Re: 0xc0

[Nathan E Norman <finn@midco.net>]

On Thu, 10 Sep 1998, Default Debian Reader wrote:

 : Anyone tell me what tos 0xc0 is in ip headers?

First, install the doc-iana package.

I'm no IP expert (I'm currently reading Stevens's IP Illustrated book)
but if you are referring to the Type Of Service field, 0xc0 is not a
valid choice.

[ from /usr/doc/doc-iana/assignments/ip-parameters.gz ]

TOS Value       Description                             Reference
---------       --------------------------              ---------
  0000          Default                                 [RFC1349]
  0001          Minimize Monetary Cost                  [RFC1349]
  0010          Maximize Reliability                    [RFC1349]
  0100          Maximize Throughput                     [RFC1349]
  1000          Minimize Delay                          [RFC1349]
  1111          Maximize Security                       [RFC1455]

The TOS value is used to indicate "better".  Only one TOS value or
property can be requested in any one IP datagram.
--

Note that the TOS field is an eight-bit field composed of a three-bit
precedence field, the 4-bit field described above, and one unused bit.
This is confusing since a TOS "value" of 0001 is written in hex as 0x02.

0xc0 would be 011000000, so two bits in the precedence field have been
set (and none of the TOS bits).  According to Stevens, the precedence
field is ignored, so I'm not sure what's going on here :)

--
Nathan Norman
MidcoNet  410 South Phillips Avenue  Sioux Falls, SD
mailto:finn@midco.net           http://www.midco.net
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