AS PCE (Active Stateful Path Computation Element)

Active Stateful Path Computation Element (AS PCE) is a component of the Software Defined Networking (SDN) architecture. It is responsible for computing end-to-end paths for traffic flows across a network, taking into account various network constraints and policies. AS PCE is an evolution of the Path Computation Element (PCE) concept, which is used to compute paths for Traffic Engineering (TE) in Multiprotocol Label Switching (MPLS) networks.

AS PCE has two primary functions: path computation and path instantiation. Path computation refers to the process of finding an optimal path for a given traffic flow based on a set of network constraints, such as available bandwidth, link and node resources, and traffic demand. Path instantiation refers to the process of programming network devices to establish the computed path and direct traffic flows along it.

AS PCE is designed to be stateful, meaning that it maintains a persistent view of the network's topology and resources, as well as the traffic demands placed on it. This stateful capability allows AS PCE to compute paths that take into account the current state of the network, rather than relying solely on static network maps. By maintaining a persistent view of the network, AS PCE can also perform traffic engineering functions, such as load balancing and path optimization, in real-time.

AS PCE is also designed to be active, meaning that it can initiate path computation and instantiation requests on its own, without relying on external triggers. This is in contrast to the traditional PCE, which is typically reactive and waits for path computation requests from other network elements, such as Path Control and Management Plane (PCMP) clients or Border Gateway Protocol (BGP) speakers.

The main benefits of AS PCE are improved network scalability, flexibility, and traffic engineering capabilities. By offloading path computation and instantiation tasks from network devices, AS PCE enables them to focus on forwarding traffic and reducing packet drops. AS PCE also allows network operators to deploy new services and applications quickly, without having to modify network devices or configurations manually.

AS PCE architecture consists of several functional components. These components include the Path Computation Element Controller (PCEC), the Path Computation Element Protocol (PCEP), the Path Computation Element Database (PCE-DB), and the Path Computation Element Client (PCE-Client).

The PCEC is the central component of the AS PCE architecture. It receives path computation requests from PCE clients and uses the PCEP to communicate with network devices to instantiate the computed paths. The PCEC also maintains a view of the network's topology and resources through the PCE-DB.

The PCEP is the protocol used by PCE clients to communicate with the PCEC. The PCEP is responsible for requesting path computations and receiving responses from the PCEC, as well as for requesting and receiving path instantiation requests.

The PCE-DB is the database used by the PCEC to store and manage network topology and resource information. The PCE-DB is responsible for collecting and updating information from network devices, such as link-state information, traffic demand, and available bandwidth.

The PCE-Client is the component that sends path computation requests to the PCEC. The PCE-Client can be implemented in various network devices, such as routers and switches, or in external management systems.

AS PCE has several use cases, such as traffic engineering in Service Provider (SP) networks, network optimization in data centers, and cloud service orchestration. In SP networks, AS PCE can be used to optimize traffic flow across multiple Autonomous Systems (AS) and to manage congestion and network failures. In data centers, AS PCE can be used to optimize traffic flow between servers and storage systems, as well as to provide real-time traffic engineering for different applications running in the data center. In cloud service orchestration, AS PCE can be used to optimize traffic flow between different cloud data centers and to provide load balancing for cloud services.

In conclusion, AS PCE is a key component of the SDN architecture that provides advanced traffic engineering capabilities for modern networks. Its stateful and active design enables it to compute optimal paths in real-time, taking into account the current state of the network. AS PCE improves network scalability, flexibility, and performance by offloading path computation and instantiation tasks from network devices and enabling network operators to deploy new services and applications quickly. With its numerous use cases and benefits, AS PCE is an essential technology for network operators and service providers looking to optimize their networks and improve their users' quality of experience.