This RFC is part of a pair that defines and discusses the requirements for Internet host software. It covers the communication protocol layers: link layer, IP layer, and transport layer. Its companion RFC covers application and support protocols. The document outlines the requirements for Internet host software, including the link, IP, and transport layers. It incorporates by reference, amends, corrects, and supplements the primary protocol standards documents. The document includes a detailed discussion of the requirements for each protocol layer, including the link layer, IP layer, and transport layer. It also discusses the architectural assumptions of the Internet, the robustness principle, error logging, and configuration. The document emphasizes the importance of robustness, error handling, and configuration in ensuring interoperability across the Internet. It also discusses the requirements for embedded gateway code and the need for host software to be compatible with a wide range of network environments. The document is intended to guide vendors, implementors, and users of Internet communication software. It represents the consensus of a large body of technical experience and wisdom from the Internet research and vendor communities. The document includes a detailed discussion of the requirements for each protocol layer, including the link layer, IP layer, and transport layer. It also discusses the architectural assumptions of the Internet, the robustness principle, error logging, and configuration. The document emphasizes the importance of robustness, error handling, and configuration in ensuring interoperability across the Internet. It also discusses the requirements for embedded gateway code and the need for host software to be compatible with a wide range of network environments. The document is intended to guide vendors, implementors, and users of Internet communication software.This RFC is part of a pair that defines and discusses the requirements for Internet host software. It covers the communication protocol layers: link layer, IP layer, and transport layer. Its companion RFC covers application and support protocols. The document outlines the requirements for Internet host software, including the link, IP, and transport layers. It incorporates by reference, amends, corrects, and supplements the primary protocol standards documents. The document includes a detailed discussion of the requirements for each protocol layer, including the link layer, IP layer, and transport layer. It also discusses the architectural assumptions of the Internet, the robustness principle, error logging, and configuration. The document emphasizes the importance of robustness, error handling, and configuration in ensuring interoperability across the Internet. It also discusses the requirements for embedded gateway code and the need for host software to be compatible with a wide range of network environments. The document is intended to guide vendors, implementors, and users of Internet communication software. It represents the consensus of a large body of technical experience and wisdom from the Internet research and vendor communities. The document includes a detailed discussion of the requirements for each protocol layer, including the link layer, IP layer, and transport layer. It also discusses the architectural assumptions of the Internet, the robustness principle, error logging, and configuration. The document emphasizes the importance of robustness, error handling, and configuration in ensuring interoperability across the Internet. It also discusses the requirements for embedded gateway code and the need for host software to be compatible with a wide range of network environments. The document is intended to guide vendors, implementors, and users of Internet communication software.