TCP/IP for DOS Socket Library Reference

Glossary

Address Resolution Protocol (ARP)

The Intemet protocol that dynamically identifies a high-level Internet address based on a known low-level physical hardware address. ARP broadcasts across a single physical network, but only on networks that support hardware broadcasts.

Application Programming Interface (API)

The set of calls a program uses to obtain services from the operating system (for example, the Socket API).

Attached Resource Computer network (ARCnet)

A high-speed, multi-vendor network.

Datagram

The basic transfer unit on the Internet. A datagram is divided into header and data areas. Every datagram contains the IP addresses of its source and destination. See Packet.

Device driver

A program that takes hardware-independent ~O instructions and converts them into requested operations on specific hardware (for example, ANSI.SYS or LSL.SYS).

Domain Name System (DNS)

A DNS server has network addresses for each computer on a network. A workstation calls a name server to get address information. A DNS server translates symbolic hostnames (for example, Finance) into IP addresses.

Dynamic-Linking Library (DLL)

A compiled version of a library that contains shared routines and functions. Because multiple programs can access the DLL module simultaneously, only one copy of the DLL needs to be present in memory, and the size of executables that access the DLL can be minimized.

Encapsulate

To enclose one complete entity (for example, a UDP datagram or a TCP segment) in the data area of a lower-layer entity such as an IP packet. On the Internet, to encapsulate usually means to carry an IP datagram in a network (hardware) frame.

File Transfer Protocol (FTP)

The Internet standard, application level protocol for transferring files from one computer to another. Usually FTP is implemented in application programs using the Telnet and TCP protocols. The server side requires a client login and password before it honors requests.

Gateway

A special-purpose computer that connects networks and routes packets from one network to another. A gateway translates all seven protocol layers between computers with different upper layer protocols, operating systems, and network media types.

Host Name Database

Contains the names, aliases (optional), and network addresses of the computers on your network.

internet (not capitalized)

Physically, a collection of packet switching networks connected by routers along with protocols that let them function logically as a single large virtual network. See Internet.

Internet (capitalized)

Internet refers specifically to the DARPA Internet and the TCP/IP protocols it uses. The Internet is the collection of networks and routers (including the ARPANET, MILNET, and NFSnet) that use the TCP/IP protocol suite and function as a single, cooperative virtual network. The Internet provides universal connectivity and three levels of network services: unverified, connectionless packet delivery; reliable, full duplex stream delivery; and application level services like electronic mail. See internet.

Internet Control Message Protocol (ICMP)

An integral part of the Internet Protocol (IF) that handles error and control messages. Specifically, gateways and hosts use ICMP to send reports of problems about datagrams back to the original datagram source. ICMP also includes an echo request/reply used to test whether a destination is reachable and responding.

IP address

The Internet Protocol address is a network level (level 3 of the OSI networking reference model) address assigned to each system in a TCP/IP network. It is 4 bytes long.

IP host address

An IP host address is a part of the 4-byte IP address. The IP address can be divided into two logical parts: an IP network address and a local host address. The IP host address is unique for every node on a single network.

IP network address

An IP network address is a part of the 4-byte IP address. The IP address can be divided into two logical parts: an IP network address and a local host address. The IP network address is the same for every node on a single network. The IP network address facilitates routing between Internet networks.

Library

A collection of standardized subroutines that provide programmers with commonly-used processing functions. Programmers make reference to library functions using function calls, and include the library when compiling the program.

Link Services Layer (LSL)

Routes packets between LAN boards with their MLIDs and protocol stacks. The LSL maintains LAN board information, protocol stack information, and ECB information.

Medium Access Control (MAC)

The MAC is the sublayer in between the physical and datalink layers for controlling the use of the network hardware.

Multiple Link Interface Driver (MLID)

Accepts multiple protocol packets. When an MLID device driver receives a packet, the MLID does not interpret the packet; it copies identification information and passes the packet to the Link Support Layer (LSL). MLIDs (LAN drivers) are supplied by Novell, by the network board manufacturer, or a by third-party supplier (for example, a university).

Open Datalink Interface (ODI)

A set of specifications that define the relationships between one or more protocol stacks, the LSL, and one or more MLIDs. These specifications allow multiple communication protocols such as IPX/SPX, TCP/IP, and AppleTalk to share the same driver and adapter.

Packet

A packet is a message that is sent on a point-to-point subnet from one processor to another. Each packet is stored and then forwarded, or packet-switched. The term packet has been losing its distinctness and is sometimes used as a synonym for datagram. See Datagram.

Packet InterNet Groper (PING)

A program used to test the accessibility of destinations by sending them an ICMP echo request and waiting for a reply.

Protocol element

A command for performing FTP operations on the protocol level. After you have established an FTP session, you can enter REMOTEHELP from the FTP prompt. FTP then displays a list of FTP protocol elements recognized by the particular FTP server (for example, USER, PORT, XEXC). Most FTP servers support a subset of available protocol elements. Elements that begin with the letter X are experimental. Refer to RFC 959 for additional information on FTP protocol elements.

Protocol stack

The software modules that take data from an application and transform or encapsulate it for transmission across a network. The stack may have several layers of modules. Each layer provides services to the layer above; each layer requests services from the layer below. Examples of protocol stacks are IPX/SPX, TCP/IP, and OSI.

Reverse Address Resolution Protocol (RARP)

The Internet protocol used by a workstation at startup to find its Internet address from its hardware address. The workstation broadcasts a request that contains its physical hardware address and a server responds by sending the workstation its Internet address.

Router

A router uses a packet's IP destination address to determine which network or network segment is its destination. A router can find the best way to transmit data between networks. This may involve hops across multiple networks. Routers use specialized protocols that let them communicate with each other and advise their peers of available routes, hop counts, time to destination, and router maintenance. Upper layer protocols must be the same.

Runtime

Pertaining to the actual execution of a program. For example, a runtime library is a library that is accessed at the time that a program is executed, as opposed to when the program is compiled.

Server

A node that provides services to other nodes on the network. A server could be a print server and provide print spooling and printer access for other nodes on the network.

Socket

A logical communications device that allows programs on two networked computers to make a connection and transfer data. The sockets interface was popularized by the BSD UNIX operating system, and supports the standard TCP and UDP communications protocols.

TCP/IP Transport software

Software residing in the operating system, including a set of device drivers. These drivers interface with the MLID/ODI drivers at the bottom layer, and support the Berkeley socket APIs and the NetBIOS APIs at the top layer. The Novell TCPnP Transport can support the popular Ethernet (IEEE 802.3) and token ring (IEEE 802.5) network adapters. A set of standard MLID/ODI drivers is included in the NetWare Requester software.

Transmission Control Protocol (TCP)

A virtual circuit connection-oriented protocol.

User Datagram Protocol (UDP)

An unverified (usually called unreliable) connectionless protocol.

Workstation

A node that requests services from other nodes on the network, but does not provide services to other nodes. Some nodes that provide services can be both workstations and servers, but in the context of requesting services, they are workstations.

The following list of abbreviations may be helpful: