A method, comprising: utilizing, at a network interface device, a physical layer, PHY, protocol data unit, PPDU, maximum duration such that, A) when operating in a first mode of operation, a data unit i) defined by a protocol in a layer above a PHY protocol in a protocol stack and ii) having a maximum length defined by the protocol above the PHY protocol will fit entirely within a single PPDU at a lowest possible data rate in the first mode of operation, and B) when operating in a second mode of operation, the data unit i) defined by the protocol in the layer above the PHY protocol and ii) having the maximum length defined by the protocol above the PHY protocol will not fit entirely within a single PPDU at a lowest possible data rate in the second mode of operation; receiving medium access control, MAC, service data units, MSDUs; generating, at the network interface, MPDUs to include the MSDUs; when operating in the second mode of operation, generating MPDUs includes, for each received MSDU, determining whether a length of the MSDU exceeds a fragmentation threshold, fragmenting the MSDU into multiple MPDUs when it is determined that the length of the MSDU exceeds the fragmentation threshold, and generating a single MPDU that includes the MSDU when it is determined that the length of the MSDU does not exceed the fragmentation threshold, wherein the fragmentation threshold is determined based on a maximum MPDU size that will fit entirely within a single PPDU at the lowest possible data rate in the second mode of operation; generating, at the network interface device, PHY protocol data units, PPDUs, to include the MPDUs, wherein each PPDU has a duration less than or equal to the PPDU maximum duration; and causing the PPDUs to be transmitted. utilizing, at a network interface device, a physical layer, PHY, protocol data unit, PPDU, maximum duration such that, A) when operating in a first mode of operation, a data unit i) defined by a protocol in a layer above a PHY protocol in a protocol stack and ii) having a maximum length defined by the protocol above the PHY protocol will fit entirely within a single PPDU at a lowest possible data rate in the first mode of operation, and B) when operating in a second mode of operation, the data unit i) defined by the protocol in the layer above the PHY protocol and ii) having the maximum length defined by the protocol above the PHY protocol will not fit entirely within a single PPDU at a lowest possible data rate in the second mode of operation; receiving medium access control, MAC, service data units, MSDUs; generating, at the network interface, MPDUs to include the MSDUs; when operating in the second mode of operation, generating MPDUs includes, for each received MSDU, determining whether a length of the MSDU exceeds a fragmentation threshold, fragmenting the MSDU into multiple MPDUs when it is determined that the length of the MSDU exceeds the fragmentation threshold, and generating a single MPDU that includes the MSDU when it is determined that the length of the MSDU does not exceed the fragmentation threshold, wherein the fragmentation threshold is determined based on a maximum MPDU size that will fit entirely within a single PPDU at the lowest possible data rate in the second mode of operation; generating, at the network interface device, PHY protocol data units, PPDUs, to include the MPDUs, wherein each PPDU has a duration less than or equal to the PPDU maximum duration; and causing the PPDUs to be transmitted. generating MPDUs includes, for each received MSDU, determining whether a length of the MSDU exceeds a fragmentation threshold, fragmenting the MSDU into multiple MPDUs when it is determined that the length of the MSDU exceeds the fragmentation threshold, and generating a single MPDU that includes the MSDU when it is determined that the length of the MSDU does not exceed the fragmentation threshold, wherein the fragmentation threshold is determined based on a maximum MPDU size that will fit entirely within a single PPDU at the lowest possible data rate in the second mode of operation; determining whether a length of the MSDU exceeds a fragmentation threshold, fragmenting the MSDU into multiple MPDUs when it is determined that the length of the MSDU exceeds the fragmentation threshold, and generating a single MPDU that includes the MSDU when it is determined that the length of the MSDU does not exceed the fragmentation threshold, wherein the fragmentation threshold is determined based on a maximum MPDU size that will fit entirely within a single PPDU at the lowest possible data rate in the second mode of operation; generating, at the network interface device, PHY protocol data units, PPDUs, to include the MPDUs, wherein each PPDU has a duration less than or equal to the PPDU maximum duration; and causing the PPDUs to be transmitted.