computer networks A computer network is a set of computers sharing resources located on or provided by network nodes. The computers use common communication protocols over digital interconnections to communicate with each other. These interconnections are ...

, a path computation element (PCE) is a system component, application, or

network node In telecommunications networks, a node (, ‘knot’) is either a redistribution point or a communication endpoint. The definition of a node depends on the network and protocol layer referred to. A physical network node is an electronic devic ...

that is capable of determining and finding a suitable route for conveying data between a source and a destination.RFC 4655
"A Path Computation Element (PCE)-Based Architecture"
/ref>

Description

Routing can be subject to a set of constraints, such as

quality of service Quality of service (QoS) is the description or measurement of the overall performance of a service, such as a telephony or computer network, or a cloud computing service, particularly the performance seen by the users of the network. To quantitat ...

(QoS), policy, or price. Constraint-based path computation is a strategic component of traffic engineering in

MPLS Multiprotocol Label Switching (MPLS) is a routing technique in telecommunications networks that directs data from one node to the next based on labels rather than network addresses. Whereas network addresses identify endpoints the labels identif ...

GMPLS Generalized Multi-Protocol Label Switching (GMPLS) is a protocol suite extending MPLS to manage further classes of interfaces and switching technologies other than packet interfaces and switching, such as time-division multiplexing, layer-2 switchin ...

and Segment Routing networks. It is used to determine the path through the network that traffic should follow, and provides the route for each

Label Switched Path Multiprotocol Label Switching (MPLS) is a routing technique in telecommunications networks that directs data from one node to the next based on labels rather than network addresses. Whereas network addresses identify endpoints the labels identif ...

(LSP) that is set up. Path computation has previously been performed either in a management system or at the head end of each LSP. But path computation in large, multi-domain networks may be very complex and may require more computational power and network information than is typically available at a network element, yet may still need to be more dynamic than can be provided by a management system. Thus, a PCE is an entity capable of computing paths for a single or set of services. A PCE might be a

network Network, networking and networked may refer to: Science and technology * Network theory, the study of graphs as a representation of relations between discrete objects * Network science, an academic field that studies complex networks Mathematics ...

node, network management station, or dedicated computational platform that is resource-aware and has the ability to consider multiple constraints for sophisticated path computation. PCE applications compute label switched paths for MPLS and GMPLS traffic engineering. The various components of the PCE architecture are in the process of being standardized by the

IETF The Internet Engineering Task Force (IETF) is a standards organization for the Internet and is responsible for the technical standards that make up the Internet protocol suite (TCP/IP). It has no formal membership roster or requirements and ...

's ''PCE Working Group''.IETF's Working Group
"Path Computation Element (pce)"
PCE represents a vision of networks that separates route computations from the signaling of end-to-end connections and from actual

packet forwarding Packet forwarding is the relaying of packets from one network segment to another by nodes in a computer network. The network layer in the OSI model is responsible for packet forwarding. Models The simplest forwarding modelunicastinginvolve ...

. There is a basic tutorial on PCE as presented at ISOCORE's MPLS2008 conferenceBasic PCE tutoria
"PCE Tutorial"
/ref> and a tutorial on advanced PCE as presented at ISOCORE's SDN/MPLS 2014 conference.Advanced PCE tutoria
"Advanced PCE Tutorial"
/ref> Since the early days, the PCE architecture has evolved considerably to encompass more sophisticated concepts and allow application to more complicated network scenarios. This evolution includes Hierarchical PCE (H-PCE)RFC 680
"Hierarchical PCE"
/ref> and both Stateful and Active PCE.RFC 739
"Unanswered Questions in the Path Computation Element Architecture"
/ref> A potential deployment of PCE separates the computation element from the client (the PCC) that request computation services. Communications between the PCE and PCC are achieved using the Path Computation Element Communication Protocol (PCEP)RFC 544
"Path Computation Element Communications Protocol"
/ref> which runs over the

Transmission Control Protocol The Transmission Control Protocol (TCP) is one of the main protocols of the Internet protocol suite. It originated in the initial network implementation in which it complemented the Internet Protocol (IP). Therefore, the entire suite is common ...

(TCP). As the architecture has evolved, new protocol extensions have been developed to add functionality to support new applications and the new architectural elements. These developments are tracked by the PACE projectPAC
"PACE: Next Steps in PAth Computation Element (PCE) Architectures"
/ref> which is funded by the

European Union The European Union (EU) is a supranational political and economic union of member states that are located primarily in Europe. The union has a total area of and an estimated total population of about 447million. The EU has often been ...

's Seventh Framework Programme for research, technological development and demonstration under grant agreement no. 619712. The PACE project has developed a primer for those interested in PCE. It can be downloaded without charge from the PACE website.PCE Prime
"PACE project PCE Primer"
/ref>

PCE extensions

There are several PCE extensions to achieve different goals. For example: * Interdomain PCE discovering extensions

References

Specifications

* {{cite web , url=http://www.ietf.org/html.charters/pce-charter.html , title=Path Computation Element (pce) – Charter , publisher=Ietf.org , date=2012-07-03 , accessdate=2012-07-08 , url-status=dead , archiveurl=https://web.archive.org/web/20090710130634/http://www.ietf.org/html.charters/pce-charter.html , archivedate=2009-07-10 Computer networking