Configuring Differentiated Services

C H A P T E R 24

This chapter describes how to configure Differentiated Services (DiffServ).

This chapter contains the following topics:

Section , Understanding Differentiated Services (DiffServ)

Section , Configuring Differentiated Services via CLI

Section , Configuring Differentiated Services via Web Interface

Section , Configuring DiffServ for Voice Over IP (VoIP)

Understanding Differentiated Services (DiffServ)

Differentiated Services (DiffServ) is one technique for implementing Quality of Service (QoS) policies. Using DiffServ in your network allows you to directly configure the relevant parameters on the switches and routers rather than using a resource reservation protocol.This section explains how to configure the Sun Netra CP3240 switch to identify which traffic class a packet belongs to, and how it should be handled to provide the desired quality of service. As implemented on the Sun Netra CP3240 switch, DiffServ allows you to control what traffic is accepted and what traffic is discarded.

Traffic to be processed by the DiffServ feature requires an IP header if the system uses IP Precedence or IP DSCP marking.

How you configure DiffServ support on a Sun Netra CP3240 switch varies depending on the role of the switch in your network:

Edge device - An edge device handles ingress traffic, flowing towards the core of the network, and egress traffic, flowing away from the core. An edge device segregates inbound traffic into a small set of traffic classes, and is responsible for determining a packet’s classification. Classification is primarily based on the contents of the Layer 3 and Layer 4 headers, and is recorded in the Differentiated Services Code Point (DSCP) added to a packet’s IP header.

Interior node - A switch in the core of the network is responsible for forwarding packets, rather than for classifying them. It decodes the DSCP in an incoming packet, and provides buffering and forwarding services using the appropriate queue management algorithms.

Before configuring DiffServ on a particular Sun Netra CP3240 switch, you must determine the QoS requirements for the network as a whole. The requirements are expressed in terms of rules, which are used to classify inbound traffic on a particular interface. FASTPATH does not support DiffServ in the outbound direction.

During configuration, you define DiffServ rules in terms of classes, policies and services:

Class - A class consists of a set of rules that identify which packets belong to the class. Inbound traffic is separated into traffic classes based on Layer 2, Layer 3, and Layer 4 header data. One class type is supported, All, which specifies that every match criterion defined for the class must be true for a match to occur.

Policy - Defines the QoS attributes for one or more traffic classes. An example of an attribute is the ability to mark a packet at ingress. FASTPATH supports the ability to assign traffic classes to output CoS queues, and to mirror incoming packets in a traffic stream to a specific egress interface (physical port or LAG).
The FASTPATH software supports the Traffic Conditioning Policy type which is associated with an inbound traffic class and specifies the actions to be performed on packets meeting the class rules:

Marking the packet with a given DSCP, IP precedence, or CoS

Policing packets by dropping or re-marking those that exceed the class’s assigned data rate

Counting the traffic within the class

Service - Assigns a policy to an interface for inbound traffic.

Configuring Differentiated Services via CLI

This example shows how a network administrator can provide equal access to the Internet (or other external network) to different departments within a company. Each of four departments has its own Class B subnet that is allocated 25% of the available bandwidth on the port accessing the Internet.

FIGURE 24-1 DiffServ Internet Access Example Network Diagram

Enabling DiffServ Inbound

Ensure DiffServ operation is enabled for the switch.

config
  diffserv

Create a DiffServ class of type “all” for each of the departments, and name them. Define the match criteria -- Source IP address -- for the new classes.

CODE EXAMPLE 24-1 Creating a Diffserv Class Type All
class-map match-all finance_dept match srcip 172.16.10.0 255.255.255.0 exit class-map match-all marketing_dept match srcip 172.16.20.0 255.255.255.0 exit class-map match-all test_dept match srcip 172.16.30.0 255.255.255.0 exit class-map match-all development_dept match srcip 172.16.40.0 255.255.255.0 exit

CODE EXAMPLE 24-1 Creating a Diffserv Class Type All

class-map match-all finance_dept
 match srcip 172.16.10.0 255.255.255.0
exit
 
class-map match-all marketing_dept
 match srcip 172.16.20.0 255.255.255.0
exit
 
class-map match-all test_dept
 match srcip 172.16.30.0 255.255.255.0
exit
 
class-map match-all development_dept
 match srcip 172.16.40.0 255.255.255.0
exit

Create a DiffServ policy for inbound traffic named 'internet_access', adding the previously created department classes as instances within this policy.

This policy uses the assign-queue attribute to put each department's traffic on a different egress queue. This is how the DiffServ inbound policy connects to the CoS queue settings established in the following example.

CODE EXAMPLE 24-2 Creating a Diffserv Policy for Inbound Traffic
policy-map internet_access in class finance_dept assign-queue 1 exit class marketing_dept assign-queue 2 exit class test_dept assign-queue 3 exit class development_dept assign-queue 4 exit exit

CODE EXAMPLE 24-2 Creating a Diffserv Policy for Inbound Traffic

policy-map internet_access in
 class finance_dept
   assign-queue 1
 exit
 class marketing_dept
   assign-queue 2
 exit
 class test_dept
   assign-queue 3
 exit
 class development_dept
   assign-queue 4
 exit
exit

Configuring DiffServ on FASTPATH Software

Attach the defined policy to interfaces 1/0/1 through 1/0/4 in the inbound direction

CODE EXAMPLE 24-3 Attaching the Policy to Interfaces
interface 1/0/1 service-policy in internet_access exit interface 1/0/2 service-policy in internet_access exit interface 1/0/3 service-policy in internet_access exit interface 1/0/4 service-policy in internet_access exit

CODE EXAMPLE 24-3 Attaching the Policy to Interfaces

interface 1/0/1
 service-policy in internet_access
exit
interface 1/0/2
 service-policy in internet_access
exit
interface 1/0/3
 service-policy in internet_access
exit
interface 1/0/4
 service-policy in internet_access
exit

Set the CoS queue configuration for the (presumed) egress interface 1/0/5 such that each of queues 1, 2, 3 and 4 get a minimum guaranteed bandwidth of 25%. All queues for this interface use weighted round robin scheduling by default. The DiffServ inbound policy designates that these queues are to be used for the departmental traffic through the assign-queue attribute. It is presumed that the switch will forward this traffic to interface 1/0/5 based on a normal destination address lookup for internet traffic.

CODE EXAMPLE 24-4 Setting CoS Queue for Egress
interface 1/0/5 cos-queue min-bandwidth 0 25 25 25 25 0 0 exit exit

Configuring Differentiated Services via Web Interface

Use the following screens to perform the same configuration using the Graphical User Interface:

FIGURE 24-2 DiffServ Configuration

FIGURE 24-3 \DiffServ Class Configuration

FIGURE 24-4 DiffServ Class Configuration

FIGURE 24-5 Source IP Address

FIGURE 24-6 DiffServ Class Configuration

FIGURE 24-7 DiffServ Class Summary

FIGURE 24-8 DiffServ Policy Configuration

FIGURE 24-9 DiffServ Policy Configuration

FIGURE 24-10 DiffServ Policy Class Definition

FIGURE 24-11 Assign Queue

FIGURE 24-12 DiffServ Policy Attribute Summary

FIGURE 24-13 DiffServ Policy Attribute Summary

FIGURE 24-14 DiffServ Service Configuration

FIGURE 24-15 DiffServ Service Summary

FIGURE 24-16 DiffServ VoIP Example Network Diagram

Configuring DiffServ for Voice Over IP (VoIP)

One of the most valuable uses of DiffServ is to support Voice over IP (VoIP). VoIP traffic is inherently time-sensitive: for a network to provide acceptable service, a guaranteed transmission rate is vital. This example shows one way to provide the necessary quality of service: how to set up a class for UDP traffic, have that traffic marked on the inbound side, and then expedite the traffic on the outbound side. The configuration script is for Router 1 in the accompanying diagram: a similar script should be applied to Router 2.

Enter Global Config mode. Set queue 5 on all ports to use strict priority mode. This queue shall be used for all VoIP packets. Activate DiffServ for the switch.

CODE EXAMPLE 24-5 Setting Queue on All Ports
config cos-queue strict 5 diffserv

Create a DiffServ classifier named 'class_voip' and define a single match criterion to detect UDP packets. The class type "match-all" indicates that all match criteria defined for the class must be satisfied in order for a packet to be considered a match.

CODE EXAMPLE 24-6 Creating a Diffserv Classifier
class-map match-all class_voip match protocol udp exit

Create a second DiffServ classifier named 'class_ef' and define a single match criterion to detect a DiffServ code point (DSCP) of 'EF' (expedited forwarding). This handles incoming traffic that was previously marked as expedited elsewhere in the network.

CODE EXAMPLE 24-7 Creating a Second Diffserv Classifier
class-map match-all class_ef match ip dscp ef exit

Create a DiffServ policy for inbound traffic named 'pol_voip', then add the previously created classes 'class_ef' and 'class_voip' as instances within this policy.

This policy handles incoming packets already marked with a DSCP value of 'EF' (per 'class_ef' definition), or marks UDP packets per the 'class_voip' definition) with a DSCP value of 'EF'. In each case, the matching packets are assigned internally to use queue 5 of the egress port to which they are forwarded.

CODE EXAMPLE 24-8 Creating a Diffserv Policy
policy-map pol_voip in class class_ef assign-queue 5 exit class class_voip mark ip-dscp ef assign-queue 5 exit exit

Attach the defined policy to an inbound service interface.

CODE EXAMPLE 24-9 Attaching the Policy to Inbound Interface
interface 1/0/2 service-policy in pol_voip exit exit