Traffic-Shaping Concepts

Shapers monitor rate data sent
If rate exceeded, delays packets in shaping queue
Packets then released over time
Solves issue of SP dropping traffic (shape before it reaches them)
Solves egress blocking (choke point in the network)

Shaping Terminology

Routers only send at clock rate
Lower rates alternate between sending and silence
For IOS Shaping, static time interval set (Tc)
Number of bits per Tc interval calc'd to match shaping rate
Bits per Tc = Bc (committed burst)
Tc = Bc/CIR, measure in Ms
Bc = Committed burst in bits
Shapred rate - Bps
Be - Excess burst, number of bits above Bc sent after period of inactivity

Shaping with excessive burst

More than Bc bits in one or more ints if link has been quiet

Underlying Shaping Mechanics

Tc = Bc/shape rate

Token bucket model
Bucket filled at start of Tc
Each token is for 1 bit
At start of Tc, shaping can release Bc bits

Actions in shaping bucket

Refill at Tc start
Spend tokens for packet forwarding
Overflow - Only sents amount in interval
Be exists to use overflow
Bc tokens added at each Tc still
If more tokens available than Bc, can send more at next Tc

Generic Traffic Shaping

GTS in older IOS
Supported on most router ints
Not used with flow switching
Could shape all traffic leaving, or ACL'd for subset
traffic-shape rate shaped-rate [Bc] [Be] [buffer-limit]
Shaped rate - bps
Bc and Be - bits
Buffer is maximum queue buffer in bps
Only shaped rate required, Bc and Be would then be quarter of shaped by default
traffic-shape group access-list-number shaped-rate {BC} {BE}
show traffic-shape INTERFACE
show traffic-shape STATISTICS
show traffic-shape QUEUE

Class-Based Shaping

Allows queueing tools for packets delayed by shaping
Classification of packets for different shape rates
Command in policy map is shape [average | peak] mean-rate [[burst-size][excess-burst-size]]
Apply with service policy as normal
Tc cannot be set directly
Bc and Be dont need setting
Calcaultes values of abvoe based on

Variable	Rate le 320kbps	Rate gt 320kbps
Bc	8000 bits	Bc = shape rate by Tc
Be	Be=Bc=8000 bits	Be=Bc
Tc	Tc=Bc/shape rate	25ms

Tuning for Voice

Use small Tc so packets less delayed

policy-map queue-voip 
 class voip-packets
  priority 32
 class class-default
  fair-queue

policy-map shape-all
 class class-default
  shape average 96000 960
  service-policy queue-voip

Shaping only when single packet above contract

Configuring Shaping by Bandwidth percent

Can be done as perents

Keep in mind following: -

Shape percent ses bw of int or subint on which enabled
Sub ints dont inherit physical bandwidth, 1544 default
Bc and Be configured as Ms (bits sent at configured rate in time period)
Tc set to configure Bc (in ms)
shape average 50 125 ms
50 is shaper rate, 125 ms is Bc
Ms required or command rejected

CB Shaping at Peak Rate

shape peak MEAN-RATE
Calcs Bc, Be and Tc same way as average
Refills Bc + Be for time intervals
Logic means CB shaping can send Bc and Be per time period
Shaping rate becomes
configured_rate x (1 + Be/Bc)
64 (1 + 8000/8000) = 128

Adaptive Shaping

shape adaptive MIN-RATE under shape command in class config

Policing Concepts and Config

Different internal process than older IOS policer

CB Policing Concepts

Enabled on ingress or egress
Monitors bit rate of combined packets
When above, takes action
Actions are
Drop
set-dscp-transmit
set-prec-transmit
set-qos-transmit
set-clp-transmit
transmit
Packets conform, exceed or violate

Single Rate, Two Colour (One Bucket)

No excess burst
Conform and exceed only
Single token bucket
Over time, policer refils bucket according to policing rate
Token is a byte, so for 96 kbps over a second, bucket filled with 12,000 tokens (12KBps)
Not refilled on time interval
Instead, reacts to arrival of packet, replenishes prorate number of tokens into bucket
Defined by: -
((Current_packet_arrival_time - Previous_packet_arrival_time) x Police_rate) / 8
Policer then decides if newly arrived packets conform or exceeding contract
Number of bytes (Xp)
Number of tokens in bucket (Xb)

Category	Requirements	Tokens drained from bucket
Conform	If Xp <= Xb	Xp tokens
Exceed	If Xp>Xb	None

Over time, tokens back into packet, so some packets conform
After bit rate lowers, all conform

Single-Rate, Three Colour (Two Buckets)

First bucket filled like single
If Bc bucket overlows, these fill Be
After filling buckets, another option
If Xbe>=Xp>Xbc, tokens from Be bucket

Two-Rate, Three Colour Policer

Second rate is PIR (Peak Information Rate)
Packets under CIR conform
Packets below PIR exceed
Beyond is violating
Sustained excess buristing allowed in this model
Be bucket not relying on spillage
If one bucket was 128kbps, other 256kbps, in 0.1s 1600 tokens into BC, 3200 into Be

Consumed like so: -

Category	Requirements	Tokens Drained from Bucket
Conform	Xp <= Xbc	Xp tokens from Bc and Xp from Be
Exceed	Xbc < Xp <= Xbe	Xp tokens from Be
Violate	Xp > Xbc and Xp > Xbe	None

CB Policing Config

police bps burst-normal burst-max conform-action action exceed-action action [violate-action action

Single Rate Three Colour

policy-map police-all
 class class-default
  police cir 96000 bc 12000 be 6000 conform-action transmit exceed-action set-dscp-transmit 0 violate-action drop

Policing subset

class-map match-all match-web
 match protocol http

policy-map police-web
 class match-web
  police cir 80000 bc 10000 bc 5000 conform-action transmit exceed-action transmit violate-drop
 class class-default
  police cir 16000 bc 2000 be 1000 conform-action transmit exceed-action set-dscp-transmit 0 violate-action set-dscp-transmit 0

CB Policing defaults for Bc and Be

If Bc not config'd, equivalent in bytes for 1/4 send at police rate
Bc = ((CIR * 0.25s)/8 bits = CIR/32

Default Be based on policy: -

Type of config	Defaults
Single rate, two colour	Bc = CIR/32, Be = 0
Single rate, three colour	Bc = CIR/32, Be = Bc
Dual Rate three colour	Bc=Cir/32, Be = PIR/32

Config for Dual Rate

police {cir CIR} [bc CONFORM-BURST] {pir PIR} [be PEAK-BURST] [conform-action ACTION exceed-action ACTION [violate-action ACTION]]
Requires PIR and CIR to be confirmed, can set with only these two

Multi action policing

Mark multiple fields in same packet
Slightly different syntax, places in policing subconfig mode

policy-map testpol1
 class class-default
  police 128000 256000
   conform-actionb transmit
   exceed-action transmit
   violate-action set-dscp-transmit
   violate-action set-frde-transmit

Policing by percentage

Bc and Be config'd as number of Ms
IOS calcs Bc and Be based on how many bits sent in that many ms

Dual rate example:-

policy-map test-pol6
 class class-default
  police cir percent 25 bc 500 ms pir percent 50 be 500 ms conform transmit exceed transmit violate drop

Committed Access Rate

Single rate two colour
Set rate in bps, Bc and Be bytes
CAR differs from CB policing
Uses rate-limit command
Cascaded/nested rate limits (multiple on interface)
Does support Be, but no violate categeory
When Be config'd, internal logic for monitoring differs from CB
rate-limit {input | output| [access-group [rate-limit] acl-index] bps burst-normal burst-max conform-action action exceed-action action
Can use normal ACL or rate limit ACL, which can match MPLS EXP, IPP or MAC. For other fields, ACL

int Se0/0
 rate-limit input 496000 62000 62000 conform-action continue exceed-action drop
 rate-limit input access-group 101 400000 50000 50000 conform-action transmit exceed-action drop
 rate-limit input access-group 102 160000 20000 20000 conform-action transmit exceed-action drop
 rate-limit input access-group 101 200000 25000 25000 conform-action transmit exceed-action drop

Continue means go through and potentially match others

Hierarchical Queuing Framework

MQC mechanism used for HQC for queueing and shaping
Local engine to support QoS features
Tree structure built using policy maps
When data through interface using HQF, data classified so it traveres tree branches
Data arrives at top of tree, classified on one of leaves

policy-map class
 class c1
  bandwidth 14
 class c2
  bandwidth 18

policy-map map1
 class class-default
  shape average 64000
  service-policy class

policy-map map2
 class class-default
  shape average 96000

map-class frame-relay fr1
 service-policy output map1

map-class frame fr2
 service-policy output map2

int Se4/1
 encapsulation frame-relay
 frame-relay interface-dlci 16
  class fr1
 frame-relay interface-dlci 17
  class fr2

Fast deployment of QoS queueing and shaping
Consisitent queueing behaviour with common MQC
HQF supports distributed and non-distributed implementations
Includes levels of scheduling and support for integrated CB shaping and queueing
Placement of hierarchical policies and queueing features at every level of structure
means can apply queueing to any traffic class in parent or child level of policy
discrete service levels for different sessions/subscribers

policy-map class
 class c1
  bandwidth 14
 class c2
  bandwidth 18

policy-map map1
 policy-map child
  class child-c1
   bandwidth 400
  class child-c2
   bandwidth 400

policy-map parent
 class parent-c1
  bandwidth 1000
  service-policy child
 class parent-c2
  bandwidth
  service-policy child

Flow-based Fair Queueing in Class-Default

Rather than WFQ, flow based used
Flow queues scheduled equally instead of weight based (ipp or dscp)

Default Queueing Implementation for Class-Default

Default FIFO when no policy-map
Can use bandwidth, fair queue or service policy to change

Class-Default and Bandwidth

Bandwidth assigned is unused int bandwidth not in other user-defined classes
Minimum 1% of int by default

Default Queuing for Shape Class

Default FIFO rather than WFQ for Shape Class

Policy Map and Int Bandwidth

Can reserve 100% of int bandwidth
If no explciti bandwidth guarantee in class-default, can assign max of 99% of int bandwidth
Error appears when going to 12.4(20)T if 100% to user classes

Per-Flow Queue Limit in Fair Queue

When fair queue enabled, default per flow queue limit is 1/4 of class queue limit
If not enabled in class, default is 16 packets

Oversubscription Support for Multiple Policies on logical interfaces

When shaping policy added to multiple logical ints (including sub int), and sum of all above physical in tbandwidth
Congestion at physical gives back pressure to each logical int policy
Each policy reduces output rate to its fair share of int bandwidth

Shaping on GRE Tunnel

In HQF, shapping after Encap with hierarchical service policy
When shape in parent policy applied to tunnel, can use class-default only
Cannot configure user defined class in parent
Can apply service policy with queueing at tunnel/virtual int and service policy with queueing at physical, but not at same time

Nested Policy and Reference Bandwidth for Child Policy

When nested policy config'd with child queueing policy under parent
Ref bw for child taken from following
Minimum (parent shaper rate, parent class's implicit/explicit bandwidth guarantee)
when not defined for parent, int bandwidth devices among all parents as implicit bandwidth guarantee

Handling congestion on int with policy map

If int configurured with policy map full of heavy traffic,
Implicitly defined polcier allows traffic as defined in bandwidth statement at each class
Policer activated whenevr traffic congestion on interface

QoS Troubleshooting and COmmands

Lack of planning for qos requirements
Failure to track changes in apps and traffic
Lack of good documentation

Troubleshooting Slow App Response

Ensure enough bandwidth for application
Check bw, latency and drop requirements
IP SLA can help, show ip sla statistics
show policy-map
show class-map
show policy-map interface

Troubleshooting Voice and Video

show mls qos
show policy-map
show class-map
show policy-map interface
IP SLA

Switch techniques

show mls qos input-queue ingress
show mls qos INTERFACE queuing egress
show mls qos maps cos-input-q - mapping for CoS to Queue
show mls qos maps cos-output-q
show mls qos maps cos-dscp
As above but dscp-cos

Rotuers also have

show mls qos maps - COS and DSCP mappings
If traffic shaping enabled, tune Tc to 10ms
SP may have different service levels, check mapping

Other tips

Remove config if something like a printer on an interface that used to be a user (eg AutoQoS for voice)
default interface INTERFACE

Approach to resolve

Problem	Approach	Helpful IOS Commands
Troubleshooting QoS misconfig	Verify QoS is enabled, class map config, policy map config, and service policy operation	show mls qos, show class-map, show policy-map, show policy-map interface
Possible switch QoS misconfig	show commands to determine how input/egress queueing configured	show mls qos input-queue, show mls qos interface interface queueing, show mls qos maps cos-input-q, show mls qos maps cos-output-q, show mls qos maps cos-dscp, show mls qos maps dscp-cos
Possible router Qos	show commands to determine how queueing configured	show mls qos maps, show traffic-shape

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shaping-policing-lfi-shortnotes.md

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