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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
Multi-VC MLP Over ATM-Based LFI
Multi-VC MLP over ATM-based LFI uses the fragmentation and interleaving capability of MLP to
integrate real-time and nonreal-time packets together on the same link. MLP defines the mechanisms to
fragment, reassemble, and sequence large datagrams across multiple logical data links. MLP uses the
fragmentation and packet sequencing specifications defined in RFC 1990 to implement link
fragmentation and interleaving at the bundle level. Multi-VC MLP over ATM-based LFI supports up to
10 member links per MLP bundle, one of which is LFI-enabled.
MLP encapsulates real-time packets as PPP over ATM (PPPoA) and sends the packets to a priority
transmit queue to enable the router to transmit the real-time packets earlier than other packet flows. The
router interleaves the real-time packets between the fragments of the larger, nonreal-time packet over a
single point-to-point link to the remote address. Upon receipt, the receiving fragmentation peer
processes the real-time packets as PPPoA packets.
MLP fragments the large data packets to a size small enough to satisfy the delay requirements of
real-time traffic. MLP encapsulates the packets as MLP packets and sends the packets to a first-in
first-out (FIFO) queue to enable the router to transmit the fragments at the same time over multiple
point-to-point links to the same remote address. Upon receipt, the receiving fragmentation peer
reassembles the fragments to the original packet and then processes it as PPPoA. The underlying PPP
encapsulation conforms to RFC 1661.
MLP fragments all outbound MLP packets with a payload that is larger than the specified fragment size.
The smallest fragment size depends on the AAL5 encapsulation type and whether or not protocol
compression is enabled. For more information, see the
“Fragment Size Calculation for MLP Over
ATM-Based LFI” section on page 16-15
.
When configuring Multi-VC MLP over ATM-based LFI, you must configure a virtual template interface
for the MLP bundle. However, the virtual template does not need to be unique for each bundle—multiple
MLP bundles can share the same virtual template.
Feature History for Multi-VC MLP Over ATM-Based LFI
Fragment Size Calculation for Multi-VC MLP Over ATM-Based LFI
For Multi-VC MLP over ATM-based LFI, the ideal fragment size should allow the fragments to fit into
an exact multiple of ATM cells.
Table 16-2 on page 16-15
lists the minimum fragment sizes for
Single-VC and Multi-VC MLP over ATM-based LFI. As shown in the table, the minimum fragment size
depends on the AAL5 encapsulation type used and whether or not protocol compression is enabled.
For more information, see the
“Fragment Size Calculation for MLP Over ATM-Based LFI” section on
page 16-15
.
Cisco IOS Release
Description
Required PRE
Release 12.2(27)SBB
The Multi-VC MLP over ATM-based LFI feature was
introduced on the router for the PRE2.
PRE2
Release 12.2(31)SB2
This feature was introduced on the PRE3 and the valid
multilink interface values changed from 1 to 9999
(Release 12.2(28)SB and later) to from 1 to 9999 and
65,536 to 2,147,483,647.
PRE3