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iptos(4) Kernel Interfaces Manual iptos(4) NAME iptos - Defines the IP Type Of Service (TOS) for FTP and Telnet SYNOPSIS /etc/iptos DESCRIPTION The /etc/iptos file configures the Type Of Service (TOS) of the Inter- net Protocol (IP) used by FTP and Telnet. The TOS field in the Internet datagram is to specify how the datagram should be handled. It is a mechanism to allow control information to have precedence over data. Generally, protocols that are involved in direct interaction with a hu- man should select low delay, while data transfers that involve large blocks of data need high throughput. Finally, high reliability is most important for datagram-based Internet management functions. In the DIGITAL UNIX operating system, the ftp and telnet applications and the ftpd and telnetd daemons allow the configuring of TOS values. These applications check to see if the /etc/iptos file exists; if the file exists, the applications obtain the TOS value from the file and use that value to set the TOS field. If the /etc/iptos file does not exist, the applications default to the following TOS values recommended by RFC1060: Low delay High throughput Low delay Users who want to configure their own TOS values for the TOS field should provide the /etc/iptos file. Note Most IP routers do not differentiate based on TOS, and therefore providing values other than the default would have no affect. Digital does not recommend changing the default values for FTP and Telnet. Each entry should consist of a single line of the form: Application Proto TOS-bits aliases The entry fields contain the following information: The name of an ap- plication TOS entry. The protocol name for which the entry is appro- priate. The TOS value to be set for the entry. A list of aliases that exist for the entry. Items on an entry line are separated by any number of blanks, tabs, or combination of blanks and tabs. A number sign (#) indicates that the rest of the line is a comment and is not interpreted by routines that search the file. Blank lines in the file are ignored. Valid TOS entry names are ftp-control and ftp-data for FTP and telnet for Telnet. The TOS value for the entry should be one of the following hexadecimal numbers, corresponding to TOS bits: Low delay High throughput High re- liability If you need to disable the use of TOS bits, because you are having troubling communicating with a TCP/IP host that doe not conform en- tirely with the IP specification, you can disable the TOS bits by using the the following settings in the /etc/iptos file: # # Format of this file: # Application Proto TOS-bits aliases # ftp-control tcp 0x0 ftp-data tcp 0x0 telnet tcp 0x0 EXAMPLES The following example shows typical entries in the /etc/iptos file: # # Format of this file: # Application Proto TOS-bits aliases # ftp-control tcp 0x10 ftp-data tcp 0x08 telnet tcp 0x10 RELATED INFORMATION RFC1060, ftp(1), telnet(1), ftpd(8), telnetd(8) delim off iptos(4)