sonet sdh switches c 32 and d 34 operate in a conventional manner this illustrates the reason behind the deployment of eos to leverage the widely deployed sonet sdh infrastructure from the transport network edge sonet sdh switches b 28 and e 30 must be capable of a processing incoming data packets including performing packet buffering flow control and gfp encapsulation and b initiating controlling and terminating the vcat lcas path 36 both of these functionalities are new to sonet sdh networks additionally sonet sdh switches b 28 and e 30 must interface with control protocols such as gmpls to correlate cross connects most likely diversely routed with the vcat lcas path 36 in general gfp is a simple data packet encapsulation method used to adapt various data packet payloads into sonet sdh containers one of the most practical features of gfp is the ability to propagate client specific management information such as performance monitoring or oam data for example upon failure degradation detection on a client interface the gfp source can send a client signal fail csf message to the far end gfp destination a typical csf message includes only a payload header with the failure type sonet sdh allows bandwidth to be increased in a coarse manner if the bandwidth of a container is insufficient the next larger container can be allocated when interfacing with data traffic this method of bandwidth allocation becomes extremely inefficient for example in order to transport.