Some activities within UCWW, such as end-to-end (E2E) hot access network change (HAC) based on user-driven ABS&S policies, require cross-layer protocol functionality. Other examples include E2E reconfigurability (Z. Boufidis et. al., 2004, Sept), service adaptability (Houssos, N., et. al. 2003), E2E QoS support (Politis, C. al., 2004), ABC&S (O'Droma, M., Ganchev, I, et. al., 2006), user/network/service/terminal profile management, 3P-AAA and related 3P-C&B, and WBC & ADA operation. While this seems to contradict the layering architecture model for designing, planning, implementing and analysing communication protocols, nonetheless, it is the reality and it is worthwhile to structurally allow for it with suitable modifications of the reference models. Such a suitably modified reference communication model is presented in Figure 1.
It has similarities with the B-ISDN/ATM reference communication model in that it is a 3D model consisting of three planes: user plane, control plane, and management plane. The new central element, which intersects all three planes, is added to allow for structured cross-layer functionality. This cross-layer core cylinder is a modification ofthat proposed in (Ganchev, I., O'Droma, M., et. al., 2006) and may be visualized as consisting of several parallel mini cylinders each with its own dedicated functionality, e.g., corresponding to the activities already listed above with cross-layer protocol functionality. Formal reflecting of these activities and their cross-layer functionalities into this model will assist their formal design and analysis, and facilitate development of formal and open primitives and APIs.
Figure 1: The proposed cross-layer reference communication model
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