TABLE OF CONTENTS Interface technology for seamless connection between LAN and WAN should have a healthy balance of interface features from both types of networks. In other words, it should feature the simplicity and low-cost nature of LAN interfaces as well as the high reliability of WAN interfaces. Here, the approach to technology development can be broadly divided into two types: an approach from WAN technology and an approach from LAN technology (Fig. 2). In the WAN approach, Packet over SONET (POS) 9 and WAN-PHY (where PHY denotes the physical layer in IEEE802.3) 8 technologies appropriate SDH/SONET frames to map LAN packets or frames and perform protocol conversion. Similarly, Optical Transport Network (OTN) technology 10 performs protocol conversion by mapping LAN packets or frames to a frame structure employing Forward Error Correction (FEC) frames in undersea SDH/SONET transmission systems. In contrast, ILS technology aims to provide a WAN interface with practically no protocol conversion of ultra-high-speed Ethernet signals as an approach from LAN technology. In short, the research presented here aims to achieve a simple, low-cost, and high-reliability interface with a LAN/WAN protocol-conversion section as small and as seamless as possible.
Figure 2 also shows the layer configuration in ILS together with that of competing technologies (we assume here that Layer 3 is IP in all cases). In POS, HDLC frames are used in Layer 2 and SONET frames in Layer 1, while...
