diff options
Diffstat (limited to 'man7/udp.7')
| -rw-r--r-- | man7/udp.7 | 24 |
1 files changed, 17 insertions, 7 deletions
diff --git a/man7/udp.7 b/man7/udp.7 index b55b5ba7fe..9268d86e66 100644 --- a/man7/udp.7 +++ b/man7/udp.7 @@ -69,13 +69,23 @@ When the flag is set on sending the destination address must refer to an local interface address and the packet is only sent to that interface. -UDP fragments a packet when its total length exceeds the interface MTU -(Maximum Transmission Unit). -A more network friendly alternative is to use path MTU discovery -as described in the -.B IP_MTU_DISCOVER -section of -.BR ip (7). +By default Linux UDP does path MTU (Maximum Transmission Unit) discovery. +This means the kernel +will keep track of the MTU to a specific target IP address and return +.I EMSGSIZE +when a UDP packet write exceeds it. +When this happens the application should decrease the packet size. +Path MTU discovery can be also turned off using the +.B IP_MTU_DISCOVER +socket option or the +.B ip_no_pmtu_disc +sysctl, see +.BR ip(7) +for details. +When turned off UDP will fragment outgoing UDP packets +that exceed the interface MTU. +However disabling it is not recommended +for performance and reliability reasons. .SH "ADDRESS FORMAT" UDP uses the IPv4 |