DESCRIPTION: DECnet/OSI Phase V ------------------------------ Making the Transition from Phase IV This document introduces DECnet/OSI Phase V -- its design, new features, and enhancements from DECnet Phase IV. It also highlights the benefits of making the transition from Phase IV to Phase V. After outlining Phase V concepts and terminology, this document presents preliminary guidelines for making the transition from a DECnet Phase IV network to DECnet/OSI Phase V. These guidelines introduce appropriate transition methods and sample procedures for various kinds of networks. The intended audience comprises network managers and network planners who are familiar with the DECnet DIGITAL Network Architecture (Phase V) General Description. Contents Phase V: Digital's Commitment to OSI 1 Open Systems Integration 1 DECnet/OSI Phase V Features 2 Phase V Product Support 4 Phase V: Elements of Change 7 Distributed Name Service 7 Network Management 9 Applications 10 Addressing 12 End Nodes 13 Routers 14 VAXcluster Systems 16 Node Configuration 16 Phase V: Making the Transition 18 Preparing for the Transition 18 Planning and Creating the Namespace 22 Transition of LANs Without Routers 26 Transition of Single-Area Networks 26 Transition of Multiarea Networks 29 Key Terms 30 i Phase V: Digital's Commitment to OSI Digital Equipment Corporation continues as the industry leader in networks and communications with its fifth generation of the Digital Network Architecture (DNA) -- DECnet/OSI Phase V. By providing an OSI-based multivendor, multiprotocol network, Digital is in the forefront of open systems integration. Open Systems Integration The greatest advance of Phase V is that it offers full OSI support within theThe greatest advance of Phase V is that it offers full OSI support within the DECnet environment. Open System Interconnection (OSI) refers to the implementation of a set of international standards developed by the International Organization for Standardization (ISO) and the International Telegraph and Telephone Consultative Committee (CCITT) for networks and networking products. DECnet/OSI Phase V fully supports the efforts within ISO for successful interoperation of systems in global multivendor networks. DECnet/OSI Phase V uses the OSI addressing scheme. ISO protocols and the OSI addressing scheme enable OSI-based products from all vendors, including Digital, to interoperate. DECnet/OSI Phase V supports OSI in the following ways: o Automatically delivers OSI to DECnet nodes with an operating system upgrade or new network software. o Enhances DECnet products with the ISO standards, enabling DECnet/OSI Phase V routers to send and receive both Digital and non-Digital OSI packets. o Provides complete OSI implementations. DECnet/OSI systems can participate in other vendors' OSI networks. 1 DECnet/OSI Phase V Features DECnet/OSI Phase V provides many new features, including the following: o Backward compatibility -- DECnet/OSI Phase V is compatible with DECnet Phase IV. Phase V allows supported Digital products to continue successful communications. o OSI applications support -- With DECnet/OSI Phase V, Digital continues to support existing OSI applications such as FTAM and X.400. DECnet/OSI Phase V also enables support for new OSI applications as new standards emerge. o End node support -- Phase V supports multivendor OSI end nodes connected to either LANs or WANs. DECnet/OSI Phase V end nodes can have multiple links. Phase V end nodes cache information to select the appropriate circuit for sending data to a particular destination. In addition, after completing the transition to Phase V, end nodes automatically generate their network addresses. o Distributed Name Service (DNS) -- Phase V uses DNS to store node names and obtain protocol selection information. The DNS namespace replaces the DECnet Phase IV node database. o Network management -- Phase V network management includes a new command interface, the Network Control Language (NCL), and is based on the ISO draft international standard Common Management Information Protocol (CMIP). Modular and consistent for all Phase V products, Phase V network management offers continued support for management of Phase IV nodes. o Data Link layer support -- Phase V supports High-level Data Link Control (HDLC). HDLC support includes the LAPB protocol, which is used for X.25 communications. Phase V also continues to support the Digital Data Communications Message Protocol (DDCMP). Phase V supports both the ISO 8802-3 (IEEE 802.3) and the Ethernet standards for the Carrier Sense Multiple Access with Collision Detect (CSMA/CD) class of LANs. In addition, for DECservers and DECrouters, Phase V provides continued down-line loading support. 2 o Routing layer support -- ISO refers to the Routing layer as the Networking layer. This layer supports the ISO addressing standard. Phase V enables communications among multivendor systems and supports a range of networks from small to extremely large. Using the ISO Internetwork Protocol, the Phase V Routing layer supports the ISO Connectionless-mode Network Service (CLNS). Phase V also supports the ISO Connection-mode Network Service (CONS), used by systems attached to or accessing X.25 WANs. The Phase V Routing layer allows Digital and non-Digital systems to occupy the same routing domain. This layer also enables connection to other routing domains that are not using Phase V routing. Two DECnet/OSI networks can connect and still maintain their autonomy. o Transport layer support -- Phase V supports the OSI Transport Protocols as well as Digital's Network Services Protocol (NSP). The OSI Transport Protocol is used primarily for communications with OSI systems, including DECnet/OSI systems. 3 Phase V Product Support DECnet/OSI Phase V supports a variety of current software and hardware products. Networking Software Current software products that can make the transition to DECnet/OSI Phase V include the following: DECnet-VAX DECnet-ULTRIX DECrouter family of products DECnet for personal computers VAX P.S.I. (Packetnet System Interface) VAX P.S.I. Access VAX FTAM (File Transfer, Access, and Management) VAX OSAK (OSI Applications Kernel) VAX MRX (Message Router X.400 Gateway) DECnet/OSI Phase V continues to support connections to Systems Network Architecture (SNA) environments. 4 Communications Controllers Digital recommends the following communications controllers for DECnet/OSI Phase V: Synchronous Controllers DMF32 (UNIBUS) DMR11 (UNIBUS for DECnet-ULTRIX systems) DMV11 (Q-bus for DECnet-ULTRIX systems) DSV11 (Q-bus) DMB32 (VAXBI) DST32 (for MicroVAX 2000) DEC Multicontroller 581 (DSH32 for MicroVAX 2000) DEC WANcontroller 220 (DSB32 for VAXBI systems) Asynchronous Controllers DMF32 (UNIBUS) CXY08 (Q-bus) DHQ11 (Q-bus) DHV11 (Q-bus) DHB32 (VAXBI) DMB32 (VAXBI) DHT32 (for MicroVAX 2000) DEC Multicontroller 581 (DSH32 for MicroVAX 2000) 5 802.3/Ethernet Controllers DELUA (UNIBUS) DEUNA (UNIBUS) DELQA (Q-bus) DESQA (Q-bus) DEBNA (VAXBI) DESVA (for MicroVAX 2000, VAXstation 2000, and DECstation 3100) Phase IV Products The following products will not migrate to Phase V. However, as Phase IV systems, they continue full communications with all Phase V nodes that have Phase IV-compatible addresses. PDP-11 systems DECsystem-10 and DECSYSTEM-20 systems DMR11 and DMV11 hardware for DECnet-VAX systems DECSA-based dedicated routers DEQNA hardware for DECnet-VAX systems 6 Phase V: Elements of Change DECnet/OSI Phase V introduces many new and powerful features, the most significant of which is the integration of OSI into the DECnet software. The transition of networks from DECnet Phase IV to DECnet/OSI Phase V can occur as gradually or as rapidly as is necessary for each network. From the start, two tools are essential to the Phase V network: the Distributed Name Service (DNS) and the new Phase V network management. Other features, such as new application programming interfaces and the Phase V routing protocols, need not be adopted until their Phase V benefits are desired. Regardless of when these new features are utilized, full support exists for the Phase IV programming interfaces and the Phase IV routing protocols. For network management personnel, the effort required to make the transition depends upon the size and complexity of the network. However, all Phase V network managers need to learn and use two new tools -- DNS and Phase V network management. Note that in this document, the sections on using DNS and Phase V network management apply to all Phase V networks. Discussions about routing protocols apply only to networks with routers. Distributed Name Service The Distributed Name Service (DNS) offers consistent, networkwide naming of network resources or objects, such as nodes, disks, queues, and mailboxes. DNS stores object names and attributes, for example, address and protocol information. DNS also provides networkwide mapping of names to attributes and automatically distributes updates. DNS names are stored in DNS directories. These directories are organized into a networkwide hierarchy called a namespace. DNS provides these features and benefits: o Location-independent names -- The DNS name of a network resource is independent of the resource's physical location. Location-independent naming makes it possible to relocate the resource in a manner that is transparent to end users and application programmers. 7 o Caching of frequently used information -- DNS software maintains a cache of information obtained during previous requests to DNS servers. Caching maximizes overall performance and reduces the number of requests to DNS servers. o Namespace scaling -- Very large namespaces can be partitioned so that no one DNS server must contain the entire directory structure. The namespace can also be replicated; that is, each directory can be stored on more than one server to ensure high availability. Changes to names and attributes are automatically made available to the whole network. o Unique networkwide names -- All DNS users and applications in the network use a unique name to access a resource. o Simplified management of names -- The consistent, networkwide naming scheme simplifies management of resource names. o Security -- Access to DNS names can be assigned to individuals or to groups. o Future growth -- DNS can support large or small DECnet/OSI Phase V LANs or WANs. o Choice of management style -- DNS allows for either centralized or distributed management of the namespace and the DNS servers. For example, many networks may have one administrator to coordinate the namespace, while other networks may distribute the coordination among several individuals or groups. DNS is based on a client-server model. In this model, both client and server work together to perform the naming function. The client is any application that makes requests of a DNS server. One or more servers store the namespace data and perform the name-to-attribute translation. A clerk, running on each DECnet/OSI Phase V node, is the interface between the client and the server. 8 8 How DECnet/OSI Phase V Uses DNS DECnet/OSI Phase V uses DNS for mapping DNS node names to attributes. Two universal examples of attributes are node address and protocol information. DNS servers store node names and their attributes in a networkwide database. Nodes use DNS to look up the attributes associated with node names and network applications. For example, when making a connect request, a Phase V node passes the remote node's name to DNS. DNS returns the remote node's address and other attributes, such as available protocols to use when making the connection. The requesting node uses this information to connect to the remote node, and then stores the information for future use. In addition, Phase V nodes automatically register with DNS. DNS then stores their name and attributes. Network Management Phase V network management offers three new features: o OSI-based protocols o Modular and consistent management model o New, comprehensive command language ISO Standards Phase V network management is based on the ISO Common Management Information Protocol (CMIP) draft standard for network management operations. CMIP is a combination of two protocols: Management Information Control and Exchange (MICE) protocol used for information exchange and Management Event Notification (MEN) protocol used for event logging. These protocols supersede the Phase IV Network Information and Control Exchange (NICE) protocol. 9 Management Model The design of Phase V network management uses a management model that is modular and consistent. This model has two major components: o Directors -- management software used by the network manager o Entities -- manageable components of the network, such as CSMA/CD circuits, Session Control, and OSI transports Phase V network management architecture is based on the entity model. New Network Command Language The Network Command Language (NCL) software is a new, comprehensive command interface. NCL uses a syntax that reflects the structure of network management. Network managers use NCL to manage all Phase V nodes. To manage Phase IV nodes from a Phase V node, network managers can invoke the Network Control Program (NCP) from NCL. As a result, Phase IV nodes can be managed from either Phase IV or Phase V nodes. Applications DECnet/OSI Phase V allows continued use of existing Phase IV applications without modifications. DECnet/OSI Phase V also supports: o Use of DNS by applications o Additional methods of connecting to applications o Continued use of Phase IV network management applications 10 Programming Interfaces Phase V provides continued support for Phase IV programming interfaces. Applications modified for Phase V do not have to operate within the constraints of Phase IV. Thus, these applications can take advantage of Phase V features. One impact of Phase V on existing applications is the increased length of node names from a maximum of 6 characters to a maximum of 512 characters. However, Phase V does not require long node names. The length of a Phase V node name depends on the directory structure that is defined in the namespace. This change affects existing applications that assume a full node name is displayed in a 6-character field. To handle this situation, Phase V provides a facility that allows system managers to define 6-character node names that map to their DNS node names, thereby allowing Phase IV applications to continue to work without modification.work without modification. DNS Support for Applications A network application can have its object name and an associated set of attributes defined in the namespace. If the attributes include the location of this application, it becomes location independent. In this way, Phase V nodes can always connect to an application by its DNS object name even if the node on which the application resides changes. If an application is modified to use a Phase V programming interface, that application can specify how Session Control uses DNS and how the application connects to an object over different transport protocols. Phase V Application Connections Phase V allows three methods for applications to make connections. Applications can provide the following: o Node name and either the application or file name, as with Phase IV. o DNS object name. Session Control then uses the DNS server to look up the object's address and attributes. o All connection information to Session Control. In this case, there is no need to look up the node name on the DNS server. 11 Network Management Applications Existing network management applications that use the NICE protocol can continue to manage Phase IV nodes from a Phase V node. However, these applications must be modified to use CMIP before they can be used to manage a Phase V node. Addressing DECnet/OSI Phase V provides an advanced addressing scheme that offers the following benefits: o Increased addressing capabilities for larger networks o Backward compatibility with Phase IV addressing o Conformance to the ISO standard for network addressing Increased Addressing Capabilities Phase V's new addressing scheme eliminates the previous Phase IV limits of 1023 nodes per area and 63 areas per network. After the transition is complete, the size of a Phase V network is limited only by the memory capacity and processor capabilities of its routers. Compatibility with Phase IV Addresses Phase V routers can translate Phase IV and Phase V addresses in both directions. To be Phase IV compatible, a Phase V address must have node and area numbers that fall within the Phase IV limits (1023 nodes per area and 63 areas per network). Phase V routers can translate a Phase IV address into a Phase V address and a compatible Phase V address into a Phase IV address. Address Assignment During Transition A Phase V node must have a Phase IV-compatible address in order to communicate with Phase IV nodes. For this reason, it is best to use the existing Phase IV node address during the transition of a node from Phase IV to Phase V software. 12 If new Phase V nodes are added to the network during transition, assigning Phase IV-compatible node addresses helps to ensure communication between the new nodes and the existing Phase IV nodes. After the transition is complete, supplying an address is no longer required for end nodes. Address assignment for end nodes becomes automated because they can generate their own addresses. Conformance to OSI Addressing Phase V complies with the ISO 8348/AD2 addressing standard and fully supports ISO addressing. To ease the transition, Phase V provides defaults for most Phase V address field parameters. Initial Domain Part The ISO 8348/AD2 addressing standard introduces a new address component called the Initial Domain Part (IDP). Each Phase V address begins with an IDP field. The IDP ensures unique network addresses throughout the world and identifies each DECnet/OSI Phase V or other OSI network. A unique IDP allows the network to connect to any other DECnet/OSI Phase V or OSI network. A small network may not need a unique IDP if that network has no current or planned connections to other OSI networks. Note that Phase IV nodes can communicate only with nodes that have the same IDP as the Phase V routers to which they are connected. There are several ways to obtain an IDP. To accommodate customer needs, Digital will ship products with the same default IDP and will also provide customers with a procedure for obtaining a unique IDP. End Nodes End nodes, also called end systems in OSI terminology, can be upgraded to Phase V software at any time. Because DECnet/OSI Phase V software is backward compatible, Phase IV and Phase V end nodes can coexist within the network. Phase V allows these combinations: o A mix of Phase IV and Phase V end nodes within a DECnet area o Connection of Phase V end nodes to Phase IV routers o Connection of Phase IV end nodes to Phase V routers 13 Phase V end nodes can reside within an area in which all the level 1 routers are running the Phase IV routing protocols (a Phase IV area). Likewise, Phase IV end nodes can reside within an area in which all the level 1 routers are running the Phase V routing protocols (a Phase V area). For a mix of Phase IV and Phase V end nodes to coexist in either area, all node addresses within the area must be Phase IV compatible. Routers A DECnet/OSI Phase V network can have two types of routers: o Level 1 router -- routes data between nodes within its own area, and routes data toward a level 2 router when the destination system is in another area. o Level 2 router -- routes data between nodes within its own area and to other areas in the network. DECnet/OSI Phase V routers, also called intermediate systems in OSI terminology, use new routing protocols that provide flexibility, as follows: o Level 1 routers can run either Phase IV or Phase V routing protocols. o Level 2 routers can run different routing protocols at level 1 and level 2. o Each area in the network can use either Phase IV or Phase V routing protocols, regardless of the routing protocols other areas are running. 14 Phase V software can be installed onto a router at any time. The routing protocols (Phase IV or Phase V) currently in use within the area and the level 2 network are specified during the installation. Routers in the Level 2 Network All level 2 routers that connect areas in the network make up the level 2 network. With Phase V software, level 2 routers can run different protocols at each level. For example, a level 2 router can run Phase V routing protocols at level 1 and Phase IV routing protocols at level 2. Level 2 networks need not make the transition to Phase V at the same time as individual areas. Routers Within an Area All level 1 routers within an area must run the same set of routing protocols. With Phase V software, a router can function as a Phase IV router and can coexist in an area with Phase IV routers during the transition. The ability to run Phase IV routing protocols also permits Phase V routers to coexist in areas that will continue to use Phase IV routing protocols for an extended time. Once all the routers in an area have Phase V software installed, the network manager uses Phase V network management to begin the change from Phase IV to Phase V routing protocols. Phase IV Routers Some Phase IV routers, such as PDP-11 systems and DECSA routers, cannot run Phase V software. DECnet/OSI Phase V allows these routers to continue operating successfully in an area in which all other level 1 routers are running Phase IV routing protocols. If a Phase IV router that is not making the transition is a time-sharing system, then a viable solution may be to reconfigure the system as an end node within a Phase V area. If desirable, selected routers can be maintained at Phase IV. For example, a router may stay at Phase IV because an existing application running on that system depends on the Phase IV version of the operating system. 15 VAXcluster(TM) Systems DECnet-VAX Phase V software will continue to support the cluster alias feature of VAXcluster systems. The nodes in the VAXcluster participating in the alias must be either all Phase IV nodes or all Phase V nodes. Also, unlike Phase IV, Phase V does not require a routing node within the VAXcluster in order to use an alias. Node Configuration The activities associated with node configuration are different for Phase IV, the transition, and Phase V. Node Address During the transition, network managers should use the existing Phase IV method to allocate network addresses. Once the transition is complete, assigning and manually entering network addresses for end nodes becomes unnecessary. Phase V end nodes can automatically generate their addresses during configuration. Network managers must continue to allocate node addresses for routers in a Phase V network.routers in a Phase V network. Node Name As with Phase IV networks, each node in a Phase V network requires a unique name. However, Phase V node names are DNS names. Since DNS names reflect the structure of the directory hierarchy of the namespace, the coordinator of the namespace and the system manager determine the node name. DNS Server Address Phase V requires that each node know the DNS server address. During the transition, this address is automatically determined if the DNS server is located on the same LAN as the node being configured. If not, the system manager must manually enter the address. 16 Adding Nodes to the Network The following two tables summarize the differences in information and tasks for system and network managers when adding nodes to the network. The first table lists the information that the system manager supplies in configuring a node in the network. System Manager Input Phase IV During Transition Phase V Node name Node name Node name Node address Node address n/a n/a DNS server address* DNS server address* * Only if the node and a DNS server are not located on the same LAN The following table summarizes the network configuration tasks that the network manager must perform before, during, and after the transition. Network Manager Tasks Phase IV During Transition Phase V Allocate end node Allocate end node n/a addresses addresses Allocate router Allocate router Allocate router addresses addresses addresses Define names/addresses Define names/addresses n/a in node database in node database Distribute name/ Distribute names n/a address translations addresses to Phase IV nodes n/a Enter Phase IV names/ n/a addresses into namespace n/a Manage namespace Manage namespace n/a Determine node names Determine node names When the transition is complete, the configuration requirements for both the system manager and the network manager lessen, and node configuration becomes significantly easier than in the Phase IV environment. 17 Phase V: Making the Transition Making the transition to Phase V requires planning. Consider these factors: the size of the network, the requirements of the network, preparing for the transition, and planning the Phase V namespace. Preparing for the Transition The amount of planning and preparation depends on the size and complexity of network. For many networks, the transition will be similar in scope to an operating system upgrade and can be planned and executed easily by a single person. Much of the information in the rest of this document does not pertain to such networks. However, the sections that follow contain guidelines that generally are useful in preparing networks for the transition. Digital plans to provide training and support services to assist customers in the transition of large, complex networks. For networks of any size, use the following list as a starting point to prepare for the transition to Phase V: o Identify personnel to coordinate the transition. o Consider the applicable transition guidelines. o Gather information about end nodes, routers, and circuits. o If the network has dedicated routers, select a node to start the transition of these routers. 18 Identifying Personnel to Coordinate the Transition Each network needs a focal point for gathering and disseminating Phase V transition information. This focal point can be either one person or a team. The current network manager may provide this coordination. A transition coordinator is the first individual to become familiar with and use Phase V features and Phase V network management. Transition coordinators have the following responsibilities: o Gather and maintain information about the network. o Ensure that DNS is available. o Help to design the namespace and the naming conventions. o Allocate node names and addresses that ensure Phase IV compatibility. o Become knowledgeable about DNS and Phase V network management. o Identify Phase IV network management applications that use the Network Information and Control Exchange (NICE) protocol; ensure that these applications are upgraded to CMIP. o Determine whether to use the IDP that comes with the Phase V software or whether a different IDP is needed. Digital plans to provide a procedure for obtaining IDPs. o Plan the introduction of Phase V into the network, including down-time schedules. o Implement the transition to Phase V. 19 Considering Applicable Transition Guidelines Consider the following simple guidelines when planning the transition process. Note that many of the guidelines apply only to large networks with multiple areas and routers. The guidelines apply to these aspects of the network: o DNS servers -- During the transition, ensure that the addresses of Phase V DNS servers follow Phase IV addressing conventions. This addressing allows interoperability in a network that has both Phase IV and Phase V nodes. o Addressing scheme -- Until all nodes can run the Phase V routing protocols, continue to use node addresses that adhere to the DECnet Phase IV addressing scheme. Assign a valid Phase IV address to any new nodes that are added to the network during the transition. This ensures continued interoperability among all nodes. o End nodes -- DECnet/OSI networks can contain a mix of Phase IV and Phase V end nodes in the same area. Install the Phase V software on end nodes, regardless of whether the routers in that area are running the Phase IV or the Phase V routing protocols. o Routing protocol -- Install the Phase V software on routers at any time. The software can be set to run either Phase IV or Phase V routing protocols. After the Phase V software has been installed, a network can continue to use the Phase IV routing protocols indefinitely. The requirements of the network, such as the need to support multivendor OSI nodes, determine when to begin using the Phase V routing protocols. o Areas and level 1 routers -- Before starting the transition of an area, ensure that all routers in that area can run Phase V routing software. Change routers that cannot run Phase V routing software to end nodes, or move them to an area that will remain at Phase IV. Level 1 routers can be changed to run the Phase V routing protocols regardless of whether the end nodes are at Phase IV or Phase V. o Level 2 routers -- Before starting the transition of a level 2 network, ensure that all level 2 routers can run Phase V routing software. Change the ones that cannot to end nodes, or change them to level 1 routers in an area that will remain at Phase IV. 20 Gathering Information About End Nodes, Routers, and Circuits Compile information about the nodes in the network to help locate systems that need particular attention. Regardless of the network's size, compile a list of node names and addresses. This information may be derived from the node name database. DNS uses this data to populate the namespace during the transition. For networks with routers, gather the following information about these routers and the circuit connections between them. This information helps to identify routers that will remain at Phase IV. o DECnet node address (area and number) o Operating system and version o DECnet software name and version o Router type (level 1 router, level 2 router) o VAXcluster information o Circuit configuration Selecting a Node to Start Dedicated Router Transition Ensure that DNS exists in the network. To start the transition of dedicated routers, select a Phase V node. The Phase V software on this node provides the required new network management. 21 Planning and Creating the Namespace Three activities are required for creating the namespace: planning the namespace, selecting DNS servers, and populating the namespace. Planning the Namespace To help achieve a smooth, successful transition from Phase IV to Phase V, plan a design for the namespace. Consider the future growth of the network. A well-designed namespace efficiently accommodates changes in an organization's structure and network configuration. Use the following guidelines to help meet specific network requirements: o Define administrative tasks and responsibilities. Specify the tasks needed for administering the namespace. Tasks include creating and replicating DNS directories, assigning access rights, and monitoring the naming policy. Also, the duties of a Phase IV node registrar are required as long as the network has Phase IV nodes. o Develop naming conventions for network resources. Choose short, meaningful names, such as names of departments, and use consistent names for network resources. For directories immediately under the root directory, choose names that are not likely to change. o Design the node name hierarchy. One approach is to start with an organizational structure and to update the design when the organization and the network change. Designing the namespace is an ongoing process. o Plan the layout of the namespace. Determine how the DNS directories will be arranged within the namespace. Then decide how the namespace will be partitioned. 22 The following examples illustrate two ways of placing node names in the namespace. Nonhierarchical Node Names In a nonhierarchical namespace, all DNS names may be located in the root directory. This type of namespace is similar to the Phase IV node database. Nonhierarchical namespaces are appropriate for networks of approximately 100 nodes or fewer that have minimal projected growth. Simplicity is the major benefit of a nonhierarchical namespace. Hierarchical Node Names A hierarchical namespace consists of several DNS directories organized into a hierarchical tree under the root directory. Creating a DNS directory under the root directory sets up this type of namespace. A hierarchical namespace offers the following benefits:A hierarchical namespace offers the following benefits: o Allows replication based on frequent access and availability -- The hierarchical namespace allows replication of directories with frequently used information on several DNS servers. This ensures maximum availability of information. o Allows flexibility in placement of directories -- A directory can be located near clerks that use the directory's information most frequently. For example, a directory with scientific research information is located near the systems running scientific applications. o Allows future growth -- The hierarchical namespace can store a large number of DNS names. 23 Selecting DNS Servers After planning the namespace, choose the nodes that will be DNS servers. The location of DNS servers depends on several factors, including the size and topology of the network. DNS is currently implemented on the VMS operating system and will be offered on additional operating systems. Considerations for selecting a node that makes a good DNS server include the node's availability, reliability, and system performance. Designating two servers with identical contents ensures continuous DNS availability and provides a backup of the contents. DNS performance can be improved by increasing the capacity of the servers as well as by increasing the number of servers in the network. Creating and Populating the Namespace With the namespace design complete and servers selected, begin creating the namespace on the first server. With Phase IV, installation of the first DNS server created the namespace and the root directory. With Phase V, first use NCL to start the DNS software on servers and then to create the namespace. Once the namespace exists, begin populating it. First, set up a shell, or skeleton, namespace. This shell is based on the namespace design and consists of the root directory and directories that branch from it. Later these directories can be populated with entries, such as Phase V node names. Add new directories at any time to any level of the namespace hierarchy. Phase IV Node Name Database During Transition Create a Phase V DNS name for each Phase IV node to allow interoperation between Phase IV and Phase V nodes. During transition each Phase IV node has two names: a Phase IV name and a Phase V name. Other Phase IV nodes continue to access a node by its Phase IV name, for example, NODE3. At the same time, Phase V nodes access this node by its Phase V name, for example, .ENG.DEV.NODE3. 24 Phase V nodes can also use the Phase IV name through the node alias database. However, the node alias database is primarily a transition tool to aid applications that assume 6-character node names. It is not a substitute for aapplications that assume 6-character node names. It is not a substitute for a hierarchical namespace. Use one of these procedures: o Place the entire Phase IV node database in the root directory of the Phase V namespace. With this method, a node's Phase IV name, for example, NODE3, and its Phase V name, for example, .NODE3, are similar. This kind of transfer is appropriate for networks of approximately 100 nodes or fewer that are not planning to grow. o Create the hierarchy of directories. Then create Phase V node names for Phase IV nodes and place these names in their appropriate directory. With this method, a node's Phase IV name, for example, NODE3, and Phase V name, for example, .ENG.DEV.NODE3, are different. Although this method may initially seem time consuming, Digital recommends it because it is ultimately the most efficient for networks with approximately 100 nodes or more. 25 Transition of LANs Without Routers Local area networks and extended LANs without routers are the simplest networks to make the transition to Phase V. Since Phase IV and Phase V end nodes can coexist in a LAN without the need for a router, the transition of an end node can occur any time the software is available for that node. Follow these steps: o Create and populate the namespace. o Continue to use Phase IV-compatible addresses to ensure interoperability while there are still Phase IV nodes in the LAN. o Install the Phase V software onto end nodes at any time. This process does not disrupt communication among other nodes on the LAN during the transition to Phase V. Transition of Single-Area Networks Many small and medium-sized networks have a single area, such as an area that exists entirely within a LAN. These networks can be converted to Phase V with a method that requires changing the network routing nodes to run the Phase V routing protocols. For DECnet-VAX routers, change the routing protocols by shutting down the network software that is set to the Phase IV protocols and bring up the network software set to the Phase V protocols. To change the routing protocols for dedicated routers, use the node that was selected to start the transition. Use this node to reboot the router with the network software set to the Phase V protocols. 26 During the transition of routing protocols from Phase IV to Phase V, there will be a time during which both protocols exist in the network. As a result, connectivity through adjacent routers running dissimilar routing protocols cannot be maintained. For this reason, it is important to ensure that once the transition of routing protocols begins, all routers are changed to run the Phase V protocols. When the transition is complete, connectivity throughout the area is automatically restored. The amount of time required for the total transition depends on the number of routers in the area and the method used to convert them to run Phase V protocols. This process takes only minutes if there are few routers in the area. To minimize the impact of the loss of connectivity within an area, consider the following guidelines: o Perform the transition at a time that has the least impact on network users. o Select a method that balances the resources and time available to complete the transition. To help complete the transition, Digital supports two methods of Routing layer transition: o Locally through a coordinated effort with all routers changing at once o Remotely through network management with routers changing one at a time 27 Use either method or a combination of the two to meet specific networking needs. To use these methods, follow these steps: o Create and populate the namespace. o Convert end nodes to Phase V at any time. o Verify that all routing nodes can run Phase V software. Move the routers that cannot run Phase V software into areas that will continue to use Phase IV routing protocols, or convert these routers to end nodes. o Install the Phase V routing software, which continues to use Phase IVo Install the Phase V routing software, which continues to use Phase IV routing protocols, and change the routers to run Phase V routing protocols. Depending on the needs of the network, select either the local or remote method: -- With the local method, install the Phase V software onto all routers. Then set the routers to run the Phase V routing protocols at the same time. -- If the local method is not appropriate, use the following procedure to change routers remotely. Install the Phase V software, which is set to run the Phase IV routing protocols, onto the routers as the software becomes available. (There is no need to install the software onto all routers at once, since this operation does not disrupt communications among other nodes.) After installing the Phase V software onto all routers, use remote network management to change the routers one at a time to run Phase V routing protocols. The network is now running the Phase V routing protocols and supports Phase IV, Phase V, and multivendor OSI end nodes. 28 Transition of Multiarea Networks One possible transition method for networks with multiple areas is similar to a series of small network conversions. Follow this sequence: o Create and populate the namespace. o Convert end nodes to Phase V at any time. o Convert a few areas using the methods described for single-area networks. Convert areas independently of each other. Become familiar with DECnet/OSI, DNS, and the Phase V network management tools in these areas. o Convert the level 2 network. The process for converting the level 2 network is similar to the process for converting an area. Use one of the methods described for single-area networks to convert the level 2 network. During the transition to Phase V, there will be a time during which both protocols exist in the level 2 network. Although connectivity through adjacent level 2 routers running dissimilar routing protocols cannot be maintained, routing within areas (level 1 routing) continues unaffected. o Convert the other areas that are moving to Phase V. Areas can continue to use the Phase IV routing protocols, as required by some applications and products. Digital plans to provide facilities to assist customers in converting large networks to Phase V. 29 Key Terms Common Management Network management protocol based on ISO standards. Encompasses the Information Protocol (CMIP) Phase V MICE and MEN protocols. DECnet/OSI Phase VDECnet/OSI Phase V Fifth version of Digital Network Architecture (DNA). Conforms to standards set by the International Standards Organization (ISO). Distributed Name Service (DNS) Networkwide, distributed system software used for storing object names (such as nodes, applications, files, disks, queues, and mailboxes) and attributes (such as address and protocol information). Also provides networkwide mapping of names to attributes and automatically distributes updates. DNS server Node with DNS software that maps object names to a set of attributes (including their network address). attributes (including their network address). Initial Domain Part (IDP) The first part of the Phase V address. Uniquely identifies a network among other DECnet/OSI and OSI networks. level 2 network Level 2 routers that connect areas in a network. Management Event Notification (MEN) Protocol Protocol used by DECnet/OSI Phase V that exchanges event information. Management Information Control and Exchange (MICE) Protocol Protocol used by DECnet/OSI Phase V that exchanges management information. namespace Hierarchical tree of DNS directories that store DNS object names. Network Control Language (NCL) Phase V network management language. Provides the command interface for full network and node management. 30 Phase IV area Area that has Phase IV routing protocols running on all its level 1 routers. Phase V area Area that has Phase V routing protocols running on all its level 1 routers. Phase V router Router that has Phase V software installed. A Phase V level 1 router can run either Phase V or Phase IV routing protocols. A Phase V level 2 router can run different routing protocols at each level. Routing domain Collection of routers that use the same routing protocols, plus the end nodes that use their routing services. Session Control Digital Network Architecture (DNA) module that provides the functions for name-to-address mapping, protocol selection, and functions for name-to-address mapping, protocol selection, and system-dependent, process-to-process communication. 31 For additional information on DECnet /OSI Phase V, refer to the DIGITAL Network Architecture (Phase V) General Description (Order No. EK-DNAPV-GD). Digital believes the information in this publication is accurate as of its publication date; such information is subject to change without notice. Digital is not responsible for any inadvertent errors. The following are trademarks of Digital Equipment Corporation: CompacTape, DEC, DECsystem-10, DECSYSTEM-20, DECUS, DECmate, DECnet, DECwriter, DIBOL, the Digital logo, MASSBUS, PDP, P/OS, Professional, Rainbow, RSTS, RSX, UNIBUS, VAX, VAXcluster, VMS, and VT.VAX, VAXcluster, VMS, and VT.