HTTP/1.1 allows a client to request that only part (a range of) the response entity be included within the response. HTTP/1.1 uses range units in the Range (section 14.36) and Content-Range (section 14.17) header fields. An entity may be broken down into subranges according to various structural units.
range-unit = bytes-unit | other-range-unit
bytes-unit = "bytes"
other-range-unit = token
The only range unit defined by HTTP/1.1 is "bytes". HTTP/1.1 implementations may ignore ranges specified using other units. HTTP/1.1 has been designed to allow implementations of applications that do not depend on knowledge of ranges.