Slicing is a function that only mirrors a specified packet length from each frame. This is useful to monitor network usage without having to copy the actual data. Slicing enables the mirroring of larger frames than the destination packet decoding equipment can handle. It also allows conservation of mirroring resources by limiting the size of the stream of packets through the router and the core network.
When a mirror slice-size is defined, a threshold that truncates a mirrored frame to a specific size is created. For example, if the value of 256 bytes is defined, up to the first 256 bytes of the frame are transmitted to the mirror destination. The original frame is not affected by the truncation. Mirrored frames will grow larger as encapsulations are added when packets are transmitted through the network core or out the mirror destination SAP to the packet/protocol decoding equipment.
The transmission of a sliced or non-sliced frame is also dependent on the mirror destination SDP path MTU and/or the mirror destination SAP physical MTU. Packets that require a larger MTU than the mirroring destination supports are discarded if the defined slice size does not truncate the packet to an acceptable size.