How do you compare LCAS with other methods of bandwidth allocation in SDH networks?

1 What is LCAS?

LCAS is a protocol that allows dynamic adjustment of the bandwidth of a virtual concatenation (VC) group in SDH networks. A VC group is a set of contiguous or non-contiguous channels that are logically combined to form a larger bandwidth. LCAS enables the addition or removal of channels from a VC group without interrupting the service or affecting the quality of the signal. LCAS also provides protection and restoration mechanisms in case of failures or errors in the network.

2 How does LCAS work?

LCAS uses a control word that is inserted in the overhead bytes of each channel in the VC group. The control word contains information about the status, sequence, and membership of the channel. The sender and the receiver of the VC group exchange these control words to coordinate the bandwidth adjustment process. The sender can initiate the adjustment by sending a request to the receiver, indicating the desired number of channels in the VC group. The receiver can accept or reject the request, depending on its capabilities and availability. The sender can then activate or deactivate the channels accordingly, and the receiver can acknowledge the completion of the adjustment.

3 What are the benefits of LCAS?

LCAS offers several advantages for bandwidth allocation in SDH networks, such as flexibility, efficiency, resilience, and compatibility. It allows the adaptation of the bandwidth of a VC group to changing traffic demands or network conditions without disrupting existing services or requiring manual intervention. LCAS also enables optimal utilization of network resources by avoiding under- or over-provisioning and minimizing the waste of unused channels. Additionally, it provides fast and automatic recovery from failures or errors in the network by switching to alternative channels or restoring the original channels in the VC group. Moreover, it is compatible with existing SDH equipment and standards, and does not require any modification or upgrade of the network infrastructure.

4 What are the limitations of LCAS?

LCAS has some limitations for bandwidth allocation in SDH networks, such as complexity due to the exchange and interpretation of control words between sender and receiver of the VC group, granularity as it can only adjust bandwidth by adding or removing channels, and availability as it depends on the network topology, configuration, and traffic. These limitations mean LCAS cannot provide fine-grained or fractional bandwidth allocation nor guarantee requested bandwidth in all situations.

5 How to compare LCAS with other methods?

LCAS is not the only method of bandwidth allocation in SDH networks; there are other methods with different characteristics, advantages, and disadvantages. Static bandwidth allocation is the simplest and most common method, where the bandwidth of a VC group is predefined and fixed at the time of provisioning. Dynamic bandwidth allocation is a more advanced and adaptive method, where the bandwidth of a VC group is dynamically adjusted according to the traffic demands or network conditions. Hybrid bandwidth allocation is a combination of static and dynamic methods, where some channels in a VC group are fixed and some are adjustable. To compare LCAS with other methods of bandwidth allocation, you should consider factors such as the type of traffic or service you want to transmit over the network, its available and compatible channels and equipment, performance objectives like reliability and throughput, as well as cost and complexity implications like capital expenditure and maintenance.