1.1 Glossary

This document uses the following terms:

acknowledgment (ACK): A signal passed between communicating processes or computers to signify successful receipt of a transmission as part of a communications protocol.

DirectPlay: A network communication library included with the Microsoft DirectX application programming interfaces. DirectPlay is a high-level software interface between applications and communication services that makes it easy to connect games over the Internet, a modem link, or a network.

DirectPlay 4: A programming library that implements the IDirectPlay4 programming interface. DirectPlay 4 provides peer-to-peer session-layer services to applications, including session lifetime management, data management, and media abstraction. DirectPlay 4 first shipped with the DirectX 6 multimedia toolkit. Later versions continued to ship up to, and including, DirectX 9. DirectPlay 4 was subsequently deprecated. The DirectPlay 4 DLL continues to ship in current versions of Windows operating systems, but the development library is no longer shipping in Microsoft development tools and software development kits (SDKs).

DirectX runtime: A set of libraries created for the family of Windows operating systems that provide interfaces to ease the development of video games.

DirectX Software Development Kit (DirectX SDK): A set of libraries, called the DirectX runtime, and supporting infrastructure for building applications for those libraries.

game: An application that uses a DirectPlay protocol to communicate between computers.

game session: The metadata associated with the collection of computers participating in a single instance of a computer game.

host: In DirectPlay, the computer responsible for responding to DirectPlay game session enumeration requests and maintaining the master copy of all the player and group lists for the game. One computer is designated as the host of the DirectPlay game session. All other participants in the DirectPlay game session are called peers. However, in peer-to-peer mode the name table entry representing the host of the session is also marked as a peer.

Internetwork Packet Exchange (IPX): A protocol that provides connectionless datagram delivery of messages. See [IPX].

maximum transmission unit (MTU): The size, in bytes, of the largest packet that a given layer of a communications protocol can pass onward.

payload: The data that is transported to and from the application that is using either the DirectPlay 4 protocol or DirectPlay 8 protocol.

peer: In DirectPlay, a player within a DirectPlay game session that has an established connection with every other peer in the game session, and which is not performing game session management duties. The participant that is managing the game session is called the host.

peer-to-peer: A server-less networking technology that allows several participating network devices to share resources and communicate directly with each other.

player: A person who is playing a computer game. There can be multiple players on a computer participating in any given game session. See also name table.

player ID: A 32-bit integer that uniquely represents a player.

round-trip: A process that imports data and then exports that data without data loss.

sequence ID: A monotonically increasing 8-bit identifier for packets. This is typically represented as a field named bSeq in packet structures.

serial link (or serial transport): Running the DXDiag application over a null modem cable connecting two computers. See also modem link.

service provider: A module that abstracts details of underlying transports for generic DirectPlay message transmission. Each DirectPlay message is transmitted by a DirectPlay service provider. The service providers that shipped with DirectPlay 4 are modem, serial, IPX, and TCP/IP.

session layer: The fifth layer in the Open Systems Interconnect (OSI) architectural model as defined by the International Organization for Standardization (ISO). The session layer is used for establishing a communication session, implementing security, and performing authentication. The session layer responds to service requests from the presentation layer and issues service requests to the transport layer.

throttling: The reduction in the rate of sending data when a network link saturation condition is detected.

tick count: In DirectPlay, the count from when the system was booted, in milliseconds.

Transmission Control Protocol (TCP): A protocol used with the Internet Protocol (IP) to send data in the form of message units between computers over the Internet. TCP handles keeping track of the individual units of data (called packets) that a message is divided into for efficient routing through the Internet.

User Datagram Protocol (UDP): The connectionless protocol within TCP/IP that corresponds to the transport layer in the ISO/OSI reference model.

user message: A message that is sent between instances of an application using the DirectPlay network library as a transport.

MAY, SHOULD, MUST, SHOULD NOT, MUST NOT: These terms (in all caps) are used as defined in [RFC2119]. All statements of optional behavior use either MAY, SHOULD, or SHOULD NOT.