Lfi Overview; Alcatel-Lucent Specific Overview On Lfi Features; Lfi Scenario - Alcatel-Lucent OmniAccess 700 Cli Configuration Manual

Release versions: 2.2, 2.2-r02, 2.3

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Link Fragmentation and Interleaving (LFI)

Link Fragmentation and Interleaving (LFI) is a Layer 2 technique in which all the

Layer 2 frames are broken into small, equal-size fragments, and transmitted over

the link in an interleaved fashion.

Link Fragmentation and interleaving feature for MLPPP and FR supports the

transport of real-time (voice) and other (data) traffic on lower-speed PPP and FR

links without causing excessive delay to the real-time traffic. The feature enables

delay-sensitive real-time packets and packets that are not real-time data, to share

the same link by fragmenting the long data packets into a sequence of smaller

data packets (fragments). The fragments are interleaved with the real-time

packets. On the receiving side of the link, the fragments are reassembled and the

packet reconstructed. This method of fragmenting and interleaving helps

guarantee the appropriate Quality of Service (QoS) for the real-time traffic.

Consider a 1500 byte data frame that is being sent out of a 64 Kbps serial

interface. The interface, in this case, needs 187ms just to place that data frame on

the wire. If a smaller packet (for example, a voice frame) were sitting behind that

data frame, that frame might have already experienced excessive "serialization"

delay before it was ever placed on the wire. LFI mechanisms fragment larger

payloads to specified fragment sizes and then interleave the smaller payloads

among the fragments, greatly reducing the serialization delay that is experienced

by the smaller payloads.

Figure 38: LFI Scenario

The following features are available with the current release:

The OmniAccess 700 supports RFC 1990 (MLPPP) without necessarily

conforming to all the optional items mentioned in the specification.

Multilink PPP with interleaving

FRF.12 LFI is used with Frame Relay data connections.

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