An Openview-Based ATM Network Management System Is Born

DEVELOPERS VIEW FEATURE FOR NOVEMBER OPENVIEW ADVISOR

By Nigel Cook, Robert Coote, David Horton, and Geoff Thompson, CiTR Pty. Ltd.; and Dr. Hiroshi Suzuki, NEC Network Research Laboratories and C&C Research Laboratories

ATM (Asynchronous Transfer Mode) networks are emerging as a major broadband networking technology. Because of the complex mixture of different kinds of ATM switch equipment--to say nothing of the need to establish, control, and monitor end-to-end connections (virtual circuits)--managing these networks has created new challenges for private network operators and public telecommunications service providers alike. Considerable effort is being applied to the formulation of standards in this area, especially by the ATM Forum.

CiTR Pty. Ltd. (Queensland, Australia) has been working with NEC (Kawasaki, Japan) to implement a prototype ATM Network Management System (NMS) using Openview and SNMP Version 1 to control and monitor ATM Networks via the IETF (Internet Engineering Task Force) ATM management information base (AToM MIB). This international collaboration has developed successive phased releases of the NMS software. At first, work focused on two areas: connection-oriented Openview map navigation and a graphically driven connection-establishment interface. The latest release includes ATM autodiscovery, automatic optimal route selection when establishing Permanent Virtual Circuits (PVCs), and their subsequent monitoring and unattended restoration.

Perspectives

ATM, of course, is a high-speed networking technology. Its speed, low latency, and ability to handle all kinds of traffic over a single network make it ideal for a range of bandwidth-intensive applications, including multimedia, medical imaging, bank-check imaging, seismology studies, supercomputer applications, and CAD/CAM. One factor influencing the pace at which ATM has been adopted is the development of standards, many of which are being formulated by the ATM Forum. One such standard is the concept of a virtual circuit. Negotiating such a circuit with nominated bandwidth and quality-of-service parameters is one feature of ATM circuit provisioning. Standards defined by the ATM Forum and the IETF allow users to change network design and re-route traffic by manipulating virtual circuits. But in many implementations to date, the process has been a manual one.

The Model

Understanding what this project has achieved requires, first of all, a basic overview of the ATM Forum's network management model (see Figure 1). The model defines five work areas for network management:

ATM end devices (M1)
private ATM networks or switches (M2)
links between public and private networks (M3)
public networks (M4)
links between two public networks (M5)

In this work, the partners have incorporated the ATM Forum architecture, as well as some other emerging standards, including the AToM MIB, an SNMP Version 2 MIB (Management Information Base) developed by the IETF for ATM management. After a year of development--and eight revisions AToMMIB was released in August 1994 as RFC (Request for Comment) 1695. AToMMIB supports semantics for monitoring and setting up virtual circuits. The work undertaken by the project's co-authors at NEC has included ATM Forum submissions to obtain the definitions required for ATM autodiscovery support. Openview was chosen as the development platform; independent published studies of market share and applications available for various network management development platforms confirmed that the marketplace accepts Openview as an "open platform."

The Openview network management system supports M1- and M2-style management interfaces as described by the ATM Forum. The SNMP agent, which was also developed in this project, uses information from the UNI (user-network interface) ILMI (Interim Local Management Interface) for reporting to management functions through the IETF AToM MIB.

Development Program

Early adoption and use of recommendations and drafts from such bodies as the ATM Forum and the IETF is an important aspect of the development project and provides valuable experience for later product implementations. The NEC/CiTR joint development program, which began in mid-1993, concentrates on implementing proof-of-concept network management prototypes based on open standards. The proof-of-concept software CiTR developed has been made available to NEC as an input to commercial product development activities--specifically, the upcoming NEC Atomview product--but that is quite another subject. The development program has been structured in a series of phases, with a number of improvements in functionality during each of them, as outlined below.

Phase 1

At this stage, the project concentrated on building a basic ATM network management system that provided for monitoring and manually initiated control of a set of ATM hosts and switches using SNMPv1. Features included the following:

PVC connection management
multiple views of connections, both logical and physical
drill-down connections and nodes
context-sensitive object detail reports
fault management
SNMPv1 and v2 bilingual agents for both host and switch

At this point, the system, based on AToM MIB and the proprietary end point IP to VCI (Virtual Circuit Identifier) MIB, directly permitted IP address translation. CiTR's in-house tools provided for the automated conversion from SNMP MIB specifications to software agents. This made it easy to track evolving IETF specifications. The system's architecture (see Figure 2) consists of some Openview-based applications and supporting report-generation tools that combine Openview object database (ovwdb) applications and some SNMP applications, as well as atm_lan. The atm_lan application, integrated into OVW (Openview Windows), manipulates the OVW map, symbols, and ovwdb. The next step was to create a sample interface screen, in which the ATM switches and hosts were represented by icons and physical connections between nodes were shown as solid lines with logical connections (virtual paths and circuits).

Phase 2

The next phase of development concentrated on adding automation functions to the basic ATM NMS established during Phase 1. The following functions were added:

fault and topology monitoring
SNMP-based ATM auto-discovery (automatic physical connectivity) using AToM MIB (RFC 1695 Final)
Virtual Circuit Tracing
automatic path selection, using a shortest-path (fewest hops) algorithm as sample heuristic
unattended automatic PVC rerouting

The Phase 2 development also involved a series of enhancements to the Phase 1 software. Another integrated OVW application, known as atm_mon, was added (see Figure 3). This application contains functions that detect nodes and ports making the transition to the "down" state, achieved both by actively polling status and by passively catching and processing "traps" that report the change of state. The division between two applications, atm_lan and atm_mon, exists to ensure maximum responsiveness in atm_lan; atm_mon can suffer from delays because of SNMP timeouts in the processing loop. The atm_lan application was further enhanced during Phase 2. Association between major functional blocks was achieved through a combination of internal APIs (.MDNM/application program interfaces) and the use of OVW callback registration, OVW actions, and Xt Intrinsics timers (see Figure 4).

At this point, the Openview IP submap window was adjusted to show the icons representing the ATM submap. Clicking on the ATM submap icon (nwkatm-cl-nec) explodes it into the top-level ATM submap, which is populated by the ATM autodiscovery process.

ATM Auto-discovery

ATM autodiscovery functionality is a key feature in a network management system for private LAN-centered ATM networking environments. It is important not only for initially determining the physical connectivity of the network but also for ongoing efforts to monitor the topology. Other elements of functionality, such as unattended PVC rerouting, rely on the automatic invocation of autodiscovery to maintain a view of the network topology on detecting a port status change. When it becomes aware of a port operational status change, the Openview object status change callback triggers processing. Subsequent processing by atm_mon, using information obtained from neighboring information fields defined in RFC 1695, determines when a topology change occurs, and an Openview action then triggers the invocation of autodiscovery to resolve the updated network configuration. The autodiscovery algorithm minimizes the host traffic, since it is linear to the number of nodes in the system (see table and Figure 5). Only a small percentage of the time required for autodiscovery is associated with network accesses. Most processing is related to Openview database manipulation.

Openview is an effective development environment. But it suffers in a number of areas that affected the development effort and the clarity of presentation to the end-user.

There is a lack of transaction functionality to group multiple object add and delete operations. In the application developed by the project, there are long sequences of operations involving the Openview databases, MIBs on a number of different nodes, and an external database. During an involved creation process, the Openview model requires developers to keep separate records of components created, so that if a rollback is necessary, the components created before the rollback can be deleted. Rolling back a delete is also a complicated process. These limitations force the application to check before sending requests, so as to ensure that operations are likely to succeed.
The Openview palette of icons and connections allows no program control or hiding. This causes the internal symbols in the system to be inappropriately exposed to the user as a possible choice.
Connections are poorly supported as regards locating connections for an object, and there is a limitation of only one connection palette.
ovwdb is separate from mapdb. The management system includes a status-monitoring daemon that updated the status on objects associated with the MIB only--in other words, that did not relate to symbols on a submap. But as a result of Openview's limitations, a separate Openview session was necessary to provide a submap to set status on objects. Another part of the management system included a background recovery application that rerouted PVCs and detected network topology changes. To make these changes to the map, a read/write connection to a map was required, and it would interact unfavorably with operator usage of the map. Although it may be possible to batch up symbol and submap changes until a writable map becomes available, this would introduce considerably more application complexity.
Program versus user control are poorly distinguished. Openview cannot distinguish programatically between user- and software-initiated actions.
Operations that update the Openview database are very slow. Even with the relatively small test network, the majority of elapsed time for such operations--for example, automatic rerouting--must be spent updating the Openview representations and database rather than manipulating the actual network.

Future Directions

As time goes on, the project aims to improve the host MIB definitions and to create a display based on world geographical coordinates. To sum up, although the Openview platform was an adequate development tool for the Broadband Network Management applications, it has considerable limitations. Nevertheless, our use of automated agent-generation tools provided for easy tracking of standards. The project demonstrates the possibility of an Openview-based Broadband Network Management system, based upon the open standards defined by the IETF and ATM Forum, and capable of controlling networks containing multiple vendor switches.

Biographies

Nigel Cook is an account manager, Robert Coote, David Horton and Geoff Thompson are consultants with CiTR. CiTR is an Australian software engineering company specialising in network and services management. They can be reached on the internet at n.cook@citr.uq.oz.au, r.coote@citr.uq.oz.au, d.horton@citr.uq.oz.au, g.thompson@citr.uq.oz.au .

Dr Hiroshi Suzuki is a senior researcher at the NEC Network Research laboratories developing NEC's range of ATM switches. He can be reached on the internet at hiroshi@nwk.cl.nec.co.jp .

Table: ATM Autodiscovery Timings

This table presents a sample of the timings and performance of the autodiscovery algorithm, based on a Sun Sparc 10.


Number of Nodes            Number of Connections      Time to Auto-discover

4                              3                          27.33s 
4                              6                          29.00s 
8                              7                          55.6s 
8                             28                          75.25s