Configuring Ppp Link Efficiency Mechanisms; Introduction To Ppp Link Efficiency Mechanisms - H3C SR6600 Configuration Manual

Configuring PPP Link Efficiency Mechanisms

Introduction to PPP Link Efficiency Mechanisms

This mechanism is available for improving transmission efficiency on PPP links: Link Fragmentation
and Interleaving (LFI).
Link fragmentation and interleaving
On a low speed serial link, packets of real-time interactive communications (such as Telnet and VoIP)
may be blocked or delayed if packets of other applications are also transmitted across the link. For
example, if a voice packet arrives when large packets are being scheduled and waiting for being
transmitted, it has to wait until all the large packets have been transmitted. For the real-time applications
such as VoIP, delays longer than 100 or 150 ms cause voice quality to drop dramatically and thus
cannot be tolerated.
On a 56 Kbps link, it costs approximately 215 ms to transmit a 1500-byte packet (the size of the MTU of
common links). To confine the delay of transmitting time-sensitive packets on low-speed links (such as
56 Kbps frame relay channels or 64 Kbps ISDN B channels) to an acceptable level, a method is
required to fragment larger packets and adding both the smaller packets and fragments of the large
packet to an output queue.
LFI reduces delays and jitters on low-speed links by fragmenting large packets into small fragments and
transmitting them along with small packets. The fragmented datagrams are reassembled at the
destination.
The following figure illustrates the process of LFI. When large packets and small voice packets arrive at
a WFQ-enabled interface at the same time, the large packets are fragmented into small fragments,
which are then added to the queues along with the voice packets.
Figure 2-4 Link fragmentation and interleaving
Configuring PPP Link Efficiency Mechanisms
Follow these steps to configure PPP Link efficiency mechanisms:
Enter system view
Create an MP-group
To do... Use the command...
system-view
interface mp-group
mp-number
2-43
Remarks
—
Required