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Understanding MLPPP Bundles and Link Fragmentation and Interleaving (LFI) on Serial Links
Configuring the Links in a Multilink or Link Services Bundle
Example: Configuring a Link Services Interface with Two Links
Example: Configuring Link and Voice Services Interfaces with a Combination of Bundle Types
Configuring Delay-Sensitive Packet Interleaving on Link Services Logical Interfaces
Configuring Link and Multilink Services Bundles
Understanding MLPPP Bundles and Link Fragmentation and Interleaving (LFI) on Serial Links
MX240, MX480, and MX960 Universal Routing Platforms support MLPPP and MLFR multilink encapsulations. MLPPP enables you to bundle multiple PPP links into a single multilink bundle, and MLFR enables you to bundle multiple Frame Relay data-link connection identifiers (DLCIs) into a single multilink bundle. Multilink bundles provide additional bandwidth, load balancing, and redundancy by aggregating low-speed links, such as T1, E1, and serial links.
You configure multilink bundles as logical units or channels
on the link services interface lsq-0/0/0:
With MLPPP and MLFR FRF.15, multilink bundles are configured as logical units on
lsq-0/0/0—for example,lsq-0/0/0.0andlsq-0/0/0.1.With MLFR FRF.16, multilink bundles are configured as channels on
lsq-0/0/0—for example,lsq-0/0/0:0andlsq-0/0/0:1.
After creating multilink bundles, you add constituent links to the bundle. The constituent links are the low-speed physical links that are to be aggregated. Depending on the system license and hardware, you can create up to 1023 multilink bundles per Chassis, and on each multilink bundle add up to 8 constituent links. See Multilink and Link Services PICs Overview for more information.
The following rules apply when you add constituent links to a multilink bundle:
On each multilink bundle, add only interfaces of the same type. For example, you can add either T1 or E1, but not both.
Only interfaces with a PPP encapsulation can be added to an MLPPP bundle, and only interfaces with a Frame Relay encapsulation can be added to an MLFR bundle.
If an interface is a member of an existing bundle and you add it to a new bundle, the interface is automatically deleted from the existing bundle and added to the new bundle.
Configuring a multilink bundle on the two serial links increases the bandwidth by 70 percent from approximately 1 Mbps to 1.7 Mbps and prepends each packet with a multilink header as specified in the FRF.12 standard. To increase the bandwidth further, you can add up to eight serial links to the bundle. In addition to a higher bandwidth, configuring the multilink bundle provides load balancing and redundancy. If one of the serial links fails, traffic continues to be transmitted on the other links without any interruption. In contrast, independent links require routing policies for load balancing and redundancy. Independent links also require IP addresses for each link as opposed to one IP address for the bundle. In the routing table, the multilink bundle is represented as a single interface.
Starting
with Junos OS Release 13.3, if you attempt to delete or deactivate
a static inline service (si) MLPPP bundle interface that
is still referenced by a member link interface, which could be PPPoE
(pp0) or si logical interfaces, and commit the
configuration, the commit operation fails. You must reactivate such
MLPPP bundle interface before committing the settings. Alternatively,
you must ensure that member links do not refer a static MLPPP bundle
before you delete or deactivate the bundle. This method of deactivation
and reactivation of an MLPPP bundle is not applicable for interfaces
other than si- interfaces, such as link services IQ (lsq-) and virtual LSQ redundancy (rlsq-) interfaces.
See Also
Configuring the Number of Bundles on Link Services PICs
You can combine MLFR FRF.16, MLPPP, and MLFR FRF.15 bundles on a single Link Services PIC. For a sample configuration, see Example: Configuring a Link Services Interface with Two Links.
To configure the number of bundles on a Link Services PIC, include
the mlfr-uni-nni-bundles statement at the [edit chassis
fpc slot-number pic pic-number] hierarchy level:
mlfr-uni-nni-bundles number;
Each Link Services PIC can accommodate a maximum of 256 MLFR UNI NNI bundles. For more information, see the Junos OS Administration Library for Routing Devices.
A link can associate with one link services bundle only. All Link Services PICs support up to 256 single-link bundles and up to 256 DLCIs. For an example configuration, see the configuration examples.
When one or more links in a bundle are put in loopback, reassembly buffering and hence processing are reduced so as to not affect other bundles. This prevents packet loss on other bundles, while reducing the reassembly buffers available for the bundle with looped links.
See Also
Configuring the Links in a Multilink or Link Services Bundle
To complete a multilink or link services interface configuration, you need to configure both the physical interface and the multilink or link services bundle. For multilink interfaces, you configure the link bundle on the logical unit. For link services interfaces, you configure the link bundle as a channel (see Figure 1). The physical interface is usually connected to networks capable of supporting MLPPP or MLFR (FRF.15 or FRF.16).
The following sample configuration refers to the topology in Figure 1 and configures a multilink or link services bundle over a T1 connection (for which the T1 physical interface is already configured).
To configure a physical T1 link for MLPPP, include the following statements at the
[edit interfaces t1-fpc/pic/port]hierarchy level:unit 0 { family mlppp { bundle (ml-fpc/pic/port | ls-fpc/pic/port); } }You do not need to configure an IP address on this link.
To configure a physical T1 link for MLFR FRF.16, include the following statements at the
[edit interfaces t1-fpc/pic/port]hierarchy level:encapsulation multilink-frame-relay-uni-nni; unit 0 { family mlfr-uni-nni { bundle ls-fpc/pic/port:channel; } }You do not need to configure an IP address or a DLCI on this link.
To configure the logical address for the MLPPP, MLFR FRF.15, or MLFR FRF.16 bundle, include the
addressanddestinationstatements:address address { destination address; }You can include these statements at the following hierarchy levels:
[edit interfaces interface-name unit logical-unit-number family inet][edit logical-systems logical-system-name interfaces interface-name unit logical-unit-number family inet]
When you add statements such as
mrruto the configuration and commit, the T1 interface becomes part of the multilink bundle.
For MLPPP and MLFR (FRF.15 and FRF.16) links, you must
specify the subnet address as /32 or /30. Any
other subnet designation is treated as a mismatch.
See Also
Example: Configuring a Link Services Interface with Two Links
This example uses the MLFR UNI NNI protocol between Router A
and Router B and logically connects link services bundles ls-1/1/0.3 and ls-0/0/0.10, as specified in Table 1.
Router A |
Router B |
|---|---|
|
|
|
|
For LMI to work properly, you must configure one router to be a DCE.
Configuration on Router A
[edit interfaces]
ls-1/1/0:3 {
dce;
encapsulation multilink-frame-relay-uni-nni;
unit 0 {
dlci 16;
family inet {
address 10.3.3.1/32 {
destination 10.3.3.2;
}
}
}
}
t1-0/1/0 {
encapsulation multilink-frame-relay-uni-nni;
unit 0 {
family mlfr-uni-nni {
bundle ls-1/1/0:3;
}
}
}
t1-0/1/1 {
encapsulation multilink-frame-relay-uni-nni;
unit 0 {
family mlfr-uni-nni {
bundle ls-1/1/0:3;
}
}
}
Configuration on Router B
[edit interfaces]
ls-0/0/0:10 {
encapsulation multilink-frame-relay-uni-nni;
unit 0 {
dlci 16;
family inet {
address 10.3.3.2/32 {
destination 10.3.3.1;
}
}
}
}
t1-0/3/0 {
encapsulation multilink-frame-relay-uni-nni;
unit 0 {
family mlfr-uni-nni {
bundle ls-0/0/0:10;
}
}
}
t1-0/3/1 {
encapsulation multilink-frame-relay-uni-nni;
unit 0 {
family mlfr-uni-nni {
bundle ls-0/0/0:10;
}
}
}
See Also
Example: Configuring Link and Voice Services Interfaces with a Combination of Bundle Types
[edit chassis]
fpc 1 {
pic 3 {
mlfr-uni-nni-bundles 4;
}
}
[edit interfaces]
t1-0/2/0:0 {
encapsulation multilink-frame-relay-uni-nni;
unit 0 {
family mlfr-uni-nni {
bundle ls-1/3/0:0;
}
}
}
t1-0/2/0:1 {
encapsulation multilink-frame-relay-uni-nni;
unit 0 {
family mlfr-uni-nni {
bundle ls-1/3/0:0;
}
}
}
t1-0/2/0:5 {
unit 0 {
family mlppp {
bundle ls-1/3/0.2;
}
}
}
t1-0/2/0:6 {
unit 0 {
family mlppp {
bundle ls-1/3/0.2;
}
}
}
t1-0/2/0:7 {
encapsulation frame-relay;
unit 0 {
dlci 20;
family mlfr-end-to-end {
bundle ls-1/3/0.1;
}
}
}
t1-0/2/0:8 {
encapsulation frame-relay;
unit 0 {
dlci 20;
family mlfr-end-to-end {
bundle ls-1/3/0.1;
}
}
}
t1-0/2/0:10 {
no-keepalives;
encapsulation ppp;
unit 0 {
family mlppp {
bundle lsq-1/1/0.0;
}
}
}
t3-1/0/0 {
no-keepalives;
encapsulation ppp;
unit 0 {
family mlppp {
bundle lsq-1/1/0.2;
}
}
}
lsq-1/1/0 {
unit 0 {
encapsulation multilink-ppp;
compression {
rtp {
f-max-period 100;
queues [ q1 q2 ];
port minimum 2000 maximum 6000;
}
}
family inet {
address 10.5.5.5/24;
}
}
unit 1 {
encapsulation multilink-ppp;
compression {
rtp {
port minimum 2000 maximum 6000;
}
}
family inet {
address 10.6.6.1/24;
}
}
unit 2 {
encapsulation multilink-ppp;
compression {
rtp {
port minimum 2000 maximum 6000;
}
}
family inet {
address 10.9.9.1/24;
}
}
}
t1-1/2/0 {
no-keepalives;
unit 0 {
family mlppp {
bundle lsq-1/1/0.1;
}
}
}
ls-1/3/0 {
unit 1 {
encapsulation multilink-frame-relay-end-to-end;
family inet {
address 10.1.4.1/24;
}
}
unit 2 {
encapsulation multilink-ppp;
family inet {
address 10.7.4.1/24;
}
}
}
ls-1/3/0:0 {
encapsulation multilink-frame-relay-uni-nni;
mlfr-uni-nni-bundle-options {
debug-flags 15;
}
unit 0 {
dlci 20;
family inet {
address 10.5.4.1/24;
}
}
}
[edit routing-options]
static {
route 10.12.12.0/24 next-hop 10.1.1.9;
}
On Router B:
[edit chassis]
fpc 1 {
pic 3 {
mlfr-uni-nni-bundles 4;
}
}
[edit interfaces]
ge-0/0/0 {
unit 0 {
family inet {
address 10.1.1.1/24;
}
}
}
so-0/1/1 {
encapsulation ppp;
unit 0 {
family inet {
address 10.7.7.7/24;
}
}
}
t1-0/2/0:0 {
encapsulation multilink-frame-relay-uni-nni;
unit 0 {
family mlfr-uni-nni {
bundle ls-1/3/0:0;
}
}
}
t1-0/2/0:1 {
encapsulation multilink-frame-relay-uni-nni;
unit 0 {
family mlfr-uni-nni {
bundle ls-1/3/0:0;
}
}
}
t1-0/2/0:5 {
no-keepalives;
unit 0 {
family mlppp {
bundle ls-1/3/0.2;
}
}
}
t1-0/2/0:6 {
no-keepalives;
unit 0 {
family mlppp {
bundle ls-1/3/0.2;
}
}
}
t1-0/2/0:7 {
dce;
encapsulation frame-relay;
unit 0 {
dlci 20;
family mlfr-end-to-end {
bundle ls-1/3/0.1;
}
}
}
t1-0/2/0:8 {
dce;
encapsulation frame-relay;
unit 0 {
dlci 20;
family mlfr-end-to-end {
bundle ls-1/3/0.1;
}
}
}
t1-0/2/0:10 {
no-keepalives;
encapsulation ppp;
unit 0 {
family mlppp {
bundle lsq-1/1/0.0;
}
}
}
t3-0/3/0 {
no-keepalives;
encapsulation ppp;
unit 0 {
family mlppp {
bundle lsq-1/1/0.2;
}
}
}
ge-1/0/0 {
unit 0 {
family inet {
address 10.2.2.1/24;
}
}
}
lsq-1/1/0 {
unit 0 {
compression {
rtp {
port minimum 2000 maximum 6000;
}
}
family inet {
address 10.5.5.1/24;
}
}
unit 1 {
encapsulation multilink-ppp;
compression {
rtp {
port minimum 16384 maximum 20102;
}
}
family inet {
address 10.3.4.1/24;
}
}
unit 2 {
encapsulation multilink-ppp;
compression {
rtp {
port minimum 2000 maximum 6000;
}
}
family inet {
address 10.9.9.9/24;
}
}
}
t1-1/2/2 {
no-keepalives;
unit 0 {
family mlppp {
bundle ls-1/3/0.1;
}
}
}
t1-1/2/3 {
no-keepalives;
unit 0 {
family mlppp {
bundle lsq-1/1/0.1;
}
}
}
ls-1/3/0 {
unit 1 {
encapsulation multilink-frame-relay-end-to-end;
family inet {
address 10.1.4.4/24;
}
family iso;
}
unit 2 {
encapsulation multilink-ppp;
family inet {
address 10.7.4.4/24;
}
}
}
ls-1/3/0:0 {
dce;
encapsulation multilink-frame-relay-uni-nni;
unit 0 {
dlci 20;
family inet {
address 10.5.4.4/24;
}
}
}
[edit routing-options]
static {
route 10.12.12.0/24 next-hop 10.3.4.4;
}
See Also
Enabling MLPPP Link Fragmentation and Interleaving
MLPPP enables you to bundle multiple PPP links into a single multilink bundle. MLPPP bundle support on an inline LSQ interface is identical to a non-inline LSQ interface, because the configuration to enable fragmentation, link fragmentation and interleaving (LFI), and timeout is identical.
Priority scheduling on a multilink bundle determines the order in which an output interface transmits traffic from an output queue. The queues are serviced in a weighted round-robin fashion. But when a queue containing large packets starts using the multilink bundle, small and delay-sensitive packets must wait their turn for transmission. Because of this delay, some slow links, such as T1 and E1, can become useless for delay-sensitive traffic.
Link fragmentation and interleaving (LFI) solves this problem. It reduces delay and jitter on links by fragmenting large packets and interleaving delay-sensitive packets with the resulting smaller packets for simultaneous transmission across multiple links of a multilink bundle.
To configure schedule maps and fragmentation maps for MLPPP LFI:
The following partial configuration shows when the fragment threshold for low priority queues inherits from the fragment threshold configured in the bundle IFL and will have the value of 640.
[edit class-of-service]
forwarding-classes {
queue 0 be;
queue 1 ef;
queue 2 af;
queue 3 nc;
}
fragmentation-maps {
fragmap-3 {
forwarding-class ef {
no-fragmentation;
}
}
}
schedulers {
af-scheduler {
transmit-rate percent 30;
priority low;
}
be-scheduler {
transmit-rate percent 20;
priority low;
}
ef-scheduler {
transmit-rate percent 35 rate-limit;
priority strict-high;
}
nc-scheduler {
transmit-rate percent 15;
priority high;
}
}
....
See Also
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.
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.
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:
interleave-fragments;
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 User Guide for Routing Devices.
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.
[edit interfaces]
ls-1/0/0 {
unit 1 {
encapsulation multilink-frame-relay-end-to-end;
interleave-fragments;
family inet {
address 192.168.5.2/32 {
destination 192.168.5.3;
}
}
}
t3-1/0/0:1 {
per-unit-scheduler;
unit 0 {
dlci 16;
encapsulation multilink-frame-relay-end-to-end;
family mlfr-end-to-end {
bundle ls-1/0/0.1;
}
}
}
[edit class-of-service]
interfaces {
t3-1/0/0:1 {
unit 0 {
scheduler-map sched-map-logical-0;
shaping-rate 10m;
}
unit 1 {
scheduler-map sched-map-logical-1;
shaping-rate 20m;
}
}
}
scheduler-maps {
sched-map-logical-0 {
forwarding-class best-effort scheduler sched-best-effort-0;
forwarding-class assured-forwarding scheduler sched-bronze-0;
forwarding-class expedited-forwarding scheduler sched-silver-0;
forwarding-class network-control scheduler sched-gold-0;
}
sched-map-logical-1 {
forwarding-class best-effort scheduler sched-best-effort-1;
forwarding-class assured-forwarding scheduler sched-bronze-1;
forwarding-class expedited-forwarding scheduler sched-silver-1;
forwarding-class network-control scheduler sched-gold-1;
}
schedulers {
sched-best-effort-0 {
transmit-rate 4m;
}
sched-bronze-0 {
transmit-rate 3m;
}
sched-silver-0 {
transmit-rate 2m;
}
sched-gold-0 {
transmit-rate 1m;
}
sched-best-effort-1 {
transmit-rate 8m;
}
sched-bronze-1 {
transmit-rate 6m;
}
sched-silver-1 {
transmit-rate 4m;
}
sched-gold-1 {
transmit-rate 2m;
}
}
}
}