Nmap Announce mailing list archives
Re: Precedence field value in ICMP Error Messages with LINUX Kernels 2.2.x & 2.4
From: "Mikhail Evstiounin" <evstiounin () telerama com>
Date: Thu, 19 Oct 2000 22:06:05 -0400
----- Original Message ----- From: "Ofir Arkin" <ofir () itcon-ltd com>
This is a corrected post for the post I have sent on 14.10.2000 Titled "TOS Field value in ICMP Error Messages with LINUX Kernels 2.2.x & 2.4". --------------------------------------------------------------- Each IP Datagram has an 8-bit field called the “TOS Byte”, which represents the IP support for prioritization and Type-of-Service handling.
Ofir, take a look at RFC2474 - this is a proposed standard (from December of 1998 -- we will see in December if it becomes a complete standard). It completely redefines ToS field in IPv4. And it's a native field for IPv6.
The “TOS Byte” consists of three fields. The “Precedence field”, which is 3-bit long, is intended to prioritize the IP Datagram. It has eight levels of prioritization. Higher priority traffic should be sent before lower priority traffic. The second field, 4 bits long, is the “Type-of-Service” field. It is intended to describe how the network should make tradeoffs between throughput, delay, reliability, and cost in routing an IP Datagram. The last field, the “MBZ” (most be zero), is unused and most be zero. Routers and hosts ignore this last field. This field is 1 bit long.
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Current thread:
- Precedence field value in ICMP Error Messages with LINUX Kernels 2.2.x & 2.4 Ofir Arkin (Oct 19)
- Re: Precedence field value in ICMP Error Messages with LINUX Kernels 2.2.x & 2.4 Mikhail Evstiounin (Oct 19)