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See: 2 on datatracker.ietf.org

The title of this RFC is “Host Software.”

RFC 2 was published on April 7, 1969, shortly after RFC 1, and was also written by Steve Crocker. The document builds on the ideas presented in RFC 1 and focuses on elaborating the development of host software for the ARPANET, the predecessor to the modern internet. The goal of RFC 2 was to further outline the functions that host software needed to perform in order to communicate effectively with the Interface Message Processors (IMPs) in the network. While RFC 1 provided an introduction to the concept of host responsibilities, RFC 2 dives deeper into the specific technical considerations required for host-to-host communication. The related RFC is RFC 2, which expands on the foundational concepts of ARPANET host software. https://en.wikipedia.org/wiki/ARPANET https://tools.ietf.org/html/rfc2

One of the key points in RFC 2 is the focus on the software’s ability to interact with the IMPs. The IMPs managed the packet switching within the ARPANET, but it was the responsibility of the host software to manage tasks such as data formatting, error detection, and establishing communication sessions. RFC 2 emphasized the need for host software to be both efficient and flexible, so it could handle the various tasks that would be necessary for different types of data transmission over the network. The related RFC is RFC 791, which formalizes the role of IP in packet-switched networks like the ARPANET. https://en.wikipedia.org/wiki/Packet_switching https://tools.ietf.org/html/rfc791

Error control and message sequencing were significant concerns discussed in RFC 2. For successful communication between hosts, it was crucial to ensure that messages arrived in the correct order and without corruption. The document describes the need for hosts to handle retransmission of lost or corrupted packets, laying the groundwork for error detection and correction techniques that would become key components of later protocols, such as the Transmission Control Protocol (TCP). The related RFC is RFC 793, which defines TCP and its mechanisms for ensuring reliable communication. https://en.wikipedia.org/wiki/Transmission_Control_Protocol https://tools.ietf.org/html/rfc793

RFC 2 also discusses the process of establishing communication sessions between hosts. In this early stage of network development, the procedure for initiating and terminating sessions was still being defined. The host software needed to be able to request a connection, maintain the session for the duration of the data transfer, and then cleanly terminate the connection. This would later become an integral part of the connection-oriented communication model seen in TCP, where a three-way handshake is used to establish a connection and ensure both sides are ready to communicate. The related RFC is RFC 793, which formalizes the three-way handshake process used by TCP. https://en.wikipedia.org/wiki/Three-way_handshake https://tools.ietf.org/html/rfc793

An important aspect of RFC 2 is the emphasis on cooperation between host computers on the ARPANET. At the time, there were a variety of different computer systems and architectures in use, and it was essential that the host software be able to communicate across these diverse platforms. The document outlines the importance of standardizing certain aspects of host software to ensure interoperability, even as individual hosts might implement their own internal processes differently. This theme of interoperability remains a cornerstone of modern networking standards. The related RFC is RFC 1122, which outlines the requirements for internet hosts and their role in maintaining interoperability across networks. https://en.wikipedia.org/wiki/Internet_Standard https://tools.ietf.org/html/rfc1122

RFC 2 also introduced the concept of data formatting and transmission control for host-to-host communication. It emphasized the need for a uniform method of data representation to ensure that all hosts could interpret the data being transmitted, regardless of their internal architectures. This foresight led to the development of various data representation standards and protocols, such as External Data Representation (XDR), which ensures that data can be exchanged between systems with different architectures. The related RFC is RFC 4506, which defines XDR and its use in network communication. https://en.wikipedia.org/wiki/External_Data_Representation https://tools.ietf.org/html/rfc4506

RFC 2 highlights the importance of ensuring efficient resource usage in host software, particularly with respect to memory and processing power. Since early computers had limited resources, the host software needed to be optimized to handle communication without overwhelming the system. This focus on resource efficiency influenced later developments in protocol design, where minimizing overhead and ensuring scalability became key considerations in the growth of the internet. The related RFC is RFC 2616, which discusses the efficiency and scalability of the HTTP protocol, a later evolution of ARPANET concepts. https://en.wikipedia.org/wiki/Hypertext_Transfer_Protocol https://tools.ietf.org/html/rfc2616

Overall, RFC 2 built on the foundational ideas presented in RFC 1 and provided more technical detail on how host software should function to support the emerging ARPANET. It set the stage for the development of more complex protocols and standards, many of which continue to underpin the modern internet. The RFC series, which RFC 2 helped shape, remains a vital mechanism for documenting and improving networking technologies. The related RFC is RFC 2026, which outlines the process by which RFCs are developed and promoted to internet standards. https://en.wikipedia.org/wiki/Internet_Standards_Process https://tools.ietf.org/html/rfc2026

The title of this RFC is “Host Software.” RFC 2 serves as an important early document in the development of host software for the ARPANET. It elaborates on the functions required for host-to-host communication, including error control, message sequencing, session establishment, and resource efficiency. These ideas laid the groundwork for future protocol development, particularly in the areas of error detection, session management, and interoperability. RFC 2 is a key part of the early RFC series that shaped the technical standards for what would eventually become the modern internet.