4 1 qos overview
DESCRIPTION
QoS OverviewTRANSCRIPT
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Section 4 Introduction to Quality of
Service
Module 1QoS Overview
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7450 ESS Services Implementation
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Module Objectives
Upon successful completion of this module, the student will understand:
What Quality of Service (QoS) means and why it is desirable
Layer 2 and Layer 3 QoS classifiers
QoS implementation on the 7450 ESS including: Traffic Classification
Buffer management
Scheduling
Policing and shaping
Basics of hierarchical QoS
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What is quality of service?
> QoS characteristics:
Uses a combination of hardware and software to provide
consistent delivery of traffic across a network Distinguishes between different types of traffic in order to
allocate resources
QoS gives differential treatment to different types of traffic
Helps to use existing bandwidth more efficiently
Provides a way to deliver Service Level Agreements (SLA)
QoS techniques optimize:
Bandwidth
Delay
Jitter
Packet loss
7450 ESS Quality of Service (QoS)
QoS is an integral part of the 7450 ESS. QoS techniques, applied to both incoming and
outgoing traffic, support multiple customers and multiple services per physical interface. The
7450 ESS has extensive and flexible capabilities for classifying, policing, shaping, and
marking traffic.
QoS techniques classify traffic into forwarding classes, also known as classes of service or
types of service. A forwarding class provides network elements with a method to weigh the
relative importance of one packet over another. Traffic assigned to forwarding classes isplaced into queues and the contents of the queues are output in a controlled manner using
schedulers. The packets forwarding classalong with the in-profile and out-of-profile
statedetermines how the packet is queued and handled as it passes through each 7450 ESS
router.
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Quality of Service on the 7450 ESS
> Service differentiation
Uses differentiated service model (Diff-Serv)
> Aggregation and forwarding classes Large number of individual micro-flows are aggregated into forwarding
classes (8)
Mapping of traffic to forwarding classes (FC) is based on multi-fieldclassification rules
> Resource allocation
IOM resources are allocated on a per-FC basis
Performance of FC flows is provided through shaping, queuing, scheduling,and aggregate bandwidth reservation
> Traffic policing and shaping
Available at service ingress and egress
Policing prevents excessive traffic from congesting the network and assuringthat classified traffic conforms to SLAs
Shaping improves bandwidth utilization minimizes packets loss atdownstream policing points
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QoS Traffic Flow Example
1. Orange and purple traffic enters Node 1 through separate service access points (SAP).
Each SAP classifies its traffic into one or more forwarding classes based on multi-
field classification rules.
Classified packets are placed into queues based on the SAP they entered on and their
forwarding class. Purple traffic is queued separately from orange traffic.
Classification rules and queue parameters are defined in SAP-ingress QoS policies.
2. The forwarding class and profile status (in/out) of the purple and orange traffic is
translated into tunnel header QoS markings (Exp, DSCP, or dot1q bits). Translation is
defined in anetwork QoS policy.
All traffic, purple and orange, belonging to the same FC is queued together at the
network egress of Node 1. The parameters for network queues, which are different
from SAP-ingress queues, are defined by anetwork-queue policy. Queued packets
are serviced by virtual output queue (VoQ) schedulers and sent towards the
appropriate network port.
3. Purple and orange traffic arrives on the same network interface. The traffic is
classified into forwarding classes based on tunnel header markings. The tunnel
header to forwarding class translation is defined in anetwork QoS policy.
All network ingress traffic on an MDA uses a common buffer pool to create the
forwarding class queues. Purple and orange traffic belonging to the same FC is
placed into the same queue. Blue traffic, arriving on a SAP, is queued separately
from the purple and orange traffic.
The queued packets are serviced by a VoQ scheduler and sent towards the switching
fabric.
4. Because purple packets are coming from a network ingress on Node 2, they are
remarked only if the remark flag in the associated network QoS policy is enabled.
The purple packets egress port is different from the orange and blue egress ports, so
they are queued independently according to their FCs.
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QoS Traffic Flow Example
SAP
SAP
SAP
SAP
SAP
SAP
Purple A
Purple B
Orange A
Orange B
Blue A
Blue B
1
1. Traffic is classified into one or more forwarding classes or subclasses and placed into queues. Classification and queue
characteristics are set by SAP-ingress policies.
2. Traffic FC and profile status are mapped to tunnel header QoS markings (EXP, DSCP, or dot1p bits) as defined in a
network QoS policy. All traffic belonging to the same FC is queued together; network queue parameters are defined in a
network-queue QoS policy.
3. Traffic is mapped to FCs based on tunnel header markings; tunnel header to FC mapping is defined in a network QoS
policy.
4. Tunnel headers are remarked only if the remark flag in the associated network QoS policy is enabled.
5. SAP-Egress QoS policies define queuing and packet marking based on the traffic FC.
2
Node 1 Node 2
Node 3
Node 4
3
4
5
ePipe Services
Purple Service
5. A SAP-egress QoS policy defines queuing and packet marking based on FCs. Packets arequeued according to their SAP and forwarding class.
The queued packets are serviced by an egress VoQ scheduler and sent towards an egress port
for delivery to customers.
Traffic arriving at the ingress of Node 3 is processed in the same manner as traffic arriving at
the network ingress of Node 2.
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VersionLength
TOS1 Byte
TotalLength
ID Offset TTL Protocol FCS SA DA Data
Layer 3IPv4
Layer 2 and Layer 3 QoS Classifiers
Preamble SFD DA SA TAG
4 Bytes PT DATA FCS
Layer 2802.1Q/p
IEEE 802.1p
802.1p is a specification for giving Layer 2 switches the ability to prioritize traffic. The prioritization
specification works at the media access control (MAC) framing layer of the OSI model.
IP Precedence
IP Precedence/ToS changes the IP Precedence bits in the Type of Service (ToS) field in the IP
header. Based upon that change, the associated traffic receives priority within the IP network. To
enable this service, all IP routers and switches in the network must be configured to handle traffic
with the IP Precedence bits set.
Differentiated Services Code Point (DSCP)
A modification of the TOS byte. Six bits of this byte are reallocated for use as the DSCP field, where
each DSCP specifies a particular per-hop behavior that is applied to a packet.
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Traffic Classification - Internal Forwarding Classes
BE
L2
AF
L1
H2
EF
H1
NC
FC
Designation
Best Effort
Low-2
Assured
Low-1
High-2
Expedited
High-1
Network
Control
FC Name
0
1
2
3
4
5
6
7
FC ID
Intended for best effort traffic.Best
Effort
Intended for assured traffic.
Intended for assured traffic. Also the default
priority for network management traffic.
Assured
Intended for delay/jitter sensitive traffic.
Intended for network control traffic ordelay/jitter sensitive traffic.
Intended for network control traffic.High
Priority
DefinitionDefault
Class
Type
The 7450 supports eight internal forwarding classes. The default definitions are shown in theabove slide. Users can create QoS policies to configure the ingress marking interpretation and
egress marking behaviour of the forwarding classes.
The forwarding classes are grouped into three class types:
High-Priority
High-priority forwarding classes are serviced before other forwarding classes. These classes are
intended to be used for network control traffic or for delay or jitter-sensitive services (e.g. real
time traffic).
Assured
Assured forwarding classes provide services with a committed rate and a peak rate much like
ATM VBR service categories or Frame Relay. If the core network has sufficient resources in-
profile traffic will reach the service destination. When the network is congested out-of-profile
traffic will be discarded before in-profile traffic.
Best-Effort
The best-effort forwarding classes have no delivery guarantees. All packets in this class are
treated, at best, like out-of-profile assured type forwarding class packets.
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Service Ingress
Service
IngressService
Egress
Network
Ingress
Network
Egress
Service
Access
Point
Service
Access
Point
IP/MPLS
Network
PE PE
SAP SAP
Network QoS Policies
Service QoS Policies
service ingress/egress point can be delimited by a physical port or encapsulation (VLAN, Frame Relay)
SAP-ingress QoS policy:
defines traffic queues (type, en-queuing and de-queuing parameters, mode, etc.)
assigns forwarding classes to queues
maps traffic to a forwarding class or sub-class based on user-defined match criteria and assigns in or out-of-profile status to the packets
is applied to SAPs for IES, ePipe and VPLS services
support for 8 unicast queues, one for each internal forwarding class
VPLS service supports 3 additional queues per forwarding class (broadcast, multicast, and unknown)
support for up to 32 queues per SAP
shared queuing supported for IES and VPLS services
support for hierarchical scheduling (H-QoS)
At service ingress to the 7450 ESS traffic can be classified into one of eight internal forwardingclasses (FC) and mapped to a queue. Traffic classification is achieved with ingress QoS policy
match criteria.
IP and MAC match criteria for service ingress traffic:
IP or application information (L3 L7)
Source IP address/prefix Destination IP address/prefix Source port/range Destination port/range
Protocol type (TCP, UDP, etc.) DSCP value IP fragment
Source MAC, Destination MAC or Layer 2 criteria
IEEE 802.1p value/mask Source MAC address/mask Destination MAC address/mask EtherType type
IEEE 801.2 LLC SSAP value/mask
IEEE 802.2 LLC DSAP value/mask IEEE 802.3 LLC SNAP PID value IEEE 802.3 LLC SNAP OUI zero or non-zero value
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Service Ingress QoS Policy Configuration
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Network Egress
Service
IngressService
Egress
Network
Ingress
Network
Egress
Service
Access
Point
Service
Access
Point
IP/MPLS
Network
PE PE
SAP SAP
Network QoS Policies
Service QoS Policies
each network egress port supports a queue for each of the 8 internal forwarding classes; queues are created
automatically when a port is configured as a network port
queue parameters are defined in a network-queue QoS policy; on network egress the policy is applied to
an entire port
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Network Egress QoS Policy Configuration
config>qos#
net workpolicy-iddescri pt i on description-stringscope {excl usi ve| t empl ate}egress
remarking
fc {be|l2|af|l1|h2|ef|h1|nc}
dscp-in-profile dscp-name
dscp-out-profile dscp-name
lsp-exp-in-profilempls-exp-value
lsp-exp-out-profilempls-exp-value
i ngr essdef aul t - acti on f c {be| l 2| af | l 1| h2| ef | h1| nc} [ prof i l e{i n| out }]dscpdscp-name f c {be| l 2| af | l 1| h2| ef | h1| nc} [ prof i l e{i n| out }]l er - use- dscp
l sp- exp lsp-exp-value f cfc-name [ prof i l e {i n| out }]
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Network Ingress
Service
IngressService
Egress
Network
Ingress
Network
Egress
Service
Access
Point
Service
Access
Point
IP/MPLS
Network
PE PE
SAP SAP
Network QoS Policies
Service QoS Policies
each forwarding class is supported by an ingress queue per MDA
network ingress queues are created automatically when a port is placed in the network mode queue parameters are defined in a network-queue QoS policy; on ingress the policy is applied at the
MDA level to all network ingress ports on the MDA
network-ingress QoS policy defines the mapping of DSCP and EXP bits to one of the 7450 internal
forwarding classes
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Network Ingress QoS Policy Configuration
config>qos#
net workpolicy-iddescri pt i on description-stringscope {excl usi ve| t empl ate}
egr essr emarki ngf c {be| l 2| af | l 1| h2| ef | h1| nc}dscp- i n- prof i l e dscp-namedscp- out - prof i l e dscp-namel sp- exp- i n- prof i l e mpls-exp-valuel sp- exp- out - pr of i l e mpls-exp-value
ingress
default-action fc {be|l2|af|l1|h2|ef|h1|nc} [profile{in|out}]
dscpdscp-name fc {be|l2|af|l1|h2|ef|h1|nc} [profile{in|out}]
ler-use-dscp
lsp-exp lsp-exp-value fcfc-name [profile {in|out}]
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Service Egress
Service
IngressService
Egress
Network
Ingress
Network
Egress
Service
Access
Point
Service
Access
Point
IP/MPLS
Network
PE PE
SAP SAP
Network QoS Policies
Service QoS Policies
SAP-egress QoS policy define:
forwarding class to output queue mapping
in/out-of-profile marking to high/low priority mapping egress queue en-queue and de-queue parameters
support for hierarchical scheduling (H-QoS)
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Service Egress QoS Policy Configuration
conf i g>qossap- egr esspolicy-id
descri pt i on description-stringscope {excl usi ve| t empl at e}f cfc-name
dot 1p dot1p-valuequeue queue-id [ pr i or i t y {l ow| hi gh}]
conf i g>qos# sap- egr ess 100 creat econf i g>qos>sap- egr ess$ descr i pt i on "SAP egr ess pol i cy 100"conf i g>qos>sap- egr ess# queue 2 cr eateconf i g>qos>sap- egr ess>queue$ exi tconf i g>qos>sap- egr ess# f c ef creat e
conf i g>qos>sap- egress>f c# queue 2conf i g>qos>sap- egr ess>f c# exi tconf i g>qos>sap- egr ess# queue 3 expedi t e cr eateconf i g>qos>sap- egr ess>queue$ adapt at i on- r ul e pi r cl osest ci r cl osestconf i g>qos>sap- egr ess>queue# par ent t est 1conf i g>qos>sap- egress>queue# exi tconf i g>qos>sap- egr ess# exi t
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Network-Queue QoS Policy
> Network Queue Policies:
define the network forwarding class queue characteristics
are applied at egress to core network ports and channels are applied at ingress to MDAs
> Network queue policies can be configured to use as many queues as
needed. This means that the number of queues can vary. Not all policies will
use eight queues like the default network queue policy.
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Network-Queue QoS Policy Configuration
conf i g>qosnet work- queuepolicy-name
descri pt i on description-string
f cfc-namemul t i cast - queue queue-idqueue queue-id
queue queue-id [ mul t i poi nt ] [ queue-type]cbspercenthi gh- pr i o- onl ypercentmbspercentratepercentage [ ci rpercentage]
Exampl e:
conf i g>qos# net work- queueNQ1 createconf i g>qos>network- queue# descr i pt i on "Network Queue Policyconf i g>qos>network- queue# f c beconf i g>qos>net work- queue>f c# exi tconf i g>qos>networ k- queue# queue 1conf i g>qos>net work- queue# exi t
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Network-Queue QoS Policy Application
Applying a policy to all network ingress ports on an MDA:
conf i g>car dmdamda-slotnet work
i ngr essqueue- pol i cy name
Applying a policy to a network egress port:
conf i g>por t #ethernet
net workqueue- pol i cy name
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Traffic Service Queues
> Queues created as needed
> Multiple FC per Queue if desired
> Defines packet to FC classification rules
> Per virtual port queuing
Queues are created by applying QoS Service Policies:
All packets received from subscribers must be classified for proper handling within theaggregated service core network. The aggregated packets within the core network are not
treated on a per service basis, but on a forwarding class and profile basis.
7450 ESS routers support eight (8) forwarding classes (FC). Each forwarding class is
important only in relation to the other forwarding classes. A forwarding class provides
network elements with a method to weigh the relative importance of one packet over another
in a different forwarding class.
Queues are created for a specific forwarding class to determine the manner in which the queue
output is scheduled into the switch fabric and the type of parameters the queue accepts. Theforwarding class of packets, along with their in-profile or out-of-profile state, determines how
packets are queued and handled (the per hop behavior (PHB)) at each hop along the path to a
destination egress point.
The forwarding classes are grouped into three categories:
High-priority
Assured
Best effort
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Queue Buffer Management
Each 7450 ESS forwarding complex has 256 Mb of buffer space available for ingress traffic
and 256 Mb for egress traffic queues. Buffer space management ensures that services are
segregated from each other and that no one service will use a disproportionate amount of
system resources.
Reserved Buffers
Reserved buffer space is a percentage of the total buffer space allocated to a queue. You can
configure the amount of reserved buffer space allocated to each queue, the default being fifty
percent of the total buffer space of the queue. The amount of reserved buffer space for a queue
is known as the committed burst size (CBS) of the queue.
Shared Buffers
Shared buffer space is the buffer space that is not reserved for use by specific queues.
Shared Buffers = Total Buffer Pool Reserved Buffers
Any queue can use non-allocated shared buffer space if its reserved buffer space is full and it
has not exceeded its maximum burst size (MBS).
Shared buffer utilization is managed by WRED.
Committed Burst Size (CBS)
The CBS parameter specifies the amount of buffer space reserved for use by a given ingress o
egress queue. Once the reserved buffer space for a queue has been used, the queue contends
with other queues for additional buffer resources up to the Maximum Burst Size (MBS) of the
queue. The CBS for a given queue can be configured or the system can assign a default size.
Maximum Burst Size (MBS)
The Maximum Burst Size parameter specifies the maximum size to which a queue can grow.
This parameter ensures that customers that are exceeding the PIR of a queue will not consume
all the available buffer resources. The MBS for a given queue can be configured or will be
assigned a default value by the system.
Service ingress and egress QoS policies define CBS and MBS for each queue separately, and
the network QoS policy defines CBS and MBS for each network queue.
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Buffer Management Queue Attributes
Queue
Configured as a% of total
buffer space
0xMax
High-Priority-OnlyWater Mark
Highpriorityonly
Shared Buffers
CBS
Reserved buffers are a subset of the buffer pool reservedfor queue allocation.Each queue is allocated a number of reserved buffers.Reserving buffers per queue prevents a queue from beingstarved of buffer resources by other queues.
The Committed Burst Size (CBS) parameter defines theamount of reserved buffer space for a queue.
Shared buffers are buffers within a buffer poolthat are not reserved for specific queues.
The number of shared buffers within a bufferpool is the difference between the total number
of buffers and the reserved buffers.
Any queue within the buffer pool may use anon-allocated shared buffer if its reservedbuffers are full and it has not exceeded itsMaximum Burst Size (MBS).
Sharing buffers within a buffer pool allows the7450 ESS to absorb bursts using the largestpossible pool of buffers while maintainingforwarding class and service separation.
Reservedbuffers
MBS
A portion of the shared buffer space can bereserved for traffic marked as high-priority-only.
After buffer space up to the the high-priority-onlywater mark is used, only high-priority-only trafficwill be allowed into the queue.
Reserved High-Priority-Only Buffers
Reserved High-Priority-Only buffers are defined on service ingress queues and allow buffers to
be reserved for traffic classified as high-priority traffic as defined by the service ingress QoS
policy. When a queue depth reaches a specified level, only traffic marked as high-priority-only
can be placed into the queue.
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Buffer Management - WRED
Shared Buffers Reserved
buffers
LowEnqueuing
Traffic
SLOPE
HighEnqueuing
Traffic
SLOPE
Average Shared Buffer Utilization
Discard
Probability
0
1
Slope Knee
Slope Start
WRED and Shared Buffer Management
Weighted Random Early Detection (WRED) monitors the shared buffer space utilization over a period
of time. WRED uses the shared buffer utilization rather than any individual queue depth to get a better
picture of the average resource utilization of the shared buffer space.
A large amount of buffer space is important to absorb the traffic while the TCP session senders adjust
their round-trip time calculations and throttle their output. The instantaneous value of the weighted
average is used to determine the discard probability of a given packet at the time it arrives at a queue.
The discard probability is a fractional number ranging from zero to one and describes the probability of
discarding a packet subject to a WRED slope. Two points relative to weighted average utilization anddiscard probability define each slope:
The weighted average utilization where discard probability starts to rise above zero
The weighted average utilization and discard probability point defining where discard probabilityrises straight to one.
Two configurable slopes are defined per buffer pool:
a high slope
a low slope
Traffic from expedited (premium) traffic queues is not subject to WRED. Only traffic from non-
expedited traffic queues (assured and best effort) will be affected by the WRED algorithm.
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Buffer Management - WRED Configuration
Average Shared Buffer Utilization
Discard
Probability
0
1
Max-avg
Start-avg
Max-prob
1 2
3
4
1 No Discard
2 Random Discard
3
4All Discard
Once a queue exceeds its reserved buffer allocation and starts using shared buffers, each service packetmapped to that queue is subject to the probability based drop function. The above slide depicts WRED
slope configurable parameters. Each slope is configured with thresholds describing points on the slope
that intersect the average utilization of the shared portion of the buffer pool (X-axis or horizontal plot
with utilization increasing from 0 to 100%) and the probability of discard (Y-axis or vertical plot with
probability rising from 0 to 1).
Configurable parameters are:
Start-avg
Sets the low priority or high priority WRED slope position for the shared buffer average utilization
value where the packet discard probability starts to increase above zero.
Max-avg
Sets the low priority or high priority WRED slope position for the shared buffer average utilization
value where the packet discard probability rises directly to one.
Max-prob
Sets the low priority or high priority WRED slope position for the maximum non-one packet discard
probability value before the packet discard probability rises directly to one.
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Queue Schedulers
All ingress and egress queues operate under the control of one or more schedulers. Several
queues may use the same scheduler.
Schedulers control the data transfer between the following queues and destinations:
Service ingressswitch fabric destinations.
Service egressaccess egress ports.
Network ingressswitch fabric destinations.
Network egressnetwork egress interfaces.
Queue Committed Information Rate (CIR)
The CIR of a queue performs two functions:
1. Profile marking - Service ingress queues mark packets in-profile or out-of-profilebased on the queue's CIR.
2. Scheduler queue priority metric - The scheduler serving a group of ingress oregress queues prioritizes individual queues based on their current CIR and PIR
states. Queues operating below their CIR are always served before queues
operating at or above their CIR.
Queue Peak Information Rate (PIR)
PIR defines the maximum rate at which packets are allowed to exit a queue.
PIR does not specify the maximum rate at which packets may enter a queue; this is governed
by the queue's ability to absorb bursts and is defined by the maximum burst size (MBS).
The PIR is provisioned on ingress and egress service queues, within SAP-ingress and SAP-
egress QoS policies respectively. The PIR of service queues is defined in Kbps (Kilobits/sec).
The PIR for network queues are defined within network-queueQoS policies. The PIR fornetwork queues is defined as a percentage of the network interface bandwidth.
Note:normally it is good practice to make PIR=CIR for high-priority FC queues.
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Scheduling - Queue CIR & PIR
PIR = Peak Information Rate
PIR defines the maximum rate atwhich packets are scheduled out ofa queue.
CIR = Committed Information Rate
CIR defines the threshold up towhich packets scheduled out of thequeue are marked In-profile andconform to CIR. Once the scheduledrate of packets out of the queuepasses the CIR threshold, packetsare marked Out-of-Profile.
ServiceQueue
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Scheduling - Single Tier Hardware Schedulers
Packets are scheduled out of aqueue according to thefollowing criteria:
1. Expedited
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Scheduling - Hierarchical Virtual Schedulers
Strict / WeightedRate Limiting
Scheduler
Strict / WeightedRate Limiting
Scheduler
Strict / WeightedRate Limiting
Scheduler
Strict / WeightedRate Limiting
Scheduler
Strict / Weighted
Rate LimitingScheduler
Queue
Queue
Queue
Queue
Queue
Queue
3 levels supported
Allows lower priority
traffic to make use
of unused bandwidth
when higher priority
traffic is below CIR
Hierarchical Schedulers (H-QoS)
The 7450 ESS makes use of hierarchical virtual schedulers to implement hierarchical QoS (H-QoS).
H-QoS creates a hierarchy of schedulers configured in a series of parent-child relationships.
The levels of scheduler policies are then treated according to their assigned priority. This
design allows the 7450 ESS to implement very granular QoS policies consisting ofcombinations of strict priority queuing and weighted fair queuing for bandwidth management.
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Scheduling - Hierarchical QoS Applications
> Multi-ApplicationSLA
Each application getsreserved bandwidth butlower priorityapplications can burstto use all availablebandwidth.
Sum of CIRs=5Mb/s
Overall PIR=12Mb/s
CIR=0
PIR=max
PIR=max
PIR=3 Mb/s
PIR=2 Mb/s
CIR=2 Mb/s
CIR=3 Mb/s
CIR=0
OverallPIR
12 Mb/s
Voice
Video
Business
Best Effort
> Multi-Site SLA Customer with two
offices connecting tosame VPN, sharingone SLA. Each officehas its own CIR, butcan burst to use anyavailable bandwidth.
VPLSVPLS
12Mb/s
> Multi-ServiceSLA
Customer sharingone SLA betweenInternet accessand VPN services.Internet traffic canburst if VPN isbelow CIR.
VPLSVPLS
12Mb/s
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Overriding QoS policies
> Enhance the capabilities of QoS templates
> Allows an existing QoS policy to be instantiated and thenmodified to suit the new situation
> Allows you to
Re-use a QoS policy (i.e. use it as a template)
Override that template
> Can be used with QoS policies and schedulers
ScenarioAn operator has 3 types of services: HSI, Video and Voice. Each subscriber can buy service
packages with different bandwidth for each service.
HSI: 2, 4, 6 Mbps
Video: 6, 12 Mbps
Voice: 384, 768, 1536 Kbps
With traditional QoS policies, 47 types of policies (variations) are required, or each subscriber
must be configured individually. Overriding allows the use of only 7 templates: HIS only,Video only, Voice only, HSI+Video, HSI+Voice, Video+Voice, HSI+Video+Voice. Eachindividual subscriber can then be assigned bandwidth at the SAP level, by applying and then
overriding one of the 7 templates.
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Overriding QoS policies example
QoS policy
conf i gur e qos sap- i ngr ess 101 createdescr i pt i on Thi s i s t he base queue def i ni t i on for HSI and Vi deodef aul t - f c bedef aul t - pr i or i ty l owqueue 1 cr eate
parent hsiexi tqueue 2 cr eate
parent vi deoexi tf c be c reate
queue 1exi tf c ef cr eat e
queue 2exi tpr ec 4 f c ef pr ec 0 f c be
exi t
Applying and overriding the policy
conf servi ce epi pe 101 cust omer 1create
sap 1/ 2/ 15 creat ei ngr ess qos 101qos- override
queue 1r at e 1024exi tqueue 2
r ate 768exi t
exi texi t
exi t
In this example, sap-ingress policy 101 was created as a template policy.
The policy was then applied to sap 1/2/15 with the override keyword. The changes to thetemplate policy are the rates of queues 1 and 2 (to match for this customer agreed to pay for).
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Questions
1. How many internal forwarding classes does the 7450 ESS support?
a. 2
b. 8c. 16
d. 4
2. What is the default method of scheduling queues in the 7450 ESS?
a. Single tierb. Hierarchical
3. Which of the following groups, A or B describes the default scheduling priority of the7450 ESS:
a. High scheduler queues operating within CIRLow scheduler queues operating within CIR
High scheduler queues operating within PIR
Low scheduler queues operating within PIR
b. High scheduler queues operating above CIR but within PIRLow scheduler queues operating within CIR
High scheduler queues operating above CIR but within PIRLow scheduler queues operating within PIR
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Answers
1. How many internal forwarding classes does the 7450 ESS support?
a. 2
b. 8 c. 16
d. 4
2. What is the default method of scheduling queues in the 7450 ESS?
a. Single tier b. Hierarchical
3. Which of the following groups, A or B describes the default scheduling priority ofthe 7450:
a. High scheduler queues operating within CIR Low scheduler queues operating within CIR
High scheduler queues operating within PIR
Low scheduler queues operating within PIR
b. High scheduler queues operating above CIR but within PIRLow scheduler queues operating within CIR
High scheduler queues operating above CIR but within PIRLow scheduler queues operating within PIR