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Part III. Appendix 2: Data TransportImplementing the IOOSData Transport SystemIt is important to stress that much of what is being attempted here breaks new ground. Certainlythe integration of the various components into the envisioned data transport system is novel, andno matter how hard we try to envision all the issues that will arise in so doing, we are likely to findas we assemble the various components that significant new issues must be addressed to bring thesystem to the level of functionality and operation that we desire.We recommend a modular approach to the design of the system. As noted in the Introduction, amodular architecture will allow straightforward replacement of components as new technologiesrender older modules obsolete. It also will allow the overall design and implementation of the systemto be undertaken in stages by several groups working in parallel. Furthermore, we recommendthat the system be modularized along the lines presented in the Introduction, beginning with a discipline-neutrallower layer and working up from this layer. A significant advantage to making thelayers discipline neutral where possible is that it broadens the user base of support for these layers.To provide a base on which to begin building the complete transport layer, we recommend specifyingan initial configuration for several of the lower system layers. This configuration will likelychange with time, but adopting a base at this time will allow more rapid implementation of thesystem as a whole, i.e., it will allow us to undertake a suite of pilot projects built on this base thatcan move forward in parallel.In this chapter we detail the specific approach that we recommend for the design and implementationof the IOOS Data Transport System.THE DATA ACCESS PROTOCOLWe recommend adopting TCP/IP as an operational component for the IOOS Data Transport Systemat the lowest level. TCP/IP is in widespread use and is likely to remain the dominant low leveltransmission/internet protocol for the foreseeable future.The next layer up in the Data Transport System must be associated with a data access protocol. Werecommend adopting the OPeNDAP data access protocol as a pre-operational component for thedata access protocol on which the transport layer will be built. OPeNDAP is described in some detailin Annex C and in Annex B is compared to other systems of which the Data Transport Team isaware. Given the current status of OPeNDAP and the reasons outlined in the introduction to thisChapter and in Annexes B and C, we believe that selecting OPeNDAP as a pre-operational componentwill gain IOOS one to two years of advanced development on the Data Transport System.159