main Cisco IOS-based
  platforms
• Separates classification engine from the policy

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Basic MQC Commands
Which traffic do we care about?
What will do with this traffic?
Where will we implement this policy?
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MQC Classification Example
Which traffic do we care about?
The default is match-all
What will do with this traffic?
Where will we implement this policy?
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Layer 2 Classification (Cisco Switch)

• Set CoS values according to Policy
• Set CoS value manually for packets from PC
• Trust CoS values from computer

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Layer 3 Classification (ACL-based)
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Network Based Application Recognition (NBAR)
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NBAR Capabilities

• A new IP packet classifier capable of
  classifying
• L4-L7 protocols which dynamically assign
• TCP/UDP ports
• Sub-port criteria such as transaction types
• NBAR classification used by QoS features in CEF
  mode
• More than 24 concurrent URLs, hosts, or MIME type
  matches
• Matching beyond the first 400 bytes in a URL

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Configuration Classification (NBAR)
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Access Layer Traffic Conditioning
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MarkingWhat Is It?
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Class-Based Marking

• Formerly QoS Packet Marking
• Set CoS, IP Precedence, DSCP value, ATM CLP
• Introduced as QoS Packet Marking - 12.0(5)XE
• Matching based on IP Precedence, DSCP, QoS
  groups
• Updated - 12.1T
• Set ATM cell loss Priority (CLP)
• Introduced as Class-Based Marking - 12.1(2)T
• Support added for 2600, 3640, 4500
• Updated - 12.1(5)T
• Match CoS, Set CoS (to prioritize Layer 2,
  remap Layer 2 to Layer 3

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Class-Based Marking Example
Router(config) policy-map Video
Router(config-pmap) class Markit
Router(config-pmap) set ip precedence 5
Router(config) interface fastethernet 0/1
Router(config) service-policy input Video
Other set commands
set ip dscp ip-dscp-value
set ip qos-group qos-group-value
set cos cos-value
set atm-clp
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Map Layer 2 to Layer 3 Example
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Policy-Based Routing
With PBR
ROUTE MAPS
PERMIT/DENY access by

• Select special route for specified traffic
• Set IP Precedence
• Classify traffic based on access control list

PACKET SIZE and/or
SRC. AND DEST. ADDRESS
At RECEIVING INTERFACE
WHY USE PBR?

• If size or addresses do not match, set
• IP address
• next hop
• output interface

• set special route
• provide equal access
• protocol-sensitive routing
• source-sensitive routing
• control interactive vs. batch traffic
• dedicated links

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PBR ExampleMarking IP Precedence
1. Define route map
2. Specify match criteria packet length, IP
Precedence
3. Specify action set IP Prec, next hop, output
interface
1. Define route map
5. Specify route map to use
4. Specify interface
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Precedence Marking Using CAR
R1
R2
S0
in bits per second (bps)
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Topics

• QoS Overview
• QoS Architecture
• Classification and Marking
• Congestion Management
• Congestion Avoidance
• Shaping and Policing
• Call Admission Control

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Access Layer Handling Congestion
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Congestion Management

• Determines how to place traffic into queues, and
  then how to service them
• Queuing Techniques
• FIFOfirst-in, first-out
• PQpriority queuing
• CQcustom queuing
• WFQflow-based weighted fair queuing
• CBWFQclass-based WFQ
• IP RTP Priorityalso known as PQ/WFQ
• LLQlow latency queuing

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Priority Queuing (PQ)

• Rigid traffic prioritization scheme with 4
  queueshigh, medium, normal, low
• Unclassified packets to the normal queue
• Can result in protocol starvation (lower
  priority traffic might never be serviced)

Transmit Queue
Output Line
High
Medium
Classify
Normal
Low
Classify by protocol, source interface
Interface Buffer Resources
Absolute Priority Scheduling
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Custom Queuing (CQ)

• Flexible traffic prioritization scheme allocates
  minimum bandwidth to specific classes of traffic
• Up to 16 queues available
• Queues serviced in round-robin fashion
• Bandwidth specified in byte count and queue length

1
Transmit Queue
Output Line
2
3
Classify
4
5
Weighted Round-Robin Scheduling (byte count)



Up to 16
Classify by protocol, source interface
Interface Buffer Resources
Allocate Proportion of Link Bandwidth
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Router
VoIP (High)
1
1
V
V
Video (High)
PQ
2
2
4
3
2
1
1
2
WAN Circuit
Data (Low)
WFQ
3
3
3
3
WFQ Is Weighted Fair Hence is not the
Recommended Queuing Structure for Voice
Data (Low)
4
4
4
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QoS Queuing Features IP RTP Priority CBWFQ with
LLQ IP to ATM QoS
Classification Mechanisms IP Precedence DiffServ
Code Point RSVP
Identifying Voice as Important
Giving Priority to Voice
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LLQ Protecting Voice From Data
Layer 3 Queuing Subsystem
Layer 2 Queuing Subsystem
Link Fragmentation Interleave
Low Latency Queuing
PQ - Voice
Police
PQ - Video
Interleave
Class X
Packets Out
Packets In
CBWFQ
Fragment
Class Y
Default
WFQ
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LLQ Configuration Voice, Video, Data
access-list 101 permit ip any any precedence
5 access-list 102 permit ip any any precedence
4 access-list 103 permit udp host 1.1.1.1
host 1.1.1.2 range 16384 20000 ! class-map
voice1 match access-group 101 class-map
Video1 match access-group 102 class-map data
match access-group 103 ! policy-map
wantraffic class voice1 priority 48
class video1 priority 384 class data
bandwidth 16 random-detect class
class-default fair-queue 64 queue-limit
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Leased Lines 12.0.7T
interface Multilink 1 service-policy output
wantraffic
ATM 12.0.7T
interface ATM1/0.1 point-to-point
service-policy output wantraffic
VoIPovFR targetted for 12.1.2T
PQ traffic
map-class frame voipovfr frame cir 128000
frame bc 640 frame frag 160 service-policy
output wantraffic
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WFQ and IP RTP PRIORITY Using Multilink PPP
R1
R2
S0
Create multilink group 1 and configure a strict
priority queue
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WFQ and IP RTP PRIORITY Using Multilink PPP
R1
R2
S0
Configure interface S0 to be part of the
multilink bundle 1
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Frame Relay and IP RTP Priority
Frame Relay
R1
R2
S0
Frame Relay map class config with strict priority
service
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Frame Relay and IP RTP Priority
Frame Relay
R1
R2
S0
Apply map class to PVC 100 to provide strict
priority
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Queuing Comparison
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Topics

• QoS Overview
• QoS Architecture
• Classification and Marking
• Congestion Management
• Congestion Avoidance
• Shaping and Policing
• Call Admission Control

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Congestion Avoidance

• If a queue fills up, all packets at tail end of
  queue get droppedcalled tail-drop
• Tail-drop causes TCP window to shrink on a large
  number of sessions, giving the effect of global
  synchronization
• Need a way to make an intelligent drop decision
  when average queue depth exceeds a minimum
  threshold

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Link Underutilization Global Synchronization
(4) Result is queue (and link) underutilization
Tail Drop
Queue Utilization
100
(4)
(4)
(4)
(4)
Time
(1)
(2)
(3)
(1)
(2)
(3)
(1)
(2)
(1) Multiple senders slow transmission
(2) Multiple senders restart with slow-start
method
(3) Result is global synchronization
(transmission waves)
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Weighted Random Early Detection (WRED)
Drop Probability
1
1/m
0
Min 1
Min 2
Min 3
Max 1
Max 2
Max 3
Max Queue Length (Tail Drop)
Average Queue Depth
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Flow-Based WRED (FRED)

• Extension of WRED
• - Classifies packets by flow (for example,
  source address, destination address, port)
• - Tracks flow of each packet in output queue
• Penalizes flows that do not respond to drops
  (e.g. UDP)
• No single flow hogs all the buffer resources
• Adaptive flows get fair share of resources

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Configure WREDInterface-Level Example
Enable WRED with default values, then change the
weight values
precedence
minimum threshold
mark probability denominator
maximum threshold
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CBWFQ Using WRED Packet Drop Example
R1
R2
S0
E0/1
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Recap of Packet-Dropping Techniques
Evolution
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Topics

• QoS Overview
• QoS Architecture
• Classification and Marking
• Congestion Management
• Congestion Avoidance
• Shaping and Policing
• Call Admission Control

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Access Layer Traffic Conditioning
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Shaping
Shaping is the QoS feature that regulates traffic
flow to an average or peak bit rate

• With bursting capability
• With bufferspackets that cannot be sent are
  queued (delayed)

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Policing
Policing is the QoS component that limits traffic
flow to a configured bit rate

• With limited bursting capability
• But no bufferspackets above the specified burst
  rate are dropped or have their precedence altered

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Policing Shaping Differences
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Policing Committed Access Rate (CAR)

• Propagates bursts
• No smoothing or shaping of traffic
• No buffering
• - No delay component added
• Optimized to run on high-speed links
• Rate limits may be implemented on input or output
  interfaces, or subinterfaces
• Includes Frame Relay and ATM subinterfaces

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CAR Policing Actions
Transmit
Evaluate Packet Against Policy
Drop
Next Policy
None Remaining
Set Precedence
Color/Recolor
Send Packet
CAR provides rate limiting and does not guarantee
bandwidth. Should be used with other QoS
features for bandwidth assurances
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Class-Based Policing

• Provides rate limiting per class
• Policer within each class can have different
  CIR/burst limits and different actions defined if
  traffic conforms or exceeds the rate limits
• Packets that cannot be transmitted can simply be
  marked down or dropped within a class

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Policy Map Policing
police ltbpsgt ltburst-normalgt ltburst-maxgt conform-a
ction ltactiongt exceed-action ltactiongt violate-ac
tion ltactiongt Actions include - drop -
set-clp-transmit - set-dscp-transmit (0-63)
- set-prec-transmit (0-7) -
set-qos-transmit (0-99) - transmit Similar to
CAR, but with a violate action added
class-map data-in match input interface
e0/0 ! policy-map rate-limit class data-in
police 8100 2000 2504 conform-action
transmit exceed-action set-dscp-transmit
0 violate-action drop ! interface s0/1
service-policy out rate-limit
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Class-Based Policer with CBWFQ
policy-map POLICE class bronze bandwidth
percent 15 police 300000 1500 3000
conform-action transmit exceed-action set-dscp-tr
ansmit 1 violate-action drop class silver
bandwidth percent 35 police 600000 1500 3000
conform-action trasmit exceed-action set-dscp-tra
nsmit 2 violate-action drop ! interface
serial4/1 ip address 4.4.4.1 255.255.255.0
service-policy output POLICE clockrate 1544000
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Topics

• QoS Overview
• QoS Architecture
• Classification and Marking
• Congestion Management
• Congestion Avoidance
• Shaping and Policing
• Call Admission Control

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Definition ofCall Admission Control
Call Admission Control (CAC) is a deterministic
decision before call establishment, on whether
the required network resources are available to
provide QoS to the new call
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Call Admission Control
Example WAN Bandwidth Can Only Support 2
Calls What Happens when 3rd Call Attempted?
Call 3 Causes Poor Quality for ALL Calls
Call 1
PBX
PBX
x1111
x1111
Call 2
VoIP Data Network
x1112
x1112
Call 3
x1113
x1113
IP RTP Priority does no admission control All
calls proceed and use priority queue All 3 calls
experience jitter ? delay/loss ? poor quality
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Multiple Ways to Achieve Local CAC Operations

• Physical DS0 Limitation
• Max Connections
• Voice Bandwidth for FR
• Trunk Conditioning
• Local Voice Busyout (LVBO)

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Call Admission ControlBy Design Port Density
Example WAN Bandwidth Can Only Support 2
Calls Provision only enough ports for two calls
? Ensure IP RTP Priority is configured
accordingly
Call 1
PBX
PBX
x1111
x1111
Call 2
VoIP Data Network
x1112
x1112
x1113
x1113
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Call Admission Controlmax-connections
Example Specify Max Connections to a specified
peer Local Accounting for Admission
Control Ensure IP RTP Priority is configured
accordingly
Call 1
PBX
PBX
x1111
x1111
Call 2
VoIP Data Network
x1112
x1112
x1113
x1113
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Call Admission ControlGatekeepers
Example Zone bandwidth used for Admission
Control. Ensure IP RTP Priority is configured
accordingly.
Gatekeeper
Call 1
PBX
PBX
x1111
x1111
Call 2
VoIP Data Network
x1112
x1112
x1113
x1113
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Gatekeeper Zone BW

• Works well where calls between sites must be
  limited
• Limits the aggregate BW used for voice and video
• The only CAC method available for Distributed CM
  topologies
• Key part of H.323 video network designs
• All IOS GW calls are 64K from the GKs
  perspective regardless of codec selected
• GK does not do BW reservation, only limits calls

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Summary

• The tools needed to deploy QoS end-to-end are
  available today
• The trick is to understand application
  requirements and the QoS behavior expected
• Applying the right tools in the right place help
  make the DiffServ model scale
• Several QoS management tools are available for
  provisioning and monitoring

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