Constant PACKET_BUF_SIZE 

pub const PACKET_BUF_SIZE: usize = _; // 1_514usize

Size of the buffer in a PacketBuf, in bytes.

This is the largest frame that can be sent or received, headers included.

Not configurable yet: it is 1514 (the largest Ethernet frame without the FCS) rounded up to a multiple of PACKET_BUF_ALIGN.