t Interface 3 (SPI-3) interface, which are carried on the same set of pins. Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. SYSTEMS ENGINEERING ISSUES SYSTEMS ENGINEERING ISSUES The 10 GbE card represents a challenge for our designer, but not an insurmountable problem. This is because in addition to the 10 Gigabit Ethernet NPU, Agere also provides their own in-house Synchronous Optical Network (SONET) framer. However, they do not provide the data engine, SO hybrid solution must be found. Our designer does not need to tackle frame relay now, but he or she can think about solutions offered by an alternative source because Agere currently does not have high-density High-level Data Link Control (HDLC) framer and therefore cannot propose such a line card. This vendor could be someone like PMC-Sierra. Cards then need to be found or designed. The first point to check is obviously the fabric and NPU vendor. Agere proposes multiple cards that could be used for this purpose but not all of them. The issues can be summarized as follows. The designer notices that the network-processor aspects of the OC-48c card and the 4X1.2 GbE card are essentially identical; therefore, only the PHY/framer aspects of these cards will be different. The designer notices that the OC-48 cards and the 4X1.25GbE cards are essentially identical as they are implemented around Agere's APP5xx chip; therefore, only the framer/PHY cards corre- sponding to these different interfaces will be different. The key component of the OC-48 ATM/POS framer/PHY card is Agere's TADM. Several versions are available of the TADM (the current one is the TADM042G5) and its sister-part the TDAT, which can handle the transmission convergence and SONET/Synchronous Digital Hierarchy (SDH) terminal/add/drop multiplexing (ADM) functionality in ring, linear, and mesh networks. The TADM can handle 155/622/2