Network byte order

In the open environment of TCP/IP, IP addresses must be defined in terms of the architecture of the machines. Some machine architectures, such as IBM® mainframes, define the lowest memory address to be the high-order bit, which is called big endian. However, other architectures, such as IBM PCs, define the lowest memory address to be the low-order bit, which is called little endian.

Network addresses in a given network must all follow a consistent addressing convention. This convention, known as network byte order, defines the bit-order of network addresses as they pass through the network. The TCP/IP standard network byte order is big-endian. In order to participate in a TCP/IP network, little-endian systems usually bear the burden of conversion to network byte order.

Note: The socket interface does not handle application data bit-order differences. Application writers must handle these bit order differences themselves.