MPLS cisco QOS VPN full 02 mpls qos jayk

MPLS-QoS
Jay Kumarasamy


© 2001, Cisco Systems.

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Agenda

• QoS Models
• Differentiated Model Features
• Modular QoS CLI (MQC)
• MPLS QoS
• Sample Examples

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QoS Models

•

Integrated Services (IntServ)

•

Differentiated Services (Diffserv)

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The QoS Pendulum
Time
N o s ta te

A g g re g a te d
s ta te

B e s t E ffo rt

D iffS e r v

P e r -flo w s ta te

In t S e r v / R S V P

1 . T h e o r ig in a l IP s e r v ic e
2 . F ir s t e f f o r t s a t IP Q o S
3 . S e e k in g s im p lic ity a n d s c a le
4 . B a n d w id th O p tim iz a tio n & e 2 e S L A s
( ( In t S e r v + D if f S e r v + T r a f f ic E n g in e e r in g ) )

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Integrated Model

• Application requests a specific kind of QoS service, through explicit
signaling.
• Resource Reservation Protocol (RSVP) is used by applications to
signal their QoS requirements to the router.
• Complex to use.
• Difficult to support with a large number of RSVP connections, due to:

the amount of state information required for every

flow.

the amount of control traffic
• Fine grain, providing strict QoS.

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Differentiated Model
• Qos is provided by differential treatment to
each packet or class of packets.
• No explicit signaling from the application.
• This model is appropriate for aggregate
flows.
• Coarse grain, not strict QoS (no guarantees).

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Differentiated Model
Divide Traffic into Classes
Differentiated
IP Services

Voice

Platinum Class
Low Latency

Gold

Guaranteed: Latency
and Delivery

Silver

Guaranteed Delivery

Bronze

Best Effort Delivery

E-Commerce
Application
Traffic

Traffic
Classification

E-mail, Web
Browsing
Voice

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Differentiated Model
Classification/
Marking policy

Drop
policy

Scheduling
policy

Switching
Fabric
rx queue

tx queue
tx hw

recv hw

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Agenda

• QoS Models
• Differentiated Model Features
• Modular QoS CLI (MQC)
• MPLS QoS
• Sample Examples

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www.cisco.com

9


Differential Model Features

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•

Classification

•

Marking

•

Policing and Shaping

•

Congestion Avoidance

•

Congestion Management

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Differentiated Model Features
Classification
Most fundamental QoS building block
The component of a QoS feature that
recognizes and distinguishes between
different traffic streams
Without classification, all packets are
treated the same

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Differentiated Model Features
Marking
Layer 3
IPV4

Version ToS
Len ID Offset TTL Proto FCS IP­SA IP­DA Data
Length 1 Byte

7

6

5

4

IP Precedence

3

2

1

0

Unused 
Bits;

DSCP
0
1
2
3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
Label

| EXP |S|
TTL
|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Differentiated Model Features
Policing and Shaping
• Policing is the QoS component that limits
incoming traffic flow to a configured bit
rate
• Shaping is the QoS feature component
that regulates outgoing traffic flow to a
configured bit rate
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Differentiated Model Features
Congestion Avoidance
Drop Policy
• Tail Drop

• Random Early Detection (RED)
• Weighted Random Early Detection (WRED)

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Differentiated Model Features
Congestion Management

Scheduling Policy
• FIFO
• Fair Queuing
• Weighted Fair Queuing (WFQ)
• Class Based Weighted Fair Queuing (CBWFQ)
• Low Latency Queuing (LLQ)

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Agenda

• QoS Models

• Differentiated Model Features
• Modular QoS CLI (MQC)
• MPLS QoS
• Sample Examples

2001 Cisco Systems, Inc.

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Modular QoS CLI
Modular QoS CLI (MQC)
Command syntax introduced in 12.0(5)T
Reduces configuration steps and time
Uniform CLI across all main Cisco IOS-based
platforms
Uniform CLI structure for all QoS features

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Basic MQC Commands
router(config)#

class­map [match­any | match­all] class­name 

• 1. Create Class Map ­ a traffic class ( match access list, input 

interface, IP Prec, DSCP, protocol (NBAR) src/dst MAC address, mpls 
exp).

router(config)#

policy­map policy­map­name

• 2. Create Policy Map (Service Policy) ­ Associate a 
class map with one or more QoS policies (bandwidth, police,  queue­
limit, random detect, shape, set prec, set DSCP, set mpls exp).
router(config­if)#

service­policy {input | output} policy­map­name

• 3. Attach Service Policy ­ Associate the policy map with an 
input or output interface.

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Basic MQC Commands
• 1. Create Class Map

Router(config)# class-map class1
Router(config-cmap)# match ip precedence 5
Router(config-cmap)# exit

• 2. Create Policy Map
Router(config)# policy-map policy1
Router(config-pmap)# class class1
Router(config-pmap-c)# set mpls experimental 5
Router(config-pmap-c)# bandwidth 3000
Router(config-pmap-c)# queue-limit 30
Router(config-pmap)# exit

• 3. Attach Service Policy
Router(config)# interface e1/1
Router(config-if)# service-policy output policy1
Router(config-if)# exit
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Agenda

• QoS Models
• Differentiated Model Features
• Modular QoS CLI (MQC)
• MPLS Quality of Service
• Sample Examples

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MPLS QoS
ATM-LSR

Conventional
Router

Label Edge
Routers

Label Switching
Router (LSR)

• Note: End to end service is IP; therefore, IP
class of service is what MPLS must support
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MPLS QoS

ISP Customer

2) Match IP Prec/DSCP; Set 
MPLS EXP.
Rate­limit/Police and apply drop 
policy
MPLS

Core
3) Invoke QoS Policy 
Action Based on Edge
Classification (based on 
MPLS EXP),  e.g. LLQ,
CBWFQ,  Drop Policy
Low Priority via WRED if 
rate limit exceeded

1) Packet Classification
through IP Prec/DSCP 

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MPLS QoS
• ‘Differentiated Model’ approach: Set IP precedence or
MPLS Exp bit at the edge of the network

• WRED by MPLS Exp, and WFQ by class in the core
• Because MPLS is there primarily to transport IP,
MPLS’s primary QoS goal is to support existing IP
QoS models
• Because MPLS is there to support very large scale
operations, MPLS should also be capable of
supporting Diff-Serv in the future

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MPLS QoS
0
1
2
3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
Label
| EXP |S|
TTL
|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

• Copy of IP Precedence into MPLS EXP

• Mapping of IP Precedence into MPLS EXP
MPLS Domain

Non-MPLS
Domain
IPv4 Packet

MPLS

MPLS
EXP: xyz

Prec: xyz
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Hdr

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Prec: xyz
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MPLS QoS
Diff-Serv : Jargon
• PHB = Per Hop Behavior
The Diff-Serv treatment (scheduling/dropping) applied by a Router to all
the packets which are to experience the same Diff-Serv service
• DSCP = Differentiated Services Code Point
The value in the IP Header indicating which PHB is to be applied to the

packet
• BA = Behavior Aggregate
The set of all the packets which have the same DSCP (and thus that will
receive the same PHB)
• OA = Ordered Aggregate
The set of BAs which have an ordering constraint (“must go into the
same queue”)
• PSC = PHB Scheduling Class
The set of PHBs applied to an OA (the set of PHBs using the same
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queue”)

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