Multilink Ppp-Based Link Fragmentation And Interleaving - Cisco 10000 Series Configuration Manual

Chapter 16 Fragmenting and Interleaving Real-Time and Nonreal-Time Packets
Usage Guidelines for the ppp multilink group Command
By default the ppp multilink group command is disabled, which means the link can negotiate to join
any bundle in the system.
When the ppp multilink group command is configured, the physical link is restricted from joining any
but the designated multilink group interface. If a peer at the other end of the link tries to join a different
bundle, the connection is severed. This restriction applies when MLP is negotiated between the local end
and the peer system. The link can still come up as a regular PPP interface.

Multilink PPP-Based Link Fragmentation and Interleaving

Interactive traffic such as Telnet and Voice over IP (VoIP) is susceptible to increased latency when the
network processes large packets such as LAN-to-LAN FTP transfers traversing a WAN. Packet delay is
especially significant when the FTP packets are queued on slow links within the WAN. To solve delay
problems on slow bandwidth links, the router supports link fragmentation and interleaving (LFI) based
on the Cisco implementation of Multilink PPP (MLP), which supports the fragmentation and
packet-sequencing specifications in RFC 1990.
LFI allows reserve queues to be set up so that Real-Time Transport Protocol (RTP) streams can be
mapped into a higher priority queue.
As shown in
overwhelm real-time packets such as voice. However, when fragmentation and interleaving is enabled,
bandwidth is shared equitably between nonreal-time packets and real-time packets.
Figure 16-2
Voice
MLP fragmentation allows large packets to be multilink encapsulated and fragmented into a small
enough size to satisfy the delay requirements of real-time traffic. MLP fragmentation is enabled by
default. To disable fragmentation, use the no ppp multilink fragmentation or ppp multilink fragment
disable command.
Small real-time packets are not multilink encapsulated. MLP interleaving provides a special transmit
queue (priority queue) for delay-sensitive packets to allow the packets to be sent earlier than other packet
flows. Real-time packets remain intact and are sent (interleaved) between the fragments of the larger
packets.
OL-7433-09
Figure 16-2, without fragmentation and interleaving nonreal-time data packets can
Fragmenting and Interleaving Packets
Data
Without LFI, data can
overwhelm voice
Voice Data
Multilink PPP-Based Link Fragmentation and Interleaving
Voice Data
With LFI, bandwidth
is equitably shared
to reduce voice jitter
Cisco 10000 Series Router Quality of Service Configuration Guide
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