TOS Configuration

Description:

Use this pane to configure Type of Service (TOS) parameters for an IP Profile. Type of Service can be configured in both SIP and H.323. The IMG supports RFC 1349 which is Type Of Service Support. When making an IP Call the path that the call follows varies depending on the quality of service the circuit provides. There are different factors that are looked at and decided on when making the decision of which path to take. Some of the decisions are as follows:

The optimal path to follow depends largely on the user. Type of service configuration gives you the ability to decide which circuits will get high or normal throughput, high or normal delay, and high or normal reliability.

 

Accessing this Pane

Dialogic IMG EMS -> IP Bearer Profiles -> IP Bearer Profile -> TOS Configuration

sc_tree_tos.png

 

Maximum Objects:

1 TOS object per IP Bearer Profile

 

Related Topics:

Configuring Type of Service

 

CientView Pane:

sc_tos.png

 

 

Field Descriptions:

Within the RTP packet are 8 bits of information reserved to the type of service. They are broken up as shown in the table below

0     1     2

3

4

5

6

7

PRECEDENCE

DELAY (D)

THROUGHPUT (T)

RELIABILITY (R)

COST (C)

CONGESTION

 

The fields below fill in this ethernet packet depending on the selections made in the TOS Settings Pane

 

Precedence:

The first three bits of the RTP packet are a bit mask and specify the precedence varying from 0 to 7. The precedence field denotes importance or priority of the RTP packet. This field does not affect the route. It affects different aspects of packet forwarding. The precedence field has a drop down menu with the following selections:

 

TOS Fields: (Type of Service)

The next four (Delay, Throughput, Reliability, and Cost) are all Types Of Service and specify how the network should make tradeoffs between throughput, delay, reliability, and cost.

Delay:

Throughput:

Reliability:

Cost:

Congestion: (Must be Zero):

The last is considered MBZ (Must be Zero). This value is always 0.

Property

ClientView Setting

Bit Mask / Binary Value

Precedence

ROUTINE (DEFAULT)

000

 

PRIORITY

001

 

IMMEDIATE

010

 

FLASH

011

 

FLASH OVERRIDE

100

 

CRITICS/ECP

101

 

INTERNETWORK CONTROL

110

 

NETWORK CONTROL

111

Delay

Normal

Low

0

1

Throughput

 

Normal

High

0

1

Reliability

 

Normal

High

0

1

Cost

 

Normal

Low

0

1

Congestion

N/A

0

 

 

RTP TRACE

Below is an RTP Trace of the TOS feature.

 

sc_sip_h323_tos_trace.png

 

Mapping Differentiated Services Code Point (DSCP) to Type of Service (TOS)

DSCP is a newer model in which traffic is treated with priorities based on the Type Of Services field. The IMG does not support the DSCP model. However the DSCP model can be mapped to values used in the TOS model. Below are tables on how the values are mapped. The mappings are only valid for RTP packets and does not affect signaling packets.

 

Name DSCP Value (Decimal) DSCP (Binary)   Precedence Delay Throughput Reliability
Default 0 00000000   Routine Normal Normal Normal
AF11 10 00001010   Priority Normal High Normal
AF12 12 00001100   Priority Low Normal Normal
AF13 14 00001110   Priority Low High Normal
AF21 18 00010010   Immediate Normal High Normal
AF22 20 00010100   Immediate Low Normal Normal
AF23 22 00010110   Immediate Low High Normal
AF31 26 00011010   Flash Normal High Normal
AF32 28 00011100   Flash Low Normal Normal
AF33 30 00011110   Flash Low High Normal
AF41 34 00100010   Flash Override Normal High Normal
AF42 36 00100100   Flash Override Low Normal Normal
AF43 38 00100110   Flash Override Low High Normal
EF 46 00101110   Critical ECP Low High Normal

 

 

cf_tos_dscp_mapping.png