With the preemption mechanism, a ???low-priority??? frame
can be preempted by a ???high-priority??? frame, thus lowering the latency of high-priority
traffic. This mechanism is intended to minimize the delay for latency sensitive applications
such as VoIP.
With the ITU??™s VDSL2 standard being ratified in May 2005, it is likely that true
10PASS-TS implementations will never be deployed. Instead, VDSL2 leverages the
technological advances of IEEE 802.3ah and provides additional physical layer flexibility.
This ???next-generation??? 10PASS-TS, based on VDSL2 instead of VDSL, is already
a key part of video deployments for a large number of carriers and would not have been
possible without the work of IEEE 802.3ah; even though the 10PASS-TS standard is
not technically being used.
The fast and widespread technical and market adoption of IEEE 802.3 ah, as well as
the dedication to improving the technology, has cemented the IEEE 802.3ah techniques
as the best way to deliver Ethernet services over the copper loop infrastructure.
Figure 5.5 Evolution of IEEE 802.3 and ITU standards
IEEE 802.3ah 2BASE-TL (E-SHDSL) and 10PASS-TS (VDSL)
2004
Ethernet encapsulation
Ethernet multipair bonding (G.
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