Why does UDP have a length field in the header and TCP does not?

Question

Why does UDP have a length field in the header and TCP does not?

I am guessing that the length of the segment in TCP is inferred from the IP header but one should be abl

Answer 1

I thought: As TCP is a stream based protocol, it's ok if its segment be fragmented at . UDP is transaction oriented, if its messages be fragmented at IP layer we need its length to recover it.

Sorry for my poor English.