IP_TOS(2const)                                                  IP_TOS(2const)

NAME
       IP_TOS - type of service

LIBRARY
       Standard C library (libc, -lc)

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

HISTORY
       Linux 1.0.

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

Linux man-pages 6.17              2025-11-25                    IP_TOS(2const)