 the DSL Forum's (www.dslforum. org) IP video distribution technology. In this case, video packets are given priority based on setting the DiffServ control points in the IP headers. The other solution involves proprietary vendor-defined schemes. Those pursuing an FTTN strategy are investigating new technologies that address three key areas: new technology for wire pair transmission, video com- pression, and packet video with appropriate and adequate channel-changing performance. FTTH/FTTP FTTH/FTTP takes fiber directly to the side of each home. The selected method depends on a number of demographic and financial considerations, but FTTH/ FTTP offers the greatest potential for realizing the long-term end-user service ADSL2/VDSL IP Phone 25Mbps Local Neighborhood Residential Exchange Concentrator Gateway Fiber Up to 1 Mile (1.5 km) Set-top Figure 12.6 FTTN Fiber Solutions needs. Accordingly, this is the most "future-proof" of the FTTx architectures. Basi- cally, the closer to the subscriber the fiber is, the greater the potential bandwidth and improved performance. A number of deployment scenarios are possible for FTTH/FTTP, but today one of the most popular is the use of PONs. The advantage of PONs is a lower cost per subscriber to provision the service initially. On the other hand, as Figure 12.7 indi- cates, because it is a system based on sharing wavelengths, a PON limits the band- width available, depending on the number of subscribers sharing the fiber. In addition, because it is a passive system (i.e., it makes use of nonpowered splitters to break out individual wavelengths to each subscriber), it also faces distance limi- tations. (PONs are discussed in detail in the following section.) The most common fiber implementation today is the PON, which allows multiple buildings to share one access line. A PON is basically an FTTH/FTTP arrangement in which a single optical fiber serves multiple premises (currently up to 32). It is, in essence, a point-to-multipoint configuration, which reduces the amount of fiber 