# DIGITAL TCP/IP Services for OpenVMS
Concepts and Planning

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Consider configuring servers even if you are not creating your own zones. If you configure a secondary server for the zones (forward and reverse) where your hosts are members and point your hosts to that secondary server, the BIND service will continue to work for local names even if you lose your link to the outside world.

## 6.4.1 Server Selection Guidelines

Study your network and keep in mind the following guidelines to help you achieve your goals:

- Plan to configure at least three servers for each zone.
  Although each zone requires only one primary server, use at least three servers to increase reliability and performance. Use a primary and secondary server on the same network, and another secondary server outside of the network. Ensure that this other secondary server is on a different LAN or in another building. Also ensure that the secondary server is in an upper-level domain of your zone. This provides an alternate source of information if a server is temporarily unavailable. This scheme also provides a backup of BIND service data if the primary server becomes permanently unavailable.
- Choose stable hosts.
  BIND servers should reside on stable systems that experience minimal downtime and restart quickly. It is important that a BIND server be one of the first systems available in the network, because client applications on the network are limited to the information in caches until a BIND server is available.
- Estimate disk space, CPU, and memory requirements.
  In small zones, the impact of the BIND service on timesharing systems should be minimal. The impact depends partly on the number of entries in the database files, the frequency of use of those names, and the load placed on the system by other applications.

## 6.4.2 Selecting Primary Servers

The primary server is the authority, or best source of information, for one or more zones. You need one primary server for each zone in your domain hierarchy.

Every time a host changes addresses or servers, update the forward and reverse zone files on the primary server. If your zone has many hosts, consider dividing the zone into separate subzones, to balance the administrative work.

A primary server can also be a primary or a secondary server for other zones that exist in a contiguous or non-contiguous part of the name space.

## 6.4.3 Selecting Secondary Servers

Your strategy for configuring secondary servers is especially important in the initial stages of BIND operation. Once a resolver establishes a cache of frequently used names, the server will rarely need to locate a copy of the information it needs. However, well-planned copying of zone files can make the server's process of learning about names in a large network easier and more efficient.

When selecting secondary servers for large networks, consider the following guidelines to enhance BIND service performance:

- Ensure availability.
  Every zone should have at least two secondary servers. Secondary servers ensure an alternate source of information if a primary server becomes temporarily unavailable. Very small zones with one BIND server can use traditional operating system backups to preserve BIND service information. However, backups are not a good way to preserve data in zones that have more than one primary server. Multiple database copies are especially important in these zones because you cannot depend on traditional operating-system backup methods to preserve copied data.
- Distribute the lookup load.
  Identify primary and secondary servers that receive the most lookups and updates. Then configure additional servers within and outside of the local domain to act as secondary servers.
- Place a secondary server where users are located.
  If a zone's users are widely dispersed geographically, create subzones and configure secondary servers to avoid long-distance copying of zone files. These subzones populate the new zone file with domain names used mainly by a group of users concentrated in one geographic area.

## 6.4.4 Selecting Caching-Only Servers

There are no special requirements for caching-only servers. Follow the guidelines in Section 6.4.1.

## 6.4.5 Selecting Forwarder and Slave Servers

You can configure any server to act as a forwarder server. A BIND server can use a forwarder server to resolve queries. Because a forwarder server accepts queries from many other servers, it can develop an extensive cache compared to caches on other servers. Having a forwarder server in your zone can reduce the total number of queries from the zone to the rest of the Internet.

Configure slave servers if you do not want specific hosts to have access to the Internet or you want to restrict the server to using only specified forwarder servers. If you have a slave server in your zone, you must have a forwarder server as well.

## 6.4.6 Determining Server Placement for LANs and Extended LANs

You might be able to use just one server on a LAN. Factors influencing your decision can include the expected lookup load and how you want to distribute it, and the capacity of the systems that you plan to use as BIND servers.

On extended LANs, consider the reliability of the bridge connecting the LANs. If the bridge is frequently unavailable, you might want one server on each side of the bridge. However, if the bridge is reliable, one server on the LAN may be adequate.

## 6.4.7 Determining Server Placement for Sites Connected by a WAN

When planning the placement of BIND servers in a wide area network (WAN) environment, avoid connections through WAN links. WAN links are not usually stable. Place BIND servers so that most systems can access at least one server even if a WAN connection is unavailable.

At small sites connected to the rest of the network through a WAN, a BIND server is not necessary if the small site only occasionally uses resources on the other side of the WAN link. For example, if users at a small site sometimes contact nodes at the company's headquarters, it is probably sufficient to store the node names at headquarters, and it is not necessary to configure a BIND server at the small site. Remember that once the BIND resolver at the small site caches frequently used names, they will rarely need to cross a WAN link for lookups.

Conversely, if a small site has many domains, configure a server there. Also, if you expect users to make frequent name changes, create a zone and store the information at the site's server. This further reduces WAN traffic and improves performance.

# 6.5 Planning Domain Registration

After you plan your domains and zones, your next steps are to create the necessary server files and to register zone and domain information with the upper-level domain administrator and zone technical contact. See Appendix A for information about domain registration.

# Appendix A
InterNIC Registration Services

The InterNIC---the Internet Network Information Center---is a cooperative activity between the National Science Foundation, Network Solutions, Inc., and AT&T that offers four basic services:

- Registration Services
- Directory and Database Services
- Information and Education Services
- Net Scout Services

The InterNIC Registration Services maintain Requests for Comments (RFCs) and documents related to the Domain Name System (DNS). The InterNIC Registration Services also provide Internet domain registration for a small yearly fee.

The other InterNIC services offer an array of tools, resources, databases, and publications of interest to the Internet community.

You can access the InterNIC's web site at http://rs.internic.net for up-to-date information or to receive RFCs, DNS documentation, and current domain registration prices. If you do not yet have Internet access, you can download copies of RFCs and DNS documents, with either the automated mail service or FTP as described in this appendix.

# A.1 Using the Automated Mail Service to Download Documents

Use this service to retrieve DNS-related documents with electronic mail. Send a mail message to MAILSERV@RS.INTERNIC.NET (the body message is unimportant; it is generally ignored). In the SUBJECT field, type one of the following to specify the service you want:

HELP | Returns the list of services you can request.
INDEX | Returns the master list of available index files.
NETINFO xxx | Returns a specified file --- xxx is a file name or the word INDEX.
RFC nnn | Returns the specified Request for Comments (RFC) --- nnn is the RFC number or the word INDEX.
SEND xxx | Returns the specified file --- xxx is a fully qualified file name.
WHOIS xxx | Returns information about the specified entity (domains, network numbers, etc.) --- use WHOIS HELP to receive information about using the WHOIS program.

For example, you could type NETINFO DOMAIN-TEMPLATE.TXT to receive the domain registration template, or you could type RFC 1033 to receive the RFC 1033 file.

The message body is generally ignored. The automated mail service breaks large files into smaller separate mail messages.

# A.2 Using FTP to Download Documents

Retrieve public files using FTP as follows:

1. Open an FTP connection to the RS.INTERNIC.NET host.
2. Log in as user ANONYMOUS.
3. Enter the password GUEST.
4. Retrieve the document you want:
   - RFCs are in the policy subdirectory (get policy/rfcxxx.txt*).
   - The domain template is in the template subdirectory.
   - Other useful documents are in the /netinfo subdirectory.

   # A.3 Registering Your Network on the Internet

   To register your network, autonomous system and domains, complete the appropriate templates (see Table A-1) and return them to the InterNIC Registration Services; you can use either postal mail or electronic mail (see Section A.3.2 for the postal mailing address). The process for using the automatic registration is as follows:

   1. Complete the appropriate templates and mail them to the InterNIC automatic registration services at autoreg@internic.net.
   2. The Automatic Registration software checks the templates for conflicts or errors and returns either a verification or rejection mail message.
   3. If you receive a verification, check that the information is correct and do one of the following:
      - Return the verify form to verify@internic.net.
      - Correct the information and return the verify form.
   4. If you receive a rejection, make the necessary adjustments and resend the registration request to the automatic registration mailbox.

      ## A.3.1 Registration Templates

      Use the templates listed in Table A-1 to register your domains, networks, and autonomous systems.

      Table A-1 Registration Templates
      If Registering This: | Use This Template:
      --- | ---
      Network | templates/internet-number-template.txt
      Autonomous system | netinfo/asn-template.txt
      Domains | templates/domain-template.txt

      ## A.3.2 Registration Services User Assistance

      You can contact the InterNIC using the Internet, postal mail, or the telephone. If you have questions about the registration services or want to mail your registration templates electronically, follow the procedures on the http://rs.internic.net web site. To use postal mail for questions or mailing of your registration templates, send to:
      - Network Solutions Inc.
      - ATTN: InterNIC Registration Services
      - 505 Huntmar Park Drive
      - Herndon, VA 22072

      #

      This glossary defines terms that explain the features and operation of DIGITAL TCP/IP Services for OpenVMS (UCX).

      # G.1 Definitions

      absolute path name: A path name that starts with a slash (/); specifies a file that can be found by starting at the root of the file system and traversing the file tree.

      absolute time: A point on a time scale.

      abstract syntax: The description of a data structure that is independent of host structures or codes.

      Abstract Syntax Notation One (ASN.1): The language used by ISO protocols for describing abstract syntax. Most notable use in TCP/IP is for Simple Network Management Protocol (SNMP) and the Management Information Base I & II (MIB-I & MIB-II). The rules of ASN.1 are independent of the encoding techniques used to represent them.

      access control information: A character string with login information that validates connect or login at a remote host.

      access control list (ACL): A list that defines the kinds of access to be granted or denied to users.

      access rights: A set of privileges that determines what users can do.

      ACK: See acknowledgment.

      acknowledgment (ACK): A type of message sent to indicate that a block of data arrived at its destination without error. A control bit (acknowledgment flag) in the TCP header indicates that the acknowledgment number field is significant for each segment in a packet.

      ACL: See access control list.

      ACP: See ancillary control process.

      active port: A port that is bound to a process.

      address: A number or group of numbers that uniquely identifies a network node within its own network or internet. (See also IP address and hardware address.)

      address mask: A 32-bit mask used to identify which bits in an IP address correspond to the network and subnet portions of the address.

      address resolution: The process of relating a logical address to a physical address, when both refer to the same device, for example, conversion of an IP address into the corresponding Ethernet, Token Ring, or FDDI hardware address. This may require broadcasting on a local network. See also Address Resolution Protocol.

      Address Resolution Protocol (ARP): The protocol that dynamically binds IP addresses to either Ethernet or FDDI addresses; limited to physical network systems that support broadcast packets that can be heard by all hosts on the network. See also proxy ARP.

      addressing: The function that ensures that network systems are correctly identified at all times.

      addressing authority: The authority, such as the American National Standards Institute (ANSI), responsible for assigning Network Interface layer addresses within an addressing domain.

      addressing domain: A level in a hierarchy of Network Interface layer addresses.

      adjacency: A single connection to an adjacent node; collection of state information representing a node in the local node's routing databases.

      adjacency address: An address that identifies a local subnet access point and a subnet address of an adjacent system.

      adjacent nodes: The nodes with direct lines between them; can communicate without an intermediate system. For example, all nodes on an Ethernet LAN are adjacent to each other.

      administrative domain: A group of hosts, routers, and networks operated and managed by a single organization. Routing within an administrative domain is based on a consistent technical plan. An administrative domain is viewed from the outside, for purposes of routing, as a cohesive entity, of which the internal structure is unimportant. Information passed by other administrative domains is trusted less than information from one's own administrative domain.

      aged packet: A data packet that is discarded because it exceeded the maximum number of visits while being forwarded through the network.

      agent: A system that acts on behalf of another system. (1) Client/server model: Part of the system that initiates, prepares, and exchanges information preparation on behalf of a client or server application. (2) Network management: Portion of an entity that responds to management requests and/or preprogrammed trap.

      agent access module: The portion of an agent responsible for the agent's end of SNMP.

      agent access point: The instance of a connection between a client or director and a server or agent.

      agent address: An address that specifies the information needed by a director to establish communications with the agent's management interface.

      agent attributes: The attributes maintained by the agent; do not cross the internal management interface.

      aggregate throughput: See throughput.

      alias: A name, usually easy to remember, that is translated from a different name, usually difficult to remember. Most often used as an optional alternate name for a host. See also host name.

      alias node identifier: An optional node name used by some or all nodes in an OpenVMS cluster, allows them to be treated as one node.

      alternate address notation: The internet address notation that conveys the same information as the common notation, but consists of two parts: network and host.

      American National Standards Institute (ANSI): The organization that coordinates U.S. standards in many areas, including computers and communications.

      American Standard Code for Information Interchange (ASCII): The standard character set that assigns an octal sequence to each letter, number, and selected control characters.

      ancillary control process (ACP): The process that acts as an interface between user software and an I/O driver; provides functions supplementary to those performed in the driver, such as file and directory management.

      anonymous (FTP): A convention of the File Transfer Protocol that allows individuals who do not have explicit authorization to transfer files to and from a host anonymously. The individual usually logs in with a generic user ID and e-mail address as password.

      ANSI: See American National Standard Institute.

      API: See application programming interface.

      application: A program that provides functionality for end users of systems.

      Application layer: The top-most layer in the Internet architecture model where the user interacts with an application such as Network File Service (NFS), File Transfer Protocol (FTP), and mail.

      application process: A part of a distributed application running on a single host.

      application programming interface (API): A standardized set of routines that makes system functions available to programmers.

      architecture: The structure of a system, a description of which can be used to re-create the system.

      ARP: See Address Resolution Protocol.

      ASCII: See American Standard Code for Information Interchange.

      assigned numbers: The numbers officially assigned as part of the Internet standards.

      asynchronous transfer mode (ATM): The method for dynamic allocation of bandwidth using a fixed-size packet (called a cell). Also known as fast packet.

      asynchronous transmission: The mode of transmission in which the time intervals between character transmissions differ. Each character is surrounded by start and stop bits to allow the receiving device to recognize the beginning and end of each character (also called start-stop transmission).

      ATM: See asynchronous transfer mode.

      attribute: The controllable or observable part of an entity; a variable that network managers and applications programmers can manipulate for optimal performance.

      attribute group: A named collection of attributes grouped together, such as all information relating to errors.

      authentication: Verification of the identity of a person or process attempting to access a system.

      authentication server: The software that searches the proxy database for valid user and group identification for remote personal computer users and returns them to PC-NFS.

      autonomous confederation: A group of independent computer systems that trust each other regarding routing and reachability information; members believe information provided by other members in preference to information received from systems that are not part of the confederation.

      autonomous system: A collection of networks controlled by one administrative authority. The gateways within this system are expected to trust one another and to share and update routing information among themselves by any mutually agreeable protocol. A core gateway must also be designated to share routing information with other autonomous systems by means of an External Gateway Protocol. See also External Gateway Protocol.

      auxiliary server: The DIGITAL TCP/IP Services for OpenVMS software that runs as a background process and listens for incoming requests for services. When it receives a request, it runs the appropriate server application; includes inetd, security, and logging options.

      availability: The proportion of time a specific piece of equipment, system, or network is usable, compared to the total time it is expected to be.

      backbone: The primary connectivity mechanism of a hierarchical distributed system. Usually a high-speed high-performance network that links together other networks into an internetwork. All systems with connectivity to an intermediate system on the backbone will connect to each other. This does not prevent systems from setting up private arrangements with each other to bypass the backbone for reasons of cost, performance, or security.

      bandwidth: (1) Technically: The difference, in Hertz (Hz), between the highest and lowest frequencies of a transmission channel. (2) Typically: The amount of data that can be sent through a communications circuit.

      baseband: A characteristic of any network technology that uses a single carrier frequency and requires all stations attached to the network to participate in every transmission; only one communication channel is provided at a time. See also broadband.

      BBS: See Bulletin Board System.

      Berkeley Internet Name Domain (BIND): The implementation of a DNS server developed and distributed by the University of California at Berkeley. Host name and address lookup service for the Internet; implemented in a client/server model. The client software, referred to as the resolver, allows client systems to obtain host names and addresses from servers rather than from locally hosted databases.

      Berkeley Software Distribution (BSD): The derivation of the original UNIX operating system developed by the Computer Systems Research Group of the Department of Electrical Engineering and Computer Science at the University of California at Berkeley. The DIGITAL UNIX operating system is based on the BSD version of UNIX.

      best-effort delivery: A characteristic of network technologies that will attempt to deliver data but will not try to recover if there is an error such as a line failure. Internet protocols IP and UDP provide best-effort delivery service to application programs.

      BG driver: The DIGITAL TCP/IP Services for OpenVMS implementation of a network device driver. See also device driver.

      BGP: See Border Gateway Protocol.

      big endian: The format for storage or transmission of binary data in which the most significant bit (or byte) comes first. The reverse convention is called little endian.

      BIND resolver: The software that asks a name server to look up name and address information.

      BIND server: The software that responds to queries from BIND resolvers for name and address lookups; can be local or distributed. See also cache server, forwarder server, primary server, and secondary server.

      binding: Defining a remote file system to be a part of the local UCX file system.

      Bits per second (bps or b/s): The measure of the rate of data transmission.

      block: A contiguous unit of user information grouped together for transmission, such as the user data within a packet, excluding the protocol overhead.

      boot file: A database file that BIND servers use to determine their type, the zones for which they have authority and the location of other BIND database files.

      BOOTP: The mnemonic for Bootstrap protocol. The protocol used for booting diskless systems remotely to a network. See also remote boot.

      BOOTP database: The DIGITAL TCP/IP Services Software for OpenVMS database with entries for diskless network clients that depend on a boot server to download their system images.

      Border Gateway Protocol (BGP): The interautonomous system routing protocol used to exchange network reachability information between autonomous systems; runs over TCP.

      bottleneck: A point in the network where traffic is delayed or blocked. Bottlenecks are the limiting factors in network performance.

      bound port: An I/O function specifying a port number and IP address for the device socket to bind a port to a process.

      bps: See bits per second.

      bridge: A device that connects two or more physical networks and then stores and forwards complete packets between them; can usually be made to filter packets (that is, to forward only certain traffic).

      broadband: A characteristic of any network that multiplexes multiple, independent network carriers onto a single cable; usually using frequency division multiplexing. Broadband technology allows several networks to coexist on one single cable; traffic from one network does not interfere with traffic from another because the "conversations" happen on different frequencies.

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