FrameSize is a read-only Gauge32, expressed in bytes, giving the average frame size across both transmitted and received traffic for this IP-to-IP conversation. A shrinking average frame size for a IP-to-IP conversation can indicate a shift toward small control or VoIP-style packets, while a size hovering near the link's MTU suggests bulk data transfer, and — since this ipsb table duplicates the row layout of the MIB's iplb table but is sampled and indexed independently — a given pair can show different collection intervals in ipsb than it does in iplb. Watching this gauge for the pair 10.4.12.30/198.51.100.7 settle around, say, 1200 bytes versus dropping to under 100 bytes tells an admin whether that traffic looks like file transfer or short signalling exchanges.