Interactive traffic (Telnet, voice on IP, and the like) is susceptible to increased latency and jitter when the network processes large packets, (LAN-to-LAN FTP transfers traversing a WAN link, for example), especially as they are queued on slower links. The Cisco IOS Link Fragmentation and Interleaving (LFI) feature reduces delay and jitter on slower-speed links by breaking up large datagrams and interleaving low delay traffic packets with the resulting smaller packets;

LFI was designed especially for lower-speed links where serialization delay is significant. LFI requires that multilink PPP be configured on the interface with interleaving turned on. A related IETF Draft, called Multiclass Extensions to Multilink PPP (MCML) implements almost the same function as LFI.