Type of Service (ToS) Precedence

[Jerry Kreger]

Hi Folks,

I am looking for infomation on how to set the ToS precedence. In an IP packet there is an IP header. In this header there is a ToS (Type of Service) byte:

------------------------------------
0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
------------------------------------
| | ToS |
^
L Precedence

There is documentation on how to set the ToS portion of the ToS byte (setsockopt; see man ip) but I don't know how to set the precedence portion of the ToS byte. Does anyone know how to do this?

Thanks for any help you can give.

OS=HP-UX 11.00


Jerry

[Ceesjan van Hattum]

The precedence-bits have not been changed since RFC791:

Packets can be filtered by precedence level, as specified by a number from
0 to 7, or by name.
The following is a list of precedence names:
bits name
--- -------------
111 network (network control)
110 internet (internetwork control)
101 critical (CRITIC/ECP)
100 flash-override
011 flash
010 immediate
001 priority
000 routine

Regards,
Ceesjan

[Steven Gillard_2 · Accepted solution]

Have you tried setting the high order bits in the unsigned char argument to setsockopt(IP_TOS)? Eg the value 0xb0 (binary 11100000) will set all the precedence bits in the TOS header to 1.

The man page only specifies three allowable values but states that no error will be returned for the other possibilities.

Regards,
Steve

[Steven Gillard_2]

Sorry, that should read 'the value 0xe0 (binary 11100000) will set all the precedence bits in the TOS header to 1'.

Regards,
Steve