-s snaplen Analyze at most the first snaplen bytes of data from each packet rather than the default of 116. 116 bytes is adequate for IPv6, ICMP, TCP, and UDP, but may truncate protocol information from name server and NFS packets (see below). Packets truncated because of a limited snaplen are indicated in the output with ``[|proto]", where proto is the name of the protocol level at which the truncation has occurred. Taking larger snapshots both increases the amount of time it takes to process packets and, effectively, decreases the amount of packet buffering. This may cause packets to be lost. You should limit snaplen to the smallest number that will capture the protocol information you're interested in.
Но я нихрена не понял.
