TCP Processing of the IPv4 Precedence Field

This memo describes a conflict between TCP [RFC793] and DiffServ [RFC2475] on the use of the three leftmost bits in the TOS octet of an IPv4 header [RFC791]. In a network that contains DiffServ-capable nodes, such a conflict can cause failures in establishing TCP connections or can cause some established TCP connections to be reset undesirably. This memo proposes a modification to TCP for resolving the conflict.