Configuration management in network management is normally used in the context of discovering network topology, mapping the network, and setting up configuration parameters in management agents and management systems. Network management in the broad sense also includes network provisioning, which includes network planning and design. Network Provisioning is considered to be part of configuration management.
- Network Provisioning :
• Network provisioning, also called circuit provisioning in the telephone industry, is an automated process.
• A trunk (circuit from the originating switching center to the destination switching center) and a special service circuit (customized to meet customer specifications) are designed by application programs written in operation systems.
• Planning and inventory systems are integrated with design systems to build an overall system (often referred to as a system of systems). Thus a circuit designed for the future automatically derives its turn-on date from the planning system and ensures that the components are available in the inventory system.
• Similarly disconnecting a circuit is coordinated with the planning system, and the freed-up components are added to the inventory system, making the design system aware of the availability of components for future designs.
• Given the requirements of a trunk, such as transmission loss and noise, type of circuit, availability date, as input to the system, the system automatically designs trunk components.
• The designed circuit identifies the transmission facilities between switching offices and equipment in intermediate and end offices. Equipment selection is based on the devices available when the circuit is to be installed.
• Network provisioning in a computer communications network has different requirements. Instead of circuit-switched connections, packet-switched paths are used to transmit information from source to destination.
• In a connectionless packet-switched circuit, each packet takes an independent path and the switching of each packet by the routers at various nodes is based on the load in the links.
• Provisioning of the links is based on average and peak demands. In store-and-forward communication, excess packets can be stored in buffers in routers or retransmitted in the event that packets are lost or discarded.
• In connection-oriented circuit communication, permanent and switched-virtual circuit demands need to be accommodated for end-to-end demands on the various links.
• Network provisioning for packet-switched network is based on performance statistics and quality of service requirements.
• Network provisioning in broadband WAN communication using ATM technology is more complex. The virtual-circuit concept is always used and has to be taken into account in the provisioning process.
• The switches are cell-based, in contrast to frame-based packet switching. Each ATM switch has knowledge of the virtual path-virtual circuit (VP-VC) of each session connection only to the neighboring nodes and not end-to-end.
• Each ATM switch vendor has built into the ATM switch their proprietary assignment of VP-VC for end-to-end design.
• The architecture of end-to-end provisioning of ATM circuits could be either centralized or distributed. It is based on whether the circuit is a permanent virtual circuit (PVC) or a switched virtual circuit (SVC). Commercial products, which provision PVCs for multiple vendor products, have recently been introduced.
- Network Topology:
• Network management is based on knowledge of network topology. As a network grows, shrinks, or otherwise changes, network topology needs to be updated automatically.
• Such updating is done by the discovery application in the network management system. However, the scope of the discovery process needs to be constrained.
• For example, the arp command can discover any network component that responds with an IP address, which can then be mapped by the network management system.
• If the response includes workstations that are turned on only when they are in use, the network management system would indicate failure whenever they are off.
• In addition, some hosts should not be discovered for security reasons and should be filtered out during the discovery process. Hence the discovery application should have the capability to set filter parameters to impose constraints.
• Auto discovery can be done by using the broadcast ping on each segment and following up with further SNMP queries to gather more details on the system.
• A more efficient method is to look at the ARP cache in the local router. The ARP cache table is large and contains the addresses of all the hosts and nodes used in recent communications.
• Use of this table also allows subsequent ARP queries to be sent to other routers. This process is continued until the desired information is obtained on all IP addresses defined by the scope of the auto discovery procedure.
• A map showing network topology is presented by the auto discovery procedure after the addresses of the network entities have been discovered.
• The auto discovery procedure becomes more complex in the virtual LAN configuration.
• Figure1 shows the physical configuration of a conventional LAN. The router can be visualized as part of a backbone (not shown).
• Two LAN segments, segment A and segment B are connected to the router. They are physically connected to two physical ports in the router (i.e., one port for each segment is used on the interface card).
• They are identified as port A and port B and correspond to segment A and segment B, respectively. Both LANs are Ethernet LANs and use hub configuration.
• Two hosts, A1 and A2, are connected to hub 1 on LAN segment A and two hosts, B1 and B2, are connected to huh 2 on LAN segment B.
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