Actiontec MI424-WR-Rev-F Router Manual PDF (Setup & Configuration Guide)

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Conﬁguring Quality of Service

A.2

Traﬃc Shaping

A

196

TCP Serialization

Enable TCP Serialization from its drop-down list, either for active voice calls only

or for all traffic. The screen will refresh, adding a “Maximum Delay” text box. This

function allows the maximum allowed transmission time frame (in milliseconds)

of a single packet to be defined. Any packet requiring a longer time to be

transmitted will be fragmented to smaller sections. This avoids transmission of

large, bursty packets that can cause delay or jitter for real-time traffic, such

as VoIP.

Queue Policy

The class policy determines the traffic policy of routing packets inside the

class. Depending on the type of device, options include

Strict Policy

and

Class Based

.

Rx Bandwidth

In the same manner, this Rx bandwidth limits the FiOS Router’s bandwidth

reception rate.

A.2b Shaping Classes

The bandwidth of a device can be divided to reserve constant portions of

bandwidth to predefined traffic types. Such a portion is known as a shaping

class. When not used by its predefined traffic type or owner (for example VoIP),

the class will be available to all other traffic. However, when needed, the entire

class is reserved solely for its owner. Also, the maximum bandwidth that a class

uses can be limited, even if the entire bandwidth is available.

When a shaping class is defined for a specific traffic type, two shaping classes

are created. The second class is the “Default Class”, which is responsible for all the

packets that do not match the defined shaping class, or any other classes that

might be defined on the device. This can be viewed in the “Class Statistics” screen.

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To define a shaping class:

Click

1.

Add

in the “Tx Traffic Shaping” section of the Edit Device Traffic Shaping

screen. The “Add Shaping Class” screen appears.

Name the new class and click

2.

Apply

.

Click the class name in the Edit Device Traffic Shaping screen to edit the

3.

shaping class. The “Edit Shaping Class” screen appears.

Configure the following parameters:

Class Priority

Select the priority of this class from the drop-down menu (0 being highest

priority, while 7 is lowest).

Bandwidth

Reserved

- Enter the amount of bandwidth (in Kbits/second) to be reserved

for this class only.

Maximum

- Select the amount of bandwidth available to this class. Options

include

Unlimited

or

Specify

. If Specify is enabled, enter the bandwidth

amount (in Kbits/second, or as a percentage of the total bandwidth) in the

appropriate text box.

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Policy

Select a QoS policy from the drop-down menu. Options include Priority, FIFO

(First In, First Out), Fairness (balanced set), RED (Random Early Detection), and

WRR (Weighted Round Robin).

When should this rule occur?

By default, the rule will always be active. However, scheduler rules can be

configured to define time periods during which the rule is active. To learn how

to configure scheduler rules, see the “Advanced Settings” chapter.

A.2c

Ingress Data

The FiOS Router can control outgoing data fairly easily. It can queue packets,

delay them, give precedence to other packets, or drop them. This helps in

resolving upload (Tx) traffic bottlenecks, and in most cases is sufficient. However,

in the case of download (Rx) traffic bottlenecks, the ability to control the flow is

much more limited. The FiOS Router cannot queue packets, since in most cases

the local network (LAN) is much faster then the Internet (WAN), and when the

FiOS Router receives a packet from the Internet, it passes it immediately to the

local network.

QoS for ingress data has the following limitations, which do not exist for

outgoing data:

QoS can only be applied to TCP streams (UDP streams cannot be delayed);

•

no borrowing mechanism;

•

and when reserving Rx bandwidth, it is strictly taken from the bandwidth of

•

all other classes.

Furthermore, the FiOS Router cannot control the behavior of the ISP, which may

not have proper QoS handling. Unfortunately, this is a common situation. Let’s

look at a scenario of downloading a large file and surfing the Internet at the

same time. Downloading the file is distinguished by small requests, followed

by very large responses. This may result in blocking HTML traffic at the ISP.

A solution for such a situation is limiting the bandwidth of low-priority TCP

connections (such as the file download).

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A.2d

Differentiated Services Code Point Settings

In order to understand what DSCP is, one must first be familiarized with the

Differentiated Services model.

Differentiated Services (Diffserv) is a Class of Service (CoS) model that

enhances best-effort Internet services by differentiating traffic by users, service

requirements, and other criteria. Packets are specifically marked, allowing

network nodes to provide different levels of service, as appropriate for voice

calls, video playback, or other delay-sensitive applications, via priority queuing

or bandwidth allocation, or by choosing dedicated routes for specific traffic

flows.

Diffserv defines a field in IP packet headers referred to as the Differentiated

Services Codepoint (DSCP). Hosts or routers passing traffic to a Diffserv-enabled

network will typically mark each transmitted packet with an appropriate DSCP.

The DSCP markings are used by Diffserv network routers to appropriately

classify packets and to apply particular queue handling or scheduling behavior.

The FiOS Router provides a table of predefined DSCP values, which are mapped

to 802.1p priority marking method. Any of the existing DSCP setting can be

edited or deleted, and new entries can be added.

Click

1.

Quality of Service

at the top of the Home screen, then click

DSCP

Settings

. The “DSCP Settings” screen appears.

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Conﬁguring Quality of Service

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Traﬃc Shaping

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200

To edit an existing entry, click the appropriate icon in the “Action” column.

2.

To add a new entry, click

Add

. In either case, the “Edit DSCP Settings”

screen appears.

Configure the following parameters:

3.

DSCP Value (hex)

- Enter the DSCP value as a hexadecimal value.

802.1p Priority

- Select a 802.1p priority level from the drop-down list,

zero being the lowest and seven the highest (each priority level is mapped

to low/medium/high priority). The default DSCP value for packets with an

unassigned value is zero.

Click

4.

Apply

to save the settings.

A.2e

802.1p Settings

The IEEE 802.1p priority marking method is a standard for prioritizing network

traffic at the data link/Mac sub-layer. 802.1p traffic is simply classified and sent to

the destination, with no bandwidth reservations established.

The 802.1p header includes a 3-bit prioritization field, which allows packets to

be grouped into eight levels of priority. By default, the highest priority is seven,

which might be assigned to network-critical traffic. Values five and six may be

applied to delay-sensitive applications such as interactive video and voice. Data

classes four through one range from controlled-load applications down to “loss

eligible” traffic. Zero is the value for unassigned traffic and used as a best effort

default, invoked automatically when no other value has been set.

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