Configuring CoS on Link Services Interfaces
For link services IQ (lsq-) interfaces, Junos class of service (CoS) is fully supported and functions as described in the Junos OS Class of Service Configuration Guide. For more information and detailed configuration examples, see Layer 2 Service Package Capabilities and Interfaces.
On SRX Series and J Series devices, the lsq- interface is an internal interface, which is not associated with a physical interface. For information about link services on SRX Series and J Series devices, see the Junos OS Interfaces Configuration Guide for Security Devices.
For information about CoS functions and link services on M Series or T Series routers, see the following sections:
CoS for Link Services Interfaces on M Series and T Series Routers
For Link Services PIC interfaces (ls) on M Series and T Series routers, queue 0 is the only queue that you should configure to receive fragmented packets. Configure all other queues to be higher-priority queues.
Table 1 summarizes how CoS queues work on link services (ls) interfaces.
Table 1: Link Services CoS Queues
Supported Bundling Type | Queue 0 | Higher-Priority Queues |
|---|---|---|
Hash-based load balancing | No | Yes |
MLFR FRF.15 | Yes | No |
MLFR FRF.16 | Yes | No |
MLPPP | Yes | No |
For M Series and T Series routers, CoS on link services (ls) interfaces works as follows:
- On all platforms, the Link Services PIC currently supports up to four queues: 0, 1, 2, and 3.
- Queue 0 uses MLFR FRF.15, MLFR FRF.16, or MLPPP to bundle packets.
- Higher-priority queues (1, 2, and 3) use hash-based load balancing to bundle packets. IP and MPLS header information is included in the hash.
- MLPPP packets traversing link services interfaces using queue 0 are fragmented and distributed across the constituent links. Queue 0 packets are sent on the least utilized link, proportional to its bandwidth. The queue 0 load balancer attempts to maintain even distribution of all traffic across all constituent links. In situations with a small number of high-priority traffic flows (queues 1, 2, and 3), queue 0 traffic might be unevenly distributed.
- For the MLFR FRF.16 protocol, only queue 0 works. If you configure a bundled interface to use MLFR FRF.16 with queue 0, then you must ensure the classifier does not send any traffic to queues 1, 2, and 3 on that interface.
- To carry high-priority traffic correctly on MLFR FRF.16 interfaces, you must configure an output firewall filter that forces all traffic into queue 0 on the ls-fpc/pic/port.channel interface.
- MLFR FRF.15 and MLPPP interfaces support CoS through packet interleaving. The MLFR FRF.16 standard does not support packet interleaving, so all packets destined for an FRF.16 PVC interface must egress from the same queue.
- For constituent link interfaces of Link Services PICs, you can configure standard scheduler maps.
- For input packets and fragments received from constituent links, you can use regular input firewall filters and standard CoS classifiers on the link services interface.
- For packets that pass through a link services interface and are destined for a constituent link interface, all traffic using queue 0 is fragmented. Traffic using higher-priority queues (1, 2, and 3) is not fragmented.
- For MLFR FRF.15 and MLPPP, routing protocol packets smaller than 128 bytes are sent to queue 3; routing protocol packets that exceed 128 bytes are sent to queue 0 and fragmented accordingly. For MLFR FRF.16, queue 0 is used for all packet sizes.
- You must configure output firewall classification for egress traffic on the link services interface, not directly on the constituent link interface directly.
- Inverse multiplexing for ATM (IMA) is not supported on link services interfaces.
For more information, see Configuring Delay-Sensitive Packet Interleaving on Link Services Logical Interfaces and the Routing Policy Configuration Guide.
Example: Configuring CoS on Link Services Interfaces
Configure CoS on a link services interface and its constituent link interfaces.
 | Note: This example applies to M Series and T Series routers. For examples that apply to SRX Series and J Series devices, see the Junos OS Interfaces Configuration Guide for Security Devices. |
Packets that do not match the firewall filters are sent to a queue that performs load balancing by sending fragments to all constituent links.
Packets that match the firewall filters are sent to a queue that does not support packet fragmentation and reassembly; instead, this traffic is load-balanced by sending each packet flow to a different constituent link. Each packet that matches a firewall filter is subjected to a hash on the IP source address and the IP destination address to determine the packet flow to which each packet belongs.
When you configure the MLPPP encapsulation type or the multilink FRF.15 Frame Relay end-to-end encapsulation type, routing protocol packets smaller than 128 bytes are sent to the network-control queue on the constituent link interface. This keeps routing protocols operating normally, even when low-speed links are congested by regular packets.
