Alcatel-Lucent 1643 AMS User's Operation Manual page 394

Traffic provisioning
Differential delay
Due to the different propagation delay of the VCs a differential delay occurs between
the individual VCs. This differential delay has to be compensated and the individual
VCs have to be re-aligned for access to the contiguous payload area.
The TransLAN
Link Capacity Adjustment Scheme (LCAS)
LCAS is an extension of virtual concatenation that allows dynamic changes in the
number of channels in a connection. In case channels are added or removed by
management actions this will happen without losing any customer traffic.
LCAS allows a bandwidth service with scalable throughput in normal operation mode.
In case of failure the connection will not be dropped completely but only the affected
channel(s). The remaining channels will continue carrying traffic. LCAS provides
automatic decrease of bandwidth in case of link failure and re-establishment after link
recovery.
In case only one end supports (or has turned on) the LCAS protocol, the side that does
support LCAS adapts automatically to the restrictions that are dictated by the
non-supporting end, i.e. the entire link behaves as a link that does not support
in-service bandwidth adaptations.
Bandwidth allocation (GbE)
Unlike the TransLAN+ and M-LAN cards the GbE unit has a fully flexible internal
cross connect. This means that it is impossible to simply request bandwidth. For the
GbE card the user selects which VCs to add to the SDH Channel/VCG. In addition the
user has the option of substructuring the VC4s into VC3s thus giving additional
flexibility as in the other Ethernet cards the substructuring was fixed. The user may
select from the following SDH Rates: VC3, VC3-2v, VC4-1v, VC4-2v, VC4-3v, and
VC4-4v. This gives a range from 50 Mbps to 600 Mbps.
Dynamic bandwidth adjustment (GbE)
One of the major problems with using Virtual Concatenation is that if one of the VCs
has a fault and fails the whole signal fails. This means that if a single VC fails the
entire SDH Channel/VCG is lost. The GbE card for the 1643 AM network element
supports the Link Capacity Adjustment Scheme (LCAS). This LCAS allows dynamic
bandwidth increase or decrease without loss of signal. Furthermore, if the signal of one
or more of the components becomes degraded then LCAS will autonomously remove
those VCs from the group. When the failure is repaired LCAS will automatically return
those component VCs to the SDH Channel/VCG.
The following table indicates the effect LCAS has on the transmission capacity:
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8-42
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re-alignment process covers at least a differential delay of 32 ms.
Alcatel-Lucent - Proprietary
See notice on first page
Virtual concatenation
365-312-807R7.2
Issue 4, May 2007