Zyxel VMG3926-B10A Router Manual PDF (Setup & Configuration Guide)

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Chapter 10 Quality of Service (QoS)

VMG3926-B10A User’s Guide

151

10.6

The QoS Shaper Setup Screen

This screen shows that you can use the token bucket algorithm to allow a certain amount of large

bursts while keeping a limit for processing outgoing traffic at the average rate. Click

Network

Setting > QoS >

Shaper Setup

. The screen appears as shown.

Figure 72

Network Setting > QoS > Shaper Setup

The following table describes the labels in this screen.

Step5: Outgoing Queue Selection

To Queue

Select a queue that applies to this class.

You should have configured a queue in the

Queue Setup

screen already.

Click

to save your changes.

Cancel

Click

Cancel

to exit this screen without saving.

Table 48

Classification Setup: Add/Edit (continued)

LABEL

DESCRIPTION

Table 49

Network Setting > QoS > Shaper Setup

LABEL

DESCRIPTION

Add New

Shaper

Click this to create a new entry.

This is the index number of the entry.

Status

This field displays whether the shaper is active or not. A yellow bulb signifies that this

policer is active. A gray bulb signifies that this shaper is not active.

Outgoing

Interface

This shows the name of the VMG's interface through which traffic in this shaper applies.

Rate Limit

(kbps)

This shows the average rate limit of traffic bursts for this shaper.

Modify

Click the

Edit

icon to edit the shaper.

Click the

Delete

icon to delete an existing shaper. Note that subsequent rules move up by

one when you take this action.

Page 152 / 327

Chapter 10 Quality of Service (QoS)

VMG3926-B10A User’s Guide

152

10.6.1

Add/Edit a QoS Shaper

Click

Add

New Shaper

in the

Shaper Setup

screen or the

Edit

icon next to a shaper to show the

following screen.

Figure 73

Shaper Setup: Add/Edit

The following table describes the labels in this screen.

10.7

The QoS Policer Setup Screen

Use this screen to view QoS policers that allow you to limit the transmission rate of incoming traffic

and apply actions, such as drop, pass, or modify the DSCP value for matched traffic. Click

Network

Setting > QoS >

Policer Setup

. The screen appears as shown.

Figure 74

Network Setting > QoS > Policer Setup

Table 50

Shaper Setup: Add/Edit

LABEL

DESCRIPTION

Enable

Select the check box to activate this shaper.

Outgoing

Interface

Select the VMG's interface through which traffic in this shaper applies

Rate Limit

Enter the average rate limit of traffic bursts for this shaper.

Click

to save your changes.

Cancel

Click

Cancel

to exit this screen without saving.

Page 153 / 327

Chapter 10 Quality of Service (QoS)

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The following table describes the labels in this screen.

10.7.1

Add/Edit a QoS Policer

Click

Add

New Policer

in the

Policer Setup

screen or the

Edit

icon next to a policer to show the

following screen.

Figure 75

Policer Setup: Add/Edit

Table 51

Network Setting > QoS > Policer Setup

LABEL

DESCRIPTION

Add new Policer

Click this to create a new entry.

This is the index number of the entry.

Status

This field displays whether the policer is active or not. A yellow bulb signifies that this

policer is active. A gray bulb signifies that this policer is not active.

Name

This field displays the descriptive name of this policer.

Regulated

Classes

This field displays the name of a QoS classifier

Meter Type

This field displays the type of QoS metering algorithm used in this policer.

Rule

These are the rates and burst sizes against which the policer checks the traffic of the

member QoS classes.

Action

This shows the how the policer has the VMG treat different types of traffic belonging to the

policer’s member QoS classes.

Modify

Click the

Edit

icon to edit the policer.

Click the

Delete

icon to delete an existing policer. Note that subsequent rules move up by

one when you take this action.

Page 154 / 327

Chapter 10 Quality of Service (QoS)

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The following table describes the labels in this screen.

10.8

Technical Reference

The following section contains additional technical information about the VMG features described in

this chapter.

IEEE 802.1Q Tag

The IEEE 802.1Q standard defines an explicit VLAN tag in the MAC header to identify the VLAN

membership of a frame across bridges. A VLAN tag includes the 12-bit VLAN ID and 3-bit user

Table 52

Policer Setup: Add/Edit

LABEL

DESCRIPTION

Active

Select the check box to activate this policer.

Name

Enter the descriptive name of this policer.

Meter Type

This shows the traffic metering algorithm used in this policer.

The

Simple Token Bucket

algorithm uses tokens in a bucket to control when traffic can be

transmitted. Each token represents one byte. The algorithm allows bursts of up to

bytes

which is also the bucket size.

The

Single Rate Three Color Marker

(srTCM) is based on the token bucket filter and

identifies packets by comparing them to the Committed Information Rate (CIR), the

Committed Burst Size (CBS) and the Excess Burst Size (EBS).

The

Two Rate Three Color Marker

(trTCM) is based on the token bucket filter and

identifies packets by comparing them to the Committed Information Rate (CIR) and the

Peak Information Rate (PIR).

Committed

Rate

Specify the committed rate. When the incoming traffic rate of the member QoS classes is

less than the committed rate, the device applies the conforming action to the traffic.

Committed

Burst Size

Specify the committed burst size for packet bursts. This must be equal to or less than the

peak burst size (two rate three color) or excess burst size (single rate three color) if it is also

configured.

This is the maximum size of the (first) token bucket in a traffic metering algorithm.

Conforming

Action

Specify what the VMG does for packets within the committed rate and burst size (green-

marked packets).

•

Pass:

Send the packets without modification.

•

DSCP Mark:

Change the DSCP mark value of the packets. Enter the DSCP mark value to

use.

Non-

Conforming

Action

Specify what the VMG does for packets that exceed the excess burst size or peak rate and

burst size (red-marked packets).

•

Drop:

Discard the packets.

•

DSCP Mark:

Change the DSCP mark value of the packets. Enter the DSCP mark value to

use. The packets may be dropped if there is congestion on the network.

Available Class

Selected Class

Select a QoS classifier to apply this QoS policer to traffic that matches the QoS classifier.

Highlight a QoS classifier in the

Available Class

box and use the

button to move it to the

Selected Class

box.

To remove a QoS classifier from the

Selected Class

box, select it and use the

button.

Apply

Click

Apply

to save your changes.

Cancel

Click

Cancel

to exit this screen without saving.

Page 155 / 327

Chapter 10 Quality of Service (QoS)

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155

priority. The VLAN ID associates a frame with a specific VLAN and provides the information that

devices need to process the frame across the network.

IEEE 802.1p specifies the user priority field and defines up to eight separate traffic types. The

following table describes the traffic types defined in the IEEE 802.1d standard (which incorporates

the 802.1p).

DiffServ

QoS is used to prioritize source-to-destination traffic flows. All packets in the flow are given the

same priority. You can use CoS (class of service) to give different priorities to different packet

types.

DiffServ (Differentiated Services) is a class of service (CoS) model that marks packets so that they

receive specific per-hop treatment at DiffServ-compliant network devices along the route based on

the application types and traffic flow. Packets are marked with DiffServ Code Points (DSCPs)

indicating the level of service desired. This allows the intermediary DiffServ-compliant network

devices to handle the packets differently depending on the code points without the need to

negotiate paths or remember state information for every flow. In addition, applications do not have

to request a particular service or give advanced notice of where the traffic is going.

DSCP and Per-Hop Behavior

DiffServ defines a new Differentiated Services (DS) field to replace the Type of Service (TOS) field

in the IP header. The DS field contains a 2-bit unused field and a 6-bit DSCP field which can define

up to 64 service levels. The following figure illustrates the DS field.

DSCP is backward compatible with the three precedence bits in the ToS octet so that non-DiffServ

compliant, ToS-enabled network device will not conflict with the DSCP mapping.

The DSCP value determines the forwarding behavior, the PHB (Per-Hop Behavior), that each packet

gets across the DiffServ network. Based on the marking rule, different kinds of traffic can be

marked for different kinds of forwarding. Resources can then be allocated according to the DSCP

values and the configured policies.

Table 53

IEEE 802.1p Priority Level and Traffic Type

PRIORITY

LEVEL

TRAFFIC TYPE

Level 7

Typically used for network control traffic such as router configuration messages.

Level 6

Typically used for voice traffic that is especially sensitive to jitter (jitter is the

variations in delay).

Level 5

Typically used for video that consumes high bandwidth and is sensitive to jitter.

Level 4

Typically used for controlled load, latency-sensitive traffic such as SNA (Systems

Network Architecture) transactions.

Level 3

Typically used for “excellent effort” or better than best effort and would include

important business traffic that can tolerate some delay.

Level 2

This is for “spare bandwidth”.

Level 1

This is typically used for non-critical “background” traffic such as bulk transfers that

are allowed but that should not affect other applications and users.

Level 0

Typically used for best-effort traffic.

DSCP (6 bits)

Unused (2 bits)

Rate

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