Per Hop Behavior | Juniper Networks EX2500 manual

Chapter 5: Quality of Service

Per Hop Behavior

The DSCP value determines the Per Hop Behavior (PHB) of each packet. The PHB is the forwarding treatment given to packets at each hop. QoS policies are built by the application of a set of rules to packets, based on the DSCP value, as they hop through the network.

The default settings are based on the following standard PHBs, as defined in the

IEEE standards:

Expedited Forwarding (EF)—This PHB has the highest egress priority and lowest drop precedence level. EF traffic is forwarded ahead of all other traffic. EF PHB is described in RFC 2598.

Assured Forwarding (AF)—This PHB contains four service levels, each with a different drop precedence, as shown in Table 14. Routers use drop precedence to determine which packets to discard last when the network becomes congested. AF PHB is described in RFC 2597.

Table 14: Assured Forwarding

Drop
Precedence	Class 1	Class 2	Class 3	Class 4

Low	AF11 (DSCP 10)	AF21 (DSCP 18)	AF31 (DSCP 26)	AF41 (DSCP 34)

Medium	AF12 (DSCP 12)	AF22 (DSCP 20)	AF32 (DSCP 28)	AF42 (DSCP 36)

High	AF13 (DSCP 14)	AF23 (DSCP 22)	AF33 (DSCP 30)	AF43 (DSCP 38)

Class Selector (CS)—This PHB has eight priority classes, with CS7 representing the highest priority, and CS0 representing the lowest priority, as shown in Table 15. CS PHB is described in RFC 2474.

Table 15: Class Selector

	Class
Priority	Selector	DSCP

Highest	CS7	56

	CS6	48

	CS5	40

	CS4	32

	CS3	24

	CS2	16

	CS1	8

Lowest	CS0	0

Using DSCP Values to Provide QoS 61

Image 75

Juniper Networks EX2500 manual Per Hop Behavior, Assured Forwarding Drop Precedence Class

Contents

North Mathilda Avenue Sunnyvale, CA Configuration Guide Ii „ Table of Contents Chapter VLANs Rmon Overview Rmon Group 1-Statistics Rmon Group 2-History Chapter Ports and Trunking Port Mirroring Overview Configuring Port Mirroring AppendixesIndexes Port-Based Vlan Assignment Default Vlan SettingsPage List of Tables EX2500 Ethernet Switch Configuration Guide „ List of Tables Supported Platforms About This GuideObjectives Audience Icon Meaning Description Documentation Conventions List of Technical Publications Documentation FeedbackRequesting Technical Support Opening a Case with Jtac Self-Help Online Tools and Resources EX2500 Ethernet Switch Applications Page Configuring the Management Interface Accessing the Switch Configure the default gateway. Enable the gateway Dynamic Host Configuration Protocol Using the EX2500 Web Device Manager Using Telnet Configuring EX2500 Web Device Manager Access via Https Configuring EX2500 Web Device Manager Access via Http SNMPv1, SNMPv2 Using Snmp Default Configuration User ConfigurationSNMPv3 Configure an entry in the notify table Configuring Snmp Trap HostsSNMPv1 Trap Host Configuration SNMPv2 Trap Host Configuration SNMPv3 Trap Host Configuration Securing Access to the Switch Configure the Radius secret Radius Authentication and AuthorizationHow Radius Authentication Works Configuring Radius on the Switch Radius Authentication Features in the EX2500 Switch Radius Attributes for EX2500 User Privileges Switch User Accounts TACACS+ Authentication How TACACS+ Authentication WorksTACACS+ Authentication Features in the EX2500 Switch „ starttime „ stoptime „ elapsedtime „ disccause Command Authorization and Logging Configuring TACACS+ Authentication on the SwitchConfigure the TACACS+ secret and second secret SSH Encryption of Management Messages Configuring SSH Features on the SwitchGenerating RSA Host and Server Keys for SSH Access Secure Shell SSH Integration with Radius and TACACS+ Authentication End User Access Control User Access Control Considerations for Configuring End User Accounts Logging In to an End User Account Listing Current Users Vlan Overview VLANs Pvid Numbers „ Port configurationVLANs and Port Vlan ID Numbers Vlan Numbers Vlan Tagging Illustrates the default Vlan settings on the switch Default Vlan Settings Port-Based Vlan Assignment Vlan Topologies and Design Considerations Vlan Configuration Rules Multiple VLANs example in is described in Table Multiple VLANs Configuration Example Enable tagging on uplink ports that support multiple VLANs Private Vlan Ports Private VLANs Verify the configuration Private Vlan Configuration GuidelinesPrivate Vlan Configuration Example Configure a secondary Vlan and map it to the primary Vlan Spanning Tree Overview Spanning Tree Protocol Bridge Protocol Data Units BPDUs Determining the Path for Forwarding BPDUsBridge Priority Port Path Cost Spanning Tree Group Configuration GuidelinesChanging the Spanning Tree Mode Port Priority Creating a Vlan Rules for Vlan Tagged PortsAdding and Removing Ports from STGs Port State Changes Rapid Spanning Tree Protocol Edge Port Rstp Configuration GuidelinesRstp Configuration Example Port Type and Link Type Default Spanning Tree Configuration Why Do We Need Multiple Spanning Trees?Per Vlan Rapid Spanning Tree Configuring Pvrst Pvrst Configuration Guidelines Common Internal Spanning Tree Mstp Configuration GuidelinesMultiple Spanning Tree Protocol Mstp Region Implementing Multiple Spanning Tree Groups Multiple Spanning Tree Groups Configuration Example Vlan Fast Uplink Convergence Configuring Fast Uplink Convergence Configuration Guidelines Ports and Trunking Trunking OverviewStatistical Load Distribution Built-In Fault Tolerance Before Configuring Static TrunksTrunk Group Configuration Rules Port Trunk Group Configuration Example Port Trunking Configuration Example Follow these steps on the EX2500 switch Define a trunk group „ Destination IP DIP Configurable Trunk Hash AlgorithmLink Aggregation Control Protocol „ Destination MAC Dmac 48 „ Link Aggregation Control Protocol Set the Lacp mode Lacp Configuration GuidelinesConfiguring Lacp Optionally Reducing Lacp Timeout Ex2500config-if# lacp timeout short ex2500config-if# exit QoS Overview Quality of Service COS Using ACL Filters To delete an IP Standard ACL MAC Extended ACLsIP Standard ACLs To delete a MAC Extended ACL To delete an IP Extended ACL IP Extended ACLs TCP/UDP Understanding ACL Priority ACL Example 1-Blocking Traffic to a Host ACL Configuration ExamplesAssigning ACLs to a Port Viewing ACL Statistics Add the ACL to a port ACL Example 3-Blocking Http Traffic Assign the ACLs to a port ACL Example 4-Blocking All Except Certain Packets Using Storm Control Filters Configuring Storm ControlBroadcast Storms Differentiated Services Concepts Using Dscp Values to Provide QoS Assured Forwarding Drop Precedence Class Per Hop Behavior Use the following command to perform Dscp mapping QoS LevelsDscp Mapping Shows the priority bits in a VLAN-tagged packet Using 802.1p Priority to Provide QoS Queuing and Scheduling Rmon Overview Remote Monitoring Rmon Group 1-Statistics Configure the Rmon statistics on a port Rmon Group 2-History Configuring Rmon HistoryConfigure the Rmon History parameters for a port This configuration enables Rmon History collection on port Configure the Rmon Alarm parameters to track Icmp messages Rmon Group 3-AlarmsAlarm MIB Objects Configuring Rmon Alarms Rmon Group 9-Events Ex2500config# rmon event 110 type log-onlyPage Igmp Snooping Igmp FastLeave IGMPv3 Snooping Igmp Snooping Configuration Example Ex2500# show ip igmp groups Static Multicast Router High Availability Overview High Availability Through Uplink Failure Detection Failure Detection Pair Spanning Tree Protocol with UFD UFD Configuration Guidelines Monitoring UFD UFD Configuration ExamplePage Appendixes EX2500 Ethernet Switch Configuration Guide 80 „ Appendixes Port Mirroring Overview „ Port Mirroring Overview on „ Configuring Port Mirroring on Configuring Port Mirroring „ Index on Indexes EX2500 Ethernet Switch Configuration Guide 84 „ Indexes Numerics Index Internet Group Management Protocol. See Igmp Management interface, configuringMulti-links between switches, port trunking Physical. See switch ports Segmentation. See IP subnets Segments. See IP subnets Quality of Service. See QoSQoS Security Example showing multiple VLANs Virtual Local Area Networks. See VLANs