Juniper Hierarchical Class User Manual

Junos® OS

Hierarchical Class of Service User Guide

Published

2021-04-17

ii

Juniper Networks, Inc. 1133 nn v n Way Sunnyvale, California 94089 USA

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Junos® OS Hierarchical Class of Service User Guide
Copyright © 2021 Juniper Networks, Inc. All rights reserved.
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END USER LICENSE AGREEMENT

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iii

Table of Contents

About This Guide | xv

1Hierarchical Class of Service

C n		r n	Hierarchical Class of Service on MX Series 5G Universal R				n	rms | 2
Hierarchical Class of Service Overview |				2
Hierarchical Class of Service Network Scenarios |						6
Understanding Hierarchical Scheduling |				7
Priority		r	n in Hierarchical Scheduling | 11
C n		r n	Hierarchical Schedulers for CoS | 15
Hierarchical Schedulers and r c Control					r	s | 16
Example: Building a Four-Level Hierarchy of Schedulers | 18
Scheduling and Shaping in Hierarchical CoS Queues for r c Routed to GRE Tunnels | 24
Example: Performing Output Scheduling and Shaping in Hierarchical CoS Queues for r								c Routed
	to GRE Tunnels | 26
	Requirements | 26
	Overview | 27
	C n		r n | 27
	r	c	n | 41
C n		r n	Ingress Hierarchical CoS on Enhanced Queuing DPCs | 45
C n		r n	Hierarchical Class of Service on MICs, MPCs, MLCs, and Aggregated
	Ethernet Interfaces | 48
Understanding Hierarchical Scheduling for MIC and MPC Interfaces | 48
C n		r n	Ingress Hierarchical CoS on MIC and MPC Interfaces | 51
Per-Unit Queuing and Hierarchical Queuing for MIC and MPC Interfaces | 53
Dedicated Queue Scaling for CoS C n				r	ns on MIC and MPC Interfaces Overview | 57
	r R	c	n in Hierarchical CoS Queues | 60

iv

Example: Reducing				r in Hierarchical CoS Queues | 64
Requirements | 64
Overview | 64
C n		r	n | 64
	r	c	n | 70

Hierarchical Schedulers on Aggregated Ethernet Interfaces Overview | 72

C n r n	Hierarchical Schedulers on Aggregated Ethernet Interfaces | 73
Example: C	n r n Scheduling Modes on Aggregated Interfaces | 74

Increasing Available Bandwidth on Rich-Queuing MPCs by Bypassing the Queuing Chip | 81

2Hierarchical CoS for Subscriber Management

Hierarchical Class of Service for Subscriber Management | 85

Hierarchical Class of Service for Subscriber Management Overview | 85

Understanding Hierarchical CoS for Subscriber Interfaces | 87

Hardware Requirements for Dynamic Hierarchical CoS | 96
C	n	r n	S c Hierarchical Scheduling in a Dynamic r	| 98
C	n	r n	Hierarchical CoS for a Subscriber Interface of Aggregated Ethernet Links | 99
C	n	r n	Hierarchical CoS on a S c PPPoE Subscriber Interface | 101

Example: Maintaining a Constant r c Flow by C n r n a S c VLAN Interface with a

Dynamic		r		for Subscriber Access | 102
Requirements |				102
Overview | 103
C n	r		n |	104
r	c	n | 118

Applying CoS to Groups of Subscriber Interfaces | 120

CoS for Interface Sets of Subscribers Overview | 120

C n r n		an Interface Set of Subscribers in a Dynamic r		| 123
Example: C		n	r n a Dynamic Interface Set of VLAN Subscribers | 124
	Requirements | 125
	Overview | 125
	C n	r n	the Dynamic VLANs | 125

v

	C	n	r n	Dynamic r	c Scheduling and Shaping | 128
	C	n	r n	the Interface Set in the Dynamic r			| 134
	C n		r n	DHCP Access | 136
	C n		r n	RADIUS	n c	n | 138
		r c	n | 145
Example: C			n	r n a Dynamic Service VLAN Interface Set of Subscribers in a Dynamic r				| 146
	Requirements | 146
	Overview | 146
	C n		r	n | 147
		r c	n | 150
C	n	r n	Hierarchical Scheduling for MPLS Pseudowire Interfaces | 152
Hierarchical CoS on MPLS Pseudowire Subscriber Interfaces Overview | 152
CoS C		n	r	n Overview for MPLS Pseudowire Subscriber Interfaces | 153
CoS Two-Level Hierarchical Scheduling on MPLS Pseudowire Subscriber Interfaces | 155
C	n	r n	CoS Two-Level Hierarchical Scheduling for MPLS Pseudowire Subscriber Interfaces | 157
CoS Three-Level Hierarchical Scheduling on MPLS Pseudowire Subscriber Interfaces | 159
C	n	r n	CoS Three-Level Hierarchical Scheduling for MPLS Pseudowire Subscriber Interfaces
	(Logical Interfaces over a Transport Logical Interface) | 164
C	n	r n	CoS Three-Level Hierarchical Scheduling for MPLS Pseudowire Subscriber Interfaces
	(Logical Interfaces over a Pseudowire Interface Set) | 166
C	n	r n	Hierarchical Scheduling for L2TP | 170
CoS for L2TP LAC Subscriber Interfaces Overview | 170
C n		r n	Dynamic CoS for an L2TP LAC Tunnel | 173
CoS for L2TP LNS Inline Services Overview | 175
C	n	r n	an Inline Service Interface for L2TP LNS | 177
C n		r n	Dynamic CoS for an L2TP LNS Inline Service | 178
r v n n			Bandwidth C		n n	n on Subscriber Interfaces | 181

Hierarchical CoS Shaping-Rate Adjustments Overview | 181

Shaping Rate Adjustments for Subscriber Local Loops Overview | 184

vi

Guidelines for C				n	r n Shaping-Rate Adjustments for Subscriber Local Loops | 185
C n		r n	the Minimum Adjusted Shaping Rate on Scheduler Nodes for Subscribers | 186
		Overview | 186			c Minimum Adjusted Shaping Rate on Scheduler Nodes | 187
		C n	r n	a S
		C n	r n	a Dynamic Minimum Adjusted Shaping Rate on Scheduler Nodes | 187
C n		r n	Shaping-Rate Adjustments on Queues | 188

Overview | 188

C n r n a S c Shaping-Rate Adjustment for Queues | 188

C n r n a Dynamic Shaping-Rate Adjustment for Queues | 189

Enabling Shaping-Rate Adjustments for Subscriber Local Loops | 191

C	n	r n	S c Logical Interface Sets to Serve as CoS Hierarchical Scheduler Nodes for
	Subscriber Loops | 191
C	n	r n	the Logical Interfaces That Compose the S c Logical Interface Sets | 192
C	n	r n	Hierarchical CoS on the S c Logical Interface Sets That Serve as Hierarchical
	Scheduler Nodes for Subscriber Local Loops | 193
C n		r n	ANCP nc n y That Supports and Drives Shaping-Rate Adjustments for
	Subscriber Local Loops | 195

Disabling Shaping-Rate Adjustments for Subscriber Local Loops | 197

Disabling Hierarchical Bandwidth Adjustment for Subscriber Interfaces with Reverse-OIF Mapping | 198

Example: C n			r n Hierarchical CoS Shaping-Rate Adjustments for Subscriber Local Loops | 199
Verifying the C		n	r	n of Shaping-Rate Adjustments for Subscriber Local Loops | 203
Verifying the C		n	r	n of ANCP for Shaping-Rate Adjustments | 204
Using Hierarchical CoS to Adjust Shaping Rates Based on M c s r c | 205
C n	r n Targeted			s r b	n of Subscribers on Aggregated Ethernet Interfaces | 209
s r b	n of Demux Subscribers in an Aggregated Ethernet Interface | 209

Providing Accurate Scheduling for a Demux Subscriber Interface of Aggregated Ethernet Links | 212

C	n	r n	the s r b	n Type for Demux Subscribers on Aggregated Ethernet Interfaces | 214
C n		r n Link and Module Redundancy for Demux Subscribers in an Aggregated Ethernet
	Interface | 215
C	n	r n	Rebalancing of Demux Subscribers in an Aggregated Ethernet Interface | 215

vii

	C	n	r n	Periodic Rebalancing of Subscribers in an Aggregated Ethernet Interface | 216
	C	n	r n	Manual Rebalancing of Subscribers on an Aggregated Ethernet Interface | 216
Example: S			r	n Targeted M c s r c for Demux Subscribers on Aggregated Ethernet

Interfaces | 217

Requirements | 218

Overview | 218

C n r n | 219 r c n | 227

Verifying the	s r b	n of Demux Subscribers in an Aggregated Ethernet Interface | 232
C n r n the	s r b	n Type for PPPoE Subscribers on Aggregated Ethernet Interfaces | 233
Verifying the	s r b	n of PPPoE Subscribers in an Aggregated Ethernet Interface | 234

Applying CoS Using Parameters Received from RADIUS | 236

Subscriber Interfaces That Provide n CoS Parameters Dynamically Obtained from RADIUS | 236

Changing CoS Services Overview | 241

	CoS r	c Shaping				r b s for Dynamic Interface Sets and Member Subscriber Sessions
	Overview | 247
	Guidelines for C			n		r n CoS	r c Shaping		r b s for Dynamic Interface Sets and Member
	Subscriber Sessions | 249
	C n	r n	n	CoS Parameters Dynamically Obtained from RADIUS | 250
	C n	r n	S	c Default Values for r				c Scheduling and Shaping | 251
	Applying CoS r			c S		n	r b s to Dynamic Interface Sets and Member Subscriber
	Sessions | 253
	CoS r	c Shaping			r	n	Variables for Dynamic Interface Sets | 256
	Example: C		n	r n	Dynamic Hierarchical Scheduling for Subscribers | 263
3	C n	r		n Statements and				r	n Commands
	C n	r	n Statements | 275

accept | 280

address-assignment (Address-Assignment Pools) | 282

n c n (DHCP Local Server) | 285

viii

n	c	n (DHCP Relay Agent) | 287
n	c	n	r r | 289
c	n	r	| 291

adjust-minimum | 294 adjust-percent | 295 atm-service | 296

br s z (Schedulers) | 298

cbr | 300
c ss rs (	n n) | 302

css rs (Logical Interface) | 304

css rs (Physical Interface) | 305

code-points (CoS) | 307

y b	r r	| 308
demux0 (Dynamic Interface) | 310
m x	ns (Dynamic Interface) | 313

demux-source (Dynamic IP Demux Interface) | 314 demux-source (Dynamic Underlying Interface) | 315 demux-source (Underlying Interface) | 317

cr b s (Address-Assignment Pools) | 318

dhcp-local-server | 325 dhcp-relay | 338

drop-probability (Interpolated Value) | 355 drop-probability (Percentage) | 356

rr (Schedulers) | 358

r	r	m	(Schedulers) | 359
r	r	s |	360

ix

dscp (CoS C ss			rs) | 362
dscp (Rewrite Rules) | 363
dscp-ipv6 (CoS Rewrite Rules) | 365
yn m c	r	(DHCP Local Server) | 367
yn m c	r	(VLAN) | 369
yn m c	r	s | 371
egress-shaping-overhead | 385
excess-bandwidth-share | 387
excess-priority | 389
excess-rate (Dynamic r				c Shaping) | 391
excess-rate-high (Dynamic				r	c Shaping) | 392
excess-rate-low (Dynamic				r	c Shaping) | 394
family | 396
family (Address-Assignment Pools) | 402
family (Dynamic Demux Interface) | 404
family (Dynamic PPPoE) | 406
family (Dynamic Standard Interface) | 408
v	(Drop	r	s) | 411

v(Interpolated Value) | 412

r (C	n	r n )	| 414
fl x b	v n	n	| 416

forwarding-classes (Class-of-Service) | 417 group (DHCP Local Server) | 419

guaranteed-rate | 424 hierarchical-scheduler | 426

hierarchical-scheduler (Subscriber Interfaces on MX Series Routers) | 428

x

ieee-802.1ad | 430
inet-precedence (CoS C ss					rs) | 432
input-excess-bandwidth-share | 433
input-scheduler-map | 435
input-shaping-rate (Logical Interface) | 437
input-shaping-rate (Physical Interface)							| 439
n	r	c c	n r	r	| 440
n	r	c c	n r	r	r m n n		| 442
interface (DHCP Local Server) | 444
interface-set (Ethernet Interfaces)						| 447
interface-set (Hierarchical Schedulers)							| 448
interface-set (IP Demux Interfaces) | 450
interfaces		| 451
interfaces (CoS) | 453
interfaces (S			c and Dynamic Subscribers) | 456
internal-node | 463
interpolate | 464
loss-priority (BA C ss				rs)	| 465
loss-priority (Scheduler Drop r						s)	| 467
max-queues | 468
max-queues-per-interface | 471
member-link-scheduler | 473

mode (Layer 2 Tunneling Protocol Shaping) | 475

r	c c	n r	r	|	477
r	c c	n r	r	r	m n n | 479
v r	cc	n n	| 481

xi

pap (Dynamic PPP) | 482 peak-rate | 484 per-unit-scheduler | 485

pool (Address-Assignment Pools) | 487 ns (Dynamic PPPoE) | 490

ns (Dynamic PPP) | 491 priority (Schedulers) | 494

r(Access) | 496

protocols | 503
proxy-arp | 506
qos-adjust-hierarchical | 508
queue (Global Queues) | 510
radius (Access	r	) | 511
radius-server | 516
range (Address-Assignment Pools) | 522
ranges (Dynamic VLAN) | 524
rewrite-rules (	n	n)	| 525
rewrite-rules (Interfaces)			| 527
r n ns nc s (M			R	n	n	s) | 529
scheduler (Scheduler Map) | 532
scheduler-map (Interfaces and				r	c C	n r r	s) | 533
scheduler-maps (For Most Interface Types) | 534
schedulers (CoS) | 536
secret (RADIUS) | 537
server (Dynamic PPPoE) | 539
server-group | 540

xii

shaping-rate (Applying to an Interface) | 542 shaping-rate (Schedulers) | 545

shaping-rate (Oversubscribing an Interface) | 547 shaping-rate-excess-high | 550 shaping-rate-excess-low | 552 shaping-rate-priority-high | 554 shaping-rate-priority-low | 556 shaping-rate-priority-medium | 559 shared-bandwidth-policer (C n r n ) | 561 shared-instance | 562

shared-scheduler | 564

s m	r (Applying to an Interface) | 565
s m	r | 566

sn r (VPLS) | 569

stacked-interface-set (Dynamic					r	s) | 570
stacked-vlan-tagging | 572
term (Simple Filter)			| 573
three-color-policer (Applying) | 575
three-color-policer (C				n r n )	| 577
r	c c n r	r	s	| 579
r	c m n	r | 582

transmit-rate (Schedulers) | 587 transparent | 590

underlying-interface (demux0) | 592 underlying-interface (Dynamic PPPoE) | 593 unit | 595

xiii

unit (Dynamic Demux Interface) | 597 unit (Dynamic PPPoE) | 599

unnumbered-address (Dynamic PPPoE) | 602

unnumbered-address (Dynamic r		s) | 603
unnumbered-address (Ethernet) | 606
s r r x (DHCP Relay Agent) | 608
vlan-id (Dynamic r	s) | 610

vlan-id (VLAN ID to Be Bound to a Logical Interface) | 611 vlan-model | 613

vlan-ranges | 614 vlan-tag | 616 vlan-tags | 617 vlan-tags-outer | 619

vlan-tags (Stacked VLAN Tags) | 620

rn Commands | 625

show access-cac interface-set | 625
show class-of-service	s m n	c n r r	| 628
show class-of-service c	ss r |	631

show class-of-service interface | 634 show class-of-service scheduler-map | 681

show class-of-service scheduler-hierarchy interface | 686 show class-of-service scheduler-hierarchy interface-set | 689 show interfaces | 691

show interfaces (PPPoE) | 830

show interfaces demux0 (Demux Interfaces) | 848 show interfaces queue | 863

xiv

show subscribers | 924

xv

About This Guide

Use this guide to understand and c		n	r hierarchical class of service (CoS) features in Junos OS to
n service levels that provide		r	n delay,	r and packet loss c r c r s cs to r c r
c	ns served by s c c r	c fl	ws Applying CoS features to each device in your network
ensures quality of service (QoS) for		r	c throughout your n r network.

RELATED DOCUMENTATION

The Day One: Deploying Basic QoS

Day One: Dynamic Subscriber Management

1

PART

Hierarchical Class of Service

C	n	r n	Hierarchical Class of Service on MX Series 5G Universal R n
		rms | 2
C	n	r n	Hierarchical Class of Service on MICs, MPCs, MLCs, and Aggregated

Ethernet Interfaces | 48

2

CHAPTER 1

C n r n Hierarchical Class of Service on MX Series 5G Universal R n rms

IN THIS CHAPTER
	Hierarchical Class of Service Overview | 2
	Hierarchical Class of Service Network Scenarios |			6
	Understanding Hierarchical Scheduling | 7
	Priority	r	n in Hierarchical Scheduling | 11
	C n	r n	Hierarchical Schedulers for CoS | 15	s | 16
	Hierarchical Schedulers and r c Control r
	Example: Building a Four-Level Hierarchy of Schedulers | 18
	Scheduling and Shaping in Hierarchical CoS Queues for r c Routed to GRE Tunnels | 24
	Example: Performing Output Scheduling and Shaping in Hierarchical CoS Queues for r c Routed to GRE
	Tunnels | 26
	C n	r n	Ingress Hierarchical CoS on Enhanced Queuing DPCs | 45

Hierarchical Class of Service Overview

Hierarchical class of service (HCoS) is the ability to apply r c schedulers and shapers to a hierarchy of

scheduler nodes. Each level of the scheduler hierarchy can be used to shape r										c based on	r n
criteria such as		c	n user, VLAN, and physical port.
This allows you to support the requirements of							r n services,	c	ns and users on the same
physical device and physical infrastructure.
HCoS is implemented primarily using r c c						ss	rs at the ingress and hierarchical schedulers and
shapers at the egress.
A c ss	r is a	r that labels			r c at the device ingress based on c			n	r b	parameters such as
c	n or	s n	n	r	c is c ss	into what is called a forwarding equivalence class (FEC).
The FEC	n s a class of			r	c that receives common treatment.

3

Schedulers, and their associated shapers, is the				nc n that controls the r c bandwidth,	r (delay
v r	n) and packet loss priority at the egress of the device.
Hierarchical schedulers are used to apply m				levels of scheduling and shaping with each level
applied to		r n c ss c	ns such as forwarding equivalence class, VLAN, and physical interface
(port) as shown in Figure 1 on page 3.

Figure 1: Hierarchical Scheduling Architecture

NOTE: Hierarchical class of service is also referred to as Hierarchical Quality of Service (HQoS) in

other vendor’s		c m n	n
A typical	c	n of HCoS is to c		n	r m	levels of egress schedulers and shapers, at the
subscriber edge, using dynamic r				s to provide r		c shaping and r r z	n at the subscriber
VLAN level and for m			classes of r		c

4

Dynamic r s are a mechanism that allows you to dynamically apply schedulers and shapers to individual subscribers or groups of subscribers.

To learn more about HCoS, the following topics are very helpful:

•	Junos CoS on MX Series 5G Universal R n		rms Overview
•	CoS Features and m	ns on MX Series Routers

• CoS Features of the Router Hardware, PIC, MIC, and MPC Interface Families

• How Schedulers

n Output Queue r r s

•Subscriber Access Network Overview

•CoS for Subscriber Access Overview

•"Hierarchical Class of Service for Subscriber Management Overview" on page 85

The Junos OS hierarchical schedulers support up to v levels of scheduler hierarchies on MX Series devices when using enhanced queuing Dense Port Concentrators (DPCs) or n r n queuing Modular Port Concentrators (MPCs), and Modular Interface Cards (MICs). It is important to know the

c	b	s of your hardware with respect to HCoS. The following are a few s to help you:
•	Only certain hardware supports the v v scheduler hierarchy of HCoS.

•The number of queues and logical interfaces supported is dependent upon exactly what hardware you are using.

•The MX Series Packet Forwarding Engine handles guaranteed bandwidth and scheduler node weight r n y than other Packet Forwarding Engines.

• The	n	r	n	queuing MPCs and MICs have a certain granularity with respect to the shaping and
delay b			r values. The values used are not necessarily exactly the values c n r
To learn more about				rm support for HCoS, use the Juniper Networks Feature Explorer (	s
n	r	n	r n	r x r r ). In the Feature Explorer, search on hierarchical schedulers.
In	n it is important to note the following:

• HCoS is most frequently used to enforce service level agreements at the subscriber edged using dynamic r c control r s

•Hierarchical schedulers can also be applied to Ethernet pseudowire interfaces, aggregated Ethernet interfaces, Layer 2 Tunnel Protocol (L2TP) network server (LNS) inline services, and GRE tunnels.

• Hierarchical ingress policing is a feature that is complimentary to and ft n used in c n nc n with HCoS.

5

• There are other features in Junos OS that have similar sounding names.

NOTE: The hierarchical scheduler and shaper feature supported on the SRX Series devices is not the HCoS feature described here.

Before planning HCoS for you network, you should learn about HCoS,							n you needs, plan how you
want to implement HCoS, and test the			r	n in a simulated environment.
Table 1: Resources for Learning More About HCoS
Document			scr	n
Day One: Deploying Basic QoS		This book is a good resource for learning the basics of CoS on
Juniper Networks Books		Juniper Networks devices.
Juniper MX-Series O'Reilly Media		Learn about the advanced features of HCoS. This book provides
		an in-depth			scr	n of how HCoS works and how it can be
		deployed. It also provides a lab tested topology and c						n	r n
		example.
Day One: Dynamic Subscriber		Learn how to use HCoS in c n nc					n with dynamic	r	c
Management Juniper Networks		control		r	s for subscriber management. This book also
Books		includes		r	b s	n
QoS Enabled Networks John		This book is an				n source for studying QoS.
Wiley & Sons
c m n	n related to HCoS is consolidated in the Hierarchical Class of Service User Guide.

RELATED DOCUMENTATION

Hierarchical Class of Service for Subscriber Management Overview | 85

Hierarchical Class of Service Network Scenarios

Understanding Hierarchical Scheduling

6

Hierarchical Class of Service Network Scenarios

IN THIS SECTION

Services to Subscribers | 6

Services to Businesses | 7

Wireless Backhaul | 7

Hierarchical class of service (HCoS) can be used to provide granular control of r c for a variety of r n c ns

NOTE: Hierarchical class of service is also referred to as Hierarchical Quality of Service (HQoS) in other vendor’s c m n n

Hierarchical class of service is most frequently used in the following scenarios:

Services to Subscribers

M s rv c network operators face a challenge to provide r n types of services on the same infrastructure to r s n and business subscribers. The network operator needs to make sure each subscriber gets the network resources they paid for and each service gets the network resources it needs to operate properly.

If no CoS is applied, one service could consume most of the bandwidth of the transmission infrastructure and starve the other services.

Using hierarchical class of service, the network edge device can have up to v levels of scheduling and r r z n So the r c can be shaped and r r z per customer and per service type. Controlling r c in this way provides the ability to deliver the required service level for each subscriber for each

service type.
By allowing network operators to consolidate	r n services and m	customers on the same
physical infrastructure, hierarchical class of service helps maximize the ability to			r revenue
n r n services while simultaneously minimizing capital cost.

7

Services to Businesses

Hierarchical class of service is a valuable tool for service providers that support business customers who

are running	c	ns with	r n r r z	n and scheduling requirements over the same
infrastructure. In this scenario hierarchical class of service allows lower priority r c to fully					z the

available bandwidth on a port, while simultaneously ensuring low latency and guaranteed bandwidth to

higher priority r	c on the same port.
This allows a provider to consolidate		r n services on the same physical device and physical
infrastructure thus	m z n network resources while maintaining the required level of service.
All of this maximizes revenue and minimizes cost

Wireless Backhaul

In a cellular network the operator might want to				r business services along with its cell tower r c
One of the main challenges is to make sure that the				m s ns	v	cell	r	c is not	c	by the
business services running on the same infrastructure. Each type of						r	c has its own priority fl ws and
bandwidth constraints. For example, wireless backhaul is very s					ns	v	to fl	c	ns in the packet
stream (	r) because it relies on sync r n z		n
In this scenario, hierarchical class of service allows each type of					r	c to receive the required resources
and quality of service while being delivered over the same infrastructure.
By consolidate		r n services on the same physical infrastructure, HCoS helps maximize revenue and
minimize cost.

RELATED DOCUMENTATION

Hierarchical Class of Service Overview

Hierarchical Class of Service for Subscriber Management Overview | 85

Understanding Hierarchical Scheduling

IN THIS SECTION

Hierarchical Scheduling Terminology | 8

Scheduler Node-Level s n ns in Hierarchical Scheduling | 9

8

Hierarchical Scheduling at Non-Leaf Nodes | 10

Hierarchical class of service (HCoS) is a set of c for network r c based on criteria such as user,

b s that enable you to apply unique CoS treatment c n VLAN, and physical port.

This allows you to support the requirements of		r n services,	c	ns and users on the same
physical device and physical infrastructure.
This topic covers the following n rm	n

Hierarchical Scheduling Terminology

Hierarchical scheduling introduces some new CoS terms and also uses some familiar terms in

r n

contexts:

•

Customer VLAN (C-VLAN)—A C-VLAN,

n

by IEEE 802.1ad. A stacked VLAN contains an outer

tag corresponding to the S-VLAN, and an inner tag corresponding to the C-VLAN. A C-VLAN

ft n

corresponds to CPE. Scheduling and shaping is

ft n used on a C-VLAN to establish minimum and

maximum bandwidth limits for a customer. See also S-VLAN.

•

Interface set—A logical group of interfaces that describe the c

r c

r s cs of set of service VLANs,

logical interfaces, customer VLANs, or aggregated Ethernet interfaces. Interface sets establish the set

and name the r

c control

r

s See also Service VLAN.

•

Scheduler— A scheduler

n

s the scheduling and queuing c

r c

r s cs of a queue. Transmit rate,

scheduler priority, and b

r size can be s

c

In

n a drop r

may be referenced to

describe WRED c n s

n control aspects of the queue. See also Scheduler map.

•

Scheduler map—A scheduler map is referenced by r

c control

r

s to

n queues. The

scheduler map establishes the queues that comprise a scheduler node and associates a forwarding

class with a scheduler. See also Scheduler.

•

Stacked VLAN—An

nc

s

n on an S-VLAN with an outer tag corresponding to the S-VLAN, and

an inner tag corresponding to the C-VLAN. See also Service VLAN and Customer VLAN.
• Service VLAN (S-VLAN)—An S-VLAN,				n	by IEEE 802.1ad,	ft n corresponds to a network
r	n device such as a DSLAM. Scheduling and shaping is					ft n established for an S-VLAN to
provide CoS for downstream devices with					b r n and simple schedulers. See also Customer
VLAN.
• r	c control r	—	n s the c r c	r s	cs of a scheduler node. r c control r		s are

used at several levels of the CLI, including the physical interface, interface set, and logical interface

9

levels. Scheduling and queuing c r c r s				cs can be	n for the scheduler node using the
shaping-rate, guaranteed-rate, and			y b	r r	statements. Queues over these scheduler
nodes are	n by referencing a scheduler map. See also Scheduler and Scheduler map.
• VLAN—Virtual LAN,		n on an Ethernet logical interface.
Scheduler Node-Level		s n	ns in Hierarchical Scheduling

Scheduler hierarchies are composed of nodes and queues. Queues terminate the hierarchy. Nodes can be either root nodes, leaf nodes, or internal (non-leaf) nodes. Internal nodes are nodes that have other nodes as “children” in the hierarchy.

Scheduler hierarchies consist of levels, s r n with Level 1 at the physical port. This chapter establishes a four-level scheduler hierarchy which, when fully c n r consists of the physical interface (Level 1), the interface set (Level 2), one or more logical interfaces (Level 3), and one or more queues (Level 4).

NOTE: Beginning with Junos OS Release 16.1, certain MPCs on MX Series devices support up to v levels of scheduler hierarchies. The concepts presented in this topic apply similarly to v

scheduler hierarchy levels.

Table 2 on page 9 describes the possible c mb n

ns of scheduler nodes and their corresponding

node level

s

n

ns for a hierarchical queuing MIC or MPC.

Table 2: Node Levels

s n

ns in Hierarchical Scheduling

Scheduler C

n

r

n for

Hierarchical CoS Scheduler Nodes

Hierarchical CoS

Root Node

Internal (Non-Leaf) Nodes

Leaf Node

Level 1

Level 2

Level 3

Level 4

One or more

r

c control

Physical interf

—

One or more

One or more

r

s c

n

r

on logical

ace

logical interfac

queues

interfaces, but no interface-sets

es

c n

r

10

Table 2: Node Levels

s n

ns in Hierarchical Scheduling (C

n

n

)

Scheduler C n

r

n for

Hierarchical CoS Scheduler Nodes

Hierarchical CoS

Root Node

Internal (Non-Leaf) Nodes

Leaf Node

Level 1

Level 2

Level 3

Level 4

Interface-sets (c

c

ns of

Physical interf

—

Interface-set

One or more

logical interfaces) c n

r

but

ace

queues

no r

c c

n r

r

s

c n

r

on logical interfaces

Fully c

n

r

scheduler nodes

Physical interf

Interface-set

One or more

One or more

ace

logical interfac

queues

es

The table illustrates how the c

n

r n of an interface set or logical interface

c s the terminology

of hierarchical scheduler nodes. For example, suppose you c n

r

an interface-set statement with

logical interfaces (such as unit 0 and unit 2) and a queue. In this case, the interface-set is an internal

node at Level 2 of the scheduler node hierarchy. However, if there are no

r c control

r

s

c

to logical interfaces, then the interface set is at Level 3 of the hierarchy.

Hierarchical Scheduling at Non-Leaf Nodes

Whereas standard CoS scheduling is based on the scheduling and queuing c r c r s cs of a router’s egress ports and their queues, hierarchical CoS scheduling is based on the scheduling and queuing

c r c r s cs that span a hierarchy of scheduler nodes over a port. The hierarchy begins at Level 1, a root node at the physical interface (port) level of the CLI hierarchy and terminates at Level 4, a leaf node at the queue level. Between the root and leaf nodes of any scheduler hierarchy are one or more internal nodes, which are non-root nodes that have other nodes as “children” in the hierarchy.

Whereas you c n	r	standard CoS scheduling by applying a scheduler map to each egress port to
specify a forwarding class and a queue priority level, you c n					r hierarchical CoS scheduling with
n parameters. To c n				r hierarchical CoS scheduling, you apply a scheduler map to the queue
level (Level 4) of a scheduler hierarchy, and you can apply a					r n r c control r	at each of the
other levels. A r	c control		r	s c s not only a scheduler map (forwarding class and queue
priority level) but also		n	shaping rate (PIR), guaranteed transmit rate (CIR), burst rate, delay b				r
rate, and drop r

11

Release History Table

Release scr n

16.1	Beginning with Junos OS Release 16.1, certain MPCs on MX Series devices support up to v levels of
	scheduler hierarchies.

Priority r	n in Hierarchical Scheduling
Priority r	n is performed for MX Series router output Interfaces on Enhanced Queuing DPCs,

MICs, and MPCs, and for M Series and T Series router output interfaces on IQ2E PICs. Priority

rn is useful for mixed r c environments when, for example, you want to make sure that the

voice r c of one customer does not s r due to the data r c of another customer. Nodes and queues are serviced in the order of their priority. The default priority of a queue is low, and you can

explicitly c		n	r a queue priority by including the priority statement at the [edit class-of-service
schedulers scheduler-name] hierarchy level.
You cannot directly c n				r	the r	r	s of all hierarchical scheduling elements. The r r s of
internal nodes, for example, are determined as follows:
• The highest priority of an					c v child, that is, a child currently containing r c (Interface sets only
take the highest priority of their						c v	children.)
• Whether the node is above its c						n	r guaranteed rate (CIR) or not (this is only relevant if the
physical interface is in CIR mode).
Each queue has a c n				r	priority and a hardware priority. The usual mapping between the
c n	r	priority and the hardware priority is shown in Table 3 on page 11.
Table 3: Queue Priority
C n	r	Priority						Hardware Priority
Strict-high								0
High								0
Medium-high								1

12

Table 3: Queue Priority (C n	n	)
C n r Priority			Hardware Priority
Medium-low			1
Low			2
MPCs also have c n r b	CLI	r r s of excess-priority high, excess-priority medium-high,
excess-priority medium-low, and excess-priority low. These r r s only take				c	above the
guaranteed rate.
In CIR mode, the priority for each internal node depends on whether the highest				c v	child node is

above or below the guaranteed rate. The mapping between the highest c v child’s priority and the hardware priority below and above the guaranteed rate is shown in Table 4 on page 12.

Table 4: Internal Node Queue Priority for CIR Mode

C	n	r Priority of Highest	Hardware Priority Below	Hardware Priority Above
c	v	Child Node	Guaranteed Rate	Guaranteed Rate
Strict-high			0	0
High			0	3
Medium-high			1	3
Medium-low			1	3
Low			2	3
Excess-priority high*			N/A	3
Excess-priority medium-high*			N/A	3

13

Table 4: Internal Node Queue Priority for CIR Mode (C n n				)
C	n	r Priority of Highest	Hardware Priority Below		Hardware Priority Above
c	v	Child Node	Guaranteed Rate		Guaranteed Rate
Excess-priority medium-low*			N/A		4
Excess-priority low*			N/A		4

* MPCs only

In PIR-only mode, nodes cannot send if they are above the c					n	r shaping rate. The mapping
between the c n			r priority and the hardware priority is for PIR-only mode is shown in Table 5 on
page 13.
Table 5: Internal Node Queue Priority for PIR-Only Mode
C n	r	Priority		Hardware Priority
Strict-high				0
High				0
Medium-high				1
Medium-low				1
Low				2
A physical interface with hierarchical schedulers c n				r is shown in Figure 2 on page 14. The
c n	r	r r	s are shown for each queue at the top of the			r The hardware r r s for each
node are shown in parentheses. Each node also shows any c					n	r shaping rate (PIR) or guaranteed

rate (CIR) and whether or not the queues is above or below the CIR. The nodes are shown in one of

14

three states: above the CIR (clear), below the CIR (dark), or in a c n	n where the CIR does not m	r
(gray).
Figure 2: Hierarchical Schedulers and r r s

In the r the strict-high queue for customer VLAN 0 (cvlan 0) receives service rs even though the customer VLAN is above the c n r CIR (see Table 4 on page 12 for the reason: strict-high always has hardware priority 0 regardless of CIR state). Once that queue has been drained, and the priority of the node has become 3 instead of 0 (due to the lack of strict-high r c) the system moves on to the medium queues next (cvlan 1 and cvlan 3), draining them in a round robin fashion (empty queue lose their hardware priority). The low queue on cvlan 4 (priority 2) is sent next, because that mode is below the CIR. Then the high queues on cvlan 0 and cvlan2 (both now with priority 3) are drained in a round robin fashion, and n y the low queue on cvlan 0 is drained (thanks to svlan 0 having a priority of 3).

RELATED DOCUMENTATION

CoS on Enhanced IQ2 PICs Overview

Enhanced Queuing DPC CoS r r s

CoS Features and m ns on MIC and MPC Interfaces

Understanding Hierarchical Scheduling for MIC and MPC Interfaces

15

C n r n Hierarchical Schedulers for CoS

In metro Ethernet environments, a virtual LAN (VLAN) typically corresponds to a customer premises

equipment (CPE) device and the VLANs are n		by an inner VLAN tag on Ethernet frames (called
the customer VLAN, or C-VLAN, tag). A set of VLANs can be grouped at the DSL access m			x r
(DSLAM) and n	by using the same outer VLAN tag (called the service VLAN, or S-VLAN, tag).
The service VLANs are typically gathered at the Broadband Remote Access Server (B-RAS)

level.Hierarchical schedulers let you provide shaping and scheduling at the service VLAN level as well as other levels, such as the physical interface. In other words, you can group a set of logical interfaces and then apply scheduling and shaping parameters to the logical interface set as well as to other levels.

On Juniper Networks MX Series 5G Universal R	n	rms and systems with Enhanced IQ2 (IQ2E)
PICs, you can apply CoS shaping and scheduling at one of four			r n levels, including the VLAN set

level. You can only use this c n r n on MX Series routers or IQ2E PICs. Beginning with Junos OS Release 16.1, certain MPCs support up to v levels of scheduler hierarchies.

The supported scheduler hierarchy is as follows:

•The physical interface (level 1)

•The service VLAN (level 2 is unique to MX Series routers)

•The logical interface or customer VLAN (level 3)

•The queue (level 4)

Users can specify a r			c control	r	(	r c c n r	r	that can specify a shaping rate, a
guaranteed rate, and a scheduler map with transmit rate and b							r delay. The scheduler map contains
the mapping of queues (forwarding classes) to their r s c v							schedulers (schedulers			n the
r	r	s for the queue). Queue		r	r	s can specify a transmit rate and b			r management
parameters such as b			r size and drop			r
To c	n	r CoS hierarchical scheduling, you must enable hierarchical scheduling by including the
hierarchical-scheduler statement at the physical interface.

RELATED DOCUMENTATION

Understanding Hierarchical Scheduling

Understanding Hierarchical Scheduling for MIC and MPC Interfaces

CoS on Enhanced IQ2 PICs Overview

Understanding Hierarchical CoS for Subscriber Interfaces | 87