Abstract

Links in an IP network are unidirectional but currently are routed over bidirectional optical circuits with identical AZ and ZA capacities. Potentially there could be savings if the two directions of an optical circuit could be treated independently. In this study of possible savings, we have quantified the asymmetry of traffic on a current large IP backbone. A theoretical greenfield network with similarly asymmetric traffic is modeled, and it is shown that the use of unidirectional circuits to satisfy traffic demands provides significant equipment savings. We consider this study of the benefits of this approach to be a first step in deciding whether it makes economic sense to tackle the hurdles that would face such a major change in network design and operations.

© 2013 Optical Society of America

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Errata

Sheryl L. Woodward, Weiyi Zhang, Balagangadhar G. Bathula, Gagan Choudhury, Rakesh K. Sinha, Mark D. Feuer, John Strand, and Angela L. Chiu, "Asymmetric Optical Connections for Improved Network Efficiency: Erratum," J. Opt. Commun. Netw. 5, 1468-1468 (2013)
https://www.osapublishing.org/jocn/abstract.cfm?uri=jocn-5-12-1468

References

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  1. “Interfaces for the optical transport network,” [Online]. Available: http://www.itu.int/rec/T-REC-G.709-201202-I/en .
  2. The DARPA CORONET topology for Contiguous United States (CONUS) [Online]. Available: http://monarchna.com/topology.html .
  3. R. D. Doverspike and J. Yates, “Optical network management and control,” Proc. IEEE, vol. 100, no. 5, pp. 1092–1104, 2012.
    [CrossRef]
  4. V. Hutcheon, “OTN to enable flexible networks,” in Nat. Fiber Optic Engineers Conf., 2011.
  5. A. L. Chiu, G. Choudhury, R. Doverspike, and G. Li, “Restoration design in IP over reconfigurable all-optical networks,” in Network and Parallel Computing. Springer, 2007, pp. 315–333.
  6. G. L. Choudhury and J. G. Klincewicz, “Survivable IP link topology design in an IP-over-WDM architecture,” in 7th Int. Workshop on Design of Reliable Communication Networks, 2009, pp. 147–152.

2012

R. D. Doverspike and J. Yates, “Optical network management and control,” Proc. IEEE, vol. 100, no. 5, pp. 1092–1104, 2012.
[CrossRef]

Chiu, A. L.

A. L. Chiu, G. Choudhury, R. Doverspike, and G. Li, “Restoration design in IP over reconfigurable all-optical networks,” in Network and Parallel Computing. Springer, 2007, pp. 315–333.

Choudhury, G.

A. L. Chiu, G. Choudhury, R. Doverspike, and G. Li, “Restoration design in IP over reconfigurable all-optical networks,” in Network and Parallel Computing. Springer, 2007, pp. 315–333.

Choudhury, G. L.

G. L. Choudhury and J. G. Klincewicz, “Survivable IP link topology design in an IP-over-WDM architecture,” in 7th Int. Workshop on Design of Reliable Communication Networks, 2009, pp. 147–152.

Doverspike, R.

A. L. Chiu, G. Choudhury, R. Doverspike, and G. Li, “Restoration design in IP over reconfigurable all-optical networks,” in Network and Parallel Computing. Springer, 2007, pp. 315–333.

Doverspike, R. D.

R. D. Doverspike and J. Yates, “Optical network management and control,” Proc. IEEE, vol. 100, no. 5, pp. 1092–1104, 2012.
[CrossRef]

Hutcheon, V.

V. Hutcheon, “OTN to enable flexible networks,” in Nat. Fiber Optic Engineers Conf., 2011.

Klincewicz, J. G.

G. L. Choudhury and J. G. Klincewicz, “Survivable IP link topology design in an IP-over-WDM architecture,” in 7th Int. Workshop on Design of Reliable Communication Networks, 2009, pp. 147–152.

Li, G.

A. L. Chiu, G. Choudhury, R. Doverspike, and G. Li, “Restoration design in IP over reconfigurable all-optical networks,” in Network and Parallel Computing. Springer, 2007, pp. 315–333.

Yates, J.

R. D. Doverspike and J. Yates, “Optical network management and control,” Proc. IEEE, vol. 100, no. 5, pp. 1092–1104, 2012.
[CrossRef]

Proc. IEEE

R. D. Doverspike and J. Yates, “Optical network management and control,” Proc. IEEE, vol. 100, no. 5, pp. 1092–1104, 2012.
[CrossRef]

Other

V. Hutcheon, “OTN to enable flexible networks,” in Nat. Fiber Optic Engineers Conf., 2011.

A. L. Chiu, G. Choudhury, R. Doverspike, and G. Li, “Restoration design in IP over reconfigurable all-optical networks,” in Network and Parallel Computing. Springer, 2007, pp. 315–333.

G. L. Choudhury and J. G. Klincewicz, “Survivable IP link topology design in an IP-over-WDM architecture,” in 7th Int. Workshop on Design of Reliable Communication Networks, 2009, pp. 147–152.

“Interfaces for the optical transport network,” [Online]. Available: http://www.itu.int/rec/T-REC-G.709-201202-I/en .

The DARPA CORONET topology for Contiguous United States (CONUS) [Online]. Available: http://monarchna.com/topology.html .

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Figures (11)

Fig. 1.
Fig. 1.

Peak traffic measured over an eight-week interval on links of a large backbone network. For each link (az), AZ is the direction with the higher peak traffic level. The links are shown ordered by the peak traffic level from AZ. The network symmetry calculated from this data was ρnetwork=0.50.

Fig. 2.
Fig. 2.

Network symmetry of the 57 links calculated weekly over the same eight-week period. For each link the AZ direction was defined as the direction with the higher peak traffic over the entire eight-week period and was held constant in calculating the weekly network symmetry.

Fig. 3.
Fig. 3.

Symmetry of the top 10 links calculated weekly over the same eight-week period. For each link the AZ direction was defined as the direction with the higher peak traffic over the entire eight-week period. The 10 links presented are those with the greatest peak traffic from AZ. The dominant traffic direction for one of these 10 links (link no. 4) changed during the eight-week interval. Its traffic in each direction is shown in Fig. 4.

Fig. 4.
Fig. 4.

Peak traffic level per week in each direction for link 4. The amount of traffic from AZ varied greatly during this period. Such variations can be due to either network events (e.g., scheduled maintenance) or variations in the underlying traffic demands.

Fig. 5.
Fig. 5.

Network topology used in our study is the CORONET CONUS topology [2] (shown in blue; nodes are circles and links are dashed lines) augmented with 13 additional nodes (red squares) and 26 links (red lines). Many of the augmented links are too short to see in this figure, as the additional nodes connect to a nearby CORONET node.

Fig. 6.
Fig. 6.

Traffic on each link in the traffic model used in our network studies. The network asymmetry calculated from this data was ρnetwork=0.43. There are 56 links at the IP layer. As in Fig. 1, for each link (az), AZ is the direction with the higher peak traffic level, and the links were ordered by the peak traffic level from AZ.

Fig. 7.
Fig. 7.

Assumed network architecture. Each DWDM link carries up to (e.g.) 80 wavelengths and is routed over individual fiber(s) (not shown). The IP/OTN and OTN/ROADM layer interfaces are OTN formatted and (today) normally bidirectional with symmetric capacity. The IP links are unidirectional. We consider architectures where the routers are connected to either the OTN layer or directly to the ROADM layer.

Fig. 8.
Fig. 8.

Examples of the network planning for a link between A and Z when (a) bidirectional equipment or (b) unidirectional equipment is used. In (a) the link between nodes A and Z requires a 60 Gbps link. Because 60 Gbps exceeds the capacity of a wavelength (40 Gbps in our model) the OTN layer is bypassed, and the traffic is carried between locations A and Z on two wavelengths (the black dashed lines show how data flows between the layers, from the router to the ROADM layer). ROADMs enable these wavelengths to express through Location B without regeneration. In (b) the link from A to Z requires a 60 Gbps link, but the link from Z to A requires only 20 Gbps. Once again, the 60 Gbps link is carried directly on the ROADM layer, and expresses through Location B. However, the 20 Gbps link utilizes the OTN layer, so that it can be multiplexed with OTN circuits serving other links in the network. For this reason the wavelength serving this link does not express through ROADM B.

Fig. 9.
Fig. 9.

Traffic on each link for both working traffic plus the additional capacity that must be present for mesh protection (the maximum link usage in case of any single failure in the network). The design uses 58 links (two additional links are added for meshprotection). ρnetwork=0.49.

Fig. 10.
Fig. 10.

Number of DWDM transmitters (which equals the number of DWDM receivers) needed for each network design. A bidirectional transponder has both a DWDM transmitter and receiver, while the unidirectional design uses transponders with just one or the other.

Fig. 11.
Fig. 11.

Relative costs of each network design. The costs include the router, OTN, and ROADM layers, including transponders.

Tables (1)

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TABLE I Relative Port Costs

Equations (5)

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ρ=min(t(az),t(za))max(t(az),t(za)),
ρnetwork=i[t(ZiAi)]i[t(AiZi)],
t(ZiAi)=min(t(aizi),t(ziai))andt(AiZi)=max(t(aizi),t(ziai)).
t8wks(AiZi)=max(t8wks(aizi),t8wks(ziai)).
t(AiZi)=max(t1wk(aizi),t1wk(ziai))