Revision Information: This is a revised manual.
Operating Systems: OpenVMS Alpha Versions 6.2, 7.0, 7.1 OpenVMS VAX Versions 6.2, 7.0, 7.1
Software Version:
DIGITAL TCP/IP Services
for OpenVMS Version 4.2
Digital Equipment Corporation Maynard, Massachusetts
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Possession, use, or copying of the software described in this publication is authorized only pursuant to a valid written license from DIGITAL or an authorized sublicensor.
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© Digital Equipment Corporation 1997. All rights reserved.
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ZK6523
This document is available on CD-ROM.
An open communications standard defined by the worldwide networking community, TCP/IP consists of numerous applications, routing, transport, and network management protocols. These protocols enable any connected host to communicate with any other connected host, without needing to know details about the other host or the intervening network topology. Computers and networks from different manufacturers running different operating systems can interoperate seamlessly.
This book describes DIGITAL's implementation of TCP/IP for the OpenVMS operating system --- DIGITAL TCP/IP Services for OpenVMS, also known as UCX. Chapters 1--4 describe the key concepts of TCP/IP as they relate to the protocols supported by the UCX product. Chapters 5 and 6 provide specific guidelines for system and network managers to plan an internet with the DIGITAL TCP/IP Services for OpenVMS product. The glossary at the end of this book defines many networking and TCP/IP terms used throughout the UCX document set.
This book is for anyone familiar with OpenVMS, but new to the TCP/IP environment who needs an overview of the key components of the DIGITAL TCP/IP Services for OpenVMS product.
See the DIGITAL TCP/IP Services for OpenVMS User's Guide for more detailed user information and the DIGITAL TCP/IP Services for OpenVMS Management guide for more detailed system and network management information.
This book contains the following chapters, an appendix, and a glossary.
Table 1 outlines the documents available to you with this version of DIGITAL TCP/IP Services for OpenVMS.
| Manual | Contents |
|---|---|
| DIGITAL TCP/IP Services for OpenVMS Concepts and Planning |
This manual provides conceptual information about networking and the
TCP/IP protocol. This manual also provides a description of DIGITAL's
implementation of the Berkeley Internet Name Domain (BIND) service and
the Network File System (NFS). It also outlines general planning issues
to consider before configuring your system to use the DIGITAL TCP/IP
Services for OpenVMS software.
This manual also describes the manuals in the documentation set and provides a glossary of terms and acronyms for the DIGITAL TCP/IP Services for OpenVMS software product. It also documents how to contact the InterNIC Registration Service to register domains and access Request for Comments (RFCs). |
| DIGITAL TCP/IP Services for OpenVMS Release Notes |
This text file describes new features and changes to the software
including installation, upgrade, configuration, and compatibility
information. These notes also describe new and existing software
problems and restrictions, and software and documentation corrections.
Print this text file at the beginning of the installation procedure and read it before you install DIGITAL TCP/IP Services for OpenVMS. |
| DIGITAL TCP/IP Services for OpenVMS Installation and Configuration | This manual explains how to install and configure the DIGITAL TCP/IP Services for OpenVMS layered application product. |
| DIGITAL TCP/IP Services for OpenVMS User's Guide | This manual introduces the user services available with DIGITAL TCP/IP Services for OpenVMS such as remote file operations, E-mail, TELNET, TN3270, and network printing. This manual also explains how to use these services to communicate with systems on private internets or on the worldwide Internet. |
| DIGITAL TCP/IP Services for OpenVMS Management |
This manual describes how to manage a corporate internet that uses the
DIGITAL TCP/IP Services for OpenVMS product. This manual also explains
the kernel software, applications, and network services, from a system
management perspective.
Use this manual with the DIGITAL TCP/IP Services for OpenVMS Management Command Reference manual. |
| DIGITAL TCP/IP Services for OpenVMS Management Command Reference |
This manual describes the DIGITAL TCP/IP Services for OpenVMS
management commands.
Use this manual with the DIGITAL TCP/IP Services for OpenVMS Management manual. |
| DIGITAL TCP/IP Services for OpenVMS ONC RPC Programming | This manual presents an overview of high-level programming using open network computing remote procedure calls (ONC RPC). This manual also describes the RPC programming interface and how to use the RPCGEN protocol compiler to create applications. |
| DIGITAL TCP/IP Services for OpenVMS System Services and C Socket Programming | This manual describes how to use C socket and system services routines to build internet application programming interfaces (APIs). |
| DIGITAL TCP/IP Services for OpenVMS eSNMP Programming and Reference | This manual describes the Extensible Simple Network Management Protocol (eSNMP), the eSNMP application programming interface (API), and how to build additional subagents to manage vendor-specific equipment. |
For additional information about the DIGITAL TCP/IP Services for OpenVMS products and services, access the DIGITAL OpenVMS World Wide Web site at the following URL:
http://www.openvms.digital.com
You might also find the Internetworking with TCP/IP: Principles, Protocols, and Architecture, by Douglas Comer useful if you are looking for a comprehensive overview of the TCP/IP protocol suite.
This manual uses the following terminology:
For a complete list of acronyms used throughout this and other manuals in the DIGITAL TCP/IP Services for OpenVMS documentation set, see the glossary in this book.
All IP addresses in this book represent fictitious addresses. The following conventions apply to this book.
| Convention | Meaning |
|---|---|
| UPPERCASE TEXT | Indicates names of OpenVMS and UCX commands, options, utilities, files, directories, hosts, and users. |
| lowercase special type | Indicates UNIX system output or user input, commands, options, files, directories, utilities, hosts, and users. |
| italic type | Indicates a variable. |
| [Return] | Indicates that you press the Return key. |
| [Ctrl/] x | Indicates that you press the Control key while you press the key noted by x. |
| [ ] | In command format descriptions, indicates optional elements. You can enter as many as you want. |
| { } | In command format descriptions, indicates you must enter at least one listed element. |
DIGITAL welcomes your comments on this manual or any of the DIGITAL TCP/IP Services for OpenVMS documents. Send us your comments through any of the following channels:
| Internet | openvmsdoc@zko.mts.dec.com |
| Fax | 603 884-0120, Attention: OSSG Documentation, ZKO3-4/U08 |
|
OSSG Documentation Group, ZKO3-4/U08
110 Spit Brook Rd. Nashua, NH 03062-2698 |
Use the following table to order additional documentation or information. If you need help deciding which documentation best meets your needs, call 800-DIGITAL (800-344-4825).
| Location | Call | Fax | Write |
|---|---|---|---|
| U.S.A. |
DECdirect
800-DIGITAL 800-344-4825 |
Fax: 800-234-2298 |
Digital Equipment Corporation
Mailstop: TAY2-2/11D 153 Taylor Street Littleton, MA 01460 |
| Puerto Rico | 787-781-0505 | Fax: 787-749-8300 | Local DIGITAL subsidiary |
| Canada |
DTN: 621-6005
800-DIGITAL |
Fax: 613-592-1946 |
Digital Equipment of Canada, Ltd.
Box 13000 Kanata, Ontario, Canada K2K2A6 Attn: CICC |
| International | --- | --- |
Local DIGITAL subsidiary or
approved distributor |
| Internal Orders |
DTN: 261-2010
603-791-2010 |
Fax: 800-741-6970 |
U.S. Software Supply Business
Digital Equipment Corporation 8 Cotton Road Nashua, NH 03063-1260 |
The DIGITAL TCP/IP Services for OpenVMS product (also known as UCX) is the OpenVMS implementation of the industry-standard TCP/IP suite of communications protocols. With TCP/IP, heterogeneous networks can interconnect, making it possible for users to connect to remote hosts in many ways:
Internetworking with TCP/IP hides the hardware details of each individual network and allows computers to communicate independently of their physical network connections. TCP/IP provides both a standard transport mechanism and full-duplex, reliable, stream communication services for software applications.
The DIGITAL TCP/IP Services for OpenVMS product provides
interoperability and resource sharing between OpenVMS systems, UNIX
systems, and other systems that support the TCP/IP protocol suite and
Sun Microsystems' Network File System (NFS). TCP/IP systems and other
internet hosts share data and resources by using standard TCP/IP
protocols over a number of network hardware configurations: Ethernet,
Fiber Distributed Data Interface (FDDI), Token Ring, and asynchronous
transfer mode (ATM).
1.1 TCP/IP Defined: Requests for Comments
TCP/IP evolved from the U.S. Government's need to connect many different networks regardless of their hardware architecture, operating system, or subnetwork technology. The resulting internetwork needed to be able to route data between networks, tolerate routing errors, and easily add new subnetworks. From a simple four-node entity in 1969 to today's Worldwide Internet connecting thousands of networks and millions of computers, TCP/IP has become the communications standard of the Internet.
TCP/IP is an open system interconnection. Although monitored by a number of organizations, no one entity owns TCP/IP; its specifications are publicly available and constantly growing as communications requirements evolve.
The process by which the specifications evolve is through a mechanism called Requests for Comments or, more commonly, RFCs. Basically, when someone has an idea for a new or improved capability for TCP/IP, he or she writes a proposal, posts it on the Internet, and requests comments from the networking community. After a review and revision cycle, working code is developed and an RFC becomes a standard protocol.
RFCs are available on the Internet from an organization called the
Internet Network Information Center, or InterNIC. Appendix A discusses
the InterNIC and explains how you can get copies of RFCs.
1.2 TCP/IP Architecture
The TCP/IP protocol suite is designed in a fashion similar to that of the OSI layered model. However, the TCP/IP protocol suite has four layers while the OSI model has seven layers. Figure 1-1 shows the relationship between the layers of the two models. As shown in the illustration, the OSI model's Session and Presentation layer functions are fulfilled by the TCP/IP Application layer protocols. Likewise, some of the functions of the OSI Physical layer are handled by the Network Interface layer and the hardware itself in the TCP/IP model.
Figure 1-2 and Table 1-1 outline the layers of the TCP/IP model. Sections 1.3 through 1.6 summarize the protocols.
Figure 1-1 Relationship Between TCP/IP and OSI Models
Figure 1-2 DIGITAL TCP/IP Protocol Architecture
The Network Interface layer of the TCP/IP model (also called the Data Link layer) is responsible for properly sending and receiving communications signals between two communicating hosts through their network interfaces.
The network interface is a software component that communicates with the TCP/IP software and the network controller (the hardware connection between a computer system and a network). UCX supports multiple network interfaces for each physical network controller, which means that a single physical connection can have more than one IP address.
Individual host computers can be connected to many different types of networks such as Ethernet, FDDI, Token Ring, and asynchronous transfer mode (ATM). The Internet device driver, called the BG driver, is the software interface between the OpenVMS operating system and the network device controller for these hardware configurations.
Individual host computers can also connect with other hosts or networks over serial communications lines, which are most commonly telephone connections.
With TCP/IP --- as with any layered networking protocol --- each layer adds header information to the protocol data unit (PDU) from the layer above. Each packet contains a header from the Network Interface layer, followed by a header from the Internet layer, followed by a header from the Transport layer, followed by the application data.
At the Network Interface layer, standard encapsulation of IP packets are defined for the various hardware types. Ethernet, for example, uses the Ethernet frame standard to enclose the data being sent with header fields. Serial line connections use either Serial Line Internet Protocol (SLIP or CSLIP) or Point-to-Point Protocol (PPP).
Serial Line Internet Protocol
SLIP is a simple packet framing protocol. It defines a sequence of characters that frame IP packets on a serial line. It provides no mechanisms for addressing, packet type identification, error detection/correction, or compression. Although limited in scope, SLIP is easy to implement, but transmission speeds are relatively slow. CSLIP (Compressed SLIP) allows for faster transmission by compressing the TCP/IP headers.
For more information on SLIP and CSLIP, see the DIGITAL TCP/IP Services for OpenVMS Management guide.
Point-to-Point Protocol
PPP is more complex than SLIP and CSLIP, but it offers much greater functionality. As described in RFC 1331, PPP consists of three main components:
For more information on PPP, see the DIGITAL TCP/IP Services for OpenVMS Management guide.
1.4 Internet Layer Protocols
The Internet layer provides a connectionless packet delivery service using the Internet Protocol (IP). An IP datagram is a packet that has no delivery receipt and is called connectionless because IP does not maintain state information about successive datagrams. Each datagram is handled independently from all other datagrams.
The DIGITAL TCP/IP Services for OpenVMS product supports the following Internet layer protocols:
IP sends or routes data across the network from its source to its destination by means of internet addressing (an IP address). The IP address identifies the connection between the network controller of a node and the network cable. IP then receives data bits from the network hardware, assembles the bits into an IP datagram, and chooses the best route to send the packet to its destination. IP also fragments and reassembles packets during the routing process.
RIP enables gateways to exchange current routing information about hosts and directly connected networks.
Internet Control Message Protocol
ICMP provides a number of diagnostic functions and handles error and control messages. ICMP reports problems with data delivery to gateways and hosts.
ARP dynamically maps an IP address to a physical hardware address of
the broadcast medium such as Ethernet, FDDI, Token Ring, or PPP. ARP is
limited to a single physical network and to networks that support
hardware broadcast.
1.5 Transport Layer Protocols
The Transport layer protocols provide either connection-oriented or connectionless data stream transmission from one host to another. The Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP) form the bridge between the Application layer functions and Internet layer protocols such as IP.