4.22.1. PrmTOS (Type of Service)

Parameter Number: 0x1d01

Description: The PrmTOS parameter sets the Type of Service (TOS) byte in the IP header of transmitted datagrams in order to improve the mobility of the UDP/TCP packets. The TOS byte is set on a per call basis. The prmTOS parameter can be set in the FCD file or dynamically by sending a Std_MsgSetParm to the NetTSC component instance.

Note: Not all routers recognize a precedence higher than routine (default) and may drop the packets if the default setting is changed.

The IP protocol defines the TOS byte (8 bits) as follows:

Figure 9. Type of Service (TOS) Byte

The Precedence field consists of 3 bits and defines 8 levels of precedence:

Table 62. TOS Precedence Field

Decimal Value	Binary Value	Precedence Level
0	000	Routine (Default)
1	001	Priority
2	010	Immediate
3	011	Flash
4	100	Flash Override
5	101	CRTIC/ECP (Emergency Control Procedures)
6	110	Internetwork Control
7	111	National Network Control

The Type of Service (TOS) field consists of 3 bits and (Bits 6-7 are reserved and should be zero):

Table 63. TOS Field

Bit	Binary Value	Type of Service	Description
3	0 = Normal1 = Low (Default)	Delay	Select a minimum delay link or circuit for the datagram
4	0 = Normal1 = High (Default)	Throughput	Select a high throughput link or circuit link for the datagram
5	0 = Normal1 = High (Default)	Reliability	Select a high reliability link or circuit for the datagram

Values: 0 to 255

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