L2 QOS - 802.1p Priority

This section will explain you about 802.1p priority field in L2 header.This field is majorly used in L2 QOS. 

      The 802.1p priority is located in the L2 packet header. It is used when you don’t want to analyze the L3 packet header, but need to ensure QOS in L2 environment. As shown in below diagram, the 4-byte 802.1Q header contains 2-byte TPID (Tag Protocol Identifier valued as 0x8100) and 2-byte TCI (Tag Control Information).

Figure 1 - Ethernet Frame with 802.1Q Header

The following figure shows the detailed contents of the 802.1Q header. Ethernet frame with 802.1Q header.

Figure 2 802.1Q header

As shown in above diagram, the Priority field in TCI is the 802.1p priority. It comprises three bits and the value range is 0-7.

It is called 802.1p priority.

Hope this information is informative for you. In coming post, I will share 802.1p configuration for L2 QOS.

For any feedback, Plz comment with your name and mail ID. For new users, you can use Name/URL option. 

Thanks for reading...

MAIPU - Configuration for QOS and IPSLA

Maipu configuration Example – QOS , IPSLA.

Here we have one example, How to configure Maipu router for QOS, IPSLA and SNMP traps. I think this configuration template you can use as reference.

Functions Included : 

QOS  – LLQ + CBWFQ + Traffic shaping.

 IP SLA – Jitter,ICMPEcho,ICMP Path Jitter, Flow statistics,UDP Echo.

SNMP traps

After doing  below configuration,  you can monitor Maipu device from your NMS. Make sure that Maipu MIBs are integrated in your NMS.

Device used: Maipu 1800

Configuration :

Building Configuration...done

! Current configuration : 5621 bytes

!

! Last configuration change at UTC THU APR 14 18:56:15 2011

! Flash config last updated at UTC THU JAN 01 01:24:26 1970

! Configuration version 0.18

!

!software version 6.1.38(JSJR-35)(integrity)

!software image file flash0: /system/rp5-c-6.1.38(JSJR-35).bin

!compiled on Jan  4 2011, 12:34:35

hostname XXXX

service timestamps debug datetime

service timestamps log datetime

service taskname debug

service taskname log

no service password-encrypt

no service new-encrypt

service login-secure

enable timeout 0

enable password OW encrypt

no exception reboot

ip mef

ip load-sharing per-destination

ip flow enable

ip access-list extended 1001

 10 permit ip host 22.0.0.1 130.255.0.0 0.0.255.255

 exit

ip access-list extended 1002

 10 permit ip any host 130.255.153.120

 exit

ip access-list extended xx

 10 permit ip host 68.1.1.2 any

 exit

vlan 1

 description default

 port 0-7 untagged

 exit

class-map match-all xx

  match access-group xx

 exit

class-map match-all snmp

  match access-group 1001

 exit

class-map match-all telnet

  match access-group 1002

 exit

policy-map test

 class xx

  priority 1000

  exit

 class snmp

  priority 2000

  exit

 class telnet

  bandwidth 1000

  exit

 class class-default

  shape average 1000000

  exit

 exit

policy-map test1

 class class-default

  set qos-group 1

  exit

 exit

interface fastethernet0

 ip address 17.1.1.2 255.255.255.0

 service-policy input test1

 exit

interface fastethernet0.1

 ip address 19.1.1.2 255.255.255.0

 encapsulation dot1q 1

 traffic-shape 1000000 10000

 exit

interface fastethernet1

 ip address 192.168.2.84 255.255.252.0

 service-policy output test

 traffic-shape 1000000 50000

 exit

interface fastethernet1.1

 exit

interface null0

 exit

router rip

 version 2

 network fastethernet0

 no auto-summary

 exit

ip route 12.1.1.0 255.255.255.0 18.1.1.1

ip route 17.1.1.0 255.255.255.0 22.0.0.2

ip route 130.255.0.0 255.255.0.0 22.0.0.2

line vty 0 15

 exec-timeout 0 0

 no login

 exit

ntp master 8

ntp authenticate

ntp authentication-key 520915 md5 SYSZXZ encrypt

check cpu enable

check cpu time-interval 1

snmp-server start

snmp-server view default 1.3.6.1 include

snmp-server community public view default ro

snmp-server host 130.255.153.200 traps community public version 2

snmp-server host 130.255.153.120 traps community public version 2

snmp-server host 192.168.2.85 traps community public version 2

snmp-server enable traps bgp established

snmp-server enable traps bgp backward-transition

snmp-server enable traps frame-relay dlci-status-change

snmp-server enable traps frame-relay pvc-connect-status-change

snmp-server enable traps frame-relay pvc-connect-status-notify

snmp-server enable traps ospf if-authen-failure

snmp-server enable traps ospf virtif-authen-failure

snmp-server enable traps ospf if-config-error

snmp-server enable traps ospf virtif-config-error

snmp-server enable traps ospf if-state-change

snmp-server enable traps ospf virtif-state-change

snmp-server enable traps ospf nbr-state-change

snmp-server enable traps ospf virtnbr-state-change

snmp-server enable traps ospf if-rx-bad-packet

snmp-server enable traps ospf virtif-rx-bad-packet

snmp-server enable traps ospf tx-retransmit

snmp-server enable traps ospf virtif-tx-retransmit

snmp-server enable traps ospf originate-lsa

snmp-server enable traps ospf max-age-lsa

snmp-server enable traps ospf lsdb-approaching-overflow

snmp-server enable traps ospf lsdb-overflow

snmp-server enable traps snmp authentication

snmp-server enable traps snmp coldstart

snmp-server enable traps snmp warmstart

snmp-server enable traps snmp linkdown

snmp-server enable traps snmp linkup

snmp-server enable traps snmp enterprise snmp-agent-up

snmp-server enable traps snmp enterprise snmp-agent-down

snmp-server enable traps snmp enterprise rmon-rising

snmp-server enable traps snmp enterprise rmon-falling

snmp-server enable traps veth remote-status

snmp-server enable traps remote-ping probe-failed

snmp-server enable traps remote-ping test-failed

snmp-server enable traps remote-ping test-complete

snmp-server enable traps vrf

rtr enable

rtr 1 jitter

 set dest-ipaddr 17.1.1.1 dest-port 200 g711alaw

 number-of-history-kept 100

 CreatedTime WED JAN 26 17:12:38 2011

 LatestModifiedTime THU JAN 01 01:38:09 1970

 exit

rtr 2 icmpecho

 set 17.1.1.1 1 70 2

 number-of-history-kept 100

 CreatedTime MON JAN 19 16:58:24 1970

 LatestModifiedTime THU JAN 01 01:38:32 1970

 exit

rtr 3 icmp-path-echo

 set dest-ipaddr 17.1.1.1 source-ipaddr 18.1.1.2

 number-of-history-kept 90

 CreatedTime TUE MAR 15 19:21:11 2011

 LatestModifiedTime THU APR 14 18:55:47 2011

 exit

rtr 4 icmp-path-jitter

 set dest-ipaddr 17.1.1.1

 number-of-history-kept 100

 CreatedTime THU APR 14 18:53:12 2011

 LatestModifiedTime THU APR 14 18:53:34 2011

 exit

rtr 5 flow-statistics

 flow-statistics interface fastethernet0 interval 10

 CreatedTime THU APR 14 18:53:59 2011

 LatestModifiedTime THU APR 14 18:54:20 2011

 exit

rtr 6 udpecho

 set dest-ipaddr 17.1.1.1 dest-port 300

 number-of-history-kept 100

 CreatedTime THU APR 14 18:54:36 2011

 LatestModifiedTime THU APR 14 18:54:53 2011

 exit

rtr group 1

 member 3

 exit

rtr schedule 1 entity 1 start now ageout 900 life forever

rtr schedule 2 entity 2 start now ageout 900 life forever

rtr schedule 4 entity 4 start now ageout 900 life forever

rtr schedule 5 entity 5 start now ageout 900 life forever

rtr schedule 6 entity 6 start now ageout 900 life forever

rtr schedule 10 group 1 start now ageout 900 life forever

rtr responder

!end

1800#

1800#sh ver

               MyPower (R) Operating System Software

MP1800 system image file (flash0: /system/rp5-c-6.1.38(JSJR-35).bin), version 6.1.38(JSJR-35)(integr

ity), Compiled on Jan  4 2011, 12:34:35

Copyright (C) 1999 Maipu Communication Technology Co., Ltd. All Rights Reserved.

MP1800 Version Information

        System ID           : 00017a0c6124

        Hardware Model      : MPC8270 with 128 MBytes SDRAM, 32 MBytes flash

        Hardware Version    : 020(Hotswap Unsupported)

        MPU CPLD Version    : 001

        Monitor Version     : 2.18

        Software Version    : 6.1.38(JSJR-35)(integrity)

        Software Image File : flash0: /system/rp5-c-6.1.38(JSJR-35).bin

        Compiled            : Jan  4 2011, 12:34:35

System Uptime is 1 week 5 days

I am using this configuration for my use. I am sharing this, May be it will be useful for you ..

Plz let me know if you have any queries.

Models Of QOS

Quality of Service Models

In this post, we will see Models of QOS.A QOS model, also called a level of service, describes a set of end-to-end QOS capabilities. End-to-end QOS is the ability of the network to deliver service required by specific network traffic from one end of the network to another.

Cisco IOS QOS software supports three types of service models: best effort, integrated, and differentiated services.

This section describes these service models:

•          Best-Effort Service
•          Integrated Service
•          Differentiated Service

The features in Cisco IOS QOS software address the requirements for these service models.

Best-Effort Service

Best effort is a single service model in which an application sends data whenever it must, in any quantity, and without requesting permission or first informing the network. For best-effort service, the network delivers data if it can, without any assurance of reliability, delay bounds, or throughput.

The Cisco IOS QOS feature that implements best-effort service is first-in, first-out (FIFO) queuing. Best-effort service is suitable for a wide range of networked applications such as FTP, Exchange,etc.

Integrated Service

Integrated service is a multiple service model that can accommodate multiple QOS requirements. In this model the application requests a specific kind of service from the network before sending data. The request is made by explicit signalling; the application informs the network of its traffic profile and requests a particular kind of service that can encompass its bandwidth and delay requirements. The application is expected to send data only after it gets a confirmation from the network. It is also expected to send data that lies within its described traffic profile.

The network performs admission control, based on information from the application and available network resources. It also commits to meeting the QoS requirements of the application as long as the traffic remains within the profile specifications. The network fulfills its commitment by maintaining per-flow state and then performing packet classification, policing, and intelligent queuing based on that state.

Differentiated Service

Differentiated service is a multiple service model that can satisfy differing QOS requirements. However, unlike the integrated service model, an application using differentiated service does not explicitly signal the router before sending data.

For differentiated service, the network tries to deliver a particular kind of service based on the QOS specified by each packet.

This specification can occur in different ways, for example, using the IP Precedence bit settings in IP packets or source and destination addresses.

These features that support the differentiated service model:

·         Committed access rate (CAR), which performs packet classification through IP Precedence and QoS group settings. CAR performs metering and policing of traffic, providing bandwidth management.

·         Intelligent queuing schemes such as WRED and WFQ and their equivalent features on the Versatile Interface Processor (VIP), which are VIP-Distributed WRED and VIP-Distributed WFQ. These features can be used with CAR to deliver differentiated services.

QOS Techniques

QOS Tools/Techniques:

In previous post we discussed about overview of QOS. Now we will see, what are tools/techniques in QOS. How we are going to do this ?

QOS provides us some tools/techniques: 

• Classification and Marking
• Congestion Avoidance
• Policing and Shaping
• Queuing

Classification: Classification means identifying applications and grouping of applications. Performed by Access-list and NBAR (Cisco proprietary)

Marking: Marking means coloring/tagging identified groups as per requirement, So that it can be recognized in network with same marking and whatever the priority is assigned that color/tag it will be catered to that group in full network. Performed by IP Precedence and DSCP.

Suppose I identified a group of application (http) then I will assign a tag to that group (IP Precedence 5). That means HTTP is having 5 as marking and 5 means best in IP Precedence. It results that HTTP will be passed first from interface. But we need to configure a service policy and then apply that service policy to interface.

Here is mentioned example:

Router#conf t

Router(config)#class-map match-all WEBTRAFFIC  --- Class-map is used to classify the traffic

Router(config-cmap)#match protocol http               --- Identified HTTP traffic by NBAR

Router(config-cmap)#exi

Router(config)#policy-map QOS                                  --- Created Policy

Router(config-pmap)#class WEBTRAFFIC                  --- Match class to assign marking

Router(config-pmap-c)#set ip precedence 5             --- Marked with IP Precedence 5   

Router(config-pmap-c)#exi

Router(config-pmap)#exi

Router(config)#

Router(config)#int fa0/0

Router(config-if)#service-policy output QOS          --- Policy map applied on WAN Interface.

Router(config-if)#exi

Router(config)#exi

Router#

Congestion Avoidance:

Congestion avoidance techniques monitor network traffic loads in an effort to anticipate and avoid congestion at common network and internetwork bottlenecks before it becomes a problem.

 These techniques are designed to provide preferential treatment for premium (priority) class traffic under congestion situations while concurrently maximizing network throughput and capacity utilization and minimizing packet loss and delay.

WRED and RED are the Cisco IOS QOS congestion avoidance features.

Policing and Shaping:
The following diagram illustrates the key difference. Traffic policing propagates bursts. When the traffic rate reaches the configured maximum rate, excess traffic is dropped (or remarked). The result is an output rate that appears as a saw-tooth with crests and troughs. In contrast to policing, traffic shaping retains excess packets in a queue and then schedules the excess for later transmission over increments of time. The result of traffic shaping is a smoothed packet output rate.

Shaping implies the existence of a queue and of sufficient memory to buffer delayed packets, while policing does not. Queuing is an outbound concept; packets going out an interface get queued and can be shaped. Only policing can be applied to inbound traffic on an interface. Ensure that you have sufficient memory when enabling shaping. In addition, shaping requires a scheduling function for later transmission of any delayed packets. This scheduling function allows you to organize the shaping queue into different queues. Examples of scheduling functions are Class Based Weighted Fair Queuing (CBWFQ) and Low Latency Queuing (LLQ).

Queuing:

You can set a queuing technique on a device's interface to manage how packets are queued to be sent through the interface. Some queuing techniques use the packet marking, while others ignore them.

Queuing techniques are primarily used for managing traffic congestion on an interface, that is, they determine the priority in which to send packets when there is more data than can be sent immediately:

·         Class-Based QOS Queuing: Multiple-Action, Class-Based Policies

·         Fair Queuing (FQ): Flow-Based Queuing

·         Priority Queuing (PQ): Basic Traffic Prioritization on Routers

·         Custom Queuing (CQ): Advanced Traffic Prioritization on Routers

·         Weighted Fair Queuing (WFQ): Intelligent Traffic Prioritization on Routers

·         First In, First Out (FIFO) Queuing: Basic Store and Forward on Routers

Ref: Cisco.com