Cisco Cisco IOS Software Release 12.2(27)SBC

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The Link Fragmentation and Interleaving for Frame Relay and ATM Virtual Circuits feature supports the 
transport of real-time (voice) and non-real-time (data) traffic on lower-speed Frame Relay and ATM 
permanent virtual circuits (PVCs) without causing excessive delay of real-time traffic. (This feature does 
not support switched virtual circuits.)

This feature implements link fragmentation and interleaving (LFI) using multilink PPP (MLP) over 
Frame Relay and ATM. The feature enables delay-sensitive real-time packets and non-real-time packets 
to share the same link by fragmenting the long data packets into a sequence of smaller data packets 
(fragments). The fragments are then interleaved with the real-time packets. On the receiving side of the 
link, the fragments are reassembled, and the packets are reconstructed. This method of fragmenting and 
interleaving helps guarantee the appropriate quality of service (QoS) for the real-time traffic.

Without this feature, MLP supported packet fragmentation and interleaving at the bundle layer; however, 
it did not support interleaving on Frame Relay or ATM. This feature supports low-speed Frame Relay 
and ATM as well as Frame Relay/ATM interworking (FRF.8) and Frame Relay fragmentation (FRF.12).

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12.1(5)T

This feature was introduced.

12.2(28)SB

This feature was integrated into Cisco IOS Release 12.2(28)SB.