On Thu, 10 Sep 1998, Default Debian Reader wrote:
[ snip ]
: > : 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)
: That book was copyright 1994, i imagine it was printed even before that.
: > but if you are referring to the Type Of Service field, 0xc0 is not a
: > valid choice.
: >
: That is my question, Is it valid because i have seen ip headers with a tos
: of 0xc0 or at least it appeared.
:
: > [ 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 :)
^^^^^^^^^^^^^^^^
Uh, did you read this part? The precedence field is ignored (according
to Stevens, and he seems to know what he's talking about). A value of
0xc0 means that some application is setting the two most significant
precendence bit, and since these are supposedly ignored in IP-land
today, it's no big deal. Weird, but not a huge problem.
--
Nathan Norman
MidcoNet 410 South Phillips Avenue Sioux Falls, SD
mailto:[EMAIL PROTECTED] http://www.midco.net
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