🚀 go-pugleaf

Actually the term "unreliable" has three different meanings in TCP/IP,
depending upon whether you're using it to describe IP, UDP, or the
many buggy implementations that exist -:).

  telnet, ftp     NFS, name service
     TCP		UDP
     --------IP-----------

IP does checksums only for the IP header.  The main information this
includes is the source and destination address.  The IP level does not
check the data.  Thus the IP level is "unreliable" both in the sense
that it does not guarantee delivery and in the sense that it may give
you bad data.  There are some applications written directly on top
of IP, not using TCP or UDP.  They have to contend with unreliable
in its full definition.

TCP does checksums for all of the data.  It also does retransmissions
as necessary to make sure all the data arrives exactly once.  Thus
Protocols written on top of TCP don't have to worry about this, and
can treat TCP as providing reliable data.

UDP normally checksums its data.  It does not guarantee arrival.  Thus
applications written on top of UDP can assume that what they get is
uncorrupted, but they may have to do retransmission at the application
level, because delivery is not guaranteed.  So UDP is unreliable in
the sense of delivery but not in the sense of corruption.  Note
however that it is possible to turn off checksumming in UDP.  The most
infamous case is Sun, which turns it off for NFS (for performance
reasons -- it even makes sense when you use NFS the way they
intended).