Path computation element: Difference between revisions

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In [[computer networks]], a '''path computation element''' (PCE) is a system component, application, or [[network node]] that is capable of determining and finding a suitable route for conveying data between a source and a destination.<ref name=pce-rfc>RFC 4655, [http://www.ietf.org/rfc/rfc4655.txt "A Path Computation Element (PCE)-Based Architecture"]</ref>

{{context|date=July 2008}}

Routing is the process of finding a suitable route for conveying data between a source and one or a set of destination. Routing can be subject to a set of constraints, like QoS, policy, or price. Constraint-based path computation is a strategic component of traffic engineering in [[MPLS]] and [[GMPLS]] networks. It is used to determine the path through the network that traffic should follow, and provides the route for each [[Label Switched Path]] (LSP) that is set up.

==Description==

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 usually available at a network element, yet may still need to be more dynamic than can be provided by a management system.

Routing is the process of finding a suitable route for conveying data between a source and one or a set of destination. Routing can be subject to a set of constraints, likesuch as [[quality of service]] (QoS), policy, or price. Constraint-based path computation is a strategic component of traffic engineering in [[MPLS]], [[GMPLS]] and [[GMPLSSegment Routing]] networks. It is used to determine the path through the network that traffic should follow, and provides the route for each [[Labellabel-switched Switched Pathpath]] (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 usuallytypically available at a network element, yet may still need to be more dynamic than can be provided by a management system.

A '''Path Computation Element''' (PCE) is defined by the Internet Engineering Task Force ([[IETF]]) in ''RFC 4655'' <ref name=pce-rfc>RFC 4655, [http://www.ietf.org/http://www.ietf.org/rfc/rfc4655.txt "A Path Computation Element (PCE)-Based Architecture"]</ref>, as

<blockquote>

An entity (component, application, or network node) that is capable of computing a network path or route based on a network graph and applying computational constraints

</blockquote>

Thus, a PCE is an entity capable of computing complex paths for a single or set of services. A PCE might be a [[Computer network|network]] node, network management station, or dedicated computational platform whichthat is resource-aware of the network resources and has the ability to consider multiple constraints for sophisticated path computation. PCE applications includecompute computinglabel-switched Label Switched Pathspaths for MPLS and GMPLS Traffictraffic Engineeringengineering. The various components of the PCE architecture are in the process of being standardized by the [[IETF]]'s ''PCE Working Group''.<ref name=pce>IETF's Working Group, [http://www.ietf.org/html.charters/pce-charter.html "Path Computation Element (pce)"] {{webarchive|url=https://web.archive.org/web/20090710130634/http://www.ietf.org/html.charters/pce-charter.html |date=2009-07-10 }}</ref>.

PCE represents a vision of networks that separates route computations from the signaling of end-to-end connections and from actual [[packet forwarding]]. There is a basic tutorial on PCE as presented at ISOCORE's MPLS2008 conference<ref name=tutorial>Basic PCE tutorial [http://www.olddog.co.uk/Farrel_PCE_Tutorial.pdf "PCE Tutorial"]</ref> and a tutorial on advanced PCE as presented at ISOCORE's SDN/MPLS 2014 conference.<ref name=AdvTutorial>Advanced PCE tutorial [http://www.olddog.co.uk/AdvancedPCE.pdf "Advanced PCE Tutorial"]</ref>

PCE represents a modern vision of networks where route computations should more or less be separated from actual packet forwarding.

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)<ref name=H-PCE>RFC 6805 [http://www.rfc-editor.org/rfc/rfc6805.txt "Hierarchical PCE"]</ref> and both Stateful and Active PCE.<ref name=Stateful>RFC 7399 [http://www.rfc-editor.org/rfc/rfc7399.txt "Unanswered Questions in the Path Computation Element Architecture"]</ref>

==References==

<references/>

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)<ref name=PCEP>RFC 5440 [http://www.rfc-editor.org/rfc/rfc5440.txt "Path Computation Element Communications Protocol"]</ref> which runs over the [[Transmission Control Protocol]] (TCP).

==Specifications==

* http://www.ietf.org/html.charters/pce-charter.html

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 project<ref name=PACE>PACE [http://www.ict-pace.net/ "PACE: Next Steps in PAth Computation Element (PCE) Architectures"] {{Webarchive|url=https://web.archive.org/web/20161024222557/http://www.ict-pace.net/ |date=2016-10-24 }}</ref> which is funded by the [[European Union]]'s Seventh Framework Programme for research, technological development and demonstration under grant agreement no. 619712.

==External links==

* [http://www.manolodominguez.com Website containing papers related to PCE]

The PACE project has developed a primer for those interested in PCE. It can be downloaded without charge from the PACE website.<ref name=primer>PCE Primer [https://web.archive.org/web/20160304071829/http://www.ict-pace.net/files/3313/8929/2782/PCE_Primer.pdf "PACE project PCE Primer"]</ref>

== PCE extensions ==

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

* Interdomain PCE discovering extensions<ref>{{cite web

|url = http://manolodominguez.com/content/common/pdf/cv/publications/JITEL2008.pdf

|title = Descubrimiento de PCE inter-AS: una aportación a la computación de LSP en sistemas multidominio.

|author = M. Domínguez-Dorado, José-Luis González-Sánchez, J. Domingo-Pascual. Libro de actas de las VII Jornadas de Ingeniería Telemática (JITEL'08) Págs. 80–86. ISBN 978-84-612-5474-3. Alcalá de Henares (ESPAÑA), Septiembre de 2008.

}}{{dead link|date=March 2018 |bot=InternetArchiveBot |fix-attempted=yes }}</ref><ref>{{cite book

|url = http://manolodominguez.com/content/common/pdf/cv/publications/NETWORKS2008.pdf

|title = PILEP: a contribution to PCE-based interdomain path computation.

|author = M. Domínguez-Dorado, José-Luis González-Sánchez, J. Domingo-Pascual. Proceedings of the 13th International Telecommunications Network Strategy and Planning Symposium (NETWORKS'08). pp. 1–7. IEEE catalog number CFP08568-USB. ISBN 978-963-8111-68-5. DOI 10.1109/NETWKS.2008.4763712. Budapest (HUNGARY), October, 2008.

|year = 2008

|pages = 1–17

|doi = 10.1109/NETWKS.2008.4763712

|hdl = 2117/12929

|isbn = 978-963-8111-68-5

|s2cid = 18470823

|url-status = dead

|archiveurl = https://web.archive.org/web/20130410161732/http://www.manolodominguez.com/content/common/pdf/cv/publications/NETWORKS2008.pdf

|archivedate = 2013-04-10

}}</ref><ref>{{cite web

|url = http://manolodominguez.com/content/common/pdf/cv/publications/CITA2009.pdf

|title = RI-CUBE: Dotando al PCE de información abstracta de ingeniería de tráfico interdominio.

|author = M. Domínguez-Dorado, José-Luis González-Sánchez, J. Domingo-Pascual, J. Carmona-Murillo. Proceedings of the V Iberoamerican Conference on Telematics (CITA'09). pp. 14–21. ISBN 978-84-613-2679-2. Gijón (SPAIN), May, 2009.

}}{{dead link|date=March 2018 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>

== References ==

{{reflist}}

==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 }}

[[Category:TelephonyComputer networking]]