# IP TOS

The IP Type of Service (TOS) field (also known as DiffServ or DSCP field) is a part of an [IP datagram](/glossary/i/ip_datagram) header, originally meant to describe the purpose of a datagram.

It is used by [Differentiated Services](/glossary/d/diffserv) for the [DiffServ Code Point](/glossary/d/dscp), and the optional [Explicit Congestion Notification](/glossary/i/ip_ecn).