On Fri, 1 Oct 2021 15:36:18 +0100 Ferruh Yigit <ferruh.yi...@intel.com> wrote:
> Other issues causing confusion is: > * maximum transmission unit (MTU) is payload of the Ethernet frame. And > 'max_rx_pkt_len' is the size of the Ethernet frame. Difference is > Ethernet frame overhead, and this overhead may be different from > device to device based on what device supports, like VLAN and QinQ. > * 'max_rx_pkt_len' is only valid when application requested jumbo frame, > which adds additional confusion and some APIs and PMDs already > discards this documented behavior. > * For the jumbo frame enabled case, 'max_rx_pkt_len' is an mandatory > field, this adds configuration complexity for application. One other issue which DPDK inherits from Linux and BSD is that MTU (Maximum Transmission Unit) is overloaded to mean MRU (Maximum Receive Unit). On Linux, network devices are allowed to receive packets of any size they want. MTU is used as a hint about "you need to accept at least MTU size packets on receive". So MRU >= MTU. In practice, and documentation, MRU and MTU are used synonymously.
