| The Management of QoS To manage the Qos effectually is to control the delay, jittery, throughput, drop rate and other capability parameter of the data flows which are transmitted through the network .In the QoS field, the manufacturer of device and technician focus on the development of the several QoS technology, such as: Admission control, classification and prior/scheduler.The traditional IP network only supports single service model that is the Best-Effort in which any packet is transmitted in the way of FIFO. But it is a important problem, which must be solved, to provide different service to the different client or operation. So the IntServ model and the DiffServ model are invented to solve this problem.The PBNM architecture The PBNM means that network device may had capability to access information, transmit information, spy and configure the device, depending on the policies. The advantage of the PBNM is that it could transform the complex business rules of communication into the control of the action of device or configure parameter. The PBNM architecture is composed of three important components:PDP: The PDP generally takes the form of a policy server, which directly interacts with PEPs such as routers, switches and firewalls. PDP's decisions are based on policies retrieved from the policy repository, as well as other management entities. Further, it fine-tunes the policy information that has been entered into the PBNM system and requires functionality for: Retrieving and evaluating policies, detecting any policy conflicts and providing resolutions.PEP: the PEP receive and enforce decisions from the PDP, thus the PEP enforces policies at the packet level. PEPs are normally implemented on network devices, such as routers, switches, network access servers (NAS) and VoIP gateways. The functionality of PEP includes:1.Requesting policy-based decisions from one or more PDPs.2.Applying actions according to PDP decisions based on relevant policies and network status.3.Caching policy decisions for future use.4. Providing feedback to the PDP regarding the results of the PEP-based installed policy. Policy Repository:Usually, policies and information of network source are stored in Policy Repository. The PBNM architecture assumes that multiple policy systems may need to interoperate within a single domain, as well as sharing the same policy information. For interoperable standard policy storage, the LDAP standard directory structure is normally used.The model of PBNM management: Outsourcing Policy Model:If the PEP is unable to resolve the signalled events (associated with end-to-end protocols such as RSVP) based on policy criteria, it outsource the decision-making to a PDP. The PDP receives such a policy decision request along with policy elements from PEP, and decides whether or not to grant these requests based on the relevance of the policy. Reservation. This model is sometimes referred to as the "pull" model, or the "reactive" model, since PEP pulls policy decisions from the PDP, while the PDP responds according to the PEP's requests.Policy Provisioning Model:The PDP predicts future configuration needs, and proactively provisions resources accordingly. It "pushes" configuration information to the PEPs. The policy-provisioning model is most commonly used for controlling overall network policies for non-signalled events such as IP service differentiation (DiffServ), or configuring devices. The PDP sends policy elements to the PEP and other network devices based on policy updates or requests entered from external entities such as a management console. These policy rules are distributed over the network in real-time, and the PDP determines whether or not to install the policy based on various criteria such as applicable time constraints and device enforcement capabilities.The communication Protocol in PBNMCOPSThe IETF has developed COPS. Compared with SNMP, COPS provides a more proactive and global view of network management. COPS is a protocol designed to exchang...
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