MPLS-QoS
Jay Kumarasamy
jayk@cisco.com
© 2001, Cisco Systems.
1
Agenda
•
•
•
•
•
2001 Cisco Systems, Inc.
QoS Models
Differentiated Model Features
Modular QoS CLI (MQC)
MPLS QoS
Sample Examples
www.cisco.com
2
QoS Models
•
Integrated Services (IntServ)
•
Differentiated Services (Diffserv)
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The QoS Pendulum
Time
No state
Aggregated
state
Best Effort
DiffServ
Per-flow state
IntServ / RSVP
1. The original IP service
2. First efforts at IP QoS
3. Seeking simplicity and scale
4. Bandwidth Optimization & e2e SLAs
((IntServ+DiffServ+ Traffic Engineering))
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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
•
•
•
•
•
2001 Cisco Systems, Inc.
QoS Models
Differentiated Model Features
Modular QoS CLI (MQC)
MPLS QoS
Sample Examples
www.cisco.com
9
Differential Model Features
2001 Cisco Systems, Inc.
•
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
Length 1 Byte Len ID Offset TTL Proto FCS IP-SA IP-DA Data
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
•
•
•
•
•
2001 Cisco Systems, Inc.
QoS Models
Differentiated Model Features
Modular QoS CLI (MQC)
MPLS QoS
Sample Examples
www.cisco.com
16
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)#
class-map [match-any | match-all] class-name
• 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)#
policy-map policy-map-name
• 2. Create Policy Map (Service Policy) - Associate a
class map with one or more QoS policies (bandwidth, police, queuelimit, random detect, shape, set prec, set DSCP, set mpls exp).
router(config-if)#
service-policy {input | output} policy-map-name
• 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
•
•
•
•
•
2001 Cisco Systems, Inc.
QoS Models
Differentiated Model Features
Modular QoS CLI (MQC)
MPLS Quality of Service
Sample Examples
www.cisco.com
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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.
Rate-limit/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
queue”)
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MPLS QoS
Diff-Serv : DSCP
DSCP
EF
1 0 1 1 1 0
CU
DSCP
AFxy
x x x y y 0
CU
Drop
Class
Precedence
AF Class = 1, 2, 3, 4
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Drop Precedence = 2, 4, 6
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MPLS QoS
Diff-Serv over MPLS
• Two methods:
E-LSP
“Queue” inferred from Label and EXP field
“drop priority” inferred from label and EXP field
L-LSP
“Queue” inferred exclusively from Label
“drop priority” inferred from EXP field
<draft-ietf-mpls-diff-ext-03.txt>, by
Francious Le Faucheur, et al
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MPLS QoS
E-LSP Example
LDP/RSVP
LSR
LDP/RSVP
E-LSP
AF1
EF
• E-LSPs can be established by various label binding
protocols (LDP or RSVP)
• Example above illustrates support of EF and AF1 on
single E-LSP
Note: EF and AF1 packets travel on single LSP (single label)
but are enqueued in different queues (different EXP values)
• Queue is selected based on EXP
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MPLS QoS
L-LSP Example
LDP/RSVP
LDP/RSVP
LSR
L-LSPs
• L-LSPs can be established by various label binding
protocols (LDP or RSVP)
• Example above illustrates support of EF and AF1 on
separate L-LSPs
EF and AF1 packets travel on separate LSPs and are
enqueued in different queues (different label values)
• Queue is selected based on label, Discard is based on
ESP
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MPLS QoS
Edge DiffServ LSR with L-LSP
Non-MPLS
Diff-Serv Domain
IPv4 Packet
MPLS
Diff-Serv Domain
Edge LSR
MPLS Header
DSCP
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
|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1) identify incoming packet’s BA looking at incoming DSCP
2) pick the LSP/label which supports the right FEC and the right BA
3) mark the EXP field to reflect the packet’s BA
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MPLS QoS
Signaling
• E-LSPs can be set up with existing (non-DS-aware)
signalling
LDP, RSVP etc.
EXP -> PHB mapping is configured on every router as
per Diffserv
• L-LSPs require signalling extension to bind “queue” to a
label
New DIFFSERV object/TLV added to RSVP/LDP to
signal the “queue” in which to enqueue the label
Meaning of EXP bits is well-known (ie standardised for
each PSC)
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MPLS QoS
E-LSP & L-LSP Applicability
• MPLS over PPP and LAN:
both E-LSPs and L-LSPs are applicable
• MPLS over ATM:
only L-LSPs possible (EXP is not seen by
ATM LSR)
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MPLS QoS
• On non-ATM LSRs, MPLS-QoS is simple
• Copy or Map IP precedence to MPLS exp
field
• Exact same mechanism as IP-QoS
• Net result is end-to-end QoS
indistinguishable from non-MPLS (IP)
network
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MPLS QoS
MPLS QoS on ATM-LSRs
Two Challenges:
 No WRED in switches
 No EXP field in header
Solution Modes:
 ATM Forum PVC
 Multi VC (LSP)
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MPLS QoS
ATM Forum PVC Mode
ATM-LSR
PVC
• Looks like packet interface to MPLS QoS
• BW and other parameters configured on the PVC
• Requires significant amount of configuration
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MPLS QoS
Multi VC Mode
MPLS LVCs
ATM-LSR
• MPLS ATM core provides MPLS QoS at each link
• Configure each non-ATM LSR to support a number
of classes (2-4)
• Parallel LVCs automatically established
• Assign weight to each class
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MPLS QoS
Multi VC Mode
• Queuing is done through CBWFQ (eg.
Premium gets 80% of link, standard gets
20%)
• Unused bandwidth available to other
classes
• No per-router-pair configuration required,
as in ATM Forum PVC
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Agenda
•
•
•
•
•
2001 Cisco Systems, Inc.
QoS Models
Differentiated Model Features
Modular QoS CLI (MQC)
MPLS Class of Service
Examples
www.cisco.com
38
Examples
MPLS Network
PE 2
PE 3
CE 1
CE 4
P3
PE 4
PE 1
CE 2
CE 3
PE 5
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Examples
! Matching voice traffic from customer 1
Pe1(config)# class-map match-all cus1_voice
Pe1(config-cmap)# match interface POS1/0
Pe1(config-cmap)# match ip precedence 4
Pe1(config-cmap)# end
! Matching voice traffic from customer 2
Pe1(config)# class-map match-all cus2_voice
Pe1(config-cmap)# match interface POS1/1
Pe1(config-cmap)# match ip precedence 5
Pe1(config-cmap)# end
! Matching any e2e traffic
Pe1(config)# class-map erp
Pe1(config-cmap)# match ip precedence 2
Pe1(config-cmap)# end
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Examples
Pe1(config)# class-map isp_voice
Pe1(config-cmap)# match mpls experimental 4
Pe1(config-cmap)# end
Pe1(config)# class-map isp_erp
Pe1(config-cmap)# match mpls experimental 2
Pe1(config-cmap)# end
Pe1(config)# class-map isp_routine
Pe1(config-cmap)# match mpls experimental 1
Pe1(config-cmap)# end
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Examples
! Input Policy for setting experimental 4, 2, 1
Pe1(config)# policy-map pe1_input
Pe1(config-pmap)# class cus1_voice
Pe1(config-pmap-c)# set mpls experimental 4
Pe1(config-pmap-c)# exit
Pe1(config-pmap)# class cus2_voice
Pe1(config-pmap-c)# set mpls experimental 4
Pe1(config-pmap-c)# exit
Pe1(config-pmap)# class erp
Pe1(config-pmap-c)# set mpls experimental 2
Pe1(config-pmap-c)# exit
Pe1(config-pmap)# class class-default
Pe1(config-pmap-c)# set mpls experimental 1
Pe1(config-pmap)# exit
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Examples
! Output Policy for configuring bandwidth, queue…
Pe1(config)# policy-map policy pe1_output
Pe1(config-pmap)# class isp_voice
Pe1(config-pmap-c)# priority 100
Pe1(config-pmap-c)# exit
Pe1(config-pmap)# class isp_erp
Pe1(config-pmap-c)# bandwidth 50
Pe1(config-pmap-c)# queue-limit 30
Pe1(config-pmap-c)# exit
Pe1(config-pmap)# class class-default
Pe1(config-pmap-c)# bandwidth 20
Pe1(config-pmap-c)# queue-limit 100
Pe1(config-pmap-c)# exit
Pe1(config-pmap)# exit
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Examples
Pe1(config)# interface POS1/0
Pe1(config-if)# service-policy input pe1_input
Pe1(config)# interface POS1/1
Pe1(config-if)# service-policy input pe1_input
Pe1(config)# interface POS2/0
Pe1(config-if)# service-policy output pe1_output
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Examples
MPLS Network
PE 2
PE 3
CE 1
LSC1
PE 1
LC-ATM
CE 4
PE 4
ATM Core
CE 2
CE 3
PE 5
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Examples
Pe1(config)# ATM1/0
Pe1(config-if)# no ip address
Pe1(config-if)# atm clock INTERNAL
Pe1(config-if)# no atm ilmi-keepalive
Pe1(config-if)# exit
Pe1(config)# interface ATM1/0.1 tag-switching
Pe1(config-if)# ip unnumbered loopback0
Pe1(config-if)# tag-switching multi-vc
Pe1(config-if)# tag-switching atm vpi 2-5
Pe1(config-if)# tag-switching ip
! Sets up 3 LVCs.
Pe1(config)# cos-map 1
Pe1(config-mpls-cos-map)# class 3 standard
Pe1(config-mpls-cos-map)# exit
! 3 - standard
! 2 - premium
! 1 - standard
! 0 – available
Pe1(config)# mpls prefix-map 1 access-list 1 cos-map 1
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Examples
! Matching voice traffic from customer 1
Pe1(config)# class-map match-all cus1_voice
Pe1(config-cmap)# match interface POS1/0
Pe1(config-cmap)# match ip precedence 4
Pe1(config-cmap)# end
! Matching voice traffic from customer 2
Pe1(config)# class-map match-all cus2_voice
Pe1(config-cmap)# match interface POS1/1
Pe1(config-cmap)# match ip precedence 5
Pe1(config-cmap)# end
! Matching any e2e traffic
Pe1(config)# class-map erp
Pe1(config-cmap)# match ip precedence 2
Pe1(config-cmap)# end
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Examples
P! Input Policy for setting experimental 2, 1, 0
e1(config)# policy-map pe1_input
Pe1(config-pmap)# class cus1_voice
Pe1(config-pmap-c)# set mpls experimental 2
Pe1(config-pmap-c)# exit
Pe1(config-pmap)# class cus2_voice
Pe1(config-pmap-c)# set mpls experimental 2
Pe1(config-pmap-c)# exit
Pe1(config-pmap)# class erp
Pe1(config-pmap-c)# set mpls experimental 1
Pe1(config-pmap-c)# exit
Pe1(config-pmap)# class class-default
Pe1(config-pmap-c)# set mpls experimental 0
Pe1(config-pmap)# exit
! Voice for customer 1
! Voice for customer 2
! ERP data
! All other traffic
Pe1(config)# class-map isp_voice
Pe1(config-cmap)# match mpls experimental 2
Pe1(config-cmap)# end
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Examples
Pe1(config)# class-map isp_erp
Pe1(config-cmap)# match mpls experimental 1
Pe1(config-cmap)# end
Pe1(config)# class-map isp_available
Pe1(config-cmap)# match mpls experimental 0
Pe1(config-cmap)# end
! Output Policy for configuring bandwidth, queue…
Pe1(config)# policy-map policy pe1_output
Pe1(config-pmap)# class isp_voice
Pe1(config-pmap-c)# priority 100
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Examples
Pe1(config-pmap-c)# exit
Pe1(config-pmap)# class isp_erp
Pe1(config-pmap-c)# bandwidth 50
Pe1(config-pmap-c)# queue-limit 30
Pe1(config-pmap-c)# exit
Pe1(config-pmap)# class isp_available
Pe1(config-pmap-c)# bandwidth 20
Pe1(config-pmap-c)# queue-limit 100
Pe1(config-pmap-c)# exit
Pe1(config-pmap)# exit
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Examples
LSC1
Interface XTagATM11
extended-port ATM3/0 bpx 1.1
tag-switching atm vpi 2-15
tag-switching atm cos available 20
tag-switching atm cos standard 30
tag-switching atm cos premium 50
tag-switching ip
Interface XTagATM12
extended-port ATM3/0 bpx 1.2
tag-switching atm vpi 2-15
tag-switching atm cos available 20
tag-switching atm cos standard 30
tag-switching atm cos premium 50
tag-switching ip
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Thank You!
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