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Communication functions such as electronic mail are vital both within an organizational internetwork and across the worldwide Internet. The electronic mail components of DIGITAL TCP/IP Services for OpenVMS are:
SMTP is the TCP/IP standard protocol for transferring electronic mail messages from one system to another. SMTP specifies how systems interact and the format of the mail messages they exchange. The product's SMTP implementation uses the OpenVMS mail facility.
The OpenVMS mail facility automatically recognizes an SMTP host address, as shown in the following example:
$ MAIL MAIL> SEND To: jones@widgets.com |
The DIGITAL TCP/IP Services for OpenVMS Post Office Protocol (POP) server and the SMTP server work together to provide a reliable mail service.
POP is a mail repository used primarily by PCs to ensure that mail is accepted even when the PC is turned off. With POP, the PC user need not be concerned with configuring the system as an SMTP server. The user logs into the client system's mail application, and the POP server forwards any new mail messages from the OpenVMS NEWMAIL folder.
The POP server is an OpenVMS implementation of the Post Office
Protocol, Version 3 (RFC 1725), and is based on the Indiana University
POP server (IUPOP3).
1.6.5 Network Services
The DIGITAL TCP/IP Services for OpenVMS product provides services that are used by system or network managers rather than directly by users. The following TCP/IP Services components let the system or network manager provide consistent, reliable, and efficient network services with minimal interruption:
Simple Network Management Protocol (SNMP)
SNMP is a vendor-independent network management standard for managing network components in a TCP/IP network.
The TCP/IP Services product implements SNMP Version 2c using an extensible SNMP (eSNMP) architecture. The product provides a master agent and two subagents to implement data items from standard Management Information Bases (MIBs): MIB-II (RFC 1213) and the Host Resources MIB (RFC 1514). Depending on how you configure your host, an SNMP management station can obtain information about your host and perform updates on your host's MIB data items. For SNMP configuration, operation, and restriction information, see the DIGITAL TCP/IP Services for OpenVMS Management manual, DIGITAL TCP/IP Services for OpenVMS Management Command Reference manual and DIGITAL TCP/IP Services for OpenVMS Release Notes.
The TCP/IP Services product also includes an eSNMP application programming interface (API) and related tools. These features help customers create custom subagents to access their own software or hardware parameters through SNMP. For more information about the eSNMP API, see the DIGITAL TCP/IP Services for OpenVMS Release Notes and the DIGITAL TCP/IP Services for OpenVMS eSNMP Programming and Reference manual.
The Network Time Protocol (NTP) provides a means to synchronize time and coordinate time distribution throughout a TCP/IP network. Time synchronization is important in client/server computing. For example, systems that share common databases require coordinated transaction processing and time-stamping of instrumental data. Synchronized timekeeping means that hosts with accurate system time send accurate time quotes to each other. Hosts running NTP act as time servers, clients, or both server and client.
The TCP/IP Services product implements NTP Version 3 (xNTP) and provides several utility programs that help you manage and make changes to the NTP server. These utilities include:
See the DIGITAL TCP/IP Services for OpenVMS Management manual for more information about configuring and managing NTP.
The Domain Name Service (DNS) is an Internet service that maintains and distributes information about Internet hosts. DNS consists of several databases that store host names and host IP addresses. With DNS, there is no central storage of data --- no one server knows everything about all the Internet domains. In UNIX environments, DNS is implemented by the Berkeley Internet Name Domain (BIND) software. The TCP/IP Services product implements a BIND server based on the Internet Software Consortium's (ISC) BIND 8. The BIND 8 implementation provides new configuration syntax and a new format for configuring the BIND name server.
BIND is a lookup service for the Internet. BIND is divided into two components: a resolver and a name server. The resolver queries a name server, and the name server responds to a resolver query.
| BIND Component | Function |
|---|---|
| BIND resolver | Client software that requests host names, addresses, and other network information from BIND servers that maintain extensive information, rather than from the more limited local database. |
| BIND server | Server software that translates host names into numeric Internet addresses and numeric Internet addresses into host names. BIND servers maintain databases of host names, addresses, mail records, text records, and other network objects. When client systems require this information, they query the servers with the BIND resolver. |
For more information about BIND and planning your DNS environment, see Chapter 3, Chapter 5, and the DIGITAL TCP/IP Services for OpenVMS Management manual.
Internet hosts can simultaneously run multiple industry-standard and custom-developed services. With the portmapper, you do not need to preconfigure client applications with port numbers for each service. Instead, each server registers itself and the portmapper allocates the port. Each server process listens for connections on a designated port.
The portmapper maintains a database of the following:
Remote clients request port numbers to connect to particular applications.
The TCP/IP Services product implements the UNIX internet daemon inetd function, through the security and event and error logging of the auxiliary server process. The auxiliary server simplifies application writing and manages overhead by reducing simultaneous server processes on the system. In addition, the auxiliary server does the following:
Dynamic Host Configuration Protocol
DHCP is an extension (or superset) of BOOTP that allows for the centralized management of network connections. In addition to BOOTP functionality, DHCP provides configuration services including the assignment of temporary or permanent IP addresses, subnet masks, and default gateways for both BOOTP and DHCP clients.
The TCP/IP Services implementation of DHCP allows system managers to configure a host as a DHCP server and specify server characteristics (parameters) and client information through DHCP's graphical user interface (GUI).
System managers who currently use BOOTP to manage their IP address space can easily migrate to a DHCP environment. In addition, system managers can configure a cluster failover environment to ensure that a backup system takes over as the DHCP server if the active DHCP server process should stop for any reason.
For information about configuring your DHCP environment, see
Chapter 5.
1.7 Management Tools and Utilities
The Management Control Program is a comprehensive, easy-to-use network management tool that includes over 100 OpenVMS DCL-style commands. These commands allow you to locally configure, monitor, and tune DIGITAL TCP/IP Services for OpenVMS components and to write customized applications by issuing management commands at the TCPIP> prompt.
To invoke the program, enter:
$ TCPIP |
You can also use UNIX management commands to manage some components of the TCP/IP Services product. Table 1-5 lists the supported UNIX commands.
| Command | Description |
|---|---|
| ifconfig | Configures or displays network interface parameters, redefines an address for a particular interface, or sets options such as an alias list, broadcast address, or access filter. |
| netstat | Displays network statistics of sockets, data link counters, specified protocols or aliases, network interfaces, and a host's routing table. |
| sysconfig | Displays and maintains the network subsystem attributes. |
| route | Manually manipulates the routing table. Normally a system routing table management daemon, such as GATED or ROUTED, tends to this task. |
| arp | Controls and displays ARP tables for the specified host. |
| ping | Sends ICMP ECHO_REQUEST packets to network host. |
| traceroute | Displays the route that packets take to the network host. |
The DIGITAL TCP/IP Services for OpenVMS product supports the following application programming interfaces (APIs) for developing customized network applications:
The Berkeley socket interface is a programming interface that provides applications with access to network communication protocols. A socket is a generalized, UNIX communication endpoint upon which the TCP/IP protocols have been implemented. Using the socket programming interface, makes it easy to implement network applications. Sockets have become a popular programming interface.
OpenVMS provides support for the socket interface through the C programming language and the DEC C Run-time Library. Benefits of using the socket interface on the OpenVMS platform include:
Refer to the DIGITAL TCP/IP Services for OpenVMS System Services and C Socket Programming manual for more details.
1.8.2 OpenVMS QIO System Service Interface
The standard I/O programming interface on OpenVMS is through the QIO (Queue Input/Output) system services. QIO provides a rich set of functions for controlling devices, and connections, and for performing input (read) and output (write) operations.
The benefits of using the OpenVMS QIO interface include:
Refer to the DIGITAL TCP/IP Services for OpenVMS System Services and C Socket Programming manual for more details.
1.8.3 Sun RPC Programming Interface
The RPC programming interface is an industry-standard, portable API that is an efficient alternative to application development with sockets. Programmers using RPC do not need an in-depth knowledge of networking protocols.
One strong point of the RPC interface is its ability to distribute functions across the network. This is done in an architecture-independent manner where floating point formats and byte address ordering would normally lead to problems when interacting between architectures.
This API includes:
Refer to the DIGITAL TCP/IP Services for OpenVMS ONC RPC Programming manual for more details.
1.8.4 eSNMP Programming Interface
The Extensible Simple Network Management Protocol (eSNMP) API provides routines for developing applications that remotely manage and collect data from network devices such as routers, bridges, and hosts.
The network devices run software that carry out management commands that either get information from or set operating parameters for the device.
Other network applications send commands to network devices to perform configuration management, monitor network traffic, or troubleshoot network problems.
The API provides routines for the following functions:
The eSNMP API routines are almost identical in function and interface with the routines in the Tru64 UNIX API.
Refer to the DIGITAL TCP/IP Services for OpenVMS eSNMP Programming and Reference manual for more details.
1.9 Application Support
TCP/IP Services provides support for the following:
The DIGITAL TCP/IP Services for OpenVMS software includes the PWIP
driver and the PWIPACP network ancillary control process (ACP). The
PWIP driver makes possible communication between OpenVMS systems
running both PATHWORKS server and TCP/IP Services software, and
personal computers running PATHWORKS client software. It also enables
the DECnet-over-TCP/IP feature, which is included with the DECnet-Plus
for OpenVMS Version 6.0 and later software. For more information, see
the DECnet-Plus for OpenVMS documentation.
1.9.2 SRI QIO Compatibility
TCP/IP Services provides support for applications using the INETDRIVER QIO interface developed at Stanford Research Institute (SRI) in 1980-81. An SRI QIO emulator that translates non-TCP/IP Services QIO interfaces into TCP/IP Services QIO programming interfaces can be configured by using the TCPIP$CONFIG procedure.
An internet is a set of connected networks that act as a coordinated whole, providing interconnections while allowing individual groups to select the network hardware best suited to their needs. This chapter discusses the following networking and TCP/IP concepts:
It is important to remember that the internet is not a new kind of physical network. It is a method of interconnecting physical networks and includes a set of conventions for using these networks that allow the computers they reach to interact. While network hardware plays only a minor role in the overall design, understanding the internet technology requires you to distinguish between the low-level mechanisms provided by the hardware and the higher-level facilities provided by the DIGITAL TCP/IP Services for OpenVMS software.
A network consists of two or more computer systems linked by communications hardware and software. An open network is a network of open systems. An open system is a computer system with communications software that implements formal, international networking standards (for example, the TCP/IP suite of protocols).
A TCP/IP network supports remote system communication, resource
sharing, and distributed processing. Network users can access resources
on any system in the network and the resources of other vendors'
systems.
2.1.1 Local Area Networks
A local area network (LAN) consists of two or more hosts, all connected
to one broadcast medium by a high-speed communication medium over short
distances. Host computers connect to the communication medium by a
hardware interface that often connects to one of the following LANs:
Ethernet, FDDI, or Token Ring.
2.1.2 Wide Area Networks
A wide area network (WAN) consists of two or more hosts residing in different locations. Communication transmissions are primarily carried for long distances over telephone lines or a similar medium. Each host connects to the communication medium by a hardware interface connected to the WAN. DIGITAL TCP/IP Services for OpenVMS supports the Serial Line Internet Protocol (SLIP) and the Point-to-Point Protocol (PPP) standards.
SLIP is a framing protocol that sends IP packets over dialup phone lines. SLIP treats each serial link as a separate connection.
PPP is also a framing protocol that sends IP packets over dialup phone
lines. Like SLIP, PPP also treats each serial link as a separate
network. However, PPP's advantage over SLIP is that it can assign a
temporary network number that applies during the time the connection is
established. This approach allows internet service providers to make
access available to more users because these users only occupy the
line, and therefore the network number, during the connection.
2.1.3 Subnets
You can divide a network into subnetworks. A subnet is a single network within a group of interconnected networks. Subnets are useful for organizing hosts within a network into logical groups. When you use subnet routing, multiple physical networks can share a single network address. You can use local routers and subnet addresses for each local physical network and cause the network to appear as one single network to other systems. The data from a host on another network routes through a router on to the appropriate subnet, where the destination host receives the data.
For example, your company may have only one assigned network number,
even though several physical networks exist. In this scenario, you can
use local routers and assign a subnet address to each physical network
to make it appear to outside systems that your company has only one
network.
2.2 Internets
An internet is a unified, cooperative collection of two or more networks that support a single, universal communication service. The networks are connected by a host that acts as a router. A router forwards data from one host to another host on a different network. Underlying communication mechanisms reside on each network. Between these mechanisms and application programs, low-level protocols are hidden to make the collection of networks appear to be a single large network. These interconnected systems agree to conventions, such as procedures for moving data, that enable each computer to communicate with every other computer on the Internet, whether it is locally or remotely connected.
The Internet is a global internet that uses TCP/IP protocols. This entity is accessible to many universities, military installations, government research labs, private companies, and individuals.
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