A content delivery network or content distribution network (CDN) using cloud resources such as storage and compute have started to emerge. Unlike traditional CDNs hosted on private data centers, cloud-based CDNs take advantage of the geographical availability and the pay-as-you-go model of cloud platforms. The Cloud-based CDNs (CCDNs) promote content-delivery-as-a-service cloud model. Though CDNs and CCDNs share similar functionalities, introduction of cloud impose additional challenges that have to be addressed for a successful CCDN deployment. Several papers have tried to address the issues and challenges around CDN with varying degree of success. However, to the best of our knowledge, there is no clear articulation of issues and challenge problems within the context of cloud-based CDNs. Hence, this paper aims to identify the open challenges in cloud-based CDNs. In this regard, we present an overview of cloud-based CDN followed by a detailed discussion on open challenges and research dimensions.

Content delivery networks, Cloud, Cloud-based CDN, pay-as-you-go model, content-delivery-as-a-service

[1] IDC, �Data Growth, Business Opportunities, and IT Imperatives�. Available: http://www.emc.com/leadership/digital- universe/2014iview/executive-summary.htm. Accessed: 10/09/2014.
[2]. Akamai, �The Importance of Delivering A
Great Online Video Experience�. Available: http://www.akamai.com/dl/reports/jupiter_onlinevideoexp.pdf. Accessed: 10/09/2014.
[3] IneoQuest, �The Case for Leveraging the Cloud for Video Service Assurance�. Available: http://www.ineoquest.com/wpcontent/uploads/2013/10/Whitepaper_Cloud_Services.pdf. Accessed: 10/09/2014
[4] Big Data & CDN, Available: http://www.slideshare.net/pavlobaron/bigdata-cdnoop2011-pavlo-baron, Accessed: 03/07/2014
[5]. Wang L, Kunze M, Tao J, Laszewski G (2011) �Towards building a cloud for scientific applications�. Adv Eng Softw 42(9):714�722
[6] Wang L, Fu C (2010), �Research advances in modern cyber infrastructure�. New GenerComput 28(2):111�112
[7] P. Mell and T. Grance, "The NIST definition of cloud computing (draft)," NIST special publication, vol. 800, p. 145, 2011.
[8] Mastin. P; �Is the Cloud a CDN Killer�, Available: http://cloudcomputing.sys-con.com/node/2628667. Accessed: 03/07/2014.
[9] Compton. K; �Marching towards cloudCDN� Available: http://blogs.cisco.com/sp/marching-towards-cloud-cdn/. Accessed: 03/07/2014.
[10] Hao Yin; Xuening Liu; Geyong Min; Chuang Lin, "Content delivery networks: a bridge between emerging applications and future IP networks," Network, IEEE , vol.24, no.4, pp.52,56, July-August 2010
[11] Li Ling; Ma Xiaozhen; Huang Yulan, "CDN cloud: A novel scheme for combining CDN and cloud computing," Measurement, Information and Control (ICMIC), 2013 International Conference on , vol.01, no., pp.687,690, 16-18 Aug. 2013.
[12] Lizhe Wang, Dan Chen, Jiaqi Zhao, Jie Tao:Resource management of distributed virtual machines. IJAHUC 10(2): 96-111 (2012) .
[13] Lizhe Wang, Dan Chen, Yangyang Hu, Yan Ma, Jian Wang: Towards enabling Cyberinfrastructure as a Service in Clouds. Computers & Electrical Engineering 39(1): 3-14 (2013).
[14] Microsoft Azure Cloud Services: http://www.windows.azure.com.Accessed: 10/09/2014 .
[15]AmazonCloudFront.http://aws.amazon.com/cloudfront/, Accessed: 10/09/2014
[16]. P. Mell and T. Grance, "The NIST definition of cloud computing (draft)," NIST special publication, vol. 800, p. 145, 2011.
[17]. K. Krauter, R. Buyya, et al., "A Taxonomy and Survey of Grid Resource Management Systems for Distributed Computing," Software: Practice and Experience (SPE), vol. 32, pp. 135-164, February 2002.
[18] L. Hui, "Realistic Workload Modeling and Its Performance Impacts in Large-Scale eScience Grids," IEEE Transactions on Parallel and Distributed Systems, vol. 21, pp. 480-493, 06/15 2010.
[19] IneoQuest, �The Case for Leveraging the Cloud for Video Service Assurance�. Available: http://www.ineoquest.com/wp-content/uploads/2013/10/Whitepaper_Cloud_Services.pdf. Accessed: 10/09/2014
[20] Akamai Technologies, Inc., www.akamai.com, 2014
[21]. Li. H; Zhong. L; Liu. J; Li. B; Xu. B, "Cost-Effective Partial Migration of VoD Services to Content Clouds," Cloud Computing (CLOUD), 2011 IEEE International Conference on, vol., no., pp.203,210, 4-9 July 2011
[22]. Zhang. X; Du. H; Chen. J-Q; Lin. Y; Zeng. L-J, "Ensure Data Security in Cloud Storage," Network Computing and Information Security (NCIS), 2011 International Conference on, vol.1, no., pp.284,287, 14-15 May 2011
[23]. No SQL, http://nosql-database.org/, Accessed: 8/06/2014 Wang. L, Pai. V and Peterson. L, �The Effectiveness of Request Redirection on CDN Robustness�,web.cs.wpi.edu/~rek/DCS/D04/CDN_Redirection.ppt, accessed: 10/09/2014
[24] Shivlal Mewada, Umesh Kumar Singh and Pradeep Sharma, "Security Enhancement in Cloud Computing (CC)", ISROSET-International Journal of Scientific Research in Computer Science and Engineering, Vol.-01, Issue-01, pp (31-37), Jan -Feb 2013.