Configuring Delay-Sensitive Packet Interleaving on Link Services Logical Interfaces
For link services FRF.15 and MLPPP interfaces only, you can configure link fragment interleaving (LFI). LFI reduces excessive delays of Frame Relay packets by fragmenting long packets into smaller packets and interleaving them with real-time frames. This allows real-time and non-real-time data frames to be carried together on lower-speed links without causing excessive delays to the real-time traffic. When the peer interface receives the smaller fragments, it reassembles the fragments into their original packet. For example, short delay-sensitive packets, such as packetized voice, can race ahead of larger delay-insensitive packets, such as common data packets.
 | Note: All Link Services PICs (4-multilink bundle, 32-multilink bundle, and 128-multilink bundle) support up to 256 link services interfaces with LFI enabled, if those link services interfaces contain only one constituent link each. For the Link Services PIC, multiple-link LFI bundles are simply multilink bundles, and are limited based on the type of PIC (4-multilink bundle, 32-multilink bundle, and 128-multilink bundle). In addition, the multilink bundles you configure subtract from the total of 256 possible LFI-enabled link services interfaces. For example, if a 32-multilink bundle Link Services PIC has 24 multilink bundles configured and active, then you can configure 256 – 24 = 232 LFI-enabled link services interfaces, each with a single constituent link. For link services IQ interfaces (lsq), the interleave-fragments statement is not valid. Instead, you can enable LFI by configuring fragmentation maps. For more information, see Configuring CoS Fragmentation by Forwarding Class on LSQ Interfaces. |
You can configure multiple links in a bundle and configure packet interleaving. However, if you use packet interleaving, high-priority, nonmultilink-encapsulated packets use a hash-based algorithm to choose a single link.
For detailed information about link services CoS, see Configuring CoS on Link Services Interfaces.
Per-bundle CoS queuing is supported on link services IQ interfaces (lsq). For more information about link services IQ interfaces, see Layer 2 Service Package Capabilities and Interfaces.
The Junos OS supports end-to-end fragmentation in compliance with the FRF.12 Frame Relay Fragmentation Implementation Agreement standard. Unlike user-to-network interface (UNI) and network-to-network (NNI) fragmentation, end-to-end supports fragmentation only at the endpoints.
By default, packet interleaving is disabled. To enable packet interleaving, include the interleave-fragments statement:
You can include this statement at the following hierarchy levels:
- [edit interfaces interface-name unit logical-unit-number]
- [edit logical-systems logical-system-name interfaces interface-name unit logical-unit-number]
Configuring LFI with DLCI Scheduling
For Link Services and Channelized DS3 IQ PICs, you can configure LFI and DLCI scheduling. For channelized DS3 interfaces, LFI is supported with FRF.15 only, and on M10i and M20 platforms only.
Configuring LFI with DLCI scheduling enables packets entering the Link Services PIC to be fragmented before being transmitted to the Channelized DS3 IQ PIC. Once the fragmented packets enter the Channelized DS3 IQ PIC, they are scheduled at the DLCI level, to allow priority transmission for real-time applications.
For more information about associating a scheduler with a DLCI, see the Junos OS Class of Service Configuration Guide.
Example: Configuring LFI with DLCI Scheduling
Configure packets entering the Link Services PIC to be fragmented before being transmitted to the Channelized DS3 IQ PIC. Once the fragmented packets enter the Channelized DS3 IQ PIC, they are scheduled at the DLCI level, to allow priority transmission for real-time applications.
