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Using DSCP values to provide QoS, Differentiated Services concepts, Per Hop Behavior

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Using DSCP values to provide QoS The six most significant bits in the TOS byte of the IP header are defined as DiffServ Code Points (DSCP). Packets are marked with a certain value depending on the type of treatment the packet must receive in the network device. DSCP is a measure of the Quality of Service (QoS) level of the packet. Differentiated Services concepts To differentiate between traffic flows, packets can be classified by their DSCP value. The Differentiated Services (DS) field in the IP header is an octet, and the first six bits, called the DS Code Point (DSCP), can provide QoS functions. Each packet carries its own QoS state in the DSCP. There are 64 possible DSCP values (0-63). Figure 12 Layer 3 IPv4 packet The GbE2c can perform the following actions to the DSCP: • Read the DSCP value of ingress packets • Re-mark the DSCP value to a new value • Map the DSCP value to an 802.1p priority Once the DSCP value is marked, the GbE2c can use it to direct traffic prioritization. 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 applying a set of rules to packets, based on the DSCP value, as they hop through the network. The GbE2c 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 below. Routers use drop precedence to determine which packets to discard last when the network becomes congested. AF PHB is described in RFC 2597. Table 18 Assured forwarding drop-down precedence Drop Precedence Class 1 Class 2 Class 3 Class 4 Low Medium High AF11 (DSCP 10) AF12 (DSCP 12) AF13 (DSCP 14) AF21 (DSCP 18) AF22 (DSCP 20) AF23 (DSCP 22) AF31 (DSCP 26) AF32 (DSCP 28) AF33 (DSCP 30) AF41 (DSCP 34) AF42 (DSCP 36) 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 below. CS PHB is described in RFC 2474. Table 19 Class selector priority classes Priority Class Selector DSCP Highest CS7 56 CS6 48 CS5 40 CS4 32 CS3 24 Quality of Service 80

Section	Page
HP GbE2c Ethernet Blade Switch for c-Class BladeSystem Application Guide	1
Notice	2
Contents	3
Accessing the switch	8
Introduction	8
Additional references	8
Typographical conventions	9
Management Network	9
Connecting through the console port	10
Connecting through Telnet	10
Connecting through Secure Shell	10
Using the command line interfaces	10
Configuring an IP interface	11
Using the Browser-based Interface	11
Using Simple Network Management Protocol	12
SNMP v1.0	12
SNMP v3.0	12
Default configuration	12
User configuration	13
View based configurations	14
CLI user equivalent	14
CLI oper equivalent	14
Configuring SNMP trap hosts	15
SNMPv1 trap host	15
SNMPv2 trap host configuration	16
SNMPv3 trap host configuration	16
Secure access to the switch	17
Setting allowable source IP address ranges	17
Configuring an IP address range for the management network	17
RADIUS authentication and authorization	18
How RADIUS authentication works	18
Configuring RADIUS on the switch (CLI example)	18
Configuring RADIUS on the switch (BBI example)	19
RADIUS authentication features	20
User accounts for RADIUS users	21
RADIUS attributes for user privileges	21
TACACS+ authentication	21
How TACACS+ authentication works	22
TACACS+ authentication features	22
Authorization	22
Accounting	23
Configuring TACACS+ authentication on the switch (CLI example)	23
Configuring TACACS+ authentication on the switch (BBI example)	24
Secure Shell and Secure Copy	25
Configuring SSH and SCP features (CLI example)	26
Using SSH and SCP client commands	27
SSH and SCP encryption of management messages	28
Generating RSA host and server keys for SSH access	28
SSH/SCP integration with RADIUS and TACACS+ authentication	28
User access control	29
Setting up user IDs	29
Ports and trunking	30
Introduction	30
Ports on the switch	30
Port trunk groups	31
Statistical load distribution	31
Built-in fault tolerance	31
Before you configure trunks	31
Trunk group configuration rules	31
Port trunking example	32
Configuring trunk groups (CLI example)	33
Configuring trunk groups (BBI example)	34
Configurable Trunk Hash algorithm	36
Link Aggregation Control Protocol	37
Configuring LACP	38
Port-based Network Access and traffic control	39
Port-based Network Access control	39
Extensible authentication protocol over LAN	39
802.1x authentication process	39
EAPoL Message Exchange	40
802.1x port states	41
Supported RADIUS attributes	41
EAPoL configuration guidelines	42
Port-based traffic control	42
Configuring port-based traffic control	42
VLANs	43
Introduction	43
Overview	43
VLANs and port VLAN ID numbers	43
VLAN numbers	43
Viewing VLANs	43
PVID numbers	43
Viewing and configuring PVIDs	44
Port information	44
Port configuration	44
VLAN tagging	44
VLANs and IP interfaces	47
VLAN topologies and design considerations	47
VLAN configuration rules	47
Multiple VLANS with tagging	47
Configuring the example network	49
Configuring ports and VLANs on Switch 1 (CLI example)	49
Configuring ports and VLANs on Switch 2 (CLI example)	50
Configuring ports and VLANs on Switch 1 (BBI example)	51
FDB static entries	54
Trunking support for FDB static entries	54
Configuring a static FDB entry	54
Spanning Tree Protocol	55
Introduction	55
Overview	55
Bridge Protocol Data Units	55
Determining the path for forwarding BPDUs	55
Bridge priority	55
Port priority	55
Port path cost	56
Spanning Tree Group configuration guidelines	56
Default Spanning Tree configuration	56
Adding a VLAN to a Spanning Tree Group	56
Creating a VLAN	56
Rules for VLAN tagged ports	56
Adding and removing ports from STGs	57
Assigning cost to ports and trunk groups	57
Multiple Spanning Trees	57
Why do we need Multiple Spanning Trees?	57
VLAN participation in Spanning Tree Groups	58
Configuring Multiple Spanning Tree Groups	58
Configuring Switch 1 (CLI example)	59
Configuring Switch 2 (CLI example)	59
Configuring Switch 1 (BBI example)	59
Port Fast Forwarding	60
Configuring Port Fast Forwarding	61
Fast Uplink Convergence	61
Configuration guidelines	61
Configuring Fast Uplink Convergence	61
RSTP and MSTP	62
Introduction	62
Rapid Spanning Tree Protocol	62
Port state changes	62
Port type and link type	62
Edge port	62
Link type	63
RSTP configuration guidelines	63
RSTP configuration example	63
Configuring Rapid Spanning Tree (CLI example)	63
Configuring Rapid Spanning Tree Protocol (BBI example)	63
Multiple Spanning Tree Protocol	65
MSTP region	65
Common Internal Spanning Tree	65
MSTP configuration guidelines	65
MSTP configuration example	65
Configuring Multiple Spanning Tree Protocol (CLI example)	65
Configuring Multiple Spanning Tree Protocol (BBI example)	66
Quality of Service	70
Introduction	70
Overview	70
Using ACL filters	71
Summary of packet classifiers	71
Summary of ACL actions	72
Understanding ACL precedence	72
Using ACL Groups	74
ACL Metering and Re-marking	74
Metering	74
Re-marking	75
Viewing ACL statistics	75
ACL configuration examples	75
Configure Access Control Lists (CLI example)	75
Configure Access Control Lists and Groups (BBI example 1)	76
Using DSCP values to provide QoS	80
Differentiated Services concepts	80
Per Hop Behavior	80
QoS levels	81
Using 802.1p priorities to provide QoS	81
802.1p configuration (CLI example)	82
802.1p configuration (BBI example)	83
Queuing and scheduling	86
Basic IP routing	87
IP routing benefits	87
Routing between IP subnets	87
Example of subnet routing	89
Using VLANs to segregate broadcast domains	91
Dynamic Host Configuration Protocol	92
DHCP relay agent	92
DHCP relay agent configuration	93
Routing Information Protocol	94
Distance vector protocol	94
Stability	94
Routing updates	94
RIPv1	94
RIPv2	94
RIPv2 in RIPv1 compatibility mode	95
RIP Features	95
Poison	95
Triggered updates	95
Multicast	95
Default	95
Metric	95
Authentication	95
RIP configuration example	96
IGMP Snooping	97
Introduction	97
Overview	97
FastLeave	97
IGMP Filtering	98
Configuring the range	98
Configuring the action	98
Static multicast router	98
IGMP Snooping configuration example	98
Configuring IGMP Snooping (CLI example)	98
Configuring IGMP Filtering (CLI example)	99
Configuring a Static Mrouter (CLI example)	100
Configuring IGMP Snooping (BBI example)	100
Configuring IGMP Filtering (BBI example)	102
Configuring a Static Multicast Router (BBI example)	105
OSPF	107
OSPF overview	107
Types of OSPF areas	107
Types of OSPF routing devices	108
Neighbors and adjacencies	109
Link-State Database	109
Shortest Path First Tree	109
Internal versus external routing	109
OSPF implementation in GbE2c software	110
Configurable parameters	110
Defining areas	110
Assigning the area index	111
Using the area ID to assign the OSPF area number	111
Attaching an area to a network	111
Interface cost	112
Electing the designated router and backup	112
Summarizing routes	112
Default routes	112
Virtual links	113
Router ID	114
Authentication	114
Host routes for load balancing	115
OSPF features not supported in this release	116
OSPF configuration examples	116
Example 1: Simple OSPF domain (CLI example)	116
Example 1: Simple OSPF domain (BBI example)	117
Example 2: Virtual links	124
Configuring OSPF for a virtual link on Switch A	124
Configuring OSPF for a virtual link on Switch B	126
Other Virtual Link Options	127
Example 3: Summarizing routes	127
Verifying OSPF configuration	128
Remote monitoring	129
Introduction	129
Overview	129
RMON group 1—statistics	129
Configuring RMON Statistics (CLI example)	129
Configuring RMON Statistics (BBI example)	130
RMON group 2—history	132
History MIB objects	132
RMON group 3—alarms	134
Alarm MIB objects	134
RMON group 9—events	138
Configuring RMON Events (CLI example)	138
Configuring RMON Events (BBI example 1)	139
High availability	140
Introduction	140
Uplink Failure Detection	140
Failure Detection Pair	141
Spanning Tree Protocol with UFD	141
Configuration guidelines	141
Monitoring Uplink Failure Detection	141
Configuring Uplink Failure Detection	142
Configuring UFD on Switch 1 (CLI example)	142
Configuring UFD on Switch 2 (CLI example)	142
Configuring Uplink Failure Detection (BBI example)	143
VRRP overview	145
VRRP components	145
Virtual router	145
Virtual router MAC address	145
Owners and renters	145
Master and backup virtual router	145
Virtual Interface Router	145
VRRP operation	146
Selecting the master VRRP router	146
Failover methods	146
Active-Active redundancy	147
GbE2c extensions to VRRP	147
Tracking VRRP router priority	147
Virtual router deployment considerations	147
Assigning VRRP virtual router ID	148
Configuring the switch for tracking	148
High availability configurations	148
Active-Active configuration	148
Task 1: Configure Switch A	149
Task 2: Configure Switch B	150
Task 1: Configure Switch A (BBI example)	151
Troubleshooting tools	159
Introduction	159
Port Mirroring	159
Configuring Port Mirroring (CLI example)	160
Configuring Port Mirroring (BBI example)	161
Other network troubleshooting techniques	162
Console and Syslog messages	162
Ping	162
Trace route	163
Statistics and state information	163
Customer support tools	163

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Quality of Service 80

Using DSCP values to provide QoS

The six most significant bits in the TOS byte of the IP header are defined as DiffServ Code Points (DSCP). Packets are

marked with a certain value depending on the type of treatment the packet must receive in the network device. DSCP

is a measure of the Quality of Service (QoS) level of the packet.

Differentiated Services concepts

To differentiate between traffic flows, packets can be classified by their DSCP value. The Differentiated Services (DS)

field in the IP header is an octet, and the first six bits, called the DS Code Point (DSCP), can provide QoS functions.

Each packet carries its own QoS state in the DSCP. There are 64 possible DSCP values (0-63).

Figure 12

Layer 3 IPv4 packet

The GbE2c can perform the following actions to the DSCP:

•

Read the DSCP value of ingress packets

•

Re-mark the DSCP value to a new value

•

Map the DSCP value to an 802.1p priority

Once the DSCP value is marked, the GbE2c can use it to direct traffic prioritization.

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 applying a set of rules to packets, based on the DSCP value, as they

hop through the network.

The GbE2c 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 below. Routers use drop precedence to determine which packets to discard last when the network

becomes congested. AF PHB is described in RFC 2597.

Table 18

Assured forwarding drop-down precedence

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 below. CS PHB is described in RFC 2474.

Table 19

Class selector priority classes

Priority

Class Selector

DSCP

Highest

CS7

CS6

CS5

CS4

CS3