Mile (EFM), among others, address these developments. However, because of its field penetration, SONET/SDH will continue to play a key role for years to come, particularly if some of the newer technologies do not get deployed for any number of reasons. At the same time, vendors are adding features to the existing SONET platforms and, in doing so, they are bringing out next-generation SONET/SDH sys- items, which may play an important role in metro access/metro core deploy- ments until (at least) 2005. The following section indicates some of the new technologies and specifications that are applicable to the metro space. As noted, the idea of a carrier-supported LAN extension to a city level, that is, TLS service, is not such an esoteric concept as it is made out to be today. Bellcore's Switched Multimegabit Data Service (SMDS) and the IEEE 802.6 MAN standard were mid- to late-1980s carrier-grade broad- band services. The former supported up to 34 Mbps and the latter sup- ported 10 Mbps. TLS can be delivered via nonpacket architectures (such as SONET, next-generation SONET, and so on) as well as via packet architec- tures (such as GbE/VLAN, RPR, and so on). It is interesting to note that both SMDS and IEEE 802.6 services were packet based. Therefore, what- ever intrinsic advantages packet brings to the table (as the strong RPR advocacy focuses on), these advantages are already a known quantity and already tried. If packet represents a breakthrough, the said breakthrough was already commercially available since the services of the 1980s. A dis- course about the commercial success of packet-based TLS/MAN services such as VLAN, RPR, and SO on should at least make reference to the com- mercial experience accrued at that time with SMDS and 802.6. Addition- ally, you should make note of the fact that efficient bandwidth packet technologies attempt to make the most parsimonious use of a supposedly plentiful commodity: bandwidth.³0 Why be so parsimonious (at the expense of added equipment costs/expenditures) with the resour