IP_TOS(2const) — Linux manual page

IP_TOS(2const)                                             IP_TOS(2const)

NAME         top

       IP_TOS - type of service

LIBRARY         top

       Standard C library (libc, -lc)

SYNOPSIS         top

       #include <netinet/in.h>  /* Definition of IP* constants */
       #include <sys/socket.h>

       int setsockopt(int sockfd, IPPROTO_IP, IP_TOS,
                      const int *tos, sizeof(int));
       int getsockopt(int sockfd, IPPROTO_IP, IP_TOS,
                      int *tos, sizeof(int));

DESCRIPTION         top

       Set or receive the Type-Of-Service (TOS) field that is sent with
       every IP packet originating from this socket.  It is used to
       prioritize packets on the network.

       There are some standard TOS flags defined:

       IPTOS_LOWDELAY
              to minimize delays for interactive traffic,

       IPTOS_THROUGHPUT
              to optimize throughput,

       IPTOS_RELIABILITY
              to optimize for reliability,

       IPTOS_MINCOST
              should be used for "filler data" where slow transmission
              doesn't matter.

       At most one of these TOS values can be specified.  Other bits are
       invalid and shall be cleared.

       Linux sends IPTOS_LOWDELAY datagrams first by default, but the
       exact behavior depends on the configured queueing discipline.

       Some high-priority levels may require superuser privileges (the
       CAP_NET_ADMIN capability).

ERRORS         top

       See IPPROTO_IP(2const).  See setsockopt(2).  See ip(7).

HISTORY         top

       Linux 1.0.

SEE ALSO         top

       IPPROTO_IP(2const), setsockopt(2), ip(7)

COLOPHON         top

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Linux man-pages 6.18            2025-11-25                 IP_TOS(2const)

Pages that refer to this page: IP_HDRINCL(2const),  IPPROTO_IP(2const),  IP_RECVTOS(2const)

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