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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 20, Iss. 28 — Dec. 31, 2012
  • pp: 29137–29142
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Inter-layer traffic engineering with hierarchical-PCE in MPLS-TP over wavelength switched optical networks

R. Casellas, R. Martinez, R. Muñoz, L. Liu, T. Tsuritani, and I. Morita  »View Author Affiliations


Optics Express, Vol. 20, Issue 28, pp. 29137-29142 (2012)
http://dx.doi.org/10.1364/OE.20.029137


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Abstract

We present the implementation and validation of an Inter-layer Traffic Engineering (TE) architecture based on a hierarchical path computation element (PCE), where the parent PCE is notified of established optical layer Label Switched Paths that induce packet traffic engineering (TE) links, thus not requiring full topology visibility. We summarize the architecture, the control plane extensions and its experimental evaluation in a control plane testbed.

© 2012 OSA

1. Introduction

A multi-region network (MRN) [1

1. K. Shiomoto, D. Papadimitriou, JL. Le Roux, M. Vigoureux, and D. Brungard, “Requirements for GMPLS-based multi-region and multi-layer networks (MRN/MLN),” IETF RFC 5212 (2008), http://tools.ietf.org/rfc/rfc5212.txt.

], combining a packet-switching layer with an optical circuit-switching one, provides both the bandwidth flexibility and granularity of packet switching – including statistical multiplexing – and the cost-efficiency and high bandwidth capacity of the optical layer. Such a MRN enables advanced aggregation and grooming, and both the MPLS-TP and WSON technologies are mature and well positioned for such network deployments. From the operators’ perspective, a control plane provides dynamic provisioning and recovery, along with an efficient usage of resources. In particular, inter-layer Traffic Engineering (TE) refers to the process of optimizing network resource utilization globally, taking into account all layers rather than optimizing resource utilization at each layer independently [2

2. E. Oki, T. Takeda, JL. Le Roux, and A. Farrel, “Framework for PCE-based inter-layer MPLS and GMPLS traffic engineering,” IETF RFC 5623, (2009), http://tools.ietf.org/rfc/rfc5623.txt.

].

In a MRN it is often stated that a single and unified control plane instance, with a common vision of all the switching layers constituting the network, provides the required inter-layer cooperation [3

3. R. Martinez, R. Casellas, and R. Muñoz, “Experimental validation and evaluation of a GMPLS unified control plane in multi-layer (MPLS-TP/WSON) networks,” NFOEC paper NTu2J.1 (2012), http://www.opticsinfobase.org/abstract.cfm?URI=NFOEC-2012-NTu2J.1.

]. Since the path computation function has full visibility of the topology and network resources, it is thus able to benefit from multi-layer TE strategies. In practice, a unified control plane in a multi-vendor setting may present scalability and/or inter-operability problems, commonly addressed by segmenting the network or defining different domains (e.g. OSPF-TE areas), which may preclude such Inter-layer cooperation. Fortunately, inter-layer TE does not require a unified control plane with full topology visibility. In general, Inter-Layer TE relies on both an optimal inter-layer path computation (I) and the automated provisioning of all involved layers (II).

2. Inter-layer path computation element

Inter-layer TE is an application domain for Path Computation Elements [2

2. E. Oki, T. Takeda, JL. Le Roux, and A. Farrel, “Framework for PCE-based inter-layer MPLS and GMPLS traffic engineering,” IETF RFC 5623, (2009), http://tools.ietf.org/rfc/rfc5623.txt.

] in collaborative settings, with augmented functionality (e.g. a Virtual Net-work Topology Manager or VNTM), although the exact VNTM interfaces and protocols are to be defined. Requirement (I) relies on coordinated path computation and/or full topology visibility, by means of either a single PCE with topology visibility of all layers or a per-layer PCE. In the later case, each PCE knows its layer topology and relies on PCEP procedures to ensure that the optimal region boundary nodes are selected. (II) requires to provision all (server/client) layers either by: triggered hierarchical signaling, where the establishment of a client LSP triggers a server layer connection at region boundaries (Fig. 1), or layered provisioning, in which an entity (e.g., NMS or VNTM) is able to coordinate the ordered, layered establishment of server segments and finally the client layer.

Fig. 1 Triggered hierarchical signaling of a server (LSC) LSP during signaling a client (PSC) LSP

3. Inter-layer traffic engineering with a hierarchical PCE

Fig. 2 Wireshark captures of the ERO object computed by the PCE. A high number represents a dynamically allocated identifier during signaling.

4. Control plane extensions

Fig. 3 H-PCE path computation procedures
Fig. 4 14- node testbed with a multi region network comprising 3 OSPF-TE areas and a 2-level H-PCE

Standard MLN/MRN RSVP-TE and OSPF-TE procedures are used in this work, extensions covering the PCEP protocol: parent/children domain relationships and mappings rely on PCE ID and DOMAIN ID TLVs included in the PCEP OPEN object. Endpoint reachability information is aggregated and announced using TLVs that contain CIDR IPv4 prefix sub-objects. For topology summarization, within a domain, domain border nodes (i.e., ABRs) are learnt from Summary and External OSPF LSAs and forwarded to the parent. In all cases, PCEP Notifications are used to wrap topology updates in the vertical direction, using TLVs (Fig. 4, top).

5. Experimental performance evaluation

Path computation latency depends on several factors; a notable one being the synchronization / mutual exclusion to access the TED (Fig. 5(a)): path computation may be delayed significantly, resulting from 25ms with no contention to 50ms when also processing topology updates.

Fig. 5 Experimental results obtained with the multi-layer, multi-domain scenario

Finally, a simplified version of the H-PCE architecture for multi-layer path computation has been implemented and deployed in a multi-partner control plane testbed, extending the STRONGEST Distributed Control Plane infrastructure as explained in [6

6. F. Paolucci, O. Gonzalez de Dios, R. Casellas, S. Duhovnikov, P. Castoldi, R. Munoz, and R. Martinez, “Experimenting hierarchical PCE architecture in a distributed multi-platform control plane testbed,” OFC paper OM3G.3 (2012) http://www.opticsinfobase.org/abstract.cfm?URI=OFC-2012-OM3G.3.

]. The testbed interconnects five European research institutions, located in Madrid (Telefónica I+D), Barcelona (CTTC), Pisa (CNIT and Nextworks) and Munich (Nokia Siemens Networks, NSN), in the scope of a joint collaboration between the FP 7 IP STRONGEST Project [7

7. ICT FP7 STRONGEST Project, “Scalable, tunable and resilient optical networks guaranteeing extremely-high speed transport,” www.ict-strongest.eu.

], integrating the Optical Burst Switching (OBS) Path Computation Elements from the FP 7 MAINS Project [8

8. IST FP7 MAINS Project, “Metro architectures enabling sub-wavelengths,” www.ist-mains.eu.

]. The path computation scenario was successfully demonstrated in [9

9. Workshop on control plane architectures for new optical switching technologies enabling flexibility in time, frequency and space domains, collocated with ECOC(2012).

], with a network environment made of several interconnected WSON and OBS domains. The WSON domains are able to provide lambda switched paths. The OBS domains are based on the Optical Burst Switching paradigm, a sub-wavelength technology able to fill wavelengths. End-to-end OBS paths starting in one domain and ending in a different domain are possible using wavelengths provided by the multi-domain WSON network (see Fig. 6).

Fig. 6 Multi-layer multi-domain control plane testbed used in the STRONGEST / MAINS collaboration, showing the interconnection of GMPLS controlled OBS domains via a WSON

6. Conclusions

We have presented a functional architecture to enable inter-layer TE minimizing topology visibility requirements and improving scalability. Our approach uses an H-PCE model in which the parent PCE ensures domain sequence and end-to-end path optimality leveraging existing FAs while triggering new ones using hierarchical signaling. We have implemented the solution, qualitatively validated in a testbed.

Acknowledgments

This work has been partially funded by Spanish MINECO project DORADO (TEC2009-07995), and by the EC FP7 IP project STRONGEST grant no 247674. The authors would like to thank R. Vilalta, O. González de Dios, G. Bernini, F. Paolucci, G. Carozzo, G. Landi and C. Margaria for their support of this work and the multi-partner testbed validation.

References and links

1.

K. Shiomoto, D. Papadimitriou, JL. Le Roux, M. Vigoureux, and D. Brungard, “Requirements for GMPLS-based multi-region and multi-layer networks (MRN/MLN),” IETF RFC 5212 (2008), http://tools.ietf.org/rfc/rfc5212.txt.

2.

E. Oki, T. Takeda, JL. Le Roux, and A. Farrel, “Framework for PCE-based inter-layer MPLS and GMPLS traffic engineering,” IETF RFC 5623, (2009), http://tools.ietf.org/rfc/rfc5623.txt.

3.

R. Martinez, R. Casellas, and R. Muñoz, “Experimental validation and evaluation of a GMPLS unified control plane in multi-layer (MPLS-TP/WSON) networks,” NFOEC paper NTu2J.1 (2012), http://www.opticsinfobase.org/abstract.cfm?URI=NFOEC-2012-NTu2J.1.

4.

R. Casellas, R. Martinez, R. Muñoz, L. Liu, T. Tsuritani, I. Morita, and M. Tsurusawa, “Dynamic virtual link mesh topology aggregation in multi-domain translucent WSON with hierarchical-PCE,” Opt. Express 19, B611–B620 (2011), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-19-26-B611. [CrossRef]

5.

F. Zhang, D. Li, F. Javier, Jimenez Chico, O. Gonzalez de Dios, and C. Margaria, “GMPLS-based hierarchy LSP creation in multi-region and multi-layer networks,” IETF work in progress, http://tools.ietf.org/html/draft-zhang-ccamp-gmpls-h-lsp-mln-04.

6.

F. Paolucci, O. Gonzalez de Dios, R. Casellas, S. Duhovnikov, P. Castoldi, R. Munoz, and R. Martinez, “Experimenting hierarchical PCE architecture in a distributed multi-platform control plane testbed,” OFC paper OM3G.3 (2012) http://www.opticsinfobase.org/abstract.cfm?URI=OFC-2012-OM3G.3.

7.

ICT FP7 STRONGEST Project, “Scalable, tunable and resilient optical networks guaranteeing extremely-high speed transport,” www.ict-strongest.eu.

8.

IST FP7 MAINS Project, “Metro architectures enabling sub-wavelengths,” www.ist-mains.eu.

9.

Workshop on control plane architectures for new optical switching technologies enabling flexibility in time, frequency and space domains, collocated with ECOC(2012).

OCIS Codes
(060.4250) Fiber optics and optical communications : Networks
(060.4258) Fiber optics and optical communications : Networks, network topology

ToC Category:
Backbone and Core Networks

History
Original Manuscript: October 1, 2012
Revised Manuscript: November 28, 2012
Manuscript Accepted: November 29, 2012
Published: December 17, 2012

Virtual Issues
European Conference on Optical Communication 2012 (2012) Optics Express

Citation
R. Casellas, R. Martinez, R. Muñoz, L. Liu, T. Tsuritani, and I. Morita, "Inter-layer traffic engineering with hierarchical-PCE in MPLS-TP over wavelength switched optical networks," Opt. Express 20, 29137-29142 (2012)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-20-28-29137


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References

  1. K. Shiomoto, D. Papadimitriou, JL. Le Roux, M. Vigoureux, and D. Brungard, “Requirements for GMPLS-based multi-region and multi-layer networks (MRN/MLN),” IETF RFC 5212 (2008), http://tools.ietf.org/rfc/rfc5212.txt .
  2. E. Oki, T. Takeda, JL. Le Roux, and A. Farrel, “Framework for PCE-based inter-layer MPLS and GMPLS traffic engineering,” IETF RFC 5623, (2009), http://tools.ietf.org/rfc/rfc5623.txt .
  3. R. Martinez, R. Casellas, and R. Muñoz, “Experimental validation and evaluation of a GMPLS unified control plane in multi-layer (MPLS-TP/WSON) networks,” NFOEC paper NTu2J.1 (2012), http://www.opticsinfobase.org/abstract.cfm?URI=NFOEC-2012-NTu2J.1 .
  4. R. Casellas, R. Martinez, R. Muñoz, L. Liu, T. Tsuritani, I. Morita, and M. Tsurusawa, “Dynamic virtual link mesh topology aggregation in multi-domain translucent WSON with hierarchical-PCE,” Opt. Express19, B611–B620 (2011), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-19-26-B611 . [CrossRef]
  5. F. Zhang, D. Li, F. Javier, Jimenez Chico, O. Gonzalez de Dios, and C. Margaria, “GMPLS-based hierarchy LSP creation in multi-region and multi-layer networks,” IETF work in progress, http://tools.ietf.org/html/draft-zhang-ccamp-gmpls-h-lsp-mln-04 .
  6. F. Paolucci, O. Gonzalez de Dios, R. Casellas, S. Duhovnikov, P. Castoldi, R. Munoz, and R. Martinez, “Experimenting hierarchical PCE architecture in a distributed multi-platform control plane testbed,” OFC paper OM3G.3 (2012) http://www.opticsinfobase.org/abstract.cfm?URI=OFC-2012-OM3G.3 .
  7. ICT FP7 STRONGEST Project, “Scalable, tunable and resilient optical networks guaranteeing extremely-high speed transport,” www.ict-strongest.eu .
  8. IST FP7 MAINS Project, “Metro architectures enabling sub-wavelengths,” www.ist-mains.eu .
  9. Workshop on control plane architectures for new optical switching technologies enabling flexibility in time, frequency and space domains, collocated with ECOC(2012).

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