 they leverage the same technology and have similar functionalities, MSSPs are clearly directed toward a different application with respect to MSPP. MSPP are compact machines, designed for use mainly in metro networks. Telecommunication Networks On the contrary, an MSSP is essentially a core machine, directed to carriers that are building a transport infrastructure. Due to the different application, also requirements for the two classes of machines are different. Just to make an example, the MSPPs generally have low bit rate interfaces to con- nect clients from the access network and frequently have also the possibility to incorporate Plesiochronous Digital Hierarchy (PDH) interfaces to connect to the network low bit rate legacy equipment using the PDH [27,30] that is the transmission standard that was in use before SDH/SONET. On the other hand MSSP, being oriented toward the core network, does not incorporate low bit rate interfaces, but frequently has 40 Gbit/s interfaces. This difference can be noted from Tables 7.3 and 7.4, where the features of an MSPP/ MSTP dedicated to the metro core network and of an MSSP are reported. Finally, another particularly compact type of ADM that is gaining momentum in long- haul networks is the so-called ADM on a blade. This is a small capacity, particularly compact MSPP (or even simple ADM) that is com- pletely concentrated into a single blade of a DWDM system. The use of this device is sometimes alternative to the use of the OADM, when there is the need of dropping a small part of the traffic in an intermediate location, sometimes complementary, when it is used to perform grooming and GFP adaptation of data signals before their insertions into the DWDM stream via an OADM. In this case naturally, since the switching device is a single blade, no particular platform has to be used and its accommodation inside the DWDM system implies no problems. TABLE 7.3 Summary of the Feature List of a Practical MSSP Platform Mechanic Sub-racks compatible with 19' rack; 18 unit maximum, two su