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Cisco 10000 Series Router Quality of Service Configuration Guide
OL-7433-09
Chapter 16 Fragmenting and Interleaving Real-Time and Nonreal-Time Packets
Multilink PPP-Based Link Fragmentation and Interleaving
Transmit Processing
The purpose of MLP over ATM-based LFI transmit processing is to fragment large nonreal-time
delay-insensitive packets and interleave smaller real-time delay-sensitive packets between the
fragments. Each MLP bundle has multiple transmit packet queues. MLP does not interleave packet
fragments from different packet queues associated with a given MLP bundle. Instead, MLP transmits all
of the fragments associated with a nonreal-time packet in order before transmitting fragments from
another nonreal-time packet. MLP posts all of the packets from the various nonreal-time packet queues
to a single bundle first-in first-out (FIFO) queue. It is from this single bundle queue that MLP does the
following:
• Fragments nonreal-time traffic
• Encapsulates the fragments with MLP
• Transmits the fragments
Real-time traffic, such as voice, are queued intact to a priority (low-latency) queue. It is from this queue
that MLP transmits the real-time packets and interleaves them between the nonreal-time fragments.
Because real-time packets are not MLP encapsulated or fragmented, MLP can safely interleave these
packets as needed. Traffic transmitted from the priority queue takes precedence over the MLP
encapsulated traffic that is transmitted from the related bundle queue.
Figure 16-4 shows an example of the packet flow of real-time and nonreal-time packets.
Figure 16-4 MLP Over ATM-Based LFI Packet Queue Flow
Receive Processing
The purpose of MLP over ATM-based LFI receive processing is to reassemble MLP over ATM
encapsulated packet fragments into PPP over ATM packets. During receive processing, the fragments
that arrive out of order and the packets with missing fragments are discarded. Valid fragments are merged
in memory until the entire packet is reassembled.
132278
Delay Insensitive
Packet Queues
Bundle FIFO
Queue
Delay Sensitive
Packet Queues
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