Removing a Restriction on the use of MPLS Explicit NULL

This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited. Abstract The label stack encoding for Multi-protocol Label Switching (MPLS) defines a reserved label value known as "IPv4 Explicit NULL" and a reserved label value known as "IPv6 Explicit NULL". Previously, these labels were only legal when they occurred at the bottom of the MPLS label stack. This restriction is now removed, so that these label values may legally occur anywhere in the stack.