09- Junos CoS

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JUNOS QoS

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• What JUNOS QoS supports

– Classifiers– Forwarding classes & Loss Priority– Scheduling and Queues – Rewriting– Dropping– Fabric Scheduler

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Components of JUNOS QoS

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JUNOS CoS applications supports• Differentiated Services

– DiffServ as well as six-bit IPv4 and IPv6 header ToS byte settings. DiffServ code points (DSCPs) in the IP and IPv6 ToS fields used to determine the forwarding class of a packet.

• Layer 2 to Layer 3 CoS mapping– Mapping of Layer 2 (IEEE 802.1p) packet headers to routing platform

forwarding class and loss-priority values.– Layer 2 to Layer 3 CoS mapping involves setting the forwarding class and loss

priority based on information in the Layer 2 header. Output involves mapping the forwarding class and loss priority to a Layer 2-specific marking. You can mark the Layer 2 and Layer 3 headers simultaneously.

• MPLS EXP– Mapping of MPLS experimental (EXP) bit settings to routing platform

forwarding classes and vice versa.• VPN outer-label marking

– Setting of outer-label EXP bits, also known as CoS bits, based on MPLS EXP mapping.

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Classifiers

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Classifiers • Associate incoming packets with a forwarding class and

loss priority and, based on the associated forwarding class, assign packets to output queues.– Behavior aggregate (BA) or code point traffic classifiers

• Code points determine each packet’s forwarding class and loss priority. BA classifiers allow you to set the forwarding class and loss priority of a packet based on DiffServ code point (DSCP) bits, DSCP IPv6, IP precedence bits, MPLS EXP bits, and IEEE 802.1p bits. The default classifier is based on IP precedence bits.

– Multifield (MF) traffic classifiers• Allow you to set the forwarding class and loss priority of a packet

based on firewall filter rules.

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BA Classifier• Allows you to set FC and PLP:

– For incoming IPv4 and IPv6 packets, based on the value of the entire 6-bit DSCP field.

– For incoming MPLS packets, based on the value of the MPLS EXP field.

– For incoming Ethernet packets, based on the value of the 802.1p bits.

– For incoming ATM traffic, the ATM2 PIC can be configured to set the assembled packet notification’s PLP-bit based on the ATM cell loss priority (CLP) bit.

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Classification Defaults• Default “no-config” classification:

• Only “ipprec-compatibility” classification table is active– 000-101 go to queue0, plp=least significant bit– 110-111 go to queue3, plp=least significant bit

• All other unclassified packets are placed in queue0– Incoming MPLS packets are placed in output queue 0– Incoming IEEE 802.1p is ignored

8Copyright © 2004 Juniper Networks, Inc. Proprietary and Confidential www.juniper.net

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BA Classifier Configuration

1. Create a dscp, exp, ieee-802.1p or ipprecedence classifier:

[edit]class-of-service {

classifiers {[dscp | exp | ieee-802.1 | inet-precedence] classifier-name {

import [classifier-name | default];forwarding-class class-name {

loss-priority [low | high] code-points [alias | bits];

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>>BA Classifier Configuration

2. Bind the classifier to an incoming logical interface:[edit]

class-of-service {interfaces {

interface-name {unit unit-number {classifiers {

[dscp | exp | ieee-802.1 | inet-precedence] [classifier-name | default];

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MF Classifier

• Allows to use an arbitrary input firewall filter to set the FC and/or PLP fields in the packet notification.

• Working for incoming and outgoing packets• MF-classifier overrides BA-classifier if conflict• MF filters are applied per-logical interface and

the number of MF classifiers that can be configured on an interface is virtually unlimited, since it is solely bounded by memory.

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MF classifier example # 1

• Map all traffic coming into an interface to a particular forwarding-class (queue#)[edit]class-of-service {

interfaces {interface-name {

unit unit-number {forwarding-class class-name;

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MF classifier example # 2

• Map destination IP addresses to specific forwarding classes

1.Define a policy class to override the default packet classification.


forwarding-policy {class class-name {classification-override {

forwarding-class fc-class-name;

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>>MF classifier example # 2

2. Create a policy to identify the IP addresses to which the policy class should be applied.

[edit]policy-options {

policy-statement policy-name { term term-name {

from route-filter destination-prefix match-type;then class class-name;

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>>MF classifier example # 23. Export the policy to the forwarding

table.[edit]routing-options {

forwarding-table {export policy-name

• Note: – this essentially “tags” the matching forwarding table entries

with a queue#, so that packets forwarded using those entries getplaced into the specified queue.

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MF classifier example # 3Configuring classification based on a firewall filter:

1. Define the firewall filter:[edit]firewall {

filter foo { term term-1 {

from {match-conditions; (see previous slide)

}then {

forwarding-class class-name; loss-priority [low|high];accept;

term default {then accept;

}

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>>MF classifier example # 32. Apply the firewall filter to an interface:

[edit]interfaces interface-name {

unit logical-unit-number { family inet {

filter {input foo;

• Notes: – Can only apply 1 input and/or output firewall filter to an interface

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Forwarding Classes

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Forwarding Classes: ordered aggregates• Affect the forwarding, scheduling, and marking

policies applied to packets as they transit a routing platform. The forwarding class plus the loss priority define the per-hop behavior. – Best effort,– Assured forwarding, – Expedited forwarding,– Network control.

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Forwarding Classes: ordered aggregates

• M-series, except M320, routing platforms, – four forwarding classes are supported;

• M320 and T-series platforms, – eight forwarding classes are supported,

• For example, multiple classes of EF traffic: EF, EF1, and EF2.

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Loss Priority• Internal mechanism.• Typically mark packets exceeding some service

level with a high loss priority. • Loss priority affects the scheduling of a packet

without affecting the packet’s relative ordering. • Loss priority is set by configuring a classifier or a

policer.

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Scheduling and rate Control

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Transmission Scheduling and rate controlManages traffic flows:• Schedulers

– Define the priority, bandwidth, delay buffer size, rate control status, and RED drop profiles to be applied to a particular forwarding class for packet transmission.

• Fabric schedulers– For M320 and T-series platforms only, fabric schedulers allow you to

identify a packet as high or low priority based on its forwarding class, and to associate schedulers with the fabric priorities.

• Policers for traffic classes– limits traffic of a certain class to a specified bandwidth and burst size.

Packets exceeding the policer limits can be discarded, or can be assigned to a different forwarding class or to a different loss priority, or to both. You define policers with filters that can be associated with input or output interfaces.

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Output Queue Scheduling, • Each FC has three parameters:

– The buffer-size:• Maximum queue length as a % of the output interface’s total buffer capacity

or a temporal value from 1 to 200,000 ms. Define maximum buffer delay. – The transmit-rate:

• Bandwidth allocated to a FC. Each FC is assigned transmission bandwidth credits by the DWRR scheduler every 200 microseconds, based on the configured transmit-rate. The transmission bandwidth assigned to each queue can be rate limited to the exact value specified, or it can exceed the configured rate and borrow surplus bandwidth if it is unused by other FCs. This is basically traffic shaping per queue.

– The priority:• identifies the scheduling priority assigned to the FC. The scheduling priority

can be configured as low, high, or strictly-high. – High-priority FCs are allowed to transmit packets ahead of low-priority

FCs as long as the high-priority FC retains enough bandwidth credits. – A Strictly-high priority FC has precedence over all other FCs as long as

there is strictly-high priority traffic waiting to be sent.

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Queues: Define forwarding-classes• Queue numbers are now abstracted to

“forwarding-classes”• Default Forwarding-classes:

• be -> queue0• ef -> queue1• af -> queue2• nc -> queue3

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Queues: Define forwarding-classes• Assign forwarding-classes to queues:


forwarding-classes {queue queue-number class-name;queue queue-number class-name;queue queue-number class-name;queue queue-number class-name;

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Queues: Size

• Large queues may increase latency during congestion

• smaller queues may be more appropriate for delay sensitive traffic

• The default configuration has queue 0 with 95% of queue memory and queue 3 with 5%

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Queues: Size Configuration• Queue size configuration:


schedulers {scheduler-name {

buffer-size [temporal|percent percentage|remainder];

– Bind the scheduler to a queue and interface– Can specify queue size in time for time-sensitive traffic

{master}[edit class-of-service]juniper@t640_RE0# set schedulers test buffer-size temporal 8000

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Queues: Transmit Rate• Determines the actual traffic bandwidth

– Rate is specified in bits per second• Limit the transmission bandwidth to the exact value • Allow it to exceed the configured rate if additional bandwidth

is available from other queues.– Also referred to as WRR%

• The default configuration has queue 0 with 95% of queue bandwith and queue 3 with 5%

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Queues: Transmit Rate• Transmit rate configuration:



transmit-rate [rate | percent percentage | remainder] <exact>;

– Bind the scheduler to a queue and interface

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Queues: Priority

• Determines the order in which an output interface transmits traffic from the queues

• JUNOS supports:– Low priority, – Medium-low priority, – Medium-high priority, – High priority, – Strict-high priority

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Queues: Priority• The order by which the DWRR queue-

scheduling algorithm services queues is: – High priority with positive credit– Medium High priority with positive credit– Medium Low priority with positive credit– Low priority with positive credit – High priority with negative credit – Medium High priority with negative credit– Medium Low priority with negative credit– Low priority with negative credit.

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Combination of PQ and DWRR• M-series and T-series platforms can have max one

queue per interface with strict-high priority, which works the same as high priority, but provides unlimited transmission bandwidth.

• As long as the queue with strict-high priority has traffic to send, it receives precedence over all other queues, except queues with high priority.

• Queues with strict-high and high priority take turns transmitting packets until the strict-high queue is empty, the high priority queues are empty, or the high priority queues run out of bandwidth credit. Only when these conditions are met can lower priority queues send traffic.

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Combination of PQ and DWRR• If you do configure a transmission rate on a strict-high

priority queue, it does not affect the WRR operation. The transmission rate only serves as a placeholder in the output of commands such as the show interface queue command.

• Strict-high priority queues might starve low priority queues. The high priority allows you to protect traffic classes from being starved by traffic in a strict-high queue.

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Queues: Priority Configuration



priority priority-level;

– Bind the scheduler to a queue and interface• Default “no-config” settings:

– All queues are low priority

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Congestion Management1. Configure the RED profiles:


drop-profiles {profile-name {

fill-level percentage1 drop-probability probability1;fill-level percentage2 drop-probability probability2;

… up to 64 times, ORinterpolate {

drop-probability [ p1 p2 p3 p4 p5 …];fill-level [ f1 f2 f3 f4 f5 …] ;

– “fill-level” creates a series of steps– “interpolate” creates a series of line segments from (0,0) to (f1,p1), then

(f1,p1) to (f2,p2), then (f2,p2) to (f3,p3), etc.

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Congestion Management2. map the drop-profile to a scheduler:



drop-profile-map loss-priority [low|high] protocol [non-tcp|tcp|any] drop-profile profile-name;

– Bind the scheduler to a queue and interface• Default “no-config” settings:

– 100% drop probability at 100% full (drop from head of queue)

– 0% drop probability for other levels of fullness

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Scheduling Configuration1. Configure schedulers;



transmit-rate [rate|percent percentage|remainder] <exact>; WRR configbuffer-size [milliseconds|percent percentage|remainder]; queue size configpriority [low|high]; queue priority config

drop-profile-map loss-priority [low|high] protocol [non-tcp|tcp|any] drop-profile profile-name; RED profile assignment

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>> Scheduling Configuration2. Assign schedulers to a scheduler-map:


scheduler-maps {map-name {

forwarding-class class-name1 scheduler scheduler-name1;forwarding-class class-name2 scheduler scheduler-name2;forwarding-class class-name3 scheduler scheduler-name3;forwarding-class class-name4 scheduler scheduler-name4;

3. Bind the scheduler map to a physical interface:[edit]class-of-service {


scheduler-map map-name;

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Scheduling in Summary• Default “no-config” settings:

– WRR%:• Queue0 gets 95%• Queue3 gets 5%

– Queue size:• Queue0 gets 95% of buffer space• Queue3 gets 5% of buffer space

– Priority:• Low

– RED: • 100+% full then drop, otherwise don’t

• Note: A queue’s WRR% and queue size % should be kept similar in value

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DWWR Example• Queue 3 is asigned HP,

– control traffic, – 5% of the interface’s buffer capacity,– 5% of the interface’s bandwidth, – Can borrow surplus bandwidth from other queues if it is available.

• Queue 2 is assigned a HP, gold traffic, – 20% of the interface’s buffer capacity, – 45% of the interface’s bandwidth, – Can borrow surplus bandwidth from other queues if it is available.

• Queue 1 is assigned a LP, silver traffic, – 30% of the interface’s buffer capacity, – 30% of the interface’s bandwidth – Can borrow surplus bandwidth from other queues if it is available.

• Queue 0 is assigned a LP, best-effort traffic, – 50% of the interface’s buffer capacity, – 20% of the interface’s bandwidth, – Can borrow surplus bandwidth from other queues even if it is available.

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DWRR Example

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Combination of PQ and DWRR • Queue 3 strictly-high priority, latency and jitter-sensitive voice traffic,

– 5% of the interface’s buffer capacity, – Can borrow surplus bandwidth from other queues if it is available. – BW has no meaning

• Queue 2 Low priority, gold traffic, – 30% of the interface’s buffer capacity, – 30% of the interface’s bandwidth, – Can borrow surplus bandwidth from other queues if it is available.

• Queue 1 low priority, silver traffic, – 30% of the interface’s buffer capacity, – 30% of the interface’s bandwidth,– Can borrow surplus bandwidth from other queues if it is available.

• Queue 0 low priority, best-effort traffic,– 35% of the interface’s buffer capacity, – 20% of the interface’s bandwidth, – Can borrow surplus bandwidth from other queues even if it is available.

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Combination of PQ and DWRR

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Rewrite

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Rewrite Markers

• Rewrite markers– Redefines the code-point value of outgoing packets.

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Rewriting Configuration1. Configure rewrite-rule;


schedulers {rewrite-rules {

dscp|exp|ieee-802.1|inet-precedence <table-name> {import [<table-name>|default]; (default=“exp-default”)forwarding-class <class-name1> {

loss-priority [low|high] code-point [<alias>|bits];}forwarding-class <class_name2> {

loss-priority [low|high] code-point [<alias>|bits];}forwarding-class <class-name3> {

loss-priority [low|high] code-point [<alias>|bits];}forwarding-class <class_name4> {

loss-priority [low|high] code-point [<alias>|bits];}

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>>Rewriting Configuration2. Apply rewrite-rule to outgoing logical interface;



unit <unit-number> {rewrite-rules [dscp|exp|ieee-802.1|inet-precedence] [rewrite-name |default] ;

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Rewriting Configuration, MPLS[edit]

protocols {mpls {

label-switched-path lsp-name { (user defined name)class-of-service value; (0-7)

• ALL traffic forwarded down the LSP will have EXP=value

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Rewriting Classification

• No-config Default: “exp-default” rewrite-rule active on all interfaces:

Rewrite rule: Rewrite rule: expexp--defaultdefault, Code point type: exp, Index: 2, Code point type: exp, Index: 2

Forwarding class Loss priority Code pForwarding class Loss priority Code pointoint

bestbest--effort low effort low 000 000

bestbest--effort high effort high 001001

expeditedexpedited--forwarding low 010 forwarding low 010

expeditedexpedited--forwarding high forwarding high 011 011

assuredassured--forwarding low 100 forwarding low 100

assuredassured--forwarding high 101 forwarding high 101

networknetwork--control low 110 control low 110

networknetwork--control high 111 control high 111

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Default “no-config” Summary• Classification: only “ipprec-compatibility” classifier is active• Queue Properties: (size, RED, scheduling)

– WRR%:• Queue0 gets 95%• Queue3 gets 5%

– Queue size:• Queue0 gets 95% of notification memory space• Queue3 gets 5% of notification memory space

– Priority:• Low

– RED: • 100% full then drop with 100% probability, otherwise don’t

• Rewriting: only “exp-default” rewrite-rule is active

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Drop profile

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Drop Profiles

• E-FPC can have 16 unique drop profiles, vs 32 in T sereis. Each queue has four pointers into this global pool of drop profiles

• One pointer for permutations of the TCP and PLP bits {(TCP=0, PLP=0), (0,1), (1,0), and (1,1)} for packets placed in the given queue.

• Pointers identifies the WRED drop profile in the global pool.

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Queues: Drop Profile

• Defines the drop probabilities across the range of delay-buffer occupancy, thereby supporting the RED process

• For each scheduler, you can configure four separate drop profiles, one for each combination of loss priority (low or high) and IP transport protocol (TCP/IP or non-TCP/IP)– Maximum of 32 different drop profiles

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Queues: Drop Profiles• Drop profile configuration:



drop-profile-map loss-priority [any | high | medium | low] protocol [any | non-tcp | tcp] drop-profile profile-name;

• Then bind the scheduler to a queue and interface

• Default “no-config” settings:– 100+% full then drop, otherwise don’t

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Mapping queued packets to WRED profile

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T & M320 Switch Fabric Scheduler • Separate queues on the ingress PFE facing the fabric.

• Separate paths through the fabric for high and low priority cells. This means that a low priority cell never blocks a high priority cell.

• Default behavior is fabric priority queuing on egress interfaces to match the scheduling priority you assign. High-priority egress traffic is automatically assigned to high-priority fabric queues. Likewise, low-priority egress traffic is automatically assigned to low-priority fabric queues.

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Thank You

Documents

09- Junos CoS