"Introduction Layered Coding Transport (LCT) provides transport level support for reliable content delivery and stream delivery protocols. Layered Coding Transport is specifically designed to support protocols using IP multicast@ but it also provides support to protocols that use unicast. Layered Coding Transport is compatible with congestion control that provides multiple rate delivery to receivers and is also compatible with coding techniques that provide reliable delivery of content. This document describes a building block as defined in [RFC3048]. This document is a product of the IETF RMT WG and follows the general guidelines provided in [RFC3269]. [RFC3451]@ which was published in the ""Experimental"" category and which is obsoleted by this document@ contained a previous version of the protocol. This Proposed Standard specification is thus based on and backwards compatible with the protocol defined in [RFC3451] updated according to accumulated experience and growing protocol maturity since its original publication. Said experience applies both to this specification itself and to congestion control strategies related to the use of this specification. The key words ""MUST""@ ""MUST NOT""@ ""REQUIRED""@ ""SHALL""@ ""SHALL NOT""@ ""SHOULD""@ ""SHOULD NOT""@ ""RECOMMENDED""@ ""MAY""@ and ""OPTIONAL"" in this document are to be interpreted as described in [RFC2119]."